Okay - I've now tried the mod too! I got my T1s the week before last and left them for about 5 days to burn in with the Isotek CD (track 2). Then I exchanged the plug for a balanced one (my first DIY soldering job - not too bad!).... and all was set for a comparison to my other headphones:
HD650 - recabled with APS V2 balanced cable and modded by removing all foam from inside the cups and behind the backs of the driver per the APS website description (I find this makes them much faster, clearer, more open and less veiled than in the stock configuration)
HE-6 - recabled with a balanced AmpCity Fidelis silver cable
PS1000 - stock cable but re-terminated with a balanced plug
The other elements of my system are in my signature block. The music I tried was pretty varied - classical, indie, rock, R&B, folk, country, jazz, African, pop, electro...etc. All in all, I think about three hours disappeared!
Everything that follows is just what I heard/my opinion. YMMV.
Firstly, I tried the T1s unmodded:
- Vs HD650: T1 was (unsurprisingly) much more neutral and transparent with better clarity. HD650 was warmer with more bass - particularly mid bass, less so down low. With well recorded tracks, I'd prefer the T1 95% of the time. With modern mainstream recordings, I think the t1 is too hot though and its time to reach for my comfy slippers (aka HD650).
- Vs HE-6: Very tough one. I was amazed to find my HE-6 actually sounded darker and less 'lit-up' in the treble than the T1s (I've always considered my HE-6 to be the brightest headphones I own, sometimes too much so). The clarity on the HE-6 was also better than the T1 and they have a much larger and more open sound. However, the mids on the T1 were definitely 'lusher' and although I couldn't really say why, I found my head nodding and foot tapping along to the music a lot more with the T1! That treble peak on the T1 was bothersome though, particulary with any recordings prone to sibilance or that already had quite a hot treble.
- Vs PS1000: Polar opposites. I love my PS1000s - they are incredibly open with a wonderfully expansive and realistic soundstage (much more realistic than the weird soundstage produced by the HD800 in my view!), crystaline treble with unbelievable clarity (the best clarity of any headphone here) and really fun bass that hits hard albeit not particularly deep. Despite not being even vaguely neutral, I somehow still find them very 'natural' to listen to - the timbre of voices is very realistic and the bass is not exactly accurate but somehow seems more real and less 'in your head' than most other headphones. The T1s are soooo much more neutral but they also have lusher mids (my main criticism of the PS1000 is that the mids can sometimes sound a bit sucked out). I would say the T1s are the most neutral headphones I've listened to that are also fun to listen to (I didn't buy the HD800 for exactly this reason - I found it really boring, despite its technical strengths).
So overall, the T1 was shaping up to be the "most fun neutral headphone" I had ever heard...but that treble peak was making my ears hurt and I definitely prefered other headphones in my collection for any recording with a hot or even obviously present treble and that sssibilance was really bugging me.
I then tried the mod. I used felt furniture floor pads for the rear part of the circle (about 4mm thick) and some art felt for kids from amazon (about 2mm thick) for the front section under the driver (which colour should I use? Even though no one was going to see it, I thought a crazy purple was kind of fun!)
Firstly I tried it with just a small circle of the thin (purple!) felt. However, I found this didn't make much/(any?) difference so pulled everything apart again and went for a full purple crescent instead......much better!
To be honest, it was getting pretty late by now and my son is currently waking up at 5.30am so I knew I needed to get to bed! I felt the comparison between the T1 and the HD650 and PS1000 were pretty much night and day, so I didn't bother repeating these and instead focused solely on the HE-6, which I thought was much more similar in nature.
With the mod:
I still find the T1 is brighter than the HE-6, but the gap has narrowed considerably. Sssibilance is now much better controlled. I would sum up the characteristics of the two headphones as follows:
HE-6: Superior clarity and blacker background. More relaxed and smoother treble (even with the mod, My T1 treble still has some peak). More open soundstage - for 'large hall recordings' this works really well and conveys much greater ambience than the T1, for smaller venues or studios, the HE-6 can sound a bit distant. The base extends deeper with more punch down low (my adams apple 'wobbles' much more with the HE-6 than the T1!)
T1: More mid-range centric with a lusher sound. Less open but still provides a realistic soundstage and images better (i.e. more realistic instrument placement). Less clarity but somehow images better. SSssibilance still occasionally present but much reduced and much less bothersome. The bass seems tighter but also has more body to it. Still not in HE-6 league for distortion free punch, extension and detail though. Not sure if it's the mod, but they do sound a bit muddier when the tempo quickens and the volume increases?
Which headphone wins in each of the individual areas?
Treble - Clear win to HE-6
Mids - Clear win to T1
Bass - Comfortable win by HE-6
Clarity and detail - Comfortable win by the HE-6 (I am wondering if upgrading the cable for the T1 would improve things here - the magnitude of the win is similar to what I experienced upgrading from the stock HE-6 cable to the Fidelis)
Soundstage - HE-6 for large scale recordings (big halls, outdoor...etc), T1 for more intimate recordings
Imaging - Comfortably T1
Separation/layering of instruments - Hard to call. Very different presentations. The HE-6 never distorts and remains completely controlled even at volume allowing you to hear everything (it sounds as if you can hear every individual voice in some choral music!). However, the T1s more intimate presentation can work better on some tracks where the HE-6 occassionally all sounds a bit too distant (possibly something to do with the waveform/shape/focus of the sound waves coming from the planar drivers??)
PRaT- Tie (both quick)
Comfort - Tie
Ease of amplification - T1 by a zillion miles (but my current setup is great with the HE-6 so this is not a factor in this test)
To sum up: In terms of line by line specs, I feel the HE-6 beats the modded T1 in most areas. If I want to really hear everything about a piece of music (i.e. 'analyse it') I will pick up the HE-6. BUT..... as I've said above, there's something about the way the T1 plays music that instantly draws me in and I suddenly find myself nodding my head, tapping my foot, playing air guitar or imaginary drums.... you get the idea! For some types of music, the PS1000 remains the undisputed king in this area but its genre bandwidth is more limited. For an all rounder with a neutral-ish character (or neutral-lush! See what I did there...?!), which makes you forget the equipment you're listening to and allows you to enjoy the music, I think the modded T1 is hard to beat. I suspect it will be my 'go-to' headphone for some time.
[That said - I may keep playing with the mod a bit more. Now that I have listened for longer, I feel the treble smoothing has possibly come at the expense of reduced speed and clarity. I think it's worth experimenting further with different sizes and thicknesses of felt!]
Sorry this turned into such a long post. I found it quite useful to write though; it helped me organise my thoughts! Hopefully you'll find it somewhat useful too. BTW, for anyone scared of doing the mod, don't be. It was REALLY EASY and is completely reversible!