Looking forward to your follow up Bif. (Lucky you)
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@Bob -- just wait until I home audition the DEQX. As seems to be the case with a great many audio issues, there is a divergence of opinion. Yes ... on the hand, the time coherence opponents say that most people can't tell the difference between a time coherent speaker and one that is not time coherent. The naysayers may add that like all engineering problems, trade off are made. Perhaps there is greater flexibility in driver selection in the time incoherent space. OTOH, folks like Bombaywalla, Roy Johnston, Rich Vandersteen, and the late Jim Thiel urge us fence sitters to drink the Kool-Aid. And as stated above, Roy has written some really good white papers that explain time coherence and why it so important. At this point ... I am still sitting on the fence and will continue to do so until the US DEQX sale reps sets me up with a home demo. So ... to my fellow fence sitters, hopefully sometime after Labor Day I will be able to post my reactions. Cheers BIF |
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I've been trying to arrange a DEQX home audition. Came close to setting something up tomorrow, but vacation schedules got in the way. Hopefully, soon after Labor Day. Bob, if you read through the Sloped Baffle thread, you might get a better sense of what the DEQX device can do. The beating heart in NOT room equalization ... it is time coherence correction. Most speakers on the market are not time coherent. They may be phase coherent at the x-over points, but not time coherent. The DEQX measures actual time incoherence of one's speakers and makes corrections by delaying various slices of the sonic spectrum to align the output of the various drivers. Room EQ is just an added plus. If you look at most of the Stereophile speaker reviews, one of John Atkinson's tests involves a time coherence analysis. What you see in most cases is the tweeter reacting first, then the mid driver, followed up by the woofer. Sometimes, one or more drivers are wired in reverse polarity to achieve phase coherence at the x-over points. So in the more usual case, the DEQX will slice up the sonic output of the source signal into 4000 segments. Then, using a very sophisticated chip, the DEQX will delay (up to 10 micro seconds) the various segments in order to achieve time coherency. Since the tweeters generally respond before woofer, the sonic spectrum covered by the tweeter may be time delayed vis a vis the woofer. The same approach is applied with the mid driver. Back to the Sloped Baffle thread -- Roy Johnson of Green Mountain Audio has posted some great articles that explain why most speakers are not time coherent, the impact on the summed wave form, and how he attempts to effect corrections. In most cases, the fix, or his fix, is to use 1st order x-overs and to recess the tweeter and mid driver vis a vis the woofer so that the voice coils of each driver are perfectly aligned in vertical space. The DEQX does this electronically. So, I'll report back as soon as I can arrange my home audition. |
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Have not heard and do not know how well executed (always the key), but I agree that the theory seems sound and the approach practical, so definitely something that would be worth hearing for me and I would go in optimistic about hearing some good things. Digital processing of sound that comes out of a speaker compared to what is fed into it sounds like a very practical approach and one that should be practically addressable with modern technology and signal processing algorithms. So it passes the initial BS test and worth further investigation for me. There may be other similar solutions out there as well but don't know so I could not compare this to any other options that might exist. |
If you haven't already seen it, take a look at the comments about DEQX on pages 3 and 4 of the recent "Sloped Baffle" thread. (Expand the contents of all of the posts on each page if necessary, by clicking on the date of the first response on each page, and use your browser's "find" function (usually under the "edit" menu) to search the page for "DEQX"). I've read through all of the the writeups at their website, and I certainly find it to be an intriguing product, especially given that it can in many cases serve as a preamp as well as providing sophisticated room and speaker correction. And I'll say that my BS meter never budged above zero while reading through those materials. Regards, -- Al |
