Speaker Repair

Foam -- such as the foam in carrying cases -- softens and falls apart even when not exposed to environmental contaminants. It just isn't stable.

over

I kept all my college texts. I even occasionally lend them out. I keep much of my pleasure reading as well.

pine

blow

night

speakers?

If you can get or make parts.

an

multimeter?

Yes but it is rare. Yes, they can. They are just capacitors and inductors, separate them and test the components themselves, capacitors dying is by far the most frequent failure mode. Replacement parts may be hard to get.

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searching

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The surround is supposed to keep the cone (and voice coil) centered. I think scratching was how I realized something was wrong with my surrounds. When I glued in a new surround, I'd let the glue set, then move the cone to be sure it didn't scratch. Of ten speakers, I think I had to reset one surround. I'm glad I caught it while the glue was soft.

If the "spider" is good, the surround doesn't do any locating. I rebuilt 8, 4 of them 12 inchers, With the surrounds totally removed there was no scratching I didn't need to shim the voice coil, and the surrounds went on quickly and easily, and the speakers sound EXCELLENT.They were pretty high end speakers - can't remember the brand and they are up in the mezzanine so I can't check.

The surround is for acoustic loading. The spider keeps the motor aligned.

adding

VC

paper/plastic

soft.

aligned.

Not quite the case. The surround seals the airflow between the cone and the spider. It also provides axial tilt support for the voice coil. Both properties are important to overall function.

?-)

Speakers work without surrounds; "seals the airflow" is another way to say "acoustic loading", ain't it? I use shims so the surround is glued when the piston is at rest, thus favoring neither compression nor rarefaction.

Try torquing a spider supported voice coil with a piece of soft cardboard, not gonna happen.

Hmmm, Not only high power blows speakers. El Cheapo amps can blow speakers much easier than good amps. Why? Cheap amps have too much garbage in the output signal. My kids are in music since toddlers. Piano, sax, flute, drum, guitars. I don't have to tell, they wear ear plugs when they jam. Me? I am lower brass lifer since high school days. Still active with local concert band.

It's the clipping in the Power Amp that puts DC pulses of opposite polarity into the voice coil. Pulses always destroy better than steady current.

RMS = Peak (in a square wave situation afaik)

aligned.

and

Both

Your view of acoustic loading seem rather different from mine. Segregating the forward and rearward acoustic domains is a prerequisite for acoustic loading to occur. Acoustic loading is mainly determined by the physics of the speaker enclosure, be it stuffed with absorptive batting, folded horn, bass reflex, or some other design.

?-)

The surround separates the air behind the speaker from the air in the room, don't it? A sure sign your surrounds are gone is the bass falls off. If you have subwoofers you can go a long time before you even notice your mains have bad surrounds. I have some AR4x that appear to have the original surrounds from ca 1968. All foam not created equal. Refoaming is not difficult. You can do a a couple speakers in an hour, once they have been removed from the cabinets. Be "clean room" as possible when the dust caps are off. Get old glue off the frames before removing dust caps and shimming. I use little shims made from theatrical lighting gels, that's about the right thickness for 10" Advent/AR style low compliance woofers. The choices for replacement foam rings are size and the angle of the interface with the cone. Actually whether there is an angle. Either angled or not. That's it. YouTube has a million proud tutorials I'm sure.

Are yours really foam? I have some AR-2ax's from the early 1907s, and the surrounds appear to be rubberized cloth (which should make a better seal th an foam). They have survived over 30 years of California smog with no obvi ous degradation. I do not remember seeing foam on any of the old AR speake rs (AR 1-4) I have seen at the swap meets.

Its not foam or rubber. It's treated cloth. Some kind of substance. I've seen the treatment seep down, but the stuff might be different on different drivers.

Greg

I've had a bunch with cloth surrounds too. I have a pair of AR2 in the middle of a refinishing project. These are AR4x which were "mass produced" by Cambridge standards. They have been on a shelf on my patio for at least 10 years as the tweets (HF drivers) are smoked; the rubber surrounds are still alive and well. I am 30 miles North of UCLA. The air here is not the cleanest. Houston (Petro Metro) will eat your surrounds faster than anywhere.

On reflection, I would guess that the cloth is impregnated with silicone rubber. I do not remember any of it oozing down; however, my sample size is small. Still, foam does not make sense for acoustic suspension woofers.

If it were porous, it wouldn't make sense for any woofer. But it isn't particularly porous.

Two major divisions in foam, closed cell, open cell. Open cell is what we use for microphones pop filters, closed cell for gasketing, etc.

Thanks for the clarification.