Freq response equation

[audiorep2]

Back in the early 70s when I took JBL training for reconing ( at Gould Marketing , Montreal , Canadian JBL distributor , Herb Goldstein was the instructor ) we were taught an equation to determine aural balance of speakers . You took the lowest measured frequency and the highest ( at -3 db ) , and multiplied them together . If the result fell with a certain range , the speaker would sound balanced . What was that range ?

[grumpy]

I get the idea, even if it's a very rough rule of thumb ... 400,000 to 600,000?... perhaps higher as the span gets smaller?
Shooting for a system that isn't overly bassy or trebly... trimming both relative to the mids would make it sound relatively 'balanced'.
Seems like dropping the same number of octaves at either end would give a roughly reasonable result ... to a point:

Using 600,000 as an example:

20-30000
40-15000
80-7500
160-3750
320-1875

[audiorep2]

Exactly !

[speakerdave]

I remember it as not a range, but a number: 400,000. 20 to 20000 being typically regarded as the range of human hearing, possibly why those particular numbers still appear in stats today.

The developer of the the full range that became Hartley, for example, settled for 45-9000.

Grumpy's 40-15000 example is probably closest to the range most often actually found, so 600,000 may be more correct.

Never more than a rule of thumb anyway.

[grumpy]

Ha. Yeah, that's where I started. Seemed to sort of break down (in my thinking anyway) when the bandwidth got smaller when I ran some numbers.
But as a first order guesstimate, something around that value makes sense.

[audiorep2]

Thankyou gentlemen !!

[audiorep2]

The more my senior brain thinks about it ,... the more I tend to think the range is 600,000 - 720,000.