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Author Topic: anyone built their own cabinet for 2268H subwoofers?  (Read 32992 times)

Art Welter

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #20 on: April 07, 2010, 06:37:52 pm »

David,

The 4018LF has an Xmax of 7.9 mm.
The B&C 18TBX100 has an Xmax of 10 mm.
According to your sim, they both have exceeded Xmax with 2kW.

index.php/fa/29306/0/

The 2268 is no where near its rated Xmax of 23 mm, could you check what its output level would be when you reach that excursion ?

Art Welter
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Art Welter

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #21 on: April 07, 2010, 06:45:32 pm »

Tom Reid wrote on Wed, 07 April 2010 08:26

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.

Appears you and Tim Weaver disagree about the JBL distortion  Laughing .

Interesting, the VT4880 uses the  2258H (19mm Xmax), VT4880A uses the 2269H (also 19mm Xmax) both rated at  less Xmax than the 2268 (23 mm Xmax) used in the SRX 728.

The Eminence speakers I have tested meet their X max specifications.

I have not tested any JBL cones to see if their X max figures are correct, but I have no reason to doubt them.

Have you ever looked at the excursion of the speakers in your SRX 728 at “full tilt boogie”?
A white dot on the cone makes it easy to measure the excursion.

Art Welter
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Adam Schaible

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #22 on: April 07, 2010, 07:41:11 pm »

I know that much/any power in the 30hz area makes them sound like total shit (srx 728) .. but this is sine wave's - like 20 volts.  That probably says just as much about the box as the driver, just my experience.  I didn't have the grill off to measure, but it didn't look like 1.75" peak to peak and they definitely distort severely at that level.
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Phillip_Graham

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #23 on: April 07, 2010, 07:59:39 pm »

Art Welter wrote on Wed, 07 April 2010 18:37

David,

The 4018LF has an Xmax of 7.9 mm.
The B&C 18TBX100 has an Xmax of 10 mm.
According to your sim, they both have exceeded Xmax with 2kW.

Art Welter


I'm going to pipe up in Art's defense here, as I think he is correct in supporting the driver in question.

It should also be mentioned that the change in voice temperature is not likely being factored into these simulations, which are based on small-signal T/S parameters.

Raise the voice coil temperature by 150C, thereby changing Re appreciably, and the needed tuning for good performance will have changed dramatically.  Qe has effectively increased, and driver excursion will also increase.

The WinISD simulations presented are not going to give a realistic portrayal of the driver performance at high input voltages.  It will also result in the production of a subwoofer box that will not be properly tuned when driven the way most professional loudspeakers are driven.

The JBL differential drive speakers have quite good thermal performance compared to more conventional designs, if you look at the thermal time constants that JBL publishes for their conventional drivers compared to differential drivers.  Even if the driver Xmax was the same as the other drivers mentioned above, the JBL likely still has a thermal performance advantage.

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Art Welter

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #24 on: April 07, 2010, 08:14:06 pm »

Adam Schaible wrote on Wed, 07 April 2010 17:41

I know that much/any power in the 30hz area makes them sound like total shit (srx 728) .. but this is sine wave's - like 20 volts.  That probably says just as much about the box as the driver, just my experience.  I didn't have the grill off to measure, but it didn't look like 1.75" peak to peak and they definitely distort severely at that level.

20 volts into 4 ohms is around 100 watts.
Was your observation outdoors?
What was the nature of the “total shit”?
Was it frequency dependent?
Box rattle, cone flap, harmonic distortion?
Both cones sound the same?
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Adam Schaible

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #25 on: April 07, 2010, 08:21:16 pm »

Art Welter wrote on Wed, 07 April 2010 19:14

Adam Schaible wrote on Wed, 07 April 2010 17:41

I know that much/any power in the 30hz area makes them sound like total shit (srx 728) .. but this is sine wave's - like 20 volts.  That probably says just as much about the box as the driver, just my experience.  I didn't have the grill off to measure, but it didn't look like 1.75" peak to peak and they definitely distort severely at that level.

20 volts into 4 ohms is around 100 watts.
Was your observation outdoors?
What was the nature of the “total shit”?
Was it frequency dependent?
Box rattle, cone flap, harmonic distortion?
Both cones sound the same?



Was your observation outdoors?
Yup

What was the nature of the “total shit”?
Lots of cone flap

Was it frequency dependent?
Yup, 30hz..ish

Box rattle, cone flap, harmonic distortion?
flap

Both cones sound the same?
yeah


I don't expect it to respond well at 30hz, just saying the extreme xmax didn't seem to help distortion below box tuning.
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Art Welter

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #26 on: April 07, 2010, 09:08:02 pm »

Adam Schaible wrote on Wed, 07 April 2010 18:21


I don't expect it to respond well at 30hz, just saying the extreme xmax didn't seem to help distortion below box tuning.

Below box tuning excursion goes up radically, and ports make flapping noises.
What was the Fb ?
Did you notice distortion above the FB?
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Adam Schaible

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #27 on: April 07, 2010, 09:34:51 pm »

Right, I understand all of the issues below fb ... the cab is fine above fb IMO.  I wasn't downing the box, or the driver.  The point I was trying to make is xmax isn't that big of a deal with the proper box tuning.  XMax doesn't really help above fb .. on some of the subs I've tested/measured, between box tuning and 100hz excursion is roughly 4-5mm peak to peak with lots of power, 1500ish watts.
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Silas Pradetto

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #28 on: April 07, 2010, 09:51:51 pm »

Adam Schaible wrote on Wed, 07 April 2010 21:34

...XMax doesn't really help above fb ...


I guess all those manufacturers got it wrong then....we should all still be using http://www.jblpro.com/pub/obsolete/2220hj.pdf since they're so amazing at producing thumping bass  Rolling Eyes
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Adam Schaible

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Re: anyone built their own cabinet for 2268H subwoofers?
« Reply #29 on: April 07, 2010, 09:53:24 pm »

You really like to take things out of context.

+/- 8mm is fine.  
23mm doesn't seem necessary.
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