Sometimes you win, sometimes not so much:

Recent E155-4 acquisition

LF tone from precision sinewave oscillator into D45 amp produces some undesirable noises, even at fairly low excursions.

JBL spec says sweep test is 7v 20Hz-1.2kHz so I mostly kept to that or lower.
Did notice some pretty buzzy distortion right around 100Hz (something loose/resonant)... would have guessed tinsel leads, will have to double-check that.
Higher freqs (albeit lower excursion) sound fine. I could see where someone would briefly test this with music and call it 'good'.
Checked tinsel leads. Did not notice interference or cone slapping (but didn't sweep through 100Hz until later ) .
Checked rear vent filter. OK (probably replaced when reconed... -looks- fairly recent, hard to tell but still quite pliable/not disintegrating) .
Cone is marked MWE155 224 04 (dome glue line looks pretty good).
Tested with rear vent unblocked, holding on-edge (vertical), shooting for free-air environment.
Not noticing any rubs/scraping when carefully moving cone manually (evenly, just outside the periphery of the dome/downward, or from underneath/forward) being careful to not induce any side motion that would tilt the voice coil.
VC resistance appeared normal, and did not jerk around when cone was moved (i.e., steady when not moving... coil vs magnet motion will make the measured value change while moving).
Magnet did not appear shifted. Frame did not look damaged.
Rotating driver to terminals up seemed to change the noise characteristic -slightly-... that was the only clue I could find.

Compared with another E155-4 to make sure test was 'fair'... it was fine with even lower freq and higher excursion levels.
Have not tried it in a box yet. Have not put it on a WT2 woofer tester (I only have their initial low level device). Haven't tried green eggs and ham with a fox yet either... bucket list?

At any rate, I don't think I'm just being picky. LF drivers in free-air do tend to make some unexpected noises.
I'll keep poking at it, but I'm quickly running out of ideas.
Funny that I found one mounting screw had been left in and was held captive by the front-side gasket (alas, it was not the culprit).

Suggestions, re anything I forgot before attempting a return?
I'd prefer to have a working unit, but if truly faulty and not reasonably repairable it would be an expensive core to start over with.



Maybe someone else can use this as a check list, if nothing else. Thanks for listening.