Music in the Round

PARC Place
With all that rah-rah about digital room EQ, it's too easy to forget that not every music listener has a digital processor, whether or not he or she listens in two or more channels. After all, you can get immense satisfaction from analog sources, or from a superb digital player such as the Esoteric DV-60 or Bel Canto PL-1A feeding an outstanding analog preamp such as the Bel Canto Pre6 or the Audio Research MP1. Even so, the room and its modes are still present, and analog solutions aren't so easily found. Sure, you can get an Audyssey Sound Equalizer, but if your system is all analog, I suspect you won't be happy about the necessary A/D/A conversions, even if I tell you that they're a tiny price to pay for the benefits.

Rives Audio's PARC series of analog parametric equalizers to the rescue. In July 2003 I reviewed Rives' Parametric Adaptive Room Compensation (PARC), which provided analog parametric EQ below 350Hz for a two-channel system. Subsequently, Rives offered the add-on PARC+ to extend PARC to six channels. Now they've released the ; see sub-PARC, which adds a 1200W power amplifier to a single-channel, three-band parametric EQ, crossover making it eminently suitable for use with a passive subwoofer ($5000). In short, the sub-PARC is a crossover and power amp. I didn't use the crossover function—my Anthem Statement D2 does that—and because I have only powered subwoofers, Richard Rives Bird sent along one of the new Talon ROC passive subs (Rives also owns Talon Audio).

The sub-PARC looks just like the original line-level PARC from the front, but on its rear panel are RCA and XLR input jacks for the left, right, and LFE channels, RCA and XLR output jacks for left, right, and subwoofer, and a pair of speaker terminals. Both the subwoofer jacks and the speaker terminals benefit from the parametric EQ settings, and all outputs can be subjected to the crossover and level controls. Also on the rear are a 12V trigger, RS-232, and power connections, along with an On/Off switch. Connections are pretty intuitive.

For programming the EQ filters, Rives includes a CD with test tones and a chart for the user to fill in with the measurements, using a calibrated mike or a RadioShack sound-level meter. The user then plots the system's in-room response and calculates the appropriate filters to compensate for the measured response peaks. This worked just fine, but I found it as tedious as I had while reviewing the original PARC in 2003. Rives acknowledges this, offering on their website other tools, including their own Bass and Room Evaluator (BARE), but in this day and age—and for $5000—I would have hoped that such a tool would be included. You must have the basic minimum SPL meter anyway; if you also download the Room EQ Wizard freeware mentioned earlier, you'll have a great toolkit. I took an easier way out: the handy, dandy XTZ Room Analyzer (see below).

In fig.1 mentioned earlier, you can see an XTZ display similar to what I measured with the sub-PARC and the Talon ROC sub replacing my Paradigm Reference Servo-15 subwoofer. XTZ recommended two filters: at 23Hz with a Q of 2.8 and a magnitude of –10.25dB, and at 41Hz with a Q of 5.7 and a magnitude of –8.75dB. I programmed these into the sub-PARC and ran the measurements again. Sure enough, the frequency response was now smoother in the 16–80Hz range, and there was a significant reduction in extended energy—but, surprisingly, XTZ now recommended a third filter, this one at 29Hz with a Q of 8.4 and a magnitude of –9.25dB. Well, sure—why not? (Remember, that popped up in the ARC results, too.) I programmed this third filter into the sub-PARC and again got that pop-up message, once surprising but now happy: "No modes detected!"

The sound was clean and tight and powerful, as I am coming to expect from a system in which the major room modes have been greatly mitigated. As for the integration of the Talon subwoofer's output with that of the main speakers, that, too, was excellent. But the ROC enjoyed an advantageous position up front, between the center and right main speakers, where, in general definition, it was pretty much the equal of the Servo-15 placed at the back of the room. For a while, I ran both subs. Even better.

However, the big advantage of the sub-PARC is that the signal never leaves the analog domain. All you guys holding the fort for analog systems no longer have an excuse. I can see the sub-PARC as a complement to any no-compromise two- or multichannel system that includes a subwoofer.

Easy as XTZ
By now you should have some idea of the uses of the XTZ Room Analyzer. The package consists of a USB-connected microphone, a heavy mike base with a USB-powered signal generator, cables, Windows-compatible software, and brief, illustrated manuals in English and Swedish. Plug the mike into the base, connect the base to a USB port on your laptop and, via the 25' interconnect and splitter (provided), to inputs on your preamp or processor, or directly to your powered sub. The XTZ program opens in its Basic room analysis mode, but because the Advanced mode has similar default values and greater capabilities, I see no reason why anyone wouldn't use the latter. Either mode has two graphic windows, the larger defaulting to frequency response, the smaller showing the spectral decay, but they are swappable. XTZ had no US distributor as of August 2008, but their products are available directly via their website. The Room Analyzer costs $320, including shipping to the US.

Across the top of the display is a drop-down toolbar that permits you to print the display, control the display of the toolbar and status bar, switch between the Basic and Advanced modes, and access a Help button (which was empty). On the right, under the smaller graphic window, are tables for the identified room modes and EQ profiles. On the extreme right are controls for performing the measurements, setting the test-signal levels, display (Measured, Modes+EQ, and/or Result), smoothing parameters for the display (2–6 points/octave), setting the post-stimulus time for the frequency display, and buttons to Store, Recall, Save, Export, Overlay, and Clear the displays.

On the bottom is the status bar showing the Time (ms), Frequency (Hz), and Magnitude (dB) represented by the position of your cursor as you poke around the graphs. Finally, two buttons switch XTZ from its time/frequency mode to a 32-band RTA mode (16Hz–20kHz). In the latter, you can monitor any signals coming from the system or measure the system's response to pink noise generated by the XTZ. Markers for minimum/maximum readings are provided, along with numerical readings for each band to supplement the dancing bar graphs. For the RTA mode, XTZ recommends pointing the calibrated mike directly at the source; the mike becomes directional over 1kHz.

To run the room analysis, you prepare by reorienting the goose-necked mike to point directly up before clicking Measure. XTZ then asks if you want to use one measuring position or three. I used one mike position for quick checking when adjusting speaker positions, for example, but for better room information, XTZ advises using three. You are then prompted to move the mike to each position, left/center/right, before the XTZ emits three or four low-frequency sweeps at (in my experience) a correct, automatically adjusted level. (There is a level control.) After a few seconds of calculation, XTZ provides both the frequency response (at 0ms) and the spectral decay, as well as, in the upper table, a list of the detected modes and the suggested EQ.

I always swapped the spectral display into the big window for several reasons. First, the data richness benefits from the enlargement. Second, I can grab the vertical line in the big window (set by default at 50ms) with the mouse and move it to overlay the frequency response at any post-stimulus time on the 0ms response. Third, I can overlay the response of the recommended filters (as well as any I want to insert) and add the predicted corrected response in the frequency-response window. Neat stuff.

This is all very easy to do. Even better, it's extremely useful. The modes identified by XTZ correlated very well with the peaks shown in the frequency-response graphs provided by Audyssey's SEQ and Anthem's ARC, and, as explained above, the recommended filters did a dandy job when programmed into the sub-PARC. I haven't yet tried this, but there's every reason to think that those filters would be equally effective with other hardware, including the Velodyne SMS-1 (see www.stereophile.com/musicintheround/1105mitr), which, for all its sophistication, doesn't measure or display any time/decay information. But why stop there? If you have a parametric equalizer, the XTZ can be the tool you need to program it more usefully than with only frequency- and magnitude information. Sure, there's nothing here that you can't do (and more) with Room EQ Wizard, ETF/R+D, TEF, and a slew of other great tools. On the other hand, XTZ's Room Analyzer is so easy and intuitive to set up and use that it should appeal to anyone intimidated by those other programs, as well as to the just plain lazy, such as I. Remember what I said about XTZ's Help button? No help is provided, but then again, none is needed.

Erratum
Reader Matthew Freilich writes that, in the July 2008 "Music in the Round," I erroneously stated that "While most Blu-ray machines can also play CDs and standard-definition DVDs, none include SACD among the 'legacy' formats supported." He adds that "Sony's PlayStation 3 plays SACDs, and while it may not be the best choice (or even a good choice?) for an SACD player, it is still one of the most popular Blu-ray players on the market." He is, of course, correct. My only excuse for the error is my general ignorance of and lack of attention to video gaming.

Next Time in the Round
There are speakers, players, and another subwoofer equalizer on the horizon, but the CEDIA Expo, upcoming in early September, will likely determine the priorities for the next column, scheduled to be published in the January 2009 issue.

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Footnote 1: At the moment, neither Anthem's ARC nor Audyssey's SEQ permits the user to add his or her own filters to the determined equalization, so I couldn't attack that 70Hz plume. However, Audyssey announced that in September, at the 2008 CEDIA Expo, they planned to release v3.0 of the Pro software, which will include such capability in addition to other new features. Given Anthem's demonstrated ability to rapidly enhance their software, I wouldn't be surprised to see a similar feature appear in ARC.