Sennheiser HD 25

Name: Sennheiser HD 25
Brand: Sennheiser

A 70-ohm closed supraural monitor with a split headband and one driver that swings up over your temple. It is the DJ and location-recording workhorse that has never needed a redesign.

Overview

Seventy ohms and a frequency response of 30-16,000 Hz. Those are the numbers Sennheiser's own dealer literature put on the HD 25, and they say most of what the headphone is for. A 70-ohm load is easy enough for a mixing console's headphone amp or a portable recorder to drive. The closed supraural design with dynamic drivers keeps your cue mix from bleeding into the room, and it doesn't need a quiet room to be useful. Sennheiser's distributor copy described it as a lightweight and comfortable alternative to heavier sealed headphones for professionals who spend a great deal of time wearing them.

The mechanical arrangement is what made the HD 25 a fixture. The adjustable split headband sets the fit on each side independently, and the audio cable enters on a single side, which keeps the lead out of the way when you are moving. One driver rotates off the ear and onto the user's temple, so a DJ can cue on one muff while the other ear stays on the booth, and a location recordist can keep one ear on the room. Recording Engineer (December 1989, p.122) described this arrangement in its new-products column: the supraural design, the adjustable split headband for optimum fit, the single-side audio cable, and the rotating driver for one-ear cueing.

Dealer listings of the period put the HD 25 at a manufacturer's list of $199.00, and one later distributor sheet shows $229.00. That is professional-monitor pricing, not consumer-aisle pricing. The range of 30 Hz to 16 kHz is a monitoring range, not a hi-fi showpiece range. The HD 25 is not sold on extension or on spaciousness. It is sold on isolation, on staying put on your head, and on surviving the kind of use that eats lesser headphones.

The same dealer literature notes that replacement parts were stocked for the entire Sennheiser headphone line, which matters for a headphone built to be worn hard and used daily. A closed supraural monitor with a rotating driver is a mechanical object as much as an acoustic one, and the parts pipeline is part of the reason these stay in service. Collectors and working engineers both tend to judge the HD 25 on that basis: not as a museum piece, but as a tool whose longevity is the whole point.

One warning for anyone chasing one on the used market: the HD 25 name has been applied across a long run of variants and revisions, and listings are not always careful about which one is in the box. The period documentation here describes the original closed supraural, 70-ohm, 30-16,000 Hz monitor with the rotating driver and split headband. Confirm the exact variant before assuming the specs above apply.