HELP-woofer moves alot when playing lps

Agree with Stereo5 - the KAB filter is the best thing going to eliminate this issue. I love mine - zip zero nada downside to using it, absolutely no negative sonic impact and 100% solves the problem.

I have mine between my phono stage (PS Audio GCPH) and amp (Cayin A-70T).

We don't know what speakers we're talking about here. Whether or not the woofers could be damaged depends on the size of the woofer, it's excursion capabilities, and the extent of the pumping. MANY woofers will be damaged by repeated linear excursions in excess of their capabilities. If the pumping is severe, it's a recipe for disaster. At the very least, you're getting lots of distortion. If you get/make a more suitable mount for your TT, it will probably sound much better and eliminate the pumping. If the pumping is not severe and bottoming out, you can probably ignore it, and wallow in mediocrity.
Regards,

From a speaker perspective, big movement like that is way wrong. You are seeing a speaker attempt to reproduce a subsonic wave, introduced into the system by the playback system (turntable). Count how many times a second it moves and you have the freq-5Hz-7Hz? Subsonics eat up all your amp power as your amp is attempting to reproduce what you cannot hear and the power curve is highest in the low end. Moving woofers in out to their extremes as pushes the drive unit coils out their gaps (there is a point inside the coil where it is centered n the magnet and outside that, distortion goes straight up). Loud enough, it will damage the woofers as they are not designed for subsonics. Now normal audio is now riding on top of that woofer moving in and out, so its "smearing" everything. A mess for sure. FIx it fast.

Get rid of the subsonic input -a filter is the your best initial choice. Some built in subsonic filters are not so good-they are too high or use to slow a slope-like 40Hz is too high and if its slope is only 6 dB per octave, 20Hz will only be 6dB less than 40. If you still see some woofer movement after your engage your filter, or can hear the filter dramatically change the low end, find a better filter. However, some low end change is better than the tremendous masking artifacts and distortion the subsonics are introducing elsewhere. Subsonic filters at 20Hz are ideal, and a steep rolloff, like 18dB per octave would be best (20Hz 18dB per octave would mean 10Hz is 18 dB down from 20Hz). I defy anyone to hear a 20Hz filter (if you can, turn yourself in to science).

Next, find where the subsonics are coming from: a bump in the turntable /motor/belt? Acoustic feedback (improper mechanical or acoustical turntable isolation from the speaker)? Warped discs? FInd it and fix it. The KAB company makes an argument that rumble can be introduced by the cutting lathe (built in to the master disc) and this is true, but far less common than turntable/disc related problems within a turntable/disc warp/isolation. Most companies tried to catch cutting lathe issues on QC.
Brad

Brad

A search on "woofer pumping" shows 22 threads.

Tbromgard

I recommended spending some time isolating your TT, Gear and speakers better so they are not affected by structure feedback. The speakers can in fact be aimed at your TT - sound pressure (acoustic feedback) itself is not the problem. When the acoustic feedback is absorbed by the rack, shelves, floor and walls around your TT, gear and speakers and changes to structure feedback - this then becomes the problem - if your TT, Speakers, gear are not isolated properly. See also the last 30 or so posts on Copernican.

IMO - Any filter not recommended by the speaker manufacturer themselves should be considered a 2nd option only after isolation attempts fail. Its a band aid, another layer.

Good luck.

Thanks for the responses. I purchased the KAB filter. I dont believe isolation is an issue-the TT is well isolated. Also, the tonearm manufacture believes cart/arm mismatch is not the issue. The arm and cart are both medium mass/compliance and should work fine togther-so I dont think that is an issue either. I really dont want to add another circuit path for the signal to run, but it seems inserting the KAB filter is my best choice. I will report the results once I rec'v the unit. Thanks all.