Pioneer B20 Wide Range Driver + Piezo Revisited.
The worlds cheapest exotic loudspeaker!

January 27, 2006

The Pioneer B20 8” full range driver has been around forever. Asking someone at Parts Express how long this driver’s been out he replied “I’ve been here 11 years and this driver has always been here.”

So it’s been around. At about $25 it’s pretty cheap for a full range driver that’s actually ‘hi fidelity’… not some noise maker. This is an extended range 8” with balls! It’s rated to 37hz and can extend past 15khz but has some problems in it’s upper range that are easily improved. Midrange is smooth, clear and free of typical crossover related problems that plague most speakers available today commercially. It’s rated at 94db per watt but that’s at 1k… overall it’s closer to 90db which is still pretty efficient and it’s an easy 8ohm load. I drive this speaker with the 8 watt Sonic Impact amp and it’s a very good match for a small to mid sized room.

Piezo’s have been around forever too… Built by Motorola, Radio Shack carried them for years at around $10 a piece. Now they are even cheaper at $1.50 each at Parts Express. The cheaper tweeters look the same and sound similar enough. Only a very limited bandwidth is used from about 10khz and up so even the cheaper piezos add the necessary ‘air’ the Pioneer B20 lacks. Adding dammar to the tweeter cone improves things by reducing sibilance but without alteration these tweeters are all about fizzly fun (if you are sensitive to sibilance dammar your piezos).

After experimenting with ported and sealed boxes I concluded sealed provide the best bass to my ears. My first project using .75 cubic foot boxes sounded great but bass was a bit plump. (see WinISD response curve) A 1.3 cubic foot box yields smoother response. Larger ported or sealed boxes reproduce deeper bass but I’d rather limit the bass response somewhat in an attempt to keep the mids and highs as clean as possible… as well as maximizing power handling.

After building the Straight Pipe I realized no matter how tall it may be it’s slim and shallow proportions make it easy to position and tuck near a wall or corner without jutting into the room like other designs (back horns for example). I grew fond of the pipes dimensions and consider it a pretty unobtrusive design. So when I thought about revisiting the Pioneer/Piezo I didn’t let the height of the speaker become an issue. Rather, I decided to take advantage of a taller speaker by positioning the B20 at around ‘ear’ height while seated. This driver sounds dull off axis and I always enjoyed them most toed in towards the listening position.

The Design:

• Sealed 1.3 cubic foot box.
• Pioneer B20 ‘full range’ driver on front
• Piezo on back with 20 ohm resister across and a 1uf (1.33uf will add a more mid-treble and always seemed too hot - .67uf always sounded dull even turned all the way up) capacitor connected to L-pad
• Stuff with acoustisfuff or other

Design to suit your room. I used standard lumber sizes to good effect but you can modify my dimensions to your spec and enjoy similar or even exact performance regardless of the dimensions. In fact, I think I’ve gone pretty extreme with my dimensions of 42”H x 9.75”W x 5.5”D (all inner). The reason why I chose these dimensions was to keep this driver at listening height. The Pioneer B20 needs to at ear level to sound its best. More conventional boxes can be used and placed on stands for the same effect.

I must admit my admiration for the Zu Druid loudspeaker. And while my design is nothing like the Druid, dimensions and components used are totally different as is cabinet type, the overall proportions and look are similar.

Once positioned where you want them dial in the tweeter to taste and you’re done. Basically what you’ve got is an efficient Far East ‘exotic’ wide range paper cone driver topped off by a super fast, light piezoelectric element ‘super tweeter’ matched to your personal taste with the ability to raise or lower treble response as desired.

At an approximate cost of just under $100 (excluding cabinets) any audiophile interested in ‘full range’ drivers can experience the magic. Full range driver fanatics revel in the natural ‘crossover free’ midrange, amazing imaging, non-mechanical sounding beauty of ‘full range’ drivers. The Pioneer B20 is not the best example but it is a relatively inexpensive driver with many qualities of the best currently available. It can make you a believer that simple designs can have benefits over hi-tech, complicated speaker designs selling for triple or quadruple the price. The Pioneer B20 will also allow you to use great sounding lower powered amps (tube or other) to good effect since it’s an easy amplifier load at around 8ohm.

Overall listening impressions: Very positive! It does everything well but isn’t excellent at anything. Basically, it’s more than the sum of its parts. Mellow, easy to listen to sound that doesn’t hit you in the face. You can relax for hours without fatigue. That’s what it’s all about IMO. Compared to other more expensive full range drivers like the Fostex 127e or 168S the Pioneer B20 seems muffled and veiled. Compared to the Tang Band Bamboo driver the B20 sounds more open with larger imaging and life. It’s less detailed and clear compared to the TB. But when all comparisons are put aside this speaker always sounds like the best speaker around. It’s full bodied sound presents music with emotion, life and all the detail you ‘need’ to hear to make that connection to the music and the performers. Midrange (tho muffled compared to Fostex) sounds open and clear.. piano, guitar and brass sound excellent. They have great jump factor. Instruments seem to pop out of know where. Classical music lovers will really enjoy the scale of the orchestra, especially compared to smaller drivers. Jazz sounds perfect on these speakers even tho sax can sound a bit cupped with some recordings. Imaging is about as good as I’ve ever experienced. Everything floats in mid air and can be ghostly at times.

It’s amazing after all these years building and listening to full range drivers that I decided to revisit this driver. I think I became tired with the 4 and 5 inch drivers and needed more gusto in the mid bass and bass. This driver delivers at the expense of midrange clarity but it’s plenty clear and has an interesting sound signature that’s very appealing. I’m sure the designers of this driver knew what they were doing for it to have such longevity (this article also has longevity… my apologies). I’ve been listening to this speaker for days (with my Sonic Impact amp) and never want to leave my office. It’s one of those speakers that makes you want to listen to all your CD’s over and over again.

It’s easy high end at it’s cheapest!

Feel free to contact me if you have any questions regarding this project at godzilla3@hotmail.com

Godzilla