Why the woofer moves badly when playing certain LPs

Audio Technica AT150Sa
Weight 8.0g,
Static Compliance 40 x 10-6 cm/dyne,
Dynamic Compliance 10 x 10-6 cm/dyne (100Hz)

Pro-Ject the classic turntable
Effective Arm Mass: 13.5 g

Resonant frequency of arm/cartridge: 7.5Hz

Look like arm/cartridge mismatch is the problem !

mijostyn

Are you using digital room control?

No.

... even if you have your tonearm set at say 12 Hz there is still going to be plenty of rubbish below 10 Hz that is going to get through.

Not so. Not even close.
I understand that this will be a problem in many systems, and that a rumble filter may be the only way to fully correct the problem in those cases. But to insist that "plenty of rubbish below 10 Hz" is going to reach the woofers in every system and is an inherent problem in LP playback is simply false.

With the volume high enough everybody’s woofers are going to flap at least a little unless they have a filter ...

Nope. Not in my system.

Hello starbusters,

That is a classic example of a bad record. If your problem is only with certain new records, and does not happen with old records, then very probably your system is ok. That to me looks like a pressing error of the record. On the video, towards the end, it is obvious that record is warped... Bad production of the record mechanically... Not much that you can do there...Subsonic filter may help, but only to a certain degree...
Hope this helps.. 

Audio Technica AT150Sa
Weight 8.0g,
Static Compliance 40 x 10-6 cm/dyne,
Dynamic Compliance 10 x 10-6 cm/dyne (100Hz)

Pro-Ject the classic turntable
Effective Arm Mass: 13.5 g

Resonant frequency of arm/cartridge: 7.5Hz

Look like arm/cartridge mismatch is the problem !

@imhififan


If AT’s compliance is 10cu @ 100Hz you have to convert it first to 10Hz and it will be about 17cu @ 10Hz (Mid Compliance).

13.5 (tonearm mass) + 8g (cartridge weight) = 21.5g and you can add hardware too, probably 23g total.

The you can cross the lines (17cu and 23g) and it will be around 8Hz which is OK according to Ortofon:

Resonance frequency can be calculated by using the formula

f = 1000 : (2 x π x √ (M x C)) where:
f - Cartridge resonance frequency in Hz
π - 3.14159265359...
C - Cartridge compliance lateral in µm/mN
M - Total tonearm system mass which is a sum of Mass of cartridge, Mass of headshell and screws and Effective mass of tone arm (all values in gram).

• Resonance frequency within 7-12Hz is optimal for the system.
• Resonance frequency slightly outside optimal interval 6,5-7Hz and 12-14Hz can be considered as a possible that probably can be used without problems.
• Resonance frequency outside the interval 6,5-7Hz and 12-14Hz is questionable, and the system might not work properly.

The OP could use the lightest possible mounting screws to reduce the mass slightly. Or to remove stylus protector on AT if it's possible (to reduce the weight of the cartridge). 

Or to find a slightly lower compliance cartridge for that tonearm, for example a cartridge with 15cu @ 10Hz like Pickering XSV/3000SP will be a perfect match if we will check this (the resonance will be in desired range for 15cu compliance and toneam/cartridge mass near 21-23g).

BUT some people does not care about resonance frequency at all, here is the thread about it.

If AT’s compliance is 10cu @ 100Hz you have to convert it first to 10Hz and it will be about 17cu @ 10Hz (Mid Compliance).

I just estimate and simply doubled it to 20 @ 10Hz for calculation.

Resonance frequency within 7-12Hz is optimal for the system.

I'd like to have 8-12Hz as optimal value.