Speaker repair (not photography related)

Olympus OM-D E-M5 Mark III

05/21/2010 10:40:58 PM · #1

Ahoy ye DPC mateys. I'm hoping there's someone out there who knows a thing or two about speakers.

I just picked up a pair used of floor-standing speakers that seemed fine when I picked them up, but when I got them home, one of the subs sounded like it was blown. Physically, there doesn't look to be anything wrong, and the wiring seems fine.

Oddly, I found that when I applied light pressure to a certain spot on the outside edge of the foam that makes up the cone, the sound suddenly became just fine. But without doing that, it's all buzz and no bass.

Any idea why this would be, or what a good fix is? I rigged up something with scotch tape and kleenex, and it sounds fine at the moment, but I hardly expect this jury-rigged business to last long.

Thanks all!

Yo_Spiff

Olympus 12-100mm f/4.0 M.Zuiko ED IS PRO

05/21/2010 10:47:08 PM · #2

Sounds like the foam or some other part of it is worn and the speaker cone is vibrating in ways it should not. I've had similar with my car speakers, though when I took them apart, I found the foam ring was completely deteriorated. I think you will probably have to replace the speaker cones for a permanent fix. If you can find suitable replacements, it ought to be a fairly easy job with some light soldering involved.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

05/21/2010 10:50:01 PM · #3

The suspension, which is the foam or rubber surrounding the cone that allows the cone to move while maintaining centering of the cone, is shot. You should be able to find someone who can repair the suspension. Meantime, keep in mind that operating the speaker with the damaged suspension may cause damage to the voice coil.

Canon RF 24-70mm f/2.8 L IS

05/21/2010 10:57:06 PM · #4

Fritz, Steve, thank you both.

Fritz, I appreciate your warning. Do you know whether it would be safe to assume that if the sound is all right, there's no risk of damage? My kleenex/tape job seems to eliminate the distortion.

And is the suspension the sort of thing that could be damaged in transport? I swear they were in good shape during the sound test at the prior owner's house, but the problem was obvious upon setting them up at home.

kirbic

Canon EOS R5

05/21/2010 11:03:24 PM · #5

If you don't hear buzzing or distortion, it's a good bet that things are moving freely. And yes, it's possible for something to happen during transportation, but I'd bet that the problem was imminent prior to transporting them. Transportation shouldn't damage suspensions that are in good shape, but might push weak ones over the edge.

Sigma 10-20mm f/4-5.6 EX DC HSM for Canon

05/21/2010 11:07:08 PM · #6

Originally posted by kirbic:

All right, thanks again.

Glad to know that if it sounds okay, it probably is okay--that means I can actually use these things. (Never had floor speakers that went down to 32hz before! It sounds fabulous.)

And I'm actually glad to know that transportation could have caused the problem--I prefer that explanation of the problem to being forced to conclude that the people I bought from were shady. They certainly seemed decent enough, and everything else works just fine.

glockguy

Canon EOS-7D

05/22/2010 12:04:42 AM · #7

I hate to be the bearer of potentially bad news....

Typically if you can physically manipulate the speaker to eliminate buzzing, it indicates a dead spot on the voice coil. While it is completely possible that it is just the suspension or spider which is the issue, it is much more likely to assume that the VC has uneven wear on it.

Just an opinion, I could be way off base without actually listening myself.... Usually, you can see a deformity in the spider which would cause this.

This sounds very odd, but get right up in your speaker's biznass and smell it. Does it smell burnt? If the answer is yes, it is a strong possibility that the VC is starting to wear. While it is totally normal for a little bit of burnt smell during the normal course of the speaker's life, if the smell is quite strong, that is unusual.

Another trick that works quite well, if you determine that it is the surround (the foam part around the edge) of the speaker that has a small defect like a rip or tear in it; is to use clear nail polish and lightly use it like a super glue to fix the defect. Use it sparingly though.....

A VC can be repaired, but it is typically more expensive a repair than the value of the speaker. This is because the cost of the VC is usually related to the quality of the speaker.

Hope this provides some insight....

ETA:

The VC problem is quite common in floor standing speakers that play down to low frequencies. The reason for this is that people enjoy the lows, but typically don't have the power to adequately play the speakers without clipping the signal. Clipping heats the VC and will cause wear and dead spots.... This will quite often produce the same symptoms you are experiencing. Remember you will never blow a speaker with too much power, only not enough. It seems counter-intuitive, but it's the honest truth......

Message edited by author 2010-05-22 00:10:04.

Sigma 10-20mm f/4-5.6 EX DC HSM for Canon

05/22/2010 12:55:19 AM · #8

Originally posted by glockguy:

Hmm. If it's accurate bad news, I'd rather have that than inaccurate good news.

I didn't inspect the spider with extreme care--only what my eyes and a lamp could tell me--but I looked moderately thoroughly for deformities and didn't spot anything.

Originally posted by glockguy:

This sounds very odd, but get right up in your speaker's biznass and smell it. Does it smell burnt? If the answer is yes, it is a strong possibility that the VC is starting to wear. While it is totally normal for a little bit of burnt smell during the normal course of the speaker's life, if the smell is quite strong, that is unusual.

Sounds like an easy test to run--I'll have to do that tomorrow when it's not too late for bass thumps.

Originally posted by glockguy:

Remember you will never blow a speaker with too much power, only not enough. It seems counter-intuitive, but it's the honest truth......

Boy, that sure is counter-intuitive. These speakers are 150 watts, and the amp is 100 watts per channel. I believe that this pairing has been in use for the life of the speakers. Is it the case, then, that the relatively underpowered amp is cooking the speakers?

Originally posted by glockguy:

Hope this provides some insight....

It does! Thank you. I'm hopeful that I'll be able to resolve this issue without extreme added cost. I got a great deal for a working system, but something less than that if repairs wind up being expensive.

glockguy

Canon EOS-7D

05/22/2010 01:11:32 AM · #9

Originally posted by mycelium:

[quote=glockguy] I hate to be the bearer of potentially bad news....

Typically if you can physically manipulate the speaker to eliminate buzzing, it indicates a dead spot on the voice coil. While it is completely possible that it is just the suspension or spider which is the issue, it is much more likely to assume that the VC has uneven wear on it.

Just an opinion, I could be way off base without actually listening myself.... Usually, you can see a deformity in the spider which would cause this.

Originally posted by glockguy:

Unfortunately, speaker manufacturer's tend to rate the speakers based on what will sell them rather than on anything quantitative, same goes for amp manufacturers. You could take 2 amplifiers, one inexpensive and on more expensive, and on a scope, even if they have the same rating, will perform differently.

Usually, we recommend that people buy 2 times as much power as a speaker is rated for. This ensures that the speaker will have ample power, and that the amp will not ever perform at it's maximum.....

Here's a graph that might explain better what I mean.

The square parts are an amplifier delivering past it's optimal range. So, you can see, both amps can deliver the same power, but one does it without clipping, while another produces a square wave. It's the square wave that cooks the VC........

This graph isn't specifically derived from an amplifier, but it it's the same concept. Disregard the text......

Anyways, I hope it's a simple fix for you.....

Message edited by author 2010-05-22 01:12:04.