I was looking through a legacy audio folder & found Boxport. It's been a while since i fired it up, as i use other software. Anyway, out of curiosity when i ran it, i discovered that by selecting two drivers in the same box, BP shows EBP as double what it is for one driver ! The 2 driver box was twice the size of the single. The box tuned to the same fb.
As EBP = fs/Qes & in this case fs = 33 & Qes = 0.3 = EBP = 110 But with the 2 driver box EBP = 220. As magic doesn't exist, either BP is wrong, or EBP does double as in the above example. If so ? then combinations of different driver counts & volumes, should lead to increased EBP ! What's your take on it ?
The www has gone sdecnet.com but it & the program is available from the waybackmachine www if you want to try it.
As EBP = fs/Qes & in this case fs = 33 & Qes = 0.3 = EBP = 110 But with the 2 driver box EBP = 220. As magic doesn't exist, either BP is wrong, or EBP does double as in the above example. If so ? then combinations of different driver counts & volumes, should lead to increased EBP ! What's your take on it ?
The www has gone sdecnet.com but it & the program is available from the waybackmachine www if you want to try it.
Using Thorsten's method for calculating compound drivers, Qs sum as follows:
SQRT(((Q5*Q5)+(Q6*Q6))/2)
so you can see they do not add linearly
SQRT(((Q5*Q5)+(Q6*Q6))/2)
so you can see they do not add linearly
My take FWIW is to ignore EBP. At best it's a simplistic 1st order approximation, and tells you nothing you couldn't work out by taking a one second gander at Qt and F0 (Fs) without needing to do even the simple calculation involved. 😉 People tend to set rather too much stock by it; like most things in audio it's about shades of grey (preferably not 50).
@ PeteMcK
OK, Thanx
@ Scottmoose
My main interest in this, is that using BP, EBP doubled for what it was for one driver with the 2 driver box which was twice the size of the single box. So, BP is either wrong, or it's true ? If it's true, it's something i've Never heard/read about Anywhere before, Ever. Which, i think is a very interesting positive side effect, which could prove beneficial to some !
@ GM
Also nice to see other links 😉
OK, Thanx
@ Scottmoose
My main interest in this, is that using BP, EBP doubled for what it was for one driver with the 2 driver box which was twice the size of the single box. So, BP is either wrong, or it's true ? If it's true, it's something i've Never heard/read about Anywhere before, Ever. Which, i think is a very interesting positive side effect, which could prove beneficial to some !
@ GM
Also nice to see other links 😉
Right, in short; double the drivers and Qes is reduced by SQRT[2] [2^0.5 = ~1.414], ergo it takes four drivers to double EBP [Qes/2]:
0.3*~1.414 = ~0.212
EBP = 33/~0.212 = ~155.66
This indicates that while one of these makes an OK horn driver with a 'x' compression ratio [CR], two theoretically allows a higher one, highlighting Scott's insinuation that basically if you don't know this about horn design you probably don't need to know because for sure it has little/no impact on sealed Vs vented alignment choices where at best, EBP = Fs/Qts seems more appropriate as proven by George Augspurger's max flat impedance TL alignments [to my satisfaction anyway].
GM
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