SR4725X woofer damage?

[LowPhreak]

I noticed today that I'm getting 2-6+ dB less output on the left-side woofer than on the right, depending on frequency. Both sides are balanced on test tones over 1kHz so the horns seem OK. It's not the upstream components or level settings, those have been checked. The driver sounds OK, not distorted or scraping or buzzing that I can tell, but something is def not right.

Is it a failed component in the X-O, or is the 2226H's voice coil going bad? I'm hoping it might be the X-O, that should be easier to get removed and repaired.

Thanks for any suggestions.

[jcrobso]

Do the easy things first, swap the left/right speaker wires at the amp.
Yes, your channels will be reversed. Listen to the bass did the problem stay on the left side or did it more to the right speaker? What you next depends on the answer to this question. John

[LowPhreak]

As I said, upstream isn't the problem since it's all been checked. The amp is a brand new out of the box today PLX1804, and the one before it was a new 1104 that I had for a couple of weeks.

I went back and ran another set of test tones, and this time I did hear some noise at 160, 125, and 100Hz, but below 100Hz the noise didn't show. Looks like it's the VC.

Wonderful. I've had these cabs only a couple of months, and AFAIK that 1104 was driven into clipping very little if at all. Guess I'll have to be more careful until I get more power than the single 1804.

Getting the rubber trim out of the grill is not going to be easy. I've tried before but it seems that it's hardened up over time and now doesn't want to peel off. Maybe heating it with a hair dryer would work?

[Oldmics]

That 1104 is no where near enough power.

The 1804 will be just fine.Make sure you limit back the power with a good compresser.

Also check the crossovers as they may have taken on some thermal wear issues.

Spray some silicone on the grille rubber and yank it up from the center with a pair of needle nosed pliers.

Oldmics

[LowPhreak]

Thanks for the input, gents.

I didn't have any compression or limiting going on these. This one is my own fault since I certainly know better than using just 300w/side. Might have been OK on my 4412's but not with speakers like these. Plus, not having a HPF didn't help. I was hoping to keep things under control until I got something bigger.

Proves once again that you can't cheat on power or get out of it too cheaply, you can't always catch the peaks with frickin' clip indicators, and you can't always trust- "Clip limiting protects speakers; thermal limiting maintains operation even during abnormal overloads."...at least not once the VC's get well heated up.



Well I'll tell you one thing: at minimum, these are going to get a separate 1104 for horns with the 1804 on the woofers, or something in the 1000+/wpc range per side.

Oldmics, should I test the individual components on the X-O boards for proper values, or do you mean just give them an eye-balling for any heat-related damage? The only other drivers I've cooked were the 10-inchers on some a/d/s L990s (they were fairly notorious for that), and the ribbons on Apogee Stages that were old anyway and needed re-hanging. I've never borked any PA-type speakers until now.

[robertbartsch]

...intersting. So these are the boxes with the 2226 woofs and the 2426 compression drivers; right?

I've had a set for a while and they seem indistructible.

Were your drivers re-coned?

[LowPhreak]

Spray some silicone on the grille rubber and yank it up from the center with a pair of needle nosed pliers.

Oldmics

There was no way to get even a small needle-nose between the grill and the groove where the rubber trim is. Just packed in too flush and tight, so I had to start at the top or bottom end.

I had a HELL of a time getting the rubbers out since, unknown to me, the one side had 2 separate strips (one in front of the grill, one behind the grill) while the other side was a single "U" shaped strip that wrapped around the edge of the grill. It looked like both sides had 2 separated strips and the fronts should pull out out pretty quickly if not really dried out or having bonded to the DuraFlex covering over time.

I applied silicone spray and ran a dull-edged knife down the length of both sides of the rubber, hoping to loosen it up from the grill and the DuraFlex before I tried again to pull them. That alone was a tough, knuckle-bashing exercise.

After this, I was still tearing off short pieces of the U-shaped strip. Now I'm thinking it was really stuck in there...until I went to the other side hoping it might be a bit easier, where to my surprise and at long last the whole front strip came out in one piece. It wasn't until I finally got the grill off that I saw how both sides were different.

And that was just the left cab.

JBL says nothing about this in the manual or exploded diagrams. All that's shown is: "Trim, Grille (2) 382-00336-05", and one strip per side pictured...instead of 2 separate strips on one side and 1 U-strip on the other I would say those should have different part #'s and/or should've been illustrated as such, because they are not the same parts!

On the right cab, I found the '2 separate strip' side (which naturally, was the opposite side than the left cab's was ) and got that freed fairly quickly so the grill was hanging like a door on a hinge. But then getting the edge of the grill pulled out of the U-shaped strip was quite difficult. It required such force & finagling that it was a miracle the grill wasn't bent beyond use.

So not counting the wasted time, frustration, and scraped knuckles, now of course I'll need to order "Trim, Grille (2) 382-00336-05" if I want to re-install the grills - IF they're still available.



It might not be popular to say it here, but I will anyway: I don't know what geniuses at JBL designed that grill scheme, but they apparently weren't thinking of those who may have to disassemble it later on. Yes it looks great - all very neat, clean and solid when installed. But if I'd had to tolerate that nightmare in the field when I needed to do a relatively quick component replacement, I'd probably have killed the next JBL rep I ran into!




/rant over