Denon ah-d1001 and Denon ah-d1100

One is smaller

I believe the 1001 used the Micro Fibre driver in slightly smaller form (40mm) as used in the 2000/5000/7000 series.

The 1100 uses a different diaphram and it is 50mm. I can't comment on the SQ of it but it measures worse than either the 1001 and Creative Aurvana Live (!) which in essence is the same phone, manufactured by Fostex (as the Denon 1001). It has a slightly different casing (2part).

Personally, I would get the CAL. Available for £50 or thereabouts and a great HP if you dont want to spend Sennheiser HD650/Denon AH-D2000 money.

Bass is full, deep though a tad soft in ultimate terms but doesn't bleed into the lower mids. There are mods to get around that.

Good luck with your quest.

regards

The AH-D1100 are bassy headphones but I don't think its overpowering.

It would depend on your musical preferences, really.

I upgraded from the D1001 to the D1100 and I thought it was a vast improvement. Fuller sound (maybe because of the emphasis on bass) and less harsh/sibilant which I found the 1001's to be at times. 

They're tighter and isolate a bit better too if that matters to you at all. 

http://www.innerfidelity.com/images/DenonAHD1100.pdf

http://www.innerfidelity.com/images/DenonAHD1001.pdf

http://www.innerfidelity.com/images/CreativeAurvana.pdf

Whilst measurements dont tell the whole story and cant compensate for personal taste they do explain a lot.

As you can see, the D1100 has a vast low frequency hump from around 200hz downwards.  This may make them sound warm and 'bassy' and takes away what some perceive as sibilance but it is hardly near neutrality. Both the 1001 and CAL measure far more evenly though even they still have a lot of bass. Quite a few people have tried to get more bass out of the 1001. The difference between that model and the CAL is, I believe, mostly the pads. Personally, I would aim for around a 2db reductions of bass on the CAL's but your mileage may vary.

regards

If you want something more neutral then the 1001 is certainly the way to go. They were a bit too flat for me but still pretty decent headphones.