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That was it. I was hooked. If I could literally stumble onto something this incredible, imagine what I could achieve if I really focused on building a world-class OB speaker system. Now that I reflect back, it sounds kinda stupid. I was going to focus on building a better flat board.  

The evaluation system for this lengthy process was
• Yamamoto A08-S: This is a 45-based 2wpc SET which I used for driving all widebanders (and tweeters when incorporated). Best sound ever but only 2 watts. One must choose one’s speakers wisely.
• Fisher SA-16, 14wpc p/p EL84 stereo amplifier for driving all on-baffle woofers. This is a  mint little amplifier with quite a stellar sonic reputation in its own right and more than a match for any baffle-fitted woofer used.
• Bent Audio transformer-based passive preamp with optional wireless volume remote: Ultimately transparent. If the source component has the voltage to accommodate it and the A08-S, there is nothing better in my opinion.
• MHDT Havana DAC: So good that Redbook CD outperforms SACDs on my Sony XA777ES.
• Sony XA777ES CD/SACD: For SACD only.
• Locus Nucleus USB Cable: Stunning sonics. At $1,159 it better be great and it is.
• PS Audio PowerPlant 300 with all the updates: For the A08-S and Havana only. 
• Fine silver DIY interconnects throughout: I own many expensive commercial interconnects. None compare in my system.
• Audience AU24 speaker cables throughout: I would have preferred to go DIY as well but the AU24 is simply stunning and somewhat reasonably priced.
• Four-tier Mana amp stand:  A great tunable rack whose company is out of business.
• PC, purpose built and dead silent: Too many details to get into here.
• Foobar/ASIO4ALL aboard the PC’s hard drive: This was my original player which is now surpassed sonically.
• XXHighend: There are many versions. I purchased and loaded the latest which is the best sounding for my system.
• Wireless remote, wireless roller ball mouse (I use this mostly) and wireless keyboard (absolutely essential).
• Monitor hard-wired (on table next to listening chair).
• Professional room tuning throughout.
• 2 x 10-inch horn-loaded subwoofers driven from plate amps: One per corner six feet behind each main speaker.
• Separate 20-amp breaker system for the audio room.
• 5 x 8-foot star-configured copper rods added to code-mandated wiring: Just outside the dedicated listening room and likely a waste of good time and copper.

Lowther DX-4 and PM2MkII
Lowther DX-4 and PM2MkII

On to the meat and potatoes. I started out convinced that If I was going to do this open baffle thing, I had to become a purist of sorts - one baffle with one widebander per side augmented by my trusty subwoofers below 100Hz. After all the JE Labs baffles made the Lowther PM2MKII, Audio Nirvanas or Stepen’s Trusonics etc. all sound better than ever before. Three issues I just could not live with long term were – 1/ the drivers being situated so low to the floor definitely reduced image height to noticeably unnatural levels at times; 2/ if you have a narrower listening room (mine is 13 feet wide) these baffles begin to become visually imposing and distracting; 3/ there just weren’t enough midbass dynamics and snap from a single eight-inch driver in this configuration.

So I built several much taller yet equally wide baffles to mount the widebanders closer at ear level. These baffles were roughly 36 x 60 inches. While the image height was somewhat corrected, the almost palpable airy openness that had so impressed me to begin with was all but gone. At this point I realized that to have my cake and eat it too I would need to increase baffle height and—heaven forbid—add a woofer. Lowther America’s Jon VerHalen was having good luck with a Tone Tubby Alnico hemp-cone 12" guitar driver on his Lowther PM6a OB. He also suggested several potential crossover points for limiting the upper reaches of the Tone Tubby. That's a full-range driver in its own right after all. I decided that I wanted the PM2MkII and TT to gently meet somewhere in the 200-220Hz range. I had the local lumberyard cut ¾" Baltic Birch sheets to spec and then I meticulously constructed the tilt-back legs and cut out the driver holes. After several variations on baffle size, I ended up with roughly the same dimensions Lowther America would soon display with great success at an audio show. 

These baffles were and still are 24 x 41 inches with braces slightly tilting them back. I actually incorporated JE Labs’ legs on all my OBs except done up in Baltic Birch. My widebanders are centered at 31 inches off the floor while the TT woofers are centered at 11 inches. The only crossover is a single rather large 12MH inductor from Parts Express in series with the + speaker terminal. In this baffle I tried many different eight-inch widebanders but wish to limit this discussion to the absolute sonic stand-out, the Lowther PM2MKII. Surprisingly all eight-inchers in my home performed wonderfully. You won’t need a Lowther PM2MKII/PM5a to wring great sound from this simple open baffle configuration but, these particular drivers exceed merely good. They were and are magical in this setup.

Lowther PM2a.
Altec 416.

This is important. If you decide on the Lowther setup, ultimate listenability (not having your head chopped off by their potential harshness) depends on toe-in. Somewhere close to straight ahead allows these baffles to literally disappear while arranging a tapestry of instruments, voices and incidental room sounds in a billowing yet natural pattern beyond the boundaries of my listening room. Dynamic punch and speed are hard to correlate with this relatively modest setup. Such clarity and smoothness. It is still difficult for me to comprehend the sheer power and volume great vocalists can project through this pair of speakers without a hint of distortion and only two watts behind the Lowthers. But, there is a caveat. Toe these Lowther-fitted bafflesin by just a bit too much and that wonderful smooth dynamic clarity becomes painful stridency in the upper midrange through the treble, making them virtually unlistenable with much music. How to know when you’ve got the perfect toe-in? I mean, these OBs are far clearer and more dynamic especially through the mids and highs than what most of us are used to. That along with Lowther’s long reputation for a hot zone should create a more forward tonal balance from the PM5a on these smallish open baffles than our other normal high-end speakers deliver, shouldn't it? Absolutely not. These OBs equipped with big Lowthers are remarkably and easily tunable by simply toeing them until they sound as described, without any stridency or harshness, period. Listen to your B&W Nautilus, Wilsons and Quads. These OBs should be just as easy to enjoy long term when toed in correctly – while sounding far superior.

JE Labs baffles with Fostex FE206 ES-R.
My current Supravox 215-200 EXC field-coil with Altec 416 woofer and RAAL 140-15D tweeter baffles.

So I touched on my long journey over multiple differently sized baffles and plenty of 8-inch widebanders to crown the big Lowther king in a very livable baffle size and shape. Done? No way! The latest rage on the net is all about the superiority of full-range field-coil drivers on open baffles. I ordered myself a pair of easily accessible Supravox 215-2000 EXC eight-inchers. I wanted to compare these field-coil drivers to the fixed magnet Lowther on the same baffles. To do this I decided on baffles 22" wide by 48" tall. I fit these with a single Altec 416 16-ohm woofer incorporating the same Parts Express 12MH Inductors since I wanted a similar 212Hz woofer low pass. All of the web talk points at an inherent superiority of field coil versus fixed magnet drivers. I am however not convinced that field coils really have any sonic advantage over an equally designed and implemented fixed-magnet driver. But this was a great opportunity to observe two respected, comparatively priced drivers with disparate magnet types and see/hear who’d win  Unfortunately things are never that neat and simple. The PM2MKII is equipped with the famous Lowther whizzer while the Supravox 215-2000 EXC is not.  However both are marketed as full-range drivers and therefore the comparison on similar open baffles should be fair.

Supravox open baffle from the side.
Supravox 215-2000EXC field-coil driver from behind.

Very interestingly, the Altec/Supravox combination presents more and more robust bass (although not by much) and pointed directly at my listening chair, sounds a bit denser and weightier through the lower midrange. What a beautifully delineated and palpable soundstage, with lots of meat on the bones of instruments and voices and so damned smooth. Very nice… but where is that lit-from-within excitement of the Lowthers? I have read online accounts by owners of these Supravox baffles claiming absolutely no need for high-frequency augmentation. But I say that once you have lived with a very good widebander incorporating a proper whizzer, the Supravox 215-2000 EXC needs a little help on top. To make a long story shorter, this is where I ended up adding tweeters. I settled on a single capacitor 1st-order capacitor limiting the tweeters to 9kHz and up. I purchased a pair of 2.2uF copper cast Duelunds for the job (these sound remarkable). 

The top-line Fostex super tweeters were fabulous and definitely added the air and life derived from my PM2MKII whizzers. However there seemed to be some musical weight missing at and above the upper midrange where the Fostex comes alive. Enter the RAAL140-15D ribbon mid/tweeter. Pay dirt. The Supravox and RAAL made for a seamless combination. These tweeters added a level of detail from the midrange through the highs that restored the air and spooky palpability which the Lowther brings to instruments and voices. There still is not quite as much treble energy as from the Lowther however. This may very well be because my Supravox when charged to 9 volts are at least 98dB while the RAAL’s sensitivity is fixed at 95B.  Of course I can and have reduced the field coil voltages to 5 and 6 volts for a proper match but then the lit-from-within life that I am trying to improve with these drivers vanishes.

In our home we believe in diversity of drivers and other critters.
Lowther DX-4 and Lowther PM2MkII.

There are good news though. Aleksandar Radisavljevic is in the final phases of designing and building a dipole/open baffle version of my RAAL tweeter. This should add a new dimension to my Supravox baffles that could be downright stunning. As wonderful as the Lowther/TT and Supravox/Altec/RAAL OBs are, their high frequencies only radiate forward. The OB RAAL mid/tweeter should also have increased sensitivity by at least 3dB. I’ll let you know when it happens.

After four years of building a number of different baffles, trying many drivers and fine-tuning passive crossover points, what conclusions have I arrived at? Only one. Anyone reading this can easily and for little cash build a substantially more open, palpable and real-sounding speaker system than they are likely living with at present regardless of cost.

I know, I didn’t specify a definite preference for the Lowther/TT or Supravox/Altec/RAAL open baffles. Here I am a bit at a loss. I am generally notoriously decisive when it comes to realizing and then stating a preference for a piece of audio equipment.  In this case, I love and will keep both of these very different open baffles. I hope that I have sufficiently described their differing sonic characteristics. Obviously the Lowther/TT combination is quite a bit less expensive to build. On the other hand, the upcoming dipole RAAL could make the Supravox OBs even better than they currently are.

There will likely be an addendum to this article in a few months that might further clarify the fixed versus field coil magnet debate. Lowther America has committed to loaning me a pair of their Lowther field coils. This driver will be equipped with a whizzer!

That means that we will have a pair of Lowther PM2MKIIs (PM5a equivalent for OB purposes) with Alnico/Ticonal fixed magnets with whizzers, Supravox 215-2000 EXC field coils without whizzers and finally a pair of Lowther field-coil drivers with whizzers. The above is based on what I have learned during the past four years. I have much more to learn but henceforth will enjoy open baffles exclusively.