Which order to apply room correction tools?

@alanhuth I haven't used MSO myself but I believe it can be used on its own to determine the PEQ you should apply to the subwoofers. I would not apply any manual PEQ to the mains, and instead let Dirac take care of it. But you need to perform the subwoofer PEQ and time-alignment first, otherwise Dirac's 2-channel measurement and filtering won't work as well.

The time-alignment I am referring to is the same as what a surround sound receiver or processor typically does. It doesn't have anything to do with PEQ.

Imagine your subwoofer is located 100 feet away from your head, while your left speaker is located 10 feet away. If you play a continuous sine wave at your crossover point of 80Hz, you could adjust the phase of your subwoofer until there is no destructive interference. But when you played music, things would sound very wrong because sound from the subwoofer would arrive way too late compared to sound from your left speaker.

This problem will then present itself when performing the Dirac measurements, and consequently the computed filters will not really do what Dirac thinks they will do, and things will still sound wrong.

miniDSP has some articles about measuring the time differences between speakers:

• Measuring time delay for home theater with the UMIK-1 or UMIK-2 and REW
  
• Time-aligning speaker drivers with UMIK-1 and UMIK-2
  

I'm also assuming your left and right speakers are essentially identical distance from your head, so Dirac or REW will measure a very small difference between their impulse arrival times.

Millercarbon: upon re-reading this, I came across as a smart ass. Sorry.  Not my intention.  

You obviously have deep experience in these areas, and your advice about placement etc. was very helpful, and actionable.  I know what to do with that advice.  Your advice about listening, clapping your hands and listening, etc. is harder to turn into action.  What do I listen for?  What do I do when I hear things?  Any elaboration would be appreciated.  

Nekoaudio: if you get a chance to answer the two questions I posed to you above, I’d be most grateful.

Gotta burn to learn.  

That's nice. There is by the way no such thing as time alignment with subs. But being impatient, carry on.

Thank you, Millercarbon.  i’m sure you’re right, but I don’t know if I have the patience or ability to do that much listening. I’d like to try the tools.  Some day you can say told ya so.  

Nekoaudio:  Thanks so much for your reply.  That is exactly what I was looking for.  A couple of clarifying questions:

1. Are you saying that’s doing PEQ on each subwoofer requires both REW and MSO, or are you saying do both separately?

2. You say use REW to set the subwoofer timing relative to mains.  What about the mains?  Should you do any REW PEQ on the mains at all?  Or is that taken care of by Dirac?

Thanks,

Alan

I agree you should first do everything without applying any filtering. Place the speakers, then find good locations for the subwoofers. Since you have 3 subwoofers, you are probably going to have to treat at least two of them as a single channel so keep that in mind during placement: in other words two of them probably need to be the same distance from your seating position.

Room treatments should go on either as part of your first step in speaker positioning, or right afterwards. Since everything coming next is going to be influenced by the treatments.

Second I would use Room EQ Wizard and Multi-Sub Optimizer to perform PEQ independently on each subwoofer (two of which will be grouped into a single channel in the SHD) to flatten their response.

Third, use Room EQ Wizard to figure out the appropriate delays (positive or negative) for your subwoofers, relative to one of your main speakers. Enter these delays into the SHD for the subwoofer outputs.

At this point, your subwoofers should have relatively flat frequency responses and be time-aligned with one of your main speakers.

Finally run Dirac.

The best method is speaker placement. First being to find the best location for response, then after that to get them absolutely precisely symmetrically equidistant for imaging.   

With three subs they should be asymmetrically distributed around the room so that each sub as well as your mains are different distances from the corners of the room. This alone will achieve a very smooth low frequency response. Set the sub levels and you are about 90% of the way there. 

From this point on if you think anything is a matter of pushing a DSP button, good luck! No electronic room correction does anything even close to what it says. It does nothing for example to correct the room. Everything it does is to the signal. No getting around this.  

The fact of the matter with rooms is they are all so different and particular there really is no solution other than to sit and listen, walk around and listen, clap your hands and listen. In other words listen. Don't take my word for it. Mike Lavigne has the best room I have ever been in, and he paid big for it, some of the best acoustics guys on the planet, and even with all of that why is Mike's room so doggone good? Because he listens! He has made all kinds of improvements to his room, and the better it got the more he heard and by listening closely has been able to continue to find areas of improvement.

Your room is no different. The fundamental process is no different. Learn, look, listen. Try stuff, hear what it does. DSP is a crutch. Toss it. Get some Owens Corning acoustic panels, or GIK if you want to spend more for the same thing. Get some Synergistic HFT. Use these things. Move them around. Listen. Learn from your mistakes. Listen. Find a way to make it even better. That is the order of the process.