Well, there have been some advancement in the project so I thought I would give an update.
One of my takeaways from Decfest this year was the sound that I heard from one of Randy’s creations where he added an Air Motion Transformer to his Besty Baffle speakers. This design utilizes his standard Besty Baffle with a whizzerless Besty driver and a Dayton Audio AMT.
To me, this created some very smooth treble, and because he was running the AMT in dipole, it also created a very large soundstage and sense of air. When combined with a companion Eminence woofer in a separate baffle with a crossover, I thought this provided great sound for the money and an advance on Randy’s earlier designs.
Randy was kind enough to set me up with a pair of the AMTs, caps and coils. I chose 12K as the initial cross-over point based on where Randy was crossing his design and a peak that shows up around this point in the W8 1808 spec chart. Randy runs his design without a coil on the whizzerless Betsy, but I felt eliminating some of that peak would be helpful on tracks that can get a bit ragged and shouty on the Tang Bands.
Initially out of the box, you realize these are pretty serious drivers. Heavy magnets on either side and a heavy face plate give the feel of quality. There are two pieces of a heavy wool-like insulation which can be removed from the back of each driver to allow them to operate in dipole mode.
To get my first taste, I placed them sideways, leaning up against a CD case, on top of another set of speakers set up beside my OBs. I only used the cap on the AMT for this experiment. Here is my first report to Randy:
I got most of what I was looking for even with this crude setup. Sweeter, smoother highs and a bigger overall image.
But I decided that there was too much treble, so I did add the coil to the Tang Bands. To me it sounds like a very smooth transition now and crossing them at 12K does indeed seem to be just about right.
I am also getting some very good information that was missing before. More likely to hear singers breath, fingers on the strings and such. I do believe it has cut down on the rising frequency response issue as well.These AMTs could be added to my current 1.5” mdf baffles, but the question was where to put them on the baffle and would placing them lower and beside another driver impede the sound?
So I made up some mini-baffles out of Baltic birch and mounted them to the left of the Tang Bands, but on top, like a little tab sticking up from the top of the baffle. I’d post a picture, but I need to find another site due to photobucket restricting posting of pictures to another web site.
Well, I didn’t like the sound as much as when I just had them sitting on top of the speakers on the outside of each OB. It seemed to restrict the sound stage width.
So I moved them to the other side of the baffle, to the right (as you face the OB) of the Tang Bands. This seemed to be better spacing which allowed for the wide soundstage. Having them up top also raised the position of the vocalist and generally raised the level of the overall soundstage. I think I will try one more position which would be directly above the Tang Band, but I need to cut my birch baffles a bit so they will fit.
The long and the short of it is that this is a great setup and helps overcome some of the issues with the single driver sound and add a great sense of air. I enjoy a lot of live recordings and this is just the ticket for that kind of open sound. I do feel that things are breaking in and the final sound of this setup could even be better. I probably have about 20 hours on them now.
Once broken in, I will try to get a couple more set of ears over here to see what they think. I might get a little crazy and break out the measurement mic.
You could argue that I had to add a cap and coil which adds more to the signal path. But I am hearing more detail than I heard before and the treble is more pleasant. I think I also lost a little volume and had to turn down the Crown amps running the Augies one notch to compensate and keep things balanced.
BTW, I am also impressed with the price/performance ratio on the Auracaps that Randy recommended. I have a pair of Mundorf ZNs that I will probably swap in, but I’ll wait till these new caps have some more hours on them.
P.S. I like to monkey around with building speakers but if you just want good sound at a very reasonable price and no sawdust:
http://caintuckaudio.com/