Measuring the TacT RCS 2.0 Performance - Part Two (Time Domain)

It's been a while since my last post. I chalk it up to an eclectic combination of factors. First and funnest, I received the BC3000mk2 preamp about 6 weeks ago, and have been immersed in listening to my system as if for the first time. More details of the BC3000's capabilities to follow in another post (no, really - I'll get to it!). Second, the work I do that pays the bills has been kicking me in the gnads and my weekends have recently been relegated to Rest & Recovery. While the siren call of adding more blog entries has never ceased - I hear her voice calling insistently - what really pushed me over the edge to continue writing is that a good audio friend recently commented over email "Your blog is getting stale". Wow! He is right!! So, as the dying light of a clear but chilly early summer Sunday evening in San Francisco illuminates my keyboard, I sit in the sweet spot with randomly selected songs streaming in thru Jody's MacBook and will attempt to illuminate you, my reader, with a second installment of TacT measurements. All of these measurements are with the BC21.1 in the system. Since then, of course, I have replaced the BC21.1 with the BC3000, and also subtly altered the TacT target response curve.... that, someday, could constitute another set of comparisons, another blog post. Will it never end!?! Apparently not.

The first TacT measurement installment concerned the improvements in frequency response that the TacT rendered. But that doesn't tell the whole story. According to the TacT website, their approach is to correct in the time domain, which naturally correlates to frequency domain improvement (I'll let you read more details there if you are so inclined). So let's see how the TacT performs. First set of three graphs are the Impulse Response Envelope (ETC) Traces with a 10mS smoothing applied. The goal of the first two plots is to show what the impulse responses looked like before (Bypass) and after TacT correction. Finally, the third graph demonstrates the left channel before and after correction. I am not showing you the right channel because the before and after responses are fairly similar as expected, but the left speaker, which is shoved (for lack of a better word) into the corner of my room, reveals by far the more dramatic changes.

Figure 1. Uncorrected (Bypass) left and right channel responses.

In Fig. 1, notice that there is a good amount of pre-ringing particularly in the left channel. After the impulse is applied, the channel responses do not decay together as the left channel reveals a longer delay.

Figure 2. Corrected (after TacT) left and right channel responses.

In Fig. 2, pre-ringing is GONE! The main impulse response is uniform and decays very consistently between channels. There is a some "roughness" evident in the right channel decay, which could be due to the fact that the 2nd order reflection point of the right speaker for the wall to my left was untreated when these measurements were taken. Today, an EchoBusters panel absorbs the reflections at that point, so future measurements may reveal a smoother decay for the right channel.

Figure 3. Uncorrected (Bypass) vs. corrected (after TacT) left channel response.

Finally, Fig. 3 is demonstrating the left channel uncorrected versus corrected responses, to highlight the dramatic improvement by the TacT unit.

The last two figures are the spectrogram frequency vs. time decay plots for the bass region from 20Hz to 200Hz. These graphs are with both channels driven simultaneously. Figure 5 with TacT correction demonstrates reduced pre-ringing, a more evenly distributed frequency response across the range, and superior damping at all frequencies. One more point of interest is that, before TacT (bypass mode), the frequency response extends strongly down to 20Hz. However, after TacT, the bass response begins to drop significantly below about 25Hz. This is by design, and reflects the TacT correction curve that was applied (see the first installment of this series). My system correspondingly has a much faster and cleaner bass response.

Figure 4. Spectrogram plot of the uncorrected (Bypass) response.

Figure 5. Spectrogram plot of the corrected (after TacT) response.