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Raspy buzz on certain low frequencies

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Posted on May 9, 2021 at 16:28:49
Dr. Fuse
Audiophile

Posts: 48
Location: BC
Joined: May 12, 2020

I've got a custom pair of planar speakers, made from the old Alternate Audio kit. 4' Mylar diaphragm, copper wire, very strong magnets.

One of the speakers has problems with certain low frequencies - most notably timpani in the area of about the octave below middle C.

I would like to try and repair this, but it is a gargantuan task to take the magnets apart, which hold the Mylar in place - a job I don't feel capable of handling.

The repair DIY guide in the link seems like a doable job. But I am a bit reticent to do it, in fear of further damaging these overall lovely (and irreplaceable) speakers.

Has anyone tried a repair like this? Advice and warnings sought!

http://integracoustics.com/MUG/MUG/tweaks/DavePride/

 

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RE: Raspy buzz on certain low frequencies, posted on May 11, 2021 at 18:38:11
Green Lantern
Audiophile

Posts: 16952
Location: San Diego, Ca
Joined: November 12, 2002
Contributor
  Since: June 17, 2003
 At the very minimum you'll want to remove the cloth covering the panels which may include the connecting plates. From there take pics from top to bottom front and back INCLUDING the connection plate and the wires which connect to the speaker/crossovers; THIS IS IMPORTANT, reason being once you're done with the panel and you start reverse putting them back together you may notice a loose wire or three (never fails) and without the pic it'll be hard guessing where they connect to. And also we'll know what we're dealing with. Sounds like a Magnepan clone(?).

Next post a few pics here so we can get a better handle on them.

Do a visual, look for obvious loose copper wiring on the mylar.

Next fire them up so you can get an idea exactly where the buzz is originating from.

If it's a simple case of an unglued wire(s) you're in luck, all you'd have to do is remove the old glue from the wire and the small area on the mylar where it'll rest (small amounts of acetone works the best) and reglue them back down. Once you're at that point then we can help in more detail.











 

I would add, posted on May 11, 2021 at 18:58:26
Green Lantern
Audiophile

Posts: 16952
Location: San Diego, Ca
Joined: November 12, 2002
Contributor
  Since: June 17, 2003
 I re-read your post, are you indicating the mylar is 'sandwiched' between magnets?

If that's the case ignore the above and determine 'how' the magnets are attached, if they're riveted (a'la MG20s) you're at a disadvantage since you'd have to drill out the rivets and undo the 'sandwich'; which could be a two person job depending on the weight.

But once again, a picture speaks a thousand words, you could just take a pic of the plates first and post them here, perhaps someone is familiar with that brand.











 

RE: Raspy buzz on certain low frequencies, posted on May 14, 2021 at 18:33:15
George S. Roland
Audiophile

Posts: 1470
Location: N W Pennsylvania
Joined: March 20, 2004
 Dear Sir,

Sorry for your troubles, and I apologize if you have already done these things, but are you absolutely certain the problem is with the speaker? Did you swap speaker leads to see if the problem swapped as well? Did you try other speakers?

I had a guest play a CD he'd made with some extraordinarily low bass on my Quads and there came a raspy sound. I was completely convinced this had caused damage to my speakers. After some experimentation, it became evident the damage had occurred in my preamplifier. The speakers were just fine.

Just a thought.

 

RE: Raspy buzz on certain low frequencies, posted on May 14, 2021 at 18:47:28
Dr. Fuse
Audiophile

Posts: 48
Location: BC
Joined: May 12, 2020
 Thanks for the suggestions, George.

I am sure it is the speaker. I have swapped speakers (L,R), cables, amps, source material. Always the same bass area, with certain difficult sounds (timpani, low horn/trombone cluster chords).

I can see what looks like a Mylar patch in the area I think the buzz distortion is coming from. And it looks a bit loose, for an inch or two, not tight like the rest of the speaker and the other speaker.

I tried bracing this area with Saran wrap and foam, but this didn not really do anything. I want to find some of that sticky-but-removeable plastic, like the screen protectors for our phones. Don't seem to have any on hand right now.

I also thought about using a hair dryer to "shrink" the loose Mylar, but this seems dangerous.

As I said, this only occurs at VERY loud volume levels, and only on a couple of passages on certain recordings. So not really a problem, except my OCD personality knows it is there!

Tanks again for your time

 

RE: Raspy buzz on certain low frequencies, posted on May 14, 2021 at 18:48:31
Dr. Fuse
Audiophile

Posts: 48
Location: BC
Joined: May 12, 2020
 Hey, GL, thanks for the suggestions. Will post photos soon!

 

RE: I would add, posted on May 14, 2021 at 18:49:15
Dr. Fuse
Audiophile

Posts: 48
Location: BC
Joined: May 12, 2020
 Will post photos soon! Cheers

 

RE: Raspy buzz on certain low frequencies, posted on May 21, 2021 at 14:26:31
Dr. Fuse
Audiophile

Posts: 48
Location: BC
Joined: May 12, 2020




Here are a few [crappy] photos. One of the close ups, the unevenness of the mylar and copper wire is almost visible. This seems to be the trouble spot (just a guess).







 

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