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This is one of those places where you get into conflicting demands. Most of the speakers that can handle a lot of power like this are big, and you want a small speaker to couple well with the plate. If the speaker crosses node lines you're pushing down on both ends of the see-saw at the same time.

Since we're mostly dealing with pretty low frequencies, I find that long-throw woofers or mid-range speakers work well, and the smaller ones are often made for automotive use. The RadShack speaker I've been using is a 5" unit, #40-1354A. As I say, they don't make these any more, but if you can find the specs on it, that might help in finding a replacement.

Does this look like a suitable speaker? http://www.maplin.co.uk/Module.aspx?ModuleNo=37984

_________________
Formerly JJH

I learn more from my mistakes than my successes

Chris---I found these specs for the discontinued Radio Shack speaker that Al mentioned he uses. They're on a site some guy put together on the "Voight-Pipe" speaker design, which these speakers apparently are based on. Might be a bit more than you ever thought you'd want to know about this stuff, but if you want to learn more you should be able to find it here: https://mywebspace.wisc.edu/jstalnak/web/VoightPipeSpeakers/

Radio Shack SPECIFICATIONS for 5-1/4" HiFi Auto Speaker Cat. No. 40-1354A
Impedance 8 Ohms
Frequency response 50 - 14,000 Hz
Free air resonance 50 Hz
Efficiency (SPL at 1 Watt, 1 Meter) 90 dB
Nominal power 20 Watt
Maximum power 40 Watt
Magnet weight 10 oz
Speaker weight 30.6 oz
SPECIFICATIONS posted on Bottlehead Forum by Greg on 1.20.2000

Fs = 71.5 Vas = 7.3 liters Qts = .49 Qms = 3.85 and he notes: These should be enough to get you started. They seem to indicate a 14 liter ( .5 cu ft) box tuned to about 58 Hz.

Hope this helps.

John

Well those look close to the specs on my speaker. I mean my speaker works it just heats up!
I'm wondering if it might have something to do with my computer sound card and the tone generator. It just seems odd to me that no one else has this problem. And it has happened with two different speakers. So I kind of think the one thing that isn't the same with others setup is my laptop and the tone generator. If you remember I tried another tone gen. program and it didn't work with my computer so maybe the odd link is my computer. I suppose I cound download the program onto my newer laptop and try it and see if there is a difference. Ye old process of elimination. Maybe next round as I have this one voiced and I need to move ahead.