MBM DIY Design Concepts...

RuSsMaN

"...a very light cone, low inductance voice coil, and a strong magnet yields extremely quick response with high efficiency."

Isn't this pretty much a requirement for any mid bass or bass driver?

I don't get this, then again, I don't get Super Tweeters or tactile transducers either.

Good luck on the project - Why are you limiting yourself to 12 inch drivers? Why not some 8's? 15's?

Cheers,
Russ

Systems

RuSsMaN wrote: »

I don't get this, then again, I don't get Super Tweeters or tactile transducers either.

I understand your scepticism and it does seem uneccessary but I explain in post #9 why I think it will be a benifit in my setup by adding the missing45-80hz info.

Good luck on the project

Thanks

Why are you limiting yourself to 12 inch drivers? Why not some 8's? 15's?

I chose the 12" because I have one on hand and the enclosure can be kept very compact.Depending on their T/S parameters some 15" drivers could be used but they would likely require a larger enclosure.Quality smaller drivers used in multiples is a viable option.

beardog03

That last Dayton that Early gave a link to , looked pretty good

Early B.

How do I convert to c.f. a box with the following dimensions:

20" x 18" x 14"

Thanks.

dudeinaroom

20*18*17=6120sq.in.
6120/1728(1cu.ft.)=3.5416666666666666666666666666667cu.ft.

if you ever for get how many inches are in a cubic foot all you have to do is 12*12*12=1728

MillerLiteScott

Using a calculator I came up with 2.916 cubic feet.

Systems

As dude posted divide by 1728,and if want to know the metric(litres) multiply your cu ft x 28.317.

Early B.

Cool! Thanks for the math lesson, fellas.

Systems

Progress on this has been slow but I did get some of the MDF panels cut.The enclosure will be a WAF acceptable 14"x14" cube.The actual internal volume is a bit less than a cubic ft which sets the -3 point around about 52 hz with my Infinity 1242w woofer.The Qtc is a tad high at .9 so this will add a slight peak in the response before it rolls off.This may not be a bad thing and should add a bit of punch around 50hz.

I use my DVD players Dolby Digital and DTS decoders for surround sound therefore the my LFE output is taken directly from it.However the players internal sub crossover is set much too high(100hz) and with a shallow 12db slope so it is not well suited for the purpose. I plan to build an 80hz low pass filter with a 12db slope but if I find that the mib bass units position is detectable I may lower the crossover frequency or increase the slope to 24 db per octave.

The crossover between the mid bass and the regular subs should be unproblematic as the midbass driver because it is in a sealed box will naturally rolloff at a rate of 12db per octave below its tuning of 52hz.The main subs crossover is set so that they will roll off at 12db per octave above about 45 hz.To aid in the blending of the two I will incorporate a variable phase control with the mid bass units crossover.

I also have to aquire a single channel of amplification with 150watts or so.