The mid-range clarity of the SR325is shows up in its’ natural portrayal of the tonality and timbres of individual instruments. When we think of tonal balance in an audio product, we sometimes mean that overall bass/midrange/treble evenness that allows a band or orchestra to sound right. But it is also very important for audio products to render the distinctive, “signature” voices of individual instruments well. This latter idea is a critical test of smooth and balanced midrange, because that’s where most instruments produce sound.
Take the voice of an acoustic guitar as an example. Fundamentals on acoustic guitars range from about 80hz to 3khz, and most of what we hear, including overtones is in the 200Hz-4kHz range. This is a midrange instrument (so are voice, cello, clarinet etc). I listened to track after track of acoustic guitar recordings on the 325s, and was impressed with how natural the sound was, particularly the way the body sound and overtones were clearly defined and in balance.
That’s good and all, but we also want a headphone to be able to play large-scale material, not just solo or ensemble stuff. Fortunately, handling more complex music is another strength of the SR325is. My listening notes are full of references to the excellent sense of instrumental separation the headphones give. In other words, when you’re listening to a band, you not only hear the overall mix, but can also pick out the contributions of each individual performer, just as you can when listening to a good live performance. In short, the 325s deliver both smooth response and low distortion throughout the midrange.
When it comes to overall frequency balance, I found the 325s to be somewhat chameleon-like. The Grados sometimes seemed slightly forward in the midrange, and on the light side in the bass and upper treble. No sooner did I make this note than I’d play something with powerful bass and be surprised at how solid the low frequencies of the 325 could be. After going over lots of recordings, my conclusion is that the bass, mid-range and treble are very well balanced, but that the 325s sound as if they have a slightly “n”-shaped response curve (in other words, the levels of low 40Hz frequencies fall slightly below 1kHz mid-band frequencies, as do high 10khz frequencies). This would contrast with, say, the Denon AH-D5000s, which have a definite “u” shaped response curve (where the levels of 1kHz frequencies fall below those of sound in the 40Hz or 10kHz range). At the very highest and lowest frequency extremes (20Hz and 20kHz, respectively) the 325’s frequency response continues to show a slight degree of rolloff. But let me emphasize that these broad response shapings don’t consistently come across as “light bass” or “mellow treble” in the case of the 325, since in truth they are not dramatically far off from the ideal of “flat” or dead-neutral response. Instead, these shapings tend to make you feel that the 325s sound more “clear” and “natural,” rather than “rich” or “extended.”