BIB Calculations

[G]

The panels that I've seen were either 5/8 or 3/4 inch. Available in pine or aspen. Solid wood - even pine - is quite a bit stiffer than plywood and a LOT stiffer than MDF. Aspen is stiffer than pine and would be my choice. The glued up panels will be more stable than a single board, certainly stable enough for a BIB I would think.

Look for a panel that is glued up from full length pieces without any (or many) short pieces butted together.

-- Dave

"Stiffness" is not what you are looking for. Density is. There is a reason MDF and BB are used in so many cabinets.

 

[Dave Cigna]

"Stiffness" is not what you are looking for. Density is. There is a reason MDF and BB are used in so many cabinets.

I can see the need for mass, but a BIB made from pine will weigh plenty. Stiff panels are also important.

As for MDF, I have no use for it. I don't care how heavy it is.

-- Dave

 

[GM]

Greets!

According to the BIB site the 207E is 174"/2 = 87": http://www.zillaspeak.com/bib-fostex.asp

'Sm' isn't much, so 87" plus wood thickness isn't too tall.

You may need a little series resistance, so I recommend wiring a cheap pot in series and experiment just to be sure and swap in a fixed value if need be.

GM

 

[Scottmoose]

Thanks Greg.

Kim: trick is: don't worry about it. These big pipes are very flexible. Length is simply 1/2 wavelength of the target Fc. We ofte tune to the driver Fs, but that's more a choice thing. The Coral drivers will likely show a bit of variation, so unless you get your own units measured, the 'perfect' length if you wanted to tune to Fs will remain unknown. I wouldn't worry about it to be honest. This will get you near enough.

 

[GM]

Greets!

You're welcome!

Yeah, the whole concept of pipe horns is to make it big enough for the driver to 'feel' like it's not doing any real 'work'. Anyway..........

"Fres 57Hz" is self explanatory, ergo "min. resonance frequency = 40hz" is also once you understand that it's the product of ~0.707*Fs, or 1/2 octave below Fs, implying that tuning it any lower in a sealed, BR or any of its BLH variants isn't a good idea.

"Qo = 0.5 at 40hz" simply means that the driver is critically damped at 40 Hz, or in today's post T/S 'world', Qts = ~0.5 (only '~' since the Qo calc is more basic):

Hopefully, I didn't 'confuse' your confusion.

GM