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
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