I don't have time to fool around with irrelevant stuff, I'll just get to the sound.
This is a corrected response I was able to come up with based on Dale Thorn's "Headphone Correcting" system.
Sound -
It was hard to get a good response from this headphone, drivers are very poor quality. There's a lot of Sub-Harmonic distortion, excursion hits at 350Hz at relatively low SPL. So any energy from that range to below will result in over-riding and rattling. Keeping that in mind, I came up with a response relative to my other Neutral responses, of course this is not 100% correction but this is the best I could come up with...
The actual response relative from my curve will be the opposite, of course.
Bass correction from - 30Hz to 120Hz is around +8db, 60Hz has 2db down to resolve excursion rattling. There's a very strong buzz from 60-80Hz. Then I did a roll off from 120Hz-200hz, keeping 200-250 flat.
There was some Mid-Range accentuation which was brought down with my EDT990V pads, because of this there's not a huge correction in the Mid-Range. -2db at 500Hz, -3db at 1-2Khz. 4Khz has no correction.
I kept everything flat from 4Khz to 12Khz and above, any correction there will result in accentuation of the bass which would trigger my excursion.
Response aside, fidelity is very poor. I don't even consider it Low-Fi, its below Low-Fi. With the corrected response, its sort of passable but still not that great. With the EDT990V pads, separation is better and things don't sound congested which also has to do with the correction. Forwardness from 1KHz to 5Khz results in congestion and hence it will disturb the imaging. A corrected response will open things up.
Build Quality -
Solid, Sony knows how to make good built Headphones, this one is well built and feels solid. Only Metal used is the Spring Steel Headband.
Even after so many years of service, it seems to be intact. Compared to a HD545 Vintage, this Sony is much better built.
Mods -
The day I received this Sony I knew something was wrong, first of all Pads were dead. There was a phase issue so I knew that needed fixing.
I cut the cable and to figure out what the problem was. The conductors of the stock cable were falling apart. The cheap Copper they used was breaking off.
I decided to do a full re-cable with my Belden 9451 (Tinned Copper). I removed all connections from the Potentiometers for fidelity, also made it dual entry for fidelity and I added EDT990Vs for comfort.
Amplification - These basically have Speaker drivers slapped into a Headphone, you'll see pictures on the Video below. There's no word about their Impedance or Sensitivity.
These were unusable on my Valhalla 2, my STX drove them very well except there was a very faint noise which is not my STXs fault, even with my DT48A - 5Ohm. There's no hum. It's only apparent with Speakers and since this uses Speaker drivers, I was not surprised. There was no Hum when plugged into my Violectric V200.
Due to signal issues, I couldn't use my V200, I'll need a dedicated DSP card for that. My STX with my curve drove these the best.
Overall, I can't say anything good about them, I just got them for my collection. I may use them for some Mono recordings, maybe not.
YouTube - (Review)