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In all these years of listening to LP's, I never noticed this until
recently. This happens especially on higher volume: In the lead-in groove, or between tracks on LP's, with the grill covers off, I notice the two 8" drivers of my Gale 401 speakers have a LOT of rapid movement................is this normal with records? (it doesn't do it with CDs) If it's not normal, I was wondering if it may be a turntable/arm/cartridge compliance problem. The music sounds fine. Any ideas?
Rumble in the Bronx. Or rather rumble. It's the nature of the beast, I'm afraid. Try the other posts' remedies to remove any external sources of added rumble. But you might be left with the natural record rumble. I've seen this before with my turntable as well. The funny thing is this rumble get blended in with the music when the song is playing so it is masked. But this rumble is what gives vinyl that "warmer" sound.
I notice the woofer movement on some records and not at all on others. The biggest violator that I have noticed so far is Pink Floyd's The Wall (which is on super thin vinyl, and which I have owned since 1978 or 1979), though it still sounds great. I have yet to notice it at all on any 180g LPs. I notice it most, however, when I lower the dust cover as the LP starts to play, and lift the dust cover after the LP. Yikes -- the woofers look like they want to pop out and fly accross the room.
I doubt you have a bearing problem, since it is only noticeable in the middly of the LP. If it happens on ALL LPs, maybe its in the tonearm?
Adding to the comments below, which I agree with.
Rumble can also be caused by the turntable itself -- simply bearing noise. A good table should not produce rumble, but it could have a bearing problem. (Does yours require lubrication? Is it loose?)
LF woofer pumping (usually seen on vented speaker system, because their woofer(s) are essentially unloaded at subsonic frequencies) can also be the result of arm cartridge mis-match. Very high compliance cartridge with a fairly massive arm.
A subsonic filter is the way to go in any event. Many phono pre's have them built in (Black Cube); others have them switchable.
If you have acoustic feedback problems, experiment with different volume levels and relative placement of the 'table and speakers before spending big $$ on isolation. DIY devices suggested sound like a good alternative.
It's a turntable problem alright. Subsonic rumble. You need a subsonic filter, or better isolation of the table. Movi it farther from the speakers or add some mass under it. I made a sand-filled box about 18" x 18" x 4" thick out of 3/4" MDF. Fill with clean, white, thoroughly compacted audiophile-approved play sand (available in 50# bags at Home Depot) and cover with another piece of MDF, or even better, marble or corian. Set your turntable on top and voila! Rumble is isolated!
Sounds like a good idea.............I once used a turntable isolating stand called the "lead balloon" by Arcici. Consisted of a tall triangular stand topped odd by two lead bars which the table sat upon. Worked well.
Just like to throw my two cents in here. It is very common for a vynel record to have a slight warp at the beginning of the lead in groove. This is usually due to "Cold flow" which results from storing the record on edge. It can also result in the pressing process when the record is not left in the press long enough before removing it. Because of the low frequency variation up and down of the edge of the record a modern high-compliance cartridge will transmit a high level subsonic signal which any good preamp and amplifier will obediantly send to the speakers. Of course the speakers will attempt to reproduce that signal with the results that you observed.
All the turntable isolation in the world will not have any effect on this problem. Turntable isolators are used to prevent the vibrations of the speakers and floor movement (like walking) from reaching the turntable. In this case the record itself is producing the signal. The use of a vacuum turntable or to a lesser degree a "Platter Matter" which is a heavy, sticky mat which sticks to the record and flattens it out will help. The most effective solution is a subsonic filter which has a rolloff characteristic of at least 6db/oct at 20Hz. Hope this helps you out. U.W.
Just reread your post and I didn't notice that you said "in the middle of the record" If this is the case, look at the record from the edge inward towards the spindle. If there is no up and down movement of the tonearm you probably do have a feedback problem. If you have wooden floors (not poured concrete) then your problem is feedback and some kind of turntable isolation is in order. I just wanted to add this because I didn't want to give you the wrong information. Also just wanted to add that if it is record warpage one more solution is to obtain a lower compliance cartrige and a lighter, higher compliance arm. U.W.
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