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

BiB Spreadsheet / Calculator Gotcha

rjbond3rd,
You have found my dirty little secret! I also see that you are a perfectionist! The calculator was made with the intent of the bottom being installed outside of the sidewall as opposed to inside, and for a longer slant piece. The only reason for this was to give the greatest amount of wood needed when budgeting. If one decided to put the bottom inside the walls, then a slight calculation should be done to the slant and the bottom piece (my fault for not putting that disclaimer on the sheet, will add it soon). The spreadsheet is just a basic tool to help in the setup of the cabinets, and to give a bit of a "Fudge Factor" when the fitting and gluing begin. Many of us here are just as dangerous as we are crafty with our woodworking skills. So all the measurements are not spot-on, but they should give a bit of room for mistakes or differences in build styles. So measure once and cut twice.

If you would like to help with the formulas to get the calculations a bit closer, please send me an email. It looks like you may be better at them than I am.
 
Hi Zayne742,

Aha! That makes absolute sense. I think my taking everything so literally is a sign of newbiness.

I am extremely impressed with the spreadsheet -- if it didn't exist, I'd still be working it out. And you are definitely far, far better than me at spreadsheets, I can see. However, I will definitely zap you whatever revised formulas I can come up with for the order of rounding (it may be possible to avoid rounding an already round value, for example). In the end, it's still totally excellent as it is!

Regarding being a perfectionist, oh if you could only see my hideous-looking BiB's right now. I glued up the first two sides (I only have four clamps). After four hours, I was pondering why their width-to-depth ratio looked more "square" than the design's ratio of 1:1.4142.

Ahhh! I had glued the wrong two edges together. I popped off the clamps and had to physically rip the two boards apart, stripping away the top layer of ply from one board. Needless to say, that atrocity is going to be on the back. :( I really suck at this.
 
Wow! your shop is like mine, that is why I said we were just as dangerous as crafty! The sheets drove me crazy for a week. Had never really used formulas in Excel, but decided it was time to learn, and at least it was for a hobby and not work. The rounding was put in there so someone was not standin in their shop saying, "Where the h*** is 0.36698 on this ruler." Let me know anything you come up with. I know there has to be a mistake or two in there. And if anyone knows how to build switches half way decent, to switch between metric and impereal, and you would like to contribute........
 
>>> So measure once and cut twice.

LOL! I always do.

>>> These boxes aren't really about hitting very specific alignments. Given that they're corner horns, their ultimate performance depends on the room anyway...

That's another thing i love about BIBs. Once built (even if the measurements are off a little) they still need to be fine tuned as per each room. Room positioning - how close to a corner/backwall - and stuffing the enclosure probably play as large or larger role in finalizing their overall performance.

Experimentation with room position is something that must be done with any speaker design. Monitors on stands drove me nuts with thier endless possibilities (against the wall, away from the wall, in the corner, away from the corner, etc...). At least with the BIB we know corner loading is the position it is designed for. That's our reference. Along with stuffing, we start by positioning the BIB from the corner to find the best overall sound in our room.
 
Hi guys, I hereby volunteer to noodle away on whatever small improvements might be made to the already awesome spreadsheet.

Wouldn't it be great to have a systematic, repeatable method of BiB positioning? A series of steps using test tones maybe?

Or some optimizing rule of thumb that says mouth should be X distance from the apex of the corner, where X is related (somehow) to the line length? I know the corner forms the horn's final expansion, and every room is different, but it would be cool to comprehend the theoretically ideal mouth-to-apex positioning.
 
I have been contemplating what I'm perceiving as problems
with the front rather than the top-- specifically bringing mids forward.

So combining some ideas; If you took Godzillas wider front
baffle (wider rather than supra) and gave it a wing (idea 2) and made the wing the shape of the conche diagram shown a few days ago (idea 3) how could all that be brought together in design terms?
 
Hi Lon, hmm. Would the test tone CD be of any use in nailing down the frequency range that is recessed? If it's low enough, it might be treatable with a wider baffle but it would be good to know what frequency is the issue.

However, this second baffle was made with more accurate divider length, true? Is it possible that this new BiB is "correct" and flatter whereas the old BiB is "incorrect" and peakier? In other words, maybe your new BiB is already "fixed"?

One last thought: playing the "white noise" track through each might instantly tell you which one sounds off. You've probably already tried all these ideas!
 
rjbond3rd said:
Hi Lon, hmm. Would the test tone CD be of any use in nailing down the frequency range that is recessed? If it's low enough, it might be treatable with a wider baffle but it would be good to know what frequency is the issue.

However, this second baffle was made with more accurate divider length, true? Is it possible that this new BiB is "correct" and flatter whereas the old BiB is "incorrect" and peakier? In other words, maybe your new BiB is already "fixed"?

One last thought: playing the "white noise" track through each might instantly tell you which one sounds off. You've probably already tried all these ideas!

'Tis true there's a lot of variables with these cobbled together ones.

I think the problem one (older one is happily playing with an MLTL)
would have to be done with an SPL meter or mike'ed setup which I don't have. Or scopes or other test gear. So if the
test tone is played the level can be tested against it's neighboring tones for comparison for levels.

Since the drivers are the same, someone brought up the other irritating notion that one might be shot or going.

What happened when I set up the MLTL and BIB both using
FE127e is that I got significant sound stage back from the MLTL side.

The GM MLTL build has always been the most satisfying. It may be more appropriate for the close up listening position I use.

OTOH I'd hate to lose the effects given for movie sound effects and such. (I have never wanted to use a sub.)

For reference, my MLTL looks pretty much like the drawing at
zillaspeak but has an extra 'shelf' or full width brace below where the port extends at the bottom.

http://www.zillaspeak.com/fostex127eMLTL.asp

This build has been described by me many times.

Next step for me in refining the sound suited to this space is
to move up to a 5 in or 5.5 in like the Tangband shown here.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-850
 
Lon:
What I have experienced is that being the BIB highly dependent on the room reinforcement effect, *I* need to be in a given position to get correct bass and sub-bass.
My room (as any room) is full of nulls and maximums in the bass realm that are frequency dependent. I have to sit in a sweet spot for bass, usually near the back wall (no sofas yet ;) ). Then I tune the toe-in for the desired highs response. That sweet spot is usually quite wide.
The side wing helps filling the midbass.
For complex music, well, it's a FR with all the pros and cons.

FWIW I use the BIBs for HT duties (stereo only, for now) with a 15+15W amp without lacking much sub-bass.

One of the BIBs is in a corner, while the other one is against a wall.

Gastón
 
mp3 test tones

http://users.swing.be/hdepra/home/P22/E-sounds.html

A quick and dirty test from this test tone site using only
40, 50 and 60 hz.

I then switched the leads on the channels. This effectively
gave the sound level a switch. The problem may be in my SS
receiver. But I want to do another test with a direct dvd input
which doesn't use the soundcard.

I have some more test tones on a cd. The prblem with those is when I
burned then to disk, the file names did not give any tone numbers.


One more levels test and I'll report back.
 
Got the wire changed. Check.

Did a test using the RP U100 white noise generator in a sweep. Check.

Things sound pretty good. *But* I still have to retest with tones.
The tones were way off.

Next I swap the drivers. But I think all of this is just
confusing me. If the tone level swaps sides that means it's the
BIB.

To review: in tones (40, 50, 60) MLTL side louder, BIB not so good.

As it stands, I at least I don't think my amp/receiver or FE127es are bad. On the HD FM music stream through the soundcard things sound pretty good.

:cannotbe:
 
Hi guys,

Scott, I'm totally stumped as to why Loninappleton's MLTL w/o BSC could have more bass than his BiB. Do you have a theory?

Zayne, do you mean in-progress pics? If so, I will take them. If you mean final pics, I will have those by the end of next week. I'm limited by only having four clamps. They won't be beautiful (!) but it will be interesting to test the FE166ES-R's in them (Paba, are you out there?)
 
Re: some tweakage is needed

loninappleton said:

Interior treatment is similar but not identical.

The BIB original is giving a better midrange whereas the
double front baffle (one cutout 4 in, the interior cutout 5 in)
gives the mids coming out the front a muted effect.

So suprabaffle on these.

I do not think minor surgery such as chamfering the inside baffle
would change this.

The original 'good sounding' BIB currently has the thin wire
tweak on it but here again I think this is minor.

Both use FE127e. Both are about the same same size and the
newer sibling is closer to the calculator measures.

What concerns me is what's coming out the front and less so
what is coming out the top.

Hmm, until all the variables of driver performance, etc. are accounted for, you can't really know much about the cab's performance and if I'm understanding you there's more differences between the cab than just a double thickness front baffle, further diluting the ability to pinpoint any perceived differences.

WRT chamfering Vs using a stepped flare, my measurably hearing impaired 65 yr old buddy recently had no problem perceiving the difference when I made some adapters to convert his RS 40-1354 MLTL over to CSS FR125S drivers, though as always YMMV.

Anyway, when you say 'mids', this can mean different BWs to different folks, so please expand on what you mean since it can cover from ~160 - 1280 up to ~5120 Hz depending on the source with only ~ an octave of it being in the pipe's passband.

GM