Having ordered a pair of 40-1354's, I figured I'd build some BiB's. However, I was left wondering: What's up with the frequency response?
http://www.zillaspeak.com/BIB-RadioShack.asp
There's about +/-10db flying around in there.
Having mucked around in the EDGE, this looks like what happens when you have a long, thin baffle. What if a larger baffle were to be affixed on the front of the speaker around the driver, or some backwards-facing "wings"?
http://www.zillaspeak.com/BIB-RadioShack.asp
There's about +/-10db flying around in there.
Having mucked around in the EDGE, this looks like what happens when you have a long, thin baffle. What if a larger baffle were to be affixed on the front of the speaker around the driver, or some backwards-facing "wings"?
If you read some of the other BIB posts, you'll see that I've gone into this in some detail a few times. Still, no harm in doing it (yet) again, especiallyu as the various threads are getting to frightening lengths... 😉
The response graphs that GM and I posted on the Zilla pages and elsewhere, are 1/2 space graphs. The BIB is specifically intended for 1/8 space loading, i.e corner placement (although you can get away with just a rear wall), because it actually uses the room as part of the cabinet. The response graphs look unpleasent because the effect of the room is not taken into account in the software (yet).
What does the room do? Well, it increases the apparant terminus size by a factor of 8 due to the 3 reflective boundary conditions of ceiling, and two side-walls that are 'seen' by it (remember: the open top of the BIB is a terminus: the mouth is actually formed by a combination of this, and the 3 room boundaries), and does the same for the resistive portion of the acoustic impedece. This, as Martin points out, has several consequences. It allows for far more efficient transfer of low frequencies into the room, attenuating standing waves in the line, killing 70 - 80% of the ripple you see in the response at anything much over about 250Hz. The shape is also very directional as frequency rises, which helps still more, while the more or less abrupt flare outside the terminus will cause a considerable drop in pressure, reducing any peaking at Fc.
None of this is anything to do with room-gain or baffle-step loss etc. They don't need or benefit from a circuit as they are intended to go into corners, and also the wide pass-band of the horn, and the considerable gain it provides negates losses. A podular baffle a la Terry Cain can, however, assist with wave-launch and with scattering reflections from the surround. Useful addition, but not essential.
Overall, these are not monitor flat enclosures: that's not a design priority. They do have more ripple than a reflex or MLTL. However, their response is nothing like as bad as the simulations suggest, and no worse than quite a few other well regarded horn cabinets I could mention. That's the down side of these big old traditional corner horns. The up-side is that they are extremely easy to build, look very elegant, allow drivers to breath like little else you'll come across, and their party-piece. Bass. Enough of it to blow you out of your chair, with a distinct lack of boom. Which is nice.
Hope this helps
Scott
The response graphs that GM and I posted on the Zilla pages and elsewhere, are 1/2 space graphs. The BIB is specifically intended for 1/8 space loading, i.e corner placement (although you can get away with just a rear wall), because it actually uses the room as part of the cabinet. The response graphs look unpleasent because the effect of the room is not taken into account in the software (yet).
What does the room do? Well, it increases the apparant terminus size by a factor of 8 due to the 3 reflective boundary conditions of ceiling, and two side-walls that are 'seen' by it (remember: the open top of the BIB is a terminus: the mouth is actually formed by a combination of this, and the 3 room boundaries), and does the same for the resistive portion of the acoustic impedece. This, as Martin points out, has several consequences. It allows for far more efficient transfer of low frequencies into the room, attenuating standing waves in the line, killing 70 - 80% of the ripple you see in the response at anything much over about 250Hz. The shape is also very directional as frequency rises, which helps still more, while the more or less abrupt flare outside the terminus will cause a considerable drop in pressure, reducing any peaking at Fc.
None of this is anything to do with room-gain or baffle-step loss etc. They don't need or benefit from a circuit as they are intended to go into corners, and also the wide pass-band of the horn, and the considerable gain it provides negates losses. A podular baffle a la Terry Cain can, however, assist with wave-launch and with scattering reflections from the surround. Useful addition, but not essential.
Overall, these are not monitor flat enclosures: that's not a design priority. They do have more ripple than a reflex or MLTL. However, their response is nothing like as bad as the simulations suggest, and no worse than quite a few other well regarded horn cabinets I could mention. That's the down side of these big old traditional corner horns. The up-side is that they are extremely easy to build, look very elegant, allow drivers to breath like little else you'll come across, and their party-piece. Bass. Enough of it to blow you out of your chair, with a distinct lack of boom. Which is nice.
Hope this helps
Scott
We have our finer, more cultured sides, in between saying 'oh ar' and biting the heads off whippets. 😉
Actually, I shouldn't say such things, as I happen to own a whippet (Dana) and love her dearly.
Actually, I shouldn't say such things, as I happen to own a whippet (Dana) and love her dearly.
Any reason SPL graphs for corner placements are not given? I'm kind of curious as to the results.
Martin King's (quarter-wave.com) MathCad models (used by Scottmoose and GM to simulate the BIBs posted at zillaspeak.com) can't simulate corner placement or 1/8 space *yet* (here's hoping that's coming from Martin soon!).
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I was skeptical about the claims for the BIB design but was convinced enough to try it after reading numerous postings by Scottmoose, GM and others. Now I'm converted. I'm in the process of completing a BIB for Fostex FE126Es and played with the rough cabs last night. To put it mildly I am stunned by the sound particularly the richness of the bass.
The BIB cabs are very easy to put together but tall. I managed to find "utility shelves" (made of chip board) on sale at a local home center to use. Consequently the cabs have cost less less than $8 ea (CAN) counting the boards, pillow stuffing, glue and screws (but not finish)!
The dimensions of the lumber forced me to alter a few dimensions from the FE126E BIB design posted. I ended up with a mouth of approximately 60in2 and line length about 96.85in instead of the 63in2 and 97in posted -- thus it was very helpful to have King's models to check the driver placement (I ended up moving it up slightly from posted).
I'm still playing with stuffing and lave not yet glued one side onto each cab yet. So far I've found that adding light stuffing from the behind the driver up to the closed end (as recommended by Scottmoose) provides the best sound so far.
They work. Oh yes indeed, they work. Traditional designs still have their place, especially as we can refine them now with tools (software or otherwise) unavailable 70-odd years ago when they first emerged. Pity they were lost for so long. Glad you like them. 😀
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