A 105th AES "P R E" VIEW
ã 1998 by Eddie Ciletti
As a reviewer, I rarely have the opportunity to compare more than two products at a time. Even at the AES convention — with so much gear under one roof and so little time — it will be quite difficult to make any real sonic comparisons. Lucky for me, an intimate opportunity presented itself well in advance of the show…
On the 24th and 25th of July, The Boston PRE Party was sponsored by
Mercenary
Audio. Throwing a bunch of gear into the harbor is not unfathomable
with Fletcher, a.k.a. "Mister Mercenary," at the helm. That said, a comparatively
sedate event was held at Boston’s Prophet Sound. Six designers presented
eight microphone preamps for evaluation to a mixed audience of recording
engineers, producers and artists plus two "representatives from the press."
(Models and prices are shown in Table One.)
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Mono |
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THE CHALLENGE
For anyone not knowing what to expect, the difference amongst microphone preamplifiers — when conservatively operated with plenty of headroom — can be rather subtle. The PRE Party was thankfully not a shoot out, sparing all of us the typical assortment of conflicting opinions. Some folks can make an awfully huge fuss over the slightest sonic differences just because they’re capable of such minute perceptions. The "sessions" recorded at Prophet Sound were compiled on to a CD that can be purchased online so that you can be the judge.
Some audio products are difficult to compare. In this particular instance, there is a major technical obstacle — you simply cannot feed the output of one microphone into eight preamps (at once) because the combined input impedance would be too low. Instead, acoustic guitarist Uncle Fester and female vocalist Anastasia gave repeat performances that were as consistent as is humanly possible. The perfect solution does not exist, but I think the point was not to find the "best preamp" or the "big difference" so much as to exercise one's ears in the art of listening.
We didn’t listen to the noise floor, nor were the preamps purposely driven toward their maximum output. There was no "entry level" model. Any of these tests would have added dimension to the "party." By contrast, three different mics were used for guitar and another three for vocals. Here, each microphone's sonic "signature" was more than obvious. Check out "The Microphone Detour" sidebar for details.
NORMALIZE
Prior to the "session," pink noise was pumped into a speaker so that the "gain" of all the preamps could be made equal (using the Coles 4038 microphone and a VU meter on the console). The preamp outputs were patched into dedicated channels of a Neotek console outfitted with Neve automation. The mix buss fed Apogee converters feeding a pair of Tascam DAT decks. Monitoring was via Genelec near-field monitors.
THE OBVIOUS DISTINCTIONS
After one microphone had been auditioned through each preamp, another mic would make the rounds, this time in reverse order. Starting with the Mill Creek, the first four units all used vacuum tubes. I listened to the preamps as well as the reactions of people in the control room. The Manley seemed slightly louder especially when it followed the Mill Creek. The only transformerless product in stack one was the Millennia Media M2-A. It had just a bit more "ear tickle" (high frequency detail) and extended bottom end. At the bottom of the first stack was the DW Fearn, the mono version of which I had reviewed several years ago.
Was the Manley preamp really louder or was it some kind of techno-harmonic-voodoo? I don’t have the exact answer, but it’s unlikely the Manley was being overdriven. It was more likely a "loading" issue. Some microphones can be very affected by a preamp’s input impedance.
STACK ‘EM
The second stack began with the transformerless Crane Song Flamingo. It was the only model that, in addition to "clean" mode, featured a pair of "character alteration" switches labeled FAT and IRON. For this reason, the Flamingo was tested twice. Remember that none of the eight preamps sounded radically different from each other, although a child of three could easily have picked out any of the microphones. The Coles ribbon mic (on guitar) was most obviously "darker" than the Shure SM-57 or the Neumann KM-84. The Crane song, in FAT mode, made the Coles bright enough to compete with the other mics.
The next two preamps were brother and sister pair from Great River. The MP-2 has both an input and an output transformer (the latter is optional), while the "XP-2" is a completely different transformerless design. (XP-2 is my designation for a unit that was still in the prototype stage.) At the bottom of the second stack was the Millennia Media HV-3.
Since all of the models in stack two were "solid-state" and only one had transformers, the sound was so similar that it became necessary to "tune" one’s ear to frequency bands that might reveal the differences in topology. All the transformerless units seemed to have ever so slightly more "air" or extended high frequency response compared to those with any "iron" in the path. Since this was not a blindfold test, one could argue that my brain misled my ears…
Both the guitar and the voice stimulated the region between 80Hz and 250 Hz. The Great River MP-2 seemed a "hair more woolly" in this region while the Crane Song Flamingo (in FAT mode) was even more pronounced. By contrast, the Millennia Media HV-3 and the Great River XP-2 might be described as "drier" or as having a "tighter" low-end. Buy the CD and let me know what you think, ok?
NAPKIN FEST
The best part of the Boston PRE Party was not captured on tape. It was the conversation amongst the assortment of designers in-between sessions, at dinner and at the bar afterwards. Napkins were soon covered with circuit ideas with nearly everyone exchanging war stories, listening tips and component preferences. None of this was as much about marketing as it was about a passion for audio. Each person’s pursuit was relatively unique while the general consensus was that "if it was being done with vacuum tubes, it had probably been done before!"
JUDGE AND JURY
An evaluation environment must be able to quickly and easily switch amongst various components. (Not all components will allow this. The CD compilation made it possible.) Tests, in this case acoustic, need to be created that help to reveal sonic discrepancies. For example, the CD included a nylon string guitar that seemed to reveal more subtleties than the steel string acoustic from the previous day’s testing. In short, whenever someone tells you that such-and-such box sounds better or worse than so-and-so box, be very suspect. Ask them how the comparison was made — more often than not the two pieces were not even in the same room!
AND THE WINNER IS…
You might wonder how I could walk away from such an evaluation without declaring a winner. That’s easy! These are all well-made products. That’s not a cop out! An entry-level preamp in the $250 to $750 range might sound nearly as good, right now. The BIG difference is that a quality product will still deliver its specs and great sound in ten years. Like the old cigarette advert sez, "it’s what’s up front that counts."
SIDEBAR: The Microphone Detour
On day one, a Coles 4038, a Neumann KM-84 and a Shure SM-57 were placed in front of an acoustic guitar. On day two, the Brauner VM-1 replaced the Neumann KM-84. On voice, a Shure SM-57, a Neumann U-48 and a Brauner VM-1 were used. Since most of us are familiar with the SM-57, it was enlightening to get reacquainted with this "dynamic" veteran. In a relatively "live" studio the SM-57 seemed to capture less room ambience when compared to the two condenser mics (both were set to the "cardioid" or unidirectional mode). Aside from the obvious difference between dynamic and condenser, the cardioid pattern itself can not be taken for granted.
If you take a closer look at the documentation that comes with any mic, notice that the pick-up pattern is not the same at all frequencies. This dramatically influences both the perceived quality of any mic as well as its "Proximity Effect," the increased low-frequency response when directional microphones are used "up close." That might explain why the SM-57 was particularly perturbed when presented with the pistol-power of a head-on popping "P." It was certainly more sensitive to a "P" than either condenser microphone.
The PRE Party reminded me that if an SM-57 was the only mic available, the more distance between it and a vocalist, the better.