Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

[Godzilla]

Can't watch on my iPad

[Circlomanen]

Yes, this is my B&C 10PS26.
I like the lowish Qms of the B&C driver. It makes it much easier to drive them from a high impedance source without having to "fight" the usual very peaky bass-resonace that higher-Qms-drivers have.

Ipads doesnt do flash?! I have no problem seeing it on my Samsung Galaxy smartphone or my Ubuntu-laptop.

Johannes.

[Vix]

Originally Posted by Circlomanen

Yes, this is my B&C 10PS26.

Johannes.

I liked it. Sounds quite nice, even through crappy camera mic. Do you like them enough for a keeper? It looks like a sort of F.A.S.T. concept, bass in BIB and the smallish fullrange doing the top. On another thread there was an idea to build a Frugal horn 3 with some bass helpers. When I saw your video, I though it could be a good combination...

[jhutka]

With beginner's luck, I made some BIB's with 2" TBs for my computer. They sound great! So, in my naivete and armed with the BIB calculator, I started trying the design with others and was really disappointed. Still keeping things in a small scale, I have some surplus Vifa 3" drivers (TC9FD18-08) that I want to use.
Fs = 125 Hz
Vas = 1.241L
Qts = .89

The main difference with the successes and the failures is that the Qts on the failures was higher .

Is there other data that I'm missing that would render the design and the calculator ineffective?

[gafhenderson]

Originally Posted by jhutka

With beginner's luck, I made some BIB's with 2" TBs for my computer. They sound great! So, in my naivete and armed with the BIB calculator, I started trying the design with others and was really disappointed. Still keeping things in a small scale, I have some surplus Vifa 3" drivers (TC9FD18-08) that I want to use.
Fs = 125 Hz
Vas = 1.241L
Qts = .89

The main difference with the successes and the failures is that the Qts on the failures was higher .

Is there other data that I'm missing that would render the design and the calculator ineffective?

Problems I had with BiB and the 8 inch driver I'm playing with now, was the volume of the enclosure was always way to big for it, so it was full of holes. Messing around with hornresp to give a volume that gave a reasonable response ended up in the enclosure being too narrow/shallow to fit the mounting depth of the driver without a throat adapter set up. So perhaps it favours drivers that like nice big enclosures?

[GM]

Originally Posted by jhutka

The main difference with the successes and the failures is that the Qts on the failures was higher .

Is there other data that I'm missing that would render the design and the calculator ineffective?

Did you build all these, or just run sims? If built, where in room were they located? Remember, these are designed for some empirically arrived at internal damping, corner loading and at least ~75% of ceiling height in folded length, so the further away from the ideal, the more dips in the response and rolled off the bass.

As a general rule though, a higher Qts up to around 1.0 is desirable if it doesn't make the cab too large for the available space. FWIW, all the corner pipe horns [not BIBs per se] I did had high Qts drivers all the way up to a whopping ~2.45 Qts. Above about a 1.4 Qts, the pipe horn is a good choice to acoustically damp it down.

Nothing other than maybe increasing Qts on very low Qts drivers, then adding a bit of EQ to 'fill it up' or designing to a lower Fs to make it tall enough or in the case of low Fs drivers, increasing Fs to limit it to two folds.

GM

[jhutka]

Thanks GM

Originally Posted by GM

Did you build all these, or just run sims? If built, where in room were they located? Remember, these are designed for some empirically arrived at internal damping, corner loading and at least ~75% of ceiling height in folded length, so the further away from the ideal, the more dips in the response and rolled off the bass.
GM

I do not have the software or the know-how to run sims. If I understand what you are saying, I should chuck the idea of a scaled down BIB. Especially if the ceiling height is an integral part of the overall design.

However, I just measured and the ceiling is close to the right height with the speakers sitting up on the computer table. Hmmmm.

JHutka

[GM]

You’re welcome!

Scaled down BIBs are normally inverted, firing at the floor, but if it doesn't put the driver too high, then as you learned, spacing them up is an option.

GM

[Squeak]

Just straighten them out. That's been done before many times with success.

[jhutka]

Originally Posted by GM

You’re welcome!

Scaled down BIBs are normally inverted, firing at the floor, but if it doesn't put the driver too high, then as you learned, spacing them up is an option.

GM

I didn't think of them as down firing. Great idea! 2" to 3" enough rise off of the surface?

jhutka