8" Hall of Fame

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well that killed the dialogue...

I do not know, but adding something to the cone will make it heavier. It may also be that some of the benefits of removing the dust cap is not related to the shape or size of the dust cap, but maybe you are reducing the "air spring" effect of the driver right at the center where most high frequencies originate from, maybe the small chamber inside the voice coil has resonances in high frequencies and simply removing this chamber helps. This is just me thinking though, so don't read it as anything else.

It has been documented a few times the effects of cutting away the dust cap and putting in a phase plug, there are threads containing info about this stuff. But they focus more on the phase plugs, and maybe not the effect of the chamber in the vc and its possible resonances reverberating back through the dustcap.
 
I do not know, but adding something to the cone will make it heavier. It may also be that some of the benefits of removing the dust cap is not related to the shape or size of the dust cap, but maybe you are reducing the "air spring" effect of the driver right at the center where most high frequencies originate from, maybe the small chamber inside the voice coil has resonances in high frequencies and simply removing this chamber helps. This is just me thinking though, so don't read it as anything else.

It has been documented a few times the effects of cutting away the dust cap and putting in a phase plug, there are threads containing info about this stuff. But they focus more on the phase plugs, and maybe not the effect of the chamber in the vc and its possible resonances reverberating back through the dustcap.

a dust cap can be made of paper, felt, aluminum and a mixture. the 12lta is probably made of paper. i wonder if replacing it w/ a felt one might improve the response?
 
frugal-phile™
Joined 2001
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if 2 screws are put in the base of the phase plug & the plug width is as wide as possible, but not touching the coil, then the proper fitment is achieved by trial & error?

We use 3 screws on the FE20x plugs, 4 of the 12LTA plugs.

this sounds kind of hokey to me. it seems that a phase plug might slip off center & scrape the coil.

It does happen, but once set rarely happens in use. If one wants to have them unremovable, you could glue them in with epoxy, but care must be nade to not have any slip out and glue the voice coil down.

what about omitting the plug altogether or use a different more linear dust cap?

Then you have not solved the problem of the oil can resonance you are trying to get rid of.

dave
 
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