It is fine to talk about the sonic properties of the various drivers and configurations, but when it comes down to it you must deal with the amount of outside sound which is combining with what you're hearing in the cans. The more isolation you can achieve, the more the sonic characteristics of the drivers come into play.
Isolation:
The more, the better. the HD-265s include a frequency response of 10 Hz to 25 kHz (no tolerance stated), an impedance of 150 ohms, a characteristic SPL of 94 dB (I assume this means with a 1milliwatt input), a THD of less than 0.15%, Where I ran into problems with these phones involves their measurements. They just did not produce a flat curve. The response was very strong over the 50-to-300 Hz range, with the average bass level about 8 dB above the range between 500 Hz and 2 kHZ. This in itself was bad enough, but above 2 kHz, the response dropped another 5 dB, and the area between 3 kHz and 10 kHz was also rather choppy looking. Above 10 kHz, the response rose to nearly the midrange levels, and extended strongly clear out to 20 kHz.
This curve was obviously problematical, and it may have been the result of the spacious cavity formed around the microphone tip by the large, over-the-ear surrounds. Possibly the template was resonating somehow, and causing the irregularities. It may have even been responsible for the large suckout in the midrange and upper midrange.
While the overall subjective sound was more reticent than with the other phones, it definitely was not as subdued sounding as the measurements suggested it should be, and it just did not sound wrong to my ears. I will also note that Sennheiser supplied a curve with the phones, and it was far flatter than what I measured, although the rise above the 10 kHz point was also visible in their curve. In addition, when listening to sounds out in the real world, I should point out that the frontal head-related-transfer-function response of a normal human being displays deep notches in the 8kHz region. This is akin to what I measured with the HD-265 phones, and perhaps the unit was designed to somewhat mimic that effect.
having said all that , i find them great for cross reference between my near field monitors , when i do mix downs for guitars and drums.
if you get lucky grab a pair. :)
