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Five Year Quest To Build The Best DIY Open Baffle Wide Band/Full Range Driver Speaker System. Article 1
http://www.6moons.com/audioreviews/ob/ob.html Article 2
http://www.6moons.com/audioreviews/ob2/1.html
Photos of my final and recent wide band/full range driver OB attempt.
http://www.audioasylum.com/forums/hug/messages/15/154898.html
After all of my efforts of the past five years, documented at least in part in the attached articles, I ended up almost back where I started. (Described Later. And It’s a Very Good Thing) But First: Until very recently I got caught up in the supposed sonic superiority of field coil full range/wide band drivers as the basis or heart of my open baffle speaker projects. My Initial/final OB winner after almost five years of trial and much error?
My twenty inch wide by forty seven inch tall baffles fitted with 16 ohm Altec 416 15 inch woofers, four ohm Supravox 215-2000 EXC 8” field coil full range/wide band drivers and RAAL 140-15D dipole Ribbon tweeters with 4 and 8 ohm taps. All Pictured in attached articles. The 416’s are first order crossed over using 16.8 MH Parts Express Toroidal Inductors for a 6 db per octave roll off starting at 135 hertz. The beefy and very rugged Supravox’s were allowed to stretch their quite capable musical legs and run totally unfiltered. Unlike so many (P%$#ys), I power my 215-2000 EXC’s at 12 volts via my big ole Lambda power supply. You can tune these, or any field coil driver through manipulating their input voltage. I found that these Supravox’s came to LIFE and performed much more to the level of the phenomenal Feastrex D9e-II’s when powered at12 volts. Yes the magnet coil cases get hot, but, in the open baffle environment it aint no thang.
Lastly, the tweety things. A very recently developed pair of dipole RAAL 140-15D’s using 4 ohm taps to gain three extra decibels versus the 8 ohm taps (96.7 db efficient with foam pads in place front and back) These beauties are crossed over at 8,500 hertz using a single very large and expensive Duelund cast copper 4.7 UFD capacitor per tweeter. So what about power? First: there are two ten inch horn corner loaded subwoofers powered and crossed at 50 hertz using plate amplifiers with built in crossovers.
Second: The Altec 416’s are powered by a gorgeous mint vintage Fisher SA-16 14 watt per channel Push Pull EL 84 stereo amplifier.
Third: The Supravox’s voice coils are powered by a single First Watt J2 amplifier.
Fourth: The RAAL’s are powered by a single First Watt J2 amplifier. The rest of the system: A Mach2 version of a Mac Mini music server equipped with the most current versions of Itunes and Pure Music. Music stored on an external Oyen 2.5” MiniPro attached via Fire Wire 800 to the MACH2. The USB cable is a custom LA002 connected from the MACH2 to the AYRE QB-9 DAC. My second computer server is a silent custom PC using a portable 1 TB Western Digital hard drive storage device. The WD hard drive is connected to the PC via a USB cable. The PC also connects to the same AYRE QB-9 DAC via an LA002 USB cable. The PC uses the most current version of the J-River Music Player. The preamp is actually a Bent Audio S&B TX102 MKII transformer based Volume attenuator equipped with a remote volume control. This preamplifier (so called) is fitted with more inputs and outputs of balanced and single ended types than I care to describe here. Interconnects and digital cables are all proprietary designs. The speaker cables are all the wonderful and extremely fairly priced Audience AU24E’s. The Ayre QB-9 (24/96) DAC and Mac Mini are plugged into my loaded PS Audio PS 300 power regenerator. Power cords are all Sound String six footers. The main equipment rack is a 4 tier Mana Amp Stand (wonderful but extinct). Power to all equipment is via an electrician installed separate 20 amp spur. I have added five eight foot long copper rods driven in the earth just outside of the audio room in a star configuration. Who knows if this helps in the least? My devoted listening room is 13.5 feet wide by 20 feet long by 8.5 feet tall/high. You can see the relatively extensive, yet strategically placed room tuning in the attached photos.
Now, The Reason Why We Are Here.
Some may remember one of the top ranked speaker systems at The Rocky Mountain Audio Fest several years ago. Most of the posted votes were for a small Open Baffle speaker system displayed by Lowther America. I don’t remember the exact demmentions of the baffles, but they were small. The drivers were one 16 ohm Tone Tubby Alnico Hemp cone woofer and one Lowther PM6a per baffle. The TT’s used a single Parts Express Toroidal 12 MH Inductor in line to 1st order crossover at 212 hertz. At this point I do believe that the PM6a’s were unfiltered. A single large subwoofer was used to augment the bottom end.
This was very early on in my Open Baffle experimentation. I was still experimenting with better methods of making my Lowther PM2MKII’s perform better in the JE Labs squatty baffles. I constructed a bit larger version of the Lowther America RMAF baffles and fitted them with a pair of the same type Tone Tubby woofers and my PM2MKII’s. I was already equipped with the aforementioned dual 10” corner subwoofers. The sound was pure, dynamic as hell and utterly invisibly seamless from the TT’s to the Lowthers. These two drivers were a natural match for one another. I could not tell where one started and the other one ended.
As good as this system sounded, remember my TT OB was fitted with a much more powerful and detailed PM2MKII versus the Lowther America’s PM6a fitted baffles. I absolutely preferred my silver voice coil fitted monster Alnico PM2MKII’s (much like the current PM5a’s) to the comparatively dull PM6a’s. There is just SO much more presence, color, texture and detail with the silver clad big lowthers. However, the smallish baffles left the Tone Tubby, Lowther PM2MKII combination rather enemic in the upper bass and lower midrange. There just was not enough meat on the bones of instruments and voices. Oh, I haven’t even mentioned the truly unfortunate achelees heal of this Lowther based system yet. But then you already know this one. The highs could often become litteraly painful.
By this time I was narrowing down my development to two final DIY Open Baffle systems. The first followed the lead of Lowther Americas lattest iteration of their Lowther baffle. This was a much larger 24 inch wide by 54 inch tall baffle designed to coax the upper bass and lower midrange that was missing from the smaller Lowther baffle system. This baffle also called for a famous and extremely well respected 16 ohm Altec 416 15 inch woofer in place of the 12 inch Tone Tubby’s. A compression tweeter was also added to the top and the Lowther PM5a was crossed over or limited to 10,000 hertz at 12 db per octave.
So, I coppied this design except I replaced the compression driver (which required padding down) with a RAAL 140-15D dipole Ribbon tweeter fitted with a 4 and 8 ohm tap, Amorphous transformer cores and very expensive primary transformer wire windings of a pure silver/gold combination. The RAAL, with it’s foam pads in place were still capable of 96 plus db efficiency which was almost a perfect match for the Lowther PM2MKII’s. I purchased a vintage pair of 16 ohm Altec 416 woofers (98 db). Again almost a perfect volume match for the PM2MKII’s and the RAALs. I used an 18.6 MH Inductor to cross the Altecs’ to the Lowthers at 135 hertz. All that was left was to crossover the Lowthers high end at 10,000 herts, and allow the RAALs to operate down to 8,500 herts prier to filtering them at 6 db per octave with a Duelund 4.7 UFd cast copper capacitor. DONE.
NOW FOR THE OPEN BAFFLE THAT WAS CERTAINLY THE WINNER.
Field coil is were it’s at, right? So, I used a smaller 20 inch wide by 47 inch tall baffle because the Supravox 215-2000 EXC produces substantially more bass than the Lowther and requires a much smaller baffle. However, I used the same RAAL tweeters and 8,500 crossover point using the same Duelund capacitor. I also used a second pair of 16 ohm Altec 416 woofers crossed over at 135 hertz using the same Inductors as the Lowther based OB’s.
I cranked the big Lambda power supply up to 12 volts to extract as much “LIFE” out of the Supravox’s as possible (highly recommended).
One extra bit of information. The baffles, all fifteen of them were made from 13 ply Baltic Birch. However, all of the woofer sections used two layers of BB ply for added support and less vibration. COMPARISONS:
The Supravox system sounded anywhere from dull and lifeless to just about as out of control hot as the Lowthers’ are capable of. It all depends on where you choose to set the power supply. At my favored 12 volts, the system was quite “ALIVE” and very present. However I like my speaker systems right on the edge of too bright at times, so others may prefer them toned down a bit. This system had plenty of natural sounding tactile liquidity throughout the entire midrange region. Sound staging, especially instrument placements within the very intriquait layered field of depth was remarkably melodic and almost hypnotic at times. Instrumental textures and tonality was buttery rich.
OK, what about the obviously, lowly by comparison, Lowther based Open Baffles? Remember, same woofers and same tweeters. Of course now a substantially larger baffle (although designed by me to be quite attractive and unobtrusive in my listening room).
Well, there is immediately that Lowther “MAGIC” in the presence and midrange region that is as spooky an approximation of reality as I have never ever hear from any other speaker of any kind and at any price, accept for the $42,000 Feastrex D9e-II’s. Then there is the continued slight yet obvious mismatch between the bottom of the Lowthers (even in the bigger baffles) and the Altec 416’s. So, I tried crossing the Altecs up at 179 hertz. Yuck! Now the two drivers sounded as though they were at war with each other. Back down to 135 hertz they go. So, what about the high end? I mean We are using a World class tweeter that should mesh seamlessly with the Lowthers. Especially since I am following the tried and true 10,000 hertz Lowther crossover that many have adopted since used in the “BassZillas”.
Well, I am as disappointed and surprised as anyone, but the top end of the Lowther/RAAL combination is just as harsh, bright, and annoying as ever!
Then the LIGHT BULB moment occurred. I was supposed to be doing this project my way, not following the path already carved. I may fail and have wasted five years, but they are my five years.
Yes I know, why not stop with the Supravox OB? After all it was/is pretty darned good. Well that’s true, but there is just something that affects my musical senses when ever I plug in my Lowther Open Baffle system. Something that I just cannot shake or forget. Something that is not just really really good, but totally unique in all my years of listening to speaker systems. So I removed the Altec from the bigger Lowther baffles and constructed a Baltic Birch plate with beveled edges to fit the Tone Tubby’s onto this baffle. I used a single Parts Express 12 MH Inductor to cross the TT’s at 212 hertz 1st order. Wow! Now the bass, mid bass, upper bass, and lower middle midrange sounded as if there was only one driver, the Lowther. Plus, there was dramatically more speed and slapping dynamics . There was also much better bass definition, detail and texture. All this and I absolutely can not tell where the Tone Tubby’s end and the Lowthers’ begin. These Tone Tubby’s are remarkable drivers for this application.
Well, that’s half the battle with the Lowther Open Baffle speaker System. If they are still often too painfully harsh to even listen to, let alone enjoy them due to their upper end bite, then who cares?
Then I remembered what Aleksandar of RAAL told me emphatically about his RAAL 140-15D dipole Ribbon tweeters. “ Don’t be afraid to use them way down into the midrange because they will produce far better midrange than most midrange drivers” And he had the toughest time convincing me that I would not blow the RAALS up.
I purchased a number of pairs of components (foil inductors and Auricaps) of matching value pairs until I heard what I NEVER expected from my big fat Alnico/Ticonal magnet PM2MKII’s. Absolutely NO bite, harshness, or aggressiveness of any kind. 7,700 hertz was the magic point. All of the Lowther stuff that Lowthers are and always have been famous for is still there untouched. Except it sounds so much better because there is nothing irritating in the way any more. Who knew that it was right there in front of me that time and I did not dare try something different than what others had claimed was the way to do things. Remember how seamless the Tone Tubby’s and the Lowthers are in this open baffle? Well, the RAALS are more than seamless. They cohesively meld into the Lowthers but add a dramatic amount and especially quality of mid- highs on up that is mind blowing. These tweeters are spooky detailed yet silky smooth at the same time. And again, I cannot tell where the Lowther ends and the RAAL begin. I listened for hours and hours. I even listened to an entire Eryka Badu (spelling) that my daughter left here years ago. I got carried away and put everything that had a cd case on my hard drive.
POST SCRIPT:
1.) I do not claim to be any better at this than any other forum member.
2.) When choosing a Lowther for this application, my strong recommendation would be: All 15 ohms, PM2a, PM5a, PM2MKII (are available), and I cannot wait to try a PM4a in this application and soon Lowther field coils. It’s phenomenally powerful magnet precludes the PM4a as a direct driver, however when crossing it low enough to Emil orate it’s stridency, then there is a strong possibility that the rest of it’s strengths will shine through and allow the RAAL to handle the top end.
3.) Definitely choose a silver voice coil. Generally the silver coil is known for exasperating the brightness and harshness of the bigger Lowthers. However, the silver coils also add beautiful presence, detail and added sense of life below 7,700 hertz. In this application I believe that the copper coils will sound duller.
4.) Buy the 16 ohm Tone Tubby Alnico Hemp cone 12” woofer. The Red ones. Go to Parts Express for the Toroidal Inductors. 12 MH for 16 ohm crossover at 212 hertz 1st order. You can ad inductors to run in series if you choose a lower crossover point.
5.) You can experiment with multiple combinations of foil inductors and capacitors for the Lowthers as I did. However, I found 7,700 hertz 2nd order crossover to do the trick. .68 ufd, .62 MH
6.) The RAAL 140-15D dipole tweeter can be purchased regular, or added Amorphous transformer core, or the most costly upgrade is the primary transformer wire wound with pure silver/gold wire. I did it all, but am not sure if it makes a huge difference.
7.) IMPORTANT: Invest in the 4.7 UFD Duelund cast copper capacitor if you can. It made a huge difference in the sound of my tweeter.
8.) Make certain that you order your RAAL with 8 and 4 ohm taps. The RAALs with 4 ohm taps is 96 plus db efficient. The Lowthers are all around 97-98 db and the Tone Tubby’s are 96.7.
9.) All of these drivers are naturally close enough in efficiency to work like a charm with no need for intervention.
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