Room correction - what device works best?

Michael (Swampwalker), here are my thoughts in response to your post:

Regarding the last question, about flat frequency response, see these paragraphs from the DEQX FAQ. Makes sense to me, and note that DEQX provides a goodly amount of flexibility in that regard, for both the speaker and the room calibration/correction processes. Also, keep in mind that a large number of user-created equalization settings can be set up in the DEQX, and selected among via the remote control.

Regarding the speakers, my instinct would be that the sonics of the 5 inch mains you are presently driving full-range would be likely to benefit from having deep bass frequencies kept out of them. Provided that the plate amps on the subs can accept line-level inputs, you could accomplish that by taking advantage of the DEQX subwoofer integration features.

If you were to do that, and if you were to place the DEQX ahead of the preamp in the signal path as you described, to keep the volume levels of the mains and the subs in sync you would use the DEQX's volume control to adjust volume, with the preamp's volume control set to a fixed position. DEQX volume can be adjusted via both the remote and the front panel.

Regarding item 4, a point to be aware of is that John Atkinson's measurements of the DEQX PreMate that were provided with Kal's review in Stereophile indicated that the DEQX downsamples 192 kHz data to 96 kHz, and 176.4 kHz data to 88.2 kHz. In the comments section following the review JA said the following, which makes sense to me:

Running powerful DSP at 4Fs sample rates is very consuming of resources, so this compromise is not uncommon. It is likely that the benefits of the DSP correction outweigh the potential drop in sound quality due to the downsampling.

(4Fs presumably refers to a sample rate of 4 times the redbook CD rate. 4 x 44.1 kHz = 176.4 kHz)

Best,
-- Al

It is well documented that multiple subs can achieve better results than an equivalent single sub in appropriately sized rooms. Typically smoother frequency response from spreading room nodes and higher output/lower distortion from twice the woofer radiating surface.

"It is well documented that multiple subs can achieve better results than an equivalent single sub in appropriately sized rooms. Typically smoother frequency response from spreading room nodes and higher output/lower distortion from twice the woofer radiating surface."

Onhwy61- I think the key word is CAN. You can definitely get higher output from twice the radiating area (and twice the amplifier power). With careful placement you SHOULD be able to get smoother frequency response. However, it seems to me that it is at least theoretically possible to 1. place the subs so that they reinforce the same room nodes, or 2. create additional nodes. Not likely, but possible. For example, #1 could be achieved by placing both subs in the front corners of the room. If a node were located at the listening position, it would be re-inforced. OTOH, if the subs had a phase switch, setting one to 0 and the other 10 180 might cancel that node. #2 seems least likely but also at least theoretically possible. I'm not an acoustician, so if I am wrong, someone please correct me.

to 180

Al, I agree that the advantages the DEQX bring to the table might (probably) outweigh the down sampling issue, but in that sub $100 DVD players can decode (yes I realize that's all) the native higher sampling rates, it is still somewhat disconcerting that an item that can cost close to $5,000 can't do it all in the native higher sampling rates.
I still wish there were more amps (preferably mono) that could accept direct digital input from devices like the DEQX.