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Author Topic: Win ISD and JBL 2241's  (Read 6000 times)

scott foster

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Win ISD and JBL 2241's
« on: February 12, 2007, 07:43:56 pm »

I have four spare JBL 2241H's and I'm thinking of building four single-18 boxes for them.  I started with Win ISD and Win ISD Pro for a simple reflex design. Can anyone comment on the default Win ISD designs or point me to a better box plan for that driver?  Would consider any style.  Boxes would be used for 100-150 head pub gigs under 3-way top boxes.  

In the case that there is not really any better option,  playing with WinISD, I see that simple ported boxes between 8 and 13 cu. ft. with tunings from 35hz to 40 hz will work reasonably well.  Any tips on what trade offs are best with this speaker?  Could  I go with a lower frequency extension and accept lower power handling and higher excursion or is it more important to keep excursion low and not try to push the design too low?  Should I just stick with the WinISD default for this speaker?  

Looking at the graphs I see that for the main frequencies, as excursion goes up and power handling goes down that impedance rises.  Does that mean that in a "live" setting an appropriate sized and hi passed amp is not going to really be likely to push excessive power into the design anyway?

Any help or opinions welcome.
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Paul O'Brien

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Re: Win ISD and JBL 2241's
« Reply #1 on: February 13, 2007, 10:11:00 am »

Once the driver starts exceeding xmax distortion increases dramatically. And as you have seen with WinISD Pro there is a rise in excursion above tuning frequency, the trick is placing it to have the least impact on the intended use for the speaker system. If the box is tuned too low then this excursion rise could be right in the meat of a bass guitar or kick drum range, and that will not be good because you want as much power handling as possible for these instruments. Raising the box tuning will decrease the excursion and increase power handling, but obviously raising too much will cost low end extension. Generally a 3db point of 35-40hz is fine for live sound, this should result in a box size with good power handling while being reasonably compact. I wouldn't go any larger than 8cu ft personally.
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Dave Rickard

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Re: Win ISD and JBL 2241's
« Reply #2 on: February 13, 2007, 12:58:21 pm »

I've only used ISDonline, not WinISD, but I assume they're very similar.

I found that you can reduce the "recommended" box size by 15% or so and still get similar performance while reducing size and weight.  Tune to compensate.  Consider tuning to get that small "bump" (1-2 dB) before the dropoff and maximize efficiency.
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Dave
Yorkville dealer

"The wrong piece of gear, at the right price, is still the wrong piece of gear."

"If you don't have good stuff at each end of the signal chain, (mics and speakers) what you use in between is just turd polish."--Dave Dermont

Elliot Thompson

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Re: Win ISD and JBL 2241's
« Reply #3 on: February 15, 2007, 07:44:37 am »

scott foster wrote on Tue, 13 February 2007 00:43

I have four spare JBL 2241H's and I'm thinking of building four single-18 boxes for them.  I started with Win ISD and Win ISD Pro for a simple reflex design. Can anyone comment on the default Win ISD designs or point me to a better box plan for that driver?  Would consider any style.  Boxes would be used for 100-150 head pub gigs under 3-way top boxes.


When I used to use WinISD, it had issues with the accuracy of the Port versus Frequency Tuning.

The Pro version seemed to address the problem.


Don't try to attain a flat frequency response using the 2241 to 40 Hertz then having it roll off gradually. That will require a very large cabinet. You might want to take advantage of the cabinet gain when housing them in less than an optimum sized enclosure. The end result will be a higher sensitivity rating when comparing the 1 watt, 1 meter or 2.83 volt measurements to others.

Quote:


In the case that there is not really any better option,  playing with WinISD, I see that simple ported boxes between 8 and 13 cu. ft. with tunings from 35hz to 40 hz will work reasonably well.  Any tips on what trade offs are best with this speaker?  Could  I go with a lower frequency extension and accept lower power handling and higher excursion or is it more important to keep excursion low and not try to push the design too low?  Should I just stick with the WinISD default for this speaker?


As far as I remember, 35 Hz is the FS of the driver, and it would be best if you don't go lower than that.

There's going to be a compromise no matter what.

1.JBL 2441 requires a good sized cabinet to offer a lot of SPL
around 40 Hertz without taking EQing into factor.

2.The FS is pretty much standard like the majority of 18 woofers in the market (35 - 30Hz) and relies more on cabinet size to attain those frequencies.

As for excursion, I would it wouldn't be a major factor unless you build a 16 cubic foot cabinet for a single 18, and tune it below 35 Hertz.

The fact is, the smaller chamber will not only restrict the low frequency response, but prevent over excursion at those lower notes.

Quote:


Looking at the graphs I see that for the main frequencies, as excursion goes up and power handling goes down that impedance rises.  Does that mean that in a "live" setting an appropriate sized and hi passed amp is not going to really be likely to push excessive power into the design anyway?

Any help or opinions welcome.


Read my above comments. Cabinet size can prevent over excursion or enforce it. Guys who are always concerned with excursion is trying to get every ounce of SPL from the woofer. I can't say I ever agreed on that method for, it comes at a cost. The cost being distortion. It's far better to have four woofers driving
50% of their capacity, than two driving @ 100%

It's a quality issue that many tend to forget is the object of the game.

Best Regards,
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Elliot

robwells

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Re: Win ISD and JBL 2241's
« Reply #4 on: February 15, 2007, 04:14:38 pm »

JBL's recommended enclosures here:

http://www.jblpro.com/pub/manuals/enclgde.pdf

Rob.
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scott foster

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Re: Win ISD and JBL 2241's
« Reply #5 on: February 20, 2007, 10:01:33 am »

I had forgotten about the JBL published cabinet data sheet - I actually had that laying around.  The JBL recomended design is virtually identical to the WinIsd result - around 10 cu.ft. and 40hz tuning.  Thank you all for the input/replies.  
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