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Doc Mark
05-13-2008, 06:55 AM
Greetings, Friends,

For a while, now, I've noticed that one of my 4408's had an intermittent problem. Now, and then, the volume drops markedly, as if there's a short in the system, and I hear a buzzing noise, which sounds like distortion! I found that, if I cranked up the amp a bit, the signal seemed to "fight it's way through" whatever is causing the problem, and the program material returns to normal, for a short bit. At first, I though it might be my EQ, so I swapped out my Audio Control 101 for an old MXR 15 band stereo EQ I had downstairs. Didn't do anything.

Now, I'm thinking I might have a cold solder joint in the crossover of that 4408. I'm planning on removing it, and giving it the once-over, to see if I can spot something amiss.

Does this problem sound familiar to any of you? Am I on the right track, checking out the crossover? Any comments, or suggestions, will be greatly appreciated! Take care, and God Bless!

Every Good Wish,
Doc

P.S. Right now, I'm using a pair of JBL 2500's that I scored at a swap meet for $30, and though they sound nice, they are a bit "thin" when compared to the 4408's! ;)

grumpy
05-13-2008, 08:07 AM
Swap 4408's (L/R) and see if the problem follows (isolate from electronics).

I'd -guess- a failing voice coil but go to:

http://www.jblpro.com/search_22.htm

select www.jblproservice.com, and enter your model (4408)

you should see a link like this:

www.jblproservice.com/pdf/Studio%20Monitor%20Series/4408.pdf

that shows details of your monitor you can use to help troubleshoot.

(Of course, if in warranty, take it in...) :)

Don C
05-13-2008, 09:49 AM
Didn't the first version of the 4408 still have a L-pad? If so, I'd suspect it first.

grumpy
05-13-2008, 10:38 AM
yep. :yes: ... I made the leap that a 'marked' change in sound level might not have
been a loss of tweeter output, but it's sure easy to give it a tweak :)

Doc Mark
05-13-2008, 02:12 PM
Hey, Guys,

Many thanks for your thoughts on this situation! I'm going to swap the woofers in a few minutes, and give them a play to see what happens. At first, I thought my problem was with the tweeters, as the L-pads ARE a little scratchy. But, of late, I've begun to suspect the entire system, which is what lead me to believe that the crossover might be a fault, or at least the connection to the speakers. In any case, I'm going to see, and will report back with my findings.

I had the 8" woofers reconed by Orange County Sound, a few years ago, and have been using them ever since, as part of my bi-amped subwoofer/satellite system. As they have never seen a full range signal, having been crossed over at 90HZ, I surely hope that the voice coil is not the problem. But, I guess stranger things have happened, eh? When I found my LE10A's, I also took them into Orange County Sound, along with my 2235H's, to be re-foamed. The Tech who did the 10" drivers let a screwdriver slip, and sliced a cut into the cones of my drivers!! :blink::blink: OCS told me about the problem, and also that they had fixed it, and hoped it would be OK with me. What they had done, was to glue the split, and then cover the entire cone of that driver, and also it's twin, with some kind of coating. At the time, I said that I "understood", and just took delivery of my drivers. Since then, I've had second thoughts about that, and probably should have refused the "fix", and asked them to do the job again, from scratch.

Oh, well...... too soon old, and too late smart, eh?!! ;):):blink:

My "new" Crown DC-300A arrived today, too, safe and sound, and I'll be testing that amp, too, along with the woofer swapping for the 4408's. I'll keep my fingers crossed on both counts, and will report any findings back here. Thanks, again, Friends, and God Bless!

Every Good Wish,
Doc

grumpy
05-13-2008, 03:22 PM
I'm going to swap the woofers in a few minutes

Doc... I was thinking swap the whole 4408, or swap speaker wires on the back of your
amp, but perhaps you've already tried that? (make sure it's not the electronics). :)

Doc Mark
05-13-2008, 05:13 PM
Doc... I was thinking swap the whole 4408, or swap speaker wires on the back of your
amp, but perhaps you've already tried that? (make sure it's not the electronics). :)

Hi, Grumpy,

Well, shucks, and darn, and heckuba!!! Looks like that one 8" JBL is definitely the cause of my buzzing, and intermittent sound!! If I touch the cone, it gets good again, only to drop out again, very soon. Hard to believe that what I would consider a relatively fresh recone job, would go South so quickly, especially when it's only seen signal above 90HZ. But, that certainly does seem to be the case.

I guess I'll have to take a trip down to Orange County Sound, and get this reconed, yet again, unless you can suggest a better place. I note that you are from So. Cal., too, so if you know of a better reconing shop, I'm all ears. I live up in the mountains above the Inland Empire, and it's a drive to OCS. 'Course, I'll make that drive, if I have to.

Right now, I've removed the 4408's, and replaced them in my system with a pair of satellite speakers I made many years ago. I used Peerless drivers, a 6" Polypropylene woofer, and a 1" fabric/coated tweeter, crossed at 4KHZ, in a sealed box, and they sound very good, actually. So, at least I have something to play our music until the 4408's are once again up and running.

I also tested the Crown DC-300A, but should post that info on the thread about such things. I'll do that in a bit.

Thanks, again, for your help, Grumpy! One of these days, we'll have to meet up, and I'll treat you to lunch, as a way of saying, "Thanks!" Take care, and God Bless!

Every Good Wish,
Doc

mech986
05-13-2008, 06:14 PM
For a little closer shop, check out our member Edgewound aka Ken at Upland Loudspeaker services in Upland north of the 10 fwy. Check this JBL Pro site for the address and phone contact number.

http://www.jblproservice.com/service/california.html


Lots of SoCal LH members have used him and his work is very good.l

Hope it works out.

Regards,

Bart

Doc Mark
05-13-2008, 07:35 PM
For a little closer shop, check out our member Edgewound aka Ken at Upland Loudspeaker services in Upland north of the 10 fwy. Check this JBL Pro site for the address and phone contact number.

http://www.jblproservice.com/service/california.html


Lots of SoCal LH members have used him and his work is very good.l

Hope it works out.

Regards,

Bart

Hey, Bart,

Many thanks, Sir!! I am going to check with Ken and see if he can help me with the recone of the 8" JBL, and also have him check that 2242HPL I bought a few weeks ago, if he has time to do that work for me. Many thanks for the tip! Take care, and God Bless!

Every Good Wish,
Doc (who has to go cook some dinner for Sweet Bride and himself!) ;):D

grumpy
05-13-2008, 08:26 PM
Ditto re Bart's comments about Upland Loudspeaker Service.
... been very happy with the quality of work there. Sucks about
the woofer, but sounds like you found the culprit. :)

subwoof
05-13-2008, 08:30 PM
check the tech manual - the crossover point is a LOT higher than 90hz.....

As for the intermittent, have a JBL service station resolder or replace the Litz wires. This intermittent is a common problem when the cone has had high excursion and/or was reconed bu someone with poor soldering techniques.

EASY fix....

sub

Doc Mark
05-13-2008, 10:55 PM
check the tech manual - the crossover point is a LOT higher than 90hz.....

As for the intermittent, have a JBL service station resolder or replace the Litz wires. This intermittent is a common problem when the cone has had high excursion and/or was reconed bu someone with poor soldering techniques.

EASY fix....

sub

Hey, Sub,

What I meant to say is that I've been using the 4408's as satellite speakers, crossed over, electronically, at 90 HZ, to the subwoofers. So, excursion has been very limited to those 8" woofers, and it's hard to see why either of them might go South, given my usual light listening volumes.

I will check the Litz wires, as you suggested, or take them to Ken, and have him do it. Sounds like you might be onto something good, there, or at least I hope so.

I must admit, though, my old Peerless system, which I hooked up tonight to replace the JBL's, sounds clean, clear, and wonderful!! I'm pleased, and they will do the trick until my old JBL's are back in the saddle, one way, or the other. Thanks, again, Lads, and God Bless!

Every Good Wish,
Doc