Calculating For Cabinet Enclosure Space

[speedemon]

Hi All

I'm looking to see if anyone knows the true answer to this subject. Several weeks ago, a few of us got together at a friend's home to listen to his system. The subject that was brought up was about an enclosure having two drivers in it without a partition. Let say for an example, we are using two 12" woofers, and the spec calls for a recommended of 4 cubic foot for each of the woofers. So we have a cabinet with an internal size of 8 cubic foot total space in the enclosure and we didn’t a partition off using baffle to separate the enclosure space. So now both woofers are sharing the total of the 8 cubic foot enclosure. Our question is now since there is no partition to separate them does that mean that each woofer is considering using 8 cubic foot of enclosure space? Since there are no partition to separate them down to 4 cubic foot and it was left open, is that mean we have setup the woofer as using an 8 cubic foot enclosure instead of 4 cubic foot? If you guys know what the true answer would be then let me know. We got quite a discussion on this subject.

Thanks

[speedemon]

Hey, does anyone have any comments on this or what you think? As the question goes, without the partition to separate the enclosure is the each driver basically considered using the full 8 cubic foot enclosure? Anyone have facts this? I posted this figuring you guru's can answer this one. Let me know your thoughts on this.

[sreten]

Hi,

What your saying doesn't make any sense.
If it did you would not use 8 cuft in the first place.
Partioned or not, it doesn't make any difference.

/sreten.

[speedemon]

I guess I'll try to put it in plain English! Again, the woofer's spec recommended for 4 cubic foot of volume, there are two woofers that are going to be used in the same cabinet. The cabinet has an internal volume of 8 cubic foot (non-partitioned) so our question is since it is non-partitioned (meaning no divider) and using two woofers in the same cabinet are woofers itself going to be working off of a 8 cubic foot volume or are they consider working on a 4 cubic foot, is that more clear for you, does that make sense now?

[Eton]

Divider or not, each is using 4 Cubic ft.

[speedemon]

Of course each is using 4 cubic foot, it using a total of 8 cubic foot to be exact. There is no restriction at 4 cubic foot correct? So it’s using more since it is being shared in an 8 cubic foot space undivided! It not limiting each driver to only 4 cubic foot do you understand? So what we are saying since it in the same enclosure share that space, would it have a different effect if there was a partition splitting them apart is we are saying.

[AR2]

I will try to use just simple logic.

Yes each speaker sees 8 cubic feet since there is no divider between. But since there are two speakers instead of one the internal pressure developed by two speakers is doubled. With doubled internal pressure, volume requirement is doubled as well to have the same effect as in the scenario of 4 cubic feet. In another word there is no gain in dropping the divider. It will be completely different story if there is doubled volume with only one speaker.
If we disregard pressure, than answer to your question is yes - each speaker sees 8 cubic feet, and than what? Than internal pressure comes in light.
Just my guess.
AR2

[MJL21193]

Originally posted by speedemon
Of course each is using 4 cubic foot, it using a total of 8 cubic foot to be exact. There is no restriction at 4 cubic foot correct? So it’s using more since it is being shared in an 8 cubic foot space undivided! It not limiting each driver to only 4 cubic foot do you understand? So what we are saying since it in the same enclosure share that space, would it have a different effect if there was a partition splitting them apart is we are saying.

This is actually a good question. The fact is box volume is determined by a lot of variables. T/S specs first, number of drive units, how they are wired can even makes a difference.
Generally speaking: double the drivers, double the volume. Isobarik is the exception. With isobarik, the volume is cut in half for two drivers.

[Svante]

There is no* difference in having two drivers in one 226 liter box putting the drivers in two boxes of 113 liter. One way of understanding this is to consider a perfectly symmetrical layout of the box. Due to symmetry, there will be no airflow across the symmetry line. This means that adding a wall at the symmetry line will not affect the airflow.

*Adding the wall between the two halves may act as bracing of the box making it more stable, but I don't think this was the question here. Also, the question is different if the speakers are driven by different signals, but I don't think that is the case ere either.

[speedemon]

Originally posted by MJL21193



This is actually a good question. The fact is box volume is determined by a lot of variables. T/S specs first, number of drive units, how they are wired can even makes a difference.
Generally speaking: double the drivers, double the volume. Isobarik is the exception. With isobarik, the volume is cut in half for two drivers.

This is what we were looking at. The woofers are both running in phase. The wiring is wired in parallel. Since they are pushing in and out together which they are working together, that itself is not creating pressures against each other which that means their using more than their limited space. For an example you put two persons into a 10X20 room, technically their only allowed to run around in a 10X10 space, but without a divider or partition their able to both use the full 10X20 space isn’t that correct? Since there is a no divider or partition of some sort how you are going to stop this from crossing the line of each others. So what we’re saying here is would the drivers be more effective just in it own 4 cubic foot space or does it hurt it being in an enclosure with another driver in an open area? This is what we have been trying to figure out. Is it less effective marrying up together with another driver sharing the same space or would it do better in its own space?