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

Still in progress. Not all in place. As you can see, it's rough. Old and warped fir boards, I accidentally used a crooked saw guide and "solved" both with a lot of void filling synthetic glue. It is solid enough for a prototype, but enough to improve in a later build.
 

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It will be a week or two before I can do measurements on this thing. I like it so far. It's not fully in a corner now, so I can't judge all of its bass potential, but there certainly is more than anticipated. Deeper as well. With the subs switched on, it takes on epic form. I am quite surprised how loud I can turn it. Drivers are never visibly moving and even when touching with my finger don't seem to move that much.

My main objective was extending range to better meet my subs, and a bit lower if possible. That objective seems to have been met quite well! The subjective tonal balance is much improved as well, more warmth. There is more punch as well, this may be just more power in that area that was lacking at the crossover between mids and sub.

I really miss a second BiB to listen in stereo, though!

We'll be on vacation for about a week, I'll be looking into some measurements after that. So far, thank you very much to Terry Cain, and Scott and GM! A lot of fun and a perfect place for my little drivers to play!
 
A very preliminary measurement. In this graph, a single Visaton driver in a cork/ply sealed box of 0.8 liter (in green) and the arrays in my BiB variation (in purple). Both measurements from the listening position. I normalized to 1 kHz and added about 5 dB as hornresp suggested that kind of gain in efficiency, more or less. It might work out differently in real life, but gave me a starting point to compare graphs and assess pros and cons.

The sealed box was raised 1,5 meter off the floor in a corner, the BiB was against a wall ( and standing on the floor), so similar loading conditions? The BiB is intended for corner loading, but this was not available today. Obviously, already more extension down below, I think the big hump at 500-600 Hz is baffle step.

I hope to be able to try out corner loading soon. For the time being, crossing to a sub at 110 Hz seems OK.

I am quite surprised at the results so far.
 

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I just built a second one. Evaluating is easier in stereo. I also saw the cat running out from the mouth of the original one, he had been sleeping there. 🙂 Unfortunately, he also pulled loose 4 of the connections, so the array was only partly working. I fixed that as well. So far, big sound but too much lowmids/upper bass (booming male voice) and the result is kind of dull.

Now for some time to measure. And time to the audyssey calibration.
 
I just built a second one. Evaluating is easier in stereo. I also saw the cat running out from the mouth of the original one, he had been sleeping there. 🙂 Unfortunately, he also pulled loose 4 of the connections, so the array was only partly working. I fixed that as well. So far, big sound but too much lowmids/upper bass (booming male voice) and the result is kind of dull.

Now for some time to measure. And time to the audyssey calibration.

Nice to follow your journey Ivo, best of luck! Keep us posted. You pretty much have your own page is this thread, which is pretty cool.

Cheers.
 
Was the measurement taken with the wires disconnected?

Not surprised about the 'boom' as without significant internal damping these tend to need a really low tuning and let its 3rd harmonic null damp a strong room mode and why I typically mass loaded them with a vent Av = Sd.

GM
 
Stuff until you get the sound you want. One of my BIBs is about 5 feet tall so lay it down and use a broomstick to push AcoustaStuff to the bottom of the cabinet. This will reduce / eliminate the boom. Unstuffed, too much midrange finds its way out the top of the BIB - stuff it a little at a time to tune to taste. If you don't feel you are getting enough treble you may consider adding a tweeter. I have one on the rear. Good luck!
 
Stuff until you get the sound you want. One of my BIBs is about 5 feet tall so lay it down and use a broomstick to push AcoustaStuff to the bottom of the cabinet. This will reduce / eliminate the boom. Unstuffed, too much midrange finds its way out the top of the BIB - stuff it a little at a time to tune to taste. If you don't feel you are getting enough treble you may consider adding a tweeter. I have one on the rear. Good luck!

Thanks. I bet there is still lots to win with stuffing. During the first session of measurements, I made some measurements at the mouth end. Response of the horn was smooth and cut off steeply at its upper roll-off. Roll-off seemed a bit high. Since it could have been with faulty wiring, I didn't post it afterwards, but perhaps stuffing can lower that roll-off a bit and reduce the bump in summed/in-room response.

For now, I quickly ran the autocalibration routine from my AV receiver. It seriously attacked the bump and sound became much clearer and brighter. Simulation of the array in Boxsim indicated basically enough and extended treble, so maybe a tweeter is not nevessary in the end. I am not ideologically against it.
 
Hi All, I made a pair of these iBibs years ago and they still leave me shaking my head at how great they sound on well recorded material. So, I'm building a pair for my girlfriend and made a mistake in cutting the rare wood we're using for the face 😡 and am wondering how to proceed. 🙁

The pair I built had the drivers centered 6 3/4" down from the top of the inside of the cabinet but that was not based on any calculation - it was based on a guess by looking at the picture below. Due to the depth of the driver and the internal slant piece it was about as low on the face as it could possibly go. The way I cut the wood for these speakers, the drivers will be centered 5 1/2" down from the top of the inside of the cabinet.

Will this make any appreciable difference in the sound? Maybe even closer to what is optimum? I am just trying to figure out how to best salvage the wood we're using. Thank you in advance for any help!

Below is post #4397 for post location and in case the photo is not attached.

Here's an exerpt of the bib calculator spreadsheet from http://www.zillaspeak.com/bib-howtobuild.asp

The nice result is using the "rounded dimensions" and the automatic cut calculations at the very bottom.

Attached some pics of the results in cedar.

Driver Brand dayton
Driver Model Rs100-4
Fs 80.2
Vas (cu. Ft) 0.07
Qts 0.48
Line Length 83.944
Folded Height 41.972
Vb 0.567
Sm 23.358
Depth (internal) 5.747
Width (internal) 4.064
zdriver 18.216
a-b-c 2.874
Conversion
Liters
1
Cubic Feet
0.04

Cabinet
Wood Width 0.750
Outside Dimensions
Width (external) 5.564
Depth (external) 7.247
Height (external) 42.722

Rounded Dimensions
Width (external) 5.500
Depth (external) 7.000
Height (external) 42.5

Cut Boards Per Box
Front/Back 2 each
Width 5.500
Length 42.500
Sides 2 each
Width 5.500
Length 42.500
Slant 1 each
Width 4.000
Length 39.750
Bottom 1 each
Width 4.000
Length 5.500
 
Glad you're enjoying them so much too! For the money i can't imagine what else would come close!

Where are your drivers located?

I'll post pics of our build also, but here is the photo from the original post.
 

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