Music in the Round #64 Page 2

Most miniDSP devices can be purchased as functional boards or housed in chassis. In the interests of efficiency, I opted for the latter and chose the 10x10Hd, because it can be used as a multichannel equalizer with both analog and digital inputs and inputs. At an appealing $599 including the 12V power supply (plus $10 for the 10x10 plug-in firmware), the 10x10Hd has eight analog inputs and outputs (both balanced and unbalanced), and a stereo digital input and output (TosLink, S/PDIF, AES/EBU). It also has a USB port for connecting to a Windows PC or Mac, which runs the plug-in.

Once you've synced your computer to the 10x10Hd, you can set up high- and low-pass filters for each output channel—including up to eighth-order Butterworth and Linkwitz-Riley, and second-order Bessel—in increments of 1Hz. You can control gain, phase, delay, and compression for each output channel (fig.1). These active filters are suitable for driving the individual amps for multidriver speakers and for bass management. You can also implement up to six parametric EQ filters (peak or shelf) per input and/or output channel (fig.2); these can be set up by entering the frequency, gain, and Q values, or by importing biquad filter sets. Between the input and output screens, there is a 10x10 cross-point matrix that lets you route any of the 10 input channels to any of the 10 output channels (fig.3), including mappings that permit, for example, derivation of multiple subwoofer outputs with mono or stereo or multichannel sources. The routing can be monitored on the PC screen, and all of these options can be selected and stored in up to four independent configuration presets. Once configured, the hardware platform does not need to be connected to the computer as all the settings are stored in memory.

114mitr.Roundfig1.jpg

Fig.1 The miniDSP's "Outputs" screen shows all the options for the Config selected at the top: signal monitor, level set, mute, polarity, delay and access to submenus for crossover, parametric EQ and compression. I found uses for all but the last.

114mitr.Roundfig2.jpg

Fig.2 The miniDSP PEQ screen shows the frequency response of the correction filters for a chosen channel, the parameters of one filter selected from the list and other options. The "Select Channel" dropdown menu lets you clone these operations to another channel.

114mitr.Roundfig3.jpg

Fig 3 The miniDSP's processing options for the inputs and outputs and, between them, a 10x10 switch matrix that links them and permits any source to be connected to any (or all) outputs. This includes both analog and digital inputs and outputs.

Sound complex? Nah. Just follow the instructions. I used the six RCA outputs from my Oppo BDP-103 universal Blu-ray player as inputs, and fed the 10x10Hd's six analog outputs to the multichannel analog inputs of my Marantz AV-8801 preamplifier-processor. With the Oppo off and the Marantz muted, I connected the 10x10Hd to my laptop via USB, and opened the plug-in software I'd downloaded from miniDSP. I accessed the input page and made sure that all the channels for Config 1 were at nominal full gain and that all filters were off. I then switched to the routing page and mapped the six (5.1) inputs to the six outputs, and the S/PDIF stereo inputs to their matching outputs. Finally, I moved to the output page for Config 1 and repeated what I'd done for the inputs. Then, when I hit the Sync button, the plug-in found the 10x10Hd, downloaded the settings, and I was ready to un-Mute the Marantz. (The miniDSP has a reputation for powerful on/off transients. I was careful with power sequencing, generally left the unit on, and experienced no problems.)

114mitr.minidspbac.jpg

My initial impression was of an open, spacious sound with no apparent loss of resolution and no hint of noise, despite the fact that the 10x10Hd needs to operate at 24/48 with this plug-in (though it can operate at 24/96 when running fewer channels). Sound familiar? I learned from this that the signal path through the 10x10Hd does not, by itself, impose a fingerprint on the sound. I repeated this setup with the other three configurations and saved them on my laptop. This was necessary because my initial test of the signal through the 10x10Hd sounded weird. I found out that, even though I used Restore for the factory defaults, there were residual filters and level settings instead of a blank canvas.

Now for the fun. I needed to load something useful into the 10x10Hd, and that proved surprisingly easy with REW or OmniMic (see below), both of which can now generate biquad filter files, which the 10x10Hd can read. Using OmniMic V2 or REW with miniDSP's UMIK-1 USB microphone ($75), I took single-point and averaged measurements, calculated the biquad filters, and loaded them into the output parametric EQs of different Configs in the 10x10Hd. I also inserted the usual level and delay settings for my system, and set up bass management (using cross-point switches and high-pass/low-pass filters), before disconnecting the USB cable to the computer. Over time, I A/B'd the different equalizations I'd stored, using the front-panel controls, and decided that each made different improvements in the sound, but also imposed different shifts in tonal balance.

With the laptop reconnected and synced, I examined the filters, Config by Config and channel by channel. With the ability to edit the filters while listening, I turned individual filters on and off and determined that 1) all filters above 400Hz, cut or boost, would be deleted because they just sounded bad; and 2) some of the lower-frequency boost filters were reduced or eliminated. That really did clean up the low end, and made the midrange soundstage deeper and more discrete, but at the price of being a little light at the bottom end compared to the Audyssey-equalized sound offered by my Marantz AV-8801.

No matter—the10x10Hd had more up its sleeve. Switching to the yet-unused parametric EQs at the input, I worked up a "house curve" with a gentle bass lift from 120Hz down, and a very gradual rolloff from 120Hz to 20kHz. The result was eminently satisfying with all sorts of music, regardless of the number of channels, and with modal decay times greatly reduced.

I am a convert to the miniDSP 10x10Hd. It performed as advertised, and my criticisms are minor. First, my aging eyes were strained by the small size of the plug-in's nonadjustable display windows, which filled only about a third of my laptop's screen. To get through the setup sessions, I had to connect my plasma screen. Second, I would be happier if the signal were throughput at 24/96, not 24/48, though this would easily double the required DSP power. Third, miniDSP doesn't offer a multichannel digital input/output version that would finesse the limitations of an additional ADC/DAC process, but there is no simple solution for this. The price of licensing HDMI is high, and HDCP (High-bandwidth Digital Content Protection) constraints (back to 24/48 again) and multi-S/PDIF are far from a standard.

But the miniDSP 10x10Hd gave me the tools to do what I want in order to get the sound that I want. The 10x10Hd makes it easy to look under the hood of room EQ. So does the $13,000 Trinnov MC Processor, which—with its spatial remapping, multi-microphone pod, professional construction, and higher resolution—remains unchallenged. Still, at less than 5% of the Trinnov's price, the miniDSP 10x10Hd is a killer deal.

Audio Measurement Goes Multichannel
For a while now, I've been frustrated by the acoustical measurement tools I've tried because all of them operate, essentially, only monaurally. That's reasonable—one always begins by measuring one channel at a time—but as systems have become more complex and some have begun eliminating analog inputs, one needs to do lots of plugging and unplugging in order to get the test signals into each channel. It has sometimes deterred me from being as scrupulous as I would like to be.

That has changed. Two of the most popular and powerful measurement programs, RoomEQ Wizard (REW) and OmniMic, are now multichannel friendly.

REW continues to evolve in sophistication and utility. Version 5.10 supports HDMI output for the test signals, but none of my PCs would allow me to map that output to any particular channel other than FL or FR. However, I found that installing ASIO4ALL, offered as a universal ASIO driver for WDM (Windows Driver Model) audio, provided a solution (footnote 1). When ASIO4ALL is selected as the output driver in REW's Preferences page, one can select any of eight channels for output. With my laptop, the channels were numbered 1 through 8, but it was trivial to identify each one. Using this driver, it was a snap to choose any channel or pair of channels to test with REW.

OmniMic V2 boasts greater accuracy than the original edition, and a more robust USB connection. The current software, v.4, can output biquad filter sets, in addition to frequency, gain, and Q. However, since OmniMic gets the test signals to the system from a disc, the availability of Daytona Audio's new multichannel OMDVD Version 1 Test DVD gives users the ability to access all necessary stimuli for each individual channel from its OSD menus. The DVD costs only $25.99, and might be useful for other measurement tasks, as well.

This is real progress.

Next Time in the Round
I return to the mainstream with Yamaha's first new pair of multichannel components in a long while: the 11.2 channel AV preamplifier CX-A5000 (with ESS Sabre32 DACs); and the companion MX-A5000, an 11-channel power amplifier.



Footnote 1: I understand that there's a similar driver for Macs, called Soundflower, that supports 16 audio channels via HDMI.
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