Sennheiser HD 650 Reference Level Headphones 
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Written by Bryan Southard   
Saturday, 01 July 2006

The consumer headphone market has evolved considerably over the last 30 years. Headphones have been used for better than a half-century as an integral tool in the studio for recording and mastering due to their accuracy and immediacy. As a teen, I owned a pair of higher-end headphones that I used to defy my music curfew. They allowed me to listen to my raucous music at concert volumes without disturbing or, better yet, even alerting the rest of the household. Although the sonic pureness of headphones has rarely been in question, the fact remains that headphones, regardless of size, have always been plagued with the reputation of being fatiguing to both wear and listen to for extended periods of time. Additionally, there has been resistance from many audiophiles, who place huge stock in soundstage accuracy and instrument placement.

Sennheiser is no newcomer to the world of headphones. In fact, most recognize Sennheiser as the world leader in headphone transducer technology, as well as microphone, wireless and infrared sound transmission. Founded back in June of 1945 in Wedemark, Germany, following the end of WWII, Dr. Fritz Sennheiser and his team of engineers embarked upon a journey that has led the company to the top of their market.

The HD 650 is the flagship of Sennheiser’s consumer headphone line. Retailing for $499, the HD 650s employ a dynamic speaker configuration with an open shell design. The HD 650s have a frequency response of 10 Hz to 39,500 kHz. With headphones, the only statistic as important as sound is comfort. The HD 650s weigh in at 260 grams or just over eight ounces, making them an extremely light load for your neck to bear. The HD 650s come with the standard 6.3mm jack, as well as a handy 3.5mm adapter for smaller pieces, such as iPod and other portable devices.

The HD 650s come handsomely packaged in a silver hinging case that’s nicely fitted with foam to protect your investment. Upon further inspection, the HD 650s are a very sexy piece of gear. The outer headphone is constructed with a high-gloss metal-flake plastic that looks like a million bucks. On the external part of the earpiece are matching gray, perforated screens that provide a view into the backside of the speaker array. The speaker cups are oval in shape, measuring four inches vertically and three inches across, and are fitted with a soft, velvety fabric. An interesting feature: the cords have two-pin connectors that plug into each of the ear cups. If you have a shorting issue with the headphones, the cable can be easily replaced. Those who use wired devices, such as headphones and game controllers, for extended periods of time know that the cables can someday fail if they are used excessively.

Headphone Fit
There are no two heads or two sets of ears that are the same. Therefore, the best fit for headphones for you is determined the old-fashioned way, by trying them on. There are a few basic configurations for headphones. There is the common in-ear style, often used with iPods or other portable devices. Then there is the over-ear style that sit on top of the ear, and then the enclosed style like that of the HD 650s. After using each of these on a regular basis, I offer this assessment. In-ear is convenient for portable devices, but often allows the majority of bass to escape, unless the earphones are fitted with sealing earpieces. (This excludes the professional in-ear models that are used by most touring musicians.) On-ear can often be the most comfortable of the batch, but offers zero noise isolation and, again, they allow bass information to escape. Enclosed headphones like the HD 650s offer a lower-noise experience, along with improved dynamics, due to a more controlled inner environment.

I utilized a variety of different sources to best evaluate the HD 650 headphones. My primary source was a Sonic Frontiers Line 3, outfitted with Headroom headphone circuitry. This tube stage headphone amp has been a reference of mine for many years. I additionally used the output from my Kenwood DV-5900 and DR-5900 to test the HD 650s on a moderately-priced source. Lastly, I used my iPod with MP3 files.

Music and Movies
It was suggested that the Sennheiser HD 650 headphones were not a good match for lower-powered portable devices, such as my iPod, because they could not produce adequate volume. I am happy to report that they were wrong. The HD 650s provided as much or more volume than I can achieve with the stock Apple headphones. They seem considerably louder, in fact, due to the hugely increased bass response.

I started with Eric Clapton from his Unplugged CD (Reprise/WEA), using my Apple iPod as a source. “Lonely Stranger” provided me with an instant taste of what these headphones can do. There was major improvement in the bass and overall tonal balance. As Clapton slowly plucks his strings, the improved decay was greatly apparent.

One side of me hesitates to recommend $500 headphones for use with a $250 player, yet it sounded fantastic. I switched to my Sonic Frontiers setup and again listened to “Lonely Stranger.” Although I heard instant improvement, it was clear that the HD 650s were making everything they were plugged into sound great. There was solid isolation from the outside world. I paused for a moment to notice the sounds of my sprinklers running outside and TV playing in the upstairs room. Once fitted with the HD 650s, there was almost complete silence. For those with children – I was unable test this for you.

I compared my reference system using my Revel Salon speakers, a system that retails in the six figures, and noted that although the HD 650s didn’t outperform the Revels with dynamics, in many ways they kept up. They provided more immediacy and aural impact. Over the years, headphones have gotten a bad rap. They have been used by many but never fully respected in the audiophile world. True enthusiasts wouldn’t part with their beloved soundstages and three-dimensional imaging that their traditional speakers provided. Okay, so the HD 650s will not project the images through your front wall. On the other hand, they did provide a quality listening experience that you could only get with speakers costing 10 to 20 times their price. Bass response was huge and they had the knack for making instruments sound real.

Being fortunate enough to own one of Clapton’s signature Martins, I proceeded to humbly play one of his tunes and felt that the Sennheisers made the Martin tone most distinguishable: a great testament to accuracy. I moved to the Kenwood set-up and, although my reference system provided more information, the tone remained consistent with the other sources tested.

I loaded up the newly released 10,000 Days CD from Tool (EMI/Virgin) and played song nine, “Intension.” This cut starts with ambient noise that falls somewhere between a soup kitchen and the jungle. Information was clear and precise. There was very concise definition between instruments and a sonic air that separated them nicely. The occasional beat of a large kettledrum provided very low and accurate information. My room has been measured down to 10 Hz and the HD 650s provided every bit of low information. Of course, they lacked the physical impact of my speakers, but they nevertheless provided the balance necessary to experience a full-range listening experience. The bass guitar on this cut was eerily solid and projected with good authority.

The Downside
Headphones will not replace traditional speakers and, although they are the kings of accuracy, they are not comfortable to listen to at high volumes for extended periods of time. Some will find the HD 650s to be the most comfortable pair of headphones they have ever worn. Others may not be comfortable for long listening sessions. I fell in the middle. Although they are the most comfortable enclosed headphones I have used, they still cried to be removed after an hour or more of heavy listening. This was largely due to my head shape. I have a narrow jaw and muscular neck, so all headphones of this style tend to rest on my neck near my tonsils. I circumvented this issue by adjusting the HD 650s to ride higher on my head. This helped for longer listening sessions.

Although headphones have been part of my world for many years, they have been primarily relegated to my portable devices for exercise. I have a dedicated theater for listening and have no volume restrictions, so why would I need headphones? Doing this review was an eye-opener. Although the HD 650s won’t position a soundstage like traditional speakers, they will provide dynamics that are only rivaled by floor-standing speakers that cost as much as 10 times more. Bass was solid and quick and provided me with a live music feeling. The midrange was adequately sweet and liquid to made instruments sound very natural. High frequencies were a real joy. Due to the fact they can often get lost in an open room and cancelled by ambient noise, you will hear more information than you have ever heard when listening through the Sennheisers.

Headphones are no longer merely a tool for listening to music on the down-low. The HD 650s are an easy way to get huge sound for just a little bit of money. They are accurate, powerful and a necessary accessory for every series music listener. Sennheiser got it seriously right with their HD 650 headphones.
Manufacturer Sennheiser
Model HD 650 Reference Level Headphones
Reviewer Bryan Southard

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