displacement volume for 15inch

[holger honda]

hello.
Im building a sub for a b&c 15 pzb 40 driver.
got it for little at ebay,and here I go again.......
Now I cant find the displacement volume of the driver online,Im asking if you have any idea of an aproximation of how much (in liters) a generic sturdy pro driver might displace?
At least this would get me closer than no figure at all.
Any input is moust apriciated.
thanks a bunch!

[Bill Fitzpatrick]

It's easy enough to calculate after taking a few measurements.

[kelticwizard]

Displacement = Cone Area X Excursion

Cone Area of one 15" Peerless SLS PA woofer is is 897 sq cm, or 900 is close enough.

Displacement of the B&C 15 pzb 40 driver is given at this link:
http://www.usspeaker.com/15.htm#B&C

It is 8 mm, which is twice the excursion of other listed PA speakers, both B&C and other brands. So we know this is the correct figure, since the normal excursion of a 15" PA speaker is indeed about 4 or 5 mm. The website does make note that this is indeed a very long excursion. We can also have confidence that this is the correct method of measuring excursion, which is (+ or -), not front-to-back, since the other woofers listed on the website correspond to the manufacturer's listed (+ or -) excursion figures.

8 mm = 0.8 centimeters.

900 square centimeters X 0.8 cm = 720 cubic centimeters = 0.72 liters.

There's your answer.

Incidentally, this number is for Linear volume, that is, the amount of air that will be moved with comparatively low distortion. PA speakers are noted for being able to travel two or three times as far as the linear Xmax without damage-people drive them that far all the time. Of course, once you leave the linear area, your distortion will go up, but you won't be damaging the speaker. The limit you can drive a speaker is called Xmech, and in PA speakers it is almost always twice, and sometimes three times, the linear Xmax. so that extra excursion increases the volume of air that can be moved two or three times this figure, although with higher excursion.

So the figure I gave you-0.72 liters-is the conservative figure, the one normally used. The unit will move two or three times that without damage, but with high distortion.