So as for new headphones for my cheap keyboard / to listen to classical recordings on my computer:

I think I am looking at
$100 - $250 pricerange, perhaps up to circa $400+ if I had a great reason to go there. (Not likely...)

Thank you now for whatever patience you put into reading or responding.

Desired Features

• Able to work with my keyboard etc.
• Closed / low-leakage (despite cost in sound quality. I assume open would be enough to avoid people in other rooms, but I would play more freely if there was little chance of being overheard.)
• Doesn't waste my hearing or get me paranoid that I am wasting my hearing; doesn’t get me overly audio fatigued.
  (And closed will keep out more random noise, but does it have drawbacks here?)
• Durability / Reliability, and, secondly, fixability.
  Would be nice to be able to plug in any connection cable, but never mind.
• Appropriate sound quality.
  Also, I think I read something about headphones having cables that jostle and make their own noise-signals too often. Obviously, that might be problematic if I am using them to actively play keyboard, and can't switch out for other cables.

BeyerDynamic DT 770 80 ohms
In particular, I am interested in BeyerDynamic DT 770, probably the 80 ohms, if that’s not too much resistance
Alternatively Sennheiser 280 Pro.

Now, after reading reviews, I somehow trust build quality of the DT 770 more, but I prefer the description of the sound of Sennheiser. Why? Mostly because of the complaints that DT 770s are just a little too treble-y, or (sharper complaint) bright to the point of being eventually fatiguing. (I read that the 80 ohms DT770s are least aggressive in treble.)
I want something mellow enough but engaging. …?


So, how concerned should I be about the treble of the 770s versus similar Sennheisers-- for enjoyment or for hearing safety?

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Best, Most Reliable Closed Sennheiser in this Price Range
And as for Sennheiser: presumably the point is to spend a fair amount of money and get -open- headphones. So by insisting on -closed- 'phones, perhaps I am essentially muting Sennheiser's advantages….

In Sennheiser, I would default to the HD 280s.

Shopping amazon, I could favor an unused ‘old model’ (rather than 'new model'), because I am paranoid about quality dropping, though the old version might be newly produced enough that there's no point in caring. Amazon also has a more expensive 380, which appears to be phased-out-- perhaps not the way to ensure quality.

There is also 598 Cs / 569 (why distinguish?), which are presumably fancier soundwise. But how can I trust them to be as durable/reliable as the 280s?-- the amazon.com reviews also have a few complaints about the earpads flaking into annoying black specks https://www.amazon.com/product-reviews/B01L1IIF1A/ .
Ignoring $ money. Is 569 better overall? Or better enough sound-wise or cable-wise to be worth its drawbacks?

So again, with Sennheiser I might literally feel safest buying 'old model' 280s (which would have to be from amazon... but I might feel safer buying (new models) from sweetwater or sennheiser, since amazon.com is an open marketplace.
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Summary of Questions
So:

• 1. What should I think about build quality of these Sennheisers, especially versus the DT 770s?
• 2. Of these Sennheisers, which is most durable? Which is best?
• 3. In looking for nice enough closed headphones, what other Sennheiser, or other brand’s product, should I be considering here?

And also

• 4. How irritating/damaging might the trebles be on DT 770s, really, and (opinions! controversy!) which of the headphones mentioned here has more pleasing sound?
• 5. Should I expect 80 ohms to work well with keyboards (Williams) and laptops (Surface)?

The DT 770 is fine for me. Solid resistant. Straight cable.

Fischer Audio FA-003 ticks all your boxes. I have had a pair for 5 years. They are a very open sounding closed headphone.

Update: Unfortunately I just checked and they are discontinued.

They look to be identical to the BrainWavz HM5, which can currently be bought on sale for $63. If they are the same, then this is an absolute bargain for a full size, efficient and comfortable closed-back headphone with a very neutral sound.

I just picked up some BeyerDynamic DT250s, 250 ohm. Really nice - balanced, smooth, not harsh. 80 ohm would be better without an amp.

For now, I am thinking

AKG K553

or possibly some $200 or less closed Sennheiser (280 or maybe 569.)

Thank you--
winterflower

You're better off testing your desired cans, or, order them both online and return the loser.
Check out Sennheisers's store for refurbished cans: might get a good deal there: https://en-uk.sennheiser-outlet.com/shops/index.php

I have no way to compare my DT770 (250 Ohm) to anything but I've never found anything annoying in the treble range so far...

The biggest gripe audiophiles have about the DT range is that they aren't as comfortable as the Sennheisers. Guess it depends how long you're going to practice for as to whether that matters.

I've never owned Beyer DT's. But the DT770 felt very comfy when I tried it in the store. Very.

And I used to have a DTX900 that was super comfy, too. My mother-in-law now uses them to listen to the TV. They're now eleven years old ... and still comfortable.

I've not found comfort to be a problem with the Beyers.

I agree with Mac3 ; my Beyer is very comfortable, I never stop playing with any comfort problem.

These things tend to be head shape dependent and also, audiophiles that do these reviews tend to do long sessions of gaming (6-8 hours) so the accusation isn't that they are persay uncomfortable; rather, they become so after prolonged use.

For a digital piano, the Sennheiser HD599 are great in my opinion if you live in a quiet environment (due to their comfort and stereo).