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Can We Use Headphones As Critical Monitors - Part 2 of 2
A look at some popular models...
By Robert Auld

In Part 1 we made the case for using headphones as critical monitors for recordings and suggested some ways of evaluating particular headphones for such a role. Here are my own evaluations of several headphones, using the criteria outlined in Part 1

[Editor's note: this article was current in the year 2000, but most of the headphones mentioned here are still current models as of 2009, so we elected to keep this set of evaluations online for your reference.]

This article began as a review of a single pair of headphones, the Alessandro Music Series One by Grado Labs. When it became apparent that we were going to deal with the whole question of headphone monitoring, it seemed appropriate to evaluate a few other headphones as well.

The Sony MDR 7506 is useful as a benchmark for comparison, as most everyone is familiar with them. What has Sony come up with for their new MDR 7509?

Even though it has been around for a few years, I included the Sennheiser HD 580 because it has become a de facto standard for a number of engineers and producers of classical music recordings. I also wanted to take a look at the Sennheiser HD 250 Linear II (even though Mike Metlay and Lorenz Rychner had already evaluated it in the 5/99 issue) to compare how Sennheiser handled the challenge of a closed earcup design.

Sony MDR 7506

First, some history. The Sony 7506 began life as a consumer product, the MDR V6, back in the late 1980s. It attracted the attention of professional engineers because it had several characteristics much needed for location monitoring headphones: good isolation; a lightweight, well-configured design that could be worn for hours without undue discomfort; and high sensitivity, making the V6 suitable for use with battery-powered portable equipment not capable of high output levels.

It sounded good too, with smooth overall response and really impressive bass extension. And it proved to be durable without the chronic cord failure problems found in some previously popular monitoring headphones. The nifty fold-up earcups and built-in miniplug-to-phone plug adaptor were just icing on the cake.

Sony noticed the professional interest in their consumer headphones, and in the mid-1990s introduced the MDR 7506 as part of the Sony Professional line. It differed from the MDR V6 in one respect: Sony rebalanced the transducers to have somewhat flatter overall response. The V6 had a frequency response curve that gradually sloped downward with increasing frequency. While esthetically pleasing, this response characteristic was not ideal for professional monitoring.

The current status of the MDR 7506 is best described as ‘ubiquitous.’ It has become the headphone equivalent to the Yamaha NS-10 for loudspeakers, or the Shure SM57 for microphones: everybody uses them, not because they are “the best” but because they are proven to have characteristics that experienced users find useful in common engineering situations.

Comparing the MDR 7506 to the other headphones I auditioned for this article put its strengths and weaknesses in high relief. First, they are not truly “accurate” monitors to my way of thinking. The treble rolls off in the top octave or so, which results in a loss of top end detail in the mix. There is a mild, broad peak in the midrange, which adds definition to voices and solo instruments. And the deep bass is somewhat larger than life, though fabulously extended. Indeed, these headphones have useful response down to 16 Hz or so, and that response is notably clean.

The stereo imaging of the 7506s is about as good as I have heard from closed earcup headphones. They don’t render a sense of the performing environment as well as the best open-back phones, but they come pretty close.

I’ve used the 7506s for location mixing chores for several years and have learned to adapt to their characteristics. If the deep bass is a bit larger than life, if soloists are just a bit forward in the mix, and if the top end lacks some detail, I’ve probably nailed it. The hardest part is getting used to the top-end roll-off—it’s easy to make things a little too bright to compensate.

The practical amenities of the 7506’s design are why they are so popular with location engineers: the isolation, the compact folding design, the high sensitivity, the durable coiled cord. These headphones have a high enough quality sound to let you do good basic mixes on them.

Fine tonal adjustments in post-production are another matter; when compared to the Sennheiser HD 580s, the 7506’s tonal colorations are immediately apparent. I have hear d recordings that sound better on 7506s than on the HD 580s, but they are generally not recordings that I admire for their sound. Rather, I suspect they were mastered using monitors that had similar colorations.

Conclusion: The Sony MDR 7506 is still a very useful professional headphone at a reasonable price. I will continue to use my pair on location, especially for situations where portability is important.

Price: $170

More from: Sony Electronics Inc., 1 Sony Drive, Park Ridge, NJ 07656. 800/892-SONY, fax 201/358-4907,

Sony MDR 7509

The MDR 7509 is a new model, advertised as having “50mm drivers for deep bass.” Their design is similar in concept to the older 7506-closed back headphones with a coiled cord and earcups that fold up into the headband—but the 7509 is bigger and heavier than the 7506.

The larger ear cushions on the new headphones improve isolation from exterior sound (the 7506 is good but not great in that department) and are quite comfortable to my ears. This good ergonomic design should help reduce any discomfort caused by the greater weight of the new model. If previous Sony designs are any indication, the 7509 should be very durable. The sensitivity of the 7509 is about the same as the 7506—they can both be driven to loud levels with very little power.

If it were up to me, I would try and correct the technical faults of the 7506 in the new model, thus producing headphones with greater accuracy of response. Sony, however, seems to have designed the 7509 for people who don’t like how the 7506 sounds, period. So where the 7506 has relatively flat overall response with a midrange peak (a bit “in-your-face” as headphones go), the 7509 has a bass-heavy balance and actually dips down in the midrange—the epitome of “laid back.” The treble response is quite extended, but as it is reproduced at a lower level than the bass, high end details are not prominent in the mix.

I can imagine bass players really liking these headphones for tracking in the studio, and people who habitually turn up the bass control on their stereo will like them too. For critical monitoring we need accuracy, though, and these headphones just do not provide that. For that kind of use the less expensive 7506 remains superior.

But the sound of the 7509 is certainly not bad in an aesthetic sense; the overall response is smooth and sounds pleasant on many recordings.

Conclusion: It is not every day that new closed-back headphone models are introduced, but Sony’s design team seems to have had objectives for the 7509 more suitable for a consumer product than for a monitoring tool.

[Sony states that Robert’s assessment is basically correct; the 7509s were designed for drummers, bassists, and other artists who like heavy bass in their ’phones and desire a more robust design that can handle the extra bass and power. The 7509 also lacks the 7506’s exposed driver wiring to help prevent damage.—MM]

Price: $250

More from: Sony Electronics Inc. (see above)

Alessandro Music Series One by Grado Labs

Alessandro has been known as a producer of exotic guitar amps, among other things. They recently became the distributors for the Grado line of headphones, which are still made by Grado Labs in New York. The Music Series includes models One, Two, and Pro.

The three models appear similar in basic construction, the main difference being the materials used. The One uses mostly plastic earpiece parts, the Two uses machined metal, and the Pro is carved from wood! Besides the exotic materials, the more expensive models also have more closely matched drivers and may have slight variations in driver tuning.

The Music Series One tested here is the lowest priced of the three Music Series models. It appears to be the same basic design that Grado has used in previous models, such as the SR60: a simple steel headband covered in leatherette, and semi-open-back earpieces with foam pads that rest on the ears, the earpieces suspended on elegantly simple swiveling yokes.

The headphone cord is thick, straight and about six feet long, at which point it branches into a “y” about a foot long, with each leg of the “y” going directly to an earpiece. The cord comes with a gold-plated 1/4" plug; if you want to use these phones with a portable CD player, you’ll have to buy a mini-jack adaptor from Radio Shack.

These headphones are not suitable for applications where you need isolation, as they offer essentially none. However, in common with other lightweight on-ear designs, they are very comfortable to wear.

The only ergonomic criticism I can offer is that the cord is a bit on the short side; I can see some situations where you could end up yanking the headphones off your head when unexpectedly coming to the end of the cord. This is fixable by purchasing an extension headphone cord (time for another trip to Radio Shack...).

The Music Ones are fairly sensitive (a bit less so than the Sony 7506s) and should offer adequate volume from most headphone amps. And they sound good. I would characterize the sound as bright, a bit forward, with tight bass and surprising bass extension with musical signals that have true deep bass information. Listening to test tones, I heard usable response down to 20 Hz. This would be good for any headphones, but is exceptional for a semi-open ear design.

Edward M. Long, whose writing you have seen in Recording, tested the Grado SR125 headphones for a consumer hi-fi magazine back in 1995. The SR125s in the review photo appear very similar in construction to the Music Ones. Long measured the phones in his lab and found they were very flat up to 2 kHz, where the output rose to about +3 dB at 3 kHz, reaching a maximum of +5 dB at 5 kHz. The output remained at this level up to 10 kHz, where it rolled gently down (5 dB) to t he reference level at 20 kHz.

He could have been talking about my sample of the Music Ones. Apparently the resemblance is more than skin deep.

The stereo imaging of the Music One is good, but not great. They are, perhaps, a shade more “open” sounding than the Sony 7506, but do not achieve the remarkable sense of stereo space that one can find in a few other open-ear type headphones.

One idiosyncracy: if you cover the earpiece grilles with your hands, the bass response of the phones deteriorates drastically—suddenly they sound like a pair of cheap table radios. Obviously, the air resonance of the chamber behind the diaphragm is a crucial part of the earpiece design. This is of no consequence for practical use unless you insist on placing your hands over your headphones when listening.

A final note on the sound: over time I tended to find the brightness of the overall balance fatiguing. While my head enjoyed the physical comfort of these headphones, my ears were a little less happy. As this is a subjective reaction, you may not feel the same way, so I encourage you to listen for yourself.

The Music Ones can be purchased for less than list price from Alessandro’s web site.

Conclusion: The Alessandro Music Series One will hold no surprises for anyone familiar with previous Grado headphones. They are comfortable, good sounding headphones and a very good value. Their lack of isolation disqualifies them from location recording use.

Price: $99

More from: Grado Labs/Alessandro High-End Products, voice/fax 215/355-6424,

Sennheiser HD 580

The Sennheiser HD 580 was introduced a few years ago. It is an open-back design with essentially no isolation. Unlike other open-back headphones, the 580s are rather large and have earpads covered with velvet-like material that surround the ears without touching them. They are also fairly light for their size; combined with the earpad design, this make them quite comfortable to wear.

As the HD 580 is diffuse field equalized (like the HD 250), the interesting question was whether the two would sound similar. And how did Sennheiser cope with the different design problems of open-back vs. closed-back earcups?

The headphones come with a three meter straight cord that divides into a y-connection about nine inches from the headphones. The ends of the cord plug into each earcup with color-coded connectors of proprietary design. An advantage to this arrangement is that the entire cord assembly is easily replaced in the field.

The cord terminates in a gold-plated mini-plug, and a supplied 1/4" phone plug adapter fits over it. I found that the long, thin cord took some getting used to; until I learned how to handle it I tended to step on the cord, on occasion actually yanking the phones off my head. Fortunately, they took the abuse in stride.

These headphones need a bit more power than the Sony MDR 7506. Most headphone amps, built-in or otherwise, should have no problem driving these headphones to fairly loud levels.

According to Sennheiser, the HD 580s are diffuse field equalized and have a frequency response of 16 to 30,000 Hz (-3 dB) as measured with the B&K type 4153 coupler (a test device illustrated in our last installment). This is a pretty impressive specification, and probably accurate as far as it goes. I add the qualification because the B&K type 4153 is not a human ear, and what this human heard over his ears does not correspond to the spec in all respects.

I tested the HD 580’s bass response by listening to warble tones centered on 1/3 octaves down to 16 Hz (the limit of the test CD I was using). This kind of listening test is necessarily imprecise, but it can give an indication of how far down a transducer can actually produce useful response.

My judgement, based on this test and various music recordings, is that the HD 580s are quite flat to about 45 Hz, at which point the response begins to roll off. Useable response extends to perhaps 30 Hz, after which it drops off like the proverbial stone.

Now, this is certainly respectable bass performance for a high quality monitor, and even impressive when the difficulty of maintaining bass response in open-back headphone designs is considered. (Closed-ear designs can use the sealed air volume they contain to great advantage.) It just doesn’t match Sennheiser’s specification. So if you record pipe organs for a living, you may want to supplement the 580s with a good pair of closed-ear phones.

Sennheiser describes the HD 580 as “an ideal choice for the professional recording engineer recording classical music.” I took them at their word and auditioned the HD 580 with high quality classical music recordings.

The bigger and more demanding the ensemble that was recorded, the better these headphones sounded. I finally threw caution to the winds and listened to Jack Renner’s recording of Mahler’s Symphony No. 8 (Atlanta Symphony Orchestra & Chorus, Robert Shaw conducting—Telarc CD-80267). Imagine a huge chorus of hundreds of singers, full symphony orchestra augmented with extra brass, organ, eight operatic soloists—there’s a reason why this work is called the “symphony of a thousand.”

Over the HD 580s this recording opened up in a way I had not heard before from headphones. Most loudspeakers should do so well. Reproduction of more normally-scaled recordings was equally impressive: the sense of acoustic space was exceptional, reverb tails were detailed, tonal balance was natural, etc.

The stereo imaging of the HD 580 is superior to that of the other headphones tested, or to any other headphones I can remember hearing. The image is very wide and is seamless from left to right. It still sounds like you are listening to headphones (there is no getting around the lack of interaural crosstalk, after all), but the sense of the acoustic space present in the recording is greater than usual.

While I am reluctant to attribute this to any one factor of Sennheiser’s design, the placement of the transducers relative to the ears may be a strong contributor. With most headphones, the drivers are right on the ears (or even in them). With the HD 580, the drivers are located about a half inch away from the ears, suspended in the space between the open-back grill and the ear pinnae. This probably allows a reduction of the standing wave effects that can be set up by a headphone driver interacting with the ear cavity.

Conclusion: The Sennheiser HD 580s are remarkable headphones, offering a quality of reproduction that used to be associated only with very expensive electrostatic models. Their merely mortal bass extension is the only criticism I can make of them. They are, of course, not suitable for use in situations where isolating headphones are needed, and they will cost you quite a bit more than what you would pay for the Sony 7506 or nearly triple what you’d probably pay for the Grado Music Ones. For this kind of sound quality, that is still a bargain.

Price: $269.95

More from: Sennheiser Electronic Corporation, One Enterprise Drive, Old Lyme, CT 06371. 860/434-9190, fax 860/434-1759,

Sennheiser HD 250 Linear II

The HD 250 Linear II is a closed-back headphone, and is an older design than the HD 580. It was among the first of Sennheiser’s models to be “diffuse field equalized.” It uses a cord design like the HD 580’s and has similar sensitivity—refer to the previous review for details.

Like many good closed-earcup headphones, the Sennheiser HD 250 has very strong bass response, extending down to about 20 Hz. My only complaint is that the bass is a bit too strong, particularly in the area of 100 to 200 Hz.

At the treble end the HD 250 is very smooth, very extended, and—compared to the HD 580, which is beautifully balanced—a bit hyped. And the midrange has a mild dip, which tends to make solo instruments and vocalists a bit less forward compared to the HD 580 and also de-emphasizes room ambience.

On much program material the HD 250 sounds very beguiling indeed, but it is not a genuinely accurate headphone. I am not sure whether Sennheiser was deliberately trying to produce a “character” headphone, or if they simply hadn’t figured out diffuse field equalization yet. In any case, the result is quite different from the later HD 580.

I had a chance to compare the Sennheiser HD 250 with the Sony MDR 7506 while making a live recording of the Columbia University Orchestra. It was a good situation for judging the accuracy of the respective headphones—I could listen at the position of my Crown SASS stereo microphone, then walk over to my equipment setup and listen on the headphones—instant ‘live versus recorded’.

The Sony headphones had a more accurate overall balance and reproduced room ambience better. However, the HD 250s revealed more detail in the orchestral mix because their isolation was superior. And the slightly hyped top and bottom response of the Sennheisers actually seemed to help me separate the headphone sound from the live sound that leaked in via bone conduction, etc. I ended up switching between the two headphones, depending on what aspect of the orchestral mix I wanted to concentrate on.

Conclusion: The Sennheiser HD 250 Linear IIs are potentially very useful location recording headphones. I have yet to try a closed-back design with better isolation, and they are sensitive enough to be driven by typical battery operated equipment. I have some reservations about how they depart from accurate response, but suspect it is possible to learn to adapt to their sound.

Price: $250

More from: Sennheiser Electronic Corporation (see above).

Robert Auld is an audio engineer and theatre sound designer who works in New York City. Write to him via


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