Is DEQX a game changer?

Andrew (Drewan), thanks very much for providing the info in your system description thread. As I indicated there, it provides a good quantitative perspective for DEQX newbies such as myself on what is possible in the speaker calibration process.

Mapman, thanks also. Regarding DEQX's recommendations for how to approach speaker calibration, on the one hand the manual states:

The microphone should be mounted about 2 ft to 3 ft (or 60 cm to 1 metre) from the speaker and lined up with the tweeter axis. Best results will be obtained if you use a microphone stand with a boom to support the microphone. If larger speakers are used it may be necessary to mount the microphone further from the speaker, in order to reduce the angle between the drivers and the microphone (and any
associated off-axis effects). However, moving the microphone further from the speaker will potentially increase measured room effects and /or reduce the period of the measurement before the first room reflection, hence the reason for the suggested distance of 3 feet. Better results may be obtained by measuring the speaker outside, provided that a quiet location is used. One method, particularly useful for large speakers, is to rest the speaker on the ground, pointing up at a 45 degree angle. The microphone should still be lined up with the speaker's
driver axis, i.e. it will be pointing down at the speaker at a 45 degree angle. When measured with this method, the speaker measurement can be similar to that obtainable in an anechoic chamber.

But on the other hand they state:

The longer the delay for the first room reflection to arrive relative to the time it takes for direct sound to reach the measurement microphone, the more bass information can be gleaned. A minimum target would be 3 milliseconds, which will limit measurement usefulness to frequencies above about 400Hz. Doubling this to 6 milliseconds for example, achieves an additional octave of bass resolution: down to about 200Hz, which is the lower correction limit used for this case. In this example, if you attempt to correct below 200Hz phase distortion will be introduced to the filter, which will make the resulting sound dull and flat - worse than the uncorrected speaker.

The 3 and 6 ms 400Hz/200 Hz guidelines seem very aggressive (optimistic) compared to inputs that were provided to me by Nyal, and that have been cited by others earlier in this thread, and that were used by the DEQXpert people when they set up Bruce's (Bifwynne's) system. (They terminated the "truncation window" about 17 ms after the direct sound arrival in his case, as contrasted with the 3 and 6 ms figures cited in the manual. Also, the corresponding figure in Drewan's case was about 18 ms).

So it seems that given the great number of variables that are obviously involved DEQX is understandably not able to provide a specific quantitative feel for the degree of compromise that will be introduced at various points along the continuum between ideal measurements taken under essentially anechoic conditions, and points that are significantly less than ideal.

06-07-15: Drewan77
At the risk of repeating myself (apologies), are you absolutely sure that there is no chance of taking an outdoor speaker measurement?

Pretty much. Just moving my speakers off and then back onto the bases and footers I have them on, which elevate them less than 5 inches, involved non-trivial effort and careful logistical planning, as they weigh 108 pounds each. To get them to a location outdoors that is both level and not close to reflective surfaces they would have to traverse several steps and approximately 50 feet, and then I would have to provide some non-reflective means of tilting them back, to minimize ground reflections. Also, less significant additional complications would be that I would have to run about 50 feet of speaker cable (my amplifier also weighs more than 100 pounds), and a 40 foot or so XLR extension for the mic.

Well before deciding to purchase the DEQX I had realized from the comments earlier in the thread and from reading the DEQX literature that as a practical matter I would be unlikely to realize its full potential. But as long as it ends up providing me with a substantial improvement over what I had I won't be disappointed. As Mapman aptly said just above, "it might be a dilemma for which one practically just has to accept some kind of compromise."

Best regards,
-- Al

Al, outdoor measurement is mandatory, IMO. With the help of two people, we moved TAD Reference1 (almost 400 lb apiece) and four monoblock amps from my listening room to my driveway. We used a dolly, easily purchased on the internet. If you are willing to invest the time and cash on DEQX, you really owe this to yourself.

Al,

Were you to decide to undertake the task I would gladly volunteer to help with the schlepping. PRoblem is I do not live very close. Maybe there are some other strong and trustworthy folks out there who live a bit closer that might be willing to lend a hand as well if it comes to that.

Psag and Mapman, thanks very much.

Obviously I don't have to finalize any decisions just now, and we'll see how things develop in the coming weeks. But while I certainly value the experience-based inputs from Drewan and Psag, and while it's certainly clear that realizing the full potential of DEQX requires an essentially anechoic measurement, what doesn't seem clear (and probably can't be, given how many application-specific variables are involved), is the degree of compromise that will result in any given situation from doing the measurement indoors.

Obviously Drewan and Psag are strong advocates of outdoor measurement. On the other hand, though, in this post by Forrestc, who also seems very experienced, indoor measurement is described as "by no means a deal breaker." And in Kal's (Kr4's) review in Stereophile the speakers he calibrated on his own, and I presume also the other pair he used, which were calibrated remotely by DEQX, were done indoors. The pair he did himself, with good results, were done with the impulse response truncated at only 5.5 ms after the direct sound arrival, and with the correction performed down to 200 and 150 Hz in the two profiles he created, with the latter even being slightly preferred!

Perhaps one relevant variable influencing the degree of compromise resulting from indoor measurement, btw, is how much correction is needed by the particular speakers that are involved. In that regard I've noted that the impulse and step responses I've measured on my speakers, during the first few tenths of a millisecond or so and with no panels near them or the mic, seem to me to look pretty good. Relative, that is, to the step response plots I've seen JA present in Stereophile in conjunction with reviews of other floor-standing speakers which do not use first order crossovers.

So we shall see. Thanks again for your inputs.

Best regards,
-- Al

I'd love to hear other folks POV on the cutoff frequency that worked best for their speaker calibration.