Speaker volume (space occupied, not loudness) in cab question

[Clammy]

In the typical spec sheet for a given driver, they list "Recommended Enclosure Volume" for both vented and sealed cabs. Does this spec include the volume of the actual driver, or does that need to be subtracted from the cab volume?

For example: Say we have a sealed 4x12 cab that has an internal volume of 7 cu ft empty, and we want to put 4 speakers that are recommended for 1.3 cu ft each (for a total of 5.2 cu ft), would that cab be too large for those speakers? If the speaker volumes aren't included, how do you determine the amount of space they occupy?

Thanks.

Cheers!

[billfitzmaurice]

Originally Posted by Clammy

Does this spec include the volume of the actual driver,

No. You must add the volume taken up by the driver and ducts, if a ported cab.

[Clammy]

Originally Posted by billfitzmaurice

No. You must add the volume taken up by the driver and ducts, if a ported cab.

Thanks!

Just so I'm clear, if each of the speakers in the above hypothetical example take up .5 cu ft, I would deduct 2 cu ft from the cab volume of 7 cu ft, giving me 5 cu ft - 1.25 cu ft/driver. Correct? Or do I have it backwards?

Is there an easy way to determine the volume of the individual drivers? Is it somewhere in the spec, that I'm missing?

Cheers!

[will33]

Originally Posted by Clammy

Thanks!

Just so I'm clear, if each of the speakers in the above hypothetical example take up .5 cu ft, I would deduct 2 cu ft from the cab volume of 7 cu ft, giving me 5 cu ft - 1.25 cu ft/driver. Correct? Or do I have it backwards?

Is there an easy way to determine the volume of the individual drivers? Is it somewhere in the spec, that I'm missing?

Cheers!

That's correct. Anything in the cab must be subtracted from the gross to end up with the net air space the driver has to work in. Ports, bracing, everything although being within a few cubic inches in a large cab is fine.

For the volume of the driver itself, I take a measurement across the back of the magnet and the diameter of the basket where it comes through the inside of the baffle and average the two. Use that and the depth between those 2 points to figure the volume of a cylinder. (Pi*r squared*depth).

If you want, search the term "conical frustum". It's a geometric shape that closely resembles a speaker and may be slightly more accurate but being within a few cubic inches in a few cubic foot box is close enough.

[Passinwind]

Originally Posted by will33

For the volume of the driver itself, I take a measurement across the back of the magnet and the diameter of the basket where it comes through the inside of the baffle and average the two. Use that and the depth between those 2 points to figure the volume of a cylinder. (Pi*r squared*depth).

WinISD Pro has a handy calculator for that built in.

[will33]

Found the conical frustum calculator here

Conical Frustum Calculator

I just think it sounds cool

[will33]

Originally Posted by Passinwind

WinISD Pro has a handy calculator for that built in.

Wierd, I never noticed that. Is there an update or something or do I just need to dig deeper and take full advantage of my program?

[Clammy]

AWESOME!! Thanks for all the help everyone!

Cheers!

[Passinwind]

Originally Posted by will33

Weird, I never noticed that. Is there an update or something or do I just need to dig deeper and take full advantage of my program?

Pretty sure it's always been there, in the Utilities/Database Editing part. I've only used it a couple of times, but it seemed to jibe decently with published figures I had on hand for those particular drivers.

[billfitzmaurice]

Originally Posted by Passinwind

WinISD Pro has a handy calculator for that built in.

True, but that's a lot of work. The rule of thumb for designers is to oversize the box by 10% to account for the driver and other odd bits.