I'd suggest the Shure SRH940s as something to look at as well. Close to the same FR curve and known for good sound. And the AKG 3003i's with a high pass filter have a FR curve pretty close as well and are definitely some of the higher end of the IEM market. Just in case IEMs are a possible answer.

brad34221 said:

It is to a degree, but being a semi-noob, I'm reluctant to show my ignorance!

Here is the deal, in the most simple way I can explain it. I run my HD 800s directly from my McIntosh C2300 preamp, without any type of headphone amplifier at this point. The headphone output stage from the C2300 does not have to "strain" to get to my desired listening volume. When I started using the HD800, the fidelity difference (quality of sound of the music I listen to) dramatically increased!! Night to day, mono to stereo, black and white to color, etc. If it wasn't for the music leaking, I would be 100% satisfied with my current set up. There is no DAC in use. 99% of the music I listen to is vinyl. I'm an "analog man".

My desire for headphone listening is due to my wife likes to read often while I listen to my music. We don't disturb each other this way, well at least until I acquired the HD800s. Now it's "turn your music down". I listen mostly to classic rock music, but I hate to be classified to a musical niche. With the AKGs, I never had that problem since they are closed. I don't like going back to them now, I've been spoiled !!!!!!

So this is where I am now, hoping to find a pair of cans that don't leak, but can compare to the "quality of the sound" of music that I am now spoiled with due to the HD800. I hope all this makes sense.........

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What do you look for ?  Replace or complement your HD800 ?
 
The point is it doesn't exist one close headphone that is even close to a HD800 because the strongest qualities of the Sennheiser flagship are related ot its open nature. So if you want to replace it , you will have to  downgrade something . The questions is what do you accept to downgrade ? 
 
For example for classic rock, We can easliy advice some very very good Closed headphones but none will reproduce HD800's sound.  Soung sig maybe but not more. 

I was in a bit similar situation recently. Except I did not have HD800, but Hifiman orthos HE-6 and HE-500.  They are different from HD800, but are also very airy and detailed, and sound fantastic with good sources and proper amps. However, they are heavy and leak sound like small speakers. When you have experienced and enjoyed HD800 or some great orthos, there is no way going back to M-50 (or similar level cans from Germany) for any real musical thrill.
 
So, I definitely wanted to keep the HE-6 and HE-500, but did not want to buy very expensive closed hp's before knowing if I can enjoy them. So, TH-900 was out of the picture for the time being at least (plus people say it leaks quite a lot of sound).  My route in searching for suitable and "good enough" closed cans has been ATH-ESW9A (very portable, signature AT wooden highs, but only on-ear and leaks a bit: I still love them but do not use them at home anymore that much), ATH-A900XLTD (comfortable, different league compared to M-50, but still reasonably priced – especially the non LTD model, which is probably 95 % as good as the LTD), and finally, due to very attractive new pricing in the UK, Denon AH-D7100 (very light, great fit and comfort, sounds IMHO truly great after some serious burn-in, even from portable sources).
 
For the OP's situation as he explained it, I would also recommend keeping the HD800 and TRYING at least some of the following closed cans:
 
- ATH-A900X, generally available for 200 USD and even less. If they feel and sound good enough, you may try to find an LTD while they last, for  USD 100-200 more.
- ATH-W1000X for the AT smooth wooden highs. I have only heard them briefly, but they are supposed to be slightly better overall than A900X. May leak a bit and may benefit from pad modifications according to reports.
- Denon AH-D600 or D7100, in case you find them for less than 50 % of original price. I have only heard D7100 and I am very happy I bought them, even if a lot of people seem to really hate them, comparing them to the older D7000 and complaining about their original high list price. D600 is currently quite attractively priced and might be 90 % as good as D7100.
 
I doubt any closed cans would fully replace the HD800's, if that is the sound you want, so finding closed cans to complement them is probably the only solution you would not regret later on. Then you have to decide which price level would fit your budget.

andrew_wot said:

  Not related to OP question but calling HD800 "shrill" when comparing to DT770 and T5P is not quite fair, to me it's opposite, but as always "setup matters" rule applies. 

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What about this expression - "over-the-top treble" ?

money4me247 said:

  If you read OP's post carefully, you will notice that he NEVER mentions anything about sound signature or balanced frequency response. He also only has 2 posts under his belt. You guys are all assuming that he wants a sound signature similar to the HD800 + balanced frequency response, but the only thing he specifically mentioned wanting was "FIDELITY," which can be defined as detail & clarity vs general sound quality.
 
I think a lot of the discussion in this thread might be going above & beyond in detail of what OP is looking for, and all this in-depth sound signature discussion may be more confusing to OP than helpful.
 
But by all means, please continue this riveting discussion of which closed headphones has the closest sound signature/most balanced frequency response. I am personally finding it very interesting hahah.

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Unless he explicitly states to the contrary, it is logical to assume that he wants headphones similar in the sound signature to what he is used to by now. Further, it would be an act of charity to one's fellow human being, especially now at the time of Christmas, to not recommend him headphones with the recessed middle frequencies. The word FIDELITY in relation to the sound signature of particular headphones can very nicely be described as ' faithful reproduction of the balanced live sound of musical instruments'. Interestingly, each time I hear a live music I never hear middle frequencies that are recessed and it is safe to assume I never will. If natural sound is balanced then it would be an act of evil to recommend someone headphones with unbalanced frequencies response. 
T5p is still [together with ATH-A900X] A - closest to the sound signature of HD800 and B - closest in sound quality to HD800. If the sound quality is the primary consideration then ATH-W3000ANV is the answer [out of production and around 1300 dollars for used ones on head-fi]. I would even pick W3000ANV over HD800.
Happy and peaceful Christmas to everyone on this thread and beyond.

brad34221 said:

It is to a degree, but being a semi-noob, I'm reluctant to show my ignorance!

When I started using the HD800, the fidelity difference (quality of sound of the music I listen to) dramatically increased!! Night to day, mono to stereo, black and white to color, etc. If it wasn't for the music leaking, I would be 100% satisfied with my current set up.

So this is where I am now, hoping to find a pair of cans that don't leak, but can compare to the "quality of the sound" of music that I am now spoiled with due to the HD800. I hope all this makes sense.........

Click to expand...

 

zorin said:

  Unless he explicitly states to the contrary, it is logical to assume that he wants headphones similar in the sound signature to what he is used to by now. Further, it would be an act of charity to one's fellow human being, especially now at the time of Christmas, to not recommend him headphones with the recessed middle frequencies. The word FIDELITY in relation to the sound signature of particular headphones can very nicely be described as ' faithful reproduction of the balanced live sound of musical instruments'. Interestingly, each time I hear a live music I never hear middle frequencies that are recessed and it is safe to assume I never will. If natural sound is balanced then it would be an act of evil to recommend someone headphones with unbalanced frequencies response. Happy and peaceful Christmas to everyone on this thread and beyond.

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hahah... zorin, your attention to detail is amazing & your wish to provide amazing natural sound is definitely a noble endeavor. I was simply worried that OP might be getting a bit overwhelmed by all these very detailed & personal sound signature impressions. A lot of the impressions that posters are throwing out can be highly personal and there is no reason for us to argue about sound signatures or specific personal impressions for certain headphones.
 
since OP did not specifically state that he wants the exact same sound signature, I think it would definitely be to OP's benefit to try out other headphones w/ great clarity & other positive sonic attributes that may not be perfectly neutral. there are a lot of great closed headphones out there! There doesn't seem to be any closed headphones out there that can duplicate everything about the HD800 exactly, so there's no harm in trying out other high-quality closed options. We all hear things differently, so there are a lot of different high-quality headphones that people find enjoyable regardless of their measurements.
 
If OP gets a chance to demo any of our suggestions, I would love to hear OP's thoughts about their sound signature & quality. That probably be really helpful in narrowing down recommendations.
 

After reading the thread on DT660s and classical music they might be a good starting place for the OP to start looking at closed back headphones. Try them out at a guitar center or something and kind of use them as the reference. If whatever other phones you're looking at don't sound that good or better to you move on. That is if you like them, which I think is a good possibility after reading your first post again.

I'm finding the HD800 and Alpha Dog to share neutrality and detail.  The HD800 has the wider soundstage and better microdetails.  However, the Alpha Dog has the more thicker mids which make vocals and acoustic guitar fantastic.  My votes goes to the Alpha Dog if you want neutrality and detail.  However, the amp you use with this planar magnetic headphone will make a huge difference in listening outcome.     

I love my hd800s, but Dennon D2000 are my go to portable headphones when I don't want music leak.

I would suggest the ZMF v1 and a good amp.

Custom iems I reckon. Comfort isolation and sound quality aimed at the high end that the hd800 is firmly in. The sound signature will be different of course but will be just as enjoyable as a complement to the HD800's.
I can give no recommendations as my budget has gone on the sennheiser and I have lots of iems for out and about.
I am in the process of getting acs custom tips for my Sennheiser ie800 iems which are superb iems but come loose.
Don't think they're going to approach proper customs but they're good enough for me and you can at least see what an iem can achieve in Sq if you gave them a listen