Cartridge is probably OK, not worn, no sign of wear, or mistracking. Like I said, it is not the Io phono stage, since when the stylus is lifted from the groove, the woofers stop pumping. I have tried a platter mat, and different weights – no difference. Mechanical problems? Player is level, on a solid stone rack. Testing with sthetoscope and fingers: very silent. I do find that the shaft that holds the spindle could be tightened a bit, but I don’t think this relates to the pumping. Also, this is clearly not related to airborne feedback, position of speakers, damping, etc. Either, the woofers pump (stylus in the groove), or they don’t. It happens on all kinds of records, is not dependent on warps or record problems.
My new diagnosis is this.
1) Like many of you have said, the Lyra Atlas /SME V combo can be non-optimal – the resonance is too low. Maybe, those who don’t hear problems, have a less resolving system at low Herz, or a subsonic filter. I think I have solved the numbers mystery. The Atlas specs say: “Compliance 12 x 10-6cm/dyne at 100Hz”. But the calculators I have found (e g at Vinylengine) measure compliance at 10Hz. Noone seems to know the exact conversion, but a rule of thumb is to multiply the 100Hz value with 1.5 or 2 to get the approximate 10Hz value. This means that the Atlas compliance is in the region 20 to 24 (not 12). Using this value in the calculators, I do get a too low resonance for the combo, around 7.5 Hz. This fits quite well with my Hifi News record lateral test result (6-7Hz). Since obviously people have used Lyra’s with similar compliance to the Atlas and SME V arms to great benefit, the correct term is probably “borderline low”. It can be good enough, or not, depending on the system.
2) With this “borderline low” situation, the cart/arm picks up too much of what happens down in the subsonic region. I tested with a record at the end of the runout groove, just now. The usual situation where the LP is still going round at the end, with an audible pop for each revolution. The pop is clearly audible. The pumping is only or mainly visual. I think they interfer with each other (indicating that the pumping is no good for the sound). I also found that there is a rythm to the pumping. A pattern is repeated for each revolution, so if I change platter speed from 33 to 45 rpm, it happens faster. My conclusion: The cartridge picks up player rumble. This is not because the player is bad or poorly tuned (the Hanss T30 has received a lot of praise for its silent motors, combined magnetic/ceramic spindle system, speed stability, “inflappable” quality etc) it is just what you get when you turn on a flashlight or microphone down low, in the 5-7Hz region. Assuming that the low resonance acts like a microphone (which fits my testing).
Agreements – or not? Am I overlooking something?
So – what to do?
Some of you say a filter works, others that it doesn’t. For me, with a great cart and arm, prone to run many years ahead, it could be worth trying. Other options (change cart, arm) are far more expensive. Suggestions welcome. There are small XLR filters, but the ones I’ve seen on the net are for microphone use, with too high cutoffs, 100 or 50Hz.