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Midrange rear chamber damping

invalidbuffa

invalidbuffa

Super Member
I'm thinking about installing the Ti mids and filter modification in my Forte II's (already updated with Bob Crites' Ti tweeters and networks) and thought it might be a good opportunity to experiment with damping the rear chamber of the squawker. A while ago I tried the tweeters with and without the stock fiberglass disc and found I prefer the speakers with them installed. I'm sure there's a reason PWK didn't include them in the mid drivers (maybe cost, or it makes no difference) but I like to try things out for myself.

I'm not sure exactly what materials I should use but I've heard manufacturers like Altec and JBL sometimes used felt. Would this stuff be suitable? http://www.mcmaster.com/#87415k53/=49agru
 
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I damp the pole piece directly under the diaphragm with dynamat and use a dome made up with F-11 Acoustical Felt, I like to use 1/8" felt layers with the absolute minimal amount of adhesive to build the dome, as this will reduce reflections. makes for a dramatic difference.

PS: I do exactly the same thing with the K79 tweeters. I also damp both sides of the terminal tab on the tweeter butterfly as they ring like bells. I do other mods but you need to explore options for yourself and see what you like.
 
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Moray, I was hoping you'd chime in. I think I'll try that. What adhesive do you recommend for the job?

Also, would there be any sonic benefit to using an air-core 4mH coil in the bandpass circuit (parallel) instead of an iron-core? I'm inclined to think hysteresis distortion is of little concern at its position

post-58785-0-77740000-1408149643.jpg
 
invalidbuffa said:
Moray, I was hoping you'd chime in. I think I'll try that. What adhesive do you recommend for the job?

Also, would there be any sonic benefit to using an air-core 4mH coil in the bandpass circuit (parallel) instead of an iron-core? I'm inclined to think hysteresis distortion is of little concern at its position

post-58785-0-77740000-1408149643.jpg
Click to expand...
I use five very small wet dots of PVA adhesive per layer (tacky craft adhesive is good)
regarding inductors read the Forte thread by Set12 everything you need to know is in there.
 
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