Minimum enclosure volume?

[revans]

I'm making a speaker with two Tang Band W4-1320SF 4" Bamboo Cone drivers (http://cgi.ebay.com/Tang-Band-W4-132...QQcmdZViewItem) and was wondering what the minimum enclosure volume would be that still maintained reasonable sound quality? Pretty much I want to make the speaker as small as possible. Sorry if this is a little vague, but I've never built speakers before and have a very limited understanding of this stuff. Please ask me to elaborate if necessary.

[chops]

They have the recommended cabinet right there on the eBay page. If you want it to sound half-way decent, it might be best to stick with what they provide as a first project.

[revans]

Ok I guess I should have mentioned that this is for a portable boombox type thing (with an emphasis on the portable). I don't really want to have masses of empty space making it bigger than it needs to be...unless it's really necessary...

[Cloth Ears]

Originally posted by revans
Ok I guess I should have mentioned that this is for a portable boombox type thing (with an emphasis on the portable). I don't really want to have masses of empty space making it bigger than it needs to be...unless it's really necessary...

Those are reasonable drivers to play with, but no matter what you do, you won't get much sound below about 80Hz. And, if you try to reduce the size of the box, you won't get that either.

I can't see the drawings on the eBay sight from work, but you are best to go with a 4 litre box for these if you're going to make a vented pair of boxes. The internal dimensions would be 4 inches wide (10cm) 6 1/6 inches deep (15.5cm) and 10 inches high (25.4cm). Port should be (if it's round) 1.5 inches diameter (3.8cm) and 4 inches long (10cm). If it's going to be a slot port (ie. the full width of the speaker - 10cm) then it should be .45 inches high (or 1.15cm).

If you try to make it smaller, then the driver is unable to work sufficiently well against the volume of air in the box to be able to make sound in the lower resgisters. And is unable to excite the resonater (the port) to be able to get that to work either.

To get something to work in a smaller volume, you'd need to look at something with a lower Qts or Vas. Or just live with the larger, better sounding, speakers.

What were you intending to drive them with? These could do with some good amplification. They might be better suited to a home (or PC) environment than as a 'boom box'.

[revans]

I was going to use an Amp6-Basic to drive them. Apparently that's the weapon of choice in these areas...

[Cloth Ears]

Originally posted by revans
I was going to use an Amp6-Basic to drive them. Apparently that's the weapon of choice in these areas...

Should be a good match. The speakers on the 41hz website with the amp6basic board are about the same size I'm suggesting (mine would be a little thinner, and a bit deeper, and maybe a little less tall - not sure on the height).

[revans]

So you reckon in the name of sound quality it wouldn't be wise for the size of each speaker's enclosure to be smaller than what you specified?

[revans]

Oh I was just thinking, if I was to put both the Tang Bands together in one enclosure, would the volume of the enclosure then need to be double that of a single speaker enclosure? Or is there some reason that this wouldn't be the case?

E.g. The volume of a 10x15.5x25.4cm enclosure (Cloth Ears recommendation) is 3937 cubic cm, so with two drivers volume would be ~8000 cubic cm

[Cloth Ears]

Your thinking is exactly right - double the drivers, double the volume. Except that you would get some pretty interesting effects if you were trying to use them as a stereo.

You could build an 8 litre enclosure, but with a board right down the middle - you wouldn't get much stereo effect, but your drivers wouldn't interract with each other. If you used 12mm plywood, you could make a box that is 53.2cm long (including the walls at each end and one in the middle), 12.4cm high (including the walls again) and 19cm deep (yes, with the walls). If you mounted the drivers at each end of the front face, you'd have about a 40 distance between the centres - and you'd get stereo for about 2 metres in front of the box (maybe more).

But, if you did it this way, you wouldn't be able to separate them if you wanted to. I'd suggest building 2 boxes and looing at a good way of hooking them together when you wanted to move them around.

[revans]

Yeah, I think I'll go with trying to use two 10x15.5x25.4cm boxes. However, could I adjust this so that the volume is the same, though with changed dimensions?

I've managed to pack the electronics for my boombox into ~24x14x14cm box so I just need to arrange that with the speaker boxes in one package...