[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [ARSCLIST] Absolute Polarity
On Sat, Oct 18, 2008 at 6:02 PM, Richard L. Hess
> While we have Clark Johnsen's attention here, I do have a question.
> When we look at audio waveforms, we often see that the peak amplitudes are
> assymetrical while, obviously the total power on each side of "0" is the
> same (or there would be a DC offset).
So far, so good. Only, it's not just the peaks that differ. So do the
> In order to visualize the waveform, think of clock or watch hands that are
> balanced, but one side is longer while the other side is wider, but shorter.
> Same mass on each side.
> Clark, are the higher peaks usually the positive peaks?
Hmmm... Well they are if you think of "high" as being above the X-axis. But
sometimes the peak occurs beneath, but greater in amplitude that the top
> Let's say for brass and wind instruments?
> Drums--assuming distant mic placement, not something inside the kick?...
> What oddities have you found in this?
Well... there are instruments that exhibt a pronounced polarity signature,
and then there are others.
Take just drums. The kick drum and the snare drum (inter alia) produce *
compression* transients. Compression transients are fairly easy to
distinguish from their (electrically-caused) reversal. But then we have the
tympani, which produce *rarefaction* transients. Are these any less "peaked"
than the compression variety? Offhand I don't know, but they are somewhat
harder to isolate when reversed, as the ear seems to prefer hearing
Some organ stops are one way, others the other -- making that instrument
difficult to tell in this regard.
> Thanks--that would be helpful in re-setting the absolute polarity in
> transfers of tapes that did not pay any attention to this.
Waal... no recording studio has ever paid particular attention to this vital
aspect. (Add that to my list of beefs with so-called professional recording
and mastering engineers.) With one exception: Most of them do try hard to
keep the mics in line.
But then there are the electronics, and the toys, and the general confusion
over XLR polarity. The best one can ever hope for, is that all the stems and
channels will be the same way. Whether that way conforms to some larger
specification, is left for the end-user to decide.
And just to make this clear, there is NO larger specification.
With 78s, LPs and CDs (and DVDs!) having all these decades lacked such a
standard, it's left to the listener and his ear to set it right.
A pain in the ass, for sure! But once a listener becomes aware of this
sonic phenomenon, few are able to tolerate its being wrong anymore.
One small start might be for every studio to make even just its own internal
production conform to one polarity, day in, day out -- but there's never
been any reason for them to do so.
> I do have a copy of "The Wood Effect" and don't think that was mentioned in
> there, but maybe I missed it.
It's all there. I mean, this discussion. The full title is *The Wood Effect*:
*Unaccounted Contributor to Error and Confusion in Acoustics and Audio* There
*are* parts I inadvertently omitted, however. Some of these are offered in
but there are others still.
If anyone's interested in this pretty good book, a couple dozen copies are
still left. Only $20 + shipping.
> Richard L. Hess email: richard@xxxxxxxxxxxxxxx
> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/contact.htm
> Quality tape transfers -- even from hard-to-play tapes.