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

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#2,162
Scottmoose said:


Driver position in a BIB proper..........Ideally it wants to be at about 0.416 line length...........

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...

Greets!

The 'ideal'/'optimum' number seems to be sliding down the pipe with increasing posts 😕, so are they for specific driver alignments and are they calc'd or found through fiddling with a sim?

Hmm, design criteria for different alignments seem to be getting commingled here.......

TC's 'BIB' alignment is acoustically 1/2 WL long of Fs instead of the 'classic' TL's 1/4 WL, so most others in this thread are quasi-BIB, IOW conical horns with similar FRs, though some are distinctly not, as the case may be.

The general rule-of-thumb to limit vented alignments to 0.707*Fs applies to most since below this point there's nothing to be gained and unless there's mass quantities of displacement and/or acoustic (box) efficiency available then some form of EQ is required to protect the driver. The BIB blithely ignores this since its gain if not damped too much is sufficient for the app it's designed for, i.e. relatively small ~FR drivers that otherwise need some help with the lowest octaves. Higher power rated, and/or lower Fs drivers need more protection, especially the 'sub' BIBs, so with rare exception should be tuned within the 0.707*Fs limit otherwise the mid-bass ('slam' factor) will suffer along with potentially excessive distortion that will ripple up through the BW, modulating voices, etc. (aka 'gargling').

GM
 
#2,163
Cheers for that Greg

Agreed re the driver positioning varying depending on the box. FWIW, I've found with the regular BIB cabinets, the best response tends to come from having a Zdriver of 0.2 - 0.21 line-length. For the inverted types (assuming a smaller driver) which might as well be considered as unfolded for the purposes of a sim, the 0.416 position Martin suggests for a 1:10 taper ratio appears to get us ~close enough for differences to become relatively minor, at least in a 1/2 space calculation. That said, I haven't built an inverted or straight type, and as they're not as popular as the normal sorts, I haven't run as many sims on them either, so I speak under correction.

Scott
 
#2,164
Bib with Fostex FE206E

Hi,

I'm calculating a bib with FE206 drives I have already. The problem I found is that with a 87" height, the Zdriver is 35", so that the driver is 52" from floor. Too much.

So I arranged this solution:

bib1.jpg


Zdriver is still 35" but at 43" from floor. What do you think?

Regards

Thomas
 
#2,165
Looking verrry nice Thomaselliot!

My 'little' numbers are getting better all the time! I'd say I've just hit 100 hours on the fe108's. I might rock the neighbours at some point to shake 'em up a little see what effect that has!

Sorry for the delay Gianstairs! But thanks for the recommendation! I am having real trouble deciding what amp I should try and build for them how did people decide? options are;

Decware SET- satisfaction of own build and control over what goes inside.
2020 tripath variant- again like above but tricky soldering and no tube glory(whatever that means)....
Ucd180 - seems easier to put together and possibly best sound(?) but satisfaction/ego trip, maybe a little lower.

or if I should just by an Antique audio tube amp and modify until I get the hang of things regarding amps.

Cheers Stroop
 
#2,168
FE206E BIB

Hi,

I made some corrections. Width=25cm Depth=W*1,4=36cm Height=250cm Line lenght=420cm. Ceiling is 310 cm high.

bib2.jpg


The main reason for this mod is to have the driver at 90cm from floor (otherwise it would be at 150cm).

Have you any hint or observations?

Thanks in advance

Thomas
 
#2,173
Greg's the person to ask on damping materials. I'd use stiff fiberglass, or bitumen sheets of the sort used for damping car body panels laminated to the desired thickness. Some peopel like rubber. I'm not too convinced though as it seems to blunt dynamics.

I don't think there's any drawings showing it, but it's not too difficult to work out. Line the front of the sloping baffle from the top to just below the driver. Line one sidewall from the top to just below the driver (we're talking about the 1st 1/2 of the line here) and put a layer down covering the entire internal bottom of the cabinet.
 
#2,174
stuffing

Just my 2 cents on stuffing. I used quilt batting, layered about 1-2 inches thick. I lined the very bottom of the cabinet, and the entire length of the back of the internal baffle, the side towards the top opening. I tested a few configurations before buttoning them together. This was the one I like the best. And thus far, I am very pleased. This may have been overkill, but it helped with the cheap drivers I am using. They sound great for music of all kinds, and for movies. One work of caution though, If you own cats...... be carefull with the stuffing! I would also recommend stapling into place.
 
#2,175
New driver consideration

http://www.tb-speaker.com/detail/1208_03/w4-937sa.htm

Could someone plot this driver and give possible box dimensions if they have time. It looks like it may not be so bad in a BIB.

Thanks a million, ahead of time!

DIAPHRAGM MTL Paper
SURROUND MTL Rubber
NOMINAL IMPEDANCE 8 W
DCR IMPEDANCE 6.8 W
SENSITIVITY 1W/1m 88 dB
FREQUENCY RESPONSE 65-20K Hz
FREE AIR RESONANCE 65 Hz
VOICE COIL DIAMETER 32 mm
AIR GAP HEIGHT 6 mm
RATED POWER INPUT 25 W
MAXIMUM POWER INPUT 50 W
FORCE FACTOR, BL 6.68 TM
MAGNET WEIGHT Neodymium
MOVING MASS 4.92 g
FERRO FLUID ENHANCED No
SUSPENSION COMPL. 1052MN-1
EFFEC.PISTON AREA 0.0057M2
Levc 0.49mH
Zo 31.9ohm
X-max 4.5 mm
Vas 4.86 Litr.
Qts 0.26
Qms 1.22
Qes 0.33
 
#2,177
lining

The treatment I used in my single BIB mule (test box) was per Scott's Greg's instructions to place some batting at the closed peak,
a full inch deep covering of the base. But then I used 10 inch square pieces around the mouth (terminus) on four sides and have kept it that way.


Mine were closed up before I had any knowledge of damping one of
the sides because I've good success with using none in other builds.
 
#2,179
Too much... info overload...

First off...I am brand new to this forum. This is my first post (so please be gentle!)

I must say I am delighted to find, on my first search, loads of info about my intended speaker build the Cain design BIB.

To start off with I need advice on the best drivers for this design. I can justify any of the Fostex range, so not trying to cut costs too much. I am looking for a slightly warmer than neutral overall balance if poss, and can place them near a rear wall / corner.

Size, build plans etc I know is all here - but here's my point. I can find it all in this HUGE thread. Ahh very frustrating. I want to know so much and I want to read it in one evening and order my drivers tomorrow morning.

Am I being too impatient? Do I need to read all 218 pages of this thread? can someone point me to the roght pages for the info I seek?

Which drivers, what overall dims of cabinet and poss a series of photos.

Many thankyous in advance, you'll be hearing a lot more from me, I can feel the excitement building already.
 
#2,180
Go through the listed specs on Zilla's site. They've got freq plots, so you can pick what you like that way.

The FE168Sig is generally concidered to be the high end choice among the Fostex, though I'm more interested in the spacious bottom end of the FF series, and I would go with the FF225K if I could, though you will need a supertweeter with those.

Pretty much anything in the Fostex line from 4.5"ers and up should be acceptible in BiB full range, though you start trading top end for bottom end when you get into the 8"ers.

Maybe a touch impatient as there have been tons of drivers discussed. Not so many actually built, but there have been some built that aren't listed yet.

Kensai
 
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