This time we compared in a more compatible system. We didn't experience the same mismatch as with the
first series of tests. Results were also posted on
StereoNET.
Update: More photos of this system here:
Unity horn system with TD18H
Antripodean's system was based around the Danley Unity horn.
Actually this photo shows the later version (Synergy horn) but you get some idea. A single compression driver and four sealed back mid drivers load the horn, with a passive crossover. They cover 300 - 20k, include a passive crossover and are time aligned. In Antripodean's system, the Unity sits on top of sealed Acoustic Elegance TD15S drivers. That is a high end 15" driver with the efficiency of a pro driver, yet it looks more like a conventional hifi driver with a phase plug.
First test: Digital conversion test
We tested the sonic impact of the digital conversions with an instant switch comparison. While music was playing, we could switch the digital conversions in and out of the chain. We did this test with DCX and MiniDSP.
CD player (analogue source) > Preamp > DSP (ADC + DAC) > Power amps > Unity horns
The power amps were pro units that were used only for the test. The speakers were running full range, so this meant there was no real output below 300 Hz. It did add an artificial nature to the test. Some tracks were hard to listen to in this way.
Keith was the first to pick and describe differences, although they weren't evident the entire time. There was a slight shift in imaging at times, but I would say during most of the switches, it wasn't evident. The general consensus was that the digital conversions had a very minor influence of the sound. At one time, Keith felt that MiniDSP actually improved the sound slightly.
Instant switch box
Gainphile made up a test box for the event:
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| Test box built by Gainphile |
With this box, we were able to switch both inputs and outputs, and adjust the level of one of the inputs with the pot. We chose this method rather than blind testing because it's a much easier method to compare. Blind testing tends to rely heavily on audio memory and serves only to remove bias. We were concerned less with bias and more with making the test revealing of any differences. At the moment of switching, the best judgments can be made because there is a quick and sudden contrast that is more revealing than relying on memory. I found it was critical to switch at the right moment. Switching during a sustained note made it easier to pick differences in tonal balance and imaging.
MiniDSP vs DCX
Although they were both quite close, MiniDSP had a slight edge although not everyone was entirely convinced. I noticed a small difference in the top end, where MiniDSP appeared to have a little extra detail. This seemed to have a very slight enhancement to the sense of openness. Keith felt there was more bass definition and slightly more texture, but the others didn't seem to notice any of these traits.
Due to time limitations we didn't do as many comparisons as intended. There came a point towards the end of the day where we had reached our limit. It was a fairly hot and humid day and we became more interested in listening to music and chatting. Considerable effort was involved in working out how best to set things up and we did a fair amount of critical listening.
SNA thread with listening impressions >
Next: Conclusions on the testing >
You can also see a pair of 6th order bandpass subs with 12" drivers. 
