Hi-Vi B3N MTM Towers and MMTMM Center

[jsalbre]

I've decided for my project that I want to build 4 MTM towers, plus an MMTMM center channel, using the Hi-Vi B3N and an as yet undecided tweeter.

Towers:
Using the online ISD at http://www.linearteam.dk/default.aspx?pageid=newdriver with the specs for the B3N from http://www.partsexpress.com/pdf/297-428z.txt (vas: 0.62 l, Qts: 0.9, Fs: 114.5 Hz) I get a required vented volume of 0.6183 cu. ft. for 2 drivers.

A tower made of .75" at 5" x 7.5" x48" gives an interior volume of 0.646 cu. ft. Am I correct in guessing that the extra volume (0.026 cu. ft.) could be successfully filled up by the drivers, crossover and bracing, or is that too much or too little?

Center:

I want to base this off of the Cynosure (http://www.partsexpress.com/projects...oject=Cynosure) but using the B3N (and same un-chosen tweeter) so it will match the towers.

Using the same specs as above but for 6 drivers I get a required vented volume of 1.8555 cu. ft, while the original design plans using the Tang Band W3-926S state a required vented volume of 0.5 cu. ft. I realize these are different drivers with different specs, but that just doesn't seem right to me. A box with the original height and width (4" x 24") made of 1/2" would have to be 47.5" deep. Am I missing something?

If someone with more experience would run over my numbers for the tower and center I'd be very appreciative.

Also any tweeter suggestions would help too!

Thanks a million!

[jsalbre]

Slight correction: The width for the towers was supposed to read 5.5", not 5".

[sreten]

Hi,

Venting any driver with Qts = 0.9 is pointless. Vas of 3" drivers is
around a litre, and around 2L to 3L sealed and well stuffed each
is what is required. 2L is minimum, > 3L fairly pointless.

/sreten.

[jsalbre]

Originally posted by sreten
Hi,

Venting any driver with Qts = 0.9 is pointless. Vas of 3" drivers is
around a litre, and around 2L to 3L sealed and well stuffed each
is what is required. 2L is minimum, > 3L fairly pointless.

/sreten.

So if I understand you correctly you're saying 2-3L per driver for a sealed box, so that would be 4-6L for the 2 driver towers and 12-18L for the 6 driver center, correct?

Would venting them negatively affect the sound quality or is it just the extra required size that makes it pointless?

I'm still thinking something is wrong with my numbers, as the required size for those boxes is still turning out huge.

[augerpro]

That's because these programs are fairly dumb. And once Qts gets above .707 the resulting "optimum" box gets unreasonable. You have to exercise some good judgement. Read the June 12 posting here: http://zaphaudio.com/blog.html

[jsalbre]

Originally posted by augerpro
That's because these programs are fairly dumb. And once Qts gets above .707 the resulting "optimum" box gets unreasonable. You have to exercise some good judgement. Read the June 12 posting here: http://zaphaudio.com/blog.html

Whew, thanks Brandon. I've been beating my head against the wall trying to figure out what I was doing wrong.

So what kind of numbers would you say I should be considering when building sealed or vented enclosures with the B3N?

[bjorno]

jsalbre,

FYI:
Using the given driver data and suggested dimensions in a ported box, i.e. aperiodic damped tower speaker. See pictures 1(3) to 3(3).

b

1(3)

[bjorno]

2(3)

[bjorno]

3(3)

[jsalbre]

Wow, thanks bjorno!

I haven't the foggiest if those are good or bad results though, would you mind translating?