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

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#2,141
hi stroop,

glad to read that you are enjoying your fe108ez's. they will improve after you put some time on the drivers and/or mod them. earlier in the thread (a few pages back? 🙂) scottmoose gave some advice on ways to break in the driver, throwing it in boxes, facing each other, covering with blankets, etc. to slam them a bit. i don't think you can really get to those levels in the bib unless you have very relaxed, or deaf, neighbors.

in your search for a matching amp i would definitely try out an inexpensive tripath amp.

http://www.41hz.com/

try the amp6 basic with a cheap smps powersupply, solder the speaker wires and interconnects directly to the amp board. try single stranded cat5 or thin magnet wire to lift the bass response. you can do all this for less than 50 euros and a few hours of soldering... if you like it, box it up and make it look nice. i'm using a charlize amp and a kookaburra or tube pre and expect you would get similar sound for a bit cheaper.

enjoy!


stroop said:
'Hmm, I'd rather have no bass than unpleasant, slow, bloated bass. Better to lose the octave or two all together than have it be honky, slow, wooly poop.

Musicality is higher up my list of wants than broad frequency response.'

DrewP...

Maybe I should clarify.....I meant it in regards to a pairing with my fe108's....which are a little strong up top and not bass heavy. And what bass they do have is really VERY nice!

And of course musicality is important.

Stroop
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Variac said:
OK, I don't understand how the BIBs work really, which will become quite obvious quite soon!

Here is a sketch of a kind of Double BIB that has the advantage of having the driver in the middle of the line as some I believe have mentioned is optimal. That's why I started on this path. It also is a very long line, if the height of the cabinet is 6' , the horn length would be 18', and the opening would be 22" x whatever the depth of the cabinet. IF it is possible to use this longer length then the lowest frequency could be extended.

Can the BIB be calc'ed for longer lengths and compensate with larger horn mouth or somethin'? Or is there a driver that requires an 18' length? If the throat is too big where the driver is we can use a bigger driver or make the depth of the cabinet less, like the monoliths, though I'd rather not.... The drawing shows an 8" driver but in this drawing a 12" would fit.

Just a possible variation if SAF is not much of an issue. The shape would be OK in my opinion, kind of mid-century looking. Also the wide face where the driver would go would augment the midrange which might be a good thing....

Comments on this might help us all understand the BIB better
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hi variac,

i like your idea for the second fold. i was considering something similar, except with the first third vertical and the last fold angled out. by doing this and cutting the mouth at an angle the bib should couple with the side walls better. using the normal line length, divided by 3, the bib is too short to couple with ceilings. of course you could always flip it upside down!
 
#2,142
Hi There,

Would anyone be so kind as to suggest cabinet dimensions for Fostex FE204 drivers?

Impedance : 8 ohm
Fs : 45Hz
Re : 6.81 ohm
Qes : 0.21
Qts : 0.2
Qms : 2.84
Vas : 51.4 L
Xmax : 1.5mm (0.059 in)

I think these were replaced by the FE206 or FE207... Any opinions as to whether they would be suitable in a BIB enclosure?

Thanks in advance.


🙂
 
#2,143
Yeah, they'll drop straight into the 206 box, no problem. Nice unit. You're quite right -the FE206E was the 204's replacement -specs are very similar.

Variac -that's a perfectly reasonable idea IMO. Ideal for drivers with an Fs of about 30Hz or so. Length is roughly equivalent to 1/2 Fs or whatever reasonable tuning frequency is desired.
 
#2,144
OK, Let's use the Pioneer B20FU20. It has an Fs of about 43hz and I just happen to own a pair....

I seem to remember about the BIB that it will give good response below Fs. Is this true? So a longer horn could be calc'ed to go to 30hz with the Pioneer? The fixed sizes seem to be that the height of the horn mouth be about 6' for an 8' ceiling, and the driver center needs to be about 3' off of the floor. The BIB I showed has a path of almost 19' and shortening it isn't easy due to the 6' and 3' lengths required.

So, can a Double BIB be made w/ the 19' length and the Pioneers or is this only for drivers with low Fs such as tru woofers?

If it does work, maybe the longer horn will have smoother response by interacting better with the room. Maybe it will go a bit lower. Maybe the driver in the middle of the path sounds a bit better?

What do you think?
 
#2,146
Variac said:
OK, Let's use the Pioneer B20FU20. It has an Fs of about 43hz and I just happen to own a pair....

I seem to remember about the BIB that it will give good response below Fs. Is this true? So a longer horn could be calc'ed to go to 30hz with the Pioneer? The fixed sizes seem to be that the height of the horn mouth be about 6' for an 8' ceiling, and the driver center needs to be about 3' off of the floor. The BIB I showed has a path of almost 19' and shortening it isn't easy due to the 6' and 3' lengths required.

So, can a Double BIB be made w/ the 19' length and the Pioneers or is this only for drivers with low Fs such as tru woofers?

If it does work, maybe the longer horn will have smoother response by interacting better with the room. Maybe it will go a bit lower. Maybe the driver in the middle of the path sounds a bit better?

What do you think?
Click to expand...

Driver position in a BIB proper is the least of the possible evils. Ideally it wants to be at about 0.416 line length, but normally that would put it on the floor, which isn't exactly ideal.

You have to be careful with line-length not to go too far below Fs. 0.707Fs is about the limit, or as GM points out, the midbass will suffer. A Pioneer tuned to 1/2 wave (157.2in line length, Zdriver 34in, keep Sl the same) will certainly give a solid 30Hz.

Ceiling height is not factored into any of the BIB simulations as Martin's sheets don't account for it (yet. This is changing though...) They're not all that fussy, so long as you don't have 30ft ceilings or some such excess. Even then though, pushed against a wall, they don't do badly.
 
#2,147
Scottmoose said:
You have to be careful with line-length not to go too far below Fs. 0.707Fs is about the limit, or as GM points out, the midbass will suffer.
Click to expand...

This is another of those things that has me confused. I know it's been mentioned several times in this thread, but I'm having a hard time making sense of it.

As a 1/4 wave pipe, a BIB would be tuned to Fs when 1/4 wavelength long. Most of the designs I've seen published here are 1/2 wavelength long. which means they are tuned to 1/2 Fs, well below the 0.7 Fs limit suggested.

Where is my thinking going wrong?

-- Dave
 
#2,148
Greg can explain this better than me, but meantime:

It's Fc rather than the final cut-off that's the critical parameter. For example, the 166 BIB is tuned to 38Hz, at which point it rolls off at 18db per octave to a final cut off of 24Hz. Note that all the BIB cabinets are tuned so that Fc is always above this point.

Also -tuning frequency of a line is a function of both length and cross-section along said length. An expanding line needs to be considerably longer than a straight or negative taper (narrowing) line for the same tuning frequency. See Martin King's Classic TL Alignment Tables for more. The upshot is that while a straight line tuned to 50Hz needs to be 67.2in long, a line with a 1:10 taper for example needs to be 95.5in long for the same tuning frequency. And so on.
 
#2,149
Hi Scott,
would you be so kind to make some BIB sim for Gradient W160AL8 speaker.
Here's T/S data

Measured TSP (German only):
Breitbandlautsprecher 176(143) mm
Übertragungsbereich 43-20000 Hz
Kennschalldruck 87 dB
Schwingspule 26/12 mm
belastbar 60 Watt
bewegte Masse 15 Gramm
Konusmembran aus Aluminium
Gummisicke, Stahlblechkorb, geschirmter Ferritmagnet
Nennimpedanz 8 Ohm
Gleichstromwiderstand 5,94 Ohm
Resonanzfrequenz 43 Hz
Gütefaktoren:
Qms 2,3
Qes 0,62
Qts 0,5
Äquivalenzvolumen (Vas) 20 Liter
Effektive Membranfläche (Sd) 125 cm²
Schwingspulenüberhang (Xmax) 3 mm
Schwingspuleninduktivität (Le) 0,47 mH

and there's MLTL sim for W160AL8
 

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#2,152
I'd think you would have a tough time really putting together a proper design or reaping the benefits of a BIB from a desktop speaker. No doubt, a fun idea. Could work if you could put them on a floor (or low shelving?) in front of a wall or something, however. Perhaps a small, (tiny?) horn would provide better results. My initial thoughts, anyway.
 
#2,155
I'm getting close to the stage now where I will be building a pair of BIB's for fostex fe206e's.

Just wondering if anyone could let me know what kind of music these speakers would be suited to?

I listen to a very broad range of music, pretty much everything excluding classical.
 
#2,157
one1speed said:
I'd think you would have a tough time really putting together a proper design or reaping the benefits of a BIB from a desktop speaker. No doubt, a fun idea. Could work if you could put them on a floor (or low shelving?) in front of a wall or something, however. Perhaps a small, (tiny?) horn would provide better results. My initial thoughts, anyway.
Click to expand...

I guess desktop may be the wrong word. I was thinking of making a small set for my shop at work, more than likely would be placed between shelves on the bench. Can not have anything too big, hospitals frown on loud music. I was guessing that the line length would be just over 3 feet. So these could be small. I just think it would be great when someone asked what all this stuff was, and I could reply: Oh, thats an o-scope, freq-gen, BIB, volume tester,............
 
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