HELP-woofer moves alot when playing lps

Just got a KAB filter and installed it. Much better!!!

One thing that is for certein is that many records are often not flat, but have minor warps that cause this great displacement of the woofers due to the low frequency. It's not the problem of the table, the cart, ot the isoltaion. It IS the record and the ONLY way to solve this is to use a low pass filter. It is down 3 dB at 18 Hz and continues down at a steep 18 dB per octave from there. This is not going to cause any negative effects. And bass is in mono anyway from 140 Hz on down and the filter also removes any vertical rumble in this region.

The KAB has in fact has tightened up the bass in my system. Highly recommended!

A rolloff point at 18Hz will cause phase shift up to 180Hz- IOW, 10X the cutoff frequency. The phase shift will manifest as a loss of impact, increasing as frequency is decreased.

This might not be all that noticeable if the speaker has an LF cutoff that is significantly higher than that of the filter! Smaller speakers, where the LF noise is outside the passband of the speaker, may well be particularly susceptible to woofer motion. We run some smaller monitors here that cut off at 40Hz and have not had any troubles with them at all, FWIW

We set our preamps up with about 2Hz rolloff, even in the phono, to avoid phase shift. We avoid woofer pumping by the proper combination of cartridge compliance and effective mass in the arm.

Not uncommon for warps or other imperfections in record geometry to produce subsonic rumble To some extent. Goes with the turf with hi fi phonos. resonance frequency of cart/tonearm can exacerbate the problem with certain combos more than others.

The biggest danger of this is that subsonic rumble uses power that is no longer available for music and clipping can occur sooner, impacting sound quality and putting drivers at risk, so be careful.

BEst solution is avoid records that have this problem too much as much as possible. Get a better quality copy. High pass filters are the common solution, but that is a band aid and effects on sound are usually noticeable.

Better yet, go digital. No subsonic rumble and other vinyl snafus there! :^). Digital can be very good for not much cost these days, much more so than in the past.

My Pro-ject Xpression III did this same woofer pumping issue. It was very noticeable as soon as the stylus hit the record before the music started. Same system, same table location, same cartridge, same phono pre, same high efficiency speakers (92dB Tekton 6.5t) and now totally gone now with a new RP6 (both tables were setup professionally by same shop). Was the motor vibration in the Pro-ject coming through the subplatter and platter.

I have the same issue.  Here are the things I've tried to solve the issue. Switched turtables: had a newer bottom line audio technica,  figured it just couldn't handle being amplified a lot (just bought classic cerwin vegas, wanted to really crank them up with some Rush vinyl).  So I tried my old Dual 505.2 with the same issue. Okay, swapped my yamaha receiver out with my wifes old Kenwood.   Same problem still.  Last attempt was purchasing a DJ-PRE2 preamp...  still did it! BUT it has a low filter... well I'll try that! Works great, and the sound quality is not better or worse, well better in  sense my speakers can concentrate on producing low end signals without the woofers going nuts!  Played some albums with some nice low bass, and it all sounds good.

What I've come.to believe is what someone said in the thread.  The stylus is picking up vibration from the speakers, so in a sense is creating a kind of feedback in the low frequencies. 

I recommend that DJ-PRE2 preamp, super mixer unit,  and it also has a gain for fine tuning! 40bux in Canada