Speed Stability

I'll support Frogman's general assertion, both from theory and from my own listening experiences and Paul's.

All turntables exhibit speed instability. There are no exceptions, only differences in degree and kind. When a mechanical drive system is confronted with a variable load (ie, stylus drag) at an unpredictable mix of frequencies, rise times and amplitudes, instabilities in platter speed are inevitable. The instabilities can be mitigated by good engineering of many kinds, but they cannot be eliminated. We can use Newton, we can't repeal him.

Can any particular listener hear the speed instabilities of any particular table? Who knows? FWIW, like Frogman, Paul and I have heard few TT's that don't shout certain speed instabilities to our ears.

We aren't musicians, but the music we enjoy is pitch accurate and rhythmically precise, so very revealing of speed instabilities. DSOTM won't tell you much unless the table really sucks. If you want to diagnose a table's speed stability, listen to Mozart or Bach on authentic style instruments, as in the recordings by Hogwood or Harnoncourt for example. Held notes and complex passages in music and recordings of great clarity will reveal TT weaknesses that are masked in heavily amplified and mixed music.

At RMAF 2008 Paul correctly identified 10-15 rubber belt drives without knowing anything about the tables, without even seeing them, just from the sound as we walked in the door. On 2-3 occasions he and I actually said "rubber belt" BEFORE we walked in the door, the time smearing was that obvious.

We brought just one LP to RMAF, an original instruments rendition of certain Vivaldi concerti. I chose it specifically because it reveals two things: speed instabilities of a subtle kind and fundamental/harmonic imbalances. I wanted to hear how Mosin's Saskia table handled subtle speed challenges (I knew it would handle the big ones). Paul wanted to hear if a certain cartridge would mis-handle fundamental/harmonic structures in the way he had predicted (he gets that way!).

We only bothered to play that LP in three rooms, Mosin's, Highwater Sound #2 and the room with that cartridge of interest to Paul. The Saskia handled this LP exceptionally well. The TW Acustic Raven 3 in Highwater #2 was also very listenable. (OTOH, the cartridge mis-performed exactly as Paul had predicted, though worse than even he expected.) We didn't bother to play this LP in other rooms, since we were there to enjoy ourselves. ;-)

FWIW, digital also has speed stability challenges, which we refer to as "jitter". Jitter doesn't sound like the speed instabilities from a TT or tape deck and we don't hear them as time domain issues. They are, but on a shorter time scale and with non-analog consequences.

Hello Doug,

Interesting feedback. Was the misbehaving cartridge in the Highwater/TW setup or the thrid room you eluded to. Any comments on the gear in room-3?

Also, can you expand on the differences between Saskia and TW AC on this record from a speed stabiity standpoint. while there are many diffeences between the tables, it would be interesting to get your perspective between these implementations of idler and belt drive from a speed styability standpoint.

Cheers

Andrew

Hi Andrew,

That cartridge was in the unnamed third room, which I won't identify here. We learned that lesson! (It wasn't a Tranny of course. Your Orpheus would shame it, though the other cart costs far more.)

I can't compare the Saskia and TW AC directly, since nothing about the two systems was very similar. All I can tell you is what the better one *didn't* do.

The Saskia maintained an unflappable rhythmic rightness and drive. It refused to distort any kind of time domain information, whether macro-dynamic big bass and drums or held notes over the fastest mandolin plucks or even the nano-dynamic textures from bow, resin and string (all from that Vivaldi LP). I expected it to handle the big stuff well. I was happily surprised that it seemed to handle the fine stuff just as well. I'd have to hear it with a faster, more resolving arm, cartridge and tweeter to be certain, but its speed errors might fall below my own threshold of detectability. (I don't think anything falls below Paul's, when he's on he's scary.)

The sound in the TW AC room was a tiny bit softer, but never "wrong". Paul gave it his overall best room in show. We didn't necessarily attribute that hint of softness to the table. There were too many variables. We were frankly surprised that a table with an elastic looking belt performed so well. I believe TW's belt material is proprietary, as it should be based on what we heard.

So, all I can say is that there was probably LESS artificial softening of rise times and transients from the Saskia than from any table I've heard.

Our own table (now more carefully tweaked and notably better what you heard during your visit) does pretty well. It has to, since when it's wrong it drives us batty. I'd have to hear two tables in the same system to make actual comparisons though. Tough to do with these 80+ lb. beasts.

Thanks Doug.

Your report and descriptions are clear, concise and invaluable for those of us who aren't fortunate enough to have attended.

Regards
Henry

Macd, the SDS was a great upgrade when I had the VPI table. It truly allows you to lock in the speed and forget it. Getting the speed right gets the pitch and pace of the music correct. Having said that, I did check the speed every month or so because belts do stretch and change a little but I never had to adjust too much. The SDS also is an AC filter so it probably helped to lower the noise floor. I recently purchased the Continuum Criterion and I can honestly say I have never heard better speed stability and rock solid soundstaging from any other turntable I've listened to except the Caliburn, Continuum's top model. It must be heard; built like a tank and the sound amazing.