Another DIY M2 thread

[dprice]

Tons of background and technical data for the M2 is available in the threads below. No need to review here.

http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor

http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread

I discovered the M2 components were available through Speaker Exchange over the Labor Day weekend and ordered up most of the parts. My original thought was to try a curved cabinet or something like the S4700 to avoid the blacked-out utilitarian M2 monitor look. The 4367 was released before I had a final plan....so it was a pretty easy call to borrow from the 4367 looks for my M2 box. A walnut veneer and black baffle was chosen based on member BMWCCA's beautiful monster monitors.

I decided to go plywood rather than MDF and my first step was build a frame to attach the panels to. Doing the bracing first is bassackwards but that is how I did it. I had lots of 3/4" and 1/2" plywood scrap in the shop so I used it. Lots of glue, dozens of 15 gauge finishing nails, and a few pocket screws and I had frame to work with.

69197

3/4" pine plywood was used for the inner baffle and the outer is 1/2" plywood. I used the 3" precision ports (Parts Express # 268-350) and mounted them backwards to minimize the visible flange. Outer diameter is 5.25" so I used a 4.25" hole and a 1/2' roundover bit to flush-mount the ports. 6919869199

A few steps later and we are here....69200

[dprice]

Mounted waveguide and used 1" fender washers to to cover the 1/2" holes the screws pass through. I used a double layer of 1/8" x 1/2" gasket tape (Parts Express # 260-542) around the perimeter of waveguide to eliminate concerns about sealing the screw holes. The gasket tape is much nicer to use than any of weatherstripping I have tried from the big box stores - it actually sticks where you want it to go. Lots of caulk and construction adhesive used to seal cabinet.

6920169202

With drivers and JBL Pro badge installed....used rosewood veneer rather than walnut to get a bit more exotic look. Duratex was used for a slightly textured finish as it helps hide the flaws caused by being a hack woodworker.

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[dprice]

Being bi-amped, I opted for Carol SJOOW 4-conductor 14 gauge power cable (audiophile zip cord?) with Neutrik Speakon (NL4MPR) round chassis mount connector recessed in the cabinet with 4-pole speakon connectors (NL4FX) on the cable with a pair of them on the amplifier end (wired as 2-pole of course). Obviously going for pro audio look and idiot proof connections rather than gold-plated binding posts and fancy cables. The Magic Pebbles are installed inside the cabinets adjacent to the drivers to maximize effectiveness :p I considered adding speaker spikes but decided to go unconventional and installed Magic Sliders so I can actually move these beastly speakers without a fight. I installed an access panel to get to the D2 compression driver and crossover. Cap screws with wood threads make for an easy solution if there is any need for access.

69207

Speaking of amps, I picked up a Yamaha P2500S for the horns and a P5000S for the woofs. Supposedly the fans come on if they get hot...haven't heard them yet. Probably way more power than I will ever use at home but they should be bullet-proof. You can't see it in the photo but the rear of the equipment cabinet has cut-out so that the amps pull air in the front and out the back to the outside world.

Crossover duty is being handled by a pair of MiniDSP OpenDRC-AN units (https://minidsp.com/products/opendrc-series/opendrc-an) with one on each speaker....excellent documentation of the work by POS (Thomas) here https://minidsp.com/forum/opendrc-projects/10584-jbl-m2-crossover-with-the-opendrc Total cost for amps and DSP was under $2k which seems like a bargain compared to the iTech solution. If you already have amps, the OpenDRC units will cost you about $720 counting the duty and tax invoice that FedEx sent me. Lots of untapped PEQ (IIR) filters available for tuning the system to better match the room...

Implementation was very simple except for some issues I had with getting the input/output levels correct and running down ground hum issues introduced by adding the amps and using my Yamaha RX-A2010 AVR as the source. Getting the wife out of the house for an evening was the key. Hard to hide in this house when running frequency sweeps and some music test tracks at reference level. The DIY M2 now sound like they are supposed to (phenomenal) and they are integrated with the rest of the speakers in the home theater system. Haven't had the chance to play a good blow 'em up movie to check the bottom of the bottom end but I suspect that paired with the B460 will get the job done.
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[dprice]

reserved # 3

[srm51555]

Looking real good, can't wait to see the final product.

I like the way you inverted the ports.

[pos]

One word: Wow wow wow! (three actually)
I like the way the sides of the horn meet the outer panel of the enclosure: looks like it is perfectly flush.

[sebackman]

Nice !!

Good idea with the ports. I have much smaller cabinet so I'm still struggling with where to mount the port and how to get room for flairs. Maybe you idea can save the day. :-)

I will try to seal the WG on the edges like you, but it may prove to be difficult due to them not being completely parallell.

Very nice in Rosewood!

Kind regards
//RoB

[pos]

I did the same thing for the ports, only ordering inner flares. The version we get in europe is similar to the precision ports from parts express, but it does not sell as a full kit: you have to buy each part separately so it is less expensive to only buy inner flares rather than to put the more expensive outside flare in the inside (if that makes any sense).
I must say I was a little bit disappointed by the quality tho: most of the flares have markings on them, and even after selecting only half of them as outside part I still have to do with visible markings on some of them...
Maybe the outside flare have a better finish :dont-know:
Anyway, I prefer a few marks than a bunch of srcew holes.

[dprice]

Appreciate all the responses. The waveguide is a tight fit (but not sealed) between the cabinet sides but there is a small gap at the surface since the sides of the waveguide are slightly tapered. I literally had to beat beat it into place after trying to sand off part of the front-back taper since the top of the waveguide would not drop into place as planned. :banghead: The bottom half fit nicely. I assumed this was because the box was off but it could have been due to the waveguide being wider at the top than bottom. I never thought to check. Going with black paint on the inside edge around the waveguide helps hide the minor (and less than uniform) gap that is there. It just disappears under normal lighting and viewing distances. Using the gasket tape on the back of the waveguide allowed a bit of depth adjustment to get the edges more or less flush with the cabinet sides.

My original plan was to have the top edge of the waveguide flush with the top of the cabinet like factory M2. Half-way through construction I chickened out and added a layer of plywood on top to get a consistent 3/4" edge all the way around.

Next up will be trying to build an acceptable grill and ordering some smoked glass for the tops. They weren't in the living room for 48 hours before knick-knacks and a candle holder appeared on top of them. A metal candle holder with bare metal feet :eek:

The wife is breaking them in as we speak....Judge Judy and Law & Order never sounded clearer.

[Ed Zeppeli]

Those look great!

[SMT]

sooooooooo jealous! Stunning. :applaud:

[DS-21]

Stunning execution!

I like the "body on frame" construction method. Did you add any damping between frame and outer panels, a la Mark Dodd (Tannoy DMT/KEF LS50/new KEF Reference)?

[Fitero]

Thank you for sharing. Very nice!

I am waiting for my parts to start building my own, and I was getting nervous about making the cabinets exactly like the original M2s. Your method of construction seems better suited to my limited skills.

[srm51555]

Anyway, I prefer a few marks than a bunch of srcew holes.

Very true, I plan on inverting them as he has shown this summer when I send the cabinets off to paint. Right now mine look like they came as a kit from parts express:p.

[Ed Zeppeli]

You really can't go wrong with those pro Neutrik Speakon connectors. Just look at the contact area on them!

Good job.


Warren

[audiomagnate]

Dayum!

[NWCgrad]

Very nice build! I bet they sound fantastic.

[dprice]

I spent quite a while trying to figure out how to do a curved grill to match the profile of the M2 waveguide. After a little measuring I cut an arc with a radius 4' 9" and it looked about right. Glued up some scrap 1/4" plywood and came up with a grill frame. I used perforated metal from McMaster-Carr (# 92725T22 Hexagon-Hole Perforated Sheet, .030" Thickness, 22 Gauge Steel, .25" Diameter, 79% Open Area, 36" X40") to attach to the grill frame to form the curved profile for the fabric. This material is rather thin and light duty - it will serve the purpose but will provide minimal protection from rowdy drunks and children.

I used 2-part epoxy to secure the grill to the frame and then used body filler (Bondo) to smooth everything up. Lots of sanding followed by a healthy does of flat black spray paint. I used basic black grill cloth and followed Saeman's Zilch Cloth Installation method (http://www.audioheritage.org/vbulletin/showthread.php?7941-Zilch-Cloth-Installation). No need to show how sloppy my attempt turned out. Neo magnets were previously installed in the baffle and matching neo magnets went in the grill frames. Note - pay attention to polarity.

The clones were not in the living room for a day before photos, knick-knaks and plant :eek: appeared on them. I also found myself setting beers and tools (always plural and always together?) on top of them....they are a perfect height. So I ordered some smoked glass tops from the local glass shop....1/4" thick, tempered, with beveled edges. Measuring and calling in the order was the easiest part of the project so far :)

[srm51555]

Spectacular work again Don.

[JuniorJBL]

Very nicely done Don!! Congrats on a fantastic looking pair of M2's! :applaud:

[Mr. Widget]

Very pretty... nicely done.


Widget

[Odd]

Fantastic work!

[bubbleboy76]

Impressive :)

[dprice]

Thanks guys! I could not have done it without help and advice of the Lansing Heritage crew.

[pos]

Wow! :thmbsup:
It reminds me of Widget's drawings: http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=379478&viewfull=1#post379478

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=66621&stc=1&d=1440742513

[sebackman]

Nothing short of brilliant!

Those are really good looking and I actually prefer them to the originals withthe front covering the ports.

Congrats to a pair of very fancy looking M2’s

//RoB

[Hoerninger]

Great :thmbsup:
____________
Peter

[jlac4]

hello
does antone can give me the dimensions of the JBL M2 waveguide ?
Height, width, depth .
Thank you and long live to this thread

[pos]

Hello

448mm x 394mm (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=379462&viewfull=1#post379462)

I will measure the depth(s) tonight.

[Doctor_Electron]

YES !

Outstanding.

I have three questions.

First, what music do you listen to with them?

Second, (and I know this is a tough one) do you have a number as to the completed weight of each? I'm thinking you would have had to measure components, parts, subassemblies etc. prior to final assembly.

Third, would you mind posting details about your listening experiences, regarding the systems' sonics, imaging/soundstage in that room, and the qualities of their rendering of the media (as in Q.#1) ?

Thanks, -d. E.

[pos]

Hello

448mm x 394mm (http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=379462&viewfull=1#post379462)

I will measure the depth(s) tonight.

depth is around 80mm from the baffle, depending on what you call the baffle (is is a two-part assembly) and if you account for the adapter or not.
The the waveguide also has a ~40mm overhang from the baffle, again depending on what you call baffle, and what part of the profile you are measuring...
So total depth of the profile (from the throat to the mouth) is around 120mm.

[sebackman]

Hi dprice

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

Fs for 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 if system Fs is lower than the driver Fs. I will post a separate thread on that. -Also posting this question in the other DIY M2 thread.

Kind regards
//RoB

[dprice]

I haven't measured anything. The wife will be working late tomorrow so that may give me a chance to measure them.

[Kalle]

Impressive build:applaud: If mine get half this nice I will be wery happy;) I hope to get the last parts this week (D2 drivers). I will try to start with my build soon. I wounder what ports and what length you used? URL?
I`m thinking of these ones and the inner flare in 75mm. http://www.hifikit.se/tillbehor/3-konisk-basport
According to Win ISD the 2x 75mm port should be about 160mm for 27hz.

Best regards
Karl

[dprice]

Karl,

I used these which I measure as 77 mm ID.

http://www.parts-express.com/precision-port-3-flared-speaker-cabinet-port-tube-kit--268-350

I can't find my notes but I'm pretty sure I went for about 9" (239 mm) overall for a 27Hz target tuning.

[pos]

I used the three-part JETSET70 kit that can be found in several online shops in Europe.
I only used inner flares to avoid screw holes.
It has flat rebates (contrary to the drawings) so It can easily be glued in place.

[dprice]

Looks like I got pretty close to 27 Hz if I'm reading this right.

70438

[JeffW]

Looks a tad lower to me, maybe 24?

[jlac4]

Thank you Pos for the answer .It's very kind of you .
I hope you will post some pictures about your DIY M2 .And I am waiting for your feeling about the comparison between your previous system and these JBL DIY M2.
I hesitate a lot in buying all the components to built by myself these M2; 4000Euros is a lot of money but I think it must be cheaper if we compare with other big system .It's Worth trying that .