Saturday, November 23, 2019

Ohoh. Rattle in the 2+2's

In the past few days, I readjusted the bass EQ using my method (sweep with oscillator and adjust parametric EQ functions to fix all the bulges).  Last weekend the right sub wasn't even working (not sure how long) but after fiddling with it (I suspect loose something related to AC power) it started working again and I'm now keeping it in the "ON" rather than "AUTO" mode which might keep it warm enough to keep from dropping out again.  The faulty speaker is near the doorway were it may get more humidity.  Before I replaced the plate amplifier about a year ago, I had always kept this unit turned on.

I did the EQ adjustments (notch filters) basically from scratch, staring with the biggest bulge (either 40Hz or 45Hz depending on side) and working on down.  I can't remember the last time.  Anyway, it worked out fabulously, better than ever before, very flat bass response and no 100 Hz bulge (which has been one of the toughest to deal with).

So, on Friday I was enjoying some of the most transparent sound I've ever heard, if you can call it that playing electronic music from William Orbit and Grouse.  But then, playing Grouse (which itself is full of "deliberate" rattles and distortion) it became clear there is a rattle in one speaker.  I reversed channels and it was still there.  I tried squeezing the speaker (which seemed to help at first), slight shaking, etc., nothing helped.  I turned out lights and did not see any sparks or smell anything.

I isolated a 15 second piece of music which curiously doesn't sound loud but has a very high peak to average ratio and seems to include a bunch of tones which harmonically beat somehow and stimulates the problem consistently.  Playing that over and over, it seems I can sometimes get the rattle to go away, but then it comes back again.  Sometimes playing at the loudest possible level actually suppresses it longer--but then it starts again.

I'm pretty sure it's "mechanical," a broken stator wire support or something like that.  It probably wouldn't be hard to fix, once I get the stock off of the speaker, which I've never done before, mostly fearing the part of putting the sock back on--which is near impossible to do as well as the factory did it (no wrinkles, etc).

I'm not going to bother fixing this until mid January at the earliest.  It's another "opportunity" to do something I've never gotten around to doing before.

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