why can you use less SQ inches of port per driver in a unibox

[vehementSPL 10+ year member]

I am curious why for example... In winISD

I take 2 12's in 5 cubes ported and 100 inches of port it gives me X amount of port velocity . Now explain this. If I do 8 12's in a unichamber that is 20 cubes ported with 400 inches of port. So everything exactly 4 times so should hold the same port velocity.... The big unichamber box has a hair less than half of the port velocity . Now I know WinISD won't be 100 percent accurate on the port velocity BUT it has to be following some theory that I am not aware of (never really got into uniboxes)to show that it doesn't match the same velocity but exact same multiples of everything else. I even tried 4 100 inch ports in the unichamber box and still shows less than half as opposed to the smaller box with 2 12's. Any input.

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[vehementSPL 10+ year member]

PS Seems like back in the day I heard there was odd things on using multiple woofers in one box.

 

[vehementSPL 10+ year member]

ttt

 

[BrianChia 10+ year member]

Supplied power? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[vehementSPL 10+ year member]

Considered that. But in theory 4 times the speakers. and airspace equals 4 times the output even with same power

 

[BrianChia 10+ year member]

Not true. Each doubling of radiating area will theoretically add 3 db if volume per driver remains the same, and the total supplied power is the same. Now if you double power, then you see a theoretical maximum 6 db increase, which is roughly a doubling of output.

 

[mjf 10+ year member]

because its sharing airspace between each driver, which effectively reduces the amount of airspace needed overall.

example

12" sub needs 2.5 cubes

2 12" subs need 3.5-4 cubes

3 12" subs need 4.5-6 cubes

cut the box with 8 12s down to about 15/16 cubes, should work well.

also in terms of port area, 12-16 in^2 per cubic foot is a good rule of thumb.

 

[BrianChia 10+ year member]

because its sharing airspace between each driver, which effectively reduces the amount of airspace needed overall.
example

12" sub needs 2.5 cubes

2 12" subs need 3.5-4 cubes

3 12" subs need 4.5-6 cubes

cut the box with 8 12s down to about 15/16 cubes, should work well.

Not true at all.

 

[mjf 10+ year member]

Not true at all.

its a decent rule of thumb to work by, and has worked in almost every enclosure ive built or designed.

 

[BrianChia 10+ year member]

Multiple drivers does not reduce amount of airspace needed per driver. Required volume per driver is not determined by size of driver or number of drivers.

 

[vehementSPL 10+ year member]

Not true. Each doubling of radiating area will theoretically add 3 db if volume per driver remains the same, and the total supplied power is the same. Now if you double power, then you see a theoretical maximum 6 db increase, which is roughly a doubling of output.

That is what I was saying

 

[vehementSPL 10+ year member]

anybody?

 

[mjf 10+ year member]

Multiple drivers does not reduce amount of airspace needed per driver. Required volume per driver is not determined by size of driver or number of drivers.

i beg to differ BY FAR.