| just a guy |
I've read most of the BIB thread and the possiblility of an upside down BIB has been brought up a couple of times. The answer was that an upside down BIB is the subject for a new thread, so I guess this is it.
This possible mod is necessitated by environment, not a desire to be difficult. I have a pair of 206's and would like to try them in a BIB (and at least 2 other enclosures). I have 2 rooms these could be used in (if I make them pretty enough) but one room has 7.5 foot ceiling, the other has huge vaulted ceiling. The 206 BIB height will not work in either room, too short in one, too tall in the other. I could add another fold, but then it would be useful only in the small room, and a bit short even in there.
I would rather make them 'reasonably' room independant (even if there is really no such thing). The only solution I can think of to make these work in both rooms is to flip it upside down and vent out the back. There are some obvious drawbacks, but I see opportunity as well (maybe - but I'm not THAT bright).
The major drawback I see is that the line will not be long enough by about a foot (or whatever height the vent at the back turns out to be - for example, the line length ends where the terminus begins, which throws the driver position in the line out from the calculated ideal as well as changing the line tuning).
You would not be able to push a back loaded BIB into the back wall, or corner, but is that a weakness or a strength? I understand the need to use the corner, or at least the ceiling and back wall to form the final horn expansion, but looking at the different BIB sizes and invariably different environments they will be playing in, the final expansion does not seem to be crucial and I don't think bottom/back firing would be a deal breaker in and of itself as far as the final horn expansion is concerned.
Using a different type of terminus could make the upside down BIB a solution instead of a problem, I think. By using a k-slot instead of a large terminus COULD potentially clean up some of the response ripple, and at the same time, mass load the terminus a bit (by being a smaller terminus than the huge vent top firing BIB) to lower the pipe resonance back down to where it would have been if the full pipe length were used (considering the back firing terminus shortens the line). In addition, the driver mounting position could be changed to the theoretically 'best' 40 something % that I've seen mentioned again and again, which is not possible in the top firing BIB.
So is this just stupid or what?
RECAP (just because I don't think that was very clear) - Make a regular BIB, turn it upside down, cut a k slot in the back at the bottom and move the driver to whatever is the theoretical best mounting spot, as Scottmoose has referred to several times (somewhere a bit further down the line). |
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| just a guy |
On second thought, strike the alternate driver mounting position, it wouldn't work (optimal is TOO far down the line).
But what about the upside down and back firing mass loaded karlson slot idea? |
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| GM |
Greets!
FWIW, all the 'BIB' pipe horns I did were floor or corner loaded and 'choked' by a material thickness vent = Sd as I couldn't afford to have the driver unloaded enough for TT 'rumble'/vinyl warp/amp clipping to destroy it. The BIB builders claim an effortless, OB-like presentation, which isn't quite how I would describe the ones I did, so as always YMMV.
WRT the K-slot or any other shape designed to lower vent Q, you use it if you need it, otherwise it's a waste of time unless it's visible for cosmetic considerations since it reduces loading compared to a circular, square or mildly rectangular one.
GM |
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| GM |
Greets, part deux!
WRT optimum driver position, I've found it to be a function of line length and taper ratio, so 40-something% isn't a 'one size fits all' optimum, especially once you factor in the room's effect.
GM |
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| Scottmoose |
| God knows why they sound like OBs in the LF, but the ones I've built have. And it was about the last thing I expected from them, but there you go. I'm guessing it's partially a function of corner loading, but that really is a guess. |
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| peterbrorsson |
Hi,
I have them shoved up to wall, no corners. In my room these BIB's are the only box speakers that sound ok in the bass.
Not quite OB but darn close!
Cheers
Peter |
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| just a guy |
Ok, so I'm not sure how I missed that VERY recent thread on the iBIBk, although I've seen the term before I never knew what it was. It's certainly a more elegant name than 'upside down BIB with a k slot'. I've read so much about BIB's in so many different places, I thought I had most of it covered, but I guess not.
It is assuring though, that this is a known concept (which means I'm not that stupid), there are working plans and models have already been built.
Never expected to see the info on Dave's page though, maybe I missed a link at Godzilla's page? If it's not there, it should be, along with the rest of the normal BIB info, because that's the one place (other than here) that the BIB enthusiast will visit for sure. |
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