Hi Dave & Paul,
If you consider the bass portion of the curve separately then, yes, the turnover +3dB point is relative to the top end of the spectrum, i.e. 20 kHz. That's what I tried to explain in a previous email. Even with bass turnover points of 500 Hz or lower, 1 kHz will be slightly above 0 dB because filter response is gradual, not instantaneous.
But, as I illustrated in my Columbia LP curve article, in relation to the NAB curve with its alleged 700 Hz reference point, when you combine the two curves onto a single graph, you can put the 0 dB reference wherever it's convenient. Usually it's 1 kHz, but NAB chose to make it 700 Hz.
I can email you some simulations to illustrate this, off list. Has anyone tried sending files to the list via WeTransfer? The list would get a download link from WeTransfer. I've never tried it. I may not be able to do this right away, since I'm trying to finish a book review and a recording review for the Journal by Monday.
PS - Check Esoteric Sound's web site, and the manual for their Re-Equalizer, for Mike's views on which labels used a 1 kHz turnover. It's only a handful, and notice that the treble region is usually flat, or has a very high rolloff point: It would make little sense to have a 1 kHz bass turnover with a treble rolloff point less than an octave away.
Audio Engineer Emeritus
The Crane School of Music
SUNY at Potsdam, NY 13676
"Great art presupposes the alert mind of the educated listener."
"A true artist doesn't want to be admired, he wants to be believed."
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Paul Stamler
Sent: Saturday, July 29, 2017 3:39 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] EQ Turnover
What records have a turnover of 1,000Hz? The only listings in my references are early Brunswick 78s and Schirmer recordings (speed not specified). Anything else?
On 7/29/2017 2:24 AM, Dave Cawley wrote:
> Hi Gary
> I understand that. And when for example the turnover is say 500Hz, then 500Hz is +3dB above the level of 1Khz and any flat part of the curve. So to check accuracy of an EQ you normalise the 1Khz output measurement and go to 500Hz which should be +3dB higher.
> But if the turnover is specified at 1,000Hz then it isn't possible to get it +3dB relative to 1kHz because it's one of the same thing, so is it then permissible to measure from an otherwise flat part of the curve at say 5Khz ? And is this documented anywhere ? I have, I think, all text books on the subject but can't find a definitive reference. I am looking for both friendly advice and also a definitive reference please.
> Other experts, feel free to chip in too ?
> Dave (BTW Gary sorry for the spelling mistake)
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