The Pioneer / Piezo Loudspeaker By Godzilla Hello to all of my full-range brothers and sisters. Here is a project that is very cost effective, fun to build and sounds great. It uses the Pioneer B20FU20-51FW wide range driver and a Radio Shack 40-1218 piezo tweeter. It is a very simple design. A sealed cabinet with an internal volume of .75 cubic feet. A subwoofer is not mandatory in small to medium sized rooms but recommended for best bass performance. More information on the Pioneer 8 inch full range driver is available at El Craigo's website. The motivation: After building speaker kits for over ten years, I became frustrated with conventional designs. Crossovers were always a challenge. In fact, several of my designs used crossovers that cost more than the drivers and the cabinet combined. Listening fatigue was the main reason I continued building. I was always trying to reduce this phenomenon and get closer to the music! I found James’ site by searching for ‘speakers that work well with tube amps’. One URL led to another and there it was, the Full Range Driver Forum – yeah! It seemed others were experiencing similar challenges and frustrations. They were all talking and experimenting (and still are, thankfully) and discussing ways to get closer to the music. I tried some Radio Shack 40-1197’s in cheap little boxes as a first project and was hooked on ‘full range’ sound. Comparing these very inexpensive speakers to my very expensive ones was a revelation. How could they sound so similar? Ultimately the cheaper speakers could not handle very high volume levels, nor could they reveal all of the tiny little details on each CD, but I still preferred them. These speakers still could become fatiguing after long sessions, but others on the Forum were successfully finding ways to reduce this. These speakers were moved into my office and have been there for quite some time. I listen to them everyday. The next project was the beloved 40-1354 in a larger ported box, similar to the Hawaii speaker by Herbert Jeschke. This was an improvement over the 1197’s IMO but did not make a large enough impression on me to stop experimenting. The drivers were inexpensive and easily smuggled into home or office for tweaking. I began to look into Lowther, Fostex and Triangle. My hesitation was that I was looking at expensive drivers again and unsure of the results. So I continued looking into more affordable full range drivers. Some folks (GM was one, I remember) had been experimenting with the Pioneer B20’s/Radio Shack 1218’s and getting pretty good results. Thanks GM, your comments on these drivers inspired me to further explore, listen and experiment. Others (Craig Schmidt) had mixed results. Everyone has different tastes and opinions, I thought, and I decided to buy the Pioneers and give them a listen of my own. The Pioneer B20FU20-51FW This $25 driver appeared well made with its large heavy magnet and a durable cardboard cone. I stuck them into an old cabinet to hear the sound they produced. The sound was dull and muted. Highs were very soft in volume level. I thought, "This isn’t full range." Listening directly on axis and letting the drivers break in for a few days changed this somewhat. I was beginning to get accustomed to the sound. The midrange and bass were very good but the highs were still lacking even after break in. One thing that hooked me on this driver was the imaging. Vocals sounded very natural and floated in space. When Ella Fitzgerald’s orchestra swelled to full volume, it swelled without destroying her voice. Holly Cole was in the room with me whispering into my ear, whoa! Diana Krall was jamming, her piano sounded natural and she was much less sibilant than ever before. I could listen to Steely Dan again without getting a headache. Now, how do I ‘fix’ that top end? How can I add a little sparkle without ruining everything else? The Radio Shack 40-1218 Piezo In the spirit of ‘cheap’ I went to Radio Shack and picked up a paper cone tweeter and a piezo horn tweeter. Hooked one to each speaker and began to tweak. I think I was rooting for the paper cone. I really wanted to have an ‘all paper’ speaker system. But the paper cone didn’t sparkle, didn’t ‘enhance’ the sound of the Pioneer. It always sounded ‘in the way’. The piezo ($10) was not much better at first. It had a very distinctive sound which can become irritating at times – very spitty and lispy, very fatiguing. But there was something interesting about the sound. It added liveliness to the presentation, which I liked. After much experimentation, I came up with a simple circuit that added the sparkle I was looking for without the fatigue. After weeks of experimentation, listening and discussion on the forum, I settled on the following ‘crossover’ circuit: 8 ohm resistor across the piezo terminals (Radio Shack part # 271-120, $1.49 each) 0.47 uf capacitor wired in series (Hovland, $1.50 each from Madisound) I also experimented with damar on the piezo’s cone element. In my opinion, this added refinement to the sound and reduced sibilance almost completely to my ears. Remove the three screws from the back of the piezo Coat the paper cone with one coat of damar Remove ‘pooling’ of damar with a tissue Let dry overnight Reattach horn I also applied rope caulk to the back and sides of the horn to deaden any plastic sound. The Cabinet Just an old sealed box found in Grandma’s basement. I found a few and experimented with the .25 and .75 cubic foot. In the end I preferred the .75 because of the slightly extended bass. But the .25 gave similar results. With my subwoofer the difference was minimal. Either way, this speaker provides surprisingly good bass. Not analytic or dry, but rather fun and bouncy. I tried porting the box but found sealed kept the bass tightest. Lightly stuffed with fiberglass about half full seemed to work fine. The System My system consists of tubes! I love tubes. If you are searching for fatigue free listening I think you will enjoy them, too. Cary SLA70MkII, 35 watts per channel amp, Cary SLP94 preamp and Anthem CD1 tube CD player. This replaced an Aragon 2001MkII amp, 100 watts per channel and an Adcom preamp (which was then replaced with a Conrad Johnson PV6 and then a Cary SLP30, each an upgrade over the previous) and a dbx CD player (which was later replaced with a Sony – which I hated – and a Denon – which I hated and finally the Anthem). The Cary amp and preamp have been with me around three years. The CD player, around two. As you can see, everything has been ‘baby proofed’ high up in the wall unit. Don’t want my kids to get burned by the tubes. The speakers, while not a perfect fit, sit at the very top. Obviously, placement is not optimal, but it sounds good anyway. (BTW, this is the same location used for my 1354’s and 1197’s.) The Sound In my opinion, these speakers sound good regardless of price. They have a nicely balanced warm sound. Nice bouncy bass, smooth midrange and nicely detailed treble. Everything gels. Vocals, sax, vibes, strings, woodwinds and guitar are reproduced beautifully. This system adds up to more than the sum of its relatively modest parts! Nothing sticks out and everything sounds natural without fatigue. As mentioned above, Ella, Holly Cole and Diana Krall, are some of my favorites. The list changes weekly. Other favorites of mine include: Stan Getz, Michel Camilo, Joao Gilberto, James Taylor, Billy Joel, The Ally McBeal CD’s, Cowboy Junkies, Tommy Flanigan, Milt Jackson, etc. The list continues to grow. It appears Jazz and Pop are my preferences, although I do enjoy and listen to all types of music. The speakers were tuned by ear mainly with these artists. Once the ‘crossover’ was to my liking I found myself listening for hours, enjoying. I feel the Pioneer/Piezo is particularly well suited for this type of music. I have two reservations about this system. The first is it’s too cheap to sound this good. The parts are inexpensive so I want to spend more. The problem is that I don’t know if I will actually get more enjoyment out of a system with more expensive parts (Been there, done that!) I think this is a tribute to ‘wide range’ driver designs. Once you hear the potential, you want more, more, more! The second is ultimate resolution. This is not the best system for resolving every last detail. Let me try to explain. Although I truly enjoy listening to music played thru this speaker, sometimes I feel I am not getting all the notes. Other systems seem to have more going on. The Pioneer/Piezo sounds a bit relaxed in comparison. Dark and mellow with a twinkly top end. Of course all of the notes are there, just that they don’t call as much attention to themselves. This is the first speaker I have built that is truly enjoyable and relaxing to listen to. I have rediscovered many of my favorite CD’s. Some that sounded grainy are now easy on my ears. I never dread turning on the stereo anymore and I can listen for long periods without fatigue. Nuf said. Top