I revisited Dirac after more than a year and dug up these:
Dirac manual page 17
Using the microphone positions indicated by the Dirac Live Calibration Tool™ will generally give you consistent results.
However, the microphone positions are not required to be in exactly these positions - if your listening environment looks different then
you may use a different set of microphone positions. Taking all measurements close to the sweet spot will generally not give optimum
performance because the microphone positions need some spread in order to acquire enough acoustical information about the room.
Elsewhere there is information that even the number of nine mic positions is "typical" or "approximate" (marked with tilde) . Dirac demands
only one must-do: the central position first measurement.
View attachment 12327
Dirac FAQ
3.6. Why is there no validation feature?
The predicted response may look too good to be true, but it is important to interpret the curves in the right way; the prediction curves show the response in exactly the point each curve is based on.
In theory the curve can be totally different just a small distance away from it, but in practice this is rarely the case. In order to avoid optimizing the filter for a really small area at the expense of the actual listening area, multiple measurements are used, taken in different points. Their average is the basis for the filter calculations. Together with the spatial robustness of the Dirac Live room correction technology this will result in a filter that sounds good in a large area. However, for a measurement to produce the predicted curve the microphone need to be in the exactly same position, otherwise the result will just be close to the prediction. It is also important to compare a validation measurement to the curve that corresponds to that measurement position and not the average curve.
If you want to measure the result of the filter you can either use some application such as HOLMImpulse, or you can select the Dirac Audio Processor as the output device on the sound setup page. If this method is selected it is very important to note that the Dirac Live Calibration Tool will disable filtering in the Dirac Audio Processor before each measurement, and you will have to enable it manually real quick. The reason the Dirac Live Calibration Tool disables filtering is that most measurements will not be for validation but for room analysis, and in this case any filtering has to be disabled.
It's not hard to see some wishy-washy talk and contradictions in the above. The conclusion (in blue) is that you can measure the calibrated curve, even with Dirac -- "if you want".
My take is Dirac hopes to avoid the situation where amateur users (vast majority of applications) accuse them of misrepresenting the filter effects shown in the simulated curve.
It would not be difficult to introduce simple "filter validation" function. Instead they direct to outside apps or a workaround which is not in the manual. These solutions are
definitely not for amateurs, and the assumption is the advanced users know what they are doing and understand how it all works.
Based on my understanding of room acoustics, I am not seeing the contradictions that apparently you do. Their explanation makes perfect sense.
Offhand, I am not aware of any consumer grade EQ tools which employ spatial averaging and which also provide some precise mechanism for measuring spatially averaged, post-calibration filter response as part of the same tool. I think Dirac outlines some of the valid reasons underlying this in the above.
It also goes to the target market philosophy of keeping an EQ package user interface simple and user friendly if it is intended for less sophisticated consumers, rather than professionals or sophisticated hobbyists. Dirac is not by design intending to be an Acourate, Audiolense, etc., and Dirac much prefers an important difference in technical approach to those by using multipoint averaging. Overloading it with extra built-in features, such as post calibration measurement which most users do not want or feel they need, would overcomplicate it. It would also add to development cost and therefore to the price the consumer or licensee must pay. There may also be resource limitations in DSP processing hardware on miniDSP, AVRs, prepros, etc. making post calibration measurement difficult to implement in those targeted components.
So, Dirac is what it is, subject to its choice of product philosophy. If one wants multipoint spatial averaging in both the calibration and also post-calibration measurements, I do not know where one finds it, even on EQ packages solely designed for a higher resource PC processor, other than by using workarounds such as suggested by Dirac.
I am hazy on the details, but Audyssey has a Professional-grade product, not to be confused with Audyssey Pro, a largely defunct PC-based calibration tool I once used awhile ago. From photos, the newer Professional tool uses a fixed array of of many, multiple mikes across a long boom, which apparently is not moved during calibration. It is possible, though I do not know for sure, that it might also provide precise post calibration, spatially averaged measurement.
Trinnov, which is also professional grade, uses its own closely spaced array of 4 mikes. Possibly, it also provides for post calibration measurement capability without moving the mike array, But, again, I do not know.
There is no similar measurement problem due to spatial averaging with EQ tools that rely entirely on single point response. One can just leave the measurement mike untouched for the before/after measurements and employ different single point measurement suites, such as REW. I believe
@RayDunzl and
@dallasjustice now operate this way.
Arguments about the techical advantages of single point vs. multi point spatially averaged will no doubt go on, inconclusively. Take your pick. But, single point EQ tools are definitely preferable if accurate post calibration measurement is important to you.
) - at the end of the day you weren't using the LX521 so it's not important.
