rumble issues - see old thread update

Hi Tom,

I spend Sunday at Doug's and we were thinking about your issue. There were a couple of noticeable woofer excursions but I believe each could be attributed to vinyl anomalies. I think from your description your woofer pumping is much more frequent.

There are obvious differences between speakers. Driver suspension, crossovers, internal box pressures, etc. The Salks may simply be use drivers with different mechanical properties and parameters. The fact that your friend also has Salk's and they pump as well is telling us something. I do remember my 10t being susceptible to woofer pumping with vinyl. A local brick and mortar guy once told me "Perhaps it is time to put the covers back on and quit watching them." This was after he was satisfied no damage was being done. He's an experienced Linn-ey. Don't rule this out as possibly the final solution. If you don't hear problems, don't go looking for them. :-)

If this is increasing with volume, Doug could be on to right track. It should be easy to get an idea if this is the problem. If you haven't already tried this, here is an experiment that may help show you something. Try moving your speakers farther into the room at least 4-5' from any wall, back and sides, and see if the pumping decreases.

BTW, what are the room dimensions? Sorry if you previously posted that information. It is possible to calculate room nodes and your speakers may indeed be close to one.

What is the weight of your Universe? I'm assuming you have the extra weight from the little plate.

I seriously doubt that anything you do to the tonearm will fix this without choking off the music.

I agree that the first thing you should try to ascertain is the pumping caused by airborne or mechanical anomalies. So ...

- move the speakers
- put up some kind of baffle between the TT and the speakers
- move the TT off the rack onto the floor or in another room
- check and double check your cartridge alignment
- try a different counterweight and play with location (heavier weight closer to the pivot point, or lighter counterweight placed farther from the pivot point)
- try a record clamp or periphery ring (if you can) to see if you can get a better interface between the vinyl and your platter surface

If that doesn't work then check your cartridge compliance and theoretical resonant frequency. Add something to the headshell to increase the mass of your tonearm (rebalance and reset it all, of course) and see if that alleviates anything.

In my case it was definitely caused by the arm-cartridge compliance. Switching cartridges removed the problem entirely.

Good luck,
Bob

I usually run the ZYX a little more than 1.75 grams FWIW, more like 1.85-2.0.

hi guys

just reading your insightful posts

latest update

less woofer excursion after using granite slab under table on craz rack - it eliminated or greatly reduced isolation
slightly warped records set it off, but most have much more minimal speaker pumping (I can live with if not damaging cartridge)

craz platform is floating and works great with electronics but not with turntables - I could tap it and get noise through the speakers - not now as I replaced it with 3cm granite

pumping is more pronounced on outer portion of record which fits with the warpage scenario
so I may have similar observations as what you saw at Doug's (room and port elements may add to this)

the arm is still resonating (as seen on the scope) - calculations and your experiences as well as Mehran's and Thom Mackris say this should work and it seemed to till I got a low end pre amp -the doshi

weight 1.75 ish - have the shim and adding a quarter on top of the cartridge didn't work either
I tried the mass counterbalance variations along the arm

room 15 by 27
I have system/speakers on long wall using Cardas nearfield setup
There is a dip in volume om the back wall behing the couch - increases two feet into the room
speakers 3 feet into room. CD's sound great in the room with no noticable freqency humps

haven't tried the speaker placement
do have some echo buster type iso panels I could stick between speakers and equipment

alignment is dead on as shown by scope with test records and hearing music

I have a heavy anvil I can use on the top of warped records
is the clamp more effective

the pumping at present isn't really audibly effecting the sound anymore or minimally except for warped records

Richard is also going to bring over a few other cartridges with lesser compliance and see if we can remove resonance

this may be as dan and bob suggested - live with it

I think I'm getting closer, just want to isolate this and tweak everything out of my system

enjoy music tolerate equipment ...

thanks for all the helpful insight,
much appreciated

Those resonance figures you posted are absolutely fine. This is not, IMO, a tonearm/cart resonance issue. That combination is used by many people with no issues. Now, if one is using the Universe without one of the plates, 5 grams may be too light.

I have no idea what you mean by low end preamp.

Doug's B&Ws do not pump in the least with almost every record we played. There were maybe 3 times over a 6-7 hour session that I noticed woofer excursion out of the norm. We have also mounted his Universe on my TP and had no problems.

But it sounds to me like you are getting to the issue. I think you're rack, or what is under the table, is the problem. The granite shifted the resonances up higher. I know because I also have granite under my table as the shelf for my sandbox. It sucks because it does cause smearing in the midrange. I use Stillpoints between my plinth and the granite to remove the ill effects from the granite.

FWIW, I can tap on my stand and hear it through the speakers. That proves absolutely nothing about how the table is performing, IMO. Well, unless one tends to tap their stand while they listen to music.

No offense, but who is Richard and why is he intent on proving your arm/cart match is wrong?