Hi Tom,
this is not unusual at all with ported speakers. I used to deal with this back when I had Aerial 10t's. I'm pretty sure we can rule out the Galibier bearing and table setup. :-)
That leaves the warps and off center pressings, which is something we vinyl junkies have to contend with.
I don't believe Nick uses sub-sonic filters (a very good thing, IMHO), but you are correct that this woofer dance is likely adding distortion. KAB sells a sub-sonic filter and adding that may be the lesser of two evils. It would be something to try.
I agree that you should be concerned about possible clipping, so be sure to keep the volume to reasonable levels if your amps are not up to delivering lots of current. |
I "got" this stuff from my own experience with ported speakers and preamps that don't roll off. I have sat a watched Doug's speakers do the dance. I have seen just about ever other ported speaker do this with analog. You have a different experience. I won't say anymore about this because I can't say anything nice at the moment. |
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? |
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.
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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? |
HI Richard,
Yes, I never liked the idea of air and pumps.
I did have some time this morning to scan the Halcyonics. The only issue I have with it is that it is active, however it is reported to have a faster damping time. Yes, this kind of device does put things in another league.
I also like that workstation table on the MinusK website. Change out the adjustable feet with spikes. A Billy Bags short table would also work great under one of these, so it would seem.
Employing a MinusK would probably allow me to play through the next quake in the good ol' granite state. :-) |
What I find bothersome about the MinusK, and I fully admit I have no experience with it, are the reports of these going into oscillation by something like a cd drawer opening and closing. It seems that they do dampen out and work, but I can't imagine my gear on top of something that moves when queuing a record. I suppose I'd have to see it, but it doesn't sound comforting. :-) |
Yep, the oscillations of the craz were in my brain, but my fingers don't move as quickly as my thoughts. I tend to leave out parts. In this case, skipping ahead to the problems with granite.
Adding a suspension under a non-suspended table is not the way to go, IMO. |
Nope, no dogma here. I specifically included this is my opinion.
The granite was added on top of the craz, if I read Tom's post correctly. If that extra mass reduced oscillations getting to the speakers, something is moving too much. I didn't mean to point directly at the Craz, just whatever the table is sited on. But if that is the Craz, well not everything works in every application.
The Stillpoints are the limit I will go with compliance under my Gavia, and even then I know it is a compromise to the sound I could get with a braced, aluminum shelf on my sandbox. If I ever grow tired of that beautiful Dakota Mahogany granite it will be gone along with the Stillpoints. Remember, I'm coupled to a concrete sub-floor so I don't have the issues of a suspended floor. If I did I might own something other than what I now own. Suspend away if you want or need to. I don't find it necessary or desirable under my table to get a low enough noise floor.
Yes, there are things I hear in the mid and upper ranges differently in your system and mine. But down low is a different issue, and that's what where talking about here. I dont hear any down low in your system, I never have. I have to extrapolate what I think it would sound like. But I realize you do have your system tuned for a different sound than I based on our different preferences. Even as close as our systems are, they are still as different as the music we each prefer. |
I just finished reading up on that device. Oh, yeah. That MinusK is a completely different league. It had better be for that price. Then again, when you look at the price of decent equipment racks it doesn't look as expensive. |
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I think that if you filled the bearing all the way there should be no reason to worry about oil. There is no place for it to go. The bearing itself? Ah, no. ;-)
Got it this time. The one SRA turned out to not be a good match with the table. There is one layer peeled back, perhaps the only based on your results. BTW, have you tried the Gavia directly on the top shelf of the Craz? Heck, you could even move the Gavia to the floor since you're on a slab. Might tell you something.
I am not familiar with your amps and speakers, but it seems they are just going to move a bit with vinyl playback. Perhaps Atmasphere will have some input on this.
If things sound good, don't worry, be happy, and listen. Put the covers on if it bothers you. :-) |
