The Historic Beyerdynamic DT 48 E (25 ohm)
Yes, historic. The Beyerdynamic DT 48 model has been in continuous production in a variety of forms since 1937. That's pretty historic ... I can't even remotely think of another headphone like that.
Let's take a look ...
The Beyerdynamic DT 48 E ($529 MSRP) is a full-size, sealed headphone intended for use as a monitor headphone in pro-audio studio and location applications. These cans are designed to take the rigors of the road, and they certainly will. There are two impedance variants of this model (25 ohm and 200 ohm); and there is an audiometry version, the DT 48 A.00.
Styling and Build Quality
These headphones have all the styling of a precision stainless steel, cap-head, shoulder bolt, which is to say, I love the way they look. It's not often that the discussion of build quality and styling are identical, but such is the case with the DT 48 E. Extremely sturdy nickel-plated spring steel bands for the headband, extension arms, and earpiece gimbals are firmly held together and pre-tensioned for use by a tidy assortment of bolts, screws, spacers, washers, and nylon-insert locknuts. This headphone is meant to be able to take a beating, and be repairable when over beaten. To see it is to understand it; its beauty is in its utility. If you have the fashion sense of a ham radio operator like I do, you'll love the look of these cans.
Ergonomics and Comfort
You WILL listen to these headphones. From the moment they apply their death grip on your head, and the suction cup-like seal around your ears is made, you know your dealing with a headphone that intends to be heard, and really doesn't care how you feel about it. I'm not saying these headphones were uncomfortable, in fact, I was surprised how comfortable they were considering how much clamping pressure they had. There have been warnings from owners to regularly check to drain sweat. I'd say they were very effective at sealing up your ear-holes with little collateral discomfort, but it did feel a bit claustrophobic to me.
I wasn't a bit surprised to hear for myself and see in the measurements that these headphones had great isolation. Among the best I've seen a sealed, full-sized headphone --- that's a good thing for a monitor headphone. Coupled with the rugged build quality, their ability to provide the listener very good isolation makes these headphones very good for portable professional recording applications where intelligibility rather than fidelity is required.
Fig 1 show the isolation from outside noise. This is a very good result; possibly best in class.