Bofu Bib
This thread is regarding the popular BIB speaker built using the Pioneer full range driver and a tweeter. It really sounds quite good, is full range, and the drivers are about $25 per speaker .
We built a pair out of OSB (oriented strand board ) or as it is sometimes known- flakeboard. With this were able to keep the total cost under $100 a pair. Of course other materials such as plywood
can also be used..
Attached are plans that allow it to be cut from three four by eight sheets.
Mark
This thread is regarding the popular BIB speaker built using the Pioneer full range driver and a tweeter. It really sounds quite good, is full range, and the drivers are about $25 per speaker .
We built a pair out of OSB (oriented strand board ) or as it is sometimes known- flakeboard. With this were able to keep the total cost under $100 a pair. Of course other materials such as plywood
can also be used..
Attached are plans that allow it to be cut from three four by eight sheets.
Mark
Here is the Pioneer BOFU 8" driver
If you ignore the "2" in the model # you can see how it got its name
Part# Pioneer B20FU20-51FW "8" Full Range Driver"
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-045
I then ordered this tweeter as recommended by Mr. Chang:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=275-025&CFID=9638189&CFTOKEN=34028700
Man!! that tweeter is great with the Pioneer!! I tried other values for the crossover cap (1.75uF, 2.25 uF , etc.) and 2.0uF is spot on for my room!
If you ignore the "2" in the model # you can see how it got its name
Part# Pioneer B20FU20-51FW "8" Full Range Driver"
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-045
I then ordered this tweeter as recommended by Mr. Chang:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=275-025&CFID=9638189&CFTOKEN=34028700
Man!! that tweeter is great with the Pioneer!! I tried other values for the crossover cap (1.75uF, 2.25 uF , etc.) and 2.0uF is spot on for my room!
Variac said:
When I built mine I was just a jaw dropping experience. Until I put in the tweeter with 2uF caps, it did not sing...
It is nice to verify this has to be a sleeper combo on the internet. Gurus here has to take the credit, I just followed their instructions, thanks Scott, Dave at Planet 10, Ron, etc.
An externally hosted image should be here but it was not working when we last tested it.
gychang
EDITOR'S NOTE:
This isn't a BIB. It is Mr. Chang's horn which you can find out about here: http://www.diyaudio.com/forums/showthread.php?s=&postid=1334492#post1334492
He uses the same drivers as Variac is using and was the first to try that particular tweeter.
END EDITOR'S NOTE
Hi Variac,
Do you have any pictures of the BIB you build? How does it sound with the OSB board? Is it a pretty sturdy cabinet using the OSB?
Gychang,
You said something about putting the tweeter in line with the center of the B20 at one point in time. Have you done this? Does it sound any better than the tweeter that is off to the side like in your picture?
Thanks guys.
Do you have any pictures of the BIB you build? How does it sound with the OSB board? Is it a pretty sturdy cabinet using the OSB?
Gychang,
You said something about putting the tweeter in line with the center of the B20 at one point in time. Have you done this? Does it sound any better than the tweeter that is off to the side like in your picture?
Thanks guys.
danielm said:
Anything over about 250 - 300Hz should be damped out. The 180 degree bend at the base should help. Typically, the best starting point is to line the front of the sloping internal baffle, and one side-wall from the point to a few inches below the dirver, and also line the internal base.
The very first shot in this clip is the BOFU BIB
http://www.youtube.com/watch?v=4xibbmBc5fI
I think that the OSB could look really nicewith a color stain and clear finish... It has cool 3D look
http://www.youtube.com/watch?v=4xibbmBc5fI
I think that the OSB could look really nicewith a color stain and clear finish... It has cool 3D look
3/4" BUT with NO tongue and groove edges. If you get T&G it won't work with the cutting plan. Cost us about $16 a sheet. OSB seems harder and stiffer than softwood ply. It doesn't make complicated joints well but we just butt glued it and it seems very strong and rigid. Although I've never heard of it being used for speakers before, I like it..
Here's a photo with me and a speaker. The other BIB is MDF with a 6" Fostex, but really should have been used in the smaller room:
Mark
Here's a photo with me and a speaker. The other BIB is MDF with a 6" Fostex, but really should have been used in the smaller room:
Mark
Attachments
We had them up against the wall, and the 8" drivers filled the room!! That's why I think that they will need a bit more damping for smaller rooms. We played a piano track and it was one of the most convincing of the day! I think I am safe in saying that they were very well received by the audience.
Nelson Pass had recommended the BOFU drivers to me a couple of years ago , and in fact sent me this very pair. His remaining pairs were given away at the show. 12 pairs I believe!!!
He got to hear them at the show.. He had used them in a transmission line arrangement before. I don't think that BIB's existed back then..
The charming Brock family (always my partner's in speaker building) and I built them in a short day. They are dead simple to make.
The tapered speakers are Metronomes with Hemp drivers. They were VERY nice and I think would be even nicer in a smaller room..
Nelson Pass had recommended the BOFU drivers to me a couple of years ago , and in fact sent me this very pair. His remaining pairs were given away at the show. 12 pairs I believe!!!
He got to hear them at the show.. He had used them in a transmission line arrangement before. I don't think that BIB's existed back then..
The charming Brock family (always my partner's in speaker building) and I built them in a short day. They are dead simple to make.
The tapered speakers are Metronomes with Hemp drivers. They were VERY nice and I think would be even nicer in a smaller room..
Just a note: i was working thru Variacs plans prepping for a SketchUp of the BOFU BIB. There are a couple dimensional errors. 1 panel too short (by my figuring diagonal should be 66 1/4" long), and 1 too wide (baffle should be the same width as the cabinet)
I've contacted Mark so as to get updated plans posted.
dave.
I've contacted Mark so as to get updated plans posted.
dave.
Attachments
Is the baffle required because of the limited depth of the cabinet at the driver's location?
Has anyone tried a sliding baffle? It looks to me the BIB is a tapped horn. Reflections from the closed end would create peaks and dips in the response (???) which could be tuned to taste by sliding the "tappped" position. I'm just guessing here...
This maybe a question answered in the BIB thread that I overlooked.
Has anyone tried a sliding baffle? It looks to me the BIB is a tapped horn. Reflections from the closed end would create peaks and dips in the response (???) which could be tuned to taste by sliding the "tappped" position. I'm just guessing here...
This maybe a question answered in the BIB thread that I overlooked.
It's a pipe horn with the driver 'tapped' in at a specific distance along the flare path -the phrase recently seems to have been hijacked to refer to the Tom Danley style of cabinet with the driver mounted through the internal baffle but according to GM (and it makes sense, when you think about it) applies to any horn with the driver positioned some distance from the throat.
Yes, harmonic resonances can be supressed by tailoring the Zdriver position (distance from the throat at which the driver is tapped into the horn). Typically for an open-ended BIB run full-range, the best compromise is 0.2 - 0.217 line length. The ~optimal is around the 0.416 line length Martin King found for a 1:10 taper line, but that's only useful for high Fs drivers, with a relatively short path-length (& therefore work best as inverted types coupled to the floor), or bass-horns (see attached).
If they're positioned properly in-room (as corner horns they require the room boundaries to complete the horn flare & provide the correct acoustic-impedance match at the terminus) and with a good damping strategy, they don't exhibit much more ripple than other cabinets & kill most stone-dead in the LF.
Yes, harmonic resonances can be supressed by tailoring the Zdriver position (distance from the throat at which the driver is tapped into the horn). Typically for an open-ended BIB run full-range, the best compromise is 0.2 - 0.217 line length. The ~optimal is around the 0.416 line length Martin King found for a 1:10 taper line, but that's only useful for high Fs drivers, with a relatively short path-length (& therefore work best as inverted types coupled to the floor), or bass-horns (see attached).
If they're positioned properly in-room (as corner horns they require the room boundaries to complete the horn flare & provide the correct acoustic-impedance match at the terminus) and with a good damping strategy, they don't exhibit much more ripple than other cabinets & kill most stone-dead in the LF.
Attachments
By "baffle" we will mean the small "extra" baffle on the front , doublling the thickness near the driver..
-Mounting the baffle so that there are slots for adjustments in height or various holes to try is a good idea and one that I considered, but haven't investigated. The hole in the front of the box would need to be elongated vertically but I see no problem as long as it doesn't get exposed when the baffle is moved all the way up or down.. We're probably talking about 3 inches at most here.
-I don't know if the baffle is required to give clearance for the back of the driver, as I found that there was enough wood to make the baffle and felt that a little extra clearance behind the driver could only be good.
-We made the baffle attached with only 4 screws (6 screws if it is longer) so that it was easy to remove for work on the crossover cap or adjusting the stuffing.. That is a good idea, as removing the driver often is just asking for a screwdriver through the cone. Possibly there should be some sort of gasket material behind the baffle then, and glueing it eventually would be the most rigid.
-The baffle could also be wider than the cabinet if one wants to experiment with various sizes as a suprabaffle to adjust response. Careful trials might well pay off. May be room dependent also.
As it is, I felt that there was no problem requiring correction, but its possible that it can be improved. In order to have material for more different baffle widths, one could use a half as tall baffle. Also maybe use the base material. I showed the base, as it is important here in earthquake country! For supra baffles, taped on cardboard is always my first try..
-Mounting the tweeter on a tube in the center of the BOFU after removing the dustcap is an option that I find appealing to try. I doubt that two strands of twisted magnet wire to the tweeter in front of the large driver will have an effect on the sound, and the coherence of a coax might be an improvement. OR, the resonances might make it worse. At $20-25 each one can risk a bit of experimentation on the driver.
My main credo is to keep the mods cheap as that is the theme I have followed with this speaker. I wouldn't be suprised if many end up covered with veneer in the end, as they really are a pleasant speaker!
Please post your findings here for consideration by others..
Mark
-Mounting the baffle so that there are slots for adjustments in height or various holes to try is a good idea and one that I considered, but haven't investigated. The hole in the front of the box would need to be elongated vertically but I see no problem as long as it doesn't get exposed when the baffle is moved all the way up or down.. We're probably talking about 3 inches at most here.
-I don't know if the baffle is required to give clearance for the back of the driver, as I found that there was enough wood to make the baffle and felt that a little extra clearance behind the driver could only be good.
-We made the baffle attached with only 4 screws (6 screws if it is longer) so that it was easy to remove for work on the crossover cap or adjusting the stuffing.. That is a good idea, as removing the driver often is just asking for a screwdriver through the cone. Possibly there should be some sort of gasket material behind the baffle then, and glueing it eventually would be the most rigid.
-The baffle could also be wider than the cabinet if one wants to experiment with various sizes as a suprabaffle to adjust response. Careful trials might well pay off. May be room dependent also.
As it is, I felt that there was no problem requiring correction, but its possible that it can be improved. In order to have material for more different baffle widths, one could use a half as tall baffle. Also maybe use the base material. I showed the base, as it is important here in earthquake country! For supra baffles, taped on cardboard is always my first try..
-Mounting the tweeter on a tube in the center of the BOFU after removing the dustcap is an option that I find appealing to try. I doubt that two strands of twisted magnet wire to the tweeter in front of the large driver will have an effect on the sound, and the coherence of a coax might be an improvement. OR, the resonances might make it worse. At $20-25 each one can risk a bit of experimentation on the driver.
My main credo is to keep the mods cheap as that is the theme I have followed with this speaker. I wouldn't be suprised if many end up covered with veneer in the end, as they really are a pleasant speaker!
Please post your findings here for consideration by others..
Mark
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