Warning…long post.
The title of this thread is a spoof on the speaker brand Pure Audio Project. I heard their OB speakers at Axpona last year and liked them.
http://www.pureaudioproject.com/trio15-open-baffle-speakers-pureaudioproject/Then I heard ProggRob’s Hawthorne Trios with his UFO Zen and felt the quality bass they produced was something I wanted. Then I heard Randy’s OBs at the fest with a Augie helper
http://www.caintuckaudio.com/ http://www.hawthorneaudio.com/catalogs/index.php?main_page=product_info&cPath=3&... and liked how musical it was. Finally, ProggRob came over for a CDApS session and gave his honest opinion that bass was not a strength of my system. He was right and that pushed me over the point of no return.
So, I had a little mad money at the end of the year and bought a single Augie from Hawthorne Audio along with a Dayton Audio 250W plate amp. I figured if I liked it well enough I would get a nice baffle from Randy and be all set. Little did I know…
Well, I got the Augie, stuck it in a 23.5W X 22H MDF baffle made from leftover wood , hooked it up and it was another wow moment for me - like when I heard my Rachael on a PS Audio power conditioner or when I got the Uptone Audio Regen. But while it was great, I immediately wanted more.
So, I blew up my budget and ordered another Augie. Stuck it in another MDF baffle made from leftover wood and set it up running off the plate amp in dual mono. More goodness as the rabbit hole began to open wider and wider.
Then I thought why not get a couple Besty drivers. Randy’s OBs at the Fest sounded good. Those don’t cost much, right? But then I did some research, exchanged notes with Randy and Maddog07 and started weighing out my options. Betsy? Audio Nirvana? Or the Tang Band W8 1808 which was used in the Pure Audio Project?
I finally decided to take a chance on the Tang Band. I had used a smaller Tang Band in the past in a simple OB I built pre-Decware days. I figured that the Pure Audio speakers had received good reviews and they were at the core of that sound. Steve also had a favorable opinion of them when he was looking for an OB driver. Finally, I had a 20% off coupon from Parts Express so Tang Band it was.
I got the Tang Bands and cut some 23.5W X 13.5H baffles out of old wood and literally tacked them to the Augie MDF baffles with some leftover furring strip and some drywall screws.
The Tang Bands literally sounded like I was listening to music through a telephone hand set. But, I was emotionally prepared for break in time, so I let them play for 24 hours. Hmmmm…better. Another 24 hours. Better still. Another day or so and I think we were there.
I played with the crossover frequency on the plate amp. Originally, about 50hz. Then full on (180hz), then backed it off to about 70hz. That seemed about right. Then I started playing with volume. I started out with it about ¾. But after much fiddling, I ended up about only ¼.
Where these Augies help the most is in helping you feel the low end. They provide a nice tight foundation. If you have the crossover set too high, you can definitely hear the nice tight bass, but it starts to mess up and cloud the mid-range. Same thing with volume. It’s cool to rattle your walls, but it can overwhelm everything.
Something was still amiss. Imaging seems off, so I decided to try an old honker Class D stereo amp that I had from pre-Decware days. I pulled it out of the closet, and hooked it up to the line out from the plate amp, and rewired everything in stereo.
Wow. Even tighter and more musical bass. The plate amp wasn’t even close. No crossover on the class D though, so I exchanged more notes with Randy and did some reading about how guys are powering the bottom end with Crown class D professional amps. They have input sensitivity adjustment and a digital crossover (low pass/high pass).
In the meantime, I received a gift card from one of my employees for home depot, so I go there and get material to make a prototype of what I had in mind for the final OB. A Pure Audio Project style baffle, only without two bass drivers per side, just an Augie per side.
The key to the Pure Audio design is the metal that bolts into three pieces of wood and forms the triangle behind the baffles to give it a three point stance for stability. I found some 48” aluminum slats at home depot for about $12each. [url=
http://www.homedepot.com/p/Everbilt-1-1-2-in-x-48-in-Aluminum-Flat-Bar-with-1-8-...[/url]
Using some foam board I modeled out the bends and length of each slat. If I bent them just right, I could get three 16” aluminum bars out of each slat. I cut them using a hack saw and then bent them using a vice.
I also picked up some clear pine for the two six foot 1X2s for each side and one six foot 1X3 for the back pillar. In hindsight, I should have grabbed cherry or oak, but I can always change that out later if I want to.
I cut the wood into 36” lengths, drilled the holes and bolted it together along with a baffle I cut out of cheap plywood for the Augie and used the same baffle I had cut for the Tang Band. It all worked and was surprisingly stable. It all looked like it was going to work, so I bought some good Baltic Birch ply and made good baffles.
Unfortunately, I picked the coldest weekend of the year to apply the stain and finish to the wood, and royally screwed the baffles up rushing through the job. When it warmed up, I took the sander to the baffle fronts and refinished them so at least they look pretty good.
I then made the second frame and bolted everything together and it looked pretty decent. I also had some adjustable feet that I put on so I could vary the angle. They stand ~37” high and 23.5” wide. The middle of the Tang Band is right about ear level for my listening chair.
I sanded down the aluminum bars and applied a rubber paint to make them black and maybe help with vibrations. I also got some nice black socket head screws, washers and nyloc nuts off ebay and put those on in place of the cheap galvanized nuts and bolts from the prototype and it looks a little more professional. I still need a few more bolts to completely secure the drivers, but otherwise, they are done.
So back to the Crown amp. I found one cheap on eBay. Since the
Crown only has line level inputs, I also bought a cheap high level to line level converter (used in car audio) so I could run the Crown straight off the Torii binding posts. The el cheapo converter works, but I am going to build a “magic cable” designed by Dennis of Hornshoppe Horns fame that basically involves wiring in a 600 ohm resistor into your speaker wires to step down the juice from your amp to something the Crown can use.
So now I am tuning everything. The Tang Band does have the typical single driver rising frequency response. But I have found that playing with toe-in can impact this. The more off axis you are, the less high end you get. I am also playing with the treble shunt on the Torii III to help with this and mid-range shout. The crown crossover point is now right about 100hz and I am running the input sensitivity up around ½ to ¾. Some of this is due to the Crown requiring more input juice which I suspect the el cheapo line converter does not deliver. I should be able to back it off again with the Magic Cable once I get it put together.
These speakers do some things amazingly well. Soundstage, ambience, detail, tight, tight musical bass, real sound quality. Imaging at first was not bad but not great, so I continue to play with positioning and toe in and it is getting much better. They play a variety of music very well. Jazz, light rock, classical, progressive, ambient, classic rock all sound good. Uber complex stuff does give them a little trouble, but I don’t listen to listen to a lot of stuff like that.
I probably have them in too small a room. Even though they are duos and not the trios as offered by Hawthorne and Pure Audio, they are a little physically imposing. I ended up backing my listening chair up and I may move some of my room treatments to fine tune the sound.
I did some REW measurements and they are flatter than expected. Also, I compared the FR of the OBs to the DIY monoliths and you can most clearly see the pickup between 25 and 100hz, which is kind of what I was after in the first place.
It was a bit of a winding road getting here, but for now I am an OB guy. It is a bit addictive.
Thanks to Randy, ProgRob, Darrel Hawthorne and maddog07 for your help.