Behind The Scenes (Feb. 1972)

by Bert Whyte

OUR FRIEND Joe Audiophile is in seventh heaven. His old Aunt Nelly remembered him in her will, and with the proceeds he has purchased his "ultimate" hi-fi system.

Nothing cheap about Joe ... he has the best of everything ... super megawatt amplifiers, pre-amps with a plethora of controls which can be corrective or creative, digital readout tuner, big professional four-channel tape deck (naturally Joe's system is quadraphonic) and last but not least, those ultra wide range speakers with low frequency response down in the sub-basement .. . the kind that can handle low C organ pedal notes with ease. To gild the lily, Joe not only has B-type Dolby units, but professional A-type Dolby equipment.

Main reason for this is that Joe has managed to wangle some 15 ips copies of some classical masters. In breathless anticipation, Joe has checked out his system to the last quarter-dB, threaded the 15 ips tape on his deck, and has prepared his ears for the state-of-the-art sonorities of his super system.

The first faint susurations of Ravel's "Daphnis and Chloe" are heard from the speakers ... molto pianissimo .. . and Joe is in a transport of delight, for those lovely opening passages are unsullied by tape hiss. The music expands and develops, the strings as smooth as silk, the woodwinds mellifluous, the brass bright and articulate, Joe is really flipping now. Such incredible realism! Just listen to that flute and WHUMP! RUMBLE! Rumble, rumble. What the hell is that! Joe jumps up and stops the tape, rewinds the tape a bit and hits the play button. In a moment, the same extraneous low frequency noises assault Joe's ears. What has happened? Poor Joe is the victim of the monitoring techniques practiced by many record companies, in their studios and on location. Now if our disillusioned friend Joe had obtained the disc recording of the tape he was playing, he would have found those particular low frequency noises he heard on the tape would not be audible on the disc. How come? Quite simple, really. When the disc was cut the frequency response below 60 Hz was rolled off quite rapidly.

Surely not, you say? Well friends, if I had a dime for every disc cut like this I would be sipping Dom Perignon on my yacht! What will really raise your eyebrows is that the engineers on this recording didn't really hear the low frequency noises on their monitor speakers and introduced the bass roll off as a precaution and a matter of expediency. (With less bass response a longer-playing and louder disc can be cut) I hasten to add that there are many fine discs with response to 30 Hz, as evidenced by the excellent reproduction of bass drums and organ pedals.

The use of bass roll-off (and, for that 11 KHz) is a matter of record company policy or the idiosyncrasies of chief engineers. In any case, this sonic emasculation is an all too common practice.

What are these low frequency noises that upset Joe? They can be caused by quite a variety of sources. Many halls in which classical recordings are made are afflicted with what is known as "room or hall rumble." These noises ranging from 60 Hz down to the subsonic level, are fairly low in amplitude, but can readily be picked up by the wide range condenser microphones generally in use in classical recording.

You can walk into an empty hall with the recording mikes in place and usually not hear anything. But activate the mikes and listen through headphones and you often hear all manner of thumps and rumbles. The noises can be caused by a peculiarity in the construction of the hall and its proximity to street traffic and subways. Years ago, when we recorded in Carnegie Hall, we did not start to record before midnight, and the New York subway people furnished us with a schedule of the trains, which at that time of night ran about every 27 minutes. Thus, with the subway literally underneath us, our recording was done in 27 minute segments! In many recordings of the Boston Symphony that RCA made in Symphony Hall, in certain quiet passages you can hear the sound of a bus rumbling up through its gears, as it pulls away from the hall. Naturally, the sound of the bus must coincide with a pianissimo section for it to be heard. A good example of this is in the first few minutes of the low level passages of the Erich Leinsdorf recording of Stravinsky's Firebird Suite. Contrary to the ideas held by many record buyers, RCA does not roll-off bass in its disc recordings, keeping response fairly flat to 30 Hz. Hence, no trouble in hearing the bus in those certain passages.

It is a fact that the monitor speakers, mostly of the so-called "theatre-type," used by many record companies and countless recording studios, have almost no bass response below 50 Hz. The engineers who use this type of speaker just can't hear the low frequency "garbage" being recorded on their tapes.

Why then do they use such speakers? For one thing, they are usually very rugged and reliable. And they can tolerate the high levels at which most monitoring is done these days. Of course, the over-riding consideration is that the disc is going to be rolled off anyway, so who cares? Alas, poor Joe cares ... naturally the 15 ips copy of the master didn't suffer the bass roll-off, so he was subjected to all the low frequency problems.

Most audiophile speakers have a better low frequency response than the above described monitors, and a fair percentage can do a good job of reproducing bass to a bit below 30 Hz. These speakers are equally available to recording companies as they are to audiophiles, and indeed, some of the more enlightened companies do use them for monitoring. I should modify that a bit by stating that this monitoring is usually for classical recordings in concert halls. When I recorded the London Symphony Orchestra and the London Philharmonic in Walthamstow, my favorite hall in England, I used huge wide range speakers with extended low frequency response furnished to me by the famous Gilbert Briggs of Wharfedale. The recording room (nominally the conductor's "Green Room"), physically separate from the hall, was draped with rolls of Fiberglas and burlap, to make the room quite "dead," as we were interested in the acoustics of the hall and not that of the hall plus the recording room. These speakers, driven by special commercial versions of 60 watt McIntosh amplifiers, gave us an excellent indication of low frequency as well as overall response.

The question naturally arises: If you are using monitor speakers with good low frequency response, which allows you to hear such things as hall rumble, what can you do about these unwanted sounds? The obvious answer is that if possible, you change the recording venue, to a location where the speakers do not reveal room rumble or other anomalies. Since this is not always practical, such things as sub-sonic filtering are a help (mainly to eliminate their audible harmonics) or narrow band notch filtering, especially if the low frequencies have a pronounced peak. With audiophile speakers improving constantly in their low frequency response, it would behoove the engineers of many companies to use monitor speakers responsive to the entire frequency spectrum. Taking the expedient way out, rolling off the low frequencies,' does not endear a record company to its quality-conscious customers. I can readily sympathize with our friend Joe, since I have many 15 ips copies of masters in my possession, not a few of which are diminished by unwanted low frequency junk. I expect as usual, I'll get the cry that I am talking about a minority situation, and the mass public doesn't care, does not have the discrimination, and does not have the equipment, so why bother about this problem. Just remember, it has been the cranky audiophile over the years who has resulted in the present high quality of music reproduction.

Let's not just look the other way, when this is something so easy to correct.

In reporting on the AES convention a few issues ago, and in mentioning the unique Neve console/Ampex recorder exhibit, I inadvertently left out the fact that the special recording made by John Woram of Vanguard, was a session using all Shure microphones, and paid for by Shure. My apologies for this omission.

(Audio magazine, Feb. 1972; Bert Whyte)

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