Serious audio question

I suggest asking on rec.audio.tech.

Check out

They have speaker repair kits. They replace the foam surrounds, a common problem with aging speakers. I have used this product before, and it does work. You did not mention the speaker size! The kits are around $20 depending on size. Good luck.

Or Google for "replacement foam surround". As scada suggests, it is a common problem with a common solution, available from numerous vendors.

60A, eh? It takes 480V to push 60A into an 8 ohm speaker, so those must be some pretty impressive supply rails that it has.

Audio systems often have two or more speakers in parallel, and the actual impedance at low frequencies approaches the DC resistance, which is closer to 6 ohms. So, 60 amps into four speakers in parallel would require about

90 volts peak. At this level you will be pumping out about 3000 watts RMS. That's just a bit much, unless you are doing the sound for a Rolling Stones or ZZ Top concert. I think they are the world's loudest? Eh? Say again?

Paul

It's not that simple.

8ohms is impedance, not resistance. The speaker is a linear motor, and at any particular instant depending on which way the signal changes might develop a back emf which adds to the amplifier's voltage across the DC resistance of the motor coil, which is much lower than 8ohms.

Imagine spinning up an unloaded DC motor to full speed (at which point its back emf would about equal the power supply voltage), then suddenly reversing the power supply. You could now develop a peak current equal to twice the power supply voltage divided by the DC resistance of the motor.

So 60A is not out of the question even if the amp has typical power supply voltages for a 100W amp.

It might be unlikely to ever deliver that current except perhaps with paralleled speakers, or whatever.

It is simply specified as being capable of delivering 60A peak.

Good day!

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_____________________
Christopher R. Carlen
crobc@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5

An excellent idea. Except perhaps if I was looking for the unique perspective of electrical engineers, much like I might ask about preferred toilet plunger brands on rec.food.cooking.

:->

There's also sometimes the motive of just wanting to hear the responses of ones peers, having participated in a group for a long time. Hence the cooking and BBQ grill questions, etc.

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_____________________
Christopher R. Carlen
crobc@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5

On a unit I aquired, I replaced the foam with rubber surround. It did not fit exactly, at least in the usual sense. The rubber lip was a bit small, but I managed. I probably bought the kit from Parts Express. All woofers are not exactly the same sizes. The rubber will last much longer.

That speaker I also treated the midrange with some Airflex 400, and tightened up the connections and screws. I always solder the crimps. I redid the wood and cleaned the front grill.

I sold the speaker back to the orginal seller.

greg

I haven't read all of the posts, just the topic, and yes you can buy kits to replace that foam stuff, but I once had a really nice pair of Infinity speakers a while back, lost them in a divorce, but anyway, the foamy stuff rotted out, so I took them to a place that "repaired speakers," in fact it was somewhere like Westminster, or Huntington Beach, California/Orange County/USA. And that place fixed those speakers like absolutely good as new. And the price probably, roughly [1-arm + 1-leg]/4. Not trying to be funny, all I remember is that the price was "reasonable." Although, I think I'll write down that equation, because now that I see it, I think it's funny. In fact, I'm just going to go file>print... right now, so I have it.

Maybe that's of some help.

GregS wrote:

fit exactly, at least

Stones

Excessive assumptions that the 60 A rating is for anything other than a short term (