Those are small criticisms of what is, overall, an amazingly well-designed product. Though the M-100's performance doesn't quite match that of the Sennheiser Momentum and the AKG K551 (below), its design, build quality, style, and accessories allow it to compete favorably with them at its $310 price. And if its street price drops the way its sibling's price has (I've seen the M-80 for as little as $150), the M-100 will be a serious bargain.
AKG's K701 (currently available as the $350 Q701) was hailed upon its release as one of the best headphones in the world. The K701 and Q701 have since been surpassed by headphones with even higher prices, but both still sound great--the K701 has been my reference headphone for five years. The company has attempted to match the open-design K701's performance in a closed headphone with the $330 K551. In a nod to today's dominant listening sources, the K551 features a cable with an Apple-style, three-button inline remote and microphone module. (The K551's sibling, the $300 AKG K550, has a longer, thicker cable for home use, and omits the remote/mic module, but it is otherwise identical.) The K551 is available in black or white, each with silver accents. The only included accessory is a 3.5mm-to-1/4-inch adapter--this is the only model of the four discussed here that comes without a case or bag.
In my opinion, the K551's clean, modern design is a step up from the busier, space-age styling of the K701. The earpieces are large, black circles that evoke vinyl LPs. The stainless-steel headband adjusts in discrete, numbered increments; this approach isn't as convenient as the K701's elastic strap, which requires no manual adjustment, but the K551's design nevertheless permits a quick, consistent fit. The thin, black cable sports the aforementioned remote/microphone module, which is relatively small. I found the buttons difficult to distinguish by feel, and the thick plastic around the cable's 3.5mm plug may prevent it from fitting through the headphone-jack opening in some device cases. The K551's earpieces fold flat for travel, but the resulting size isn't very compact.
The angle of the earpieces adjusts both side-to-side and up and down. This is good, because I found that the K551 requires careful adjustment to achieve optimal bass response. Finding the right positioning was initially tricky (I angled the earpieces slightly up and toward the back of my ear), but I quickly learned to put them on easily and consistently. Thanks to this precision adjustment, the K551 creates a tight seal without clamping too strongly on your head, and I found the K551's earpads to be very comfortable.
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