Pioneer B20 in vented boxes... - diyAudio
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Old 1st February 2007, 03:30 PM   #1
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Talking Pioneer B20 in vented boxes...

Hi All,

I ran sims on the Pioneer B20 again. I love experimenting with this driver.

http://www.zillaspeak.com/pioneerb20-3cubox.asp

3 vented boxes all tuned to 34hz and one closed box.

What I want to understand better is why the three different sized vented boxes appear to give best results when tuned to 34hz? Raising the tuning frequency on the smaller box (for example to 40hz) produces too much of an exaggerated bass response that I think will muddy the sound. The vented boxes are tuned below the drivers Fs of 43hz.

I’ve always listened to this driver in a sealed cabinet and like the sound. I feel it offers something different than some of the forward sounding drivers we use around here.

3.0 Box - round port 3 x 3” long (slot 9.25 x 1.5 x 6.64)
2.5 Box - round port 3 x 4.25” long (slot 9.25 x 1.5 x 8.75)
2.0 Box - round port 3 x 6” long (slot 9.25 x 1.0 x 7)

Truly,
Godzilla
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Old 1st February 2007, 04:07 PM   #2
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PS… these boxes offer a nice tidy footprint of 10.75” x 11.25” using standard lumber (1 x 10s and 1 x 12s) and varying heights from tallest to shortest of 58”, 48” and 38”.
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Old 1st February 2007, 06:34 PM   #3
Kensai is offline Kensai  United States
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I've been going round and round with the options for my two primary rigs (office and living room), and I find that I can't really justify the cost of Fostex drivers, and can't really afford the lumber or space for any of the more interesting enclosures.

My wife is finally excited by the sound of something new. She's a music teacher, so you figure she can hear the difference between various bits of gear, but up until the sound of the B20s grabbed her, she apparently never "wanted" to and would always say, "it sounds fine . . . why do you keep messing with it?" I think its that fun, furry sound you attribute to it that got her attention. I like it, too, but I'm actually more impressed with the greater transparency and detail they offer over what I've been using (even though I know you say they're veiled compared to the Fostex). I could appreciate even greater transparency and detail, but I don't think I would like the loss of completely fatigue free listening (I do lots of headphone listening late at night, and my Grado SR80s, while somewhat more detailed, can be noticeably fatiguing after an hour or so). So, anyway, looks like the B20s are going to become staples in my house.

I want to see how they handle in my sealed cabinets in the living room with my B&G Neo3PDRs on the top end. If that goes well, we may need to order another pair. For the office, I'd like to come up with some sort of enclosure that A) I can afford and B) will let me back off on my EQing of the bottom end significantly, if not altogether. Even if I keep these simply fullrange and EQ the top in, they would make good sometimes surrounds for the living room (just run the wires and hide them to where they can be quickly fished out for "special" occassions).

I'm thinking of using 8"x48" lumber for the front/back/top/bottom so I can stain it to match all the rest of the wood in the house, and then use 12"x48" particle board for the sides which I could spray black or maybe some complimentary fleckstone sort of finish. That would give me a volume of around 2.25'^2. I was also thinking of putting the slot rear firing but up at the very top, just above the driver (as I would want the driver at about 42"), assuming I decide to go BR over sealed. If I decide to go sealed, probably need to go smaller, so might use 8" lumber all around for about 1.4'^2 or even 6" sides for just a hair under 1'^2.
The larger one with a bit of space locked out at the bottom for sand or something to weight it would be very close to your sim. I'll just play with it a bit more in WinISD, but eventually, I've got to build something, right?

Kensai
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Old 1st February 2007, 07:58 PM   #4
Kensai is offline Kensai  United States
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Also still thinking about an inverted taper TL using 4' lumber. I've also noticed that this driver likes to be tuned to 34Hz, so I'm wondering if maybe a TL tuned to 34Hz would be best. In a straight line, that would be about 99-100", so the taper needed would be minimal at best. Possibly not even needing the fold board to be angled at all, just placed slightly farther than halfway back in the box. Thoughts?

Kensai
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Old 1st February 2007, 09:06 PM   #5
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Did the Pioneer B20 ever have a blue surround?

I had some drivers that looked similar I used in a
folded voight pipe kind of arangement about 10??
years ago.
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Old 1st February 2007, 09:36 PM   #6
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>>> Did the Pioneer B20 ever have a blue surround?

Yes, they did.

Can someone help me with the tuning freq question please?

Thanks,
Godzilla
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Old 2nd February 2007, 04:49 PM   #7
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Bump...
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Old 2nd February 2007, 05:11 PM   #8
Kensai is offline Kensai  United States
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Larger ports are supposed to sound better than smaller ones, right?

I was playing around with the B20 in WinISD last night and modeled a few enclosures build from 8" and 12" lumber (~2.26 total internal volume) where the port ran the entire length and width of the back wall, the internal volume mating to the vent at the bottom and the vent firing rearward into the room at the top. I don't have any handy way to post those right now, but I found similar results (and yes I was careful to recalc the internal volume taking out the space of the vent and the extra board creating it into consideration). 3"x8"x43.5" vent tuned to around 25 and exhibited little boost but the beginnings of an extended bass shelf crossing 20Hz round -12dB. 2.5"x8"x44" vent tuned to ~30Hz with that characteristic "round" shaped rolloff. 2"x8"x44.5" vent tuned to a little over 35Hz had a bit much boost up around 60Hz than I would think appropriate.

These would look alot like a folded TL internally. Would that change the way they work to where the vented sims are no longer accurate? Would these sound noticeably better than something using a shorter, smaller vent?

Kensai
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Old 2nd February 2007, 09:26 PM   #9
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Quote:
Originally posted by Kensai


can't really afford the lumber or space for any of the more interesting enclosures.


at construction sites, (the trash pile) ,

lumber can be had for free, dress poor, be nice,

and often, more than one can carry, is avalible
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Old 5th February 2007, 02:29 AM   #10
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Not to mention alot of these long TL, TQWT and, ML-TL/tqwt designs have quite a small footprint, and instead are tall and thin. Dont take up much room at all!
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