Ever since I started working extensively in the area of loudspeaker building, I have been “stumbling” onto reports about the Eton chassis, with beautiful flowery descriptions and installed in all kinds of loudspeaker boxes. Since I mainly listen to music, but I also enjoy a good movie on occasion with the corresponding sound quality, I started thinking about building the Duettas as a complete home theater system. I realize that you’re supposed to listen to the boxes first and then build them, but I would like to take a different approach. I am tied to Stuttgart for work, but I live in Brandenburg, so I spend a lot of time commuting between them. Although I would love to take a seat on the famous couch, I just haven’t managed to do it yet. So I decided to build the Duetta Center first, and to combine it with my current boxes. After all, one box would be enough for me to make a judgment about the sound quality of the ER4 Airmotion transformer. Spoiler alert: I am thrilled.
Since the BMT Eton 7-360/37 Hex is installed in the Duetta Top and Duettas, I wanted to use the same chassis in the center. If you look around the relevant forums, a standardized loudspeaker turns out to be ideal in every position. The sound is then transmitted almost identically throughout the room – so it doesn’t sound like a V8 takes off in the front and arrives in the back as an old East German Trabant. Many people say the light version is more cost-effective for the rear and center, not to mention providing a better, more diffuse sound. Of course I can’t make a judgment about that without comparing them.
Anyway, I ordered the Duetta center. All of my questions were answered very quickly and precisely in advance, and that’s how I built my box with a few small visual modifications. Since I only had 51.5 cm of width available on my TV rack, I had to move the reflex openings to the back. So the box ended up a little bit taller, but the inside volume is exactly the same.
I bought some #22 OSB boards at my local hardware store, completely cut to size and very precisely, thanks to Hornbach. As usual, I glued the boards together with cold glue. I didn’t need any joint glue, since the fit was okay.
My helper inspected all of the materials thoroughly. I built an extra compartment for the crossover in the back, and closed off the feeds into the box with hot glue. In addition, the rear wall with the pole clamps is also airtight.
For the crossover, I divided up the available space so that the coils were as far away from each other as possible. That’s the best way to reduce the coupling between them. I also attached the components with hot glue. Then it was time to start smoothing and sanding. Since I could only get 16-mm MDF at the hardware store, I decided to use the #22 OSB board. The material is fairly rough, and glued together patchwork-style, so the surface isn’t too great. As a result, I decided to temporarily glue foil to the box after smoothing it, and to glue velour to the front.
Here you can see the foam rubber at the ready to linearize the frequency curve of the ER4. Once I had put in the insulation, I could install the chassis elements.
The box will be installed on the rack under the television. The rack is fairly stable, even if it looks a little bit “rickety.” The three metal posts are screwed into a granite base; I just need to attach three aluminum blocks to the box, which will fit into the slots in the posts and secure the box. The three points will keep it from tipping. Since I am using the maximum width, and the chassis barely fit as it was, I had to use 19-cm material on the sides as the only exception. Since the glued-on foil didn’t look bad, but it wasn’t so hot either, I screwed 3-mm stainless-steel sheets onto the outside. Metal sheets aren’t great for box-building, but when you sandwich OSB with the sheets I think it’s all right. I don’t hear any difference in the sound, although I’ve only turned it up to “normal” volume so far. Still, the metal sheets don’t touch the poles on the rack or anything else, and they are solidly glued on and screwed in.
For the amplifier, I am using the Denon 3312 (AVR). It replaced my 15-year-old AX 8? Yamaha stereo amp. When I connected it to my Quadral Vulkan MKV stereo boxes, I was amazed by the sound action. Since the boxes are “gas guzzlers,” with an impedance of 4 ohms, the old Yamaha was probably always a little overworked. With the Denon, the Vulkan boxes really lit up. Still, once I had connected my new center, I heard the direct comparison and realized how dull the old noisemakers sounded. No question about it, they can go down pretty far in the bass, but despite their hissing high notes, their tone is fairly dull and muffled. The Duetta center is completely different – fresh, airy high notes and a great bass midrange for the center. I could hear the “class” right away, without even letting the box warm up. I can’t wait to hear whether anything else changes. In any case, my decision has been made: my next boxes will be the big Duettas.
Finally, I want to thank everyone who answered my questions within minutes, even late in the evening.
P.S. I’m listening to the Pixies CD Surfer Rosa right now. I love the understated sound that’s simultaneously fresh and crisp – amazing…
Best wishes to all of you