The Talking Machine Forum — For All Antique Phonographs & Recordings

Henry wrote: Tue Nov 08, 2022 11:39 am You will not "hear overtones" unless the fundamental is also present; indeed, that is a requirement.

Well, not really... It's just a matter of which name you attribe to what. All sounds (all frequencies) are "created equal" and behave the same way, wether they are born as a fundamental or as an overtone of such fundamental. As user Anchorman has already recalled, if you record a sound (or you air it on radio, or deliver it to a telephone line, whatever) and the bandwith is such that the fundamental component of the tone will not be able to pass through, while the overtones are within the bandwith and will pass through, you will then obviously hear the overtones alone, even though the fundamental over which they were generated is no longer there.

At that point, if you really wish, you can no longer consider as "overtones" of anything the sounds that you hear, or you can rename "fundamental" the first harmonic that is still hearable, and "overtones" all the frequencies above it. But, as said, this is just an empty exercise in naming things: it won't change the reality a bit.

About your example concerning the 60 Hz hum, if you would listen to how a pure 60 Hz tone emitted by a high quality function generator really sounds through a top quality hi-fi headphone, I believe you would also realize that what is usually referenced to as "60 Hz hum" is instead mostly a sum of overtones of that frequency.

This article should clarify things and settle all doubts: https://en.wikipedia.org/wiki/Harmonic_series_(music)

Henry wrote: Wed Nov 09, 2022 3:10 pm This article should clarify things and settle all doubts: https://en.wikipedia.org/wiki/Harmonic_series_(music)

settle what doubts? Marco seems to understand what I was saying... psycho acoustics (at least when people have relatively normal hearing) will fill in the blanks for us when certain sounds are not there. That was all I was trying to say. We all understand that to get an overtone of a 40hz note, you need the 40hz note to play... but when all of it is recorded, and played back minus , your brain will trick you into think certain sounds are there, even when they are not. This is why if you listen to a tone generator playing a 30hz triangle wave, it sounds like a deep note even on crappy computer speakers, but if you play the 30hz sine wave you basically get nothing. The computer speakers (at least the one's I'm currently listening to) cannot play much of a 30hz sine wave, but the 30hz triangle wave comes though with much more apparent volume/loudness.

https://onlinetonegenerator.com

Ethan wrote: Tue Nov 08, 2022 11:02 pm

Orchorsol wrote: Mon Nov 07, 2022 11:02 am

Ethan wrote: Sun Nov 06, 2022 1:50 pmroughly a 100 Hz cut-off for the Mk IX and 80 Hz for the standard Xb—Does that seem accurate to those of you who have heard them in person?

This seems approximately right to me, or a little above those figures - from memory, around 85-90 Hz for the Xb and 75-80 Hz for the Xb Oversize.

Some years ago Bjørn Kolbrek (who co-authored 'THE' vast text book on audio horns in recent years, mentioned by Graham in another thread) visited Graham, Ian Maxted and myself and made numerous measurements on various EMGs and Experts - both from frequency test 78s using various soundboxes, and by injecting frequencies from a tone generator. Fascinating stuff!

That matches what I’ve heard for the Xb Oversize—hadn’t read anything about the Xb, though; thanks! Any idea about the IX? And do the Xb and Xa sound any “peakier” than the Ovesize? I’ve read that a too-small mouth creates resonance and a very uneven response near the cut-off, but I’ve never heard EMGs described that way, regardless of horn size.

It certainly does sound fascinating! I don’t suppose anyone recorded the results…?

Yes! It's a long time since I was in touch with Bjørn, but I've reached out to him and asked if I can share the data with yourself and anchorman.

What is your source for the acoustic lengths? The measurement, I believe, should be from the diaphragm to the bell mouth. I have attached a pdf of an advertisement of the Mark IX which states the overall acoustic length is nearly 7 feet, nine inches. Would love to know the acoustic length of a Xb Oversize.

Ethan wrote: Sun Nov 06, 2022 1:50 pm Does anyone know the frequency responses—especially the low-end cut-off frequencies—of the EMG Mk IX and Mk Xb (not the Oversize)?

Based on the length measurements that Graham Rankin gave in the thread about the vertical-horned EMG, and assuming a roughly 1.5” horn throat diameter, I found the equations pictured below for the Mk IX and Xb's respective approximate horn contours, which would indicate roughly a 100 Hz cut-off for the Mk IX and 80 Hz for the standard Xb—Does that seem accurate to those of you who have heard them in person?
EMG Mk IX Possible Equations.png
EMG Mk Xb Possible Equations.png