The October/November issue of "The Absolute Sound" magazine has an extensive article on room correction, and I believe they review both of these units.
18 responses Add your response
I too am looking into this approach. I must say - on paper - the TACT seems superior to the Rives due to the time correction it offers, which should make speaker placement and other room issue less disruptive of imaging.
Rebuttals to the above are welcome, for I am in a similar boat as "acw" -- there are no local dealers for these devices.
The TacT does its correction in the digital domain, so it has to either get a digital signal from your source component or convert an analog signal into digital. If you use the TacT, the preferred approach is to take the "digital out" from your CD player and either use the DA conversion that is built into the TacT or go from the TacT to an outboard DAC before going to your preamp. Taking the analog signal from your CD player and using the AD conversion in the TacT would be a pretty compromised approach. That is not to say you won't be happy with it, but the TacT AD conversion unit is really meant for accomodating analog sources such as LP and tuner. The TacT AD unit works fine, but its quality is not an engineering priority in the product as the company is pretty much dyed-in-the-wool digital ("We don't do analog" Peter Lyngdorf once told me).
The Rives is all analog, so none of this applies. The TacT is capable of doing a lot more than the Rives, which is limted to three corrections per channel and only in the low frequencies (which is where you need it). That may or may not be a good thing for your application.
Obviously--I'ld be watching this thread and now need to comment, particularly on time delay. My graduate work is in digital signal processing and using FFT filters in the digital domain with narrow band parametrics leaves digital artifacts--there's no way around this. When you try to correct for time coherencies depending on the frequency and the correction these same "ringing" type of artifacts occur. This is one reason we designed a parametric in the analog domain.
We designed the PARC to solve bass problems for existing rooms which there was no other realistic solution for. There are always passive solutions--but implementing some of them can be very expensive, time consuming, and basically just not worth it. The PARC had to perform for very high end systems, which we felt there was no system on the market that had the signal transparency required for high end. The PARC is limited to low frequencies. It only operates below 350 Hz, and we recommend that it only be used below 200 Hz. Keep in mind middle C on the piano is 260 Hz--most people know that the frequency spectrum is logrythmic, but not so many know how quickly you reach middle C. Everything above 350 Hz is band passed, so it can remain pure. Our philosophy remains--no electrical correction is the best--unless you have a bass problem that can not be taken care of otherwise. If this is the case, then do it in the analog domain. Why? First, there's no additional or limitations in with any D/A or A/D conversion. This will yield the best transaparency, particularly when the mid/high fequencies are band passed. Second, the phase shift in a low frequency of a minimum phase system (your room) is the inverse of an analog parametric filter. What this means is that a parametric filter in the analog domain automatically corrects for the time/phase shift that was originally caused by the room mode. This is something that is inherent to the system--where nature actually works for us. The whole principle is very simple.
If you read the Absolute Sound Review, Robert Greene is the review and a professor of mathmatics at Stanford. He mentions the phase issues in a very eliquent way.
There is no question the TACT has many more features than the PARC, but of those we've found none that are useful if you deal with the room (even in very mild terms). Only the bass remains a significant problem where 4 feet of traps or custom designed Helmhotz resonators are out of the question for either cost or aesthetic reasons. In these cases, the PARC will yield the most transparent method of dealing with this one very common and problematic issue.
I used a Tact RCS 2.0, with all available input/output board options.
First, if you are looking at the factory refurbished RCS 2.0, as I did, forget it. There is a 2.0s version of the 2.0 that samples at a higher frequency than the 2.0 The 2.0s is 192khz and the cheaper 2.0 is 96khz. The 2.0 is just not transparent enough to be effective in a resolving system. It provides some benefits as a room correction device, but seemed to remove some air and high frequency resolution in my system. The resulting sound produced an improved bass response, but seemed to lack the detail and transparency that were present without the unit.
My understanding, from discourse with the Tact Audio user group, is that the higher sampling rate 2.0s resolves some of the 'detail' and 'transparency' issues.
As far as configuration goes, the Tact has a reasonable DAC, but it didn't better my MF A3 24 upsampling DAC. So I ran transport - Tact Digi-in - Tact digi-out - DAC.
Some people are also using the Tact as a preamp, I tried this but it didn't work well for me.
If I were to get back into the room correction game I would probably give the Rives unit a spin. It approaches the problem from the right perspective, that is, deal with the issues (bass response) and leave other areas alone.
I appreciate your detailed reply and found it quite topical to my concerns.
I can also appreciate the introduction of digital artifacts (you mentioned ringing) with FFT filters (I've studied/designed such devices under Dr. Paul Horowitz). Still, one must weight the impact of such distortions against the larger issue of the room's corruption of the time component of the signal; for me, it is not hard to imagine such artifacts ultimatelly falling into the noise, particularly if the system is highly adjustable (as the TACT is).
At the end of the day, however, I suppose I'm still stuck with the inevitable home audition (you see, I am quite lazy :-). I only wish audio dealers were more receptive towards carrying such products, so I could give the different approaches the acid test: listening to them.
Again, thanks for your reply.
Thanks, I am grateful for all for your informative feedback. I'm glad my question has also stirred discussion on an issue that has concerned many.
For all practical purposes, it seems like the Rives is the better way to go if I want to preserve a purer analog signal. Will try to audition that in my system.
Alternatively I'm also thinking of a used 2.2x with the better DAC, if resale prices are close to the Rives and affordable.
Apart from the Absolute Sound review, has anybody out there compared/listened to the Tact 2.2X and the Rives PARC and made any observations?
It doesn't make much sense to use the Tact unless you're going to just use the EMC as a transport and rely upon the Tact for D/A conversion. There is absolutely no reason to add extra A/D and D/A stages to your playback chain. The Tact's D/A may or may not be an improvement over the EMC, only comparison listening will give you that answer. Your original post says you're looking for an analog EQ device, that eliminates the Tact and leaves the Rives, or any other analog parametric EQ device.
BTW, I own a TACT 2.0 and think it's a marvelous piece of equipment. It has a very steep learning curve, but it is capable of serious sound alteration. If used correctly, it's wonderful, but it doesn't sound like it's the piece you're looking for.
Onhwy, I don't understand your suggestion that the TACT is inappropriate for this application and assertion that analog equalization is the optimal solution. The reason to add an "extra A/D and D/A" stage in the playback is to remove room effects which have a great negative impact than any intermediate processing steps.
Candidly, the 'digital artifact' argument (not made by you) is a bit specious, for analog equalization also introduces phase and amplitude artifacts to the playback. So it's more an issue of minimizing the negative effects of the improvement activity. And on this score, we fall into the subjective realm of what people are looking for in their system. If time coherency is paramount to the listener, then there is one product which can assist. If frequency flatness is desired, however, then there are two approaches (which have pros and cons).
What Mr. Rives writes is very interesting. I remember reading a recent article about the TacT in Hi-Fi News, I believe, in which the reviewer clearly says that any filtering beyond 4th order is very audible as distortion. Let's remember that one of the supposed advantages of digital correction is the very high-order filtering possible.
I don't disagree with Mprime's comments, but it makes more sense to me to just go digitally from the CD player to the Tact. The different (if any) between the D/A stages is probably less than the ill effect (even if small) of the added A/D/A stages.
Tact maintains a well run user group on Yahoo. Here's the link. Not everyone markets via Audiogon.