LS90 Woofer Failure

zruben

Hey Guys, long time lurker here. I recently had one of the drivers go out on my LS90. Took out the old one and found no obvious signs of separation, but it does make a buzzy sound at certain frequencies especially when listening to music with a lot of dissonance.
Just wondering if anyone had some insight to what could be causing this, maybe a possible fix? Or if I should just rather look at getting a replacement for it. If so, where would I go about getting that?
Thanks! --Zach

thsmith

swap with known good woofer to ensure it is a bad woofer or possible crossover issue. If woofer just replace. Might be time to upgrade/replace caps and resistors.

zruben

Alright, I'll give that a try and report back!
--Zach

zruben

Well, I switched the woofers. Now they are both working. However, after listening closer it seems as though there is almost a distortion coming through one of the individual speakers. It only happens when the music becomes very dissonant and only when it's at a certain frequency. Any ideas would be appreciated!
Thanks

westmassguy

If you moved the troublesome woofer to the other cabinet, and the main complaint went away, it could be loose screws, or some type of cabinet resonance.
I have repaired woofers that were over-stressed by excessive use of the volume control, and exhibited distortion only at certain frequencies. Some develop stress creases where the cone attaches to the spider and voice coil former. This applies to treated, coated, or plain paper cones. You may have poly cones however.
Look for any separation or tear between the cone and the spider, or tears in the spider itself.

thsmith

zruben wrote: »

Well, I switched the woofers. Now they are both working. However, after listening closer it seems as though there is almost a distortion coming through one of the individual speakers. It only happens when the music becomes very dissonant and only when it's at a certain frequency. Any ideas would be appreciated!
Thanks

New problem and different woofer? If so repeat test as above. Your speaker leads may be corroded and when you unplug and plug you are getting a better contact. Try cleaning them all.

zruben

Alright, I'll give that a try. I know that this one was never taken apart yet. And it was actually the same problem, different woofer. =/ sigh

zruben

Well, I figured the problem out!
Turns out that the previous owner had actually taken out one of the woofers and "repaired" it. Turns out when he did this he didn't check and make sure all the connectors to the speakers were good and tight. The sound I was hearing was actually one of the connectors making and breaking connection, thus the weird distortion sound. Went through all the connectors and used a needle nose to bend them so they were all good and tight.
I did notice that some of the surround material around the speaker is loose. Any fix for that?
Thanks for all the helpful responses!

zruben

westmassguy wrote: »

If you moved the troublesome woofer to the other cabinet, and the main complaint went away, it could be loose screws, or some type of cabinet resonance.
I have repaired woofers that were over-stressed by excessive use of the volume control, and exhibited distortion only at certain frequencies. Some develop stress creases where the cone attaches to the spider and voice coil former. This applies to treated, coated, or plain paper cones. You may have poly cones however.
Look for any separation or tear between the cone and the spider, or tears in the spider itself.

This seems to be what the previous owner had already done with one of the speakers.

Polkie2009

Look around for a couple of replacement woofers, new or used still in good shape. Eventually, you'll need them and you'll have them right there. The Polk LS50 speakers use the same woofer.

ken brydson

Polkie2009 wrote: »

Look around for a couple of replacement woofers, new or used still in good shape. Eventually, you'll need them and you'll have them right there. The Polk LS50 speakers use the same woofer.

Last I heard Polk still stocked the replacements. $48 ea IIRC.

zruben

Thanks for the help guys! Any idea how to reattach the butyl surrounds?

westmassguy

There are two type of adhesive for the rubber surrounds. One is a solvent based, available from Simply Speakers, Orange County, or Midwest, that's made specifically for rubber. The newer type I've been using, is a modified, very thick form of Cyanoacrylate (crazy glue). It's the consistency of honey. The solvent type gives you some time to work, the other bonds almost immediately.

zruben

Thanks, I'll have to give that a try!