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

Oh...! I didn't know that would work....

Fair enough! That would be even easier. and you could very easily try different sizes of chamber to suit.

But would be cool though...you could make a big box with the appropriate Sm and just cut lengths of ply to make the correct horn shape. That way you could easily have a 3.5 metre (137 inch) pipe length venting to ceiling with one bend. Damn I wish I could draw it for you!!!!

Hmmm. Interessssting.

Stroop
 
Scottmoose said:
Personally, I'd just mount the driver on a pod on the side & vent sideways into the main cabinet.

Perhaps doing the same in the front (a la Dalek) could make the trick too. The side pod has the advantage of being able to use the full depth of the BIB plus having some additional surface to launch the waves (thinking regards need of baffle step compensation)

Gastón
 
Sorry... what I used for the initial length conversion is:

L = 13464.54/ (2 * Fs) which is in the example of Zilla's page and somewhere in this thread.

Scotts uses

L = 13560/ (2 * Fs) which is also in Zilla's page but in the text, and also in this thread...

Which one is correct ? Both are... at different temperatures :)

It has to do with the speed of sound in air... approximately (quite)

c = 331 + 0.6 * theta

where c is the speed of sound (in meters per second) in free air, theta is the air temperature (in degrees Celsius). To have the same speed in inches per second, just multiply the above result by 2540.

Now the line length is set to be:

L = c / (2 * Fs)

so if theta = 18 degrees Celsius, you have the formula I used, and if theta = 22 degrees Celsius, you have the one Scott did.

Which one to use ? IMO, this is all approximate so they, as said, are starting points for experimentation. The "useful" point of the spreadsheet I posted is that it calculates a "corrected" length. Buth it seems it lets pipe end correction calculation... oh well...

:rolleyes:

Gastón
 
Disabled Account
Joined 2004
I use in both worksheets the same line length. I understood what you said when you had explain this to me before. :)

It looks like Dave's "corrected" height works as L/2 plus A(=B=C).
And yours as L/2 plus the difference from original line divided by 2.
Which is the correct calculation?
 
Greets!

I haven't taken the time yet to review the various spreadsheets, so don't know why they are different, but WRT the SoS value I found using 13560"/sec works best overall for me in-room while 13464.54"/sec is what MJK uses in his software, so is best for most accurate simming. Since they aren't all that accurate for BIBs, it's pretty much a moot point which one you use IMO.

Bottom line though is that the 'beauty' of a BIB alignment is that extreme dimensional accuracy isn't an audible issue as it can be with a typical vented or horn alignment since down low the room dominates the system's response, so when in doubt over fractional percentage differences in dimensions use whichever ones you want. With any type of speaker alignment though, I always recommend 'BIB' if for no other reason that it increases tuning flexibility.

GM

PS: Jeff, Hopefully one day soon there will be just one all inclusive spreadsheet available, but for now please add this to the BIB site.
 
Disabled Account
Joined 2004
:( I can't understand you Dave. Can you be more specific?

By the way,
I think I must stop playing around and start to build the BIBs! As GM said "Bottom line though is that the 'beauty' of a BIB alignment is that extreme dimensional accuracy isn't an audible issue .... .....so when in doubt over fractional percentage differences in dimensions use whichever ones you want."

Only one more question :D
Must I use two pieces of ply for the front baffle or there isn't a big problem to use one?

Thanks all of you! I'll stop now asking any more questions and I'll start to build! :smash:
 
Disabled Account
Joined 2004
hmm...
"To clear room enough so the back of the driver doesnt touch the internal baffle"
that's a really good advice! I'll use a suprabaffle too but some air for the driver would be great.
I like the idea for a solid wood too. I'll think about it, cause in my plans was to paint the whole cabinet blonde... and the suprabaffle and the base light cherry red. What kind of solid wood would be great for that?

Or just use birch ply for the external of the two baffles and finish it blonde?... :rolleyes: :confused:
 
http://www.zillaspeak.com/bib-godzillabib.asp

http://www.zillaspeak.com/fostex127eStraightPipe.asp


I am an amature when it comes to building boxes. I just do it as part of the entire speaker building process. In the name of cheap, i simply build my box from particle board/ply whatever and allow for chips, dents, scratches. Then i paint it all black (choose your color) and cover the front with a piece of knotty pine - also cheap. Sand and stain as desired. Poly sand and poly until desired. No one, even my wife, has complained about the look of these speakers. Rather, they all come over to touch them.

It's easy. But it does look a bit 'woody' and rustic on close examination imo. It's just a formula i came up with to cover up my amature woodworking skills.

Godzilla
 
Disabled Account
Joined 2004
thanks Godzilla! Love your work!

ghpicard,
what exactly do you mean as "baffle thickness" in your worksheet ?
The internal baffle or the external front baffle? :confused:

Tomorrow, I'll order the birch ply!! :smash:
I decided to build it all with birch ply with external front & rear baffles.
Suprabaffle and base will be from solid wood. But I'll decide about these after I'll build the cabinet.........
thanks for help!
 
resident said:
ghpicard,
what exactly do you mean as "baffle thickness" in your worksheet ?
The internal baffle or the external front baffle? :confused:
[/B]

Internal baffle.

Just for grins, and regarding the difference in length, just check out what happens with the line length when Fs of the driver changes, say, a couple of Hertz. This is quite normal in the life of the driver and even from one driver to another of the same batch.

I'm rebuilding the spreadsheet to include all of the enhancements seen here this last posts, and also enhanced the "Corrected" length, height and etc. to be geometrically exact. No big deal. This last one I'm doing just out of being a little obsessive on the math, but knowing that none of this is meant to be built with "less than 1 mm tolerance".

I will also add another wood sizer for butt-joints, as from all the photos around, this seems to be the method of choice. Especially because is the one I will use to build my FE166E BIB as soon as the weather gets less rainy and lets me use the terrace as carpenter shop.

Gastón
 
Hello all, this is my first post on this thread (and forum). I have been following this thread for some time now, have found it really interesting and admire the free exchange of ideas and open mindedness that prevail here. I plan to build a rough BIB and maybe another design to get an idea how full rangers sound but havent decided which driver to use. I was fairly settled on the 168 sigma as it has received good ‘press’ here and because it would also suit the ‘metronome’ design which I would like to build just because I like the look of it so much and it may fit better into my smallish room (10.5 x 12 x 16.5 ft.,HxWxL)
But now the FF165K has thrown a bit of a spanner into the works, being preferred by some over the 168ez and also being cheaper. Could anyone tell me whether the FF165K would also work in a metronome cabinet and is it still regarded as the VFM BIB champ? How are some of the 168ez BIBs sounding as they get more hours on them?
My current amp is grunty SS pre/power reputedly able to drive anything but from what I’ve understood from this thread I would be better off with something that could hardly drive anything . Is this correct? Is it to do with better sound quality from low powered and simpler circuits and/or the BIB using the resonances of the driver to extend the low frequencies rather than the amp damping them electrically? Please somebody enlighten me.
Well that’s it for now, I feel like someone who has come very, very late to a party but it seems there are some stayers here. Thanks in advance for any advice.
Regards Andrew
 
Hello, and welcome!

FWIW, I spent ages suggesting people try the 165 in the BIB as I'd found it a lovely combination. Jeff & Dan then tried it, and liked it, and there are at least another pair with the 165s around. The FF technically shouldn't work due to the very low Xmax, but the blunt reality is that it seems to. My budget choice -I'd take it over the 167 for this load, and any day over the 166 (which I'm not much of a fan of), providing you're mainly in the nearfield & don't go insane with the volume knob.

Yes, it will work in a Metronome, same caveat about volume -the Metronomes aren't as efficent as a pipe-horn, so they won't go as lound.

I suspect the Sig is ultimately the better unit, but it should be; it's a much more expensive driver. Sigma guys... the floor is yours.