My short Youtube review of the SRH 1440:

http://youtu.be/ro9ddGGqNPo

Photos of the SRH-1440:

http://dalethorn.com/Photos/Nikon9300/Headphone_Shure_1440_01.jpg

http://dalethorn.com/Photos/Nikon9300/Headphone_Shure_1440_02.jpg

http://dalethorn.com/Photos/Nikon9300/Headphone_Shure_1440_03.jpg

A quick non-destructive mod I did, where I removed the thin foam backing from the spare earpads for the 1440 and the 1840 and inserted those foams into the 1440's earcups -- changed the 1440's high end from sounding more like the 940 to sounding more like the 1840. A lot like the 1840 in fact, and so far no downsides -- no peaks or dips in the response and normal HF extension.

http://youtu.be/mKo2FvzssLI

This is an extended look at the non-destructive mod I did to the SRH-1440 to bring the sound more in line with the SRH-1840.

The bass response of the Shure 1440 is very slightly less than the Shure 1840's bass, and the 1840's bass is very slightly less than the Shure 940's bass, which in turn is very similar to or a hair less strong than the Sennheiser HD800, which is my usual reference for nearly flat or neutral bass. So if I could say that the Senn 800's bass were at zero decibels (db) in the 40 to 80 hz range (just using the mid to lower bass range as an example), the 1440 might be about 2 db weaker at the top of that range and 4 to 5 db weaker at the bottom of that range. At least that's how it sounds, although measurements seem to agree with that too, plus or minus a little bit.

I did a brightness mod on the 1440 which was simply inserting Shure foam backings from extra earpads into the earcups, and that mod also improved the bass slightly. So with that mod the highs became much like the 1840 but smoother I think, and the bass improved to the point where it might range from 1 to 3 db weaker than a Senn 800 instead of 2 to 5 db weaker. I was very impressed with the sound resulting from that mod, and was hoping against hope that some other persons would do a critical review of it. But I don't think the number of 1440 units sold were sufficient, or the customers who bought them and reviewed them were not so inclined, and so that modded sound is still pretty much an unknown in the world of headphones now.

Edit: I have now and have had several other headphones where I could hear and feel significant fundamental tones at 20 hz, and even some response at 15 hz which was fundamental and not just harmonics. It's important to know what those sound and feel like in the context of what I'm going to say about the 1440 and 1840. I listened to those tones from different sources with both the 1440 and 1840, and I don't think there is a significant response at 20 hz with either one, although the response at 30 hz seems fair. I suppose the response just drops off below 30 hz somehow, and I don't know why that is. Maybe the 1440 and 1840 don't couple to my ears as well as they do to the measurement head.

Well, I'm not able to measure what the foam does exactly, so part of this is conjecture. What I expect that it does, to relieve mostly the irritating parts of the highs without suppressing the treble overall, is it selectively bounces the highs around in those tiny foam cells which softens them somehow, perhaps lowering the energy of the most aggressive of those freq's without killing the rest of the highs. It does seem to do that well, and after the mod the tone sweeps I did up to at least 12 khz showed those highs were still present in pretty much the proper quantity. In other words it didn't dull the treble, which is a small miracle. But there is a danger of losing detail if highs get smeared, so you want to check carefully for that with any mod, and especially if you use non-Shure foam.

The HD600 is the classic neutral headphone, and would give you the best balance. The SRH1440 is clearer, but slightly brighter. If you performed the modification I described, and added the Shure foam inserts into the earcups, then the 1440 should sound more like the HD600.