This is kind of off-topic. This is ES-1A - an Omega I inspired headphone designed and built by only one person who has experience in repairing Omega I's.
Tonality
ES-1A's sound signature is a mixture of slightly recessed mids and treble with emphasized air region. This shifts spectral balance towards high frequencies and overtones become quite apparent in the stage.
Bass: Bass response is flat and well balanced if you can seal ES-1A's well on your head. Sub bass textures are significantly better pronounced on ES-1A than 009 and even 007. Midbass can get punchy if the source is calling for it however there is no slight emphasis on midbass to make them slam as hard as Focal headphones. ES-1A's bass response has no problems, there is not much to talk about here. It's important to note that most of the music we listen is recorded with speakers in a room. Speakers do not have flat bass response in rooms, in room response of state-of-art speakers is usually r a downward slope from 20hz to 20khz.(Check steady state in room response for speakers for more info). As a result, since the music we usually listen is recorded with speakers, flat bass on headphones is a deviation from accuracy(usually) towards bass light sound signature. However, this is the norm with headphones usually. And ES-1A achieves flatness better than most others.
Mids:
Weird. There is a peak(a mountain?) around 1100hz which gives warmth to overall presentation. From there on, there's another dip around 1900hz. 1900hz is not only heavily recessed, 1100hz mountain peak definitely forward masks some of the detail around 1900hz and pushes the detail in that area even to lower decibels. Female vocal overtones may be lost in the stage because of this. However,
I think this 1100hz peak is necessary to balance the extremely emphasized high frequencies on ES-1A. My solution is to use 007 pads which tames down 1100hz peak by 2db and boosts 1900hz-2500hz a bit. On top of that I apply a bit EQ too. I understand why the designer didn't damp the 1100hz peak however it makes the situation worse in the areas where the response is already recessed.
Treble
2.5-5khz: As I already mentioned before, there is a slight recession from 1500hz to 2500hz. From 2500hz onwards until 5khz, there is no peaks and dips in this area for the most part and this makes ES-1A sound very *fast*. Quite good. There isn't much to say, ES-1A performs very good until 5khz.(yes I like that 4k peak too). Most other headphones have small dips and peaks around 2-5khz. ES-1A behaves extremely well where most headphones fail hard.
5-10khz: The driver goes out of min phase behavior around 5100hz area. Crinacle's measurements also reveal that problem. However according to tests I did with tone generator on my unit, the problem area is narrower than what Crinacle's measurements suggests. Unit variation? Maybe. There is another cancellation area around 7700hz. There are few cancellations in this area which have very high Q. Usually ES-1A's 5-8khz response is *dark*. It prepares the listener to the fireworks that is going to happen in 10khz+ area.
10-20khz:Usually flat response from 20hz and 20khz is considered as *accurate* which is not the case all the time. Music we listen is recorded in rooms with speakers and well designed speakers do not have flat high frequency in room response. Therefore, headphones with flat 10khz response may sound a bit bright, too *airy* while listening to majority of recordings. This is the case with ES-1A. Is it a huge problem? No, actually I like it more this way. What is fascinating about ES-1A's high treble response is that there are no huge peaks that can kill the timbre of instruments. It's almost a flat line with few cancellation areas(which is normal). 007's have 2 spikes around 11khz and 12khz and I find very off putting. 009 also suffers from the same HF peaks. I find both unlistenable without EQ because of this. ES-1A's HF response is fantastic.
ES-1A vs 009 and 007.
009 has a bit more 3khz presence and that makes 009 a bit more detailed in the mids and low treble. However ES-1A sounds more detailed in overtones due to the huge emphasis on 8-20khz response. ES-1A bass response is way better than 009/S. 009s' lack of bass make things a bit hollow and shifts spectral balance a bit too much towards treble.
007 is darker than the rest, 007's high treble response is also quite powerful however there are 2 huge peaks in 007's HF response: one in 10khz, the other 12khz. These peaks can kill timbre of most instruments. As I said before ES-1A has super energetic treble but the emphasis is constant and controlled from 8khz and 20khz. This is very very important. Due to lack of mid presence, 007 sounds a bit more midbassy than ES-1A. For the same reasons ES-1A rumble harder than 007.
ES-1A with 007mkI pads sound the most detailed ouf of all.
Imaging/Soundstage
ES-1A's drivers are huge. I mean... huge. ES-1A's headstage does something only few headphones can: The headstage wraps around the head and sounds can come from every direction around the head. This is addictive. Normally the sound window is limited to L and R channels on headphones. ES-1A's drivers are so huge that, the center stereo phantom image presentation on ES-1A is much better than all other headphones I've tried. This is most fascinating thing on ES-1A in my opinion.
Comfort
About comfort, ES1A is kind of heavy but I found ES-1A bit more comfortable than other 2. I like loose fitting headphones more than hard clamping ones. Remember that, this is just my own subjective preference.
Conclusion
ES1A sounds open, fast, extremely detailed with a tonality that makes music more engaging and involving than 007 or 009 for me. I don't have problems with "ethereal"(like 009) sounding headphones. If you do, It's better to check other options. As a wrap up, I think It's safe to repeat what another reviewer said: "these are what the 009S should have been."
I'd recommend them with 007 pads.
My audio chain: HQPlayer sinc-M filters -> Soekris 2541 Black Filter-> KGSSHV Carbon > headphones.
