Pioneer 8" BOFU BIB

[GM]

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

 

[Scottmoose]

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)

 

[Scottmoose]

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 ).

 

[Pano]

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"?

 

[jrevillug]

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

 

[Variac]

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..

 

[Scottmoose]

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.

 

[Variac]

Hey guys, make sure that you get the right driver:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-045

the BOFU with the whizzer cone.

Pioneer B20FU20-51FW

I've seen some links are to the one without the whizzer...

 

[jrevillug]

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?

 

[lousymusician]

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

 

[GM]

Re: I have a cunning plan...

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

 

[GM]

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

 

[Variac]

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

 

[jrevillug]

Re: Re: I have a cunning plan...

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

 

[Scottmoose]

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.

 

[lousymusician]

??? 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!

 

[Variac]

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

 

[GM]

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

 

[Variac]

Whew! thanks!

 

[GM]

Sorry about that, I've been having an increasing number of 'senior moments' lately.