Seeking Idiots Guide to multi-sub 2ch REW/Dirac Live calibration for miniDSP

[Eulipian]

If you haven't already, you might consider checking out @Keith_W's excellent free REW ebook to help you with taking measurements and using REW.

As the ebook says, if there is a 90-degree calibration file, use that and point the microphone at the ceiling. If the 90-degree is not available, then use the 0-degree one and point the mic between the L/R speakers.

Use impulse/step response in REW to align the subwoofers with the main speakers. Check this post to get an idea of the process.

Run Dirac Live last and curtain the correction to 500Hz (or lower).

Thanks for this very helpful information. I appreciate it.

 

[janbth]

As the title suggests I'm really hoping someone can provide a step-by-step idiots guide as to how to, once and for all, properly calibrate my miniDSP Flex Dirac Live version for a 2.2 music setup.

I've tried numerous times and either miss something or do something which later transpires is wrong (e.g. using MSO as I see now that Dirac enable miniDSP Flex is listed as incompatible) or follow a rigid process that I believe is correct and when it comes to the listening test sounds awful so therefore must have done something incorrectly!

I have the following hardware in my setup;
miniDSP Flex unbalanced with Dirac Live
Nord acoustics MP NC252 2ch power amp
Arendal 1723S THX bookshelf speakers (desk setup so quite near field)
SVS PB1000 Pro x2 subwoofers (placed about 9ft behind me close to the backwall with no option to relocate)
UMIK-1
I'd like to understand a full end-to-end process if someone is kind enough to draft one as i've seen high level bits and pieces online, or guides which become dated or don't account for nuance....etc what I'd really appreciate is full end-to-end process;

• Which mic cal file to use (given i have speakers in front, subs behind)
• Do i set XO first or later in the process? Should i high pass speakers or just low pass subs?
• For the routing matrix do i sent L+R channel both L+R subs or keep them separate?....etc
• Do i use REW to gain match & time and phase align subs and speakers, if so how and in what order? What options do i need to activate in REW.....etc - my current calibration sounds awful i think due to time alignment with subs being wrong so always hear a distracting boominess that sounds completely out of sync
• For the acoustic timing reference what is the correct way to use this feature to ensure time alignment is correct
• What stage in the process do i run Dirac Live calibration and how to ensure it improves sound rather than destroying any pre-calibration i've already done on subs....etc?

I run Dirac ART now, but your setup is quite similar to my previous setup with a NAD M33 amp connected to my two mains and two subs via a miniDSP 2x4 HD. The M33 did the crossover, and delivered signal to one sub out, using the miniDSP to split to the two subs. I spent years measuring with REW, tweaking and experimenting, and I eventually found ways to «do it right», and that worked very well for me.

I disagree with some of the advice that has been given here, in particular about time alignment, so for the record, here is my take on sub integration with multiple subs:

1. Understand the room modes in your room. Read up on room modes, and try to map out the standing wave patterns in your room using tools like the RTA in REW, room simulators, Amroc for visualisation, etc. This may influence where you put your speakers, subs and the listening position. If you have no choice in where to put them you are done, but at least you will have gained insight and knowledge.
2. Use bass management with crossover filters both on subs and mains.
3. Play the subs in mono. Recently, there has been a lot of discussion about «stereo bass». I consider that an advanced topic that may or may not work. Learn to do mono first, and experiment with stereo later.
4. When measuring with REW, point the mic to the ceiling and use the 90 deg calibration file. If you measure in a lot of locations this is far more convenient than pointing towards speakers and using 0 deg calibration. If you are interested in the bass region (as when doing sub integration) it doesn’t matter much, but even higher up in frequencies the difference in measured response will be small.
5. Set up the subs first to play well together, then integrate with L+R from the mains. When setting up the subs, pay attention to the levels. For example a sub located at mid wall will need to play 6 db louder than one in a corner due to boundary effects. Start with subs in exact mono, then experiment with relative time delays to get the smoothest frequency response. REW allows us to easily take a series of measurements while tweaking a parameter for visual inspection.
6. Apply PEQ filters to both subs if you need to cut down resonant peaks. This step is really optional, if you intend to run Dirac later.
7. Crossovers. Look at both frequency and phase response, and try to find a smooth region. Try to stay away from modal peaks or dips. Don’t be afraid to go high - I used 120 Hz. Use 80 Hz if you have no other information.
8. Focus on frequency response, not impulse response. The goal is to make it smooth at the crossover. Use time delay to get the subs and mains in rough agreement, then fine adjust for frequency response smoothness. This is the point where I disagree most with others. I believe there is no evidence that subs should fire at a particular time relative to the mains. In Floyd Toole’s Sound Reproduction you will a section where he explains this better than me. In the 4th Edition it’s Sec. 9.6.5, «Phase Shift at Low Frequencies - A Special Case». A dip at the crossover, on the other hand, is audible.
9. I always use an (acoustic) timing reference, but I rarely need to pay any attention to it. Occasionally, if you experiment with trace arithmetic or the Alignment tool, it is important. I would never use it for time alignment, for the reasons I gave above.
10. Run Dirac as the final step. Using a curtain at 500 Hz is a good idea.
11. Check your work by using test tones. ASR user @KSTR has provided a very useful set of burst test tones: https://www.audiosciencereview.com/...luation-of-room-modes-and-other-things.29310/. Especially check the frequencies around the crossover.

OK, this is what comes to mind about multisub integration. I hope it is useful. Good luck!