jbl 4310 - bad bass

[paulnparis]

Hello,
I picked up a pair of JBL 4310s off of ebay..
One speaker sounds fine, but the other sounds as if the bass is non-existent, but sometimes comes in a little on the peaks but is distorted, a bit buzzy. It doesn't come in strong at all.
Should I investigate replacing the electronics or a capacitor?
Or has the voice coil dropped?
Or am I way off..
I appreciate the help trouble-shooting and getting the speaker back to producing good sound.
Thanks in advance, Paul

[domtw]

Salut!
First, I would exchange the bass drivers. This will help you to find out if it comes from the driver or from something else...

[chris661]

Hmmmm....

Could be...

Bad connection to speaker
the speaker isn't mounted in the box properly
your amp's blown
there's something wrong with the driver

So, check connections, make sure the speaker has no gaps around it when it's in the box, try a different amp/different channel on the same amp, then take the driver back...

[pos]

You can try to permute the woofers between the two speakers, to discover if the problem comes from the driver or the filter.

[kevinkr]

If the woofer is indeed bad you will need to come to some understanding quickly with the seller - if that is not possible file a grievance with eBay and/or Paypal as appropriate. (Do this immediately if there is anything in the seller's attitude you do not like.)

Presumably the amplifier was fine before these speakers were connected, still just to be safe swap amplifier channels.

It is more than likely that the woofer voice coil has been burned up - swapping woofers from one cabinet to the other would confirm that the woofer is malfunctioning. Should this woofer prove to have a fried voice coil (verifiable with a DMM) you might want to replace the pair as it is likely in a stereo pair that the other has suffered the same level of abuse.

Also check the condition of the woofer surrounds.

Another possibility is a bad connection or a failed component in the cross-over, swapping drivers will definitely confirm or eliminate this as a possibility.

[paulnparis]

Hello Kevin, pos, Chris and domtw,

Thanks for the quick replies.

I failed to mention a couple things;
1) I was trying out an old SS amp my son found in the street in Paris. (He seems to collect any garbage..) I tested it on just this one speaker, and it emitted a hum (bmmmm), fairly loud, but not so loud that you'd turn it off right away. (At least not me.) On the other channel we got sound, but there was no bass, and we assumed it was the amp..
2) we did try inverting the channels on the regular amp, and the woofer was bad on both.

Following your advice I changed out the driver.. and it's confirmed that is the problem.
Also using two hands to push gently on opposite sides of the cone, you can hear a noticeable rubbing noise.
And of note, when the (regular) amp comes on, the speaker pushes out and makes that noise, then goes back to it's centered position after a few seconds, making the noise again. The other driver does this too, but doesn't make any noise.

I measured the bad driver (disconnected) resistance at 6.4 ohms.
I'm not sure what that means - I think it means it's not dead yet but something isn't right.(?)

I actually got these last fall.. For a time they sat since I had no amp here in France.. only one in the U.S. which I'll pick up this summer.. Then we found one.. and it's only since yesterday that I noticed the bad bass. Maybe it was there before and I didn't notice it because the other covered - I don't think so though.
Maybe I'm wrong but I don't really suspect the seller to be at fault.

Could the amp I tested yesterday have sent AC (is that right?) to the speaker and caused damage to the voice coil?

Kevin, what is a DMM? (Sorry my level is basic. I've built a guitar amp...)

In any case I've got a bad woofer, 2212 and either need to get it repaired, or a new one. Anyone know of a reasonable cost place near Paris, France?
There's this site, http://www.reparation-haut-parleur.c...t-parleur.html
but they don't mention JBL or vintage speakers..

In England I saw Wembley,
http://www.wembleyloudspeaker.com/

Any recommendations?

Thanks, Paul

[tritosine]

get factory recone kits from USA (wont be cheap), or 2 aftermarket ones and redo both. After you received find someone with good hands and get it reconed there.

[tomtt]

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[kevinkr]

Originally posted by paulnparis
Hello Kevin, pos, Chris and domtw,

Thanks for the quick replies.

I failed to mention a couple things;
1) I was trying out an old SS amp my son found in the street in Paris. (He seems to collect any garbage..) I tested it on just this one speaker, and it emitted a hum (bmmmm), fairly loud, but not so loud that you'd turn it off right away. (At least not me.) On the other channel we got sound, but there was no bass, and we assumed it was the amp..
2) we did try inverting the channels on the regular amp, and the woofer was bad on both.

Following your advice I changed out the driver.. and it's confirmed that is the problem.
Also using two hands to push gently on opposite sides of the cone, you can hear a noticeable rubbing noise.
And of note, when the (regular) amp comes on, the speaker pushes out and makes that noise, then goes back to it's centered position after a few seconds, making the noise again. The other driver does this too, but doesn't make any noise.

I measured the bad driver (disconnected) resistance at 6.4 ohms.
I'm not sure what that means - I think it means it's not dead yet but something isn't right.(?)

I actually got these last fall.. For a time they sat since I had no amp here in France.. only one in the U.S. which I'll pick up this summer.. Then we found one.. and it's only since yesterday that I noticed the bad bass. Maybe it was there before and I didn't notice it because the other covered - I don't think so though.
Maybe I'm wrong but I don't really suspect the seller to be at fault.

Could the amp I tested yesterday have sent AC (is that right?) to the speaker and caused damage to the voice coil?

Kevin, what is a DMM? (Sorry my level is basic. I've built a guitar amp...)

In any case I've got a bad woofer, 2212 and either need to get it repaired, or a new one. Anyone know of a reasonable cost place near Paris, France?
There's this site, http://www.reparation-haut-parleur.c...t-parleur.html
but they don't mention JBL or vintage speakers..

In England I saw Wembley,
http://www.wembleyloudspeaker.com/

Any recommendations?

Thanks, Paul

"DMM" - Digital Multi-Meter..

Your voice coil is burned up, and it is conceivable that the amplifier you found in the street burned it up - due to there being large amounts of dc present on the output. The hum you mentioned is a big clue.. You can use your meter set to a dc voltage range to verify this. (No speakers connected!!!)

6.4 ohms is about right for the dcr of an 8 ohm woofer, however I assume the coil has overheated and the glue holding it to the voice coil former has burned and expanded - this is what is causing the rub you can feel. (You did the right test to check for this.)

Incidentally a standard recone kit is NOT going to do it, you need the whole moving assembly including the spider, voice coil, cone and surround. Such kits are available, but expensive and require great skill & patience to do it right. (I have done a few with mixed results.)

Get the parts from JBL (I'm assuming that they are even available) and have someone who does this sort of work professionally do both speakers for you. Alternatively just find someone with a good set of woofers to sell on eBay - might be a safer and cheaper bet.

FInally put that amplifier back out on the street or get it fixed if it is something worthwhile..

[paulnparis]

Thanks everyone for the prompt and informative advice - really great!

Kevin, Just for my own knowledge and confirmation, I will measure the DC voltage of the left channel of that old amp.

As you all can imagine, I feel very stupid and bad about this experience (of possibly having destroyed a great driver)...

A few questions for me to get educated -

1) I read somewhere and have done it - use a 9V battery to check and be sure which connection is positive on the driver. The positive side of the battery connected to the positive to the speaker causes the woofer to push out away from the speaker. (I've done this on both guitar amp speakers and hifi.)
Is 9V (DC) OK for a short period going to a woofer?
What amount of DC voltage would typically cause a woofer voice coil to burn up?

2) Would a pair of 123-A be an acceptable substitute for the 2212, for the 4310?
What would the difference in sound be?
Is it important to get a matched pair - same dates, or something like that? (Sometimes the 2212 is sold independently, just one..)
What about a 2212 and a 2213 - are they close enough?

I should mention that I purchased an EICO HF-81 but it's sitting in the U.S. currently. Plan to replace the capacitors...
So I think I need light responsive woofers, vintage type..

At some point I may get the driver fixed, but first want to find someone qualified and reasonably priced..
I take it that it's important to do both at the same time, otherwise one may have a tighter bass than the other.?
For the moment I'm leaning towards purchasing a pair..

Thanks again for all the advice...
...and I promise from now on I'll look at material with $ sign in my eyes before I start testing out unknowns.

Paul