Pioneer B20FU20 application thread

[Mayuri]

Hello everyone!

I've been looking the Pioneer BOFU drivers from PE with gleaming eyes for over an year now, and have finally decided to order them, even with the crazy postage fees they put in packages coming from US to EU.

I am thinking I might get an inexpensive HT upgrade from them, or just put them in large BIBs for casual listening. But BIB is way too large for my living room, since it's only 3m x 4m. What kind of small-ish enclosures would you guys recommend for these drivers?

Best Regards,
Simo

 

[IG81]

I never tried them myself and am intrigued as well. What would be helpful to know to start with is, do the published T/S parameters hold up to measurement? I've been had before with drivers far enough form specs to make them unsuitable for the desired enclosure.

IG

 

[Godzilla]

http://www.zillaaudio.com/pioneerb20-piezo.htm

http://www.zillaaudio.com/pioneerb20-3cubox.htm

Single Driver Website

I think you can use the BOFU in a small sealed cabinet with very good results. But add a tweeter.

Zilla

 

[GM]

......do the published T/S parameters hold up to measurement?

Well, this driver's specs has changed over the decades as has how folks measure them and my 10+ yr old drivers spec a larger cab than the PE's by about 13%, so you could always 'pump up' PE's for a bit if you're worried about it being too small....... Regardless, there's been enough different alignments built using PE's over quite a few years now with nary a comment about them AFAIK, so unless something has changed recently that I'm not aware of.........

Anyway, a 3 x 4 m room is only slightly larger than the room I'm sitting in, so plenty big enough for some good size MLTLs if not full of furniture/fireplace/whatever, so my usual suggestion for drivers that need a larger than average cab to go low is to build the biggest cabs that can be tolerated and tune it in-room.

Nelson Pass's TL has been getting some good reviews lately and sealed, BR, MLTL are easy enough to calculate, so what's the largest cab that can be tolerated?

GM

 

[Mayuri]

I think that when looking at bass extension and cabinet size, a small sealed one would be best for me (I also happen to like sealed cabinets sound). First of all, I have a quality sub that can take over at about 70-80 Hz. Second, the listening room is my living room, so there's a quite of bit of furniture, so a huge enclosure would be cumbersome.

How directional are these drivers, is there any sense in making a 5 speaker HT with these or should I look at some other drivers for the upgrade. I'm now using 4 Cyburgs Sticks and a matching center speaker, so can this project be an in sound quality?

 

[norman bates]

um, very directional past 5khz (like 2-3 people wide at 10'), but phase plug may (should ?) help.

Norman

 

[Ed LaFontaine]

published T/S parameters hold up to measurement?

I have 2 B20FU20-51W's that I bought at PE's most recent tent sale. One appears to be in "like new" condition. The other is a bit worn and was subject to someone's ill-fated experiments. Below is a list of parameters. PE's data is dated January, 2002. My "a" data is from the experienced driver. My "b" data is from the "like new". They were measured this morning on a WT3.

*** Fs**** Re****Lvc****Qes****Qms
PE *43. ***6.28***1.21***.62****3.02
a **40.4 **6.23***1.40***.59****2.64
b **40.4 **6.13***1.19***.60****2.62

 

[Ed LaFontaine]

The above response plot is for the BOFU in a MLTL. The enclosure internal dimensions are 42" High, 9.5" Wide and 12" Deep. The driver is centered 6" down from the top. A port tube of 3" diameter X 6" long is centered 4" from the bottom of the enclosure.
The slope of the response was chosen to offset some of the "boom" resulting from room gain.
A simulation was done to compare with a tapered TL alignment.
This Mass Loaded alignment is essentially free from the ripple associated with the tapered alignment, allows tuning of the bass slope,...and is easier to build, particularly if you can only accept a folded taper.
As it may not be easy to see, the response is @~91 dB just below 100Hz. The "knee" of the response is -6 dB @ ~34 Hz.

 

[GM]

How directional are these drivers, is there any sense in making a 5 speaker HT with these or should I look at some other drivers for the upgrade. I'm now using 4 Cyburgs Sticks and a matching center speaker, so can this project be an in sound quality?

The B20 is a great 'bang for buck' driver wherever it's relatively dirt cheap, with a very lively, toe-tapping presentation that works surprisingly well in a HT due to the greater directivity being normally required, but as a wide BW 'upgrade' with maybe just a super-tweeter you're going to have to start with a pretty low expectation by today's lofty standards.

For your app then, the B20 would be a good choice for filling in the Cyburgs's anemic first decade and converting it to a sealed or even OB, mids/tweeter alignment, but I imagine there's better, competitively priced choices available to you locally for this type of upgrade.

GM

 

[GM]

I have 2 B20FU20-51W's that I bought at PE's most recent tent sale.

Thanks, even better than I'd hoped for!

GM

 

[Mayuri]

Sorry, I accidently left a word out of my previous post. This is how it should have went:

"I'm now using 4 Cyburgs Sticks and a matching center speaker, so can this project be an upgrade in sound quality?"

With this I meant that do I get a real upgrade from the B20 + supertweeter combo replacing the Cyburgs Sticks?

 

[Ed LaFontaine]

the response is @~91 dB just below 100Hz. The "knee" of the response is -6 dB @ ~34 Hz.

My bad ...the knee is -6 dB @ ~24 Hz

 

[GM]

With this I meant that do I get a real upgrade from the B20 + supertweeter combo replacing the Cyburgs Sticks?

It probably would for someone like me that's more interested in the thrill of a movie soundtrack than in absolute clarity if I can't have both that I typically can only get in a horn loaded system, but in this forum it's primarily about getting a HIFI version in a very compact package of what the producer intended, so if these Sticks please you overall, then probably not an upgrade, just different.

GM

 

[Mayuri]

Well, it sounds like a good speaker for me. Kinda reminds me of Tivoli audio products actually, the exact speaker output graph bounces around like crazy but still they sound good.

I also like to immerse in movies and music, I have clear analytical desktop speakers with a Tripath amp if I want absolute clarity. I like the Sticks a lot, they're actually my first real HT setup, but I'd like to try something different, and the BOFUs seem to offer just that.

 

[badman]

My bad ...the knee is -6 dB @ ~24 Hz

That presumes the starting freq to be at 10Hz... 34 would seem more likely.

They can dig deep though, which is almost nonexistent for fullrangers. The pass TLs don't really need a sub (and that is almost nonexistent for speakers in general)

 

[Mayuri]

I think I'm going to go for this combo:

1 ft^3 sealed enclosure with the B20 and this Dayton tweeter:

Dayton ND16FA-6 5/8" Neodymium Dome Tweeter | Parts-Express.com

I figured I'd put a 2.7uF capacitator in series with the tweeter for the crossover, but do I need a L-pad for it too? I'm planning to do 5 similar speakers for HT.

Also a more important question:

I know people have modded these drivers, but what would you guys recommend for HT use? Phase plugs might be one for good off-axis response, and maybe the PVA glue coating, but what else?

 

[GM]

At a glance, it doesn't appear to need one.

With a super-tweeter, I've just kneaded the whizzer to work the starch out of it to damp its bell modes, damped the dust cap and done what's become known as the $0.98 tweak: Modifications

GM

 

[Mayuri]

Had to update this thread with sad news. 5 of the Pioneers is dirt cheap with only about 100$. The problems is that the shipping costs are over 100$, and the customs in here would tax me for about 50$ on this purchase. So it would leave the total cost for one driver to be about 50$, which seems a bit too high for me.

But nevertheless, I thank everyone for their advices and time spend on my thread!

 

[GM]

Ouch! Not sure they're worth that much unless you've no better option(s) at this or a lower price.

GM

 

[Racket Scientist]

Just looking over this driver and thinking it might make a great little one speaker small stage monitor driver for PA use.