I'd like to clear up some misconceptions I've seen in this thread. Each of these are topics for which volumes of research data is available and getting into the details behind the physics, psychoacoustics, and basic concepts of digital signal processing would take more time (and space) then I have at the moment so I apologize in advance for being brief. Each of these are expressed in the context of small room acoustics.

Multiple Subwoofers:
The primary purpose of multiple subwoofers in a residental room is most certainly not to increase SPL or low frequency energy in the room. Indeed if there is a lack of performance in this area, one is well advised to get better subwoofers. As shown in the research by Floyd Toole, Sean Olive, Todd Welti and Alan Devantier, the result of multiple subwoofers in a space is providing consistent bass response in the seating positions ... noting we don't give a hoot about bass response where people do not sit and listen. The key word here is "consistent". This work also dovetails into the work by Gerry Lemay in which he presents the concept of the "virtual subwoofer". This work predates the publication of Mr. Welti's 5000 subwoofer document. When two subwoofers are placed in a space, they do not behave as to independent subwoofers but rather mimic the performance of a single subwoofer placed midway between the two. Largely due to the wavelengths involved, multiple subwoofers do not exhibit the audible problems associated with a dual-mono configuration (example: two center channel speakers playing exactly the same signal). Without getting into the details of diferential EQ of multiple subs, the first step in calibrating a multiple subwoofer configuration is to make certain all subs are set to exactly the same phase and SPL. Any suggestion the purpose of multiple subwoofers is to increase SPL is misguided to the extent such use is contrary to the intent of such configurations.

Multiple Subwoofers and Automagic Room Correction Systems:
At the current time, automagic room correction schemes with exception of the more recent Audyssey products, do not deal well with multiple subwoofers. It may be more appropriate to say "inconsistent" rather than "not deal well". This is not a fault of the correction schemes but rather a design constraint. One can get lucky but traditionally if everytime you push the automatic button you get a different result that is a symptom. At present only Audyssey has developed a room correction system designed specifically to address (I believe the upward limit is four) multiple subwoofers (for example Denon has four sub outs in some of their newer products). Note, I am not making any implied statement pro or con about the Audyssey implementation. I have not had a dialog with Chris in the past year and if we had discussed this it would have likely been under NDA in any case. In order to perform a right proper job, the room correction system would need to individually adjust the parameters and PEQ each sub individually. Where only a single sub out is available, such would not be possible. (Potentially, Meridian could do this in the digital domain once they could individually address multiple digital subs in a configuration.)

Full Range Speakers:
I don't care to debate an individuals preference for full range speakers or full range speaker configurations rather in two-channel or multi-channel environments. None-the-less, the physics behind the behavior of sound in small rooms makes it very clear that it is virtually impossible to configure speakers in such a manner as to provide excellent sound staging concurrently with smooth bass response in the seating locations. It is, of course, less difficult to accomplish with only one seating location in the room. Just to avoid notches would require such a speaker to be approximately 15' from any room boundary.

Equalization Systems:
It is clearly more convenient to have all the PEQ capability resident in the surround processor. Currently, we see more, and more of this being introduced into the market place. I advocate this if only because it sends a message to the consumer that audio needs to be calibrated. On the other hand, the vast majority of these imbedded systems do not currently contain the full set of tools required (or perhaps access to those tools) to provide a truly excellent calibration. (Note: calibration is to deal with speaker/room interaction and not to compensate for speaker performance or lack thereof.) In the context of Meridian specifically there currently does not exist a product to provide that level of calibration in a full digital environment. I had a SigTech unit for a brief period of time in my Meridian system but SigTech is no longer with us. QSC does provide a DSP with digital in/out but that protocol is propriety to QSCs playback chain ... it would be great if Meridian and QSC got together to provide a Meridian branded tool. None-the-less, there is nothing inherently wrong with using a high quality DSP between the surround processor and the amplifier(s). There can be a lot of arm waving about A-D/D-A conversion steps; but it is generally just that. In any case, the proper calibration process (using QSC for example) is to utilize the interior test signals generated by the QSC such that from the QSC, through remaining playback chain, to the seating positions, the adverse impacts of speaker room interaction are resolved. At that point, the surround processor can be brought into the mix followed by each individual source.

To suggest that Meridian (or any other processor) is inappropriate to use in an environment utilizing various PEQ or equalization tools is incorrect. The fact Meridian, ADA, or any other surround processor does not have multiple subwoofer outputs disqualifies that processor from PEQ would not be correct. Indeed, in the absence of multiple subwoofer outputs suggests a greater requirement for third party intervention. Meridian's full digital playback chain does, however, limit ones ability to perform calibrations. None-the-less, I am convinced that over time Meridian, or another vendor, will provide a solution.

Happy Holidays to all...

Last edited by DErskine; 2010-12-13 08:09.
Imagine what you could do if you could do all you imagine.