Automated room correction is an essential component of modern home theaters and AV rooms. At their most basic, such systems set speaker distances, levels, and crossover points for bass management. More sophisticated solutions try to tackle peaks and nulls in the bass region, phase-related issues, group delay, and other acoustical anomalies.
Some companies license their room-correction solutions to hardware manufacturers—Audyssey, Dirac, and Trinnov are three good examples. Additionally, there are proprietary systems from various manufacturers—Yamaha has YPAO, Pioneer offers MCACC, Sony calls its system DCAC, Anthem features ARC, Krell's is called ARES. There are quite a few different systems out there.
Dirac Live is a particularly sophisticated room-correction system that offers flexibility and ease of use. Datasat and ThetaDigital use it in their high-end cinema and audio processors. Emotiva offers it in the XMC-1 pre/pro as a $100 extra. There is also a version of Dirac Live that runs on a PC or Mac; it costs $435 for stereo processing or $730 for the multi-channel version. Furthermore, luxury automakers BMW, Bentley, and Rolls Royce use Dirac's technology to improve the sound inside their cars.
Dirac Live is also available in dedicated processors made by miniDSP. The company is known for its broad line of affordable DSP solutions for music and AV fanatics. This review is about the DDRC-88A, a $1000 Dirac Live processor that is inserted between a pre/pro's or AVR's preamp outputs and a separate amplifier's inputs.
The DDRC-88A is an 8-input/8-output standalone DSP. It offers balanced and unbalanced analog inputs and outputs, and it digitizes audio at 24-bit/48 kHz resolution.
It's a relatively compact device that is rack-mountable and takes up one rack space. It measures 1.6" (H) x 16.9" (W) x 10" (D). To fit both balanced and unbalanced connections on the back, the balanced connections use bare-wire terminal blocks, while the unbalanced connections are standard RCA-type. There's also a USB port for use with the configuration software.
A close look at the rear panel of the DDRC-88A.
A knob on the front lets you select one of four presets and adjust the volume. That's all there is to the DDRC-88A's functional, industrial design.
The central feature of the DDRC-88A is Dirac Live room correction, which requires two additional pieces of hardware: a computer and a calibration microphone . The software, which handles the measurement procedure, is designed to work with miniDSP's UMIK-1 microphone, which costs $70 extra.
Dirac Live software lets you customize room-correction parameters to your specific needs, but you don't get to tweak things like delay and speaker levels—Dirac Live takes care of that behind the scenes. You do get to tweak the frequency range Dirac processes, and you have control over the response curve.
Furthermore, you can use the channels independently in a multizone system. For example, you could use it to process audio for four stereo pairs, each with its own set of correction parameters. Another option is a two-zone configuration with 5.1 surround plus a separate 2-channel rig.
Setting up the DDRC-88A involved connecting the unit to the preamp outputs of a processor—in my case , a Pioneer EliteSC-85 AVR—and the inputs of an amplifier (I used a Crestron Procise 7x250) as well as connecting it to a PC or Mac with a USB cable. A wall wart provides power.
As I mentioned earlier, the DDRC-88A offers unbalanced RCA and balanced terminal block (bare wire) connections, and it's best to choose one or the other. The balanced and unbalanced outputs operate in parallel; both are always on. Please note, you must pay attention to the gain structure of the signal chain if you mix and match balanced and unbalanced connections. For this review, I used the unbalanced inputs and outputs.
After connecting the hardware, I downloaded the necessary software and instructions from miniDSP's website and configured the DDRC-88A. You need two apps to use the device: Dirac Live Calibration Tool and DDRC-88A Utility.
Before launching the Dirac Live Calibration Tool, I checked the firmware version and reset the unit to system defaults using the DDRC-88A Utility, which also reveals the activation serial number for Dirac Live, so you have to run it first. While running the utility, you can program the DDRC-88A to understand infrared commands from various remotes to adjust the master volume, select presets, and turn processing on and off.
You can program the DDRC-88A to recognize IR remote commands.
Once I finished with the DDRC-88A Utility, I moved to the Dirac Live Calibration Tool application. Before getting started, it's a good idea to set up the AVR or pre/pro to work with the DDRC-88A. That means setting all speaker levels to 0, setting speaker delay/distance to the same number for all channels, turning off all EQ and room-correction features, and choosing a crossover point for your subwoofer if you plan to use a sub.
The calibration process is relatively straightforward. The software has an easy-to-understand interface that illustrates what to do step by step and includes verbal instructions. If that isn't enough, AVS has a very active thread dedicated to the DDRC-88A that includes direct links to setup instructions in the original post.
The first step in the setup process is choosing a speaker configuration. I opted for 7.1 channels, the maximum the DDRC-88A can handle. It's worth noting that currently, the unit offers processing for only one subwoofer channel. That may change in the future, but for now, if you use multiple subwoofers , you have to synchronize their phase.
One way to deal with subwoofer timing is to use a signal splitter and keep the subs an equal distance from the listening position. If you want more flexibility in positioning, you can attempt to integrate the subs using variable phase controls, or employ another device to split the signal and handle delay. For example, some AVS members use a miniDSP 4X4 just to manage multiple subs. I used a Crestron PSPHD pre/pro to handle subwoofer
timing, it has three outputs with adjustable delay.
The DDRC-88A is slender and minimalist. It fits in a single rack space.
Another complaint about using a separate device to manage multiple subs is that it introduces a second round of conversion from analog to digital to analog again. I don't think that's an issue, but I'm sure some would argue otherwise. Regardless, if you use multiple subs, you must have a strategy to time-align them so Dirac Live can treat them as one channel. For this review, I used a Crestron PSPHD pre/pro as the sub splitter.
The next step is to choose the microphone (I used the UMIK-1) as well as a custom calibration profile matched to the mic's serial number. You can get the appropriate calibration profile—optimized for a vertical microphone measurement—from miniDSP's website. After making the selection, you set the microphone gain and the DDRC-88A's output volume to optimum levels—the program provides instructions of how to do so. Then, you proceed to the measurement screen.
At this point, you need to choose which measurement pattern to use. There are three options: chair (for a single listener), sofa (self-explanatory), and auditorium (for multiple rows). Thanks to the four memories in the DDRC-88A, you can make multiple profiles and choose them according to how focused you want the room correction to be. An audiophile who sits in the sweet spot will want to go for the chair option, while a home-theater owner might switch between all three correction types depending on whether they are alone, with a friend or two, or in a theater full of people.
While the system is taking readings, you can see the resulting waveform rendered on the computer screen . Dirac Live takes readings for each speaker from nine different locations. The first reading is always taken from the precise center of the sweet spot. You take the remaining readings by placing the microphone at various locations following a pattern illustrated in the calibration software.
Here's the measurement screen when using the sofa pattern.
Once the measurements finish, the tweaking begins. The next screen in the Dirac Live Calibration Tool lets you control how much of the audio spectrum is processed and adjust the EQ curve. The bottom line is that you can tweak Dirac's room correction to suit your taste. Whether you like your audio bass heavy and your treble untouched, or you seek a classic house curve similar to what's used in screening rooms and studios, you can dial it in using a simple graphical interface.
Using the graphical tools in this screen, you can tweak Dirac Live's processing.
Audiophiles will appreciate the ability to restrict corrections to the bass region—where room reflections have a significant effect on overall frequency response—while leaving the midrange and treble untouched. Home-theater enthusiasts will appreciate being able to generate a linear response curve for all speakers in the system with compensation for timing, output level, impulse response, and timbre.
The last screen in the calibration tool allows you to save completed profiles to one of four memories in the device. You can also use the utility to swap out existing profiles—you can store as many as you wish on a PC.
Because room correction is a rather common feature of many AVRs and pre/pros, Dirac live has to offer tangible benefit compared with competing systems. Otherwise, why would you bother using it?
Let's cut to the chase. Dirac Live is the best room-correction solution I've heard. It quickly went from being a curiosity—I let the DDRC-88A sit on a shelf for several months, untouched—to an absolute necessity. I was blown away from practically the first moment I added it to my system! I had read the hype in the forums, but I was not ready for the boost in fidelity it delivered.
Subjectively speaking, I loved the way Dirac Live made the soundfield more cohesive and the speakers more transparent. I found it easier to localize individual sound objects during movies and instruments when listening in stereo. Bass seemed much tighter, with greater extension and less boominess—almost as if I'd upgraded all the subs.
While I could describe how good the Dirac Live-enhanced system sounded with some select albums and movies, ultimately this review is not about my subjective listening impressions. When I publish my review of the Klipsch Reference Premiere speaker system later this week, I'll describe what it was like to listen to specific albums and movies. This review about the measured effect of Dirac Live on a Klipsch Reference Premiere 7.1-channel speaker system—in other words, how it handled a seriously heavy-hitting speaker system in my listening space.
For surround processing, I use a Pioneer Elite SC-85 AVR, which features the company's MCACC Pro room-correction system. It claims to address many of the same issues as Dirac Live, and in its latest iteration, it offers subwoofer EQ for two different subs. Nevertheless, to my ears, Pioneer's built-in system paled in comparison to what the DDRC-88A offers thanks to Dirac Live.
I achieved beyond-satisfying results using the DRC-88A with a Klipsch Reference Premiere surround system featuring RP-280F tower speakers, twin R-115SW subs, an RP-450C center, RP-160M bookshelf style speakers, and RP-250S surroundspeakers . In addition to the Klipsch subs, the system was augmented by dual JL Audio e112 subwoofers .
The studio I use for home cinema measures 11' x 19' x 9'. It has some sound absorption from carpeting and furniture, but no dedicated room treatments, and I've always had to use some EQ or room correction to get optimal results.
I measured each speaker in the system six times using Room EQ Wizard. The first two rounds of measurements involved no DSP, room correction, EQ, or even level matching. Round one measured all the speakers individually, full range. Round two was the same except that the subwoofer was integrated with each speaker using a 100 Hz crossover.
My room is far from perfect. Measuring full-range, I saw peaks and dips measuring up to +/-10 dB (1/6 octave smoothing) from the front speakers in the deep bass region, which is most affected by room modes. In the upper bass and midrange, I saw up to +/-4 dB swings in the measured response. Notably, the treble response was nice and smooth. Adding a subwoofer and engaging the crossover, linearity improved to +/-7 dB in the low frequencies.
Armed with the data
from the first two rounds, I proceeded with a full MCACC Pro calibration, using the "All Channel Adjust" mode. I placed the Pioneer calibration mic right on top of the tip of the UMIK-1, so it could calibrate the system from the exact spot I took Room EQ Wizard measurements.
All Channel Adjust is the MCACC mode most akin to Dirac Live in that it applies full correction to each speaker individually, and it also EQs the sub. Running MCACC produces a wide variety of bleeps, sweeps, and clicks. It performs measurements for each of its functions separately—levels, distance, EQ, standing waves, group delay—and each has a distinctive sound effect.
When MCACC wrapped up, I looked at the settings it chose. It thought all the speakers in the system were full-range—way to go Klipsch ! I proceeded to a second round of measurements using Room EQ Wizard following the same procedure—first full range, then with bass management and a 100 Hz crossover.
With MCACC's help, I saw a marked improvement in the full-range frequency response. For the front channels, I measured a maximum deviation of +/-7 dB in the bass region, and a maximum deviation of +/-3 dB above 130 Hz. Adding bass management to the mix brought the deep bass response to within +/-6 dB tolerance, while higher frequencies remained at +/-3 dB deviation.
Finally, I performed a fresh calibration using Dirac Live's sofa pattern. For the all-important first measurement, which is used to calculate speaker levels and distance, the UMIK-1 was in the exact spot used for the REW measurements. I marked that position so I could return to it after the Dirac calibration finished.
Once Dirac finished measuring—it only takes one sweep per speaker for each of the nine positions—I optimized the results (i.e., hit a button labeled "optimize") and used the default house curve suggested by the software. I saved the settings in the DDRC-88A, exited the calibration software, and launched Room EQ Wizard.
While Dirac Live shows you nifty graphics that illustrate what a good job it did, I wanted to compare the measured results using Room EQ Wizard. I performed two more rounds of measurements following the same procedure as before, first measuring everything full-range, then applying bass management.
The results were stunning to look at. No wonder Dirac Live sounds better than no processing or MCACC Pro. It did a far better job than MCACC Pro at making the system's response linear. In the full-range measurement of the front channels, the only real glitch was a very narrow dip in response centered around 88 Hz and measuring -10 dB. The rest of the curve stayed within +/-2.5 dB.
Finally, adding bass management to the system and processing the result with Dirac Live produced the best readings of all. The front channels stayed within +/-3.5 dB in the bass region, and +/-2.5 dB from 130 Hz on up. You really can't ask for much more from a room-correction system; it delivers linearity on par with the anechoic measurement specs of many speaker systems—incredible.
When I listen to the system with Dirac Live and then switch to MCACC Pro, I'm reminded of why my first encounter with Dirac was so memorable. It elevates the whole system, much more so than any other $1000 investment I can think of—as long as you've already got some good gear. The effect of a room is an overwhelming element in any system. The degree to which Dirac Live takes the room out of the equation sets it apart from any room-correction system I've heard in the past. I consider it a must-have.
Now, I know some of you are going to ask how Dirac Live compares to Audyssey MultEQ XT32, and I do not currently have an answer. I know both systems are capable of highly accurate correction, and both methods use clustered measurements to create a correction profile that works within a particular pre-defined zone—an expanded sweet-spot, so to speak. If I can get my hands on such a system, I'll reference this review when I write about it.
I am far from done exploring Dirac. The ability to tweak the curve and select the frequency range to be processed offers near-limitless possibilities. For 2-channel speaker reviews, it lets me run speakers full range while only correcting for room modes, so the "character" of the speaker doesn't get EQ'd away—a frequent criticism of room correction is that it tends to make all speakers sound alike.
As awesome as the DDRC-88A is, I do have a few gripes. With only eight channels, the DDRC-88A can handle up to a 7.1system . I have 5.1.4 Atmos capability, and I would have liked to use Dirac Live to correct all 9.1 channels. Also, Dirac Live desperately needs the ability to handle more than one subwoofer channel. If you have a system with multiple subs and more than seven speakers, one DDRC-88A simply isn't enough. I'd love to see a 16-channel version in one chassis.
Now that I've gotten my hands dirty with Dirac, you'll find me in the same place as any AVS member who has discovered the magic box known as the DDCR-88A: The miniDSP DDRC-88A Official Thread . As I measure speakers for reviews, I'll share my pre and post Dirac charts. Unless something better comes along, it is going to remain an integral part of my system—it's that good.
DIY PC ( Windows 8 ) running Tidal and iTunes
Oppo BDP-103 Blu-ray player
Amplification and Processing
Pioneer Elite SC-85 AVR
Crestron Procise PSPHD pre/pro
Crestron Procise ProAmp 7x250
MiniDSP DDRC-88A Dirac Live processor
Monoprice 12-gauge OFC speaker cables
Monoprice 1.5-foot premium stereo RCA cables (8)
Mediabridge Ultra Series subwoofer cable (4)
Mediabridge Ultra Series HDMI cable (2)
Speakers and Subwoofers
Klipsch RP-280F towers (2)
Klipsch RP-450C center
Klipsch RP-160M bookshelf (2)
Klipsch RP-250S surround (2)
Klipsch R-115SW subwoofers (2)
JL Audio e112 subwoofers (2)
Vizio 65" M65-C1
Samsung 64" PN64F8500