Nice review
@amirm The number one issue I have with (all) H/W solutions like this is the limited number of FIR filter taps to actually provide real low frequency room correction. Whether it is Audyssey, miniDSP, Trinnov, DEQX, or other H/W processors they all suffer from the same issue - not enough FIR filter taps below 100 Hz to really be called room correction.
As a maths example, the miniDSP 2x4 HD product datasheet talks about 4096 taps. But this is the total number. For 4 channels you have 1024 taps each channel available. The frequency resolution of a 1024 taps filter @ 48 kHz samplerate is 48000/1024 = 46.875 Hz. So e.g. below 100 Hz there are just 2 frequency bins at 46.875 and 93.75 Hz. This clearly means that you have no control over the lower frequency range.
As a graphic example, here is a Trinnov Altitude 16 versus Audiolense. Audiolense is a software based DSP/DRC product that is not limited by the number or FIR filter taps for low frequency control. In this case, Audiolense has generated a FIR filter with 65,536 taps, hosted in a software based convolution engine on a PC. We can clearly see the difference with the measured Trinnov correction on top and the measured Audiolense correction on the bottom using the same speakers same room, mic, etc:
View attachment 59916
Here is another example using Audiolense with a FIR filter length of 131,072 taps for the ultimate in low frequency control with 600ms of excessphase correction at 10 Hz:
View attachment 59917
Note that this measurement was taken at 9ft at the listening position using REW's default 500ms window and no smoothing. Meaning low frequency room reflections (i.e. standing waves, resonances) are getting into the measurement. But as one can see in the phase response, it follows the speakers minimum phase response, with no excessphase (i.e. no low frequency room reflections) disturbing the bass response. The result is crystal clear, even sounding bass response. To learn more, I
wrote an article on the subject or one
can hear my talk on it.
The point I am making is that not all DRC products are the same. Some have serious limitations on how much low frequency room correction can realistically be accomplished and folks should be aware of that.
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