TOPIC:

I own a single mDSP 2x4 presently, for refining my speaker project, and wonder if I'd be better off moving up to mDSP 2x4HD for future purchases for all the speakers instead. I'm building WMTMW active speakers with mDSP 2x4 XOs for each of the front three speakers & scaled down, but same idea for surrounds & rears, along with 4 LFE subs. Then I planned on getting an OpenDRC of some kind for final room setup. Now that the 2x4HD is out, should I buy them instead and go linear-phase XOs and then could I skip the DRC? I admit I don't fully understand how the room is equalized with DRC, but it appears to be with phase manipulation. With the playing around I've done with the 2x4 and then listening, what I'm hearing is pretty great right now. I've nearly finalized on the speaker cabs & drivers and amps and using UMIK, I measure +/- 2db outside my shop over it's operating range with 12th octave smoothing and nearly that good inside my shop, except for a few bass peaks. Just not sure which way to proceed and feel the experts here would know better than me.

I welcome your advice & even criticism as you feel led. Thank you!

Could you draw a diagram of what you are thinking of doing?

I've attached a PDF of how I'm using the mDSP 2x4. My system would include 1 mDSP 2x4 for each of the front speakers, with the 2nd input/4th output of each of these 3 mDSPs feeding an active side or rear surround speaker. A 4th mDSP 2x4 would be used for subwoofer control and the last rear surround. Each is fed an input from the HT receiver 7.2 preamp outputs.

I'm just wondering if I should use standard mDSP 2x4 as planned, then get an OpenDRC or Dirac for room correction, or Upgrade to the mDSP 2x4HD for each of these 4 and do room correction in them as well as crossovers & PEQ. From the experimenting I've done I can get the speaker pretty dang flat in different rooms with the standard 2x4, but it's not linear phase. How big of a deal is linear phase?

Where is the signal coming from? Is it originally HDMI, or...?

Wrt to "How big of a deal is linear phase?", I think a fair answer to that is "it depends". Flat frequency response (on axis, without room) is probably most important, but I find the best systems I hear are linear phase. With that said, I did a simple (single) blind test last year and 3 of 5 preferred the linear phase crossover i.e 2 of 5 preferred non-linear phase. I don't it's possible statistically speaking to draw a conclusion from my results but it was interesting. Everybody was able to hear a difference, although as I recall a couple found it hard to tell.

I'm just wondering if in a small dedicated HT room, with so many sound sources (4 sub, 7 speakers) if trying to sort out the phases is improved by linear-phase. The reading I've been doing on-line somewhat mirrors your own findings, some people can tell the difference, some can't. Those who can tell, aren't sure what they prefer.

I'm also concerned about the delays caused by FIR filters, considering the tailoring of responses of 11 sound sources. How can I be sure to match delays if I use FIR XOs for each of them?

I also agree that flat extended frequency response is first priority. I experimented with UMIK & REW on my existing speakers, and just using the options avail on my Yamaha receiver to flatten the room interferences dramatically improved the sound.

Hm..... I'd prefer not to have words put in my mouth, what you said you read does not "somewhat mirror" what I said...

Anyway, maybe it's like loudspeaker dispersion, some people are used to a certain sound (excess power response due to tweeter flare near the crossover, for example), even if it's technically incorrect, and will pick that as their preference. Who knows.

Wrt delays, you will have to set them manually based on the delay you calculate for your filters. The easier way is to use Dirac Live, having done my HT both ways I'd pick the Dirac solution if it was an option...!

So then, if I'm understanding you correctly, I should continue with mDSP 2x4s (not HD version) with standard LR crossovers as I've been doing. Then, with it all installed, get a Dirac Live to resolve any phase issues or Room effect. Is that right?

No, I didn't say that at all...

Unfortunately, there's no ideal solution. It sorta depends. I asked you a question, you didn't answer it, so I can't offer any advice.

I'm sorry, John. I'll be using analog (turntable) & SPDIF, HDMI & toslink inputs.

No worries. That excludes the nanoAVR series then. You might want to look into the forthcoming DDRC-88BM plugin for the DDRC-88A which will support active crossovers. Otherwise, I think I would go with your first thought.