Project M2 DIY Thread

[srm51555]

Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen.

Schematic of the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=382327&viewfull=1#post382327) - Note: C2 in the schematic shows a value of 33.3uf, this is a typo. the correct value is 3.3uf

DSP File (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=362894&viewfull=1#post362894)

Inside the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=375530&viewfull=1#post375530)

Outside the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=374872&viewfull=1#post374872)

M2 Dimensions (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=374875&viewfull=1#post374875)

Horn Mounting (http://www.audioheritage.org/vbulletin/showthread.php?36789-Compact-monitor&p=374486&viewfull=1#post374486)

Horn Mounting pt2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=380622&viewfull=1#post380622)

[srm51555]

Here is the photo progression of my project. Cabinets were glued with Titebond 2 and Spax MFD specific screws.

I originally started out with using 1"x2" strips of particle board for bracing. After some recommendation I moved over to using Baltic Birch to achieve a better brace matrix. The particle boards were glued and screwed so they stayed in. With the extra volume they took up I was unable to brace exactly like the M2 in the top and bottom sections.
68608

68609

Next came the primer to seal the inside. It's a 2 part epoxy primer and I sprayed 2-3 coats of it on. I taped certain sections of the cabinet and bracing I could properly glue and screw baffle on.

68610

Next came the dampening material. I was unable to locate the Owens Corning stuff POS recommended locally. I then was recommended two other options. Wrap on 16550 Bulk Roll Fiberglass (http://www.morelectricheating.com/default.aspx?page=item+detail&itemcode=WRAPON16550&catlist=1222&parent=2693) or get the regular pink stuff from Home Depot and make it 1". My original plan was to use the Wrap on stuff but I realized I already had a roll of the pink stuff and figured I'd better use it since I've been storing it for this occasion.

68611

I left the horn cutout process till after the baffle was installed because I wanted to be sure the horn was in the correct place.

68612

[srm51555]

Current state, I still need to drill holes for the woofer and horn. Also I was original going to paint to standard black. Since then I've run the thought of painting it some other color, any thoughts. These will be in a dedicated room so WAF is not a problem.

68613

[JeffW]

I think you'll want that fiberglass to be lining all the interior surfaces except the back of the baffle - especially behind the woofer.

[srm51555]

That is the plan. I left it out because I was going to send it to paint. Since then it's gotten to dang cold to properly prep so I will most likely put it in so I can finally hear them and be left with an unfinished cabinet for the winter.

[pos]

Schematic of the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=382327&viewfull=1#post382327)
As you know the schematic in this doc has a typo: C2 should read 3.3uF instead of 33.3uF.
If you could edit your first post to make this clear that would probably be helpful.

Here is the correct schematic, in appendix 3: https://docs.google.com/document/d/1bzJyui75ZG_-wjV95dqKSbFs1Xh87bk2qlc-qS7Kk_Y/edit?usp=sharing#heading=h.267sxg2itu1h

[srm51555]

As you know the schematic in this doc has a typo: C2 should read 3.3uF instead of 33.3uF.
If you could edit your first post to make this clear that would probably be helpful.

Here is the correct schematic, in appendix 3: https://docs.google.com/document/d/1bzJyui75ZG_-wjV95dqKSbFs1Xh87bk2qlc-qS7Kk_Y/edit?usp=sharing#heading=h.267sxg2itu1h

Very good, post is updated. I was waiting for confirmation before I call Parts Express and try to return these out of the 45 day policy.

[cooky1257]

Current state, I still need to drill holes for the woofer and horn. Also I was original going to paint to standard black. Since then I've run the thought of painting it some other color, any thoughts. These will be in a dedicated room so WAF is not a problem.

68613
If you plan to use 'standard' fibreglass you may want to generously spray it with hairspray to fix those pesky fibres.

[srm51555]

Thanks for the tip. Who knows, I may rip this stuff out and replace it with the wrap-on stuff, it's all pending on how sealed I can get the cabinet when painting it.

[Lee in Montreal]

I suggest you router all corners with a straight bit, to make them flush. It will take 5 minutes per cabinet and they will look even better. ;-)

[srm51555]

My straight bit got plenty of use with this project. I usually set the internal cabinet depth with the bracing and shave the excess off like you recommended. It really does turn a ok cabinet into a great one. I also used it on the bracing and horn hole. After making a jig of the part I needed to make a few of all I did was rough cut with a jig saw then cleaned up with it.

[Alobar]

Nice work! Should be a good thread... ! I really enjoy watching the progress on these DIY cab build projects. Makes me want to try building a speaker pair myself someday. It also shows how much goes into these projects than simply building a box or something like a kitchen cabinet. Looking forward to seeing the final result!

[srm51555]

Nice work! Should be a good thread... ! I really enjoy watching the progress on these DIY cab build projects.

Thanks. I think we all like watching the progress of members speaker or systems, at least I do. Photo's are so much easier with camera phones.

[Fitero]

I've been following the thread with great interest, as I too would like to start building myself a pair of M2 clones.
Other than the dour black exterior, I want to copy the original as closely as possible

I did some calculations of the cabinet dimensions and came up with the following;

Volume = 147.42 Litres
Bracing Volume = +/- 7.5 Litre
Overall Volume = 140 Litres

I am most puzzled by the port dimensions. The parameters provided by 4313b (JBL M2 System Simulation) and Valentin are what I have been comparing.

Judging from the pictures, the ports flare to +/- 4" from a minimum inner diameter of approximately 44.5mm to 46.5mm. (+/- 1.75")

I don't know squat about such things, and am unaware if JBL contemplates the Bernoulli Principle while calculating Ports. It sure appears this way to me.

Am I missing something here?

[SMT]

Marketing Propaganda fwiw:

M2 ENCLOSURE
Small Footprint, Extended Bass Performance, Patented Low Frequency Port Design

Extended low frequency performance and high SPL can be the formula for unwanted resonance. The M2 enclosure is constructed of rigid 1" MDF and with the aid of JBL’s interferometer, extensively braced for rock-solid stability at the system’s full rated power. The enclosure incorporates a JBL patented Slipstream port design with internal flares that ensure low frequency efficiency while eliminating noise caused by port turbulence. Architecturally elegant, the M2 enclosure occupies a relatively small footprint, and can be transported to various working environments.

http://www.jblpro.com/www/jbl-story/innovation/technology/directivity/slip-stream-port#.Vmixz7-TVx4

[SMT]

Sadly, this is the most technical info. I was able to dig up. I was not able to find the pending patent docs...

https://www.youtube.com/watch?v=sIc2ORiDxrE

[Fitero]

Thanks for the responses.

Since this is a proprietary design for JBL, they won't sell the ports either. No matter, it is still a venturi, and can be easily copied by enterprising DIY people.

All we need is for someone to take a snap-gauge and caliper and measure the smallest part of the port, and the o.d. of the inner port bell and we can do the rest.
Valentin has already kindly measured the length, which more or less coincide to the data on the M2 tech sheet provided by 4313b.

[grumpy]

Or buy whatever flared ports you like and tune to length appropriately:)

[Hoerninger]

Method for predicting
Loudspeaker port performance and
optimizing loudspeaker port
designs utilizing bi-directional
fluid flow principles


AES_PortPaper:
http://koti.kapsi.fi/jahonen/Audio/Papers/AES_PortPaper.pdf
___________
Peter

[1audiohack]

Well the M2 HF protection network comes with a small surprise.

ATTACH]68669[/ATTACH]

The cap values are 3.3µF and 4.7µF.

[4313B]

Well the M2 HF protection network comes with a small surprise.

ATTACH]68669[/ATTACH]

The cap values are 3.3µF and 4.7µF.That's one VERY expensive network. Kudos to you for spending the money to find out the actual values. :applaud:

Don't forget to charge-couple them! If they are in the path of the signal then they are in the signal path. ;)

[JeffW]

Maybe he'll turn up with some of those ports next :D

[JuniorJBL]

Who is this masked Audiohack maniac!! :coolness:

Nice job!! :)

[1audiohack]

Hi All;

I thought that since JBL did such a bang-up job with the M2 that to start out at least I should start with this little network in just to be sure I had the top end right.

I am going to depart from the design with a 4435 type cabinet and four 2216's. I just like the form and two 15's close coupled gives me the sound I love. I have one but still have to buy two more I-Tech 5000Hd's, ouch! At first I will likely just run the woofers on a DBX260 and a pair of non DSP amps.

I ran the drivers on the PWT and they are pretty well matched and have consecutive serial numbers, two nice surprises. The top curves are direct drive and the lower two are with the M2 network in series. The network pads the driver down 9.2dB from 3kHz on up and is down 12 dB by 250Hz.

I can't wait for Christmas break to build cabinets!

68670

[1audiohack]

If we get some complete geometry on the ports, since they are flat panel mounted we could make those easily from aluminum bar.

The Everest port and terminal panel? That one is going to be a challenge.

Barry.

[pos]

Well the M2 HF protection network comes with a small surprise.


The cap values are 3.3µF and 4.7µF.
Hi Barry,
Thanks for the confirmation!

[bubbleboy76]

Don't forget to charge-couple them! If they are in the path of the signal then they are in the signal path. ;)

Anyone having a good link for a description of how to do that?
(I might be interested in trying it for my 68uf protective cap, just for fun, if it does not change phase behaviour or something like that.)

[bubbleboy76]

I am going to depart from the design with a 4435 type cabinet and four 2216's. I just like the form and two 15's close coupled gives me the sound I love.


Wow, cool project! :)

[Hoerninger]

Anyone having a good link for a description of how to do that?

Study the circuit (http://www.audioheritage.org/vbulletin/showthread.php?37497-Jbl-4367&p=384175&viewfull=1#post384175)
____________
Peter

[macaroonie]

Something on this page should get the port issue sorted

https://www.google.co.uk/search?q=Flared+loudspeaker+ports&source=lnms&tbm=isch&sa=X&ved=0ahUKEwitlPua0NPJAhXMXBQKHR25DdMQ_AUICCgC&biw=1024&bih=650

[bubbleboy76]

Study the circuit (http://www.audioheritage.org/vbulletin/showthread.php?37497-Jbl-4367&p=384175&viewfull=1#post384175)
____________
Peter

I am not the "study the circuit guy" unfortunately, so maybe it was a stupid question from me :)
If it was an answer like, "put two caps with sum equaling 68uf in parallel, and a 9v battery chargeing the caps" or something that simple, then I maybe could have pulled it off :)

[bubbleboy76]

Found this simple explanation:
http://www.enjoythemusic.com/diy/0911/charge_coupled_crossovers.htm

But for 68uf I need two very large caps in series...

Sorry for the OT.

[Fitero]

Thank you for the interesting technical information and gentle comments.

I don't mean to be obtuse, but this is how I see it; the engineers at JBL have already completed the necessary port calculations, and through subsequent trial and error, have fitted ports that they deem the best compromise for this enclosure.

Port design theory got them close. Listening and modification got them exactly how they wanted it to sound.
It seems more prudent to defer to their experience and knowledge and build as closely as possible to theirs.
By blindly copying their dimensions, I can save an enormous amount of time, and avoid making errors.

Where I can surpass the original design is by making the ports with better flow characteristics. Their method of joining two bells in the center has left a sharp ridge, which for a venturi is anathema and results in disruption of laminar air flow.

So again, a simple measurement of the bell diameters, port length and centre I.D. is all that is needed to make the copy.

If that can't be obtained, then you are right in that I would have to rely on available port calculations to get a brute proximity.

[srm51555]

Anyone having a good link for a description of how to do that?
(I might be interested in trying it for my 68uf protective cap, just for fun, if it does not change phase behaviour or something like that.)

Just double the capacitor value (3.3uf to 6.6uf) and then double the amount of capacitors used. Instead of one 3.3uf you will have two 6.6uf caps in series. I'm going old school and biasing via 9V for now.

Good info here (http://www.audioheritage.org/vbulletin/showthread.php?3555-Bypassed-and-Biased-Capacitors&p=32732&viewfull=1#post32732)

Edit: Sorry didn't see post 31, keeping the post for the CC Timbers link

[srm51555]

I posted this in the M2 thread.

Using a volume of 5.2 cubic feet, a tuning frequency of 27hz, port diameter of 3” and the number of ports needed set at 2 using, the precision port calculator recommends this port http://www.parts-express.com/precisi...-tube--268-368 (http://www.parts-express.com/precision-port-psp-3ofh-3-outside-flare-for-port-tube--268-368) (and it's inner mate) to be set with a total length of 8.85.

[srm51555]

Well the M2 HF protection network comes with a small surprise.

The cap values are 3.3µF and 4.7µF.

Thank you for posting this.

[1audiohack]

Thank you for posting this.

You are welcome! :)

So I have a port question: On the other thread post 842 shows the inside of the port and front baffle board and the port major outside diameter is smaller than the front. Surly to go through the baffle hole in one piece so, do we know the cut out diameter and or the diameter of the flare? At a glance it looks like a eponential flare? Do we know the center minor diameter?

I looked carefully at the ports in my 4365's and they are a plain radius on the front and rear with a piece of tube in the middle. Not as racey as the M2 port. Nothing to learn there.

It also looks like that part of the M2 front baffle is a laminate of two pieces of MDF. How thick?

Edit: Thinking about this a bit, it is doubtful that my box, or many, will tune in just like the M2 so working to make identical ports will only be academic. Edit.

Thank you,
Barry.

[pos]

The geometry of the port baffle should be identical to the upper part of the horn, as the lower part of the grill does fit that part almost exactly (I tried this when I considered reversing the horn...)

[cooky1257]

Where I can surpass the original design is by making the ports with better flow characteristics. Their method of joining two bells in the center has left a sharp ridge, which for a venturi is anathema and results in disruption of laminar air flow.

So again, a simple measurement of the bell diameters, port length and centre I.D. is all that is needed to make the copy.

If that can't be obtained, then you are right in that I would have to rely on available port calculations to get a brute proximity.

http://koti.kapsi.fi/jahonen/Audio/Papers/AES_PortPaper.pdf

[ivica]

You are welcome! :)

So I have a port question: On the other thread post 842 shows the inside of the port and front baffle board and the port major outside diameter is smaller than the front. Surly to go through the baffle hole in one piece so, do we know the cut out diameter and or the diameter of the flare? At a glance it looks like a eponential flare? Do we know the center minor diameter?

I looked carefully at the ports in my 4365's and they are a plain radius on the front and rear with a piece of tube in the middle. Not as racey as the M2 port. Nothing to learn there.

It also looks like that part of the M2 front baffle is a laminate of two pieces of MDF. How thick? If we can get the real geometry I will make the ports for anyone that wants them at material cost.

Thank you,
Barry.

Hi Barry

I have read somewhere that the suggested port flare would have be about 5 to 7 deg-off-axis, but I have no idea about M2 port off-axis flare, is it conical, hyperbolic or exponential.
From the:
http://www.aes.org/e-lib/browse.cfm?elib=11094
"Maximizing Performance from Loudspeaker Ports" [Alex Salvatti and Doug Button, JBL Professional,Allan Devantier, Infinity systems,Northridge, California]

I have understood that COSH function would give good results, on the other side seems to me that if the curvature radius equals to the port length would give very low SPL compression. On the other side port diameter vs 'inlet radius' about 5 (Dp/r) would be 'loss-less', so different walls flare can be expected.

May be some ideas can be find in JBL patent: US7711134
http://www.google.com/patents/US7711134


regards
ivica

[Fitero]

For the level of precision that I wish to attain;

The dimensions that are missing to make an approximate facsimile are the inner bell diameter and the port's minimum inner diameter.

A more precise measurement of port length could be obtained by placing a straight edge across the port bells and passing a tape measure through the port and obtaining the measurement.

For the inner minimum diameter, and in the absence of a snap gauge, a piece of paper, gradually folded into smaller dimensions until it fits perfectly in the smallest portion of the port then measured would be quite close.

This port could be modified to approximate the OEM port dimensions once they are known.
The curved lower port mount panel appears to be 21mm thick at it's maximum, judging from the JBL's published dimensions and those that have been posted here.
This is how the port molding pieces are joined and typically mounted to front baffles;
http://i.ebayimg.com/images/g/-f4AAOSw5ZBWOt9k/s-l1600.jpg

[pos]

Nice!
Where does this port come from?

[Fitero]

http://www.ebay.com/itm/331700198468?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Almost the exact outer diameter as the OEM ports too.

Duh! Same thing, but much cheaper here;
http://www.parts-express.com/flared-port-tube-3-id-x-11-l-with-5-flared-ends--269-165

[pos]

It looks like it is too long though, and the inner part looks too large...

[Fitero]

It is, but it can be cut at the junction seam, heated and re-molded into a small diameter, then cut to the correct length and re-joined.

The inner bell can be expanded to the correct diameter through heating and re-molding as well.

Once I am able to obtain the correct dimensions of the original ports, then I will buy one of these and give it a go.

At the very least, it may provide me with a mold to make a fiberglass port with if I choose to go that route.

[ivica]

It looks like it is too long though, and the inner part looks too large...

Hi POS,

If Vb=130 Lit, Fb=27Hz, with TWO vents Dia=76mm, then Lv=198mm, owing to BB6.

regards
ivica

[cooky1257]

http://koti.kapsi.fi/jahonen/Audio/Papers/AES_PortPaper.pdf

Fig40 profile 'c' ?

[srm51555]

So after searching for input control solutions to use with a Crown dci 4300 N for an hour, I decided to leave that for another day and work on the M2's. Over the past week or so I was able to mount the waveguides, ports and T-nuts of the woofers. I wanted to see how it looked with the woofers in so I mounted them in the second picture.

69131

69132

Still on the list:
-Crossover
-Mount Banana Plug Jacks
-Figure out cabinet feet
-Grills

I was a little disappointed the crown doesn't have digital cards in it, I never even thought of it when I was looking it over. So any control solutions will be much appreciated. The only Preamp I have left is a Mcintosh C32 and it's 30+ years old so I really didn't want to turn it up to get the proper gain needed for the analog card. The best solution I came up with is to use a BSS EC-V and some sort of network switch to provide power and run the CD player directly into the Crown. Thanks, Scott

[grumpy]

For somewhat less $, there are the options in the GPIO-VCA notes.
(Similar function, and form factor) curious to see what you end up with.

[pos]

Sweet! :coolness:
How did you mount the horn to the enclosure?

Regarding the feet, I will use 4 of these per speaker on my clones: http://www.audiophonics.fr/fr/pointes-absorbeurs-contrepointes-pieds/pied-conique-caoutchouc-amortissant-30x36mm-m8-unite-p-8954.html
Based on the weight of the M2 the resonance frequency will be under the normal range and the isolation will be pretty high. This can all be calulated and work pretty well. The shape of those rubber pads also allows for some margin on the weight (the weight/resonance frequency curve is not a strait line because the thinner part will compress more).
I need isolation because my I have an old style parquet with floorboards on joists...
But of course depending on your floor you might want to couple the speaker to the floor (using spikes, the so called "decoupling" ones :blink:) rather than isolate it if you have an hard and heavy floor.

[srm51555]

Sweet! :coolness:
How did you mount the horn to the enclosure?

Regarding the feet, I will use 4 of these per speaker on my clones: http://www.audiophonics.fr/fr/pointes-absorbeurs-contrepointes-pieds/pied-conique-caoutchouc-amortissant-30x36mm-m8-unite-p-8954.html
Based on the weight of the M2 the resonance frequency will be under the normal range and the isolation will be pretty high. This can all be calulated and work pretty well. The shape of those rubber pads also allows for some margin on the weight (the weight/resonance frequency curve is not a strait line because the thinner part will compress more).
I need isolation because my I have an old style parquet with floorboards on joists...
But of course depending on your floor you might want to couple the speaker to the floor (using spikes, the so called "decoupling" ones :blink:) rather than isolate it if you have an hard and heavy floor.

I used the thread forming screws for plastic recommended by Donc found here http://www.mcmaster.com/#99512a465/=10lcxgv along with washers. I originally used a 1/2" spade bit for all of the holes, but the spacing was slightly off so I ended going over them with a 13.5mm bit to get the horn to fit. I used speaker gaskett material on the inside and outside of the screw holes. There was plenty of room to work with inside so screwing them wasn't too bad.

The speakers will be sitting on concrete. The waveguide for me is already at ear level so I want to keep the height of the feet to a minimum. Thanks for posting a link to the rubber feet, that seems like a very reasonably priced option.

Thanks,
Scott

[sebackman]

Hey Scott,

Excellent job, those will surely be enjoyable.

I have some questions related to POS question above.

I’m mounting my M2’s to some cabinets and found that they are not flat on the mounting side, they are warped ( all 5 of them) so when I lay them on top of the baffle the sides are not flush on both sides.

When laid on the “nose” and using a ruler across on the rear side, there is a 3 mm difference on either side. The centre part is not in line with the sides but actually slightly higher that the outer sides.

How did you solve that? Did you see it?

One way would be to reduce/lower the baffle vertically in the centre or potentially use a thicker gasket on the sides.

I also had the same problem with the mounting bosses not exactly aligned…

I also found that they are not parallel on the sides, mine are 1,5 mm narrower at the top than the bottom. This poses a bit of a problem to me as I will mount them upside down and using the out sides of the waveguide as sides in the cabinet. The baffle is correct for the bottom but a few mill to narrow at the top….

Maybe I will have to bring out the good old router again. A bit reluctant to do that as the waveguide material eats routers….

Kind regards
//RoB

[srm51555]

Hey Scott,

Excellent job, those will surely be enjoyable.

I have some questions related to POS question above.

I’m mounting my M2’s to some cabinets and found that they are not flat on the mounting side, they are warped ( all 5 of them) so when I lay them on top of the baffle the sides are not flush on both sides.

When laid on the “nose” and using a ruler across on the rear side, there is a 3 mm difference on either side. The centre part is not in line with the sides but actually slightly higher that the outer sides.

How did you solve that? Did you see it?

One way would be to reduce/lower the baffle vertically in the centre or potentially use a thicker gasket on the sides.

I also had the same problem with the mounting bosses not exactly aligned…

I also found that they are not parallel on the sides, mine are 1,5 mm narrower at the top than the bottom. This poses a bit of a problem to me as I will mount them upside down and using the out sides of the waveguide as sides in the cabinet. The baffle is correct for the bottom but a few mill to narrow at the top….

Maybe I will have to bring out the good old router again. A bit reluctant to do that as the waveguide material eats routers….

Kind regards
//RoB

I did not see any difference when dry fitting them to the cabinets, but then I really wasn't looking for it either. Hopefully someone can chime in and provide some data too. I assume since mine are already mounted they wouldn't be a good test subject anymore since they may already have been "bent" into shape. If no one responds then I will pull them for information's sake

Thanks,
Scott

[srm51555]

I was a little disappointed the crown doesn't have digital cards in it, I never even thought of it when I was looking it over. So any control solutions will be much appreciated. The only Preamp I have left is a Mcintosh C32 and it's 30+ years old so I really didn't want to turn it up to get the proper gain needed for the analog card. The best solution I came up with is to use a BSS EC-V and some sort of network switch to provide power and run the CD player directly into the Crown. Thanks, Scott

Here is what I'm going to go with:

http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=385363&viewfull=1#post385363

I posted it into the main thread just in case someone wasn't watching this one.

[srm51555]

I had some time so I removed the waveguides and they appear to have the same 3mm difference between the center and outsides Rob is talking about. Thanks, Scott

[sebackman]

Hi Scott,

Thank you for confirming.

I thought so. I need to add some gaskets to cover the difference and potentially take down the baffle a little in the middle. My WG will be the top and the sides of the cabinet so it better at least look flush...

Kind regards
//RoB

[srm51555]

Hi Scott,

Thank you for confirming.

I thought so. I need to add some gaskets to cover the difference and potentially take down the baffle a little in the middle. My WG will be the top and the sides of the cabinet so it better at least look flush...

Kind regards
//RoB

I'd be curious to see what JBL is doing when assembling the M2. I can't imagine them modifying every cabinet or waveguide when there banging out production. Can someone think of a way to measure if the waveguide even gets warped when the waveguide gets screwed down? I might try to make a curved cardboard template with the one that is out of the cabinet and compare it with the one that is still in it's cabinet.

Thanks,
Scott

[sebackman]

Hi Scott,

I just stole your idea and bought 4pcs 3" reflex ports with only the inner flare to be used in both ends.

This version has separate flares and a basic plastic pipe inbetween. Normally the have a smaller flare for in box use and a bigger for external mount. The thing is that the flates are the same but the external is much lager to look impressing....

This will bring down baffle surface for the ports so they acctually fit. Thank you for the idea.

kind regards
//RoB

[srm51555]

Both crossovers and banana plugs have been installed. Even though the crossover is only 4"x6" I found it difficult to find a place that made sense for mounting the crossover. I ended up mounting it on the cross member of the top brace for now until I rip everything apart for paint. BTW any input on what color I should paint it other than black? My DCi is at my buddy's house awaiting an EC-V that should be here this week. If everything goes right I should be listening this weekend. Maybe the first album will be The Long Run by Eagles, because it sure feels like it.:p

69666

69667

[bubbleboy76]

Regarding color, I would love to see M2 (including horn) painted in faux concrete.
And then maybe some grafitti on it, to top it off :)

[pos]

Do it ;)

[srm51555]

Regarding color, I would love to see M2 (including horn) painted in faux concrete.
And then maybe some grafitti on it, to top it off :)

I actually already had a pair of Altec diy's that had concrete looking paint on it. The 9cf cabinet never blended very well. I was originally thinking for Ferrari red but the give size may be too much, now thinking white maybe in the running.

Thanks,
Scott

[bubbleboy76]

They are too big for red, I think.
White, I probably would do myself, to try to blend them in with the walls.

Green would be a nice tribute to 4313b and his hair color! ;)
British Racing Green maybe? :)

[srm51555]

The British Racing green looks good too. I wonder how they would look in shag:rotfl:. Blues Brothers is one of my all time favorites.

69688

[johnlcnm]

No connection the sale of these amps, Crown Itech5000 HD's: For the M2 builder. http://www.ebay.com/itm/361481675547?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Regards,
John

[srm51555]

Last week Thursday I received my DCi 4|300N and with much excitement began unpacking it. After about 3-4 minutes of the amp performing it's thing during power up Audio Architect detected it. I soon found out I would be needing a network switch since the amp only has one Ethernet port and that will be used for the EC-V. The next day as luck would have it, Goodwill had one with box for $4.99. Happily I went home and began setting up the amps network.

3 hours later of trying everything I realized the network switch just wasn't going to work. I wasn't even planning to have it in the main system, but figured I needed it for initial startup. Defeated:(.

The next day I thought to myself what would happen If I loaded the setting on the Amp and the EC-V separately and try it a set of test speakers. It actually worked and was as happy as I was relieved because the end is near. After an hour or so using the test speaker on all 4 channels I decided it's time to hook up the real deal. The volume was kept low because the kids were sleeping but my first impressions were not good, then I realized the right woofer was not playing. After checking all connections I still found nothing. I decided to check the settings in AA. Everything looked as it should but reloaded the amp just in case. This worked. By now the kids are up and other things needed to be done around the house so I loaded a CD and put it on repeat and closed the door(No Grills yet and Kids:eek:). This ran for about 2 hours. I shut everything down and waited for about another 2 hours to see if the channel thing would return. It did not. After a small listening session I must say these speaker are dynamic as hell and the horn dispersion is unbelievable. Also the SPL is plenty with the 4|300. I wasn't able to get a total impression of the sound yet because the placement is not proper yet. Should be able to get that done tonight.

Note: because the EC-V was showing as "unmatched" in AA and wouldn't match using the "Auto Match" button, I had to call BSS on Friday. They told me to select the EC-V under the "Found Devices" folder and click and drag it over to the EC-V representation in AA. BSS has done a great job with AA and finding the devices. It took twice as many hours finding my BLU-100 in LA.

Thanks,
Scott

[bubbleboy76]

I`m going för building a M2-clone as well:) Found the horns and modified plates second hand in Sweden. (what is the chance of that). The rest I will get from speaker exchange.

I have some serious problems of deciding what amps or DSP to use. I think I will go for BSS or crown because simplicity with presets. I have a alternative to a nice price from a friend to buy a Crown CTs 8200 with integrated BSS-dsp. But I`m not sure if it is powerfull enough. It is 8ch and the plan is to bridge four channels for the 2216nd`s. The 2216 is a 6ohm driver. The CTs is not specified fo loads under 8ohm bridged. It leaves 4-500RMS per channel bridged. http://www.crownaudio.com/media/wysiwyg/CTs/CTs_Multi-Channel_USP-CN.pdf

My other 3 times (at least) more expensive alternative is a Crown 4x3500.

I like to play loud some times.
Today I run 18" subs. I hope to not be needing any subs whith my M2`s. Therefore I`m unsure if the CTs 8200 will be enough.

Where is the limit in RMS set on DSP in the Crown HD amps? 1000rms?

Plan 3 could is to get the CTs and use it`s dsp for a bigger amp thru the cobranet.

Plan 4 external DSP and use my Lab.gruppen amps

Suggestions?

Best regards
Karl

regarding dsp, one minidsp opendrc-di per speaker would be the best choice, I think.
I guess pos will publish very advanced FIR-settings with phase linearization, when he gets his M2:s up and running.

[johnlcnm]

No connection the sale of these amps, Crown Itech5000 HD's: For the M2 builder. http://www.ebay.com/itm/361481675547?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Regards,
John

Purchased one of these Itech amps. Manufactured date was 11/2014. Unit was apparently factory serviced by Crown in 11/2015. There was a certification/checkout card in the box. Unit looks new and performs as well as my bought new Itech5000. Highly recommended.

Regards,

John

[srm51555]

Those looked very tempting, thanks for posting.

[Mctwins]

Hallo!

Very good amps those I-tech HD. Read the manual, lot's of great features.

[johnlcnm]

Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen.

Schematic of the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=382327&viewfull=1#post382327) - Note: C2 in the schematic shows a value of 33.3uf, this is a typo. the correct value is 3.3uf

DSP File (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=362894&viewfull=1#post362894)

Inside the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=375530&viewfull=1#post375530)

Outside the M2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=374872&viewfull=1#post374872)

M2 Dimensions (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=374875&viewfull=1#post374875)

Horn Mounting (http://www.audioheritage.org/vbulletin/showthread.php?36789-Compact-monitor&p=374486&viewfull=1#post374486)

Horn Mounting pt2 (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=380622&viewfull=1#post380622)



Scott,

I believe that the input coupling cap in front of the horn driver pad should be 33.3 uF plus the 4.7 uF. That along with the forward looking equivalent resistance of 7.1 Ohm, (into the pad/driver), would fall into the ball park with about a seven Ohm impedance. This would certainly become a part of the high pass network.

Regards,

John

[srm51555]

Scott,

I believe that the input coupling cap in front of the horn driver pad should be 33.3 uF plus the 4.7 uF. That along with the forward looking equivalent resistance of 7.1 Ohm, (into the pad/driver), would fall into the ball park with about a seven Ohm impedance. This would certainly become a part of the high pass network.

Regards,

John

Hi John,

I wish that was the case before I purchased the caps to charge couple the network. Barry confirmed the 3.3uf value here (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=384220&viewfull=1#post384220).

Thanks,
Scott

[johnlcnm]

Yes, that's pretty hard to argue with! Wow. Are the pad resistors per the schematic?

John

[sebackman]

Hi Scott

Did you ever get around to measuring what resonance frequency you got from the ports in your M2 cabinet?

Fs of the 2216Nd is 36Hz mechanical from the TechBot file but seem to be all the way up to 39,3Hz from the Mlssa measurement also posted in the same document.

Some post in the lengthy M2 thread seem to indicate that the system Fs is 27Hz for the M2 system.

Not really sure what happens then. I will post a separate thread on that. -Also posting this question in the other DIY M2 thread.

Kind regards
//RoB

[srm51555]

Hi Rob,

I also have not measured anything yet. I purchased a Focusrite Scarlett 2i4 last week and still need to get a microphone. I'll be sure to post any findings when I get it set up. Unfortunately time is limited right now.

Thanks,
Scott

[sebackman]

Hi Scott,

Excellent. I would be really good with some comparable measurements. I will start measuring on the “Compact Monitor” in a week or so.

Maybe I’m breaking in open doors here, but anyway.

There is actually a very simple way to measure system/cabinet resonance with a minimum of SW & HW. If you can connect your computer to your preamp / power amp and play music from the computer you can do this.

Install a single basic resistor 10W (or higher) with 30-100 ohms in series with the speaker cable from the power amp to the speaker. Just add it in series with either of the plus or minus poles on the speaker. This is to take out any unwanted measurement errors from the power amp.

Connect a basic volt meter after the resistor right across the plus an minus poles of the 2216Nd. The volt meter can be any basic volt meter as long as it can do AC. If you don’t have one it can be a real “el-cheapo” for a basic check, get it from Home Depot or similar. If it can do RMS AC measures it is better, but not really needed for this.

Then you download a sine generator (app / program) to your computer from the Internet and install. Make sure you can hear the signal in you speakers. There are many to choose from and I don’t really know the difference. I normally use an analogue calibrated tone generator… Old School… But my fellow JBL nut's over here do this all the time with their computers.

Then with your computer slowly sweep a sine wave signal (does not have to be loud at all) from say 20Hz to 50Hz. At the frequency point where you get the lowest voltage reading across the 2216Nd on the volt meter is where you have the system resonance in the cabinet.

Simple as that. No mike or other SW & HW needed.

It would be nice to see where you came out. Give the excellent quality of your work, probably spot on.

Kind regards

//RoB

[pos]

Another (less precise, +/- 1Hz) method is to use a signal generator (I use a simple iphone app called "signal gen" for this) while touching the cone and find the frequency for which the cone movement is at a minimum (and air movement from the ports maximal).

With this method I found my current M2 build was tuned to around 24 or 25Hz (the tubes are too long, I prefer to aim for a lower tuning frequency and then cut them step by step...).

[srm51555]

Thank you both. I'll be trying both methods, but probably the one POS recommended first because painting the kitchen is taking all of my time.

[SMT]

Looking for suggestions from the genius and knowledge that frequents this forum. I have been thinking of doing a 5.0/.1 system of JBL M2. The biggest hurdle is crossover/DSP $$$. Obviously a 5.0 setup would require a minimum of 10 channels,though more would be preferable for possible expansion and allowance for subwoofer(s), of low latency crossover/dsp.


I also have the challenge of wanting to route my cable box and Oppo blu-ray sound through them as well.

Any recommendations for a low expenditure way to accomplish this and minimize the DAC/ADC conversions? I would like to run my home theater as well as multi-channel music(I have written off DSD for now as it would just be to expensive, from a server through these, also have a vinyl setup as well, I suppose mini-dsp? Some Pro audio interfaces exist but i am unsure of how i would get the cable box and Oppo blu-ray routed and not suffer video/audio sync issues. Maybe a Lynx AES sound card? I dunno...

I currently us JRiver MC on an audio server. Home theater is currently an Oppo BDP-105D and a Sony STR DA5300ES and a Time Warner cable box.

Thanks in advance for any suggestions.

edit: An analog crossover would be acceptable in the interim, though I lack those skills as well.

[sebackman]

Hi SMT,

This is probably way OT…

You already have the base. The BDP105 can take SPDIF, USB and HDMI in from your external units and output both multichannel HDMI and SPDIF working as a digital switchboard. With that you don't really need a preamp. And the digital volume is pretty decent if you run 24bit.

This is all fine for digital 2 channel but as the BDP (or most other DVD’s) cannot output decoded digital 7.1 (or whatever HT format you use) you have a couple of choices to make. If you can stay in the analogue world from the DVD and accept an ADC conversion for HT use that is one route. If you want to completely avoid ADC you can either get a DVD that can output decoded HT 7.1 digital via SPDIF or AES (ie a Oppo BDP-93/103D with a Vanity card installed = decoded digital HT SPDIF out or a Meridian 621 decoder).

-Or you can introduce a HT processor that can decode the digital MUX (multichannel) SPDIF signal from the DVD and send it on as separate SPDIF channels after decoding, like a Meridian pre. That is what I do.

When it comes to DSP the BSS units can do both analogue and digital in. -And a mix of them. All cards are 4 channels and can be mixed and expanded as needed. You have in total 256 channels to play with. All base units can do 16 channels in or out (4 cards x 4 channels). You can interconnect more units via Cobranet or BluLink to get the combination you need. I use 8 channels digital in (2 cards) and 16 channels analogue out (2 cards = 8 channels and a BLUBOB = 8 channels) from a BLU800.

Hence, you can get a BSS with both digital and analogue in. Two channel digital (use 2 out of 4 channels on one digital input card) for 2 channel all digital listening direct from the DDVD (SPDIF, no pre). And add two 4 channel analogue input cards for HT use and feed analogue direct from the DVD (RCA or balanced, no pre). This gives you room only for one additional card in that chassis to add one card with 4 analogue channels out. But you can add an extra chassis (max 16 additional analogue outs from 4 cards) or one or two fixed output units (BSS BLUBOB) that hold 8 analogue outputs.

ALL the BSS’s does have a very good volume controls built in on the analogue output cards. Control them from a wall controller or your iPad.

I use a Oppo BDP83 (soon to be shifted to a BDP93 with a Vanity card to get the HD audio that normally only goes through HDMI) feed digital multichannel SPDIF to a Meridian G68 for HT decoding and from that onwards 7.1 digital SPDIF ( 4 leads) to the digital inputs in a BSS BLU800. All DSP processing is done in that unit and I have added a BLUBOB to get more analogue outputs before hitting the power amps. One BLU160 or BLU800 can do all the DSP you need for 5.0/5.1.

What I suggest you should be looking for is a used BSS BLU16, BLU80, BLU 160 or BLU800 unit and get one or several digital input cards as how you decide to go per above. The analogue setup is on par with most (ADC) DSP solutions on the market, or correctly setup may even be better. The digital solution is better.

Good luck with your design.

//RoB

[SMT]

Rob, big thank you for your detailed response and suggestions! Lots of good info. I was unaware of the Vanity cards, very interesting option.

And yes, my apologies for meandering off topic.

Shane

edit: well, that is embarrassing....*Apologies:o:

[bubbleboy76]

I use the VanityHD in my Oppo 103.
I love it.

[johanwholst]

My temporary M2 bastard moved up to our living room today. Cabinet is a reused 140l box designed for 2225, but fits 2216 good enough for now. tuning to 30hz. horn in a provisional stay on top.
Will commence work on a proper cabinet next week, and will in the meantime work on dsp settings and try out the 2450 with truextent as an alternative to D2
Hypex DLCP does crossover duty and crown cts1200 on 2216 and day aleph J on D2.
Easy to like sound, on nice to work on a two ways compared to my four ways active horns that will rest in the basement for some time.

70672

[honkytonkwillie]

It's really hard to see your speaker in front of that spectacular view out the window. Looks like Alaska, where I live.

[johanwholst]

Photo taken like that deliberately. They are not much to look at, but hope to build a box that would justify placement with that kind of view.

[hlaari]

Nice view :)

it will be nice to visit you in the summer, then you will be finish with the new M2 enclosure
I promise to take some interesting parts with me:D



Ari

[srm51555]

Looking good



.... try out the 2450 with truextent as an alternative to D2


I also look forward to your thoughts on this combination in comparison to the D2

[sebackman]

Hi,

Maybe POS has had the time to do some lab measurements of the D2 on the M2 waveguide. That would be interesting to see.

Regarding other drivers a modern 4" core with a 476Nd diaphragm seems to measure the best and may be the best alternative for a 2-way setup. The Be's from Truextent falls off much earlier and will need more Eq/DSP or a tweeter as in the other K2 models.

I have not tried the Mg diaphragms in the unobtainable 476Mg. Member 4313b has a pair with a pair if M2 wg's to go together I don't know if he has had a chance to messure the combo.

Kind regards

//RoB

[johanwholst]

I have previous experience with 2450be on PT f95 Hf. It is totally free of breakups up to 16k, but require quite heavy EQ to play that high. We have more or less concluded that a tweeter introduces more problems than advantages combined with the pt horn and 2450be and that flat to 16k gives my ears all the sparkle and spaciousness I desire from a Hifi setup. Could be due to many years playing with guns and chainsaws :)

I hope to conclude likewise with the m2 waveguide as the two way concept is so attractive to me, and the 2450 with truextent is a really sweet sounding driver.
Hope to experiment this week and will post my subjective impressions compared to D2.

Again setbackman, thank you for your extensive measuring of different driver with the m2 guide!

one last question: is the 476nd diaphragm "obtainable"? would it fit 2450/2451? you certainly mean nd and not mg? (that was three questions...)

[hlaari]

one last question: is the 476nd diaphragm "obtainable"? would it fit 2450/2451? you certainly mean nd and not mg? [/QUOTE]


I think at Rob is talking about 475Nd diaphragm:)

there will be interesting to measure 476Mg on M2 waveguide
I think at there would be ok to try my 1501Al-1 in 140 - 180l box tuned around 25Hz


Ari

[johanwholst]

I suspect the quite small cabinet size of the M2 monitor is due to aesthetic and practical reasons. Quite sure both the 2216 and definately Al1501 would be happier in a much larger cabinet.

Looking forward to play with some of your parts this summer Ari!

[pos]

I did not have time to measure the 2540SL-Be of the M2 waveguide yet, but today I did some measurements comparing the original passive network (albeit with different resistors and caps brands) and a simple 30uF Solen cap, in an effort to get back those 9dB of passive attenuation and be able to use an amplifier with roughly 1/10 of the power...
I can share the preliminary correction adjustments if anyone is interested.

By the way, does any of you leave near Reykjavik?

[hlaari]

I did not have time to measure the 2540SL-Be of the M2 waveguide yet, but today I did some measurements comparing the original passive network (albeit with different resistors and caps brands) and a simple 30uF Solen cap, in an effort to get back those 9dB of passive attenuation and be able to use an amplifier with roughly 1/10 of the power...
I can share the preliminary correction adjustments if anyone is interested.

By the way, does any of you leave near Reykjavik?

In fact I live and work in Fareo island right now, and my speakers and parts are in storage in Iceland
are you going to Iceland?

[johanwholst]

That would be intresting to see Pos.

I live approximately 3 hours drive north of Reykjavik. You are most welcome if you happen to be in the area!

[pos]

I will be in Reykjavik the week after next, but only for 2.5 days, and for work... :'(

[hlaari]

I suspect the quite small cabinet size of the M2 monitor is due to aesthetic and practical reasons. Quite sure both the 2216 and definately Al1501 would be happier in a much larger cabinet.

Looking forward to play with some of your parts this summer Ari!


I am also looking forward to meet you and make some speaker testing, there is also good to find someone in similar hobby like me in Iceland
we will see how big enclosure 1501Al-1 need to get the best performance out of them, you can be sure at I am very excited to try them and also to see how good 476Mg will work on the M2 waveguide

I like to know if 4313b have run his 476Mg on M2 waveguide, perhaps he have made it?

[hlaari]

I will be in Reykjavik the week after next, but only for 2.5 days, and for work... :'(


there would have bin nice to meed you!

[hlaari]

there would have bin nice to meed you!

Sorry for my poor spelling!
I was going to say there would have bin nice to "meet" you:)

[srm51555]

Thank you both. I'll be trying both methods, but probably the one POS recommended first because painting the kitchen is taking all of my time.

Rob and friends,

Kitchen is still not painted but I had some time and found my speaker cabinets seem to be tuned to around 25hz. Kitchen cabinets were found to be tuned much higher :p. I will be performing the method Rob has suggested soon.

Thanks.
Scott

[ivica]

I did not have time to measure the 2540SL-Be of the M2 waveguide yet, but today I did some measurements comparing the original passive network (albeit with different resistors and caps brands) and a simple 30uF Solen cap, in an effort to get back those 9dB of passive attenuation and be able to use an amplifier with roughly 1/10 of the power...
I can share the preliminary correction adjustments if anyone is interested.

By the way, does any of you leave near Reykjavik?

Hi Pos,
It would be nice if You can share the preliminary results with us.
Regards
Ivica

[Robh3606]

476Mg will work on the M2 waveguide

It will work just fine

Rob:)

[bubbleboy76]

Come on guys, where are all the DIY M2 projects?!
I want to see pictures. I want to see measurements. I want to read listening reviews!
Surely, there must be many finished projects by now! I have only seen 2-3 finished projects, I think.

[1audiohack]

All my parts are still in boxes. :(

Barry.

[SMT]

I hit a hard wall, should of bought my D2 drivers when they were available. :(

[srm51555]

I want to see measurements.

Just started the learning curve of this last night. Took the mic and Focusrite Scarlette 2i4 out of the box and verified they work when hooked up to the PC. I've never used REW or any other measurement tool before so it will be some time. Before I start this though I still need to find what frequency my cabinet's are currently tuned too for Rob (sebackman).


All my parts are still in boxes. :(

After listening to the single 2216nd's your 2.5 version is going to be awesome.


I hit a hard wall, should of bought my D2 drivers when they were available. :(

In another thread Barry suggested that he went through other JBL pro dealers other than speaker exchange to receive his D2's.

Thanks,
Scott

[4313B]

I hit a hard wall, should of bought my D2 drivers when they were available. :(I received my three very recently. Ordered them last April, waited the obligatory year for delivery.


All my parts are still in boxes.Mine too.

I am actually looking forward to building some boxes this summer.

[johanwholst]

I just finished cutting all the pieces for the cabinet. Remains to order ports, gasket tape, threaded inserts etc... but 2216nd and D2 are up and playing in a recycled cabinet

Hope to finish the boxes before mid june

[johanwholst]

How do you M2 diy guys route out for the 2216? Is the rubber lip on the 2216nd sunk into the baffle plate resting on a sunken edge or do you leave it on top of the front baffle?

[dprice]

I sized the opening on the front front baffle such that the rubber lip is on top of the front baffle and covers the slight gap between the frame and the baffle.

[johanwholst]

I have only seen the original once, but isn't the rubber sunk into the front baffle? doesn't really matter as long as the rubber seals a gap...

Then you sink the woofer approx 1/2" ?

[pos]

Is the rubber lip on the 2216nd sunk into the baffle plate resting on a sunken edge
That is how it is done on the original:
7114971150

According to Stéphane (http://www.audioheritage.org/vbulletin/member.php?21977-Steph) the additional baffle is around 15mm, so the edge must be 2 or 3mm deep.

[johanwholst]

Great pos. Thanks for the confirmation.
This was my plan. 16mm plate on top of the 25mm. sink edge at 13mm for the rubber lip

[dprice]

I sized the opening on the front front baffle such that the rubber lip is on top of the front baffle and covers the slight gap between the frame and the baffle.

I should have clarified that I used ~12mm plywood on the front baffle so no need to cut a recess for the lip.

[johanwholst]

that's a good way. I had plenty of 16mm mdf, so I will route it down for the lip.
Not decided with the ports yet if I should just route the flare or use a plastic flared front or end piece. Looks kind of cheap and plasticky...
Got 5mm threaded inserts (Rampa) for the woofer mount, and 4 pole speak on for the connection in the mail now.
Next decision would be if I should ditch the network, use only the capacitor, or go for the whole thing Witt attenuating resistors.. Guess I have to decide on amps firsts
Any opinions if the resistors actually influence the EQ curve other than the attenuation?

[Mr. Widget]

I have only seen the original once, but isn't the rubber sunk into the front baffle? doesn't really matter as long as the rubber seals a gap...

Then you sink the woofer approx 1/2" ?If you really want M2 performance, every detail matters:


Early in the M2's development the portion of the baffle where the 2216nd mounted was flat all the way to the bottom of the baffle panel (the waveguide was always proud of the woofer baffle). After uncovering the response anomalies and determining their cause, Devantier re-designed the woofer baffle with the lower baffle area proud of the woofer mounting area, which eliminated the anomalies. I know this because after seeing the initial prototypes with the flush baffle, Alan showed me a later version with the step. I asked him why he added it, since to my mind the step would cause diffraction, and he explained that the stepped baffle actually eliminated response anomalies in the 500Hz region without causing any audible or measurable diffraction effects. (Which in hindsight makes sense, since the wavelengths at the top of the 2216nd's operating range in the M2 are around a foot long, too large to be affected by the baffle step.)

So if it's a true M2 clone you're after, you need to include this stepped baffle—it's there for performance reasons.


Widget

[pos]

Next decision would be if I should ditch the network, use only the capacitor, or go for the whole thing Witt attenuating resistors.. Guess I have to decide on amps firsts
Any opinions if the resistors actually influence the EQ curve other than the attenuation?
Oh yes it does, by attenuating the impedance peak.
If you remove the lpad bu keep the 1kHz cap, the resulting response curve will have a peak corresponding to the impedance peak.

If you want to remove the lpad in order to be able to use a low power amp, then you should only use a protection cap.

I made a few measurements comparing the original (cloned) network and a simple protection 30uF cap.
I can publish the required EQ to compensate for the difference.
What DSP unti are you using?

[pos]

Thank you for posting this here Widget, I missed it!
http://www.audioheritage.org/vbulletin/showthread.php?38178-JBL-4333-s-or-4355-s-Or&p=390024#post390024

[johanwholst]

Thanks widget.

POS: I am using Hypex DLCP for now, but struggle with too few PEQ's. I have Minidsp 2x4hd inbound for the pure fun of testing it, and wait paiciently for the perfect pre/dsp solution to come in hopefully near future. Maybe Hypex oem two by four (Isis ;)) could be it? We will see in Q4 I believe.

Please share your comparisons. Both me and a Norwegian DIY friend using Hypex experience the area 7-10k hz quite hot with your EQ, and I need to notch this area down approx 3-4dB with a wide Q.

[johanwholst]

Just to clarify mr Widget; with the stepped baffle, hsosdrum refers to the protruded lower 1/3 of the front? In other words, the port section protruded?

[pos]

Thanks widget.

POS: I am using Hypex DLCP for now, but struggle with too few PEQ's. I have Minidsp 2x4hd inbound for the pure fun of testing it, and wait paiciently for the perfect pre/dsp solution to come in hopefully near future. Maybe Hypex oem two by four (Isis ;)) could be it? We will see in Q4 I believe.
Right now using one openDRC per side is the easiest way I found.
I have high hopes on Tranquility bass (http://www.diyaudio.com/forums/digital-line-level/264743-hi-end-dsp-based-multi-channel-integrated-preamp-crossover-dac-project.html)' system, but it takes time for such a product to make it to the market..



Please share your comparisons. Both me and a Norwegian DIY friend using Hypex experience the area 7-10k hz quite hot with your EQ, and I need to notch this area down approx 3-4dB with a wide Q.
This is not my EQ, but a straight copy of the one found in the Crown DSP/amp.
Many on-axis measurements of the original M2 show this phenomenon.
eg:
http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=380146&viewfull=1#post380146
http://www.audioheritage.org/vbulletin/showthread.php?35538-New-JBL-M2&p=360555&viewfull=1#post360555

I did not have the chance to do extensive measurements myself yet.

[johanwholst]

Pos: Could you please publish your suggestion for compensating for the complete network when using only the cap?

Yes I am also quite eager to see what comes out of tranquillity bass project. That project as well as the Soon to be released Hypex is why I'm reluctant to go for the opendrc as is. I expect Minidsp to upgrade the 4x10 with Fir capabilities anytime soon as well. (sorry for the slightly off topic...)

[pos]

Here are the rephase settings for the 30uF protection cap.
The gain is 9dB lower compared to the original rephase settings (as found in the google doc).
This will of course have to be adapted to the gain of the amplifier in use, as the main purpose of this modification is to be able to use a lower power/lower gain amp...

The main modification is the addition of a -11.5dB low shelving (in effect converting the ~250Hz HP into a 1kHz HP), but some other EQs have been modified.
The matching between this and the original settings/schematic is around +/- 0.2dB in the 500Hz-20kHz range.
The phase tracking is also very good at around +/- 1° in the same range.

Copy and use rephase "load from clipboard" functionality.


rePhase settings
eNrtW9tu4zYQ/RVBTy0qEyR192OLFGjRBdrn3UCgbdomViJVSXY2G+TfOyQlRZa 1wQabXpASCSxz
hpxDnsOLwYEe/I36VOxF2fGm9dfv3/t+4IexfxssfLsN/C2XUFPIg7/2SdWCY3vk24/tqQJDhLM4
xZTluw3Lwy3ZJ3G2i1OO83yT7ONI125U287xCMZ4wHnd79BjwO KSVRz6944WR3E4FiE+/exrT3PR
E+1b1azVo4L/KIMPimIMD4xSnE4RXN0X1tVKqKZiHegQUm8jutb75ebmZpXGkV cpqbzv0EbI7/2h
XnEGXYSSeqIhHIL9wIQurUiKIg1w4H+Cbg8+23biDPqSwK/YJx0fnPWRtbxoeMk6G6QSUlSnamUc
UKG7r/Wc2CrZdkx23h9gO7PyxO1k+IEgApYYa6QY0cQMF6wUyrmxRijM BquGJMSMG3oXDuZEm2OK
DSuWsZUNTGMzhhyldBojpH0MoE6bMcIDhYHm4S0abx+DBRGTVx BxhVFmcNLEShAPXKcWHhu2w0Ga
qLeHxD76+hCmV9z2OkFxPx1AVGPJw9TGQ2TmIYTaZ4hoPHMl+H J24cFxxdibMS9rTegLxG6PvDzD
CeTpvWe2aOMeMiU9ZH+A/Q+YfZsal+putqQJgVUZ+Floz5h4sqnQCJZ7ONlrrTnMUZjSK3N CTaBL
Y54jSq7rkhh29fzKbDfrOVqCsngBLUd5ch3Y8jZHywBuAY3kKL syR0shkjDK0SJcej2MYSOaw4X5
iLaoafLtO7QdLkpgbwyowZ7oOBoGBUeD1W4sDqqNhkGvp5BaqU k8q9EknlXnKYBhZBLPKjKJZ7UY
DdFlg4H/acB02qGe80lAwzZ1TDumHdOOace0Y9ox7Zh2TDumHdOOace0Y9 ox/S8wfRv4h4bVx6Ll
XSfkoTU5h92msNda+qZHF2xqwtwC7/ihd5JsLPepC2M4ih0vrCTaZu5ejp9tmxA6gm3RNCHaeQcd
GBoQrf0AT/ATOoBPsAFpgrwyxRfg6sBfRF3lE9Qw/gZUcoka4udgLRd/I9nkP4Z+NfWKhsmP/poG
vngmd0nazlPNjjd6bcGsl6eyfErHpRm1poX0HY3mte3Kc9WfrQ 46VZy1p4ZXXHb++sHf3Juma70a
WMdAItN4/Li12cxC7fegLUyNq7miDUKeeTN4YcPuThBS96YTFZ+2fQx8qTr d7Ncff/PeUc+k2RW0
9oap80H+pKq64a3OqXq7RljnVh8UH+BP58S9Las9IUsh9Vmhao ARn8ejRMGMYt3cU+xLpRo9uc18
r7+Uk83x0vX/cBCtTG73+nxqS1Xz2RmFpqfU/M7aZQD+0QxAjl9JVPfD42t+4jm6Hd2Obke3o9vR
7eh2dDu6Hd2Obke3o9vR7eh2dDu6Hd2O7reciqxVyRrR3QN7Uj WVzguwqi4n2YB9qVg32O2LelFm
b3dbte/uWKOpb/jvfUp4MBbtadO/J7fgvHgZy1wOQ/X5e3x0fPvu8hv0u2O1zl0kJIqG/MVONDb9
8DSWcV40vWtMX+gkqJA7dWdHdGRS+o9/ASJFdOM=

[pos]

Many on-axis measurements of the original M2 show this phenomenon.
eg:
http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=380146&viewfull=1#post380146
http://www.audioheritage.org/vbulletin/showthread.php?35538-New-JBL-M2&p=360555&viewfull=1#post360555

I did not have the chance to do extensive measurements myself yet.

I had the opportunity the make some additional measurements today.

The original M2 spinorama shows a rising on-axis response above 7kHz, resulting in a flat response when averaged in the listening window :
71353

Based on all the published measurements (eg the links above) it appears that the on axis response of the current production unit is not rising that way.
This spinorama must have been taken on a prototype unit, and a more "reasonable" EQ must has been chosen on the final production unit.

In essence, the on-axis response is identical up to around 10kHz, and "rolls off" to flat above that.
This results in the aforementioned bump in the 8kHz-10kHz area, and an averaged response in the listening window that will be flat up to 10kHz and roll off above that.

Today's measurements:
71354

[bubbleboy76]

Interesting. Thanks.
What is your end goal pos, is it a flat listening-window-average, or this kind of curve you have now?
Or will you stick a UHF-driver on it?

[bubbleboy76]

The official LSR305 / LSR308 measurements also has the rising on-axis response to get the listening-window straight. I wonder if that is the thruth for them, or if that also were changed later.
Maybe I will have to pull out the old measurement-stuff again... :)

[pos]

Interesting. Thanks.
What is your end goal pos, is it a flat listening-window-average, or this kind of curve you have now?
Or will you stick a UHF-driver on it?
I will not second guess JBL (anechoic chamber, knowledge, listening tests) and stick with the current target curve, even if I try different compression drivers.
I might try to add a super tweeter though, but this is far down in the todo list.

I might try to address that dip at ~6kHz though, as this will be easy to precisely measure.
I also want to play with the option of linearizing the phase, as I am working with FIR filters.

[bubbleboy76]

Sounds wise. Will be very fun to follow!
How is the phase response now, pretty good ?

[pos]

It is pretty much text book for the ~800Hz LR 36dB/oct crossover, and the bass reflex.

[johanwholst]

It is pretty much text book for the ~800Hz LR 36dB/oct crossover, and the bass reflex.

To me it seems that the crossover slope is LR 48/dB acoustic?

[pos]

Hi Johan,
Not according to my measurements, and I think it was also specified by JBL.

[johanwholst]

But would not a 6th order LR result in a 180 degree phase flip? I cannot see that either woofer or D2 has a reversed polarity in the original setup

[Ian Mackenzie]

They might do the phase reversal at the input terminals.

[srm51555]

I had the opportunity the make some additional measurements today.
In essence, the on-axis response is identical up to around 10kHz, and "rolls off" to flat above that.
This results in the aforementioned bump in the 8kHz-10kHz area, and an averaged response in the listening window that will be flat up to 10kHz and roll off above that.


Thanks for your measurements. Does JBL put the bump at the 8kHz - 10kHz region more for off axis listening improvement? It does look like a bump in the 6kHz-7kHz could help.


They might do the phase reversal at the input terminals.

Do you see any harm in trying this. I wanted to, but wasn't sure if it would be safe.

[sebackman]

Hi POS,

Can you please upload a clean measurement (no dsp, no smoothing) of the D2 on the M2 waveguide?

I did send you the files with 2450SL and 2451Be on M2 a while back and it would be very interesting to see how D2 on M2 deviates from them.

That would give a good basis to try to figure out what changes are needed to the original JBL M2 DSP settings to get reasonable similar results with a different driver then D2.

Kind regards
//RoB

[johanwholst]

Looking good



I also look forward to your thoughts on this combination in comparison to the D2

Did note have time before today to rough-tune 2450sl/be in the M2 waveguide. Well, it took about 10 seconds to conclude that 2450sl with truextent to my ears completely parks D2

71409

[srm51555]

Did note have time before today to rough-tune 2450sl/be in the M2 waveguide. Well, it took about 10 seconds to conclude that 2450sl with truextent to my ears completely parks D2

Interesting, thanks for sharing. What do you like better about it vs the D2, and what is your final amp/DSP choice?

thanks,
scott

[johanwholst]

Remember, this is highly subjective. While D2 measures and sound sweet, it does not give me the same "presence" as 2450Be. 2450 gave me goosebumps straight away, while I have been working quite a bit with D2 without giving me quite the same feeling. And that good feeling is what we are looking for with our systems is it not?

I have not landed on a dsp solution yet. Currently using Hypex DLCP, but it will be applied in a different system after the summer.
For amps I have a dual mono Aleph J on the compression driver, and a Crown cts600 on 2216. A better cabinet is still in process, but getting there eventually!

[1audiohack]

Remember, this is highly subjective. While D2 measures and sound sweet, it does not give me the same "presence" as 2450Be...

Inhad the exact same experience with the exact same drivers. :)

Barry.

[1audiohack]

They might do the phase reversal at the input terminals.

I checked this out just now.

The wire from the terminal cup connected to the negative / black "HF In" terminal has tracer print and goes to the common trace on the board. This common section on the board is labeled negative in and negative out. The tracer print on the wires coming off the board "Out" now have the tracer print on the positive wire and this wire connects via the small fast-on to the front diaphragm positive terminal of the D2 driver.

So,, it looks like the polarity stays positive.

If I have time over the weekend I will hit one on the plane wave tube with the network in line and make sure. I want to do this to measure the effect of the network anyway.

Barry.

[srm51555]

Thank you for the confirmation!

[4313B]

Did note have time before today to rough-tune 2450sl/be in the M2 waveguide. Well, it took about 10 seconds to conclude that 2450sl with truextent to my ears completely parks D2When the D2 was first introduced it had a parts price of $1,499 and a finished goods price of $1,999. The new, and correct, price point puts the transducer in a completely different perspective. Your comparison isn't too much different than the comparison between the 435 and 476, although even the 435 is more expensive than the D2.

The really good part though is just how damn good the D2 turns out in the M2. Basically, folks that own the M2 will very probably never care about the better compression drivers. No one need be the least bit embarrassed about the D2 in the M2. :) Were you to tell a "normal" person that there are better sounding compression drivers on the planet after having just completely blown their socks off with an M2 audition they would just look at you with a blank, incomprehensible stare. ;)

[johanwholst]

:) Were you to tell a "normal" person that there are better sounding compression drivers on the planet after having just completely blown their socks off with an M2 audition they would just look at you with a blank, incomprehensible stare. ;)

Good one :D

No, the combo D2/M2 is truly spectacular, but I'm a diy'er. I love pulling things apart and mixing bits and bobs, and have long departed the world of normal people when it comes to speakers. And by the way, how many "normal" people frequent these forums ;) ?

To me it seems that a lot of the magic lies in the waveguide. This is good news for fellow homebrewers now that it seems that D2 is harder to get hold of for those without JBL pro contacts...
It will of course no longer be a M2 clone, but still based on the principle as the original, and most likely a superb speaker if used a suitable compression driver

[4313B]

Agreed :)

And I think it is fantastic that the Truextent and the 2450 are available.

[johanwholst]

Agreed :)

And I think it is fantastic that the Truextent and the 2450 are available.

I see the irony.... and point taken.

[SMT]

I see the irony.... and point taken.

so what is a girl to do? Radian 950?

[ivica]

Agreed :)

And I think it is fantastic that the Truextent and the 2450 are available.

Hi 4313B,
May be I miss something, I can imagine to compare D2430k &M2 with 2450Be (Trx)&M2, up to 10kHz, but over that region I would expect that D2 woul be superior. I have not meausure myself any of them in the M2 combo, just looking from the presented data.
I wonder what would be 2450 (2441Al dia)&M2 compared to D2&M2 combo...
Regards
Ivica

[johanwholst]

so what is a girl to do? Radian 950?

If you are in no rush, I am sure that you'll find D2430k on the secondhand market.
Ebay will probably be flooded now after the recent discovery that there are better sounding compression drivers out there :D

Ivica: Sorry for not publishing measurements, but I do not completely trust my behringer microphone above 10k, but after quick measurement and adjusting compensation for 2450sl/be in M2 wg, it seems that it comparable to d2430k in output to 16k where it dives. Perceived HF is to my ears the same.

[4313B]

Hi 4313B,
May be I miss somethingAll I am saying is that I am glad people are finding what they consider to be viable alternatives to the D2430K. Other compression drivers will very probably require different compensation but it shouldn't be too difficult for them to dial in whatever their choice ends up being.

When the D2430K was in the same price range as the other top of the line Pro compression drivers I was mystified. Now that they are priced at around $300 to $400 I think they are an absolutely fantastic bang for the buck. Like I said to GT, I am so glad I didn't purchase a pair for three grand when they first came out and his response was "No kidding!"

[ivica]

If you are in no rush, I am sure that you'll find D2430k on the secondhand market.
Ebay will probably be flooded now after the recent discovery that there are better sounding compression drivers out there :D

Ivica: Sorry for not publishing measurements, but I do not completely trust my behringer microphone above 10k, but after quick measurement and adjusting compensation for 2450sl/be in M2 wg, it seems that it comparable to d2430k in output to 16k where it dives. Perceived HF is to my ears the same.

Hi johanwhost,

Usually we can see too smothed drivers response, and a kind of ringing can be seen if higher resolution measurements have been done.As an example can be seen large difference between 2446/50/51 vs 2441Al or even 2445, not to mention SL differences. Using Be (Trx), not JBL (476Be), quite sharp roll off over 10kHz can be seen.
I would expect that D2430k would have more smoother response as it is ring radiator diaphragms shapes, but may be I am wrong, as there are two diaphradms operating together, so a kind of cancelation can happen., but may be I am wrong. It would be nice if the response without smoothing would show that there is no needs for UHF driver, especially, concerning its price, almost as 2405 alone.

I can imagine that 4313B's 476BE are very respectve drivers , not to mention the price, and if He confirm that acoustical difference is not so emphasized, I beleve that D2430K would become acceptable alternative.
Regards
Ivica

[johanwholst]

Hi Ivica
D2430k is more than an alternative. Even for the most stubborn diy'er it's admittably superb.
It was the general sound and X factor of 2450sl/be I preferred over D2. This is very subjective, but hope to inspire others building M2 clones to at least try out their expensive paperweights before they settle on D2

Anyways... finished some finishing on the baffle today. Rubber lip and port flare is countersunk, and mounting hole for WG drilled for one, and marked for the other.

71425

Surprisingly strange measurements. Did not really make sense in either imperial or metric, but I got it to fit eventually.

Strangely it seems like all components fit, so the only thing that remains is tapping mounting holes I'm the WG, glueing, install speak on, damping and finishing!

71426

Only mistake so far was making the hole for the WG too big. Needs to do something creative to supports the two lower bolts. I'm sure more mistakes will follow, but so far I'm quite optimistic that they will play music in june

[srm51555]

Great progress Johan!

Those items in the background of photo two look pretty awesome as well.

[johanwholst]

Great progress Johan!

Those items in the background of photo two look pretty awesome as well.

Thanks! I really need some cheering as this project progress slower than I want to... Eager to hear 2216nd in a more correct cabinet than the one I'm using now.

[hlaari]

great job Johan!

I think at we will have great time listening to you M2 speakers when I will visit you in the late summer:)




Ari

[johanwholst]

great job Johan!

I think at we will have great time listening to you M2 speakers when I will visit you in the late summer:)




Ari

Most likely! I'll make sure we have a lot of fun stuff to play with

Looking forward to see you up here

[4313B]

Nice! :yes:

[sebackman]

Excellent work Johan. That will be some awsome speakers.

It would be interesting if you could post a un-smoothed curve from your differen drivers in the M2 WG.

And please keep the pictures over progress coming, theay are inpiration to us all.

Kind regards
//Rob

[ivica]

Thanks! I really need some cheering as this project progress slower than I want to... Eager to hear 2216nd in a more correct cabinet than the one I'm using now.

Hi johanwholst,

Very, veeeery nice work.
One question- where is baffle step in the lowre part of baffle under the bass driver. Here on the Forum there has been a lot of words about, talking about revolutionary upgrades round 500Hz after such improvement.
Wish You great success in your project
Ivica

[Kalle]

Has this been done DIY? It seems a little bit tricky to get the round shape. If so please provide pics. I have not desided how to do mine yet.

Regards
Karl


Hi johanwholst,

Very, veeeery nice work.
One question- where is baffle step in the lowre part of baffle under the bass driver. Here on the Forum there has been a lot of words about, talking about revolutionary upgrades round 500Hz after such improvement.
Wish You great success in your project
Ivica

[johanwholst]

Ivica and Kalle
I tried to add a 16mm piece with routed edges to the lower part.
It kind of messed up the looks, so I'll take my chances at those 500hz advantages and dropped it

It is always good to do some bad decisions to maintain the audiophile nevrosa. Keeps this hobby much more intresting ;)

Sebackman: I will try to do and publish some decent unsmoothed measurements of 2450be. It was a pain mounting them, so I will not swap back to D2 anytime soon.

[sebackman]

Here are some outdoor measurements I did. These are at zero degrees.

First is 2451J Ti
Second is 2450SL
Third is 2451H Be

All on exact same gear and waveguide.

Kind regards
//RoB

Test JBL 2450SL / 2451Ti / 2451Be / 2332 / VTX F12 / M2

Outdoor at Håkke, tripod, turnable to 0, 30, 60 and 90 degrees

SW LSPCad Pro 60 (latest update), HW M-Audio Fast Track Pro, Samson Servo 200 amp, Earthworks M30 calibrated mic, 33mf protection cap in series "Mundorf",
2-Channel measurement (delta), 48kHz, 512k buff, 65536 MLS, no smoothing, offset 71 cm, range 40db, window 10ms, ca 88db level

714557145371454

[johanwholst]

Excellent work Rob!
Is the measurement of 2451Be with M2 WG?
It looks very smooth. would need very little correction to reach 16k. Just a notch at 1500 and a shelving for a more or less flat response in its working range

[ivica]

Ivica and Kalle
I tried to add a 16mm piece with routed edges to the lower part.
It kind of messed up the looks, so I'll take my chances at those 500hz advantages and dropped it

It is always good to do some bad decisions to maintain the audiophile nevrosa. Keeps this hobby much more intresting ;)

Sebackman: I will try to do and publish some decent unsmoothed measurements of 2450be. It was a pain mounting them, so I will not swap back to D2 anytime soon.

Hi johanwholst,

No problem, I am only joking , as I do not believe that such 16mm larger part of back chamber would improve 500Hz response ( wave length about 0.7m). I believe that something else JBL have done in order to reduce a kind of cancellation or driver, box, ports, depth etc .. can be a reason... but it would be difficult to get real answers....
Your work is respectable , from ANY point of view

regards
ivica

[johanwholst]

One speaker glued up and the other in process.
Everything squares up perfectly after running all pieces trough the table saw today.

I used lamello biscuits for all joints witch makes life much more pleasant

71456

you can never own too many wise grips!

71457

It looks surprisingly tiny. (empty) beer bottle for comparison. Hope I got the dimensions right...

[Kalle]

Very nice indeed:) Are you going to make grilles for them?

Regards
Karl

[johanwholst]

Very nice indeed:) Are you going to make grilles for them?

Regards
Karl

No, I would probably never use them so it's not worth the effort

[4313B]

I did a quick shot of the 476Mg versus the D2430K on the M2 waveguide. I needed the impedance curves so I figured I'd collect some SPL curves at the same time.

[sebackman]

Hi 4313b,

From the text below the graph it looks like a very long time window Is that correct?

It also seems like Mg is falling off reasonably early and showing a similar pattern as the Be. That should be just fine with a DSP but given the difference betwee the drivers the correction file will need to be rather different.

Excellent info, thank you

Kind reargs
//RoB

[bubbleboy76]

I did a quick shot of the 476Mg versus the D2430K on the M2 waveguide. I needed the impedance curves so I figured I'd collect some SPL curves at the same time.

The off-axis curves would be very interesting to see, if you measured that?

[4313B]

Hi 4313b,

From the text below the graph it looks like a very long time window Is that correct?Right, I didn't gate the posted curves above nor did I measure them outside (raining) like I usually do. I didn't like how the gating affected the response around 500 to 1kHz. Usually I use tail correction in LEAP instead. For example, in this instance I would use tail correction below approximately 300 to 400 Hz.

I'll do the SPL curves that I will end up using outside some night soon. It appears that the 476Mg won't require nearly as much compensation on the top end, just like GT theorized.


That should be just fine with a DSP but given the difference between the drivers the correction file will need to be rather different.Yep and that is the main thing one can take away from this quick set of graphs, the compensation filter for both drivers would be quite different. :)


The off-axis curves would be very interesting to see, if you measured that?Yeah, I suppose I could mark off a spot at 30 degrees off axis.

[grumpy]

Sorry to be a dolt... (&thanks for the plots):
Mg is green?
Less compensation meaning less complicated vs D2?
(or have I got this upside down).

[pos]

D2430k must be the green curve.

For comparison here is, with the same scale, the inverse of the EQ applied by the crown and passive network to make the D2430k flat (on average in the listening window).
This should be a fair representation of the natural response of the D2430K on the M2 waveguide.

71542

[pos]

Did note have time before today to rough-tune 2450sl/be in the M2 waveguide. Well, it took about 10 seconds to conclude that 2450sl with truextent to my ears completely parks D2

71409
Nice!
I am eager to try mine, but given the difficulty in swapping these, this is not going to happen right now.
I like the way you cut the walls of the waveguide mounting part to make the nuts easier to reach.

[johanwholst]

Nice!
I am eager to try mine, but given the difficulty in swapping these, this is not going to happen right now.
I like the way you cut the walls of the waveguide mounting part to make the nuts easier to reach.

You got a keen eye Thomas! It was actually done by forum member hlaari. Without it mounting would be utter pain. Now it is just fiddly :)

One question: I'm about to mount the WG to the baffle.

Two options: Tap the plastic with m5 and use bolts, or glue threaded rod in the hole?

I believe the plastic for flange mounting strong enough for supporting 2450sl so I will not brace the compression driver. Crazy?

Another thing: My wife waits eagerly to see me mounting the waveguide from the back. She this it's going to be quite entertaining with me halfway through the baffle hole and a lot of x rated language.
Kind of regret I did not build an access hatch on the back...

[pos]

Without it mounting would be utter pain. Now it is just fiddly :)
It is painful indeed, especially when the nut gets magnetized... :bomb:

The easiest way I found is to maintain a distance between the driver and the waveguide so that the threaded rod only exceed a tiny bit over the adapter.
That way you only have to get the nut above the hole and gently turn it while it stays nicely flat...
Still cumbersome, to say the least.


Two options: Tap the plastic with m5 and use bolts, or glue threaded rod in the hole?
I did a mix of the above: I used M6 threaded rods for mounting the waveguide to some metal brackets (no real baffle for now) with wing nuts.
I drilled the hols with a 5mm drill, but it is probably not necessary (Rob did not for example) as the holes are already 4.7mm.
Wing nuts are a good option if access is difficult.

[4313B]

D2430k must be the green curve.Yes. I am not liking the looks of the 476Mg. I played around with the data - gating, smoothing, etc and the D2430K looks fine, 476Mg not so much.

I'll measure the other 476Mg at the same time I redo the measurements outside and determine if they need to be opened up for inspection.


Sorry to be a dolt... (&thanks for the plots):
Mg is green?
Less compensation meaning less complicated vs D2?
(or have I got this upside down).I forgot to post which was which. D2430K is green. I wasn't all that excited about the results anyway. I primarily just needed the impedance curves for the time being and shot the SPL curves just because (in the living room on the floor, waveguides face up towards the ceiling).

[srm51555]

Kind of regret I did not build an access hatch on the back...

I was thinking the same thing before I mounted mine. For me, I am glad I did it this way, mounting them wasn't really that bad. Finding the correct hole spacing was much worse I thought .

Maybe she should screw them in since her hands are smaller. :)

[johanwholst]

Yes, the hole spacing proved difficult to measure properly is quite a bit off on mines so they are overzized... Blutack will seal it all up in the end

By the way, tapping for M5 direct went smoothly. Just finished it
Thanks for the tip on wing nuts Pos. that's what I will do

[pos]

Yes M5 is easy to drill as you are supposed to drill a 4.2mm hole and the existing holes are 4.7mm IIRC.
That means that the grip will not be as good as the fillet will not be as deep as it is supposed to.
As long as you don't pull perpendicularly to the waveguide plan everything should be fine :P

I went for M6 for the mounting holes, which calls for a 5mm pre drilling, and used M5 for mounting the drivers because I wanted to keep as much material as possible there.

[Robh3606]

Hello 4313b

Here is a passive compensation voltage drive for M2 waveguide with 476mg It looked pretty good with my pair. You have a issue with the drivers?? Simulated on axis with network and schematic.

Rob:)

[4313B]

Nice Rob! :yes:


You have a issue with the drivers??Yeah, I might have an issue with the 476Mg I measured. Hopefully I'll be able to check it in the next few days.

Did you use ideal inductors in your model or did you apply some DCR?

[Robh3606]

Hello 4313B

Ideal didn't use DCR in the model figured I would wait and just wait and measure the coils when I got them and adjust as needed if there was a significant change.

Rob:)

[srm51555]

There is actually a very simple way to measure system/cabinet resonance with a minimum of SW & HW. If you can connect your computer to your preamp / power amp and play music from the computer you can do this.



Rob, Thomas, and friends,

I finally took a cabinet resonance measurement last night and found the cabinet looks to be tuned to 27hz +/- 0.5hz. Cabinet size and port information can be found in post 35 (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=384253&viewfull=1#post384253).

For those who want to try this also, I initially used my Crown dci that has DSP built in and didn't receive a accurate measurement so I pulled out an A/V receiver and received more accurate results. I used an free download of signal generator POS recommended for my iPhone and a 50ohm resistor. Never realized taking this measurement was this easy.

Thanks,
Scott

[4313B]

I posted this in the M2 thread.

Using a volume of 5.2 cubic feet, a tuning frequency of 27hz, port diameter of 3” and the number of ports needed set at 2 using, the precision port calculator recommends this port http://www.parts-express.com/precisi...-tube--268-368 (http://www.parts-express.com/precision-port-psp-3ofh-3-outside-flare-for-port-tube--268-368) (and it's inner mate) to be set with a total length of 8.85.


Rob, Thomas, and friends,

I finally took a cabinet resonance measurement last night and found the cabinet looks to be tuned to 27hz +/- 0.5hz. Cabinet size and port information can be found in post 35 (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=384253&viewfull=1#post384253).

For those who want to try this also, I initially used my Crown dci that has DSP built in and didn't receive a accurate measurement so I pulled out an A/V receiver and received more accurate results. I used an free download of signal generator POS recommended for my iPhone and a 50ohm resistor. Never realized taking this measurement was this easy.

Thanks,
ScottNice!

And it looks like you guys figured out two 16 uF capacitors in series for the biased version of the network.

[pos]

And it looks like you guys figured out two 16 uF capacitors in series for the biased version of the network.

SCR/Solen do have a 16uF cap in their catalogue, but I did use the same unbiased WIMA caps as in the original network because I wanted to have something as close as possible to the original, and in the end I will probably either remove most of that network from the signal path, or use another compression driver...

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

[srm51555]

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

This would be my case. I thought that doubling the value and doubling quantity was good on all capacitors in a network. Electronically, It should be the same as the original network or is this incorrect?

[4313B]

SCR/Solen do have a 16uF cap in their catalogue, but I did use the same unbiased WIMA caps as in the original network because I wanted to have something as close as possible to the original, and in the end I will probably either remove most of that network from the signal path, or use another compression driver...

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

I will probably use a modified version of the biased 4367 network should I decide to follow through with the LCR plan.

[pos]

This would be my case. I thought that doubling the value and doubling quantity was good on all capacitors in a network. Electronically, It should be the same as the original network or is this incorrect?
Yes Two 16uF in series will be equivalent to a single 8uF cap.
The question is does a 9V battery provide enough bias to get a benefit at normal listening levels here?
It probably depends on what you call "normal" :D

[johanwholst]

I know it has been mentioned before, but when test mounting the waveguide today, I noticed that it is not flat. Seems like it is slightly curved and does not touch the baffle in upper left corner.
I have not bolted it down yet, and maybe it gets pulled straight.

What say you who have completed their builds with M2 parts?

[dprice]

I used gasket tape to seal between the waveguide and baffle. Not sure if the waveguide was flat or not since the cabinet frame hides that detail.

A little more info here...

http://www.audioheritage.org/vbulletin/showthread.php?37771-Another-DIY-M2-thread

Good luck!

[4313B]

Hello 4313B

Ideal didn't use DCR in the model figured I would wait and just wait and measure the coils when I got them and adjust as needed if there was a significant change.

Rob:)I entered your network into LEAP along with my data and it came out great. Gotta love that top end from the Mg. :) Thank you for reposting this information!

[johanwholst]

Little update:
Glued up both cabinets this week, and cut thread for WG mounting.
I cut it using M5 and fastened with threaded rod and wing nuts. Fits perfectly, and the slight curve in the waveguide straightens out when thighen it slightly down.

Now remains sanding, priming and finishing. They will be playing music in a week!

71590

[pos]

Yum http://www.tenerifeforum.org/tenerife-forum/images/smilies/tenerife-forum-yum-smiley.gif

[4313B]

They should sound fantastic! :)

[johanwholst]

I believe so too! The whole construction just seems to look right.
Now it's just a matter of not rushing things in the end and put good effort in finishing, damping and sealing of waveguide.

[Robh3606]

I entered your network into LEAP along with my data and it came out great. Gotta love that top end from the Mg. :) Thank you for reposting this information!

Hello 4313B

That's great! Thanks for letting me know I am on the right track. Yeah you sure do have to like that top end!

Rob:)

[srm51555]

Nice progress Johan

[ivica]

Hello 4313B

That's great! Thanks for letting me know I am on the right track. Yeah you sure do have to like that top end!

Rob:)

Hi,
Is there any difference between 467Mg and 476Be in the FR.
Regards
Ivica

[bubbleboy76]

Hi,
Is there any difference between 467Mg and 476Be in the FR.
Regards
Ivica

Take a look for your self here:
http://www.audioheritage.org/vbulletin/forumdisplay.php?59-Transducer-Information

[ivica]

Take a look for your self here:
http://www.audioheritage.org/vbulletin/forumdisplay.php?59-Transducer-Information

Hi,
It would be difficult to conclude which one is more pleasant for listening, it seems to me that Be is less intrusive...????
may be some driver&horn interaction and more resolute measurements would show more differences.....

ivica

[johanwholst]

Did not feel for veneering (chickened out...) and ended up painting with Ral 7039, my favorite DIY speaker color. Neutral and quite boring, but will be rather unobtrusive when placed up into the living room.

Test fitted ports, horn and woofer. Remains to dampen, cut and mount ports, install threaded inserts for feet and speakon

71711

[pos]

:thmbsup:

[srm51555]

Did not feel for veneering (chickened out...) and ended up painting with Ral 7039, my favorite DIY speaker color. Neutral and quite boring, but will be rather unobtrusive when placed up into the living room.



Looks good Johan!

[johanwholst]

Thanks guys! I'm waiting impatiently on the last parts, but hope to tune them this weekend.

Pos or others; what port lenght including inner and outer flare would you start with?
I'm using jetset with internal 70mm

Srm: how is your build coming along?

Johan

[pos]

Pos or others; what port lenght including inner and outer flare would you start with?
I'm using jetset with internal 70mm

I will measure mine when I get the time, but I think my enclosures are smaller than intended so this might not translate to anything usable for you.
I used the online precision port calculator, and I cut them a little bit longer to have room for adjustment.

[srm51555]

Srm: how is your build coming along?


After sound starting piping out I haven't got much progress done. I still need to work on the front baffle a bit to get the woofer flush and I'm having trouble deciding how I'm going to get the top of the horn flush to the top of the cabinet as shown here (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=379912&viewfull=1#post379912). I'm also going to look into charge coupling like 4313b has suggested Mr. Timbers used in the 4367 instead for the traditional resistor method since Thomas has explained how my current setup probably isn't fully charged as it sits.

But before all of that, learning how to use Room EQ Wizard has been my main goal. Unfortunately the threads on that subject are massive and a bit overwhelming when reading an hour before going to bed.

Thanks,
Scott

[hlaari]

Did not feel for veneering (chickened out...) and ended up painting with Ral 7039, my favorite DIY speaker color. Neutral and quite boring, but will be rather unobtrusive when placed up into the living room.

Test fitted ports, horn and woofer. Remains to dampen, cut and mount ports, install threaded inserts for feet and speakon

71711


They look very good Johan:D



Ari

[johanwholst]

After sound starting piping out I haven't got much progress done. I still need to work on the front baffle a bit to get the woofer flush and I'm having trouble deciding how I'm going to get the top of the horn flush to the top of the cabinet as shown here (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=379912&viewfull=1#post379912). I'm also going to look into charge coupling like 4313b has suggested Mr. Timbers used in the 4367 instead for the traditional resistor method since Thomas has explained how my current setup probably isn't fully charged as it sits.

But before all of that, learning how to use Room EQ Wizard has been my main goal. Unfortunately the threads on that subject are massive and a bit overwhelming when reading an hour before going to bed.

Thanks,
Scott

Scott: I have used REW quite a bit. Feel free to send me a PM if you have any questions. I think I have a basic tutorial somewhere I can send you.

[srm51555]

Scott: I have used REW quite a bit. Feel free to send me a PM if you have any questions. I think I have a basic tutorial somewhere I can send you.

Awesome, PM sent

[pos]

I'm also going to look into charge coupling like 4313b has suggested Mr. Timbers used in the 4367 instead for the traditional resistor method since Thomas has explained how my current setup probably isn't fully charged as it sits.
This was a purely theoretical calculation, and considering my very limited experience with charge-coupled network you should probably take what I said with a grain of salt :D
I don't know if biasing the caps using the voltage seen by the woofer will brings you anything more than 9V though?
Why not start with using more than 9V in your current setup with say another battery, and see what happens?

[Dave M]

Congrats on the new speakers! Looks awesome. I also would like to thank you for sharing your impression about D2 vs 2450Be. I couldn't decide whether I should put Be into my 2450SL or buy D2. I understand that it is your subjective opinion, but since I also use multiple Aleph J's driving JBL, I'm pretty sure that we share the similar taste. :)


Remember, this is highly subjective. While D2 measures and sound sweet, it does not give me the same "presence" as 2450Be. 2450 gave me goosebumps straight away, while I have been working quite a bit with D2 without giving me quite the same feeling. And that good feeling is what we are looking for with our systems is it not?

I have not landed on a dsp solution yet. Currently using Hypex DLCP, but it will be applied in a different system after the summer.
For amps I have a dual mono Aleph J on the compression driver, and a Crown cts600 on 2216. A better cabinet is still in process, but getting there eventually!

[johanwholst]

Congrats on the new speakers! Looks awesome. I also would like to thank you for sharing your impression about D2 vs 2450Be. I couldn't decide whether I should put Be into my 2450SL or buy D2. I understand that it is your subjective opinion, but since I also use multiple Aleph J's driving JBL, I'm pretty sure that we share the similar taste. :)

Thanks!
M2 WG, aleph J and 2450sl/be is a sweet sounding combination. But it is no longer a clone witch is probably the goal of many others. Personally I like to venture away from the original concept, and enjoy the challenge of tuning EQ and experimenting to get my own sound.

Are you planning a build?

[Dave M]

Thanks!
M2 WG, aleph J and 2450sl/be is a sweet sounding combination. But it is no longer a clone witch is probably the goal of many others. Personally I like to venture away from the original concept, and enjoy the challenge of tuning EQ and experimenting to get my own sound.
Are you planning a build?

Welcome!

Currently no plan to build an M2 clone, since I just have finished my DMS-1 project. I love the sound of 2450SL (DMS-1), but my endless greediness keeps asking me if there would be any possible upgrade. :D

I'm planning another project similar to M2, but it would not be an M2 1:1 clone, because my goal of this project is the same as yours. Today's affordable but excellent digital crossover / measurement technology encourages me to venture my own speaker design, which is based on proven professional monitor speaker design like M2. :)

[johanwholst]

I'm in the process of stuffing my cabinets with Rockwool with 30kg/m2 density. awful job...

Any comments about recommended thickness? i will cover five sides of the cabinet and leave baffle undamped

[srm51555]

I'm in the process of stuffing my cabinets with Rockwool with 30kg/m2 density. awful job...

Any comments about recommended thickness? i will cover five sides of the cabinet and leave baffle undamped

I used a one inch thickness when I did mine. I was told this was the standard JBL thickness.


Thanks,
Scott

[srm51555]

I will probably use a modified version of the biased 4367 network should I decide to follow through with the LCR plan.

Does anyone how close this network is to being a drop in to the M2? I know both use the same D2 and the 2216nd's are somewhat similar, but I don't want to assume it would be a lock because of the differences in 2216's and the waveguide. I went back to read the post Mr Timbers gave on the 4367 (http://www.audioheritage.org/vbulletin/showthread.php?37662-JBL-4367-first-listen&p=386898&viewfull=1#post386898) and originally missed this statement about passive systems and I got to thinking about building a pair.


Also keep in mind that the M2 is full active. It has separate amplifiers, electronic and digital crossovers and a lot of EQ bands. All kinds of things large and small can be fixed with that kind of horsepower. The pure passive systems can only have a little shaping and perhaps a few low Q correction filters. In spite of that, there is often a musicality to passive systems that purely electronic ones just can't match.

[hum4god]

hi
i will receive a pair of jbl D2430k drivers soon and am looking for a pair of M2 horn lenses and adapters.
could anybody point me to where i can get them aside from speakerex ?
any help is appreciated.
malcolm

[johanwholst]

hi
i will receive a pair of jbl D2430k drivers soon and am looking for a pair of M2 horn lenses and adapters.
could anybody point me to where i can get them aside from speakerex ?
any help is appreciated.
malcolm

Pro Sound Service maybe?

[johanwholst]

At last my "M2" play music. Did not expect the details to take that long... building cabinets was easy, but the rest took forever. Sourced black bolts for woofers and ports, gaskets for WG, and damped with 25mm Rockwool sprayed with hairspray. They smell like an old woman, but I'm getting used to it.
Ended up cutting the port tubes at 20cm, and the -6dB point with EQ seems to be at 20-25hz in my room. Remains to fine tune but they seem to give me terrific low end response.
Soundstage and imaging is miles above my former mockup speakers. Probably because of the elevated 2216 and proximity between the WG and 15"
I could not be more pleased, and looking forward to optimize 2450be in the WG when the weather stops being so nice
Thanks for the contributions in this thread!

71999

[pos]

Congrats!
It looks like you managed to reduce C-C distance compared to the original!

[srm51555]

Good Job Johan and Congrats on getting them all done!!

[johanwholst]

Thanks guys!

Took a quick and dirty on axis measurement of 2450SL with Be.
Smoothing is 1/48. No EQ apart from 56uf cap and a 2 order HP at 500hz

Cant complain about the M2 waveguide...

72007

[johanwholst]

Listening postition measurement. 1/12 smoothing. Original EQ on 2216nd with a notch at my room mode at 30hz. Self composed and very moderate EQ on 2450

72008

[ivica]

Thanks guys!

Took a quick and dirty on axis measurement of 2450SL with Be.
Smoothing is 1/48. No EQ apart from 56uf cap and a 2 order HP at 500hz

Cant complain about the M2 waveguide...

72007

HI JOHANWHOLST,
up to 10kHz good, but over 10kHz about +12dB/oct has to be EQed, I believe that AL 2441 woul be better solution, not to mention original JBL 476Be or 476Mg diaphragm, but concerning the price D2430k seems to be economic solution..
Regards
Ivica

[johanwholst]

Yes they need extensive compensation in the HF, but seem to be free of any breakups and sound smooth all the way up after EQ. I have plenty of headroom due to gain structure and final compensation is not much more than with d2430k. I use a lot less EQ below 10k as well.

They paint a huge picture and are very enjoyable to the ears..

Wonder what happens at approx 800hz through... the dip is not correctable.

[sebackman]

Dear all,

They indeed look good in Grey, johanwholst. Job well done! :applaud:

I almost wished I had gone that route as oposed to tame the beast on my own.... :eek:

Some gasoline on the fire....

:dead_horse:

Haveing tested the different drivers I still like the 2450SL's with 475Nd diaphragms better than the rest, including my Be's.... At least to my ears. However my HT will be Be's as I already have made the investment...:crying:

Keep up the good job and more pictures please.

As a byline, I don't thing the resistor value matter that much in the CC networks. The current needed to energize the cap's is really small and it may take a few more seconds to build voltage but that should not really matter for SQ.

It would be really easy to set up a test on the topic, if of interest. Just connect the desired CC network to a battery and measure the rise time of voltage over the cap's with different resistors. The voltage rise shows that the cap's are charging as desired.

Kind regards
//RoB

[4313B]

Does anyone how close this network is to being a drop in to the M2? I know both use the same D2 and the 2216nd's are somewhat similar, but I don't want to assume it would be a lock because of the differences in 2216's and the waveguide. I went back to read the post Mr Timbers gave on the 4367 (http://www.audioheritage.org/vbulletin/showthread.php?37662-JBL-4367-first-listen&p=386898&viewfull=1#post386898) and originally missed this statement about passive systems and I got to thinking about building a pair.The quick "fix" is to:
1. Change R9 from 3.6 ohms to something like 10 ohms. This props up the response in the 1k to 2k region.
2. Add a 30 ohm rheostat ala 4430 right before C7 and set it to something around 20 ohms and viola! flat as a frozen pond. We can call it R10 ;) This affects the response on the top end, otherwise it would be too hot.
Basically you would play around with these two values along with the two switches to get it how you want it (I set the switches to C8 and R6 for example and that looked flat).

Once I get better response data there is a good chance that I will look at this again. If you really want to try it though just build a cheapie non-cc version and try it out (only if you have money to blow, you know, for the sake of science).

[srm51555]

The quick "fix" is to:
1. Change R9 from 3.6 ohms to something like 10 ohms. This props up the response in the 1k to 2k region.
2. Add a 30 ohm rheostat ala 4430 right before C7 and set it to something around 20 ohms and viola! flat as a frozen pond. We can call it R10 ;) This affects the response on the top end, otherwise it would be too hot.
Basically you would play around with these two values along with the two switches to get it how you want it (I set the switches to C8 and R6 for example and that looked flat).

Once I get better response data there is a good chance that I will look at this again. If you really want to try it though just build a cheapie non-cc version and try it out (only if you have money to blow, you know, for the sake of science).


Thanks for posting this, I have a couple of other things I need to shore up but would like try this.

[srm51555]

Since I started this project I wanted to try one of the large format drivers on my DIY M2. This requires a modification to the mounting plate so it would accept countersunk screws. I'm not a machinist but I wanted to document what I used just in the event someone else wants to do the same.

I started off by using a 90 degree, 1/2" counter sink bit attached to a cordless drill (In my case the drill was attached to a Flex Arm, but a standard drill will work). Use of aluminum cutting fluid is needed. I started off by adding couple of drops and adding more when necessary. When cutting the countersink the bit should moving slow and putting downward force on drill to put pressure on the bit is necessary. The plate was held down by a drill press vise.

I had a machinist buddy guide me with the above process. He also told me the drill press wasn't the best choice here because if you are not centered your countersink would be less than perfect.

I was able to pick up 2450SL's so the driver mounting holes didn't need attention. Bolts used were M6x1.0 35mm from Fastenal (http://cad.fastenal.com/item/socket-cap-screw/socket-cap-screw-metric/item-26068)

Hope this helps,
Scott

[grumpy]

Helpful info indeed, esp. the hardware info.

My own choice (given what I have) would be to use the drill press,
accurately index/center the workpiece with a matched drill, then clamp,
swap bits, and have at it...perhaps more work than with a flex arm
(nice to have that available!), but a nice round/centered countersink
is more likely vs handheld.

Happy to hear it worked out. :thmbsup:

[srm51555]

I was looking over the low pass side of the 4376 network didn't see any nodes on the capacitor side after D1 so does that indicate C1-C4 all have the some connection point to D1 or is this a mistake? Thanks, Scott

72664

[grumpy]

All connected. Could have done it with two caps, but perhaps the design wasn't a standard value or the cap physical size was an issue. :dont-know:

[4313B]

GT used electrolytics for the larger values and put them in parallel with smaller Solen caps to achieve the correct total capacitance. It is a way to cut down on cost and size.

[Aaron]

I may be late to the party, but I finally did a thing!

http://i278.photobucket.com/albums/kk87/666csi/thangs/P1790320.jpg (http://s278.photobucket.com/user/666csi/media/thangs/P1790320.jpg.html)

http://i278.photobucket.com/albums/kk87/666csi/thangs/P1790319.jpg (http://s278.photobucket.com/user/666csi/media/thangs/P1790319.jpg.html)

I'm waiting for foam tape to seal the waveguides...can't wait to hear 'em!

[bubbleboy76]

I may be late to the party, but I finally did a thing!

http://i278.photobucket.com/albums/kk87/666csi/thangs/P1790320.jpg (http://s278.photobucket.com/user/666csi/media/thangs/P1790320.jpg.html)

http://i278.photobucket.com/albums/kk87/666csi/thangs/P1790319.jpg (http://s278.photobucket.com/user/666csi/media/thangs/P1790319.jpg.html)

I'm waiting for foam tape to seal the waveguides...can't wait to hear 'em!

Very nice looking :)

[srm51555]

Aaron,those look great!! I really like the contrast between the veneer and those silver feet.

[Aaron]

Oh darn, I knew I forgot something...veneer!
Oh well, perhaps this winter I'll get the top & sides covered in walnut.

But anyway, yes: the aluminum feet turned out better than I'd hoped.

[srm51555]

Yesterday I had the pleasure on meeting up with fellow Wisconsin member Aaron and he was kind enough to bring his Crown iTech 5000hd's. Given it was a weekday we weren't able to perform a single speaker mono test as recommended by Floyd Toole. Instead we did it old school and played a few songs, switched amplifiers, and then replayed the same set of songs after the amp switch. I must admit since these beauties were here in my listening room for a limited time only I requested to hear the 5000hd more. Plus I was very familiar with the dci already. With the exception of the power potential of the 5000hd, I didn't hear any difference between the two and feel the dci is an economical choice for home listening. Both delivered clean sound and plenty of power needed for me.

The dci used a EC-V for a volume control and the 5000hd was controlled by a Yamaha integrated amp.

Thanks,
Scott

[srm51555]

Below is a modified version of the 4367 network for use on the M2 system as instructed by 4313b here (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=392956&viewfull=1#post392956).

I have two remaining questions:
1) Can I use a pot and DMM to set S1's HF, I really don't want to fiddle around with all of the resistors if not needed.

2) How much modification would this network need for the 2450sl/be's. Same inductors but different resistor or cap values:dont-know:. I'd really like to try this combo out also one day.

Thanks,
Scott

72905

[kentj]

Below is a modified version of the 4367 network for use on the M2 system as instructed by 4313b here (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=392956&viewfull=1#post392956).

I have two remaining questions:
1) Can I use a pot and DMM to set S1's HF, I really don't want to fiddle around with all of the resistors if not needed.

2) How much modification would this network need for the 2450sl/be's. Same inductors but different resistor or cap values:dont-know:. I'd really like to try this combo out also one day.

Thanks,
Scott

72905

Not to spoil your plans, but the 2216nd and the 2216nd-1 seems to have quite different frequency responses, if you consider the voltage drive for the dsp filter of the LF section of the M2, and the voltage drive for the LF section of the 4367.

I'm betting most of this has to do with the aquaplas treatment for the 2216nd-1 - and that the passive LF filter also needs tweaking if you're using the 2216nd.

The second thing to mention, is that the M2 waveguide and the 4367 horn have quite a difference in depth, so the phase-tracking between drivers will not be the same.

[srm51555]

Unfortunately the passive crossover project was more than I had to spend on an experiment. I'd like to try using my 2450sl/be's on them next. Since my amp and DSP is one unit (Crown dci 4300N) I'll need to modify the existing network for an 8 ohm load in place of the 32 ohm D2430K. With R2 having a DCR of 11 ohms and the 32 ohm of the D2430K, that gives a parallel resistance of ~8 ohms. Does removing the 11 ohm resistor out of the circuit when the 8 ohm D2430K provided the some functionality as before with the 11 ohm and D2430K? I'd like to still have the "padding" as before so I don't hear the amp's noise when music is not playing.

Thanks,
Scott

[pos]

Hello Scott,

Assuming the same impedance and SPL/W curves as the D2430K, here are equivalent networks that should result in same high-pass frequency and overall sensitivity (ie noise) :


32 ohm driver ( 20 ohm load, 9dB attenuation): R1=13 (30W) ; R2=11 (10W) ; C=8
16 ohm driver ( 10 ohm load, 12dB attenuation): R1=7.5 (75W) ; R2=3.3 (20W) ; C=16
8 ohm driver ( 5 ohm load, 15dB attenuation): R1=4.1 (160W) ; R2=1.1 (30W) ; C=32
4 ohm driver (2.5 ohm load, 18dB attenuation): R1=2.2 (350W) ; R2=0.36 (40W) ; C=64

As you can see resistors rating go up like crazy...

Alternatively you can use an autoformer (like the ones found in cheap in-wall volume controls) to simply turn the 5 ohm load into a 20 ohm one and use the original passive network.
By the way, Truextent diaphragms also come in 16 ohm, and that is probably a better choice than 8 ohm in your situation.

[srm51555]

Hello Scott,

Assuming the same impedance and SPL/W curves as the D2430K, here are equivalent networks that should result in same high-pass frequency and overall sensitivity (ie noise) :


32 ohm driver ( 20 ohm load, 9dB attenuation): R1=13 (30W) ; R2=11 (10W) ; C=8
16 ohm driver ( 10 ohm load, 12dB attenuation): R1=7.5 (75W) ; R2=3.3 (20W) ; C=16
8 ohm driver ( 5 ohm load, 15dB attenuation): R1=4.1 (160W) ; R2=1.1 (30W) ; C=32
4 ohm driver (2.5 ohm load, 18dB attenuation): R1=2.2 (350W) ; R2=0.36 (40W) ; C=64

As you can see resistors rating go up like crazy...

Alternatively you can use an autoformer (like the ones found in cheap in-wall volume controls) to simply turn the 5 ohm load into a 20 ohm one and use the original passive network.
By the way, Truextent diaphragms also come in 16 ohm, and that is probably a better choice than 8 ohm in your situation.

Thanks Thomas! Those values do rise significantly. For the autoformer would I be choosing the tap to create the 20 ohm load with 9db of attenuation and then hooking up the 2450 on the other side of the windings or would it be installed someway different?

Thanks,
Scott

[pos]

You will need to put the autoformer between the driver and (unmodified) passive network.
Set it to -3dB to accomodate a 16 ohm driver, -6dB for a 8 ohm driver, and -9dB for a 4 ohm one.

[Flodstroem]

Hi POS,

If Vb=130 Lit, Fb=27Hz, with TWO vents Dia=76mm, then Lv=198mm, owing to BB6.

regards
ivica

Is this the original dimension of the M2 bass reflex port??? If not, where can I find it?

[dprice]

Is this the original dimension of the M" bass reflex port??? If not, where can I find it?

Not exactly. The M2 port is curved or tapered and is likely a custom JBL part. See post # 842 in this thread for a photo.

I believe POS was giving the dimensions for straight 3" port with flared ends...an "off the shelf" solution.

[srm51555]

Is this the original dimension of the M" bass reflex port??? If not, where can I find it?

Member Valentin posted some info here (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=375490&viewfull=1#post375490).

Still grateful that he took apart a $5K speaker for us.

Thanks,
Scott

[Flodstroem]

Thanks for the reply, that cleared things out. So an internal dimension of the M2 cabinet is 46 x 17" 3/4" x 11" and two ports that are 60-70 mm in diameter (smallest part) and having a length of 16 cm (6.3"). If counting with the multiplying factor from the white paper the length of a straight tube would be approx 1.2 times the 16 cm curved tube, approx 19 cm? (this is only for my own simulation with the 2216Nd and 2269H) :D

[Flodstroem]

Here is a couple of simulations done with 2216Nd compared with 2269H in an original dimension M2 cabinet
The weight/volume of the damping material used in the original M2 is however unknown for me so I have only used the same value for al my calculations shown in the calculation files.

If comparing the two simś I cant find any big difference only that the the 2269H show op a slightly better lower bass extension lower rms displacement including better group delay. So wheres the drawback for to use the 2269 instead of the 2216 besides the price........... :blink: ?7456874569

[bubbleboy76]

Here is a couple of simulations done with 2216Nd compared with 2269H in an original dimension M2 cabinet
The weight/volume of the damping material used in the original M2 is however unknown for me so I have only used the same value for al my calculations shown in the calculation files.

If comparing the two simś I cant find any big difference only that the the 2269H show op a slightly better lower bass extension lower rms displacement including better group delay. So wheres the drawback for to use the 2269 instead of the 2216 besides the price........... :blink: ?7456874569

What about directivity?
As I understood it, one of the key things in the design of the M2 is the matched directivity at crossover.

I do not think 2269h will sound good up to and beyond 800Hz, do you? It is not made for that purpose. In that case, why not use 2269H all the way up to 20KHZ instead? ;)

[Flodstroem]

I do not think 2269h will sound good up to and beyond 800Hz, do you? It is not made for that purpose.

Hmmm, I was looking at the specs of the ASB7118, thats why I decided to do some simś :blink: Also Im not sure the cabinet of the M2 has some negative limitations due to frequency response on the 2269 ?