EBP (Efficiency Bandwidth Product):
used to determine best enclosure for specific subwoofer.
EBP = Fs / Qes
50 or less = Sealed / 4th order Bandpass.
50 - 90 = flexible enclosure options.
90 or greater = Ported / 6th order Bandpass
Best volume for sealed enclosure:
First find the value of X...
X = (0.70 / Qts)^2 - 1
Then find the enclosure volume
Vb = Vas / X
Vb will be given in same unit of measure as entered for Vas
To find the frequency of the box:
Box Freq= (0.7/Qts)Fs
The Golden Ratio:
Used for optimum sound in sealed enclosures
The ratio is the cubed root of the determined enclosure size in inches (x1), (x.7939), (x1.2599)
For example if your internal volume in cubic inches needs to be 2160^in or 1.25^ft.
Take the cubed root of 2160 (12.927) and multiply it by 1 to get side A
A=12.927
To get side B multiply side A by .7939
B=10.263
To get side C multiply side A by 1.2599
C=16.286
To double check multiply side AxBxC, and you should get within 1 of 2160
Tuning a ported box:
To tune a ported box to a desired frequency, use the following equation:
LV= [(1.463 x 10^7 x R^2) / (Fb^2 x Vb)] - 1.463xR
Fb - is the desired tuning frequency of your enclosure in Hertz.
Lv - is the length of your port in inches.
R - is the inside radius of your vent tube.
Vb - is the internal volume of your enclosure in cubic inches. To convert cubic feet to cubic inches, multiply by 1728.
Transmission line length:
First, find the length of the speaker’s Fs by dividing 1120fps (speed of sound) by the Fs of the speaker. (1120fps / 40Hz = 28’)
Line length = Fs wavelength / X
X= 4 (25% of wavelength gives you a 90degree phase shift)
X= 2 (50% of wavelength gives you a 180degree phase shift)
X= 1.333 (75% of wavelength gives you a 270degree phase shift)
Temperature, elevation, air pressure, and humidity all effect the speed of sound. If you wanted to get technical, plug these factors into winisd, and it will calculate sound velocity for you. Temperature is the biggest factor in sound speed.
Comments...??
Victor..
Replies (6)
uochronos on 02/5/2005 14:33:58
i currently have a Elemental designs Kx series sub in a 1 cubic foot sealed box... before i had it in a 1cube sealed bux that was to the golden rule,... well because of the shape i had to face the middle of the truck and it sounded ok now i have a box thats the same exact size just a better shape and it is facing up and this one actualy sounds better just because i was able to move it to a proper location....
i would think if your a huge SQ freak into compitition the golden rule may help a tiny bit.. but in general builds i dont see alot of use because usualy your buidling a custom box to fit the car as much as the sub... and in alot of vehicles the golden rule shape just wotn fit properly... actauly loseing SQ.
Chronos
Victor on 02/5/2005 15:02:34
agreed...
But this is what the basics say. Just wanted to share that bit of info.
I also agree that shape, size and orientation of every enclosure is influenced by many many factors..
cant lay down a rule in this area. but as always , be it Math or Physics there are some postulates written down, this seems to be just one of them.
Am just trying to share some extra bit of info, and text book notes..
Victor..
cplkittle on 02/7/2005 00:47:35
Those equations took me almost 2 months to research, and in the last year I have found that all are very accurate. The only thing is the Golden ratio is for enclosures with no polyfill or other sound deadening material.
Victor on 02/7/2005 13:41:03
Hey kittle. .. do u still have the notes on the derivation of the Golden ration, I have researched a lot on it too.. it wud be good to share something here..
Victor..
cplkittle on 02/7/2005 20:01:47
This is the only paragraph I kept on it...
The "Golden Ratio" should be used whenever possible unless space is restricting which is a normal occurrence when dealing with an automobile. This ratio is 1 x .7937 x 1.2599. For subwoofer cabinets, dimensions with this ratio will sound less boomy and have less panel vibration. To figure the dimensions that you need for a particular volume, without trial and error, you must have a calculator with a "cube root" function. Find the cube root for the volume that you want.
You may be able to find more with a search for "acoustic suspension". I can't remember what all I looked up to find this. I also have noted some of the pages in which I found and or copied material in my "overview of enclosure designs" DIY article.
Also, I just ordered two books from amazon on acoustics.
On the Sensations of Tone by Hermann Helmholtz
and Master Handbook of Acoustics by F. Alton Everest
I will post a review and/or recommendation if I find these useful. Both cost me under $40 USD. I know the Master Handbook of Acoustics is geared toward room acoustics discussing resonance, refraction, reverberation, and diffusion; but I believe with a thorough understanding of the basics on a large scale I may be able to draw a parallel to vehicle acoustics.
Victor on 02/8/2005 01:21:55
nice going ... i guess we can be very helpful to each other.. cause i am doing a lot of research on sound, propogation of sound, acoustics, sound illussion etc..
lemme know if i can share something with u too..
used to determine best enclosure for specific subwoofer.
EBP = Fs / Qes
50 or less = Sealed / 4th order Bandpass.
50 - 90 = flexible enclosure options.
90 or greater = Ported / 6th order Bandpass
Best volume for sealed enclosure:
First find the value of X...
X = (0.70 / Qts)^2 - 1
Then find the enclosure volume
Vb = Vas / X
Vb will be given in same unit of measure as entered for Vas
To find the frequency of the box:
Box Freq= (0.7/Qts)Fs
The Golden Ratio:
Used for optimum sound in sealed enclosures
The ratio is the cubed root of the determined enclosure size in inches (x1), (x.7939), (x1.2599)
For example if your internal volume in cubic inches needs to be 2160^in or 1.25^ft.
Take the cubed root of 2160 (12.927) and multiply it by 1 to get side A
A=12.927
To get side B multiply side A by .7939
B=10.263
To get side C multiply side A by 1.2599
C=16.286
To double check multiply side AxBxC, and you should get within 1 of 2160
Tuning a ported box:
To tune a ported box to a desired frequency, use the following equation:
LV= [(1.463 x 10^7 x R^2) / (Fb^2 x Vb)] - 1.463xR
Fb - is the desired tuning frequency of your enclosure in Hertz.
Lv - is the length of your port in inches.
R - is the inside radius of your vent tube.
Vb - is the internal volume of your enclosure in cubic inches. To convert cubic feet to cubic inches, multiply by 1728.
Transmission line length:
First, find the length of the speaker’s Fs by dividing 1120fps (speed of sound) by the Fs of the speaker. (1120fps / 40Hz = 28’)
Line length = Fs wavelength / X
X= 4 (25% of wavelength gives you a 90degree phase shift)
X= 2 (50% of wavelength gives you a 180degree phase shift)
X= 1.333 (75% of wavelength gives you a 270degree phase shift)
Temperature, elevation, air pressure, and humidity all effect the speed of sound. If you wanted to get technical, plug these factors into winisd, and it will calculate sound velocity for you. Temperature is the biggest factor in sound speed.
Comments...??
Victor..
Replies (6)
uochronos on 02/5/2005 14:33:58
i currently have a Elemental designs Kx series sub in a 1 cubic foot sealed box... before i had it in a 1cube sealed bux that was to the golden rule,... well because of the shape i had to face the middle of the truck and it sounded ok now i have a box thats the same exact size just a better shape and it is facing up and this one actualy sounds better just because i was able to move it to a proper location....
i would think if your a huge SQ freak into compitition the golden rule may help a tiny bit.. but in general builds i dont see alot of use because usualy your buidling a custom box to fit the car as much as the sub... and in alot of vehicles the golden rule shape just wotn fit properly... actauly loseing SQ.
Chronos
Victor on 02/5/2005 15:02:34
agreed...
But this is what the basics say. Just wanted to share that bit of info.
I also agree that shape, size and orientation of every enclosure is influenced by many many factors..
cant lay down a rule in this area. but as always , be it Math or Physics there are some postulates written down, this seems to be just one of them.
Am just trying to share some extra bit of info, and text book notes..
Victor..
cplkittle on 02/7/2005 00:47:35
Those equations took me almost 2 months to research, and in the last year I have found that all are very accurate. The only thing is the Golden ratio is for enclosures with no polyfill or other sound deadening material.
Victor on 02/7/2005 13:41:03
Hey kittle. .. do u still have the notes on the derivation of the Golden ration, I have researched a lot on it too.. it wud be good to share something here..
Victor..
cplkittle on 02/7/2005 20:01:47
This is the only paragraph I kept on it...
The "Golden Ratio" should be used whenever possible unless space is restricting which is a normal occurrence when dealing with an automobile. This ratio is 1 x .7937 x 1.2599. For subwoofer cabinets, dimensions with this ratio will sound less boomy and have less panel vibration. To figure the dimensions that you need for a particular volume, without trial and error, you must have a calculator with a "cube root" function. Find the cube root for the volume that you want.
You may be able to find more with a search for "acoustic suspension". I can't remember what all I looked up to find this. I also have noted some of the pages in which I found and or copied material in my "overview of enclosure designs" DIY article.
Also, I just ordered two books from amazon on acoustics.
On the Sensations of Tone by Hermann Helmholtz
and Master Handbook of Acoustics by F. Alton Everest
I will post a review and/or recommendation if I find these useful. Both cost me under $40 USD. I know the Master Handbook of Acoustics is geared toward room acoustics discussing resonance, refraction, reverberation, and diffusion; but I believe with a thorough understanding of the basics on a large scale I may be able to draw a parallel to vehicle acoustics.
Victor on 02/8/2005 01:21:55
nice going ... i guess we can be very helpful to each other.. cause i am doing a lot of research on sound, propogation of sound, acoustics, sound illussion etc..
lemme know if i can share something with u too..
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