Good to see you back in here! The planatarium got lost recently. Would it be ok with you to copy your impressions and pictures of the soviet orthos into the wikiphonia russian ortho pages instead?
(So you have the Dual 720 as well? What 55mm PMB driver was inside?)
How they sound?
TDS 5M supposed to be soviet analog of Yamaha HP-1. I did not take direct comparison. I like these cans more when listening some of 80s stuff - punk, new wave, pop. They have enough drive for such music, a little hump in upper bass, timed with extra dampening. Lots of owners prefer to brighten the TDS 5M signature by changing stock cable to some new one. But I am very sensitive to exaggerated highs, and if possible, I'm avoiding to change stock cables.
TDS 7 have one of the widest soundstage of all orthos, comparable with many high-level dynamic headphones. They have the finest sound of all TDS, classical and jazz lovers very like these headphones. But I don't, TDS 7 sound weird for me, very wide soundstage and almost none of the depth, some kind of "sound in the head". Hi-End headphones, speakers, amps etc. must have deep soundstage first of all.
Pressure on the head is very strong.
TDS 15 sound simple, without long decay as TDS 7, but have bass amount that I like. They aren't quick headphones. I prefer TDS 15 for heavy metal listening of different kind: soviet, japanese and other.
TDS 16 (made in Kiev).
More or less balanced cans, good sounding headphones but just good ones. If you listened other vintage orthos, TDS 16 Echo (Kiev) have any surprise for you.
TDS 16 (made in Smela).
They differ from TDS 16 manufactured in Kiev. The same drivers but different housing and cable. Pads from the cheap fake leather gave fantastic results for sound. These cans I'll never part with. They have the quickest attack, comparable with stats, excellent upper bass slam, exceptional transparency in mids. Forget about Grados, these ones are excellent choice for any brutal music, best choice for death-metal listening, extremely good for blues, any guitar music, where the light speed attack is important. Highs are rough and dirty.
Pressure on the head is very strong. Have long burn-in period for every listening session. Very inconvinient headphones for long listening.
In whole, soviet orthos are musical, have warm sound signature, accented mids, not the finest sound. Most of soviet headphones have hard pressure on the head.
Comparing to other orthos.
Japanese orthos like Fostex and Yamaha sound colder than soviet ones. I'd say, japanese sound is neutral and more refined than soviet one. Precise and mechanical sound vs. rough and life-like one. Of course, most of japanese and german orthos are much more convinient.
If I want to listen finest orthos, with nice long decay, I still prefer german cans as Dual DK 330\720.