Questions about modelling JBL 2226J

[penngray]

New to this forum...I now own 4 JBL 2226Js and 2 JBL 2225Js, I also own the JBL 2" CDs (I forget which model) that Im mounting on a IWATA-300 horn (LeCleach design from DIYAudio.com).

I have questions about the JBL 2226J.

I had some trouble with getting WinISD to accept the 2226J T/S parameters found on JBLs pdf but I think I have it working but does anyone else have the 2226J setup for WinISD so I can confirm they are right.

Also looking at the ported model it shows that the small ports have port velocity issues. The only model I could get the port velocity below 32ft/sec was using dual 8" ports.

Of course I wanted to just follow the 4648-8 enclosures which are 8 cu. ft, 40 hz tuning but the model tells me those ports will have huge noise issues....what gives??

[penngray]

Sorry I forgot to post that the ports in the JBL 4548a-8 are 5.25" x 4.5", I modelled that box with those two ports with 300Watts and the port velocity is > 70ft/s which is more then double the 32ft/s velocity that I was taught was safe for hi-fi port noise.

[grumpy]

...might look at the resulting loudspeaker produced SPL for the same input level
that produces 32ft/sec velocity in the ports... (>125dB?, 1000+ watts? ... using 8" ports)
Then try to figure out how loud 32ft/sec is :)

Here's a fun read:
http://www.subwoofer-builder.com/flare-testing.htm


(also, I'm not sure I'd classify the 4548 as a 'hi-fi' box ...)

[penngray]

Yes, 120+dB is loud but for an HT room with 20foot listening distances movie peaks can produce that output so Im just trying to make sure my design meets certain requirements.

I understand the JBL 4648 is not really a "hi-fi" design but there are many, many happy owners out there, even HT room owners so Im questioning my model more then anything.

[grumpy]

sure. I've a pair of 4645 cabs with 2242's installed, so I get the loud peaks thing :)
I've never heard port chuffing on non-test-tone-like material though. If you roll off
below the port tuning (40Hz in your example) it will also help reduce the excitation
that produces 'chuffing'.

The models in WinISD seem to be pretty reasonable most of the time.
What parameters did you modify to get WinISD to accept the parameter group?

[penngray]

Here are the WinISD parameters.
51834

Btw, I added a HPF @ 35 Hz and yes, it drops the port velocity some but with the 5" port its still around 50 ft/sec. I guess we do not hear that during split second peaks.

Two 8" ports 12" long in a 8 cuft box seems to model nice for me so I might try that size instead of a JBL 4868A clone.

Thank you for taking the time to reply :D

[Titanium Dome]

If this is the same penngray (can there be more than one :dont-know: ?) who asked


btw, are you able to measure the impulse of your K2?? There is a design discussion that a measurement of the K2 would help a great deal.

over on AVS (I'm filecat13), then grumpy is the guy who can do what you asked.

As it turns out, he's coming over on Friday to help me set up some 4-way actively quad-amped JBL L250s reborn as PT250s with inverted dome Ti drivers. :eek: He's got the gear to give you what you want if you're still needing the info.

Otherwise, carry on! :drive:

EDIT: By "help" I mean he does the thinking, I do the lifting and supply the components.

[penngray]

:D Yep, that would be me.

Im building my own K2 type clone with TAD CDs, larger horn and these JBLs.

[grumpy]

If we have time to do some K2 tests, I'll post 'em.
Maybe you could PM a specific question or pointer to the AVS conversation
so I know more precisely what you're after.

Re: dual 15" cab, you might leave room for ports a few inches longer
(or provide a curve in the port design) to ensure that you can extend them a bit
from your model's simulation. I put similar (chose slightly different) 'hard' parameters
to enter into WinISD's T/S input screen and the 40Hz/8ft3 tuning with dual 8" dia ports
showed ~15". Nice to measure individual drivers and simulate with those values,
but even that usually deviates from reality.

[penngray]

The question was about K2 horizontal and vertical polars. I can not remember the thread off hand right now.