Hi Fred,
Broad midrange sags are VERY audible with music. To be certain of my recollections, I went to the Soundstage NRC curves. First, it was the Energy Veritas 2.4i (not the 2.3i) which I heard at length and evaluated so I don't want to castigate the 2.3i. You can see the 2.4i's measurements here:
http://www.soundstagenetwork.com/measurements/energy_veritas_v24i/ Note, the "Listening Window" curve is the best predictor, in my experience, as to what the speaker will sound like in most typically furnished rooms, because it's a combination of the on-axis and off-axis frequency response measurements. As such it best represents the combination of direct and reflected sounds that reach your ears directly from the speakers and reflected from walls, ceiling and floors in typical rooms.
The Energy 2.3i is the sister speaker of the 2.4i with two 6.5-inch woofers rather than the 2.4i's three woofers. I bet the overall curve of the 2.3i would be very similar to the 2.4i, with perhaps a little less deep bass output and extension (the enclosure is 5 inches shorter and less deep than the 2.4i).
On the 2.4i's curve, you'll note that at 1 kHz, the frequency response is -3 dB relative to the bass output between 100 and 300 Hz. Even if you reference the speaker to its output at 1 kHz, the midrange output goes down another 3 dB by 3 kHz, then by 5 kHz climbs back to the roughly the same level as at 1 kHz. Referenced that way, you could say that the 2.4 has a broad hump in bass output with a gradual depression in the midrange.
But our hearing is really peaked through the midrange, so our initial impressions of any speaker's sound will be formed largely by the shape of the speaker's frequency response between about 100 Hz and 4 kHz. The expression "it's all in the midrange" really does hold true. In the history of the NRC's double blind testing over 25 years, the speakers whose midrange response remained within +/- 1 to 1.5 dB through that region were always rated the highest on the listening tests in terms of being uncolored and musically accurate. Not surprising, given that the important fundamental tones and harmonics for most musical instruments fall into this frequency range.
The Energy's response overall is still very smooth, and in blind comparisons with other very good speakers, the differences would be audible but minor--"slightly muted compared to speaker B" "a little bit dull in the mids. ." (speaker B being the M80 v2). These are typical remarks of mine, but overall I would have rated it very well, on almost the same level as the M80 v2, with perhaps a slight edge to the M80 because of its more detailed midrange.
Regards,
Alan