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Old 20th February 2007, 06:50 PM   #1
Kensai is offline Kensai  United States
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Default SDA in OB experiment

Since my new B20s are now down in the living room as a probationary upgrade, I needed to throw something into the office to get by for the time being.

I had been using Kenwood 6949s in OB there, and I had spare pairs of them lying around, so I dremelled out a couple new ovals, strung up some lengths of Cat5 and fired up 4 of the things as a Polk Stero Dimensional Array .

The point of this thing is to make you sound stage seem much wider than the physical placement of the speakers. Given that this is at my desk, nearfield, the physical width is less than 4', and on first firing the thing up, it was pretty obvious that the technique works, pushing the walls of my little corner out at least another 3'-4' (depending on the recording, of course).

Down side . . . first off, I down graded drivers from the B20s to the Kenwoods. I can find them a bit difficult to listen to now. Second, the EQ settings I had saved for the original single Kenwoods in OB were waaay off. Guessing that has to do with the whole crosstalk cancellation/interference involved with this technique. Third, lost 8-10Hz on the bottom end.

Up side . . . the EQ layout I ended up with was alot simpler than the old single driver setup and actually actually a touch more listenable in terms of absolute SQ (though still not touching the B20s). Also, with alot less EQ in the bass, I was still able to get what feels like more authoritative bass. Not saying its going any lower, just that it seems punchier in the area right before they stop responding at all (~48-49Hz).

I had recommended this to someone over on FullRangeDriver forum who was inquiring about techniques for building a "surroundbar" style DIY project. While Polk is obviously cagey about the "surround" aspect, they seem pretty forthcoming about the older SDA tech they based it on, and coupled with the diagram on the actual surroundbar page, its easy enough to design something like this.

I had been afraid that the fact this was using cancellation/interference to get the job done, that it might be a big no-no for hifi, but that doesn't seem to really be the case. Of course I consider the drivers I used here to be around the border of low and mid fi, and maybe that is the distracting factor. I wonder if using higher quality drivers in this fashion will reveal shortcomings in the technique or if it would result in similar absolute SQ. I could easily see, say, 4 or 5 (or 8 or 9 if you wanted to try surround by using the delay adjustments in your receiver) Fostex FE127s built into a Fostex recommended DBR box (adjusted to accomodate the extra drivers) and wired for this purpose. Be good on top of a big RPTV or if you made it tall and shallow, it could be a floorstanding unit under a wall mounted flat panel.

Kensai
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