Anthem STR Preamplifier and STR Power Amplifier

Accuracy, Authority, Adaptability

Equipment report
Solid-state power amplifiers,
Solid-state preamplifiers
Anthem STR Preamplifier and STR Power Amplifier

The new Genesis software, compatible with both Windows and Apple platforms, has a redesigned user interface that allows for non-engineering types (like me) to undertake very sophisticated EQ adjustments to address room acoustic issues. For the STR preamplifier, Anthem says that ARC now has “50% more processing power” than any earlier version of the software and that it has developed improved optimization algorithms utilizing fifteen IIR (Infinite Impulse Response) filters per channel, the processing operating at a 192kHz sampling frequency.

To implement ARC, Anthem offers three options of increasing sophistication. Easiest is to use the built-in microphone of an iOS phone equipped with ARCs mobile app; of intermediate complexity is to connect the universal microphone Anthem supplies to an iOS or Android phone or tablet running the mobile App. Note that Anthem doesn’t allow using the built-in microphone of Android phones because they’ve found that Android phones lack sufficient brand-to-brand consistency of their internal microphones’ performance.

The capability of these first two alternatives is somewhat limited—the frequency range to which equalization can be applied is restricted and you don’t get graphs to examine. Best, and surely of greatest interest to audiophiles, is the “professional” option, which requires one to install the Genesis software on a Windows PC or Mac and attach the calibrated ARC microphone (also supplied) to the computer. Provided with the STR preamplifier is a boom-style mic stand and a long USB cable to connect the microphone to the calibrating computer, which is also connected to the preamp via USB or LAN. The user specifies the loudspeaker configuration—main speakers plus zero, one, or two subwoofers—and then takes measurements of the full frequency sweeps that are sent to each speaker sequentially by the preamp from typically five, but up to ten, positions.

The instructions for installing ARC and maximizing its functionality was written by Devin Zell, Anthem’s Marketing Manager and a key participant in the beta-testing of the new software. “ARC Genesis is very user-friendly and takes the frustration out of custom-tailoring correction settings,” Zell told me, and he really seems to care that consumers see it that way. His guide provides precise directions on where to place the microphone for the five sets of calibration sweeps—surprisingly, the locations are fairly close to one another in a pattern surrounding the main listening position—and Zell has composed easy-to-follow explanations of other Genesis functions, such as how to deal with a subwoofer that has its own equalization software. Anthem is to be congratulated for having someone other than an engineer write the instructions.

As with earlier versions of ARC, the user decides how far up on the frequency spectrum to apply equalization, the default being 5kHz. Though it’s possible to do so, it’s usually not a good idea to run the software full-range because at higher frequencies the effectiveness of the correction depends on both the tweeters and microphone being at the same height as the listener’s ears. 

Once the measurements have been taken, one can tweak room gain, deep bass, crossover frequency, and several other parameters. Essentially, the user can examine the graphic representation of the room response and then massage the equalization curves to smooth out unwanted peaks and valleys. The optimization of ARC Genesis over the earlier versions was apparent: A complete five-position calibration, including the calculation and uploading steps, took just five minutes, a fraction of the time needed with the older Anthem.

Several other features of the Genesis software struck me as especially helpful. First was the “Quick Measure” function that allows one to identify major problems in a room’s acoustic signature prior to running the full ARC program. The STR preamp will generate a full-frequency sweep repeatedly from each loudspeaker and show the room’s acoustic response in real time. ARC can only boost a sagging frequency response by a maximum of 6dB without a risk of overloading the amplifier or speakers; dips in the response curve that are greater than 6dB must be dealt with initially by changing the physical location of the speakers. There’s no limit to the amount that a peak can be “tamed” by ARC.

Second, from a single set of measurements, a user can specify up to four different profiles selectable from the STR’s menu—say, corrections for a loudspeaker configuration of right, left, and subwoofer, both with and without the sub. There are circumstances where it may be advisable to actually perform more than one set of measurements, and the Genesis software allows for four. For example, in a room with a drop-down video screen, the EQ curves could look very different with the screen up or down. Finally, ARC Genesis will automatically establish a parameter I’ve always found difficult to decide on by ear—subwoofer phase. After running Genesis for a system with a subwoofer, ARC makes the call and will inform you of the optimum value in the Bass Management menu.

One bummer. Though the Genesis software is backwards compatible with Anthem, Paradigm, and MartinLogan products employing ARC-2, it won’t work with the original software on devices (such as my D2v) that connect to the host computer with an RS232 data connection. Too bad for me.

I used the STR preamp and amplifier for control, D-to-A conversion, and amplification in my system for two months. Mostly, I listened to the Anthem components as an integral pair, though I did try substituting a T+A elektroakustic DAC 8 DSD (which has multiple inputs and a volume control) for the preamp and a pair of Pass XA60.8s for the STR power amp. Digital source components were a Baetis Reference media computer with JRiver’s player for files (I installed the ARC software on that machine) and an Oppo BDP-103 universal player to read silver discs. LPs were played on a VPI Scoutmaster outfitted with a JMW Memorial tonearm and Sumiko Blue Point Evo III cartridge. On the distal end of the electronics were my usual Magico S3 Mk2 loudspeakers with Magico’s powered S-Sub employed only episodically so as not to obscure the Anthem amp’s capacities for low-end control, heft, and extension. Analog cables were mostly Transparent Gen V, and a wide variety of digital wires saw service.