Measuring the TacT RCS 2.0 Performance - Part One (Frequency)

I am posting exciting measurement results comparing the SPL room response before and after TacT correction, compared to the target curve I asked TacT to meet. I haven't personally seen this type of comparison done online (though it may well exist somewhere), perhaps because it requires two separate steps: first, measurement and correction with TacT; second, a way to measure the post-correction response. For those not familiar with the TacT unit, this machine does not allow you to measure the system response after correction has been applied. I have already showed in a previous blog entry the original room response (i.e., pre-correction) using TacT's measurement method compared to the target curve which is my goal.

For this exercise, I used REW software along with M-Audio hardware and microphone to measure the response both before (Original Response) and after (TacT Correction) of my system. The microphone has a calibration curve applied, specific to the microphone model. I directed REW to send the test sweep signal through both speakers simultaneously. This is contrary to advice, or maybe you would say common wisdom, that the averaged R+L response is "closer" to what we, as listeners, perceive to be the tonal balance of our system. However, what I have found is that when I compare the REW results of both speakers against the R+L averaged response, that the results of both speakers being driven are closer to the target curve. This is not conclusive proof of anything, but has led me to use this REW result in the graphs below. For the reason why my Target TacT curve looks the way it does, please check out my previous blog entry on TacT Curves - but, in summary, here is my rationale: 1) below 300 Hz, I want to tailor the bass response to slowly rise as frequency decreases, and then drop off quickly below about 25 Hz. This imparts a powerful character to the bass notes and balances the overall frequency response, while also respecting the physical limitations of my modestly sized speakers; 2) above 300 Hz, I like the overall balance in my system and choose to basically preserve the original response. Note: I believe the dip in response above about 8kHz is an anomaly in this graph, since it is not seen in some of my other measurements when the original response has been measured.

Fig. 1. Original response of my system before TacT correction, shown against the target response that TacT is asked to achieve.

Figure 2 shows the result after Tact correction has been applied, shown with the target response. Overall, the target has been met, which is amazing to my eyes and to my ears! However, there are a few points worth mentioning. First, the response below about 150 Hz is almost exactly what I have specified. The goal here is to optimize (reduce) the demand on the amplifier and speaker in this region, which simultaneously frees up more power for the higher frequencies. Listening comparisons reveal that these goals have been achieved and result in a cleaner presentation of the music overall. Yeah for me, and yeah for the music.

Second, in the region between 150Hz and 300Hz, the TacT did a valiant job to help tame the suck out, but ultimately there is a still a sizable dip in frequency response. Generally this is to be expected since it isn't recommended to use an equalization tool (ultimately, that's what TacT is) to help fill in the dips too aggressively; however, the depth of the dip has been reduced. Whether this is due to TacT "filling in the hole" or whether the amplifiers are simply better able to compensate due to less demand in the lower bass region, I don't know. Either way, it's a win for my ears.

Finally, in the frequencies above 300Hz, the characteristics of my system have been well maintained. Score.

Fig. 2. Corrected response of my system using TacT, shown against the target response that TacT is asked to achieve.

Of course, the graphs so far are the system response with both speakers driven simultaneously. If we think just a little deeper, we might wonder what the individual Left and Right responses look like, both before and after TacT correction. In other words, is TacT also helping to equalize the channels individually, a particularly relevant question for my off-center setup. Glad you asked! Let's take a look...

Figure 3. Individual Left and Right speaker responses, before TacT correction (Original response)

Fig. 3 shows the Left and Right individual speaker responses, before TacT correction is applied. Below 300 Hz and even up to 700Hz, there are fairly large discrepancies in the response of the two channels. Perhaps not surprisingly, above 700Hz, the responses are fairly well correlated.

Figure 4. Individual Left and Right speaker responses, after TacT correction (Corrected response)

Fig. 4 shows the Left and Right individual speaker responses, after TacT correction is applied. In the lower frequency domain, the responses are now very well correlated, though there are still some discrepancies between 30Hz and 70Hz. But, certainly, the magnitude of the differences is much less than before TacT was applied (Fig 3), and of course the overall bass response is as expected. Above 300 Hz, the channels are definitely even better correlated than before TacT, though there is now a difference in the region around 1kHz that doesn't exist in Fig. 3.

As you can see, the TacT has made a world of difference over the entire frequency response of my system, and is certainly doing an excellent job of correction when we review the measurement data. If you don't have one already, and you have bass problems that you can't tame - who doesn't? - then I recommend that you get one of these units as soon as possible. You will not regret it! 

 Next time - what do the time domain measurements look like??? Stay tuned for more measurement updates in an upcoming installment....