Damaged 4430 driver?

[duaneage]

I am betting on cold solder joint somewhere or even the L-pads. Try both drivers on each crossover. If both drivers have the same notch on one xover eureka!


Vibration inside the cabinet (there is plenty of that!) may have shaken a solder joint loose. A resistor could be damaged, check the resistors on the board.

[Zilch]

Notch is not the problem. That was an artifact of having the mic too close to the throat.

The problem is (was) lack of HF extension....

[sfellini]

...run a wire to them from one of your crossovers.

Quick question: do I get to the xover by removing the 2235 or from
the back?

[Zilch]

For what you need to do, just remove the woofer.

I am sorry the idiots chipped your magnets. Of all people, they should know how to handle these....

[sfellini]

Now run a wire to them from one of your crossovers. Substitute an 8-Ohm resistor for the woofer in that cabinet. Test both drivers on that one crossover. Then repeat with the other crossover.

Click that crossover "Int/ext" switch back and forth a couple of times to be sure dirty contacts there aren't a problem.

I've done the above tests. First of all, identical results were obtained
before and after clicking the int/ext switch for each crossover (not shown).

Here are the results for LL0, LR0, RL0 and RR0, where the first letter
is the Left or Right crossover, the second letter is the Right or Left driver,
and the digit is the HF setting on the xover.

Note that for a given driver, there is more output above 8k in the Right
crossover. HOWEVER, with a +1 dB boost in the HF control, they look
pretty similar (see the following post).

Also, for a given crossover, the Right driver seems flatter in the 3-6k
region (I didn't try compensating for this with the MF control). I should
try this because previous results show the drivers are identical without
a crossover.

Together this means the LL combination should give the worst response
and the RR the best, and this is in fact the case (no wonder the two speakers measured different).

[sfellini]

HOWEVER, with a +1 dB boost in the HF control, they look
pretty similar.

Here are some more FRs, showing the effects of boosting the HF control.
One complication: on the Right crossover, the +1 dB stop is as far as the
control will go, so it's probably really +2 db?

LL1, LR1, RL1, RR1:

[Zilch]

Well, you're lookin' quite good, actually. Compare to reference:

http://audioheritage.org/vbulletin/s...page=1&p=64993.

If you pull the mic back to 1M, I think you'll find the response to be smoother.

So, your right crossover has been boosting the HF about 1 dB, because the control is not aligned with the front panel markings.

I just checked, and the control board is mounted from the front panel with screws under the foilcal. You might be able to reach in from behind and rotate the HF control that little bit if it's slightly loose.

The knob itself is 3/8" deep, and can be pulled off from the front with an IC extraction tool which will hook under the rear edge of the knob. That'll let you put it back on in the correct position, if that's important to you. If you damage the knob, though, replacements do not seem to be available from JBL parts.

[sfellini]

Well, you're lookin' quite good, actually. Compare to reference:

http://audioheritage.org/vbulletin/s...page=1&p=64993.

Yeah, it was pretty ugly. I think much of it was due to incorrect
measurement methods. Having the drivers on the floor and
having the mic hang over them is way more precise than trying
to point the mic at the speaker on a makeshift boom.

Zilch, you've been a great help, and it was a good learning
experience. Way more to go... .

Thanks again,
Steve.

[Zilch]

Stand and mini-boom I use was like $25 at Guitar Center. Nicely adjustable for height and angle.

It looks like you've zeroed in on part of the problem, at least, and perhaps corrected some of the rest of it in the process.

Remount the drivers in the cabinets and do a final test.

[sfellini]

Remount the drivers in the cabinets and do a final test.

Got my tripod & boom.

So to conclude this thread , here are the final results
(L & R at 24"). And to answer the question asked in the
thread's title: "no" .

(Now, how does one accurately measure bass response
with the RTA? ).

Steve.

[Titanium Dome]

This has been helpful to me as well.

Thanks to all participants for a constructive thread.