Setting Up Speakers and Subwoofers Using Anthem's STR Preamplifier with ARC Genesis

In a July 2019 feature for SoundStage! Access, “Integrating a Single Subwoofer into a Two-Channel System for Beginners,” I discussed the basics of that subject, and in August expanded on it in “Integrating a Single Subwoofer into a Two-Channel System . . . for Those Unafraid to Take Measurements, Fiddle with Filters, and Apply EQ.” In that second piece I mentioned Anthem’s STR Integrated Amplifier and Preamplifier, both of which include Anthem Room Correction Genesis, and are turn-key solutions for bass management and room correction.

Bass management is used to blend the outputs of one or more subwoofers with those of a loudspeaker array. Softwares such as Anthem Room Correction (ARC) are used to correct for the frequency- and/or impulse-response anomalies inevitably produced by loudspeakers producing soundwaves in a room, and which are the dominant factors affecting an audio system’s sound quality.

In September, in “Anthem’s Peter and Mark Schuck on Subwoofer Integration and Room Correction,” I interviewed the chief architects of ARC. As stated in that interview, ARC’s origins date back to about 1990, when Peter Schuck began working on a room-correction system. The latest version, ARC Genesis, was released in May 2019.

Following the interview, I got my hands on Anthem’s STR Preamplifier, which includes ARC Genesis ($3999 USD). A full review of the STR is in the works; here, I share my experiences of using the STR and ARC Genesis to get my Bowers & Wilkins 705 S2 speakers and two SVS SB-4000 subwoofers to play well together.

Setup and measurements

The Anthem STR Preamplifier came with everything needed to perform a full room calibration: an informative manual, a microphone with stand, and USB interconnects, including an extra-long one for the mike.

I connected the STR’s balanced main outputs to my McIntosh Laboratory MC302 power amp, and its balanced subwoofer outs to my left and right SVS SB-4000 subwoofers (each is placed next to the inner side panel of the speaker it’s integrated with). I connected my Bluesound Node’s digital output to the STR’s Optical 1 input, a USB link from my Windows 10 laptop to the STR’s USB update port, and the ARC mike to the laptop via USB. Following the instructions in the manual, I downloaded the most recent version of ARC Genesis from Anthem’s website, installed a firmware update for the STR, and was ready to go.

When launched for the first time, ARC presents the user with a choice of modes: Auto or Professional. Auto mode involves nothing more than taking measurements with the mike, then letting ARC Genesis do its thing. But I always want as much control as possible, so for me the choice was a no-brainer: Professional.

I used ARC Genesis in two ways: 1) with my B&W speakers alone, run full-range; and 2) with the B&Ws and my subs. When adding the subs in ARC, I chose “Two Subs (Stereo),” not “Two Subs (Mono)” -- I knew from past experience that in my room I’d be experimenting with crossover frequencies above 80Hz, where bass localization is possible.

In both cases, with and without subs, I saved a profile in which I altered none of ARC’s default parameters -- essentially, it was the equivalent of using Auto mode. I also saved a custom profile, for which I tweaked several parameters to suit my tastes and, to some degree, compensate for the limitations of my room.

Overall, I found ARC Genesis very intuitive to use. It guides the user through the measurement process with ease, fully supported by the STR’s thorough, well-written manual.

ARC is set up to process readings taken at a maximum of ten mike positions and requires at least five. I’m used to taking measurements at the nine positions required for Dirac Live 2.0, so I stuck with that, taking all measurements twice: with and without subs.

The first measurement position is at the listening position, at the center of where the listener’s head is when he or she sits down to listen: right between the ears. The software then guides you through the measurements, using a graphical representation of a couch. There’s no “single chair” option -- i.e., a single listener in a single sweet spot -- and the manual indicates that each mike position should be at least 2’ feet from the wall and 2’ from the nearest other mike position. For a scenario such as mine -- a single listening seat near the back wall -- the manual says that keeping 2’ between measurement positions is more important than placing the mike 2’ from the wall. The measuring completed, ARC Genesis generated the target curves reproduced below.

One last set of measurements can be taken for systems in which subwoofers and bass management are implemented, for perfect integration: phase alignment of the subs and main speakers. I did this as well.

Taking all of these measurements took about 30 minutes. I was ready to listen.

Listening with and without ARC Genesis -- speakers only

My initial impression was that my B&W 705 S2 speakers sounded slightly worse with ARC Genesis turned on, as is also indicated in the plots the software produced. The graph below shows the in-room frequency response of the left-channel B&W (red trace), ARC’s default target curve (black), and the projected corrected response (green):

The first thing I noticed when listening to the B&Ws full range was the reduced bass with ARC, which you can see in the graph -- the target and corrected traces are lower in level than the actual measured response of the uncorrected speaker. I was aware of a significant bass peak at 50Hz in my room, so I wasn’t surprised that there was less bass with ARC engaged. The default bass Room Gain setting that ARC came up with was 1.375dB relative to 1kHz. For someone who’s used to 6dB of bass boost, there just wasn’t enough weight for me in the low end (more on this in the next section). However, with ARC engaged, the bass was indeed more accurate, less “one-note” or boomy, as I heard when I played “Find My Home,” from Colin James’s Rooftops and Satellites (16-bit/44.1kHz FLAC, Maple Music). This track’s hot bass sounded uncontrolled and bloated without ARC engaged. With ARC, the bass thumps sounded more even, controlled, and pleasant to listen to. But I wanted a little more bass quantity and the bass quality I heard with ARC turned on.

With ARC engaged, I also heard a reduction in presence and liveliness in the midrange, which is also visible in the chart between 500Hz and 1kHz. The B&W 705 S2’s inherently forward midrange rises by 3-4dB between 500Hz and 1kHz. (See our measurements of this speaker taken in the anechoic chamber of Canada’s National Research Council.) I enjoy this attribute in a speaker, and tend to seek out manufacturers that embrace this basically nonflat frequency response -- a “feature,” let’s call it.

ARC’s default target curve runs flat through the midrange and treble up to 5kHz (above which EQ correction is turned off by default). Applying ARC’s target curve had the effect of tempering the B&W’s forward-sounding midrange -- which I did not like. Also evident in this graph is a 4-5dB bump in the B&W’s treble response between 5 and 10kHz -- another attribute of the 705 S2, and one I definitely don’t like. By default, ARC managed to partially rein in the B&Ws’ hot tweeters. When I listened to “Turn Me On,” from Norah Jones’s Come Away With Me (16/44.1 FLAC, Blue Note), Jones’s sibilants with ARC were somewhat mitigated, which I preferred. Unfortunately, her voice also now had less intimacy and presence.

Whether ARC improves soundstaging and imaging will heavily depend, much as will its effects on the bass, on the characteristics of the room. I used my favorite test track for evaluating aural image size, placement, and definition: “Give Me One Reason,” from Tracy Chapman’s New Beginnings (16/44.1 FLAC, Elektra). I focused on the size and position of the plucked guitar to left of center at the beginning, then Chapman’s voice at dead center, and the subtle cymbal work just to the right of and behind the first guitar. I also focused on the two occasional backing singers, to either side of and behind Chapman’s voice. ARC on or ARC off, I heard essentially no differences in the positions and sizes of these images and sounds.

Many users of room-correction software report hearing important improvements in soundstaging and imaging, which I can believe. If, for example, your stereo is shoehorned into a communal living room, with one speaker near a wall and the other next to open space, I suspect that ARC Genesis might work wonders. In my room, where I have an ideally symmetrical setup, and broadband absorption at the first-reflection points on the sidewalls as well as on the wall behind the speakers, ARC did nothing to alter the already very good imaging and soundstaging I enjoy. So this result didn’t surprise me.

Listening with ARC Genesis, default vs. custom settings -- speakers only

It was time to find out if I could improve on ARC’s default settings. Here are the parameters I changed from ARC’s defaults:

Room Gain (i.e., bass boost): Default 1.375dB, changed to 3dB.

Room Gain Center Frequency (i.e., the center of the range of frequencies affected by bass boost): Default 200Hz, changed to 150Hz.

Tilt Level (i.e., deviation of the target curve from low to high frequencies): Default 0dB, changed to -1dB.

Tilt Start Frequency (i.e., the frequency at which the tilt is first applied): Default 100Hz, changed to 2000Hz.

Maximum Correction Frequency (i.e., the upper limit to which EQ is applied): Default 5kHz, changed to 20kHz.

Below is the graph depicting the same in-room frequency response, now with my target curve:

Did this improve on ARC’s default settings? Yes, unequivocally. The anemic bass I’d heard with the default settings was mitigated by the more than 1.5dB of bass boost I’d applied to the target curve. I also managed to reduce how thick the bass sounded by reducing the Room Gain Center Frequency setting. With the default setting of 200Hz there was a bit too much energy from 200 to 300Hz, which can make male voices sound chesty -- as Michael Bublé sounded in “Home,” from his It’s Time (16/44.1 FLAC, Reprise). With the center frequency reduced to 150Hz, his voice sounded freer of the speaker cabinets, with clearer separation from the underlying bass notes.

The most important improvement, however, came with the increase in the Maximum Correction Frequency setting to 20kHz from 5kHz, coupled with the addition of -1dB tilt from 2 to 20kHz. With my custom settings, the remaining sibilance I’d heard in Norah Jones’s “Turn Me On” with ARC’s default target curve completely vanished.

The last problem to address with the default ARC target curve was the reduced midrange presence. Unfortunately, ARC doesn’t permit adjustments in the midrange portion of the target curve. If you’re entirely happy with the inherent midrange and treble responses of your speakers, the fix here is to experiment with turning off ARC above, say, 300Hz, and apply EQ only to the bass. Unfortunately, while I prefer to leave the midrange alone, the bass and treble of my B&W 705 S2s needed fixing -- and ARC Genesis doesn’t offer a way to fix them while leaving the midrange untouched.

Listening with ARC Genesis, default vs. custom settings -- speakers and subwoofers

When I first listened to my B&W-SVS combo with ARC Genesis’s default settings, it was certainly an improvement over the B&Ws run full-range in terms of bass extension, but I wanted still more bass slam and overall level.

The graph below shows the measured response and ARC’s default target curve for the left B&W speaker only, without subwoofer. What’s most important in this graph is something I emphasized in my previous articles on integrating subs into a system: the B&W’s significant measured bass null at 120Hz at its current position. The speakers’ positions are optimized for imaging, and I’m unwilling to change them. The obvious question: Why would I ask a pair of minimonitors to reproduce bass from 80 to 120Hz when I already have two good, sealed subwoofers positioned in the room to avoid this very null? Well, there’s no good reason I shouldn’t, so I use the subs to fill this null in!

When calibrating the speakers and subwoofers, the same ARC default settings that were applied with my speakers on their own re-emerged. So I made the same custom adjustments I’d made when running the B&Ws full-range, plus a few others affecting sub integration and bass response, to create custom settings to solve all the problems I had control over. The two user-adjustable ARC settings that influence bass performance that I’ve already discussed are Room Gain and Room Gain Center Frequency. I also had access to two parameters that I felt comfortable adjusting, now that my system included two subs capable of reproducing bass all the way down to 15Hz: Deep Bass Boost and Subwoofer Crossover Frequency (default 80Hz). A third parameter, Deep Bass Boost Center Frequency, I didn’t change from its default setting of 50Hz.

My custom settings that affected the B&W-SVS combo’s bass output differed from the defaults as follows:

Room Gain: Default 1.625dB, changed to 3dB.

Room Gain Center Frequency: Default 200Hz, changed to 150Hz.

Deep Bass Boost: Default 0dB, changed to 2dB.

Subwoofer Crossover Frequency: Default 80Hz, changed to 125Hz.

The graphs below show the measured responses and target curves using my custom settings for the left-channel B&W speaker and SVS subwoofer. Note that, for the sub, the target response is above the measured response. This will be a problem only if the sub is operated with very little headroom, but this is not the case with my SB-4000s, whose default volumes are set to -22dB (maximum volume 0dB). In short, these subs still have a ton of headroom.

I played a couple of tracks to compare the bass performance of the default and custom settings. With “You Shook Me All Night Long,” from AC/DC’s Back in Black (16/44.1 FLAC, Atco), there was no question: not only was there more bass volume with the custom settings, but the quality of the slam -- that punchy feeling in my chest -- was vastly improved with the custom settings. I also compared the default ARC setting with the B&W-SVS combo vs. the B&Ws run full range with no EQ, and found that while I could feel more extension with the subs, bass punch was mildly reduced with ARC on and the subs in use. It was quite the opposite with the custom ARC settings and the B&W-SVS combo -- when the subs were allowed to operate up to 125Hz, the bass slam I felt in my chest was visceral. No contest.

I also listened to the Eagles’ “Hotel California,” from their live album Hell Freezes Over (16/44.1 FLAC, Geffen). Comparing the custom vs. default ARC settings with the B&W-SVS combo revealed the same differences in bass impact and slam. This track also let me feel the difference in the lowest octaves. The extra 2dB of Deep Bass Boost in the custom settings provided a fuller, more satisfying experience of bass.

Conclusion

Anthem’s ARC Genesis, used in conjunction with Anthem’s STR Preamplifier or STR Integrated Amplifier, is a powerful way to apply room correction to a two-channel system. Almost every room needs at least some correction below the Schroeder frequency (200-300Hz), and many more rooms (and speakers) can benefit from room EQ all the way up to 20kHz. Enthusiasts who claim to care about the high quality of reproduced sound in their homes owe it to themselves to at least consider room EQ. With it, smoother, more accurate bass is attainable -- as the home-theater crowd has known for years.

Running ARC Genesis in Professional mode provides enough flexibility and user-adjustability to tailor the sound to suit most situations. Unfortunately, one of the situations for which ARC Genesis falls a bit short happens to be my own. If you like speakers that have a lot of midrange presence or liveliness, such as my B&W 705 S2s, but also suffer from a treble response that could use some taming, then ARC Genesis may not be for you -- other room-EQ systems that allow full user control over the target curve might be more useful. When I contacted Blake Alty, Anthem’s product manager, to discuss this issue, he acknowledged my concerns and emphasized that Anthem always listens to customer concerns and tries to meet their needs. I hope they do.

Nonetheless, so far, Anthem’s STR Preamplifier with ARC Genesis is a remarkable device. I’m not sure there’s anything else out there in Two Channel Land quite like it. Besides ARC Genesis itself, it offers balanced main and stereo subwoofer pre-outs, full bass management, advanced room correction, an advanced DAC, and a litany of input options, including a phono stage for moving-coil and moving-magnet cartridges. I’m sure that die-hard analogophiles will cringe when they read this, but I look forward to connecting my Pro-Ject turntable to the STR and having the latter digitize and apply room correction to the former’s analog signal. That should make for some interesting listening -- and reading. It will all be part of my full review of the Anthem STR Preamplifier, to be published early next year.

. . . Diego Estan

diego@soundstage.com