rumble issues - see old thread update

Hi Tom,

this is not unusual at all with ported speakers. I used to deal with this back when I had Aerial 10t's. I'm pretty sure we can rule out the Galibier bearing and table setup. :-)
That leaves the warps and off center pressings, which is something we vinyl junkies have to contend with.

I don't believe Nick uses sub-sonic filters (a very good thing, IMHO), but you are correct that this woofer dance is likely adding distortion. KAB sells a sub-sonic filter and adding that may be the lesser of two evils. It would be something to try.

I agree that you should be concerned about possible clipping, so be sure to keep the volume to reasonable levels if your amps are not up to delivering lots of current.

HI Dan

Richard Gray - my local tech and designer thought it probably is tone arm compliance - needing a little more weight

we will see where it goes from there

thanks

Hi Tom,

As you know we use the same arm, cartridge and preamp. With 8-10 different UNIverses on our arm we've never had such issues with any music, at any volume up to window shattering.

Based on that experience I question the tonearm/compliance theory (assuming your cartridge has the SB option). You can test by trying a different counterweight, positioned to give you the same VTF. That will change the eff. mass slightly, which would alter the behavior if eff. mass were the culprit. Seems doubtful to me, as I said, but it can't hurt to try.

We get only minor woofer pumping on obviously warped discs, as we should. Basically it's just the cartridge, arm, preamp and and amp reproducing the warp frequency and pushing it through to the speakers, as they should. But in our setup this never results in sonic breakup or "clipping" unless a warp's so bad the cartridge mistracks. We have exactly one LP that can cause that, a nasty pinch warp. It's our torture test for vertical tracking ability. ;-)

I suspect you have some combination of room interactions reinforcing a low frequency and/or amplifier headroom issues. Both would be volume sensitive and could lead to breakup at higher SPLs.

Just for fun, try blocking the ports on your speakers and see what that does. Try borrowing a different amp too, if you can.