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Old 25th October 2007, 06:23 AM   #1
Variac is offline Variac  United States
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Default 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
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Old 25th October 2007, 06:28 AM   #2
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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/showd...number=290-045


I then ordered this tweeter as recommended by Mr. Chang:

http://www.partsexpress.com/pe/pshow...TOKEN=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!
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Old 25th October 2007, 11:37 AM   #3
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Quote:
Originally posted by Variac
Here is the Pioneer BOFU 8" driver :

http://www.partsexpress.com/pe/showd...number=290-045

I then ordered this tweeter as recommended by Mr. Chang:

http://www.partsexpress.com/pe/pshow...TOKEN=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!
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.

Click the image to open in full size.

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/showt...92#post1334492
He uses the same drivers as Variac is using and was the first to try that particular tweeter.
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Old 25th October 2007, 02:32 PM   #4
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Is there any probem with mids coming from the rear of the driver and exiting with the BIB or does stuffing take care of that issue?

How is it stuffed?

Does that little tweeter keep up?

Fascinating project.
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Old 25th October 2007, 03:13 PM   #5
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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.
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Old 25th October 2007, 03:27 PM   #6
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Quote:
Originally posted by danielm
Is there any probem with mids coming from the rear of the driver and exiting with the BIB or does stuffing take care of that issue?

How is it stuffed?

Does that little tweeter keep up?

Fascinating project.
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.
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Old 25th October 2007, 05:11 PM   #7
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Also we filled the tapered area above the driver..
For smaller rooms other areas might have to be even more stuffed as the bass can be excessive..

A good thing about all that bass is quite likely they don't have to be all the way into corners.
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Old 25th October 2007, 05:26 PM   #8
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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
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Old 25th October 2007, 05:26 PM   #9
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What thickness of OSB did you use?
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Old 25th October 2007, 05:28 PM   #10
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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
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Old 25th October 2007, 05:39 PM   #11
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Quote:
Originally posted by Variac
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
That's a big room! Look at all the geeks. Wish I could have attended.
The bib's open end must have seen little loading.

What was the other whizzer coned 8" driver in the pointed box?
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Old 25th October 2007, 05:46 PM   #12
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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..
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Old 25th October 2007, 06:58 PM   #13
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Quote:
Originally posted by davidallancole


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.

Since I have too many speakers, I have not built another set with the tweeter and BOFU.

I have the speakers in garage and sometime in near future I will build another set, this time with tweeter right above the 8" in center.

gychang
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Old 25th October 2007, 08:50 PM   #14
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Thanks for the response Gychang and the pictures Variac.
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Old 25th October 2007, 09:42 PM   #15
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Hi Variac,

I am in the process of obtaining the materials to build a pair of these for myself. What can I say, you convinced me.

Cheers!
Russ
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Old 25th October 2007, 10:03 PM   #16
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Does anyone know, is there any european dealer for those drivers, Bofu & tweeter...
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Old 26th October 2007, 07:58 AM   #17
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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.
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Old 26th October 2007, 01:26 PM   #18
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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.
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Old 26th October 2007, 03:07 PM   #19
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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.
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Old 26th October 2007, 04:27 PM   #20
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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





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Old 26th October 2007, 05:38 PM   #21
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Quote:
Originally posted by Scottmoose

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.
I still don't get it, my experience in getting the smoothest response from ~BIB concept, Voigt, ML-horns is that it's much further down the pipe towards the mouth and judging by Tom Danley's various tapped horn products, spot on, so what am I missing?

GM
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Old 26th October 2007, 07:16 PM   #22
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I dunno Greg. I've just run a set of sims on a generic pipe with a CSS 12in driver, just varying the Zdriver location. I did two for each cabinet, one un-damped, the other with 0.25lbs ft^3 in the 1st half of the line. Positions were 0.416, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 & 0.9 total line length. There wasn't much difference between the 1st two, more than that, it gradually worsened.

This is the pipe with the driver at 0.416 line length (damped)
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Old 26th October 2007, 07:20 PM   #23
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And for sake of example (I just pulled it from the variations I did), this is at 0.65 line length with the same damping.

I don't doubt you -you've got more experience in this than I ever have, but this is what I'm getting. Maybe it's me that's doing something wrong (certainly wouldn't be the first time, or the last ).
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Old 26th October 2007, 08:07 PM   #24
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So Variac, how do you have the BIBs placed in the room? Right up in the corners?

I had considered building a set of the flat monolith versions so that they would really hug the wall - become the wall.

Did you place yours right in the corners or somewhere else they sort of "blend in"?
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Old 26th October 2007, 08:26 PM   #25
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Quote:
Originally posted by miccomacho
Does anyone know, is there any european dealer for those drivers, Bofu & tweeter...
The Pioneer Bofu can be got from Spectrumaudio.de, but they are far moer expensive than in the states- 67.5 euro ($97.15, 47.33) compared to $25 (17.40 euro, 12.18). Humph.

Makes it too expensive for me.

Don't know about the tweeter-sorry.

James
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Old 26th October 2007, 08:45 PM   #26
Variac is offline Variac  United States
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I've heard them within a foot of the corners, but in a room that has half of one sidewall open to the outside!!

I've heard them at the show in a room 27'x44' , one in the corner, but the ceiling was very tall.

They worked very well in each. I suspect that they don't need to be in a corner at all in any regular sized room, and I suspect that considerably more damping will need to be used to "house train " them!!

They have always been at a friend's house where we built them and the room open on the side. He said that the tried them indoors in a regular room, and they were too bassy.

So, my understanding is that the first thing to do if they are too bassy is to put more stuffing in the "pinchy" area above the driver. I guess fill it up. Then put the tapering "pennant" of damping hanging in the mouth of the horn. Then put more in the bottom of the box if required, then more in the mouth..

This damping adjustment is pretty fun actually.

We used 1" polyester quilt batting

The ones I took to the show had the pinchy chamber above the driver very loosely filled and the entire diagonal divider covered in 1" batting on the driver side, and the bottom about 3/4 covered with it. Nothing in the horn mouth..

I would put a couple of inches thick behind the driver and cover the bottom just to start..
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Old 26th October 2007, 10:48 PM   #27
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Quote:
Originally posted by jrevillug
The Pioneer Bofu can be got from Spectrumaudio.de, but they are far moer expensive than in the states- 67.5 euro ($97.15, 47.33) compared to $25 (17.40 euro, 12.18). Humph.

Makes it too expensive for me.
Why not import them? They shouldn't get hit with too much in the way of VAT or import duty give that they're not massively expensive. Should still work out cheaper than our daft European prices.
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Old 27th October 2007, 12:02 AM   #28
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Hey guys, make sure that you get the right driver:
http://www.partsexpress.com/pe/showd...number=290-045

the BOFU with the whizzer cone.

Pioneer B20FU20-51FW

I've seen some links are to the one without the whizzer...
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Old 27th October 2007, 12:22 AM   #29
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Default I have a cunning plan...

Import duty on a 30-40 (inc P+P) package should be 0- they waive it if the amount of duty is under 7 and VAT is charged on values of 18 and up. Might be able to get under the VAT limit with one speaker per parcel, but postage would be more, I'm sure.

I might just have to email PE and see what they come up with. Postage at less than 6/driver. Unlikely, but possible.

I'm (sort of) planning to build one of the Chang varients soon(ish). The imported BOFU should work out cheaper than the monacor sp-200x. So I might just do that.

James

P.s. The only problem that I can see with the big BOFU Changs is the size of my room- they would probably be fine for my current uni digs, but a bit big at home, and in future years. Can they ports be damped down to reduce output if they overpower a smaller room?
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Old 27th October 2007, 02:20 AM   #30
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Is a more complete set of T/S parameters for the BOFU than the ones on the PE site?

I scored a set of Nelson's BOFU's + tweeters at Burning Amp. The BIB is too big for my room, so I'm trying to figure out how best to use them. I'm running them in right now in the boxes I used to run in my FR8's - 2.9 ft^3, 4" dia x 4" long port. The bass I'm getting is ridiculous! Ignoring the 50 Hz suckout of this room, they are pretty solid to 40, and have useful output well into the 30's.

My first thought was to try some OB's, but they may wind up going into some even-smaller BR boxes and going to one of my kids with a t-amp of some sort to drive them. (A quick WinISD sim says 1.5 ft^3, tuned to 40 Hz should give 1.5 dB ripple at 80 Hz, -3 dB at 43 Hz, 102 dB with 15 Watts - they should make a pretty decent set of dorm speakers). Colin Pass said to use two of the tweeters per side for best efficiency match - maybe one tweeter forwards, one facing up for ambience and more even power response?

Bill
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Old 27th October 2007, 04:30 AM   #31
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Default Re: I have a cunning plan...

Quote:
Originally posted by jrevillug
Can they ports be damped down to reduce output if they overpower a smaller room?
Yes, 'stick a sock in it' , i.e. stuff the vent area where it exits the driver chamber with fiberglass insulation, open cell foam, or similar.

GM
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Old 27th October 2007, 04:53 AM   #32
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Quote:
Originally posted by lousymusician
Is a more complete set of T/S parameters for the BOFU than the ones on the PE site?

(A quick WinISD sim says 1.5 ft^3, tuned to 40 Hz should give 1.5 dB ripple at 80 Hz, -3 dB at 43 Hz, 102 dB with 15 Watts - they should make a pretty decent set of dorm speakers).

- maybe one tweeter forwards, one facing up for ambience and more even power response?
??? What's missing from the pdf that's needed to design/sim?

FWIW, a prosound alignment (AKA PiAlign) is small and works well for most music in a small room, especially if near/at a corner.

Whatever works for you and/or whoever will be listening to them regularly. I don't like it, much preferring to take out as much of the room reflections as practical, but some swear by it whether front/rear or front/top, so as always YMMV.

GM
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Old 27th October 2007, 05:51 AM   #33
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Actually, my buddy Matt asked the NHT guys at BA to measure one of the pair that he got from Nelson with their Kippel device.. How come no one else thought of that?

I'll ask him to post the info here..
I much prefer the tweeters that I now recommend, from PArts Express - they are only $5 ea. In the past I tried one of the Aiwas that Nelson gave away, but I recessed it a bit in the front baffle so maybe it wasn't a fair test. Still, I'd go with the Parts Express. That's what you heard at Burning Amp..


Mark
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Old 27th October 2007, 09:21 AM   #34
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Default Re: Re: I have a cunning plan...

Quote:
Originally posted by GM


Yes, 'stick a sock in it' , i.e. stuff the vent area where it exits the driver chamber with fiberglass insulation, open cell foam, or similar.

GM
[monty burns]excellent![/monty burns]

Thanks for that.

Now I just have to work out if I can afford the extra space for the curvy fronts.

James
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Old 27th October 2007, 10:21 AM   #35
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Quote:
Originally posted by lousymusician
I scored a set of Nelson's BOFU's + tweeters at Burning Amp. The BIB is too big for my room, so I'm trying to figure out how best to use them. I'm running them in right now in the boxes I used to run in my FR8's - 2.9 ft^3, 4" dia x 4" long port. The bass I'm getting is ridiculous! Ignoring the 50 Hz suckout of this room, they are pretty solid to 40, and have useful output well into the 30's.
Bill
Jeff ('Zilla) has an MLTL on his site that might suit: http://www.zillaspeak.com/pioneerb20-3cubox.asp He didn't mention a Zdriver but ~23in should do.
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Old 27th October 2007, 02:01 PM   #36
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Quote:
Originally posted by GM


??? What's missing from the pdf that's needed to design/sim?

FWIW, a prosound alignment (AKA PiAlign) is small and works well for most music in a small room, especially if near/at a corner.

Whatever works for you and/or whoever will be listening to them regularly. I don't like it, much preferring to take out as much of the room reflections as practical, but some swear by it whether front/rear or front/top, so as always YMMV.

GM

Thanks, GM, I had missed the second page of the PDF!
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Old 27th October 2007, 06:38 PM   #37
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Quote:
stuff the vent area where it exits the driver chamber with fiberglass insulation, open cell foam, or similar.
I misunderstood this before when you mentioned it in the main thread so I will ask more specifically:

Does the extra stuffing go BELOW the driver or ABOVE the driver?
assuming conventional BIB with the exit opening on the top?

Makes sense below the driver as the bass would then have to fight its way through the damping, but I had understood before that you were suggesting stuffing the small chamber above the driver more tightly..

So which is it?


Mark
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Old 27th October 2007, 07:45 PM   #38
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Gees, it just dawned on me that I've got BVRs on the brain and you're asking about BIB damping.

Higher density stuffing at the point down to the driver has the most effect on the pipe's entire gain BW, but will probably increase any perceived room 'boom' due to damping the extreme lows the least, ergo damping the mouth has the most effect on the lows, so adding the equivalent of a high density A/C duct filter inside it is best overall and I assume was one of the reasons why T.C. designed in front/rear ledges inside the mouth of his.

GM
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Old 27th October 2007, 07:57 PM   #39
Variac is offline Variac  United States
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Whew! thanks!
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Old 27th October 2007, 08:02 PM   #40
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Sorry about that, I've been having an increasing number of 'senior moments' lately.
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Old 27th October 2007, 10:05 PM   #41
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IIRC, the ledges TC put in were primarily to support a grill based on a frame of 3/4in particleboard, to stop the cabinet becoming a rubbish bin, though they undoubtedly had the effect you describe Greg. I know that he lined the final part of his original 1354 box, just as Fostex suggested for the design:

'...I notice that by lining the output of the top end of the speaker with an inch thick layer and down about 8" seems to help dampen the ripple effect a little. TC.'
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Old 28th October 2007, 12:04 PM   #42
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Quote:
Originally posted by GM
Sorry about that, I've been having an increasing number of 'senior moments' lately.
Nope- I asked about BVR stuffing. Sorry for the OT confusion.

James
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Old 28th October 2007, 04:17 PM   #43
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OK, thanks for that, but the sad fact remains that if I had any short term memory left I would have remembered there were two distinctly different situations being asked about.

GM
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Old 29th October 2007, 11:14 PM   #44
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Greetings,

Here are the t/s parameters for a B20FU driver as measured by Jack from NHT. There are no units associated with the parameters which introduces some confusion. I've included the standard metric units below in parenthesis with a question mark to indicate a final determination has not yet been made.

Please give these an eyeball and help to confirm my assumed units are correct.

Re = 6.17 ohm
Diameter = 165 mm
DriveLevel = 20 mV

Fs = 37.66 Hz
Qms = 2.544
Qes = .524
Qts = .435
Vas = 96.27 (L?)
Cms = .0015 (m/N?)
Mms = 11.91 (g?)
Mair = 1.77 (g?)
BL = 5.76 (Tm?)
SPL = 91.74 (1w or 2.83v?)
No = .94 (%/100?)
Zmax = 36.12 ohm
Sd = .021382 (m^2?)

- Matt
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Old 1st November 2007, 07:56 AM   #45
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GM

The sad fact still remains that no matter how senior you FEEL, you still rock!

respect mate.

Stroop
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Old 1st November 2007, 08:00 AM   #46
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I suggest using USOBM (ultra-secret open baffle material) for further experiments- It looks very similar to corrugated cardboard..
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Old 1st November 2007, 08:20 PM   #47
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Unfortunately the primary component of the USOBM was two levels down the stairs and I didn't feel like retrieving it.

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Old 1st November 2007, 09:45 PM   #48
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Mark & i have been working on an update of the BOFU BIB plans... they aren't done yet, but they are close enuff to get a wider set of QC & suggestions.

http://p10hifi.net/FAL/downloads/BOF...ans-311007.pdf

dave
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Old 1st November 2007, 10:20 PM   #49
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There is no mention of having the inside of the base having a layer of damping although it is shown and has an arrow to it.

Mark
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Old 2nd November 2007, 01:47 AM   #50
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Quote:
Originally posted by Variac
There is no mention of having the inside of the base having a layer of damping although it is shown and has an arrow to it.

Mark
That paragraph is quite information dense & compact, but it is there "3/a matt of poly, fiberglass, wool felt," The associated number and the damping fill shape clearly indicate where... Any suggestions on expanding it?

dave
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