Audio Calibration

Anthem Room Correction (ARC) System - Part 1


Verification of the ARC System's Performance with the Infinity C336 Speaker in the Large Room

Finally, this review turns to measurements of full-range speakers before and after ARC room correction. In this section, I verified the ARC's performance with the Infinity C336 full-range speakers. The results for the C336 appear here, so it is possible to compare results with my review of the HK 990 on this site and the Sherwood R972 with Trinnov printed in the Boston Audio Society Journal Speaker (BASS v33 n2).

I have similar measurement sets for all the speakers discussed above in the three differently sized rooms (only a select set of speakers was placed in the different rooms).

Using my independent acoustical measurement system, I quantified the accuracy of the response after electronic equalization. I used 0.1 octave smoothing and a 21dB maximum amplitude scale so as to not hide performance imperfections.

The target configuration panel for this set of measurements is shown below.

While I would like to skip any discussion of the Target Configuration panel until later in this review, I am forced to bring it up now since the settings change the measurements below. The white space cuts out a section of the control panel containing text that supplies some information to the user setting the panel.

In this measurement set, I wanted to see the ARC system flattening the uncorrected response over the full range of frequencies. I set the Max EQ frequency to 5 kHz (the recommended value by Anthem). More on using Max EQ is found at the end of this first part of the review. When the Max EQ frequency is reduced, the reference level offset may need to be adjusted. As can be seen from the panel, it is at 0dB (no offset) for this measurement set.

The Room Gain, another advanced setting discussed below, was set to yield a flat response over the full range of correction The low-frequency response cutoff was also set to flat.

In flat mode, ARC attempts to hold the bottom end as at a constant gain. ARC does not try to make the woofer flat to 20Hz, but instead will increase the level by up to 6dB above the unity gain value. You will see the 6dB boost in the electrical inverse correction curves below. This works well for sealed boxes for which the maximum cone deflection declines with decreasing frequency before cutoff.

For ported systems, the cone displacement can increase below cutoff. Depending on the tuning of the speaker port, the 6dB boost may have a positive (slight decrease in low frequency extension without significant increase in distortion) or negative effect (cone displacement increases below cutoff, resulting in little useable extension and increased distortion in the area at which the boost is applied). The Infinity C336 is a ported system.

Unfortunately, ARC does not provide a method to measure the distortion of the speaker pre- or post-correction. This measurement is difficult to make at the listening seat. See my NHT B10d subwoofer review for more details on problems with distortion measurements of a woofer in your listening room. Advanced parameters allow the roll-off frequency to be set so no boost is introduced by ARC.