Rives Audio PARC
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| Condition | |
| Payment methods |       |
| Ships from | Los Angeles, CA, 90077 |
| Ships to | United States and Canada |
| Package dimensions | unspecified |
| Shipping carrier | UPS |
| Shipping cost | Free |
| Original accessories | Box, Manual |
 Average | Research Pricing |
Rives Audio Parc Subwoofer parametric EQ..............
ROOM TREATMENT REVIEWS
Rives Audio PARC 3-Band Parametric Equalizer
Kalman Rubinson | Jul 20, 2003
Last January, the Stereophile website conducted a poll asking readers what they thought was their audio system's weakest link . The results indicated that 24% thought that their room was the most problematic component. What this says is that, though often accused of being obsessed with hardware, we audiophiles are aware of what a potent effect the speaker-room setup has.
Sure, it's easy (except for cost) to try different components or interconnects, even speakers—but room arrangements immediately invoke the Spouse Acceptance Factor and other domestic concerns. How often have you had to explain why the speakers can't go against the wall, or why it's necessary to put sound-absorbing materials in specific places? Unless one is so fortunate as to have a dedicated listening room, such fights are usually settled by compromise and concession. At least 24% of us are dissatisfied, unable to wring further concessions from those with whom we share our space. More panels and Tube Traps? Not options.
Along comes Rives Audio, a company focusing on small-room acoustics and related services, with its Parametric Adaptive Room Compensation, or PARC: a sophisticated analog parametric equalizer (footnote 1) that purports to accomplish significant low-frequency correction of room modes. By restricting its responsibilities to the 16-350Hz band, by using attenuation only, and by dint of its design and construction, Rives intends the PARC to be used in systems of the highest quality.
As I wrote in a Sidebar accompanying my review of the TacT RCS 2.0 Room Correction Processor in September 2001, a simple amplitude correction of room effects with an analog EQ cannot, in theory, suffice—any attempt to correct the room-influenced late response will also modify the speaker's on-axis direct response. In addition, many audiophiles have sworn off analog EQs, graphic and/or parametric, along with tone controls, since they introduce distortion, noise, and phase shifts. Despite this, such amplitude/frequency EQs are fairly common in recording studios and other sites.
What's the problem?
The basic issue is that, aside from room decoration and acoustic treatment, the very dimensions of our rooms support resonances. The physics start out pretty simple: A dimension will support a standing wave at a frequency whose wavelength is twice that dimension. Already, that means there is one standing wave for each of the three primary room dimensions. The room can also support frequencies related to each of its diagonal dimensions, so add three more. In addition, each of these dimensions will also support, albeit to a slightly lesser degree, all frequencies that are even harmonics of their basic resonant frequencies.
Of greater significance is that, when one of these fixed room dimensions is the same as or a multiple of another, the resonant frequencies they have in common are reinforced. These combined interactions then create sites (nodes) in a room where certain frequencies are greatly enhanced, as well as sites (nulls) where certain frequencies are greatly canceled. Such are the underlying reasons for designing listening rooms with nonparallel surfaces (to distribute the resonant frequencies for that dimension) and dimensions that are not multiples of each other (to minimize the summing of resonances).
How does this analysis help us? First, it can tell us what frequencies need attention. Second, it suggests how to attack those frequencies. High frequencies can be absorbed, diffused, or diffracted with materials that, with care and luck, can be disguised to promote domestic tranquility. That will not do for low frequencies, which would require devices of much greater size. Moreover, as Richard Rives Bird reminded me, even a relatively large and efficient bass trap occupies only a small portion of a room's area and surface. However, at these low frequencies, electronic EQ can be implemented without introducing significant distortion or noise in the midrange, where the ear is most sensitive.
That, in short, is why Rives restricts PARC's correction to between 16 and 350Hz, the range corresponding to room dimensions of between 35.3' and 1.6'. Dimensions greater than 35' would affect sub-audible frequencies and their audible harmonics above 16Hz, while dimensions shorter than 1.5', such as in a closet or cupboard, would affect higher frequencies and can be dealt with in other ways.
Footnote 1: Unlike a conventional graphic equalizer, that has bands that are fixed regarding both their width and center frequency, a parametric equalizer allows control of both band width (Q) and center frequency.—John Atkinson
NEXT: Page 2 »
ROOM TREATMENT REVIEWS
Rives Audio PARC 3-Band Parametric Equalizer Page 2
Easy as PARC
The PARC is a three-band, two-channel parametric equalizer whose front panel clearly reveals what it is and what it does. Above each control is an indicator LED or a numeric readout of its status. Beginning on the left, the first button, Display, toggles the display of the numeric readouts without affecting any other functions; you don't need that bright, bold display when you've finally set the device to your liking. Next are Save and Memory, which permit you to store and recall settings in any of three nonvolatile memories.
The Channel button selects whether the left or right channel is being adjusted, and Band selects which of the three available bands is being set. The next six buttons determine how that band is configured: The Frequency Up/Down buttons select a center frequency, the Width Up/Down buttons select the Q factor or width of the attenuated band centered on that frequency, and the Attenuation Up/Down buttons select the magnitude of the attenuation. (Unusually, only attenuation is offered, not boost.) Finally, the very useful Bypass button permits you to A/B the PARC's EQ'd and flat responses.
The rear panel is fairly symmetrical, centered around an IEC power socket, power switch, and fuse panel. Above those is an RS-232 comm port for computer communication, and a six-pin XLR for expansion of the two-channel PARC with a four-channel PARC-Plus to make a six-channel system. On either side of the central facilities are the left and right input/output facilities. Each of these consists of XLR and RCA inputs and outputs and an XLR/RCA toggle switch to select between the inputs. Both XLR and RCA outputs are always active when the PARC is powered up, but with power off, the audio signals will pass through from RCA to RCA and from XLR to XLR regardless of toggle setting.
In order to use the PARC, one could, of course, measure the room dimensions and calculate all the fundamental frequencies and overtones...but that way lies madness. You can model your room and speakers with CARA, or try one of several online calculators that are useful for planning. However, as the speakers' effective room interaction is greatly influenced by placement and by everything else in the room, I thought direct response measurement would be definitely better for this review.
One approach is to use computer analysis of calibrated pulses, such as ETF. PARC has a similar associated component, the Bass And Room Evaluator (BARE), which will do this quickly and efficiently, but it's still in beta stage and requires a PC, a microphone, and another $100. However, Rives supplies a simple alternative with the PARC: a test CD with tones for a calibrated meter, and another set of tones corrected for use with the ubiquitous RadioShack SPL meter. The latter approach is tedious, BARE (or ETF) being much easier, but I did get comparable results from the CD and from BARE. Such convenience, and the ease of re-measuring the response after correction to confirm the settings, make me hope that Rives will decide to bundle the finished BARE into the PARC package.
After measuring the response of each speaker, Rives advises finding the room's three major resonant peaks in the response below 350Hz. The PARC manual states that "the purpose is to reduce the frequencies caused by room excitation" (footnote 2). Following the manual's clear guidance, you calculate and enter the magnitude and width of each peak into the attenuation and Q settings of the parametric filter. Simple arithmetic, really, and a calculator is a useful luxury. Rives suggests entering the flattest response into Memory 1 and using the other memories for "tailored" responses. Other uses for the additional memories might be for particular sources (nah, none of us have rumbly turntables), alternative speakers, or alternative speaker and/or listener positions.
PARC Place
When Richard Bird delivered the PARC, I had just restored my Revel Ultima Studio loudspeakers to my main system. Though somewhere in the vicinity of their old sweet spots, they were not carefully positioned. They imaged well and had good midrange presence, but were a little lumpy in the bass—which, of course, made them prime candidates for the PARC treatment. The PARC was wired into the system between the Sonic Frontiers Line-3 preamplifier and Power-3 power amps with a short length of AudioQuest Python Balanced interconnect to supplement the normal long run.
The BARE facts confirmed the lumpy bass in both channels (figs.1 and 3). Note that the frequency scale of these graphs is linear, not the logarithmic scale usually used in Stereophile, so the peak at 32.7Hz in the left channel (fig.1) looks much narrower relative to the others than it otherwise would. As you can see from the chart below, its Q is actually lower than the peak at 350Hz but slightly higher than that at 134Hz. Similarly, the three peaks in the right channel (fig.3) appear, in this linear scale, to be similar but have substantially different Qs. Remember, Q= (center frequency) / (peak width at -3dB).
Fig.1 Rives PARC, uncorrected response of left channel from BARE. Peaks can be seen at 32.7Hz, 134Hz, and 340Hz.
Fig.3 Rives PARC, uncorrected response of right channel from BARE. Two peaks can be seen flanking 35.3Hz and single peaks at 84.5Hz, 211Hz, and 302Hz.
Footnote 2: Since the PARC can only attenuate, not amplify, it can deal only with resonant peaks, not resonant nulls. Rives argues that this is a conservative and parsimonious approach that is less likely to lead to garish abuse than would ill-applied amplification. It can also be argued that the resonant modes will still store energy, even with attenuation, smearing the transient performance of the system, and that a comparable gain-correction of nulls is likely to have less of an effect on transient performance. Thus, aside from keeping us from abusing the PARC or exceeding power limits for the amp or speaker, I can think of no theoretical justification for not offering some null correction. Richard Bird tells me that the PARC hardware is capable of applying gain, but that the current software does not. They are considering a software modification to permit a small amount (up to 6dB) of gain.—Kalman Rubinson
NEXT: Page 3 »
Rives Audio PARC 3-Band Parametric Equalizer Page 3
| Channel | Frequency (Hz) | Q | Attenuation (dB) |
| L1 | 32.7 | 1.9 | 10.0 |
| L2 | 134 | 1.1 | 5.0 |
| L3 | 350 | 5 | 1.4 |
| R1 | 35.3 | 1.4 | 4.0 |
| R2 | 84.5 | 3.0 | 3.0 |
| R3 | 211 | 4.4 | 3.8 |
Fig.2 Rives PARC, corrected response of left channel from BARE. Note reduction in peaks and overall lowering of average bass levels.
Fig.4 Rives PARC, corrected response of right channel from BARE. Note reduction in lower three peaks.
PARC Listening
With the PARC set to Bypass, its audible effect was vanishingly subtle. In either the recommended setup (between preamp and power amp) or the alternative setup (in the tape monitor loop), the difference between Bypass and straight-through with filters nulled was insignificant. In its active role, with filters set below 400Hz, the PARC was completely transparent in both the critical midrange and the revealing treble range. The high frequencies did seem a little brighter, in comparison with removing the PARC from the signal path, but this was probably the psychoacoustic concomitant of the improved, unmuddied bass. Way down, in the room-mode-vulnerable lower midrange and bass, the PARC was changing the sound, as was intended.
There were two ways to hear what the PARC did. First, I chose the deep male voices of Thomas Hampson and David Johansen (or any male WQXR announcer), and listened while switching the EQ in and out. With PARC EQ, the voice was always firmer, better defined harmonically and spatially, and easier to distinguish musically. Considering the corrections in the 200-350Hz range, this is not surprising.
To hear what the PARC did further down, I listened to Ray Brown's double bass on his classic Soular Energy album. The PARC maintained the powerful plucking with equal force and shape, despite attenuating rather than boosting any of the relevant frequencies. By fiddling with the controls, I found that the upper-bass corrections had a greater ameliorative effect than the lowest ones, even though the instrumental fundamentals were quite a bit lower. This is probably due to the ear's sensitivity dropping off at the very lowest frequencies and to the bass fiddle's harmonic richness.
One curious observation with Soular Energy was that the PARC corrections were both more effective and more appreciated with the analog signals from the DVD-Audio (HiRes HRM 2011) via the Meridian 800/861 DVD-Audio player, or the SACD (Groove Note GRV 1015-3) via the Sony XA-777ES SACD player, than from the LP (Pure Audiophile PA-002(2)). Pure Audiophile's blue vinyl discs are simply spectacular, with potent, taut bass at relatively higher levels than from the digital media, with or without PARC. One might chalk that up to the fact that the PARC correction was not customized to my particular combination of turntable, tonearm, cartridge, and phono stage, which, I'd venture, is not completely linear. With other, lesser LPs, the PARC wrought the same transformations as it had with the digital sources.
ROOM TREATMENT REVIEWS
Rives Audio PARC 3-Band Parametric Equalizer Specifications
Sidebar 1: Specifications
Description: Parametric Adaptive Room Compensation (PARC) 2-channel, 3-band parametric equalizer. Center frequencies: 16-350Hz. Q: 1-10. Attenuation: 0-18dB. Three nonvolatile memory stores. Power consumption: 50W. Voltages: 100, 120, 220, 240 (selectable).
Dimensions: 17" W by 4" H by 12.5" D. Weight: 20 lbs.
Serial number of unit reviewed: 103.0102.
Price: $2800. Approximate number of dealers: 10.
Manufacturer: Rives Audio, The ATI Group, Suite A-1, 8301 Patuxent Range Road, Jessup, MD 20794. Tel: (800) 959-6553. Fax: (707) 276-3983. Web: www.rivesaudio.com.
NEXT: Associated Equipment »
ROOM TREATMENT REVIEWS
Rives Audio PARC 3-Band Parametric Equalizer Associated Equipment
Sidebar 2: Associated Equipment
Analog source: Heybrook TT2 turntable, SME III tonearm, Ortofon SME30H cartridge, VPI SDS Line Controller.
Digital sources: Meridian Reference 800/861 DVD-Audio player, Sony XA-777ES SACD player, Mark Levinson No.360S D/A converter.
Preamplification: Sonic Frontiers Line-3 preamplifier, Audiolab 8000PPA phono stage.
Power amplifiers: Bel Canto eVo6, Sonic Frontiers Power-3, Classé CAM-350 monoblocks.
Loudspeakers: Revel Ultima Studio.
Cables: Interconnects: AudioQuest Anaconda & Python, both balanced; Cardas Cross, unbalanced. Speaker: AudioQuest Gibraltar. AC: PS Audio Lab, JPS Aluminata.—Kalman Rubinson
NEXT: Measurements »
ROOM TREATMENT REVIEWS
Rives Audio PARC 3-Band Parametric Equalizer Measurements
Sidebar 3: Measurements
Unusually, the Rives PARC has a hardwired bypass: when the unit is turned off, it passes the input signal to the output jacks. Turned on, the PARC had unity gain at 1kHz both when its Bypass LED was lit, and when the equalization was engaged but set to do nothing. It will not, therefore, mess up its owner's system-gain architecture. The PARC didn't invert signal polarity, and its input impedance was high 104k ohms unbalanced but a much lower 10.2k ohms balanced (both figures measured at 1kHz). The output impedance was a usefully low 25 ohms from the single-ended RCA jacks, double that from the balanced XLRs.
The Frequency, Q, and Attenuation controls were accurately calibrated, the measured parameters matching the displayed information. Fig.1, for example, shows the individual responses of the three filters for each channel that had been decided on for Kalman Rubinson's auditioning. (Note that these parametric filters provide notches at the selected frequencies, not peaks.) The lower two traces in fig.2 show the combined effect of these notch filters, compared with the response in powered Bypass. For the record, the latter offers very slightly more ultrasonic extension above 100kHz, but that won't be an issue for humans. Crosstalk in both directions for both unbalanced and balanced (not shown) operation was buried below the noise floor, which itself was very low. (I couldn't replicate the noise problems with the balanced output that Kal experienced.)
Fig.1 Rives PARC, frequency response of each of the three parametric filters as set for KR's auditioning (2dB/vertical div., right channel dashed).
Fig.2 Rives PARC, frequency response in bypass mode (top at 100Hz and 100kHz) and as set for KR's auditioning (2dB/vertical div., right channel dashed).
All the distortion measurements were taken with the three parametric filters in-circuit but with the attenuation of each set to 0dB. I could not drive the PARC into overload in balanced mode, even at my Audio Precision System One's maximum output of 15V. In unbalanced mode, the unit hard-clipped at 5V RMS input/output (fig.3)—well above the level required to drive any amplifier used into overload. The downward slope of the trace in fig.3 below the onset of distortion indicates that what distortion components do exist in the PARC's output lie below the noise floor at all levels. The distortion percentages plotted in fig.4, taken at 1V output into 100k ohms and 600 ohms in both balanced and unbalanced modes, are therefore dominated by noise. Interestingly, the unbalanced output has half the THD+noise compared with the balanced, but the right channel is even better in this respect. (This may have had something to do with the system grounding I used.)
Fig.3 Rives PARC, unbalanced, distortion (%) vs output voltage at 1kHz into 100k ohms, EQ set to 0dB attenuation.
Fig.4 Rives PARC, THD+N (%) vs frequency (from bottom to top): 1V into 100k and 600 ohms, balanced; 1V into 100k and 600 ohms, unbalanced, EQ set to 0dB attenuation.
To further examine the PARC's linearity, fig.5 shows an FFT-based spectrum of the unit's unbalanced output driving a 1kHz tone at 1V into 8k ohms, with 32 spectra averaged to drop the noise floor. The only distortion harmonics visible are the second, third, and fourth, but as none of these rises above -110dB, they are essentially nonexistent. The small spikes at the far left of this graph are due to spuriae at the full-wave-rectified power-supply frequency of 120Hz and its harmonics. I could not eliminate these, no matter how I arranged the grounding between the PARC and my PC-based analyzer. This noise was a little higher in balanced mode, but was still negligible by any meaningful measure.
Fig.5 Rives PARC, spectrum of 1kHz sinewave, DC-10kHz, at 1V into 8k ohms, EQ set to 0dB attenuation (linear frequency scale).
Finally, fig.6 shows a similar spectrum taken with the PARC driving an equal mix of 19kHz and 20kHz tones at 1V into 8k ohms. (Each of the individual components lies at -6dB with respect to the level of the summed signal.) The difference tone at 1kHz is the highest in level, but at -80dB (0.01%) is low enough to be of no concern.
Fig.6 Rives PARC, HF intermodulation spectrum, DC-24kHz, 19+20kHz at 1V into 8k ohms, EQ set to 0dB attenuation (linear frequency scale).
Befitting its pro-audio lineage, Rives' PARC appears to be bombproof. Its settings are accurately calibrated, and its excellent technical performance conforms to the First Law of Outboard Processors: "First, do no harm to the signal."—John Atkinson
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Please feel free to view our other used items for sale on Audiogon or come to our website to view our new products and see the exciting new lines we have to offer you like Bowers & Wilkins, Bryston, Aqua Acoustics, Rel Acoustics, Synergistic Research, Roon Labs, Pro-ject, Van Den Hul, Marantz and many others.
We are proud to be the dealers representing the new B&W 801 D4 Diamonds.
It is best to call David and visit: www.weinhartdesign.com with questions or come to our Los Angeles Showroom 310-472-8880 or on my cell after hours and weekends 310-927-2260 any time from 10AM - 7PM PST.
Weinhart Design has lots of other items new and used and if you’re in Los Angeles or visiting please accept my invitation to experience our World Class Audio Showroom and please visit our web site @ www.weinhartdesign.co
We accept payments by Bank Wire Transfers without fees and is the only form of payment on all sales out of the U.S. and Canada.
We prefer this method of payment and also makes shipping to addresses other than billing agreeable. VISA, MC and Papal are gladly accepted within the U.S. and Canada as long as the charge is approved and shipping to the billing address is to the one on record and plus 3% to cover card service costs.
Please call me directly in my world class showroom in Los Angeles weekdays @ 310-472-8880 or any reasonable time on my cell including weekends @ 310-927-2260 and I can answer your questions and help you with all of your new and pre owned needs.
* * * We are always interested in purchasing quality Audio and Video items, LP collections and quality trades are welcomed. * * *
Please feel free to view our other used items for sale on Audiogon or come to our website to view our new products and see the exciting new lines we have to offer you like Bowers & Wilkins, Bryston, Aqua Acoustics, Rel Acoustics, Synergistic Research, Roon Labs, Pro-ject, Van Den Hul, Marantz and many others.
We are proud to be the dealers representing the new Diamond B&W Reference Speakers.
It is best to call David and visit: www.weinhartdesign.com with questions or come to our Los Angeles Showroom 310-472-8880 or on my cell after hours and weekends 310-927-2260 any time from 10AM - 7PM PST.
Weinhart Design has lots of other items new and used and if you’re in Los Angeles or visiting please accept my invitation to experience our World Class Audio Showroom and please visit our web site @ www.weinhartdesign.co
We accept payments by Bank Wire Transfers without fees and is the only form of payment on all sales out of the U.S. and Canada.
We prefer this method of payment and also makes shipping to addresses other than billing agreeable. VISA, MC and Papal are gladly accepted within the U.S. and Canada as long as the charge is approved and shipping to the billing address is to the one on record and plus 3% to cover card service costs.
Please call me directly in my world class showroom in Los Angeles weekdays @ 310-472-8880 or any reasonable time on my cell including weekends @ 310-927-2260 and I can answer your questions and help you with all of your new and pre owned needs.
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President & CEO [email protected]
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