Originally Posted by Stereojeff
The labels for the 3 subwoofer curves were for convenience, only, and do not necessarily indicate which is correct. As Curt has pointed out in the other active R-972 thread, only the target curve for the subwoofer is changed. The unit should not (and must not) be re-set after updating the target curve with the subwoofer level files. Dr. David Rich, then technical editor for the Sensible Sound reported two things that are pertinent for this advanced crowd: 1. He insisted that the curve labeled +6 is actually flat--or at least was in his room. 2. He also suggested that after the data acquisition and filter construction was saved to the AVR, reversing the phase of the subwoofer(s) gave better integration between the main speakers and the sub. While I have not made any effort to compare the in-phase/out-of-phase sound, I do reverse the woofer phase as the final step in the R-972 audio calibration.
No room EQ I have tested finds the phase of the subwoofer relative to the main channels. This requires test equipment to determine if the subwoofer phase is correct. A Radio Shack meter and the Stereophile Test Disc 1 should suffice. Use the warble tone on the test disc that comes closest to the subwoofer crossover. Set the volume to achieve a reading of roughly 80dB SPL (this number should swamp room noise, but not be so loud as to require hearing protection). Note the amplitude. Now reverse the phase of the subwoofer and see if the amplitude changes. Retain the setting that achieves the higher SPL.
The test must be done with any room EQ and is not an issue with the R-972. As an aside, the R-972 will correct any phase reversal with the main channel speakers unlike many room EQs.
To achieve optimal performance from a high-end system requires software that displays the response of your room at core listening positioning, especially in the presence of a subwoofer. I use AcoustiSoft RPlusD, which reports the Radio Shack SPL meter can be used as a microphone (OK below 500Hz). There is a calibration file for the Radio Shack meter on the AcoustiSoft site. RPlusD does have a learning curve, but AcoustiSoft's on-line documentation is a great reference. Click on the link Introducing RPlusD Modal Analyzer at the top of the home page. Other, less intensive, test systems may be available. I do not have experience with them. The simpler ones may not allow multiple measurements averaging or may do it incorrectly.
My review of the R-972 is in the Summer issue of the BAS Speaker publication (volume 33). The issue is available as a paper copy or free download on the web. To purchase the issue from the Boston Audio Society, please contact them via the website.
The publication of this review was delayed. The review was originally scheduled for Sensible Sound magazine, but it discontinued publication. I thought another magazine might publish the piece last year but that was not to be. I had to start again with BAS Speaker, which has done a superb job of presenting the figures and text.