High Efficiency Speaker Asylum: RE: JBL E145 vs K145 voice coil heights by Tom Dawson

Hi, Robert -

This is where the difference might be. Even if you call it 7/16", that's a 1/8" difference which could significantly compromise linear Xmax in the outgoing direction if the E145 recone has a voice coil centered that much closer to the spider than the center of the K145 VC gap.

Last night, I took a driver that I have with an E145-16 recone in a K145 frame and pushed about +/-10Vdc into it to get an idea of whether I could detect any visible nonlinearity with such a crude test. Excursion in both directions appeared to be pretty equal and somewhat over 1/8", but I'll try to do the test with more finess and with higher voltages to see whether actual linearity issues are significant with up to 1/4" Xmax in either direction. It'd be nice to have a full audio distortion test setup & microphone right now.

I wonder how practical it would be to remove the recone without damaging it. Anybody know what would be a really good glue solvent for this? Then I could mill down the spider mount by ~1/8" to resolve such a linearity issue. Presumably this is what JBL has done, in effect, if there is such a VC height difference, so the loss in basket material shouldn't have a significant structural effect if done carefully. Apparently, JBL no longer sells E series recone kits, so the ones I already have would have to be reused if this is done.