Vintage speakers problems?

Marshal

i have a set of kenwood speakers that are at least 25 years old. they have always put out wonderful sound. recently tho, since i connected them to a new receiver/amplifier and new tv, they have been crackling and it's getting worse. i've even recut the speaker wire to expose fresh wire for the connections to the back of the speakers and the new receiver.

any idea what's going on and what i should do?

boston1450

Is both speakers doing this ? Is the receiver compatible with the speakers ? Could be a bunch of different things

boston1450

What are the speakers MODEL ? What is the receiver Make/Model ? that may help

Schurkey

Is there anything left of the driver surrounds?

boston1450

^^^^ + 1 --- 25 year old speakers tend to get bridle

mhardy6647

Many loudspeakers since the early 1970s used light, pliable foam (typically polyurethane) surrounds on cone drivers - predominantly woofers - to enable the use of "acoustic suspension" box alignments to get extended, well-damped bass from small speaker enclosures (albeit with rather poor sensitivity... but amplifier power was becoming cheap). These "foam surrounds" tend to degrade over time; after 10 - 15 years, they've usually disintegrated. The good news (despite the fact that many, many otherwise perfectly good loudspeakers were thrown away needlessly!) is that this is easily and inexpensively repaired.

Chances are - frankly - your Kenwoods really aren't worth the effort... BUT who am I to judge? If you like them and would like to rescue them -- pop off the grilles and look at the woofers. If the foam surrounds are dried out/brittle looking or feeling (and/or if chunks of 'em are missing), it's time to "refoam".

There are plenty of professionals who will refoam woofers for (typically) a reasonable price -- chances are you could find one locally. It's also straightforward to DIY. Parts Express sells complete kits -- a little expensive but as an "all in one" solution they're great for neophytes.
http://www.parts-express.com/cat/speaker-surround-refoam-kits/328
Good, inexpensive, generic surrounds are available inexpensively from MAT Electronics. www.matelectronics.com (although they have a minimum order). Some woofers require very specific surrounds; these are typically available on-line (e.g., check eBAY).

There are also primers on line illustrating how to - and how NOT to - refoam a driver successfully.

Two other thoughts: 1) it's possible that more than one of your drivers in each speaker have foam surrounds -- if so, they probably ALL need to be replaced. 2) Some of the sonic problems might also arise from the 25-year old passive components in the speaker crossovers (particularly capacitors). NOW is a great time to replace/refresh crossover components while you're under the hood! ;-)

mhardy6647

Here's a pretty typical instance of "foam rot" on a woofer. I always like to perform a CAT scan on drivers before repairing them :-)

DSCN6215 by mhardy6647, on Flickr

This particular driver, in a Pioneer HPM-1100 speaker, is somewhat specialized in terms of its surround. The driver is, more or less, a copy of a classic JBL woofer. In this particular case, the surround mounts to the back side of the cone (most mount to the front). These surrounds are readily available, but - in this particular case - a generic "15 inch" surround isn't appropriate.

pioneerwooferdimensions012709 by mhardy6647, on Flickr

... and here's the finished result:

HPM1100 woofer front by mhardy6647, on Flickr

HPM1100 by mhardy6647, on Flickr

Here are some extremely comprehensive :-) on-line instructions on refoaming from Steve Deckert (Decware).
I'll offer the opinion that not all woofers require quite as much effort -- but I'll leave it at that ;-)

http://www.decware.com/newsite/refoam.htm

Schurkey

mhardy6647 wrote: »

Here's a pretty typical instance of "foam rot" on a woofer. I always like to perform a CAT scan on drivers before repairing them :-)

Precious.

mhardy6647 wrote: »

Here are some extremely comprehensive :-) on-line instructions on refoaming from Steve Deckert (Decware).
I'll offer the opinion that not all woofers require quite as much effort -- but I'll leave it at that ;-)

http://www.decware.com/newsite/refoam.htm

Well, sure, I'll be blunt. I found no reason whatsoever to cut the dust-caps of my AR bass and midrange drivers in order to pack the voice-coil gap with "shims". I removed the old rotted-foam surrounds, cleaned-up the foam and old glue residue from the cones and metal baskets, and installed the new surrounds all while leaving the dust-cap in place.

It may be that my AR drivers are more forgiving in this regard...or it may be that shimming the voice-coil is a very "optional" procedure.

My first-ever surround replacement project was a marvelous success. Four woofers, two midrange drivers on that pair of speakers.

mhardy6647

Schurkey wrote: »

Well, sure, I'll be blunt. I found no reason whatsoever to cut the dust-caps of my AR bass and midrange drivers in order to pack the voice-coil gap with "shims". I removed the old rotted-foam surrounds, cleaned-up the foam and old glue residue from the cones and metal baskets, and installed the new surrounds all while leaving the dust-cap in place.

It may be that my AR drivers are more forgiving in this regard...or it may be that shimming the voice-coil is a very "optional" procedure.

My first-ever surround replacement project was a marvelous success. Four woofers, two midrange drivers on that pair of speakers.

Thanks ;-) Some woofers are indeed more forgiving than others -- fortunately for the thumb-fingered like me.

westmassguy

Nice job. The graphite woofers are extremely fragile.

mhardy6647

Thanks. I was very pleased with the way they turned out -- fortunately the HPM-1100s were given to me by an audioasylum "inmate", so I had little to lose (although I would have been wicked POd at myself if I'd bjorked either driver!).

My sense was that these cones are considerably more robust than the earlier graphite-impregnated cones used, e.g., in the HPM-100 woofer. I could be wrong about that, though.

westmassguy

I've done many, and it's always been a "white knuckle" re-edge. The owner of the shop I get my supplies from told me he broke every one he ever tried re-edging.

mhardy6647

westmassguy wrote: »

I've done many, and it's always been a "white knuckle" re-edge. The owner of the shop I get my supplies from told me he broke every one he ever tried re-edging.

So -- in my case, I guess, ignorance may have been bliss. I knew that the earlier cones were really touchy, but the HPM-1100's woofer seemed much more stout (so I was comparatively - if foolishly - fearless!).

Fearlessly the idiot faced the crowd...

boston1450

What happened to Marshal ?

mhardy6647

We (I) probably spooked him :-(

D'oh!

"1450", I need to send you a PM on behalf of an AK colleague; check your inbox (tomorrow) -- I'm too shagged out (as they used to say) to compose a note tonight...

boston1450

Yes sir