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Author Topic: anyone built their own cabinet for 2268H subwoofers?  (Read 32828 times)

Matt Errend

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #10 on: April 06, 2010, 10:46:34 pm »

Adam Schaible wrote on Tue, 06 April 2010 21:01

Hi Art,

Do you know if that is +/- 23mm, or +/- 11.5mm for the JBL driver?  Either way, that's a lot.... but if the box is tuned correctly for what you're trying to do, I don't really see 8mm of xmax as an issue.



That has to be the P-P spec, otherwise the surround would be much much beefier.

I would assume that the "real" xmax is 11.5mm, in relation to the other drivers listed.

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Tim Weaver

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #11 on: April 07, 2010, 01:38:43 am »

Art Welter wrote on Tue, 06 April 2010 18:57

Tim Weaver wrote on Tue, 06 April 2010 13:40

Building from a plan provided by a manufacturer is actually less work than measuring what you have and then halving the volume.


And my recommendation for the B&C is due to output AND sound quality. A properly built dual 18 with 2 TBX100's is a better sub than an SRX728. It may not be louder, but it is more accurate. I'd pick the B&C sub over the 728 any day of the week. Besides, it's no slouch when it comes to output either!

Tim,

How do you define "accurate"?

Have you measured the distortion in both speaker types at various drive levels?



By ear alone. Mostly by comparing different subs while in use.

Older SR4719's were pretty decent subs for the day. They would be used in the same fashion that we are seeing SRX728's today. Mid-level club rigs up to regional summer festival stages using a bunch of them under some higher priced arrays.  4719's had a bit of muddiness to them when you got down low. Say under 60 hz. They would really have a loss of cone control (for lack of a better word) when you pushed them with pedal tones. Low key riffs, and 5 string bass would not be reproduced faithfully.

The SRX728 is an improvement on an order of magnitude compared to the 4719, but still exhibits some of these traits. These cabs have a ton of output though so they get paired up with some higher end array cabinets in order to fill riders. I've seen them under hangs of vertecs a bunch of times.

Compare though an SRX728 to the Vertec sub 4880 and no one would argue with you that the vertec sub sounds better, hits harder, and goes lower with more authority. Even the Dual 15 4882 will run circles around the 728, and it gives up a good deal of displacement to the dual 18. Bass lines are quite faithfully reproduced with these cabs.

The tbx100 from B&C is more in line with a high end arena rig subwoofer than it is the club level SRX type box. If you build a proper box for it, it will give you everything you would expect from an A level subwoofer.

That's what I mean by "more accurate". It gives me more of what I want and less of what I don't....

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Mike Caldwell

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #12 on: April 07, 2010, 08:08:40 am »

With some shopping around the Peavey Low Rider can be had for about $160 each. Great 18 inch speakers and if you dont want to design your cabinet Peavey has some pre designed plans to use.

Jeff Wheeler

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #13 on: April 07, 2010, 09:12:39 am »

Tim Weaver wrote on Tue, 06 April 2010 14:40

Building from a plan provided by a manufacturer is actually less work than measuring what you have and then halving the volume.

Well, the 728 is two separate chambers, one for each woofer, so it is actually easy to copy half of it.  I did take a few minutes to input the 18TBX100 into WinISD and other than some WinISD funkyness that I can probably get past with more time spent on it, its prediction is quite good for the application with a box tuned to 35Hz.  I may go this route.

Actually, I was surprised at how good the prediction looked.  I might build a single 18 for myself and see how it sounds.
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Tom Reid

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #14 on: April 07, 2010, 10:17:23 am »

Paul O'Brien wrote on Tue, 06 April 2010 10:21

Nobody in their right mind would buy those JBL drivers for a DIY cab when you can buy high quality drivers with similar capability from B&C and others for 1/2 the price or better. If he wants to roll his own have him pick up some B&C TBX100's or Emenince Definimax 4018LF for about $300ea from Parts express and load them in an appropriately sized box. There are other even less expensive drivers he could use too but but output and power handling begins to drop off with the lesser drivers, but then it depends what the needs are, PV Lowriders will come pretty close to these for about $200 a driver.

 http://www.parts-express.com/wizards/searchResults.cfm?srchE xt=CAT&srchCat=583



If power compression and heat are issues, the 2268h will rule over the 1/2 priced baskets.  Differential drive woofers will take a magnitude of heat above the competition.
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Tom Reid

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #15 on: April 07, 2010, 10:26:17 am »

Tim Weaver wrote on Wed, 07 April 2010 00:38

Art Welter wrote on Tue, 06 April 2010 18:57

Tim Weaver wrote on Tue, 06 April 2010 13:40

Building from a plan provided by a manufacturer is actually less work than measuring what you have and then halving the volume.


And my recommendation for the B&C is due to output AND sound quality. A properly built dual 18 with 2 TBX100's is a better sub than an SRX728. It may not be louder, but it is more accurate. I'd pick the B&C sub over the 728 any day of the week. Besides, it's no slouch when it comes to output either!

Tim,

How do you define "accurate"?

Have you measured the distortion in both speaker types at various drive levels?



By ear alone. Mostly by comparing different subs while in use.

Older SR4719's were pretty decent subs for the day. They would be used in the same fashion that we are seeing SRX728's today. Mid-level club rigs up to regional summer festival stages using a bunch of them under some higher priced arrays.  4719's had a bit of muddiness to them when you got down low. Say under 60 hz. They would really have a loss of cone control (for lack of a better word) when you pushed them with pedal tones. Low key riffs, and 5 string bass would not be reproduced faithfully.

The SRX728 is an improvement on an order of magnitude compared to the 4719, but still exhibits some of these traits. These cabs have a ton of output though so they get paired up with some higher end array cabinets in order to fill riders. I've seen them under hangs of vertecs a bunch of times.

Compare though an SRX728 to the Vertec sub 4880 and no one would argue with you that the vertec sub sounds better, hits harder, and goes lower with more authority. Even the Dual 15 4882 will run circles around the 728, and it gives up a good deal of displacement to the dual 18. Bass lines are quite faithfully reproduced with these cabs.

The tbx100 from B&C is more in line with a high end arena rig subwoofer than it is the club level SRX type box. If you build a proper box for it, it will give you everything you would expect from an A level subwoofer.

That's what I mean by "more accurate". It gives me more of what I want and less of what I don't....




VT8880 uses are redesigned 2268h (aptly named 2269h) that was designed to extend low frequency response.  Otherwise the drivers are mechanically identical.  The same applies to the 15" version of the VT sub.

There's nothing wrong with B&C drivers.  I'm a fan, and have replaced some beloved JBL drivers with B&C product.
However, the JBL will produce more output with less distortion and handle more heat.
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Jeff Wheeler

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #16 on: April 07, 2010, 10:46:34 am »

I am real partial to the 2268 drivers because I already own them, but I am going to take Charlie's suggestion and spend some time with WinISD to see if the B&C drivers come out significantly ahead.  I only did the 18TBX100 real quickly so far, to see if it would be hard to make it -3dB at 35Hz, and I have an Xmax problem, but I will be able to spend more time on it this weekend and see if it is solvable.
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Phil Lewandowski

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #17 on: April 07, 2010, 02:22:31 pm »

Tom Reid wrote on Wed, 07 April 2010 10:17

Paul O'Brien wrote on Tue, 06 April 2010 10:21

Nobody in their right mind would buy those JBL drivers for a DIY cab when you can buy high quality drivers with similar capability from B&C and others for 1/2 the price or better. If he wants to roll his own have him pick up some B&C TBX100's or Emenince Definimax 4018LF for about $300ea from Parts express and load them in an appropriately sized box. There are other even less expensive drivers he could use too but but output and power handling begins to drop off with the lesser drivers, but then it depends what the needs are, PV Lowriders will come pretty close to these for about $200 a driver.

  http://www.parts-express.com/wizards/searchResults.cfm?srchE xt=CAT&srchCat=583



If power compression and heat are issues, the 2268h will rule over the 1/2 priced baskets.  Differential drive woofers will take a magnitude of heat above the competition.


To back up what Tom is saying I would very much agree that the 2268's do a great job with heat, and I have always been impressed with how they handle higher "heating" power for several hours.


Take Care,
Phil
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David Morison

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #18 on: April 07, 2010, 06:01:36 pm »

Jeff Wheeler wrote on Wed, 07 April 2010 15:46

I am real partial to the 2268 drivers because I already own them, but I am going to take Charlie's suggestion and spend some time with WinISD to see if the B&C drivers come out significantly ahead.  I only did the 18TBX100 real quickly so far, to see if it would be hard to make it -3dB at 35Hz, and I have an Xmax problem, but I will be able to spend more time on it this weekend and see if it is solvable.


Hi Jeff,
Here's a quick comparison of the TBX, 2268 and Definimax, all in 360 litre 218 configurations tuned to 36Hz and all fed with 2kW. It looks like the JBL wants a bigger box if it's going to reach as low as the others. (frequency range shown is 25Hz to ~ 325Hz, the axis got cropped off when I edited it to fit the forum)

http://img180.imageshack.us/img180/937/tbxvs2268vsdefinimax.jpg

About the Xmax, I notice from comparing WinISD with Eminence's recommended designs that WinISD seems to overestimate the actual excursion, by as much as 25% in some cases, so that may not be as much of an issue as you think. If you have the time, try modelling some of their recommendations to see for yourself.

Here's what WinISD thinks the 3 drivers from the above comparison will do for excursion, again on 2kW for each 218.

http://img6.imageshack.us/img6/1425/xmaxcomparison.jpg

Regards,
David.

Edit - added excursion graph.
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Art Welter

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #19 on: April 07, 2010, 06:21:54 pm »

Matt Errend wrote on Tue, 06 April 2010 20:46

Adam Schaible wrote on Tue, 06 April 2010 21:01

Hi Art,

Do you know if that is +/- 23mm, or +/- 11.5mm for the JBL driver?  Either way, that's a lot.... but if the box is tuned correctly for what you're trying to do, I don't really see 8mm of xmax as an issue.



That has to be the P-P spec, otherwise the surround would be much much beefier.

I would assume that the "real" xmax is 11.5mm, in relation to the other drivers listed.


That would be a wrong assumption, and if you look at JBL’s  double voice coil differential drive magnet structure you can see they came up with a rather different (and patented) approach to making a woofer than the traditional method.

You can also see how the other JBL woofers have Xmax similar to other traditional drivers.

Xmax was traditionally defined by the overhang method. Overhang is the length of coil in mm that extends past either side of the top plate and is determined by the formula:
Xmax = gap height – [voice coil length/2]

The Audio Engineering Society (AES2-1984) defines Xmax as:
“The voice-coil peak displacement at which the “linearity” of the motor deviates by 10%. Linearity may be measured by percent distortion of the input current or by percent deviation of displacement versus input current. Manufacturer shal state method used. The measurement shall be made in free air at Fs.”

Wolfgang Klippel has a much more specific idea of what Xmax should be, but that is another kettle of fish...

In the 2008 JBL Theile Small parameters and definitions PDF that I quoted the Xmax figures from, their definition for Xmax is:

Peak linear displacement of driver diaphragm (0 to peak).

So the figures are one way.

The 2268 (23 mm Xmax) should be capable of 46 mm “linear displacement” peak to peak,  about 1.75 inch of movement.

Art Welter
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