Yeah lots of assumptions need to be reviewed when we consider ART - it is a full blown paradigm shift!!
ART will reduce decay in the room within the frequency range of your speakers - and will do a better job with more speakers .... within limits, more speakers adds processor load, and the number of filters a processor has are limited by its processing capabilities, so the D&M AVR/AVP's are limited to 98 filters - it seems to handle 7 speakers on support duty with around 60 filters in use... trying with 11 speakers for support duty maxed out the 98 filters and started degrading the results (!). I assume that were I using a HTP1 or StormAudio AVP, this would not be an issue (more DSP bandwidth, more filters!).
However with the economical alternatives - the D&M range - you probably are limited to around 9 speakers at a guess (and by speakers I include subs)
The most critical and audible frequencies are going to be 50Hz to 150Hz - the more speakers you have that are capable in that range, the better the setup will sound! Having subs that can extend down to below 20Hz, will provide extension down to 20Hz... but I would probably exercise caution in sacrificing the critical 50 to 150Hz range in exchange for the 20-30Hz zone... Like many other things in audio, there is a balancing act there!
With your mains going down to 26Hz ( is that theoretical/spec, or actual in room measured?) - and 2 subs, you probably have the 30Hz to 80Hz range nailed (and possibly a pretty decent 20Hz to 30Hz range too)- it would be interesting to see your waterfall charts...
Mains measurement:
Preliminary listening tests of the Dahlquist M-905 speakers—installed on the ST-9 stands, as recommended—revealed:
The close-miked woofer (and port) response was also considerably flatter than we have measured from most speakers, with a very small bass-resonance peak. At the system resonance of 60 Hz, the output was only about 2 dB above its average level in the upper part of the woofer’s range, and even that minor output variation was spread over almost two octaves. When the bass curve was spliced to the room-response measurement, the resulting composite frequency response was flat within about ±2 dB from 26 to 20,000 Hz. The horizontal directivity of the tweeter was only discernible in the room measurement above 10,000 Hz.
We measured the sensitivity of the M-905 as 87 dB SPL, which was lower than the rated 91 dB but still about average for speakers of its size. The difference may have been a result of different test conditions since we used a full-range pink-noise signal while Dahlquist’s rating was made at 1,000 Hz. The system’s minimum impedance was about 4.8 ohms in the 8,000- to 10,000-Hz region, and it measured 7 ohms at 150 to 200 Hz. Its maximum impedance was 28 ohms at 60 Hz, and there was a broad peak of 18 ohms in the vicinity of 1,500 Hz.
We measured the woofer’s distortion with a 4-volt drive level, corresponding to a 90-dB SPL at 1 meter. The distortion was less than 1 percent from 100 Hz down to almost 60 Hz, the effective crossover to the port. Below that crossover the distortion rose to 5 percent at 45 Hz and 9 percent at 35 Hz. In high-power tests with single-cycle tone bursts, the woofer began to sound “hard” at about 350 watts into its 8.5-ohm impedance at 100 Hz. At higher frequencies the amplifier clipped—at outputs of 490 watts at 1,000 Hz and 1,380 watts at 10,000 Hz—before distortion became visible on the acoustic waveform.
Quasi-anechoic FFT measurements showed an overall group-delay variation of about 0.1 millisecond between 4,000 and 20,000 Hz and 0.5 ms between 1,000 and 20.000 Hz, convincing evidence of the attention paid to the phase characteristics of the M-905
I'm calling them better than I can hear.
The sub's I do not have any actual measurements in the box or the room on. Only on the raw 12" Pioneer Automotive dual 4 Ohm voice coil (converted to a single 4 Ohm circuit within the box) raw speaker 20-80 HZ FR 96 DB 1 WATT 2000+ watt handling capacity. Each one is floor firing (speaker & port) and the mains sit on top of them, at the pre-subscribed 3.5 degree angle at the original stand height (so, therefore 'should' be in phase with the main) and the subs are powered by a PROTON D-1200 stereo amp but in blended mono configuration. The mains are powered by a NAD 2200.
The plan was: add 2 more subs (same sub setup) in other locations of the room. But now: I'm befuddled?
