How do you measure rumble through a bearing?

[Wakefield Turntables]

I've always wondered this and thought it might be quite useful to measure with respects to seeing how some of the home brew bearing designs and tweaks measure up against the big boys.

[YNWaN]

The easiest (though not necessarily the best) way is to use a test record with a fixed tone - record it onto your laptop and compare the frequency spectrums in Audacity.

Of course you need an appropriate test record, a laptop (or nearby computer) and Audacity (though that is free to download).

[walpurgis]

I'd have thought a record with no tone, just a blank groove would be the thing. Or an accelerometer bearing down on the top of the platter spindle maybe?

There's always a chance of rumble being on the record, produced by the cutting lathe.

[Wakefield Turntables]

Ok, so recommend me a good test record ;)

[walpurgis]

The old HFS 69 record has a rumble test and silent grooves. I have a copy, it has its uses.

[cre009]

The Hi-Fi Choice reviews in the late 80's used a precision "rumble decouple" system from Thorens.

This thread discusses the subject

http://www.diyaudio.com/forums/analogue-source/243656-measuring-rumble.html

[Wakefield Turntables]

Thanks, looks like I might have a dabble.

[brian2957]

I for one would be very interested in your findings Andy . I'm still using the original bearing on my GL75 .

[walpurgis]

The old Celestion Ditton 66 and Ditton 25 speakers would demonstrate turntable rumble. If the amplifier had little or no bass roll off, the bass driver and ABR would oscillate out of phase (it was below system resonance) to rumble very visibly.

[cre009]

The old HFS 69 record has a rumble test and silent grooves. I have a copy, it has its uses.

Just checked and all 5 of the test records I have include a test for rumble using unmodulated grooves.

[walpurgis]

As a somewhat off topic aside. I have a test CD that is good for checking what you can actually hear from your system. Sweep tones and various fixed frequencies, etc. I learned I can't discern above 10kHz :). But I get audible output at 30Hz in my small room, which theory says I shouldn't be able to do.

[YNWaN]

If testing an idler drive you will find the majority of the noise comes from the motor and may well swamp bearing noise and differences of.