Omnisat v2 FS Measurements and Analysis (cont.)

The impedance plot shows us the typical characteristics of a passive radiator system, evidenced by the peak-valley-peak curve centered at ~ 85Hz. The curve minimum was just under 4 ohms.

Owing to the inductive character of the impedance in the neighborhood of that minimum, as evidenced by the positive-going slope of the phase curve, some amps might strain a bit when reproducing the segment of the spectrum in the neighborhood of the minimum, especially at high playback levels. Most shouldn't have any problem at all. Notable too is the absence of any peaks indicative of unwanted pipe resonances.

From Andrew Welker (System's Designer), on the absence of pipe resonances:

My idea was to allow the top woofer to act full-range at the bottom end, but in a sealed sub-enclosure. This reduced the height (length) of the cabinet volume "seen" by the front firing woofers, and moved the main standing wave slightly lower in frequency. We also found that by staggering the positions of the front mounted woofers and passives we were able to "drive" the cabinet at points that would reduce the effect of the standing wave. The side benefit is that we have two different low frequency alignments (sealed and passive radiator) adding together and by adjusting the parameters of each section we are able to achieve a seamless blend at the bottom end. All of this adds up to excellent bass performance in a cabinet with very little internal volume.

Focusing now on that 6kHz - 20kHz portion of the spectrum, the generally downward slope of the amplitude response plot is quite noticeable. With a front-firing loudspeaker this HF downward slope would indicate, subjectively speaking, a very recessed top end. However, when you take into account that the v2s (when operating in this portion of the spectrum) by design radiate energy all over the room, what appears to be a recessed top end will in fact sound like a clean, respectably smooth HF response characteristic. And it does so because its not only the on-axis response that counts but also the total amount of energy dumped into the room, on and off-axis by the system. It's that sum, perceived by the listener, that counts.

EQ this portion of the v2s direct sound amplitude response flat (as I did for the fun of it) and you'll end up listening to what'll sound like a pair of loud, annoyingly efficient tweeters. So, for a system with the radiation characteristics such as that possessed by the v2s, that downward sloping amplitude response plot is exactly what you want to see in a measurement.