Andrew (Drewan77) & Bombaywalla, thanks for your kind comments. And Bruce (Bifwynne), thanks for the suggestion about putting pillows on the floor for the speaker measurements. That is also suggested in the manual, and I'm planning to do it. I should have some time tomorrow to start playing with measurements, although I suspect I won't have anything meaningful to report for a few days or more.
Regarding the manual, for my HDP-5 the 38 page user manual and the 143 page calibration ("installers") manual were on the calibration software CD. Similar if slightly earlier versions of those manuals can be downloaded from the DEQX site. (Click on the "owners" tab near the top of the home page, then "upgrades," and then scroll to the bottom of the page that appears).
I printed out the manuals, 3-hole punched them, and put them in a loose-leaf binder, which for lengthy documents such as these I find preferable to viewing a pdf on a computer (unless I want to use the pdf reader's "find" function to look for a specific term).
Content-wise, IMO the manuals are informative and reasonably well done. (Perhaps it was a different story some years ago when Psag and other long-term users purchased their units). Although the online session I had with Nyal Mellor was certainly a valuable supplement, in part because of suggestions he made that were in the direction of greater conservatism in the corrections than the calibration manual would seem to suggest.
Bruce, a question for you: When the DEQXpert people calibrated your speakers, how far did they end up placing the microphone from them? And if you know, how many milliseconds after the direct sound arrivals did they place the point at which subsequent arrivals were windowed out?
The reason I ask relates to the relatively large physical spacing between some of your drivers, which based on pictures I've seen I suspect is around 3 feet between the lowest of the four woofers and the tweeter. On my speakers, also, the two woofers are a significant distance (about 15 inches) above and below the two tweeters, which in turn are about at listening height.
The reason I started thinking about that is it occurs to me that the greater the physical separation between drivers, the greater the distance should be between the speakers and the measurement microphone, which in turn (assuming the speakers are not measured outdoors) will necessitate shortening the duration of the measurement window (prior to arrival of the first reflections), which in turn will raise the minimum frequency that should be corrected and/or reduce the accuracy of the corrections.
The reason I'm envisioning for that is not related to off-axis dispersion of the drivers, since the mic is placed at the level of the drivers which presumably have the narrowest dispersion (i.e., the tweeters). What I'm envisioning is that with the mic placed at tweeter level, the closer it is to the speaker the greater the difference will be between the distance from mic to tweeter and from mic to other drivers. And if the drivers are widely spaced, the amount of that path length difference will be significantly different than the difference between those path lengths as they exist at the listening position, due to the shallower angle between those drivers as viewed from the listening position.
In other words, it seems to me that if drivers are spaced relatively widely, and the mic is not moved correspondingly further away from the speakers during the speaker calibration process (with the downside of shortening the "window," and hence the accuracy and/or low frequency extension of the corrections), the speakers may be corrected for a timing error that won't exist at the listening position.
I've done some geometric calculations for the 15 inch distance between the woofers and the tweeters on my speakers. At a 4 foot measurement distance the path length differential between the distances of the mic to the tweeters and the woofers is 0.18 feet. At my 11.5 foot listening distance that differential is only 0.06 feet. The difference between those differences is 0.12 feet, corresponding to a propagation delay at the speed of sound of about 0.11 ms (milliseconds). Which would seem to mean that the DEQX will correct for a 0.11 ms timing error that won't exist at the listening position, if my speakers are measured at a distance of 4 feet, and a somewhat larger error than that in the case of your speakers.
The planes of the baffles on my speakers, btw, are such that the woofers are mounted a little forward of the tweeters and mid-ranges, presumably to help with time alignment. But that is unrelated to the point I am describing.
Also, to provide a bit of perspective on a 0.11 ms timing error, that would be readily perceivable on the step response graphs JA provides with his speaker measurements in Stereophile, those graphs having a time scale of 1 ms per major division. One of the purposes of those graphs being to provide some idea of the time coherence or lack thereof of the speaker.
Apologies for the long-windedness of this post, but I hope it is clear, and that is the background for my question about the measurement distance the DEQXperts chose to use with your speakers.
Best regards,
-- Al
