Having been used both HD650 and K702 for quite some time I can only say I love both of these CANs and will use them for different types of music listening. For vocals I will use HD650 while for jazz music, acoustics and classical I use K702 instead.
Today I use REW software, my laptop and an omi directional mic to take the Frequency Response of the two CANs. I got the following plots (both are taken from the right can):
My headphone amplifier is Fidelity Audio HPA-200 and the volume setting are the same when the readings from the two CANs were taken. The volume knob was at around 11 o'clock position.
The followings were observed:
1. The output dB(A) of both CANs are almost the same (about 67-70 dB(A)) even though people say that K702 needs more power to drive. It is not the case here and I think it is because my headphone amplifier can delivery sufficient wattage and current to the power hungry K702.
2. The Frequency Response of both CANs below 1.5 kHz are quite similar.
3. Above 1.5 kHz HD650 has a more smooth FR than K702 which has larger fluctuations.
4. For K702 there is a bigger dip at 3 kHz and a boost in 7.5 KHz. I believe this arrangement makes the music from K702 a bit lean but it enables the very faint high frequencies to be more prominent to our ears.
5. When compare with the Impulse Response HD650 has better control than K702 as it has better damping ability. I believe it is due to its having a much high impedance than K702 with has only 62 ohm.
On actual listening K702 has more space and sounds further away while the music from HD650 is closer.
Based on the above plots it seems that actually HD650 is better CAN than K702. However as I said before they are both excellent CANs for different types of music and whether you like the sound from HD650 or K702 is a personal preference. For me I love both of them !!
Edited by inter voice - 3/23/12 at 4:32am