question about speaker box design

[jaygeorge1979]

well i am FINALLY learning how to use winisd and the t/s parameters in general and now i have figured out how to decide how much internal volume is needed to get a speaker to perform a certain way...

NOW my question has to deal with the actual box construction...say we want an internal volume of .1 cubic feet for a small sub application...if we are using half inch MDF for the project, we would have to subtract half an inch off of each of the outer dimensions to calculate internal volume, right?

also, since the sub frame/magnet displace air once installed, shouldnt we keep that in consideration and add its equivalent volume to the overall box volume?

finally, what about a plate amp? simillar to the sub question, having a plate amp takes up space that was intended to be air for the sub...should we add this volume to the total internal volume?

so what i am asking is, should we use *calculated internal volume+estimated volume of sub+calculated volume of plate amp* = actual internal volume needed in this project?

[maxwedge]

NOW my question has to deal with the actual box construction...say we want an internal volume of .1 cubic feet for a small sub application...if we are using half inch MDF for the project, we would have to subtract half an inch off of each of the outer dimensions to calculate internal volume, right?

You got it. What ever your inside dimensions are determine your volume. WxHxD=Volume

also, since the sub frame/magnet displace air once installed, shouldnt we keep that in consideration and add its equivalent volume to the overall box volume?
finally, what about a plate amp? simillar to the sub question, having a plate amp takes up space that was intended to be air for the sub...should we add this volume to the total internal volume?

No, you subtract their volumes.

so what i am asking is, should we use *calculated internal volume+estimated volume of sub+calculated volume of plate amp* = actual internal volume needed in this project?

Nope. Change your +'s to -'s and you'll be ok.

[69stingray]

I think you are both right....

If the required internal volume is 0.1 ft3, then you add the volume of the driver and the volume of the port. Lets say you est. the volume of the driver to be 0.05 ft3 and the volume of the port to be 0.01 ft3. You will want to determine what WxHxL dimensions get you the total volume.

Total Volume = Req. Volume + Driver Volume + Port Volume + Brace Volume.

That way, your NET volume is what yuo want.

[maxwedge]

For the net volume of a box you subtract the volume of anything that takes space inside the box. Including the driver, bracing and the port as well. Whatever you put in there can't add to volume....it subtracts.

[jaygeorge1979]

whoa...i am supposed to add the port volume too?

i didnt know that

can i get a second opinion

[69stingray]

I do, I have an Excel spreadhseet. It has the formula for the required port diameter and length and automatically determine's it's volume. I also add the major dimensions of the driver and it calculators the driver volume. It adds all the volumes together (include braces) to get the required internal dimensions, then adds 0.75" (MDF) to get external dimensionals. I love Excel.

[maxwedge]

69stingray and I are saying 2 diff things. I'm stating a basic fact about speaker box volume. He's saying how you come up with a specific volume needed for the driver to opperate at the frequency wanted.

Example. The driver needs 2 cu ft. You know your bracing, port and back side vol of the driver equals 1 cu ft. To get your 2 cu ft for the driver you add the 1 cu ft to your design. So you build a 3 cu ft box that has a net vol of 2 cu ft.

[jaygeorge1979]

ok ok, now i do understand...i am glad somebody pointed out the port thing before i made a mistake...

now about that excel sheet thingymabob...what say you email it to me