L.A. Home Theater Group Checks Out MiniDSP DDRC-88A Dirac Live Box

L-R: (front) fookoo_2010, Spanglo, Scott Simonian; (middle) ivanpino, Rayjr; (back) sdurani, Scott Wilkinson, Toc, aceg1, holt7153

Yesterday, AVS Forum member Ray Coronado (Rayjr) hosted a gathering of the Los Angeles Home Theater Group at his home in Palmdale, CA. Aside from the general camaraderie enjoyed by that group—and all other AVS Forum get-togethers—Ray wanted to demonstrate the MiniDSP DDRC-88A, which provides eight channels of Dirac Live room correction. Apparently, there isn’t much opportunity to audition the box before shelling out $1000 for it, so Ray wanted to give people a chance to hear it.

His home theater is beautiful, though inadequately air conditioned, as he is the first to attest—with all the electronics and bodies in there, it quickly became a sauna, so we rotated in and out to keep our cool. The audio system includes a Lexicon MC-12HD pre/pro, ATI AT3007 power amp (300W x 7 channels), NHT speakers all around (VT-2.4 for the front left and right, VS-2.4 for the center, left and right side surrounds, and left and right rear surrounds), four Hsu ULS-15 subwoofers, and a Tekton Pendragon dual-12″ sub with its ports plugged to function more as a mid-bass module.


The MiniDSP DDRC-88A provides Dirac Live room correction for eight channels.

The DDRC-88A was inserted between the MC-12HD pre/pro and AT3007 power amp with 16 RCA analog interconnects. (The unit also offers balanced connections using Phoenix connectors.) Using the included setup software on a Windows computer and a UMIK-1 microphone (an extra $70), you can create and store up to four separate correction profiles—which include amplitude and phase filters—and switch between them as needed for different program material. Switching between profiles in the unit takes a couple of seconds, but engaging and bypassing the correction is nearly instantaneous.

Ray showed us the setup software running on a Windows laptop. During setup, the computer must be online, because the actual calculations are performed in the cloud and the results are sent back to the computer so the process cannot be reverse engineered. You can let the Dirac system calculate a target curve, you can specify your own curve, or you can tweak an existing curve. Also, each speaker can have its own target curve, or you can link two or more speakers to the same target curve; Ray has essentially identical speakers all around, so he linked them all to the same target curve.


The first step is setting the overall input levels, which should be in the green area of the bar graphs next to each channel.


Next, you select the type of seating you have—chair, couch, or auditorium—and measure each speaker’s frequency response with the mic at the main listening position. This is followed by separate measurements at eight other locations so the correction can be averaged over a wider area.


In this screen, the gray lines are the responses of each speaker before correction, the red line is the target curve calculated by Dirac, and the green curves are the predicted responses of the speakers after the correction has been applied.


Here, you can see the target curve and predicted post-correction response, which follows the target almost perfectly above 80 Hz. Below 80 Hz, the response doesn’t matter, because Ray crosses over all main speakers to the subwoofers at that frequency. Notice that the target curve is slightly “tilted,” with a bit of boost in the low frequencies (+2.5 dB at 20 Hz, +2.1 dB at 80 Hz) and a bit of attenuation in the high frequencies (-2.2 dB at 15 kHz); this looks somewhat like the curve that Harman has determined most people prefer because they perceive it to be flat.


Ray saved two profiles in which he tweaked the high end to follow the natural high-frequency rolloff of this speakers.


Here’s Dirac’s default subwoofer curve in Ray’s theater.


Ray likes more punch, so he created a subwoofer target curve with more bass boost.

We listened to several clips, including the opening scenes of the animated movie 9, The Police performing “Wrapped Around Your Finger” from the Certifiable live-concert Blu-ray, and The Eagles’ rendition of “Desperado” on CD, while switching between the four profiles Ray had created and engaging/bypassing the processor. In general, I preferred the processing engaged; without it, the sound was a bit indistinct and somewhat thin. The four profiles included the Dirac default, two based on the default that Ray tweaked (both following his speakers’ natural high-frequency rolloff, one with an extra 2.5 dB of bass boost), and a perfectly flat target curve from 20 Hz to 20 kHz. I found myself preferring the flat curve with its clean, crisp, well-defined sound, even though it didn’t have the low-frequency “punch” of the others.

The effect of the Dirac room correction was pretty subtle, especially with multichannel sources. With 2-channel music, it was more noticeable, but still not profound. Admittedly, this was a brief critical listen; Mark Henninger is planning a full review of the DDRC-88A, so stay tuned for that.

I thank Ray Coronado for hosting this shindig; it was great fun to hear the DDRC-88A and hang with some of the Los Angeles AVS Forum gang.

For much more discussion of the DDRC-88A, check out this “official” thread.