rumble issues - see old thread update

Koegz,

All ported speaker cones oscillate when air inside the chamber is energized at the port frequency. When air is compressed at the port waves flow back into the cabinet at that frequency. Something inside has to move and the easiest thing to move is the cone.

Dan is correct, mine do oscillate (though never to the point of audible breakup or distortion, as the OP is experiencing).

There could be many reasons why you haven't seen yours oscillate and I'm glad you haven't. Your speaker ports are certainly tuned lower than mine. Your phono stage may have a built in rolloff or filter. Your line stage or amp may not go low enough. You may not have noticed. But this doesn't change the fact that they will oscillate if excited at the port frequency.

Want proof? Try YELLING into the ports at their tuned frequency. ;-)

Yes, woofer pumping with vinyl and ported speakers is a very common problem. As Doug has alluded to above, the problem may be more severe depending on the frequency at which the ports are tuned.

While a tonearm/cartridge mismatch is certainly going to create a problem, I'm always amazed at the number of posts in these threads on woofer pumping that absolutely insist it is a setup problem.

IME it is absolutely possible to have a perfect match in terms of cartridge/tonearm, along with a well setup properly isolated table and system and still have problems with woofer pumping with ported speakers.

I have a great deal of respect for Ralph (Atmasphere) and perhaps my amplification is just not up to the job and that is why I've experienced problems with woofer pumping with vinyl. But frankly, I doubt that. I'm comfortable with someone saying they have absolutely no woofer pumping with vinyl and ported speakers but feel that they may just have a little bit of luck going for them too.

When you look at reports of woofer pumping from audiophiles here and on other audio sites they are almost always coming from someone with ported speakers.

Sometimes, in the real vinyl world, unless I suppose you want to change speakers (or possibly amplification-not so sure about that one) you just have to bite the bullet and employ a high quality subsonic filter.

Those who continually denigrate a subsonic as a band-aid solution and negatively affecting sound quality are, in my experience, off base. My system is clearly not in the same league as some posters here, but does consist of a vinyl front end and phono preamp with a retail list price approaching $6,500 with the table mounted on a high quality wall mount with a custom shelf. No tonearm/cartridge mismatch issues. Without a decent subsonic filter (I've used the KAB, which is an excellent product, and my Aqvox phono preamp has a very high quality switchable subsonic filter), I have woofer pumping.

In may case, the subsonic is not in the least degrading of sound quality. In fact, I'd argue it improves sound quality. Now if I had no woofer pumping, it might be a different story, but I do and replacing my speakers or amplification is not a cost effective or justifiable solution for me. A decent subsonic filter is.

thanks everyone

I'll go through this thread with Richard

I do have multi weights for the triplaner and Richard and I are going to try this first- I also have the sb with the shim under the cartridge

Richard was over and said I definitely don't have an amp clipping issue - although some of the amps power is being robbed when feeding the low freq outbursts

there are some minor warped records that cleary set off pumping in the speakers, and some other's that it's so minor (but stil probably mucking up the low end) but probably still there

I want to get all the clarity out of my setup and maybe this is the limiting factor

as for suspension - I have the Silent Running Audio platforms and stand - and a very heavy platter - floor concrete - about as isolated as I can make it

it could be a room mode - I have a 14 by 27 room
long wall setup - at listening area - null against wall and reinforced 2 feet in. I've tamed slap echo with echo busters but no low freq suppression. CD's sound fine.
Table slightly forward of speaker ports which are 3' from back wall.

Perhaps if I placed the table closer to the wall on my seperate Billy Bags stand.

I'll try covering the speaker ports as well. Ports 2 2" at bottom of speaker. Jim Salk has not encountered this before with his speakers, then again, few owners with analog

Richard set this table up with a scope and the results are stunning other than the 'pumping' problem - which is there but only strong on high voumes and minutely warped records.

If this is truly a port / room issue then I'll have to look at placement of either the table or speakers. I'm a bit concerned that a subsonic filter might just mask a problem rather than correct.

Thanks

Tom

HI Tom,

I just noticed your BAT SS amp. Yeah, I doubt you're having clipping issues if that is the amp you are using. That is the worst possible problem that can occur, but it most often doesn't. Better safe that sorry though. It seems that you're woofer dance may be no different than most. Did Jim Salk think this could be detrimental to the sound of his speakers?

Tom,

If the pumping varies with volume, surely room mode interactions must be a prime suspect. My guess is that tweaking the eff. mass of the arm/cartridge may vary but will not eliminate it.

A concrete floor may dampen but it does not isolate, unless the concrete hasn't fully set and can slop around a bit. ;-) Owners of very substantial rigs on high mass stands, SRA platforms and solid concrete floors have still heard substantial improvements from adding true isolation with something like a Minus K. Not saying that would necessarily help with woofer pumping, just noting that concrete is not an isolator.