Audax HM100X4 - warped cones? - diyAudio
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Old 25th April 2013, 09:42 AM   #1
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Default Audax HM100X4 - warped cones?

I just bought four of these drives on ebay. What is TPX? Looks like black polycarbonate to me - thought it was some high end aerogel stuff originally.

Anyway, three of the drivers have one or two areas maybe 1 cm wide that are displaced to the rear by about 1 mm and extend radially. One has about four of these, but they are much stronger, and there is nothing regular about them. The inner edge of the surround has maybe 3 mm pp warping. The whole cone looks like it was blow dried too hot.

Is this normal for these drivers?
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Old 25th April 2013, 10:28 AM   #2
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I have heard of TPX cracking after a while, but not this, however if you look here you can tell from the lighting that the cone shape could perhaps be deviating from what you would expect, in a few places, near the surround.

I think if they measure and sound okay, then you're good to go. Perhaps you could post some pictures so we can see how 'bad' things actually are.

Here things look perfectly smooth though.
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Last edited by 5th element; 25th April 2013 at 10:31 AM.
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Old 25th April 2013, 11:31 AM   #3
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Audax aerogels were coded Z instead of X. TPX is polymethylpentene, a form of rigid polyolefin (a cousin of polypropylene). Audax's venture into using it as a cone material was, IMO, disastrous. They just didn't know how to form it and anneal it correctly, so warping and cracking was the rule, not the exception. I have four of the 100mm TPX drivers, three of them cracked before they were ever used.

It's a material that in theory could be a good component for cones, but the molder needs to know what he's doing.
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Old 25th April 2013, 05:25 PM   #4
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+1. HDA is paper-like and tears much the same. I once put my foot thru an 8 inch HDA much to my dismay.
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