On-Ear Sealed Headphones Reviews

A classic in the world of professional and enthusiast headphones, and probably the world's most popular DJ headphone, the HD 25 has remained in the Sennheiser line-up in a small variety of incarnations since 1987 ... and deservedly so.

When I first heard them about 15 years ago there were very few expensive headphones available, so they seemed pricy at the time. They sounded great, though, and were a solid recommendation. In today's world of high-priced fashion headphones, and even higher priced high-end headphones, these very good sounding and highly functional cans seem like a real bargain for professionals and audio enthusiasts alike.

Let's take a look at the latest incarnation, the Sennheiser/adidas HD 25 Original.

Sennheiser/adidas HD 25 Original ($359 MSRP, $269 Street)
What I love about these headphones is that a quarter of a century ago the Sennheiser product team nailed great sound in the split headband design formula and they've had the good sense and gumption to stick with it ever since. Initially released in '89--which I am assuming from the original manual for the HD 25 that indicates a printing date of that year--it then gained the Roman numeral "II" in 2007, and the latest adidas Original version was introduced in early 2010.

Model Variants
I was unable to determine the exact differences between units over the years, but it appears to be very little. HeadRoom did have a pair of HD 25-1 with "Made in Germany" printed on them, which I assume are the HD 25-1 version. I would guess the pair I had are about 10 years old. The measurements were almost identical between this old headphone and the current adidas Original when I mounted the old pads on the new cans, so very little has changed over the last 10 years in terms of measured performance.

The adidas Original version is identical to the also currently available HD 25-1 II headphone, but for the color changes to the earpads and headband pads, and the adidas stripes and logo on the capsules. Both current models come with a second pair of velour pads. The roughly $50 price premium of the adidas Originals is purely cosmetic; if you're interested in these headphones and want to save a little money, just go with the HD 25-1 II as they will sound and work the same.

There are a total of six variants of the "II" headphones:

1. HD 25-1 II - 70 Ohm impedance; 1.5 meter cable with right-angle miniplug.
2. adidas Original - Like above, but with adidas color scheme.
3. HD 25-II* - 70 Ohm impedance with two meter cable and straight connector.
4. HD 25-C II - 70 Ohm impedance with three meter coiled cable and straight plug.
5. HD 25-13 II - 600 Ohm impedance with three meter cable and straight connector.
6. HD 25-SP II - The cheap version of the HD 25, without split headband; 85 Ohm impedance; different driver. This headphone sounds significantly different and not as good, and is not recommended.

* - no longer available.

Build Quality
These cans are built like a tank; virtually indestructible. The old pair of HD 25-1 I tested while writing this article are, and have been for a long time, popular headphones among HeadRoom employees. They saw much use around the office. In comparing the new adidas Original and the ten year old HD 25-1, other than the pads being obviously well used, I found little difference in the look, feel, and tensions of the various parts and adjustments. There were little obvious indications of wear on the matte textured outer surface of the headphones. All of which indicates a very robust design and manufacture to me.

This doesnt surprise me in the least. I've been to Sennheiser's plant and had a tour of their materials analysis lab. I've spent a lot of years with lab gear in the past, and they had some good stuff. My experience with Sennheiser materials and build quality is that it's top notch.

If you do manage to break the headphones, they are repairable and a fairly full complement of spare parts is available from Sennheiser.

Ergonomics
These headphones are quite light and have a well designed split headband, which together provide a very secure and reasonably comfortable fit on the head. The left earpiece can swivel backward or forward for one-eared use. Though the clamping pressure is a bit tight (which is important for secure fit and good bass response), the headphones are quite comfortable and easy to position on the head.

Though the headphones do not have any folding features to make them smaller for storage and transport, they are fairly small as is, and their durability will allow you to feel comfortable just throwing them in a backpack or milk crate. Because the headphone is light; the earpieces relatively small; and the headband easy to collapse into a single slim band, these headphones are quite comfortable when worn around the neck.

The ergonomics of the HD 25-1 II, coupled with the stellar durability previously mentioned, have made these long time favorites among audio professionals of all types. They are especially prized as great DJ headphones, and are regularly given custom paint-jobs to improve their humble looks.

Cable
Evidently, for durability purposes the cable conductors are steel. Many like to play with cables, so for those inclined the stock cables can be replaced with Sennheiser HD 600, or HD 650 cables, or compatible after-market cables. See video for details.

Is it worth it? I thought I heard the HD 650 cable as slightly smoother sounding, but it was a very small difference ... small enough it could have easily been me fooling myself. I don't like the idea of stressing the connectors, but I think the HD 600 cable using the standard cable routing might be something I would do.

Isolation
The isolation of the adidas Original is above average for a headphone of this type, and will perform well when isolation is needed. This is a good headphone for monitoring in loud environments.