LISTEN UP!

Although new models of headphones are introduced every year, there have not been any really significant advances in the technology of these devices recently that would constitute a performance "breakthrough." However, the inherent qualities of the digital CD--its absence of noise artifacts, low distortion, and cleanness of reproduction-have greatly encouraged headphone listening. Headphones are also beneficial to apartment dwellers who must keep sound level low, or to families who share the same space but listen to different things.

Headphone users have a very broad choice of models at various levels of cost and in quality of reproduction.

Those seeking better quality headphones can choose between many models using dynamic drivers and a few models that employ electrostatic drivers. Generally, the electrostatic models are more expensive than dynamic headphones, and there is a broad assumption that the very highest reproduction quality from headphones is available only from those employing the electrostatic principle.

Until now, it has been my experience that the top electrostatic headphones do provide a superior sound, with very fast transient attack, more air and transparency, less distortion, and wider frequency response than their dynamic counterparts. This better electrostatic sound imposes a logistics problem in that a power supply is necessary to provide a polarizing voltage to the electrostatic elements. Thus, unlike dynamic headphones, they cannot simply be plugged into a headphone jack on a receiver, preamp, cassette deck, or CD player.

Needless to say, if there were a headphone with dynamic drivers which could not merely equal but surpass the quality of reproduction available from the best electrostatic 'phones, this would be a real breakthrough product with many applications. To have 'phones of this quality able to simply plug into a jack would be invaluable.

I am pleased to report that rather than imagining some fantasy headphone of the future, a headphone with these desirable characteristics is now available in the form of the Joseph Grado Signature Products HP-1 headphones. Yes, he is the same Joe Grado who has been designing and manufacturing high-quality phono cartridges for many years. He still produces his unique moving-magnet phono pickups, sold worldwide. Like all manufactures of phono cartridges, Grado is aware of the declining market for them due to the encroachments of the Compact Disc. Thus, his diversification into headphone manufacturing is understandable. However, Grado certainly knew that there was no dearth of headphones on the market, so in keeping with his basic design philosophies, he knew that his headphones would have to possess unique qualities and cutting-edge performance to be competitive.

I've known Grado for almost 40 years. He is a remarkable person, and to call him a Renaissance man would be quite apt. In his early years as a highly skilled watchmaker, Grado worked with tiny, high-precision, delicate parts. This background was invaluable when he started to design and manufacture phono cartridges.

Grado takes a perfectionist approach to everything he gets involved with. He is strongly iconoclastic and seems to have an intuitive knack for stripping away things that are mere facade; he gets down to the basics.

His interests are far-ranging--he is a high-performance car enthusiast, has flown his own plane, and built violins.

Over the years he has become a materials expert. His love of audio is balanced by his love of music. Grado is a splendid tenor and has given recitals in Alice Tully Hall in New York City and has sung in such operas as Tosca with the Honolulu Opera Company.

Over the years, Grado and I have always agreed on one subject-the destructive effects of resonances on sound reproduction. In every component of an audio system, unsuppressed resonances wreak their havoc on the sonic integrity of the music signals. In the design of his HP-1 headphones, Grado has employed his knowledge of materials, along with special fabrication techniques, to make a headphone as free of resonances as possible.

The HP-1 headphones are very straightforward, clean in design, with a rather high-tech look to their circular, machined alloy drivers and sliding-pillar positioning devices. The headphones are made from a very hard aluminum alloy. A proprietary processing method increases the porosity of the alloy. This gives the alloy a more open structure, and further processing then fills in the structure with anti-resonant damping material. This treatment suppresses the ringing resonances of the earphone chambers which house the diaphragm, voice-coil, and the magnetic driving system.

The diaphragm, made of a low-mass plastic which has a high internal damping factor, is modified to selectively broaden the resonant frequencies. The diaphragm mass is selected with the compliance of the suspension in mind, so as to provide the desired low-frequency resonance.

Grado says: "The mass of the diaphragm is low enough to produce a full 20-kHz bandwidth, and yet it's stiff enough to produce high volume levels with no increase in distortion compared to low-level performance. I found this direction much better than going for a very light and very fast diaphragm action, which would give me a more extended top end; such a design carries the penalty of more diaphragm breakup and much more distortion at higher levels and at all frequencies, as with many electrostatic earphones. Theoretically a lighter diaphragm is supposed to be better, but in the real world this is rarely the case.

It is much more important to me to use a diaphragm that will reproduce superbly clean sound at any volume level at all frequencies rather than extend the high frequencies for no practical reason. It really is a trade-off: Do you want a little more speed with a sharp increase in distortion, or do you want low distortion with speed that is already much more than what is really needed for the fastest known music signal rise-times? Keep in mind that a light diaphragm will cause frizzy highs, distorted midrange, and-worst of all-deficient, tubby, or muddy bass." The outer perimeter of the diaphragm is bonded to the earphone chassis and is suspended by its own elastomeric stiffness. The adhesive used in the bonding is inert, which helps to subdue diaphragm rim resonances. The diameter of the voice-coil is calculated to ensure that the full area of the diaphragm is driven with as pure a piston action as possible and to minimize diaphragm breakup modes.

The voice-coil is made of a special ultra high-purity copper wire that is drawn through the die very slowly and in extremely small increments, and it is annealed following each of these drawing operations.

The magnetic drive system of the HP-1 headphones utilizes a neodymium structure of very high power, for maximum efficiency and to control the diaphragm excursions at high volume.

In his zeal to suppress resonant colorations, Grado even researched various materials for the headband padding, and a combination of plastics and insulation provides high damping for the spring steel headband.

Grado contends that no single accepted measurement device can provide accurate data on headphone performance. He cites his experience in manufacturing his phono cartridges, in which 10 different stereo test records will provide 10 different curves. So Grado uses the Brüel & Kjaer headphone analysis system as well as several other devices, correlates the data from all of them, and uses this information in making various adjustments and modifications to the headphones.

Grado states that the HP-1 headphones are flat through the full audio frequency spectrum. More importantly, he feels that the relentless suppression of resonance, in every possible way in every element of the headphones, has dramatically reduced distortion, even at relatively high volume levels.

The HP-1 headphones can be efficiently driven from the 'phone jacks of most preamps, CD players, cassette decks, etc. However, for those who want to take fullest advantage of the low distortion characteristics of the HP 1 'phones, Grado has introduced a companion headphone amplifier. The unit is 2 1/2 in. H x 6 in. W x 7 in. D and weighs a little over 2 pounds. To avoid any a.c. line hash or other problems, the amplifier is powered by batteries. A compartment within the unit houses four standard 9-volt batteries; two of them will power the amplifier for 50 hours, and the other two are spares.

The amplifier has stereo RCA line in and out jacks, an on/off toggle switch for battery power, a 1/4-inch jack for headphones, and a precision volume control which is said to track from 0 to 70 dB within 0.5 dB. The amplifier circuit operates in a special, advanced Class-A mode. The unit can also serve as a line stage to feed a power amp, depending on the setting of an output switch. The Grado headphone amplifier costs $650. The HP-1 headphones, which are equipped with toggle-type polarity reversal switches mounted on each earphone structure, are $595. The HP-2, without polarity switches, is $495.

Apparently, these extraordinary headphones have generated great interest in the audio engineering fraternity. I was impressed to learn that such sonic nit-pickers as mastering engineer Bob Ludwig of Masterdisk uses them in his evaluations, as does Tom Jung of dmp and Dick Sequerra of FM tuner fame. The Grado HP-1 headphones are also being used by audio amplifier manufacturers as a sort of auditory measuring tool to evaluate circuit changes.

I compared the HP-1 to what is generally regarded as the best electrostatic headphone-the Stax Lambda Pro, which has been my reference unit for quite a few years. I was able to compare not only the sound qualities of the headphone, but the sound of the HP-1 driven from the output of a Sony CDPX77ES versus its sound via the Grado amplifier.

One of the great advantages of the electrostatic headphones had been their superior bass response. To compare the HP-1 in this parameter, I used the superb Dorian CD of the organ works of César Franck (DOR 90135). The great organ of St. Eustache in Paris has awesome 32-foot pedals, and the third track, "Fantaisie in A," opens with a tremendous outpouring from them at their 16-Hz fundamental. Listening first through the Grado HP-1 and then the electrostatic 'phones, it was immediately apparent that the Grado had more bass extension and resolution, as well as significantly less distortion. The middle- and upper-frequency reeds and brass were noticeably cleaner, and there was heightened ambience presentation. My keen-eared wife, Ruth, verified my findings. We went on to the Telarc CD (80255) of Michael Murray playing the magnificent Willis organ in Salisbury Cathedral in England. The second track, "Fanfare" by John Cook, shows off this organ's absolutely incredible choral reeds. The brilliance and projection of these reeds in the vast acoustic space of this cathedral is breathtaking.

We ran the gamut of CD music, from solo piano to massive symphonic and choral works. In every case, the cleanness, low distortion, and openness of Grado's HP-1 'phones were a revelation. Voices were beguilingly smooth, and choruses were beautifully articulate. In Tom Jung's dmp recordings, all of his exciting percussion and subterranean bass synthesizers were heard with absolute transient accuracy and speed.

The Grado HP-1 headphones are clearly the best I have ever heard, and for a reviewer, they are invaluable for close, detailed analysis of recordings prior to loudspeaker evaluation.

(adapted from Audio magazine, Mar. 1991; Bert Whyte)

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