Isobaric 2245

[gasfan]

Quick question. If I build full 10cu. cabs anyway, would using 2 per cab isobaricly not be an advantage? I happen to have 4 2245 with a 10cu. build plan. I would effectively have 20cu. cabs +or-. Is there a benefit to this? I'm not concerned about efficiency. What kind of extension would be possible? What effect on transient behavior? TIA

[Champster]

Quick question. If I build full 10cu. cabs anyway, would using 2 per cab isobaricly not be an advantage? I happen to have 4 2245 with a 10cu. build plan. I would effectively have 20cu. cabs +or-. Is there a benefit to this? I'm not concerned about efficiency. What kind of extension would be possible? What effect on transient behavior? TIA

I posted this same question months ago and didn't get many (helpful) responses. I think it is because not a lot of people have the means to devote this much money to a subwoofer. Thats not a slam, just the reality and therefore not much of an informed base to comment.

What is your goal is with this subwoofer? I have 2-2245's each in 9cf cabinets and love them. I use them below 35 hz and love them. They go plenty deep enough with enough power and control to be very impressive. If you really want to reduce distortion, go the Isobaric path. If you want greater output, double them up. I have a pretty good sized room and really like listening loudly and don't need the output of 4 18" subs.

So, what are your design goals?

[grumpy]

I like to check numbers before cutting wood.
A quick dry run in WinISD might provide some insight as to why folks aren't drooling all over this idea.
The trade space is pretty severe (e.g., power required vs output)

[gasfan]

I posted this same question months ago and didn't get many (helpful) responses. I think it is because not a lot of people have the means to devote this much money to a subwoofer. Thats not a slam, just the reality and therefore not much of an informed base to comment.

What is your goal is with this subwoofer? I have 2-2245's each in 9cf cabinets and love them. I use them below 35 hz and love them. They go plenty deep enough with enough power and control to be very impressive. If you really want to reduce distortion, go the Isobaric path. If you want greater output, double them up. I have a pretty good sized room and really like listening loudly and don't need the output of 4 18" subs.

So, what are your design goals?

I went through that thread. My point is I'm not trying to save space. And I'm not concerned about -3db. The plan I have has been put together by the crew here. Essentially a fully active franken-4345 with 2245, 2206, 2390, and 2405. But I just happen to have 4 2245s. Since everything up top is bigger than life, I'm thinking I might as well carry the theme all the way down. I've also noticed some comments about the upper range of the 2245 being a bit 'muddy'. So if there is a net gain in performance, I'd love to use all 4. Again, I'm not concerned about efficiency since they will be fully active. I have plenty of power to drive them.

[Ian Mackenzie]

You are more likely to get a smoother bass from 4 sources spaced around the front of the room than 2.

[gasfan]

I know you're right Ian. But I want to build a pair of stand alone speakers. Help can come at any time thereafter.

[loach71]

I know you're right Ian. But I want to build a pair of stand alone speakers. Help can come at any time thereafter.

What about building a triple chamber bandpass enclosure? I built four of them with qty TWO 2245H in each enclosure. The bass is prodigious.

[pos]

In theory isobaric will only let you save some volume compared to a single driver.

Here is an example of one of Mr Willy Peters' projects:
http://www.axiomaudio.net/realisations1.php
It is similar to yours, with a pair of 18" in isobaric configuration per side.
He is adamant that this isobaric configuration is the best there is :dont-know:

[gasfan]

What about building a triple chamber bandpass enclosure? I built four of them with qty TWO 2245H in each enclosure. The bass is prodigious.

I don't want to hide them or cut them off that low. I also want to preserve the impact of the 2245.

[gasfan]

In theory isobaric will only let you save some volume compared to a single driver.

Here is an example of one of Mr Willy Peters' projects:
http://www.axiomaudio.net/realisations1.php
It is similar to yours, with a pair of 18" in isobaric configuration per side.
He is adamant that this isobaric configuration is the best there is :dont-know:

I like it.

[Lee in Montreal]

Going in isobaric indeed allows to use half the cabinet volume. If the usual cabinet volume for one woofer requires 10cft, then you can run both woofers in 5cft. But you'll waste twice the amp power.

If you have four 2245 and don't know what to do with them, perhaps you can use two close to the main speakers, and two in opposite corners. You should be able to fill the room evenly, with a massive sweet spot in the center ;-)

[Ian Mackenzie]

If you simulate the port area and length in the smaller volume the port is much larger.

That might not be practical unless you are able to have a metre or so of 6 inch pic pipe.

[gasfan]

Going in isobaric indeed allows to use half the cabinet volume. If the usual cabinet volume for one woofer requires 10cft, then you can run both woofers in 5cft. But you'll waste twice the amp power.

If you have four 2245 and don't know what to do with them, perhaps you can use two close to the main speakers, and two in opposite corners. You should be able to fill the room evenly, with a massive sweet spot in the center ;-)

The idea is to still use the same 10cu. volume. And since they are fully active, separate mono amp for each driver.

I have four LSR&D Leach Superamp monos, two Model 101 stereo Leach amps, and two diy stereo Leach amps for a total of 12 channels. I will need just 10.

[more10]

You can build a pair of "push pull slot loaded (http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html)" boxes. The theory is that because all drivers are assymetric the result will be symmetric since one driver is mounted with the magnet out. The slot also creates a tighter coupling of the drivers than traditional mounting.

On top of that you can do a closed enclosure and use a Linkwitz transform to get low bass from the box. Either an analog Linkwitz (http://www.sound.westhost.com/project71.htm) filter, or a digital one (http://www.minidsp.com/applications/advanced-tools/linkwitz-transform). You should design for a total Q=0.5 because this will have optimal cone damping.

If I had four 2245, this is what I would do :-).

Mårten

[Lee in Montreal]

Marchand also makes a Linkwitz transformer and so does Kef. actually Kef has different version. They are all called Kef Kube.

http://www.marchandelec.com/wm8.html

I had a Kef Kube 200 and it was a very good bass enhancer for that last octave.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=53848&d=1322575781

[gasfan]

You can build a pair of "push pull slot loaded (http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html)" boxes. The theory is that because all drivers are assymetric the result will be symmetric since one driver is mounted with the magnet out. The slot also creates a tighter coupling of the drivers than traditional mounting.

On top of that you can do a closed enclosure and use a Linkwitz transform to get low bass from the box. Either an analog Linkwitz (http://www.sound.westhost.com/project71.htm) filter, or a digital one (http://www.minidsp.com/applications/advanced-tools/linkwitz-transform). You should design for a total Q=0.5 because this will have optimal cone damping.

If I had four 2245, this is what I would do :-).

Mårten

Thank you Marten. It's just that I want to see the drivers and I want to get punched in the chest. However, at 10cu. ft. with an effective volume of 20, does a linkwitz transformer really offer much benefit when I'm using active crossovers and separate amp for each driver?

[more10]

I made a simulation in WinISD. Two 2245 in a 688 litre box, that is 24 cubic feet. Q=0.5. The yellow curve is without Linkwitz transform, feeding 250W. The purple is with Linkwitz trasform feeding 75W.

https://dl.dropboxusercontent.com/u/106944188/2245-dual-closed-box.PNG

[more10]

One can also go vented (8 cubic feet tuned to 26 Hz)

Quick and dirty simulation, vented in grey. 250W signal. 515 litre (18 cu ft). 4 dB parametric eq at 30 Hz.

https://dl.dropboxusercontent.com/u/106944188/2245-dual.PNG

[gasfan]

Quick and dirty simulation, vented in grey. 250W signal. 515 litre (18 cu ft). 4 dB parametric eq at 30 Hz.

https://dl.dropboxusercontent.com/u/106944188/2245-dual.PNG

Is that the best you can do?

[grumpy]

"Is that the best you can do?"

LOL, keep up that attitude and you may very well get punched in the chest. :D

[gasfan]

"Is that the best you can do?"

LOL, keep up that attitude and you may very well get punched in the chest. :D

No shit. I'm buckin'.

See what happens when you don't add the smiley face:)?

[gasfan]

Is that the best you can do?

I meant that purely technically since I've seen graphs with flat response to something like 25hz with eq in much smaller cabs? And not isobaric.

[more10]

Well gasfan, you shurely fit my european predjucides about americans :-). No insult meant to Canadians, Mexicans,...

Since you have not specified any requirements, I have made some assmptions. Here in Sweden an average listening room (called vardagsrum) is 20 square meters (215 sq feet). Plan is often 4 x 5 meters. The length of the room decides the frequency limit of wave propagation. Below this limit you have no propagation, but instead you will get room gain. A 5 meter (16 ft) long room will have room gain below 34 Hz. A box with the 3 dB point at 25 Hz will sound boomy. So I chose to put the knee at about 30 Hz.

When reading the thread from start I realize you have already built the boxes, and wonder if putting a second woofer inside will give any benefits. It will not since the benefit of building isobaricly is to get a smaller box.

I have not made the simulation isobaric. Since you have stated that size is not a problem, you could build 2 more boxes. Experiment with the placement, 4 cornes on the floor or 4 corners on a wall.

I am not that interested in vented enclosures so I didn't put any effort into the vented simulation, I just kept WinISD suggested alignment of a super-boom-box. Since my vented box is twice the size of yours, and I used 2 drivers in my simulation, and you have only one in your box, I believe you have built super-boom-boxes :-)

The limiting factor of all bass designs is x-max. The lower you tune the box, the lower output you can get. My simulations is applying power to reach xmax at some point above 20 Hz.

[more10]

Now with the isobaric (WinISD defailt) alignment (130 litre, 4.5 cu feet, vented super-boom-box) in brown:

https://dl.dropboxusercontent.com/u/106944188/2245-isobaric.PNG

[gasfan]

Well gasfan, you shurely fit my european predjucides about americans :-). No insult meant to Canadians, Mexicans,...

Since you have not specified any requirements, I have made some assmptions. Here in Sweden an average listening room (called vardagsrum) is 20 square meters (215 sq feet). Plan is often 4 x 5 meters. The length of the room decides the frequency limit of wave propagation. Below this limit you have no propagation, but instead you will get room gain. A 5 meter (16 ft) long room will have room gain below 34 Hz. A box with the 3 dB point at 25 Hz will sound boomy. So I chose to put the knee at about 30 Hz.

When reading the thread from start I realize you have already built the boxes, and wonder if putting a second woofer inside will give any benefits. It will not since the benefit of building isobaricly is to get a smaller box.

I have not made the simulation isobaric. Since you have stated that size is not a problem, you could build 2 more boxes. Experiment with the placement, 4 cornes on the floor or 4 corners on a wall.

I am not that interested in vented enclosures so I didn't put any effort into the vented simulation, I just kept WinISD suggested alignment of a super-boom-box. Since my vented box is twice the size of yours, and I used 2 drivers in my simulation, and you have only one in your box, I believe you have built super-boom-boxes :-)

The limiting factor of all bass designs is x-max. The lower you tune the box, the lower output you can get. My simulations is applying power to reach xmax at some point above 20 Hz.

Not quite sure what that means but I hope I'm not in trouble. I need all the friends I can get!:)

A few years ago, you, Pos, Ian, and a few others put together a recipe for me for the 2245, 2206, 2390, and 2405. I just haven't gotten around to starting the project yet. The cabs were for 10.3 cu. ft. which I want to follow through with. I was thinking to make them isobaric with dual 2245s since I have them. My listening room is approx 20ft.X20ft.

[more10]

Not quite sure what that means but I hope I'm not in trouble. I need all the friends I can get!

I guess you just can't help it :-) Im still here.


A few years ago, you, Pos, Ian, and a few others put together a recipe for me for the 2245, 2206, 2390, and 2405. I just haven't gotten around to starting the project yet. The cabs were for 10.3 cu. ft. which I want to follow through with. I was thinking to make them isobaric with dual 2245s since I have them. My listening room is approx 20ft.X20ft.

You will have room gain below 29 Hz. Any of the designs made with the 2245 will need eq, so if you can change it in the filter you can adjust after you have built the boxes.

Regarding the 2245 you have, there is plenty of good advice in this thread. You just have to decide what you want to implement. Isobaric is not a good solution. If quality is more important than output go for closed enclosure. If output is more important than quality go for vented.

If placing two 2245 together, mount one driver with the magnet facing out in order to get symmetri. If placing the boxes in different corners there is no point doing this.

Yet another alternative is to build Onken enclosures. Play around with the online calculator: http://www.mh-audio.nl/onken_br.asp. It will sound more like a horn or a closed box, than a vented.

[4313B]

If quality is more important than output go for closed enclosure.I'd personally opt for the closed box linkwitz transform first. One can build an 8 cu ft to 9 cu ft box, add the transform and see if they like it. If not then they can vent the box as per the B460, apply the bump filter and go vented.

The linkwitz transform boxes for the 2245H can be much smaller than 8 cu ft but it will require a lot more amplifier power (risk burning out the VC) to achieve the same VLF response.

more10 is right in that one can use room gain to assist with the response. We have discussed this extensively over the years. The key is to get a real nice balance of transducer/enclosure response, room response and amplifier output without cooking the VC or breaking the VC off. The smaller boxes put more stress on the VC neck and they can pop apart. JBL went through that with the 121, 124/2203, 136/2231, 2235, 2245, etc. And that is exactly why J.M. reinforced the necks of transducers like the SUB1500 and W1500H. ;) An 8 to 9 cu ft box for the 2245H should work just fine. I built many of them over the last thirty-some years.

[more10]

Now with the isobaric (WinISD defailt) alignment (130 litre, 4.5 cu feet, vented super-boom-box) in brown:



With a parametric EQ of 4 dB at 30 Hz.

[more10]

The smaller boxes put more stress on the VC neck and they can pop apart.

Go for the 12 cu feet box (per driver). Q=0.5 is called critically damped for a reason. If output is too low, put in vents as 4313B suggests.

Make 4 boxes. Then you can try different placements, as well as together and one magnet facing outwards.

[4313B]

:hmm: HT BB6 Pro reports that an 8.757 cu ft box (net effective) with "typical" fiberglass fill yields a Qtc of 0.5 :dont-know:

Oh well, the transform should "fix" any difference. Just build some boxes and let the transform sort them out. :rotfl:

[more10]

:hmm: HT BB6 Pro reports that an 8.757 cu ft box (net effective) with "typical" fiberglass fill yields a Qtc of 0.5 :dont-know:

Oh well, the transform should "fix" the difference.

Could be wrong T/S parameters in WinISD, or a bug. This is what I have:

https://dl.dropboxusercontent.com/u/106944188/2245-ts.PNG
From JBL:

MODEL FS QTS QMS QES VAS EFF PE XMAX RE LE SD BI MMS FLUX
2245H 20 0.27 2.2 0.27 821.2 2.1 300 9.65 5.8 1.4 0.130 21 185 1.22

There is a big difference in QES. WinISD calculates it.

[more10]

Oh well, the transform should "fix" any difference.

In frequency domain yes. But not in time domain. It might sound very much alike, but the engineer on my shoulder tells me to build to Q 0.500000 :-)

[4313B]

In frequency domain yes. But not in time domain. It might sound very much alike, but the engineer on my shoulder tells me to build to Q 0.500000 :-)I hear you! ;)

This is what BB6 Pro has:

[4313B]

Disabling the damping option.

[more10]

Here we go. Disabling the whole "fill" nonsense:

Still one cubic feet missing. Can you try with my value for QES?

Since QES is calculated in WinISD there is probably something wrong with the JBL datasheet.

[4313B]

It didn't like the printed JBL value of Qes, volume suggestion went down a bit.

We went through this years ago with the E145 too. That is how we discovered some parameters had been documented by JBL incorrectly. In that case it looked like someone swapped a 4 and a 7 in the Vas value if I remember correctly. I think it was supposed to be something like 470 instead of 740, something like that.

[more10]

WinISD QES is 0.306.

So there is one cubic feet difference. If you simulate a 12 cubic feet enclosure, how much does that affect Q?

[4313B]

WinISD QES is 0.306.Right, sorry, I see that I used the 0.27 value you posted from JBL.



So there is one cubic feet difference. If you simulate a 12 cubic feet enclosure, how much does that affect Q?One with "typical" fill (0.449) and one with the "fill", aka "Damping" tab, disabled.

This is the net effective volume, nothing is taken into consideration, no bracing, no fill/damping, no transducer displacement, no series inductor, nada. Just an effective volume.

Usually what I do is build the box without anything BUT fiberglass fill taken into consideration via BB6 and the net effective volume works out just about right.

For example, I build a 9 cubic foot box, brace the hell out of it, bolt in the 2245H, put in the dual six inch diameter ports and I come up with a 7.8 cu ft effective volume. Then I line every panel except the baffle with 2" fiberglass from home depot and voila! 9 cubic feet effective volume. Sometimes I will just use 1" fiberglass to get a smaller net effective volume. If you don't use fiberglass, and everyone pretty much hates the stuff, then all bets are off with my little process.

6615366154

[pos]

Oh well, the transform should "fix" any difference. Just build some boxes and let the transform sort them out. :rotfl:

In frequency domain yes. But not in time domain.
A proper Linkwitz Transform (ie not a simple EQ, but a real asymmetrical shelving well matched to the actual parameters of the high pass, and correcting the response down to the VLF) will correct both magnitude and phase all in once (ie minimum-phase).
You can actually turn any 2nd order response into another one for both magnitude and phase using this technique, without any drawback beside a different power consumption curve.
WinISD Pro will let you test all that and show the resulting VA(f) curves.

[more10]

The difference in Q in a box without fill is 3%. Nothing to worry about.

Fill will increase the box size as seen by the driver, lowering the Q.

So anything between 9 and 11 cubic feet is ok for a closed box. Making the box bigger will give you plenty of room for vents if you want to add them later.

[4313B]

A proper Linkwitz Transform (ie not a simple EQ, but a real asymmetrical shelving well matched to the actual parameters of the high pass, and correcting the response down to the VLF) will correct both magnitude and phase all in once (ie minimum-phase).
You can actually turn any 2nd order response into another one for both magnitude and phase using this technique, without any drawback beside a different power consumption curve.
WinISD Pro will let you test all that and show the resulting VA(f) curves.I like the Crown as opposed to the miniDSP if only because the Crown makes it all so much simpler to me, plus, that all in one box thing is nice.
The miniDSP is very fun to play with though. I used it on my little Tannoy dual 6" subs which are linkwitz transforms.

In any case, I think we agree that isobaric isn't what we would do in our houses? :)

[Ian Mackenzie]

Interesting discussion

Have you evaluated them in your room in a standard enclosure yet?

I think there are two schools of thought or two roads.

Are you wanting subs or an integrated system?

If the former look at GTs original sub article. It recommends an equalised 8cu ft box vented.
Subjectively these woofers perform better dynamically in vented boxes.

The alternative is a larger un eq box about 12 cu ft
Crossed over below 80 hertz as recommended you don't have to worry about group delay or resonances from a large box.

I run one 2245 in 8 cu ft in my HT room with 800 watts and it's fine. Doubling the cone area will reduce the distortion below 50 hertz but thus depends on the room size and how loud you need it. I personally think for HT amp power is subjectively more important.

If you want stand alone boxes (like in the French link) it's a different ball game.

Integrating to the 2206 correctly in an important design goal as this will impact on out outcome subjectively particularly if you plan to run normal program material.

Attempting to crossover below 150 hertz will be challenging without sophisticated analysis.

Some people end up running them below the cut off F3 of the bass mif woofer and that is around 40 hertz with the belief that is the only way to do it.

You can do that but you will loose punch of the cone area and displacement of the 2245 in the hope on bass extension.

By crossing over from 150 hetz and above up to 250-300 hetz I think you will free up a lot of design goals and find it subjectively superior.

I have found between 9-10 cu feet optimum in a well brace enclosure and experient will the amount of fill and boundary layer damping on the walls ( too suppress standing waves 300-500 hertz).

Try and get the woofer at least 6 inches off the floor or better still use a graphic eq to correct any boundary reinforcement in tbe 100 hertz range.

You really need to do this or it will sound like a dogs breakfast no matter how well thought out the design is.

This is what gives the impression of lack of bass clarity. The woofer is either in piston range or it's not. Speed and all that is crap provided you not inviting significant group delay by trying to stretch the f3 that is swamped by room gain in most
cases anyway.

Hearing an integrated system well set up with a Smart Live using the 2245 (like Bo's 4345) is an eye opener.

This ties in with 4313's comments in the earlier post.

You can attempt to design for a balance of driver, box and room response Or you can modify the response externally with active EQ (like the M2).

[gasfan]

I guess you just can't help it :-) Im still here.


You will have room gain below 29 Hz. Any of the designs made with the 2245 will need eq, so if you can change it in the filter you can adjust after you have built the boxes.

Regarding the 2245 you have, there is plenty of good advice in this thread. You just have to decide what you want to implement. Isobaric is not a good solution. If quality is more important than output go for closed enclosure. If output is more important than quality go for vented.

If placing two 2245 together, mount one driver with the magnet facing out in order to get symmetri. If placing the boxes in different corners there is no point doing this.

Yet another alternative is to build Onken enclosures. Play around with the online calculator: http://www.mh-audio.nl/onken_br.asp. It will sound more like a horn or a closed box, than a vented.

I can't remember the last time my wife said that. Thanks.

Lee mentioned the Onkens also. Yes, lots of good advice. Thanks so much.

[gasfan]

Interesting discussion

Have you evaluated them in your room in a standard enclosure yet?

I think there are two schools of thought or two roads.

Are you wanting subs or an integrated system?

If the former look at GTs original sub article. It recommends an equalised 8cu ft box vented.
Subjectively these woofers perform better dynamically in vented boxes.

The alternative is a larger un eq box about 12 cu ft
Crossed over below 80 hertz as recommended you don't have to worry about group delay or resonances from a large box.

I run one 2245 in 8 cu ft in my HT room with 800 watts and it's fine. Doubling the cone area will reduce the distortion below 50 hertz but thus depends on the room size and how loud you need it. I personally think for HT amp power is subjectively more important.

If you want stand alone boxes (like in the French link) it's a different ball game.

Integrating to the 2206 correctly in an important design goal as this will impact on out outcome subjectively particularly if you plan to run normal program material.

Attempting to crossover below 150 hertz will be challenging without sophisticated analysis.

Some people end up running them below the cut off F3 of the bass mif woofer and that is around 40 hertz with the belief that is the only way to do it.

You can do that but you will loose punch of the cone area and displacement of the 2245 in the hope on bass extension.

By crossing over from 150 hetz and above up to 250-300 hetz I think you will free up a lot of design goals and find it subjectively superior.

I have found between 9-10 cu feet optimum in a well brace enclosure and experient will the amount of fill and boundary layer damping on the walls ( too suppress standing waves 300-500 hertz).

Try and get the woofer at least 6 inches off the floor or better still use a graphic eq to correct any boundary reinforcement in tbe 100 hertz range.

You really need to do this or it will sound like a dogs breakfast no matter how well thought out the design is.

This is what gives the impression of lack of bass clarity. The woofer is either in piston range or it's not. Speed and all that is crap provided you not inviting significant group delay by trying to stretch the f3 that is swamped by room gain in most
cases anyway.

Hearing an integrated system well set up with a Smart Live using the 2245 (like Bo's 4345) is an eye opener.

Thanks again Ian. I will stay with vented.

[pos]

I like the Crown as opposed to the miniDSP if only because the Crown makes it all so much simpler to me, plus, that all in one box thing is nice.
The miniDSP is very fun to play with though. I used it on my little Tannoy dual 6" subs which are linkwitz transforms.



Can you do L-T with the Crown? When I checked the architect software I don't remember seeing any L-T.
Hypex has asymmetrical shelvings which are the same thing.
Too bad the Crown does not let the user load biquad IIR coefficients, and even FIR ones for that matter...
Being able to freely use the FIR in the crown (instead of those textbook linear phase filters that are of no use if the acoustical slopes cannot be taken care of first) would let M2 users linearize the phase of the 800Hz crossover, and even possibly the BR...


In any case, I think we agree that isobaric isn't what we would do in our houses? :)
I have never tried it myself, but I cannot see any really good theoretical advantage to it (if EQ is a given...). T can so many disadvantages and pitfalls when implementing it tho, especially with 18" drivers that are supposed to play up to the midbass range :blink:

[gasfan]

Are you still planning on using the 2390?

Not wanting hi jack the thread but this image says it all.....lol

I will delete later....Lol

I just love the look of the 2310 lens which I have a beautifully restored pair of. Is there an economic reason for the 2421? How would a 2441 compare?

[Ian Mackenzie]

I just love the look of the 2310 lens which I have a beautifully restored pair of. Is there an economic reason for the 2421? How would a 2441 compare?

I gave not used either so I can't comment.

The 2310 and the 2441 will go lower and louder in theory.

I mentioned the 2310 as the profile of the box will need to allow the output of the horn to be at the listening height

[more10]

I just love the look of the 2310 lens which I have a beautifully restored pair of. Is there an economic reason for the 2421? How would a 2441 compare?

2441 is the proper driver for 2309 horn. The 2421 needs an adapter. Since you will have a supertweeter there is absolutley no reason whatsoever to use the 2421. Get a pair of 2441 right away. Make shure the diaphragms are ok.

2441 with 2309 horn will reach 800 Hz. Voices will sound much different with the 2441.

All the old horns and lenses: http://www.jblpro.com/pub/obsolete/Acoustic_Lens_Family1.pdf

[gasfan]

Okay, here's the line-up, which doesn't necessarily mean I'm not blowin' smoke. This stuff's been packed away in my basement for the past 4 years. The 2405s could use a coat of paint and the 2310s are missing the felt dampers. Otherwise it's all in great shape. I may just swap out the 077s in my L65s which are perfect. I don't know what it is. I've got the hankerin' but not the gumption it seems. All I've done so far is draw a few cab shapes. I was thinking to keep them as narrow as possible and taper them for imaging and vent them out the bottom a la Kef. 66158

[gasfan]

Is there something here that could explain my lazy-ass nature?66159

[ivica]

Thanks again Ian. I will stay with vented.

Hi gasfan,

May be you can try with about 320 Lit box plus about 125 Lit box for two 2245 mounted 'back to back' in the isobaric chamber, so totally about 445 Lit, ant the box tuned around 27Hz, so can get almost -3dB at about 26Hz in "2pi" surrounding. In the room some dB (10~15) can be expected to be get too at the lower frequency range, and can reach almost 120dB with 48Veff power amp supply. Using isobaric suggested enclosure 2nd harmonic distortion can be reduced too.

regards
ivica

[gasfan]

Yes yes, I'm liking it. My name is Peter but this may very well end up being the 'summer of George'. ;)

I have not yet seen a reason why isobaric would not enhance the performance of the 2245. Even if it's just a little, I'm happy.

[more10]

I have not yet seen a reason why isobaric would not enhance the performance of the 2245. Even if it's just a little, I'm happy.

I give up :-)

[4313B]

Just for grins I worked up one in BB6P. It yields a solid 21 Hz in an 9 cubic foot volume. I suppose one could use a 17" diameter sonotube for the subchamber. The vent is quite long. Too much of a hassle for me.

[gasfan]

I give up :-)

Please bear with me. You've been very virtuous so far!

I have the original plan you guys worked out for me which is likely what I'll end up using. I just thought it worthwhile to consider isobaric since I have the drivers. You've all been awesome here.

[gasfan]

Just for grins I worked up one in BB6P. It yields a solid 21 Hz in an 9 cubic foot volume. I suppose one could use a 17" diameter sonotube for the subchamber. The vent is quite long. Too much of a hassle for me.

You mean trouble getting it to fit? I'm going to build separate cabs with identical footprint for each driver and stack them so the 2245s would be by themselves.

[gasfan]

Hi gasfan,

You can see the differences
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=66160&stc=1&d=1437858554

regards
ivica

Looks to me like the horse is the one kicking.

[more10]

I went through that thread. My point is I'm not trying to save space.


Isobaric is about saving space, nothing else. You are having problems with the wife?



It's just that I want to see the drivers and I want to get punched in the chest.

You will get more punch from 4 traditionally mounted drivers. Build 2 boxes as planned and two separate boxes for the other two 2245.

Using closed boxes will sound as high as the vented isobaric monster. Sounding much better though.

The engineering required to stick two 18 inch drivers, one 12 inch, a large format driver and a horn into 150 liters is beyond me. The small isobaric compartment will hold the heat from at least one 18 inch driver. You will have power compression at medium listening levels and at high volume letting the smoke out of the 2245.

Now I am really giving up :-)

[gasfan]

Isobaric is about saving space, nothing else. You are having problems with the wife?



You will get more punch from 4 traditionally mounted drivers. Build 2 boxes as planned and two separate boxes for the other two 2245.

Using closed boxes will sound as high as the vented isobaric monster. Sounding much better though.

The engineering required to stick two 18 inch drivers, one 12 inch, a large format driver and a horn into 150 liters is beyond me. The small isobaric compartment will hold the heat from at least one 18 inch driver. You will have power compression at medium listening levels and at high volume letting the smoke out of the 2245.

Now I am really giving up :-)

Okay, I hear you. But where I'm getting hung up is the issue regarding vas. Bottom line is I'm building 10-12 cu. boxes whether they're isobaric or not. So if they are isobaric, the effective volume is bonus, no? I'd be saving space if the need was to build massive 20cu. cabs. But in my case, the added effective volume is incidental, so why not? That's all. If you tell me non-isobaric is more dynamic, then isobaric is no bonus at all. I will then definitely go traditional. As I mentioned, the 2206 and the 2390 will have their own enclosure with identical footprint of the bass bin to stack the whole lot. I will build them as deep as necessary to accommodate this design in order to fit my seating position.

Please understand that if it weren't for this and other forums, I'd still get it done, albeit without any insight to guide me as I have no prior experience or education in this field. I'm seriously counting on you and the others to help me grasp the practical outcomes and consequences of speaker design. So yours and others' experience and opinions are very valuable as you must know. I'd probably have to read an entire textbook to glean what I'm learning in this one thread. I'm honored by the attention.

Oh, my wife has built herself a 'woman's cave' in our second bedroom. I still have to get around to renovating the basement.
Did I mention I'm a lazy-ass?:)

[more10]

As I mentioned, the 2206 and the 2390 will have their own enclosure with identical footprint

Why? I'm also lazy :-)

[gasfan]

They will be very heavy(300lbs?) so I thought modular construction would be more convenient. Another way would be to have just one main cab that comes apart in sections, ship-lapped together with a gasket.

[more10]

Maybe this is the reason JBL never built such a speaker :-)

Some inspiration: http://jbl43.com/?mode=f3

I don't think this is a problem. Just remove the drivers to make it lighter when shifting house. Use furniture wheels beneath. The volume behind the other drivers is needed by the 2245. Build with just one 2245 in each cabinet. If you need extra bass, build separate cabinets for the other two 2245.

Do you have a link to the old project thread?

[gasfan]

Maybe this is the reason JBL never built such a speaker :-)

Some inspiration: http://jbl43.com/?mode=f3

I don't think this is a problem. Just remove the drivers to make it lighter when shifting house. Use furniture wheels beneath. The volume behind the other drivers is needed by the 2245. Build with just one 2245 in each cabinet. If you need extra bass, build separate cabinets for the other two 2245.

Do you have a link to the old project thread?
Nice compilation.

This thread morphed into the build thread:http://www.audioheritage.org/vbulletin/showthread.php?33388-C-1200-1200H-bass-horn-or-transmission-line/page4

[gasfan]

Okay, after deducting volume for drivers and braces including dog box, I get about 10.34 cu. ft. But the tapered rear part is a 'fat' prism so probably closer to 11. I'll be able to tailor it to Ian's suggested volume. Double 3/4 birch ply. External measurements; 47" high X 22" across the front X about 3866213" deep, taper beginning about 24" back to a point. The 2245 is about 6.5" up, however with a 2.5" cleat, it will sit 9" off the floor. The center of the horn will be 46" up, exactly ear level. 12 sheets of 3/4 5X5 birch ply. And that's that. Or I should say will be:blink:

[more10]

Excellent!

Double plywood. See if you can get acoustic damping glue.

[gasfan]

I am a renovation contractor so I am aware of a number of products designed for noise dampening. However, absorption is not the same as prevention. But it would be an interesting experiment to use the former to facilitate the latter. I have a pair of KEF 105.2 with the isolastic mounting scheme. As opposed to the series 1, the drivers are suspended in front of the cabs on rubber mounts with a soft foam gasket which while not compressed, makes contact with both driver and cab. This drastically reduces cab vibration. This not only allowed for more economy in building the cab, but resulted in a better FR. However, the Series 1 with the heavier cab is known to be the better sounding one. But they also had drivers capable of higher power/spl so it's a tough call. The question I have since I've never heard a pair of Series 1, is how transient performance is affected by this design. It seems to me that not compromising cab integrity and yet implementing the design would actually improve transient performance just by the nature of dynamic speaker function, no? Because now you have the motor's opposite movement corresponding to the cone resulting in a faster response. Mind you the entire assembly would obviously need to be tuned to optimize it. But this could be accomplished in the suspension with a tension adjustment and tuned on the fly.

[more10]

I have used the Swedish glue DG A2: http://www.swedac-acoustic.se/sidor/stomljuddamp.htm#DG A2

The result was elimination of high frequency resonance. The cab sounded "dead" when knocking.

[gasfan]

As I mentioned, there is no shortage of products designed for this purpose here. I intend on sandwiching a layer of heavy roofing felt between the two plywood layers with one of the mastic dampening compounds available such as Green Glue. But what I'd like to hear is your comment on the idea of isolastically mounting the drivers.

[more10]

But what I'd like to hear is your comment on the idea of isolastically mounting the drivers.

I don't like that idea. But you could mount the drivers on the inner plywood sheet.

Screw the bracing only on the inner plywood. Then the inner box will be "floating" in the outer box.

[gasfan]

I Don't want to introduce diffraction issues on the baffle but it would nonetheless make for a challenging solution in terms accessing the drivers, no? But why don't you like the idea of the isolastic mounts?

[Ian Mackenzie]

If your only using the 2245 up to 300 hertz then the box really only needs to be stiff as in bracing as the panels will not be excited by higher frequenciesx than the LF main chamber is reproducing.

The smaller inner chamber for the 2206 will have smaller panels which will be more rigid due to their size.

Enclosure fill for the 2206 will suppress most internal box noise.

In practise you can feel panel resonance by using sweep tones.

From my own point of view the front panel is the most important as it faces the listening position and therefore must not transmit any internal sound or that of it's own. So make it thick and rigid.

Typically you hear a blend of direct and reflected sound so we want the direct sound to be as acurate as possible.

Whereas every other wall boundary in the room will add reflected sound and at some frequencies self resonate. If you can't control that then it makes no sense to over engineer the entire enclosure.

By measuring the internal depth, length and wide the standing wave frequencies can be calculated.

The longest dimension in theory will have a standing wave around 150 hertz and will depend on the position of the woofer.

Attempting to suppress a standing wave at that frequencies would impact on the internal box volume.

Again at those frequencies any tendancy for resonance will be swamped by room modes which could be in the order of 10 decibels or more.

Thie use of a mid/bass driver effectively eliminates most box noise related issues ad this isolates harmful box noise from sensitive mid band frequencies.

On the other hand a simple 2 way system crossinigbover at 800-1000 hertz imposes significantly more demands on box design.

A small 2 way loudspeaker with a crossover point of 250@ hertz ihad even more box issues and this is where all the hype on box panels comes from.

The thing I would be looking at is the interaction of the woofer and the mid bass driver in the crossover region. Try and get that as smooth as you can.

[macaroonie]

Back in the day when I was at Ariston we had a distribution agreement with QLN in Sweden.

They made some VERY good small speakers using visco elastic damped panels for the cabinets . We took that methodology and applied it to turntable plinths.

read here http://qln.se/reference-information/qboard/

In our case we did not have corners to deal with , the visco layer < 1mm was concealed in a shadow gap. As I recall they did not do dual layer construction as such , they simply made sheets of MDF with the visco layer in between and then constructed as per normal

The visco material as we got it was like thick PVA but it contains VE micro spheres. You simply laminate two sheets together with the adhesive at a set qty or thickness to give just less than 1 mm. Allow to set and you are done and can construct normally.

The corners are not so much of an issue as that is not where the vibration occurs.

I cannot recall whether the drivers were mounted on the inner layer but if you are so inclined there is no reason not to do that.

Not so sure about viscous mounting although DCM did that in the Time Window and they were pretty darn good .

The Q Board had a very beneficial effect on the turntable performance.

[gasfan]

Looks like the product Marten mentioned does exactly that as does the Green Glue I mentioned. However, I'm thinking about using roofing felt immersed in Acoustiseal. It's that black caulk used in construction to seal vapor barrier and gaps between double studs and bottom/top plate, etc.. It never sets or dries thereby maintaining a perpetual seal regardless of the warping over time of the structure it's applied to. I've removed drywall from 20+ year old walls and wherever it was used it was as gooey as new. I would bond only the perimeters of the panels. That goo will absolutely terminate any movement.

But I would still love to hear a technical analysis of the isolastic driver mounts.

[macaroonie]

The stuff Marten linked will probably be the same as the stuff I was using as it came from Sweden also. Somewhere there is a paper that describes the action of visco elastic in lam panels.
It is very effective in noise , read vibration , suppression. One of the applications is coach and bus floors.
Read up on ' constrained layers '

Marten will probably add more info

From it's description ' green glue has the same properties , for those interested :

http://www.fullcompass.com/prod/245603-Acoustic-Geometry-ASGG29

[gasfan]

It seems that would be the ultimate way to apply it.

[more10]

But I would still love to hear a technical analysis of the isolastic driver mounts.

Driver should be making sound, not energy in the mounts. The driver should be mounted as firm as possible.

Great find Macaroonie!

The isoelastic glue should be used between two sheets of same thickness for maximum efficiency. Vibrations are damped by generating heat in the glue.

[macaroonie]

The isoelastic glue should be used between two sheets of same thickness for maximum efficiency. Vibrations are damped by generating heat in the glue.

Exactly this .

[more10]

Back in the day when I was at Ariston

My second turnable was the Ariston RD 40 :-) http://www.vinylengine.com/library/ariston/rd-40.shtml

[macaroonie]

Cool. RD 40 was very good but it had far too many machined parts in it for the price it sold at.
I worked to reduce the parts count and hence cost across the range , it's amazing how much you can strip out without reducing performance. At the same time Q Board appeared and we incorporated that into various designs. We laminated batches of board with the VE adhesive supplied from QLN in Sweden.
I had a budget prototype similar to a Rega in format , using Q Board for the plinth. It surpassed the much more complex RD80 by a scary amount. It became the RD50. Most of the things that made the RD50 work were incorporated into the RD80 although visually you would hardly know. Here's a RD50/60 The line around the plinth is where the VE adhesive is. You can't quite see where the arm mounting collar has been eliminated

66222

Simple things , for example the arm pillar used to be made with a mounting collar that then bolted on to the deck's mounting plate. We binned the collar ( making the Jelco arms cheaper incoming 500 at a time ) and machined the arm mounting plate to incorporate the pinch screw for the arm pillar. Got rid of the cork gasket also.
Result was a worthwhile improvement in clarity.
In production every penny counts and if you can reduce costs AND improve quality then , you are a winner.
I was messing about with Q board for chassis inside the suspended decks with some success , the RD 110 was in need of a re vamp. I left for the US before I got to that.

Sorry about the thread Hi Jack

[gasfan]

Driver should be making sound, not energy in the mounts. The driver should be mounted as firm as possible.

Great find Macaroonie!

The isoelastic glue should be used between two sheets of same thickness for maximum efficiency. Vibrations are damped by generating heat in the glue.

I went through my little archive of paraphernalia I've collected over the years and came across a KEF brochure showcasing the Series2 105. They do in fact claim improved transient performance with this system. It would be nice to have a series1 to compare.

[gasfan]

Cool. RD 40 was very good but it had far too many machined parts in it for the price it sold at.
I worked to reduce the parts count and hence cost across the range , it's amazing how much you can strip out without reducing performance. At the same time Q Board appeared and we incorporated that into various designs. We laminated batches of board with the VE adhesive supplied from QLN in Sweden.
I had a budget prototype similar to a Rega in format , using Q Board for the plinth. It surpassed the much more complex RD80 by a scary amount. It became the RD50. Most of the things that made the RD50 work were incorporated into the RD80 although visually you would hardly know. Here's a RD50/60 The line around the plinth is where the VE adhesive is. You can't quite see where the arm mounting collar has been eliminated

66222

Simple things , for example the arm pillar used to be made with a mounting collar that then bolted on to the deck's mounting plate. We binned the collar ( making the Jelco arms cheaper incoming 500 at a time ) and machined the arm mounting plate to incorporate the pinch screw for the arm pillar. Got rid of the cork gasket also.
Result was a worthwhile improvement in clarity.
In production every penny counts and if you can reduce costs AND improve quality then , you are a winner.
I was messing about with Q board for chassis inside the suspended decks with some success , the RD 110 was in need of a re vamp. I left for the US before I got to that.

Sorry about the thread Hi Jack

It's all pertinent:)

Btw, it looks like the RD 40 hi jacked my Oracle Alexandria

[macaroonie]

Alexandria is one of my favorites. You got the stock Sumiko arm ?

[gasfan]

Alexandria is one of my favorites. You got the stock Sumiko arm ?

Mine was the first iteration of the Oracle, bought back in 78'. I don't have it anymore. I got it with an FR-14 and Dynavector Ruby. Played it through a pair of Meridian 105 monos, also first iteration, into the Kef 105s. Great set-up.

[chrapladm]

Curious what you ended up doing?

[gasfan]

I'm still at the drawing board. I don't think I will go isobaric because I don't want to look at the back side of the drivers. The other way presents a heat issue. I presented a rough sketch on another thread. Coincidentally, it's similar to Champster's with tapered sides.

[chrapladm]

If you dont mind a giant subwoofer you can always do a PPSL slot loaded design. BUT these drivers need a LOT of room. SO probably 500 liters or so for a 24hz or so tune. This would be a pair of 2245's in a single cabinet.

67205

[wrager]

me likey Chrap!!!!