ported heresy mod...

[DrWho]

A single 4" diamater port isn't that large...I was picturing a huge
slot. However, you said you've got bends in it? Could you sketch out
your design?

As far as knocking on the squawker....keep in mind
that the energy contained in your knuckles is orders of magnitude more
than even the most insane SPL's will put out. For example, does a
portable wheel chair ramp need to be able to support the weight of a
cement truck? Certainly, if the ramp could hold up the cement truck,
then surely it would be suitable for a wheel chair ramp, but not all
wheel chair ramps need to be holding up trucks. All that to say, IF
your horn walls were strong enough to handle the stimulants from the
speaker, then what does it matter that it fails against knuckles?

I'm
not trying to say that rope caulk is going to be a magic fix, but the
few times I played with it, it had very little if any effect. Thinking
about it, it seems all you're doing is adding some lossy mass, which
actually lowers the resonant frequency....ideally you would want to
raise the resonance up and out of the audible band. I believe Roy or
some engineer once mentioned that the Cornwall squawker could have been
better damped to deal with the pressure waves coming from the woofer
section (not the squawker)...

As far as stiffening up the
cabinet, similar thoughts apply. Every time you cut the free radiating
area in half, you move up the resonance an octave....so if you do
cross-bracing through to the middle of the panel walls, then you gain
the most. And if you couple the cross members well, you increase the
amount of damping too.

Also, check for air leaks...and make
sure all your compression drivers are tightly fastened to their horns.
In fact, you can track down a whole heck of a lot of problems with a
sine wave generator that you can continuously sweep. Slide it around
until you hear things buzzing and rattling and you'll know where there
are problems to be fixed. Any horn resonance issues will show up with
this too...and I might even be willing to wager that the horn itself
isn't the problem []

Sometime this extended weekend I might
be able to run some simulations on your box. Depending on the driver,
many of the parameters tend to be very forgiving of wide tolerances.

[Rockets]

A 4" port looks big as hell when you're in the store and mentally trying to size up fitting it into a rather small Heresy box...at least for me it was. The port I'm using is basically 3" PVC w/ one 90 elbow that I shortened on one end to fit as flush as possible against the back wall. overall length including the bend is about 9 to 10 inches. It's epoxied in place w/ DP190.

As far as the Hall effect. I was all set to say that I thought it's the diaphram or driver. I say this because I pulled the woofer out and replaced it w/ the dead K-24. I ran a wire out thru the port to connect to the external JBL 2213H for amp loading purposes. No change in the Hall effect. Plugged the port, No change. Pulled the midrange and roped it. No real change. And then as I as standing over the woofer, it was quite apparent who the offensive party was. I'm shocked really. Not that you were right, but I really didn't expect it out of this woofer. I can't believe L100 owners have never posted about this on the other board. Given the L100 has such a great reputation, this just doesn't add up for me. The fact you had similar results with the Klipsch driver, makes me think I'm just missing something. One thing I could and probably should do is put the 2nd order 700hz kill switch back into the woofer circuit. I had forgotten the roll off on the JBL was around 1200 hz, and some reason I thought it was much lower. This may help on two fronts, but doesn't solve the entire riddle for me.

Marvel, do you ever crank up your 4311's?? Ever notice any hall effect coming out of them?? I'm guessing I'm hitting 75 to 80 watts when it starts to become apparent. I can't imagine what it'd sound like if I had a bigger amp. Maybe I need to take it outside...[H]

For what it's worth, I didn't cross brace. I implanted some 1/2" plywood. Screwed and glued to the internal sides..

No air leaks. I replaced all the weather stripping around the speakers.

That's it, that's all I have for now.

Thanks

TC

[DrWho]

Wait, you've got no lowpass on the woofer? []

[Marvel]

Wait, you've got no lowpass on the woofer?

I think that is the way JBL ran them on the L100s and 4311X series. I have often thought of changing my 4311 crossovers (they at least need the caps replaced... they're from '72).

I haven't fired them up for a while, but never had them hooked up to anything over 35wpc, so I was never driving them very hard.

Mike, can you explain what the Hall Effect would do in a speaker system.

Bruce

[Rockets]

I told you...I was a hack...[]

No, I ran them straight out like the L100 and let them die a natural death. [*-)] My memory evidently isn't what it should be, and I thought they died at a much younger age... I looked them back up this morning and realized this could be part of the issue. So yeah, I could kill them off to match the mid at 700 hz. That will no doubt help, but not fix the entire range. The more I listen though, I know I need to do this, even if it doesn't cure the hall effect.

The BIG question is, how can JBL get away with running this driver out to 1200 to 1500 hz at 150 watts in a similar sized ported box and I can't? Even if I were to unplug the MF and HF I would still have this Hall effect. This would lead me to believe the issue is inherent to the driver, but I think I know better, or at least refuse to believe it's the driver..

If I understood you right, you had similar Hall effects w/ the K24 and w/o modifying the stock crossover, correct?? So it's not just a matter of the crossing over at 700hz right? The cause is really a time delay right?? It's not a polarity issue, or is it? I've read conflicting info on connecting the JBL 2213H, where one report is it's positive, the other says it's negative and another says it doesn't matter, so I blew it off.

Maybe, I'm just expecting too much. When I switch over to my LaScalas, it's not just a night and day difference, it's the whole damn Universe!

Thanks

[Marvel]

The 2213H is positive on the black. That needs to match the polarity of the K-24. It will make a difference. Bob C. can probably tell you the polarity of the K-24. JBL was an oddball with their wiring. Most drivers are/were made with the positive on the red.

Something is certainly wrong. My 4311s sound pretty close to my HIIs... JBLs = more bass, lower sensitivity. The overall sound in MY livingroom (13 x21) sounds really good. The Heresy IIs and LS just sound better.

[Rockets]

Thanks Marvel, I'll flop them and see. I'm not expecting a miracle, as I've read they're rather bi-sexual, and really don't care how you hook them up. Here they tell you to reverse them http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L100A%20ts.pdf and of course now when I want it, I can't find it...the JBL link that says you can wire it either way. []

I'll put in an order to PE today for the crossover parts...not looking forwad to ripping these speakers back apart to do the mod though. I guess I'm not convinced it's going to cure the problem, tame it yes, fix it no. It should cure another issue, or so I think, with the mids sounding so proud.

For S&G's I did run some test tones through them. As expected 25hz was fairly weak, but got progressively better as it went up the scale.

Thanks for your input.

TC

[Rockets]

Just a follow up. Went back to the Heresy crossover for the woofer, and it has definitely helped. The hall effect is still there, but to a lesser extent. The louder you crank them the more noticeable it becomes, plugged or unplugged it doesn't matter. I don't think there's anything else I can do, short of finding another woofer, to correct it, and I don't think using a K-24 is the answer.

As far as the porting for gains in the lower end, I'm happy with the results. I wish I could measure the output in order to share the results, but I'm not able to.

[Marvel]

You may just be cranking the wookfer a lot more than most users would. I bought my 4311s new from a studio close to where I lived, and they borrowed them from me one weekend, while recording a Styx album. The studio had some huge EV monitors that the band wasn't familiar with, and wanted to use my JBLs as a reference. The control room wasn't huge, but I don't believe they had them up too loud.

Bruce

[Rockets]

Bruce, I totally agree with you that most, myself included, wouldn't normally push them that hard. For my intended purpose, they will do fine. Still, I had thought about loaning these out to someone who probably would, and I just don't think they're up to that job. Many people wouldn't notice, but I do. A Cornscala would be a much better choice for him, but I don't have one of those to audition either.