Elementary questions related to BiB speakers

GM, thank you for the explanation and the chart.

About the radius as shown here, how does it pertain to a pipe which has a linear rate of expansion as in a Bib?

I will certainly be putting the pipes in the corners, but with them tuned to 50 Hz, with a height of 68 inches and a ceiling which is 12.5 feet high, i doubt if there will be any useable benefit from the ceiling.

You're welcome!

It just adds an acoustical straight pipe coupling, but @ K = 0.732 it will be good enough and due to corner loading it's better to build it inverted, so floor gapped.

That said, adding a 'top hat' to a normal BIB to get it within this gap at the ceiling will in theory tune it to ~1128.58/4/12.5 = 22.6 Hz, which if you have any recordings with true sub bass it will provide my preferred 'is it live or is it Memorex' performance since the lower the fundamental, the wider ('richer') the harmonic structure.
 
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You can also put the BiB on its head and put some pieces of wood under the four corners to lift the BiB up a few inches. Maybe move the speakers closer to the fold then so they're not at "knee" but at "ear level". of you Google "ibib", as in "inverted bib" you might even find the thread or pdf file on this forum. 🙂
Thank you for your encouraging response and for the suggestion, Irish Roy! Actually, i was in a dilemma between the top firing layout and the floor firing one. Any difference in how they sound, subjectively speaking?
 
You're welcome!

It just adds an acoustical straight pipe coupling, but @ K = 0.732 it will be good enough and due to corner loading it's better to build it inverted, so floor gapped.

That said, adding a 'top hat' to a normal BIB to get it within this gap at the ceiling will in theory tune it to ~1128.58/4/12.5 = 22.6 Hz, which if you have any recordings with true sub bass it will provide my preferred 'is it live or is it Memorex' performance since the lower the fundamental, the wider ('richer') the harmonic structure.
Thank you, GM! I appreciate your encouraging response and suggestions.

Same question as above:
Any difference in how the top firing layout and the floor firing one sound, subjectively speaking?
 
Thank you for your encouraging response and for the suggestion, Irish Roy! Actually, i was in a dilemma between the top firing layout and the floor firing one. Any difference in how they sound, subjectively speaking?
I have no experience with an upside-down BIB. I'd just go build a normal BIB with some cheap plywood or MDF. See if you like the characteristic and go from there.

The sound is enormous and has a lot of body to it. The sound is not like a horn, not very dynamic but extremely linear and predictable. Makes for easy listening. I'd say the sound of a BIB is not lightning-fast like some horns. Instead it wins me over by being relaxed and powerful at the same time.

IMO, I 'll never need a subwoofer when I've got my BIBs.
 
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Thank you, GM. This certainly gives a fair idea of how it is likely to behave.

Only 1 more question - In case of a floor firing, inverted Bib on stilts, how much above the floor should the terminus be raised so as not to compromise the operation? Is there a recommended height wrt the area of the terminus? I could not find any such mention on the iBib pages.
 
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@irishrOy

Point noted, Sir! Thank you for the link! Not synthetic; truly organ-ic! 😀

I can quite imagine the enormous sound as you describe as almost recreating the spaciousness of a Church. Might as well try Bach's Toccata & Fugue. I find it brilliantly composed!

The drivers i plan on have an Fs = 50 Hz. Would a pipe tuned to 50 Hz be up to what you experience?
 
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The drivers i plan on have an Fs = 50 Hz. Would a pipe tuned to 50 Hz be up to what you experience?
I don't know exactly. I have W8 1772's and their Fs is ~42, I think, and the BiBs are "tuned" to 42Hz as well. Mainly the tuning-frequency is determined by the height or length of the BIBs. If I wanted to tune them lower, I would have had to build them higher, but that wasn't possible :-D
I have heard it's possible and sometimes "advised" to tune the speakers a bit lower than the chassis themselves to support them down low.

Though I would guess that "even" with 50Hz as a tuning frequency you will have a lot of bass output because the BIBs are simply a lot of "more is better". And if you build a BIb that's ~1.8m tall, it would support a frequency of 45Hz (45Hz wavelength in air is ~7.5m, according to https://www.omnicalculator.com/physics/wavelength, and 1/4 of 7.5m is about 1.8m). Either way, you can't go wrong 😀
 
With a rated Xmax of 2.2 mm, and as suggested by Scott, i do not feel inclined to tune the pipes lower than 50 Hz. But i find your words convincing, and therefore, plan to proceed with the design! The drivers are 12" chassis, and they call for a terminus area of 2,200+ sq. cm. - that is going to be large scale. 😀
 
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I've only built/heard BiBs with a pair of Fostex 166e and the bass was surreal for a pair of 6" drivers. I'm really tempted to make a pair with the cheap SB Acoustics SB20FRPC-8 8.
It would be a fun, inexpensive project but the negotiations to bring them into the house may be COSTLY.
12" drivers? I'd love to see/hear/feel that...
 
Thank you, GM.

Only 1 more question - In case of a floor firing, inverted Bib on stilts, how much above the floor should the terminus be raised so as not to compromise the operation? Is there a recommended height wrt the area of the terminus? I could not find any such mention on the iBib pages.
You're welcome!

Same as ceiling loaded.

Not for BIB since it needs compression loading, otherwise horn math I lack the math skills to calc would apply, but Hornresp among some other horn programs can sim it.
 
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I don't know exactly. I have W8 1772's and their Fs is ~42, I think, and the BiBs are "tuned" to 42Hz as well. Mainly the tuning-frequency is determined by the height or length of the BIBs. If I wanted to tune them lower, I would have had to build them higher, but that wasn't possible :-D
I have heard it's possible and sometimes "advised" to tune the speakers a bit lower than the chassis themselves to support them down low.

Though I would guess that "even" with 50Hz as a tuning frequency you will have a lot of bass output because the BIBs are simply a lot of "more is better". And if you build a BIb that's ~1.8m tall, it would support a frequency of 45Hz (45Hz wavelength in air is ~7.5m, according to https://www.omnicalculator.com/physics/wavelength, and 1/4 of 7.5m is about 1.8m). Either way, you can't go wrong 😀
The BIB math tunes to an octave below Fs, i.e. 42 = > ~21 Hz Fp in that it's the acoustical pathlength + boundary loading that sets tuning, not height per se.

octaves:

Fh = Fl*2^n

Fl = Fh/2^n

n = ln*[Fh/Fl]/ln[2]

where:

Fh = upper frequency
fl = lower frequency, or the XO point in this case
n = octave spread
 
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once you've built them, dont play electronic music to "test the bass". Instead, give organ music a try. That's where the BIBs shine.
I find your descriptions of bib-sound very accurate.

On a local DIY audio forum, someone described the difference between "pressure in the recording" and "pressure added by the loudspeaker"... That hits my feeling about the BIB perfectly. It can be very punchy if the recording is punchy, it isn't when the recording isn't.

And yes, organ pedal notes are something else with a BIB. 🤭

There are some symphonic orchestra pieces where the timpani play a "subsonic note" by beating the timpani at a certain rhythm. To my delight, subsonic pedal notes of an organ have that percussive character. 🥰
 
I've only built/heard BiBs with a pair of Fostex 166e and the bass was surreal for a pair of 6" drivers. I'm really tempted to make a pair with the cheap SB Acoustics SB20FRPC-8 8.
It would be a fun, inexpensive project but the negotiations to bring them into the house may be COSTLY.
12" drivers? I'd love to see/hear/feel that...
Your description of the 6" Fostex based pipes gives a good hint of what to expect!

W.r.t. the 12" wide band PA driver based proposed pipes, fortunately God has blessed me by exempting me from having to deal with the dreaded WAF and the negotiations which entail!! 😀
 
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Same as ceiling loaded.

Not for BIB since it needs compression loading, otherwise horn math I lack the math skills to calc would apply, but Hornresp among some other horn programs can sim it.
Okay.

A Bib needing compression loading.... is it just a different phrase.... a different way of saying it needs to be "mildly mass loaded"? By that i mean that the effective area of the terminus is slightly reduced (the terminus is mildly strangled) owing to the proximity with the ceiling/floor, even though it is not with the intent to achieve a specific tuning as in usual mass loaded pipes.

Is this a correct understanding?
 
Sujat,

Have you tried out the "BiB calculator" *.xls file that was developed with GM's guidance? You input the driver's parameters there are it will generate the dimensions of your cabinet.

The BiB design is under appreciated - probably because of the physical dimensions. In my experience it can generate significant low frequency output from modestly sized drivers if placed in reasonable proximity to corners/or wall behind the speakers.
 
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Yes indeed, @zman01

Have been playing with the BiB xls sheet with different drivers so as to get an idea of the internal width and depth it suggests for different Vas and Qts. The pipe length is pretty straightforward.

Thank you for your kind suggestion, Zia'ji. 🙏
 
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