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Just did some EDITS to this post.

I dived into my first tests with DiracLive a couple days ago and got very unsatisfactory results, so just did a complete read thru of the minidsp DiracLive manual highlighting key points and now have a few questions for anyone out there more experienced. While this is a lengthy entry, there are some important questions that come up comparing DiracLive's performance to REW for optimal DSP room correction. 

1. One of the things I've read on the the minidsp site when integrating a sub with 2 satellites is to first get things properly time aligned between sub and mains with REW and to set the crossovers. I did this. But when reading the minidsp DiracLive manual, it mentions  on page 14 under section 4..3.1 is to disable the low pass filter (which is essentially disabling the sub crossover, yes?) on the sub before doing DiracLive measurements. Then why is it advised to first set up one's crossovers prior to doing DiracLive measurements on the Minidsp site?

2. Is it at least still advisable to at least leave REW time alignment corrections entered on the minidsp plugin before doing the DiracLive measurements? 

3. Do the EQ "corrections" generated in DiracLive follow a different principle than what REW Auto EQ does? The correction curve generated in DiracLive after doing measurements looks much less sophisticated that what REW Auto EQ does. I.e., DiracLive's seems to follow the curve of what the overall EQ response is doing rather than generate it's opposite and equal EQ curve that REW Auto EQ does (and for that matter, Sonarworks which I've used as well for my mixing stereo as a musician also generates an opposite EQ shape) when creating a correction curve for export into the minidsp plugin.

4. Which then makes me question if REW Auto EQ works on a different or similar principle than DiracLive - I'm asking here strictly in terms of the EQ compensation they generate NOT including impulse response of DiracLive of which I'm aware is a big component of getting optimally corrected sound.

5. Which then begs the question, do more experienced minidsp users get better results with REW than DriacLive in terms of fine tuning their systems with exported REW EQ curves that one can then import into the minidsp PEQ Advanced tab? 

I read an excellent article by experienced audio engineer and author *Bob McCarthy called "Phase Alignment of Subs - Why I don't use the impulse response" just google this with Bob's name and you will get a hit. (apologies, I'm unable to share URL links for some reason on this Community forum as I get flagged as "spam" so not posting the URL here. (I do realize that this concerns impulse response regarding subs and not mains, but still a great article)

Oops, one last question. on page 47 of the miniDSP DiracLive manual, it talks about DL filter exports...do these replace the 4 configurations that the mindsp plugin offers or stack on top of them?

Geez, this is a lot of questions..! So thanks in advance for anyone willing to chime in and share their expertise!  Insert big smiley face here!

Again, thanks so much to all those, especially @entripy, @Ultrasonic, for offering your experienced advice so far.

1. I think you must be missing context somehow. Dirac Live corrects the system of the equipment and the room. If you change anything about the system or room (except for volume) the Dirac Live correction needs to be done again otherwise it is correcting a system that no longer exists. That's pretty basic.

2. Yes, essential, see answer to 1.

3. Yes, Dirac Live uses rather advanced maths and different algorithms to most competitors. Dirac Live should end up with the result being the target. It does what is needed and no more. The display tends to be what it has achieved, not how it achieved it. (I haven't calibrated for years so my memory is vague)

4. Everything works on a different principle to Dirac Live. Ok its all filtering of some sort but there are a huge number of different ways of using filters. It is rather beyond EQ. Perhaps a key basis of the Dirac Live theoretical basis is that they consider the system to not be minimum phase. This is a badly named term with a very specific technical meaning that I won't explain but if they are correct most other solutions are minimum phase which can't hope to solve a non minimum phase problem. Their solution is not minimum phase.

5. Nobody with Dirac Live is likely to use anything other than Dirac Live for correction. You can get such amazingly good results from Dirac Live that it normally easily beats more traditional solutions.

There is a technical paper on the theory behind Dirac Live. As a DSP engineer I found it very convincing. Almost every other system just tends to automate what folk were doing in hardware with parametric equalisers decades ago. It works about as well as it did then even if you throw more equalisers at the problem. Almost any solution to room correction will improve on an average badly sounding room but not many can approach the optimmum solution.

But I'm all for experimentation. If you think you can get better results with REW, fine. I think it will help, but not as much as Dirac Live.

Now I'm not saying REW is rubbish, it isn't, it is a great program, but having read many other papers about other room corrections systems I haven't found any with such advanced maths and such rigorous theory based on reality.

Now in case I sound like a Dirac Live shill, there are room issues it cannot solve, although it is great it may not make your room perfect. No other system could either.

CarlosdelJunco wrote:

1. ... But when reading the minidsp DiracLive manual, it mentions  on page 14 under section 4..3.1 is to disable the low pass filter (which is essentially disabling the sub crossover, yes?) on the sub before doing DiracLive measurements. 
 

Hi, it says there that is for a multichannel system. Since you are posting this in the SHD forum section, that doesn't apply to you.

Thanks John and entripy for your replies.

@john, regarding question 1.  I'm still confused as to why would turning off the low pass filter for the sub on a 5.1 or 7.1 system (which the minidsp DiracLive manual suggests to do) would be any different than a 2.1 system? 

  @entripy, thanks for your input and taking time to answer all the questions!

1. apologies if I'm misunderstanding something "basic" here. What you said entripy makes makes complete sense to me, that "changing anything about the system or room (except for volume) the Dirac Live correction needs to be done again otherwise it is correcting a system that no longer exists." Hence why I was surprised to see what the manual say what it does..! Again, whether it's a 2.1, 5.1, 7.1 system, if there's a sub or two or more in the chain it makes complete sense to leave the low pass filter on for the subs in the mindsp plugin while doing one's DiracLive measurements. Hence why I was pretty surprised to read this. See my attached screenshots with my highlights and underlining.

So, simply said, the only thing I should have running in the SHD plugin before doing DiracLive measurements besides corrected time alignment, is the crossover I've decided for the mains and sub (ie, leave the low pass filter on for the sub and high pass filter on for the satellites), yes?

It's actually normal to set the low pass filter on the sub as high as possible, or disable it if possible, because the crossover in the SHD is replacing that job for 2.1 and 2.2 systems. So if the low pass filter on the sub is what is involved that makes sense in general, not just before Dirac Live. But it wouldn't make sense if referring to the low pass filter in the SHD crossover. So it rather depends on which low pass filter and where it is implemented.

What you shouldn't be doing is disabling any filtering before Dirac Live and then re-enabling it afterwards, or vice versa. Any filtering that exists before Dirac Live needs to remain and should not be changed, wherever it is implemented. And that is the essence of why the SHD plugin features need to be completed prior to Dirac Live.

You also have to remember that Dirac Live applies to many different hardware systems so its manual isn't always sufficiently specific for the SHD which has many other features which other systems may not have. Because of that its usually best to rely on minidsp advice where  Dirac Live advice differs. Inconsistencies typically come down to that tension between  the general and the specific.

Man, I'm really sorry to put you guys thru this and pretty embarrassed: I was totally reading that one paragraph in the manual as if it was referring to having any low pass filter on whether it's a minidsp plugin or on the actual sub. I'd already disabled the low pass filter on the sub...just too much information to digest all at once. Again, I'm one to "overthink" things and get myself into all sorts of trouble..

All good and totally understand what you say entripy. Thanks again for your patience.

 

Since I glossed over the technical term "minimum phase" the REW site has a simple explainer related to room acoustics -

www.roomeqwizard.com/help/help_en-GB/html/minimumphase.html

As that explains, simple EQ cannot correct some room problems. Dirac Live goes further than simple EQ and can allegedly cope with some room problems simple EQ cannot, but still not all room problems. The more technical paper on the philosophy behind Dirac Live -

www.dirac.com/wp-content/uploads/2021/09...lization-filters.pdf

Entripy, Thanks for your enthusiasm in sharing these articles. At the moment, it's a bit over my head, but I do trust what you say and also just saw this simpler article "dirac-live-vs-rew" on the mindsp site which is, at the moment, enough for me to digest.

Will do a new DL test or two today and report on the results.