Bp102's what to do?

[CuttaBoi]

hey all I've got 4 Eminence bp102's (4ohm) wanting some use...

Original plan was to build for of bfms T39's 16 or 20" wide not too sure whether to build them now though.

Can anyone lend any suggestions on what to build to get the most out of them? Ideally a design a bit simpler than the T39.

Thanks in advance

[jbell]

sorry, I don't have any good suggestions for you. I've built that cab with that driver. (still have at least 1 of them brand new in box...)

Best thought I have for you if you are a good cabinet builder... Make the most beautiful 4x10 bass cab you can, tweed on the front and sell it to a die hard 'vintage tone' bass player.... You'd have a 4ohm cabinet, which would be desirable.

then buy 3015lf's and make TH's.

If you decide to build the T39, go slim, very slim. always run 4, always v-plate and always wall load. (and have good eq to flatten the response out.)

best of luck to you.

[CuttaBoi]

Thanks for the input Jbell, appreciate it. Do you think they could possibly be suitable for a home subwoofer/tapped horn design?

[bjorno]

Originally Posted by CuttaBoi

..Do you think they could possibly be suitable for a home subwoofer..

Of course:

b

[CuttaBoi]

hi Bjorno, would you be able to help/advise on how to turn that in to a build plan?

[bjorno]

Originally Posted by CuttaBoi

hi Bjorno, would you be able to help/advise on how to turn that in to a build plan?

Hi,

Do you want a single folded a multi-folded design? In case of the former I suggest you try to come up with your own calculations and present the result here at DIYaudio.

At first I would check if the ~ internal footprint is reasonable and small.

That is if the ~areas S1+S5 are OK. for a box design of (1210+669)=1879 cm^2 = ~ (43.4x 43.4) cm^2= (17.07x 17.04) sq inch and if the driver frame width would fit within the box width.

The BP 102 frame width is 10.08”= 25.61 cm = rounded off to occupying at least an internal box width of ~26 cm : indeed a fairly squarish box can be designed.

The ~height of the box would then be: total internal length/2 = 280/2= 140cm(~55.1”).

I prefer a sub box where the driver in box can be placed as close to wall/floor as possible to pick up boundary gain but avoiding FR dips at lower frequencies.

-3dB 344/8x(Driver distance to floor/Walls) dips should IME not be allowed to occur for frequencies below~100Hz for a quality sub utilizing at least a 2xPI boundary gain.

The volume occupied for a slanted internal divider + cross braces(2 off) must too be taken into consideration before the true total box volume= WxDxH can be calculated.

So what thickness and type of wood do you want to use? Rec. at least 15mm(thick enough if Birch Ply) to (~22mm).

b

[CuttaBoi]

Hi mate, in all honesty I don't understand alot of what you've just said (especially the calculations) but interested in where your going with this


With regards to wood, I can get hold of a few sheets 18mm (7 equal layer) ply for free

If we was to increase the frequency responce to 30-35hz would it be possible to increase the maximum input?

Thanks for taking the time to get back to me

[jbell]

Originally Posted by CuttaBoi

If we was to increase the frequency responce to 30-35hz would it be possible to increase the maximum input?

In general for a tapped horn:
The xmax limit for a TH is reached IN the passband, not below. As you tune lower, the xmax peak goes lower in freq, and higher in displacement -- meaning you can accept less power before reaching xmax limit.

As an example, my stadium horn (bigger, lower) can only accept 50v before reaching xmax, while the ss15 (smaller, higher) can accept 63volts before reaching xmax using the exact same driver.

A design where power limit and physical limit are reached at about the same time maximizes the output that particular driver can produce.

[bjorno]

Originally Posted by CuttaBoi

..If we was to increase the frequency responce to 30-35hz would it be possible to increase the maximum input?..

Hi,
Update: ~31.5W/4Ohm to 47W/4Ohm = ~+5.4dB; f-3dB from ~23Hz ==> ~32Hz and ~248L ==> ~202L.

b