DSP Devices for Room/Speaker Correction

The current issue of TAS has a review of the TACT RCS 2.0 DSP, a device devoted to correcting problems in the interface characterisitcs between room and speaker. There are several other models of DCS devices, such as the SigTech, Accuphase, and Perpetual. I long ago concluded that there was little more I could do to correct some of the anomalies in my listening environment, but the TAS article really caught my attention. I'd like to hear from others who have had some experience with DSP room/speaker corrections systems.

Showing 1 response by 1439bhr

I purchased an RCS 2.0 about a month ago. It is a very interesting piece and overall, a worthwhile addition to my system. The reality is that I'm still learning how to best use its capabilities. In short, it does what it's intended to do: reduce, if not eliminate, the vagaries of room acoustics as a factor in sound reproduction. Its effect is obvious even to casual listeners; non-audiophile friends immediately characterized it as "lifting a veil" from the music, which is exactly what it does. It has benefit in all parts of the spectrum, smooothing out the highs, giving greater presence and immediacy to the midrange, and controlling room boom in the bass for tighter sound. Overall it's a much more articulate and engaging musical experience. There is no doubt that it raises the quality of the sound to a higher level. In fact, the sound is so very clean that it takes a little getting used to -- we've become quite accustomed to room artifacts like room boom and mid/high range peaks and suck outs. A lot of what we think of as bass is actually room resonance. Getting to like the effect of the Tact is like learning to enjoy fine wine... it takes a bit of effort, but once you've gotten the taste for good stuff, you can't go back. I was worried that the "sweet spot" would be rather small, confined to a small volume centered where the calibration mike had been placed. In my room the sweet spot is large enough to accomodate any of three seats on a couch (although the very best effect is admittedly right dead center at the mike position). The unit is not without some downsides. It does take some practice and understanding of signal theory (e.g., impulse response, frequency response curves, and the effect of filters on frequency response) to program the unit effectively. This is not a "plug it in, let 'er rip" sort of process. It's more like learning to play a musical instrument: getting a good set of room measurements, selecting and tweaking the desired target frequency response curve take a bit of skill and care. The software doesn't prevent the user from doing dumb things; indeed the measured data hints at ridiculous possibilites such as extending the bass response down to 10 Hz or upwards to 20 kHz (absent any real capability), thereby forcing unnatural acts upon the system power amp and speakers. The user interface (a program running on a PC attached via R2-232 while the calibration is being done) is not the most obvious, user-friendly thing in the world. I would also have liked Tact to incorporate 24/96 upsampling (the current design puts out the same digital format that it's presented with at the input). Scaling of the correction filters to prevent potential output overload can lead to loss of resolution of a couple of bits. This loss of resolution can be of concern and is particularly noticeable on some disks (like orchestral music) that are recorded at relatively low level. The other thing I've noticed is that the sound is best at moderately loud listening levels; at low listening levels it sounds overly tight and constrained. Even Tact recognizes this effect and allows you to program lesser levels of correction for low listening volumes (the RCS 2.0 can store up to 9 different room correction filters for various situations). This apparently lets the room "ring out" more at low listening levels an impart a livelier feel. Would I recommend this unit to someone? Yes, provided they are willing to invest the energy to understand the problem it attempts to solve and how to use the unit effectively, just as one invests energy into issues such as speaker placement and room acoustic treatment.