Measuring for rumble

[volken]

I did something a long time ago when I still had my turntalbe, a Thorens TD160. I removed the belt, started the turn table(the platter not turning) put a record on very gently, put the needle on the record and
then SLOWLY turned up the volume. I then very gently tapped the base, stand and so on and listed to what was coming through the speakers. Not a test of rumble when playing a record but it helped me make some mods to reduce sound that was not part of the sound coming off the record.
I guess rumble is part of the record surface that is out of our control when trying to reduce surface noise.
PeterC.

The TD160 has very little rumble.Motor vibration at 100 (120) hz is the main source , its transmitted by the chassis and the belt. Most time audible when the needle is in a silent groove or at the end of the record.
Tuning from the phase capacitor can improve this with min.10db .
depending on the state of the motor.

Volken

 

[Gold]

I am not regular poster here but I have an interest in rumble measurements.

The way the OP measured the rumble is fine. The issue is that while the characteristic of the noise is easily understood the absolute level of the noise is unknown.

The scale on the screen shots is in dBfs. This digital scale has no direct relationship to an analog level. Analog levels are measured against a Standard Reference Level like dBu, dBm and dBV.

To make a more meaningful measurement you should first record a test record 1K tone at the Standard Reference Level. It doesn't matter what it is in cm/sec.

Then record the blank section of the record. In the computer add gain until the noise is at the same level as the tone. The amount of gain you have added is the amount of rumble in dB. Against the Standard Reference Level of the test record.

This number will include any rumble in the cutting and manufacturing as well. If you measure a bunch of blank groove and average you will have a good idea of what's going on.

There was a DIN standard for rumble measurement. I have been unable to determine if there was ever an NAB standard.

I am just getting up to speed for proper measurements. I have a Neumann RUMS75 rumble meter and a DIN 45544 rumble test record.

That's how it was done in the old days.

Paul Gold
Salt Mastering

 

[pjrebordao]

Hi

I'm new here and also I'm trying to compare rumble between a few TT's.
I have a HFS75 test record and the rumble test track starts with a 1Khz tone for some seconds followed by silence.

I suppose the purpose of the 1Khz tone is to enable us to equalize sound levels between several tests so that we can compare rumble figures.

However, I'm using Audacity and I don't know how to equalize a sound file to a certain peak level. I used the Amplify effect, but I didn't get the peak level that I intended.

Can anyone help ?

Thanks