BIB dimensions

[GM]

Hmm, Vb = 624.692 L since you didn’t convert Vas to ~2.92808 ft^3, so 624.692*0.3531467 = ~22.06079 ft^3, making Sm and its related dims wrong.

Away, easiest to use Vas in ft^3, then the other dims will work out in inches. That, or use Vas in liters and change the SoS and Sm calculation values to cm if you want a metric design.

GM

[opa1]

Ok, I did find the 2.92808ft^3. Somehow I messed up the rest of the equation. ( in ft^3)(12^3(inches in ft^3))/67.7 If I take 2.90808ft^3 and convert to in I get 5059.7222. What is inches in ft^3? Also the lenght formula seems off. Is 13526.5 a constant#. The lenght /2 seems short at 67.7.

[GM]

How come you didn’t just use the linked BIB spreadsheet?

Ft^3 = 12”^3 = 12”*12”*12” = 1728”^3

Sl = 22.06469 ft^3*1728”^3 = 38127.784”^3/67.7” = 563.187”^2

The speed of sound [SoS] should be a constant for typical speaker design, but for some reason different programs, technical documents will have varying values. 13526.5”_sec/12” = ~1127 ft_sec or ~ in the middle between the two most extremes. FWIW, until I got on-line, all the docs I’d seen listed 1130 ft_sec, which is ~ what I’ve measured using mil spec calibrated equipment during my working career.

Regardless, the minor differences it makes in typical speaker designs are inaudible and don’t take into account any internal heating unless you take measurements and adjust as required such as for some commercial and prosound apps.

The acoustical path-length is what matters and is a ~1/2 WL of whatever value is put in the ‘Fs’ field, which means it’s tuned to a ¼ WL of Fs = Fs*0.707 or ~35.31 Hz.

Low enough for you? If not, input a lower Fs with the understanding it will put the driver higher up off the floor.

Want to make it smaller? Reduce Vas or Qts as required. Of course less is always less in acoustics, so there will be less of an air cushion for the driver to work against, ergo less power handling down low with a higher roll off if the room’s acoustics don’t help enough.

GM

[opa1]

Ok, one more time.
L=134.780
H=67.390
Vb=22.004
Sm=564.212
D=28.247
W=19.974
Zd=29.247
A B C =14.124
So about 67.5x28.5x20
I get it now. Thats a big cab. Changing Fs changes lenght. Qts or Vas, changes D,W and Zd

[opa1]

Zd changes with Fs, lenght. I didnt know you could plug in the specs on the bib cal. chart. Just click on the blank space and enter info. It's alot easier than doing all the cals.
I did learn more doing it that way thought.lol
Sorry for giving you a headache GM.

[GM]

No problemo, it's not like no one's ever had to 'hold my hand' on a project. What goes around, comes around if you live long enough.

Yeah, it's ~2 ft^3 bigger than mine, though they have a bit bigger footprint at 30" x 24".

So, you going to build them or downscale them somewhat?

GM

[opa1]

They would get used in a 9x12 room. They would be corners. Being that its a small room I'm not sure how well they would work. Might have to stuff the whole lenght. lol. I changed the Vas from 2.92 to 2.0. It changed the dims to 67.5 x 23.5 x 16.5. Whats going to happen?

[GM]

Hmm, I'm in a ~12 x 13 ft room and I'm thinking that corner loading these might be a bit much in mine, so going a little taller using T.C.'s 138" path-length and reducing Sl to ~398.9" might be a better fit.

Your call of course!

GM

[opa1]

Footprint would be better for me. 70h x 23.75d x 16.75w. Yes, I need to build something. I've got sims and dims on three MLTL's and the BIB. Might as well build the BIB. It's going to take about the same amount of wood anyway. I've got the Betsy K's.

[opa1]

Are those sims for the 138" line lenght? Whats the big drop at 100hz and all the spikes in the upper range?