THE B.A.S. SPEAKER

Subscriptions & Membership Information EDITOR-IN-CHIEF: Brad Meyer STAFF: Robert Borden, Alvin Foster, John Schlafer, Jack Stevens PUBLISHER: Peter W. Mitchell, President, BAS VOLUME 8, NUMBER 7 APRIL 1980 THE BOSTON AUDIO SOCIETY P.O. BOX 7 BOSTON, MASSACHUSETTS 02215
THE BOSTON AUDIO SOCIETY DOES NOT ENDORSE OR CRITICIZE PRODUCTS, DEALERS, OR SERVICES. OPINIONS EXPRESSED HEREIN REFLECT THE VIEWS OF THEIR AUTHORS AND ARE FOR THE INFORMATION OF THE MEMBERS. REPRODUCTION OF ANY PORTION OF THIS NEWSLETTER FOR ANY PURPOSE WHATSOEVER WITHOUT WRITTEN PERMISSION OF THE PUBLISHER IS STRICTLY PROHIBITED.
In This Issue The latest issue of the new, lo-cal Speaker contains an interesting variety of ingredients. The feature articles cover the two ends of the audio chain. The first is a piece, reprinted from Recording engineer/producer, by audio consultant F. Alton Everest on comb filtering in microphones and rooms. It should offer valuable insight into a little-known effect for all you devoted recordists, and may help explain why some multi-miked productions sound so bad. The second is a thorough analysis of speaker cables, both garden-variety and exotic, which further strengthens the case for thick wire of ordinary construction. New contributors Charles Ward, James Thompson, and Mallory Harling are to be commended for a solid piece of work. Local member Mark Fishman has an interesting tale to tell about the time he tried to find out where Dolby level really is on a cassette; the answer turns out to be a little more complicated than you might think. An elegant summary of recent issues of Hi-Fi Choice comes from Jack Reed. We'll be hearing from Jack on more technical matters in upcoming issues. The summary of the March BAS meeting, at which Gotham Audio's Stephen Temmer held forth on digital recording and other topics, will hold the interest of those who remember his role in the digital standards controversy of a year ago. Temmer' has seen and heard just about every digital audio and video storage system now extant, and is able to put these experiences into the context of his thirty-odd years in the business. Call Up Your Friends By the time you read this, the annual BAS telephone list will be available. Send a SASE to Frank Farlow at Box 7 for your copy.
The B.A.S. Speaker (ISSN 0195-0908) is published monthly by The Boston Audio Society, Trapelo Road, Lincoln, MA 01773. Subscriptions are
available to members of the Society. Membership dues are $12 per year , October 1 through September 30 ($25 U.S. currency overseas, including air mail). $11.45 of the dues are a subscription to The B.A.S. Speaker including all issues of the applicable membership year. For further information and application form, write to The Boston Audio Society, P.O. Box 7, Kenmore Square Station, Boston, MA 02215. Second-class postage paid at Boston, MA. POSTMASTER: Send address changes to: The B.A.S. Speaker, P.O. Box 7, Boston, MA 02215.
Copyright 1980 The Boston Audio Society Vol. 8, Num. 7 April, 1980 OCRed from printed copy - errors possible.

The BAS Speaker

For Sale
Verion/Cotter MK-1 step-up transformer for moving coil cartridges, "P" strapping for low-
RTR ESR-15 electrostatic tweeters with built-in crossover at 1,200 Hz, $500/pair; special
i mpedance/low-output cartridges (e.g., Supex, Fidelity Research, Ortofon, Koetsu, Signet), mint, $275. R. Luppen, 10309 Seabury Lane, Los Angeles, CA 90024 or call (213) 581-8121 days, (213) 474-8138 evenings. 1 : 1 dubs of audiophile master tapes made by Monmouth Recording Co., cassette or reel-to-reel, dbx II or Dolby. Send SASE for details to Ronald Freeman, 43 Stratford Dr., Freehold, NJ 07728 or call (201) 462-5855 after 7 p.m. EDT. Quad ESL, old (#5546) but in first-class condition both sonically and visually, $275. Francis Daniel, 201 West 89th St., New York, NY 10024 or call (212) 874-0590. ADS Model 10 Acoustic Dimension Synthesizer, includes power amp and speakers, $695; SWTP Tigersaurus Amp, 200 watts mono, and 198 preamp, kits partially built but never finished, both for $75; Dynavector DV505 arm, $225; Shure V15-III with both spherical and elliptical styli, used only a few hours, $35; Shure V15-IV with spherical (3 hours) and elliptical (10 hours) styli, $75. Doug Robinson, 104 Lincoln, Waterloo, NB 68069 or call (402) 779-2589. Crown D-150A Amp and IC-150 preamp, both for $550; Onkyo TX4055 tuner, $125; Sherwood SEL-300 tuner with digital display, $250; Advent 201 cassette deck, just reconditioned at factory, $200; SWTP Armadillo amp, $100; stereo electronic crossover, 2 or 3-way, 900 Hz and 6,000 Hz, 24 dB/octave, $100. Michael Marks, (617) 732-4855 days, (617) 469-0710 evenings. Recording equipment: 3 Sony ECM-2'2P and 1 Sony C-55 FET condenser microphones, custom mixer (6 in, 2 or 4 out, ghosted center channel or panning, very low noise, VU meters, Beyer transformers), assorted bronze braided cables, 3 floor stands (9 ft), 4 desk stands, carrying case, all for $450. Magazines: Journal of the Audio Eng. Soc. 1961-1979 complete except 3 issues, Audio Amateur 1973-1979 complete, BAS Speaker Vols. 3, 5, 6, 7 complete, Audio magazine 1973-1979 partial (70 issues), all for $75. Ron Roscoe, 62 Harris St., Acton, MA 01720 or call (617) 263-8296 evenings, (617) 493-6084 days. Van Alstine Double Dyna 400 with external power supply box, excellent condition, $700; Dynaco CAB-2D vented cabinet, excellent condition, $15; Infinity Black Widow tone arm, GF arm tube and fluid damper with new container of damping fluid, good condition, $160; Russound tape switching unit with directions, unused, mint, $20. Chuck, (215) 623-0752 evenings, Fridays, or weekends. Dyna PAT-5 with Jung (and other) mods, $150; GAS Sleeping Beauty Shibata, $75; SME III tonearm with spare carrier, $150; Blaupunkt Frankfurt AM/FM stereo auto radio, $100; Jensen 4-in. coax auto speakers, $20 the pair; PS Audio PS-III phono section, accepts MM or MC cartridge, $125; Quatre DLH-100 power amp (not the one that blows up), separate supplies and other mods, 100 watts/channel, $175. All equipment functionally and cosmetically excellent. Julian Vrieslander, 364 Trumbull Corners Rd., Newfield, NY 14867 or call (607) 256-3838 weekdays. Selling my "mint" audio system due to home computer upgrading expenses: Infinity 4.5 RS speakers, new 2/80, $2,800; Symmetry ACS-2 crossover, new 4/80, make offer; Audio Research D-52B amps, 6/79 and 2/80, $775 each; Audio Research SP-6B preamp, modified 4/80, $950; Powerlite MC-3 head amp, rare, $250; Koetsu MC1 moving coil cartridge, new 2/80, $500; Linn Ittok LVII arm, 2/80, $475; Linn LP-12 turntable, 9/78, $625; Yamaha T1 tuner, 4/80, $275; Nakamichi 700 cassette deck, 2/77, good condition, $475; Stax SR5 headphones with STD7 transformer, 2/77, excellent condition, $110. Will consider trades plus cash, but only serious inquiries, please. Gerry, (408) 738-3310 evenings (PDT). design, limited production 435 watts (rms) mono tube amplifier, only the very best parts used, $500. Terry Eckert, New York, (212) 226-0199.

Hi-Fi Choice(s), 1980

Those familiar with the British Hi-Fi Choice series of equipment reviews, which are revised at intervals of 1 to 2 years, may be interested to know the planned publication dates for new editions this year, which I recently received from the publisher in response to my inquiry: "Cassette Decks and Tapes" "Turntables and Tonearms" "Receivers" "Cartridges and Headphones" Available April 7 August October
Evidently, the old editions of "Tuners" and "Amplifiers" are to continue mostly unrevised for a while. The new volume on "Stereo Systems" covering "over thirty" of these ready-mounted component systems which appeared last year and "Loudspeakers 3" continue also, of course. Those unfamiliar with the series may be interested in some description and summary. I have only the "Turntables and Tonearms 2" and "Cartridges and Headphones" volumes ( Hi-Fi Choice, Nos. 12 and 13, respectively), both copyright 1978 and both written by Martin Colloms. Some other volumes are written by Angus MacKenzie. The guides are about 210 digest-size pages long including some advertising, and they include indexes, five-to-fifteen-page introductions describing what the component does and how it should be used as well as how the measurements and listening tests were carried out, recommendations, and comparison tables. Each review includes a photo of the component taken for Hi-Fi Choice, an article of about 340 words discussing compatibility with other components, test results, listening quality, a table of "General Data" mostly giving about thirty measurement results, and a couple of pen recorder or oscilloscope photo representations of further tests. In the case of cartridges, some points covered include body mass, estimated compliance, low-frequency resonance in the SME 3009111 arm (undamped), sensitivity, load recommendations (not necessarily the manufacturers'), recommended arm mass and damping, hum sensitivity, high-frequency resonance, tracking ability at 300 Hz and 10 kHz. Frequency response and crosstalk to 40 kHz are graphed and 1-kHz square-wave response oscillograms are also included. Subjective sound quality is rated on a seven-value scale from "adequate" to "excellent" based on "blind" auditions which include disc versus master tape comparisons. The five-member jury listens over KEF R105's in a room with a reverberation time of 0.3 second, give or take 20% over the frequency range. In a field of 81 cartridges from thirty manufacturers, ten finished in the "excellent" soundquality category characterized by "open, neutral, deep, precise imaging." The list includes: ADC XLM III, but vague stylus profile, mild veiling, some edge added to complex passages; Audio Technica Signet Mk. IIIE-less apparent distortion than usual for a moving coil, a trifle bright with touch of surface noise, +2 dB above 8 kHz; B&O MMC 20CL-distant; Entre 1 -required 2.5 grams for 300 Hz at +18 dB, hardening of sound and high-frequency grit on complex passages; JVC X-2-slight shift toward hardness and brightness on louder, complex passages; Mission 773 -required 2.5 grams for 300 Hz at +18 dB, disc noise slightly emphasized with trace of grit, fizz and sibilance exaggeration, some poor tracking on heavy bass transients;

This sampling should give a fair indication of the breadth and depth of the series and may even enable you to compare it with your own experience. Except for the two old editions, which cost 1.50 each, the price is 2.00, plus 50p each for postage, payable by bank draft in English pounds. The books may be ordered from the publisher, Sportscene Publishers Ltd., 14 Rathbone Place, London W1P 1DE, England. Mine took a month to arrive. Jack Reed (Illinois)
OR BAS members may also obtain recent issues in the Hi-Fi Choice series from John Tooley, RFD 2, Box 120E, Milton, DE 19968. John's rate on the issues he has in stock is $6 U.S. for book rate mailings and $7 First Class. At present he has a few copies of "Stereo Systems," "Cassette Decks and Tapes 4," "Cartridges and Headphones," and "Loudspeakers 3." What John doesn't have, he will endeavor to obtain and spare you the hassle of currency conversion. Local members may obtain the last two titles directly from Peter Mitchell at local meetings while the stock lasts and save postage altogether. - Henry Belot

In the Literature

Audio, April 1980
Tape Guide (p. 6): Demagnetizing may not be needed. Audio ETC (p. 8): On some 48-year old stereo recordings. Behind the Scenes (p. 18): On some of the most advanced new products. Trends for the Future (p. 28): Surveying new products at the Winter CES. Double Barreled Amplifier (p. 36): Marshall Leach analyzes his design for a 250 W/ch kit with signal-tracking supply voltages and ostensibly superb performance. Digital Techniques in Sound Reproduction (p. 54): An intro to the uses of binary coding. Equipment Profiles (p. 62): Lirpa 5-Kg tonearm/cartridge (the annual April-Fool's parody). Fisher 4029 cassette deck (works OK at 1-7/8 ips, very good at 3-3/4 ips, but play EQ rolled off). Alpine 7307 car stereo receiver/cassette unit and 3002 power amp (tuner mediumsensitive, system otherwise excellent with honest and conservative ratings). Luxman K-12 cassette deck (an expensive two-head design, superbly well constructed, unusual control designs, counter actually displays tape timings, performance generally fine). Technics CO1 mini FM-AM tuner (mediocre sensitivity and subcarrier filtering, performance otherwise excellent). Audio Amateur, 1980 No. 2
The Grounded Ear (p. 2): On some of the more interesting new goodies seen at Winter CES. Power Supply Regulator for Op Amp Circuits (p. 8): Reasonably simple, yields very low supply
Timerless Tone-Burst Generator (p. 14): CMOS logic yields flexible operation. Audio Windows (p. 19): A clear discussion of designing and making infrasonic, ultrasonic, and Intensity Stereo (p. 29): Stan Lipshitz argues that Blumlein miking is the "only theoretically Audio Aids (p. 34): Phono capacitance switching, de-humming turntables, etc. Test Report (p. 38): Hafler DH-200 power amp (measures very clean, 250 W at 4 ohms, up to

impedance, important for the cleanest sound.
audio bandpass filters with selectable cutoff frequencies. legitimate stereophonic recording system."
13 amperes of output current, very fast; Jung hears a slight HF sizzle using Magnepans with Fulton wires but not with conventional speakers and wires; sound is judged "powerful, detailed, dynamic, and musical"). SouthWest Technical Products 210A Tigersaurus power amp (hum, buzz, parasitic oscillation, two tested samples unlike each other). Circuit Schematics (p. 48): Audio Research SP-6A preamp, Dyna FM-5 tuner front end. Letters (p. 50): Improving the Advent MPR-1, et al. The Audio Critic, Vol. 2 No. 2 FET-5 Mk 5 preamp mod.
Letters (p. 2): Including a hilarious diatribe from Frank Van Alstine describing the flaws of his Seminar, Part 2 (p. 9): A long-winded conversation about ultrasonic filtering, rise times, Wires and Cables (p. 23): A common-sense debunking job, with notes on some circumstances Speaker Reviews (p. 28): Axiom TLT-1 (edgy upper-midrange because of wrong crossover
hypothetical time-modulation distortion in preamps, preamp bypass testing, etc. where low-inductance or RFI-shielded wire can make a real difference.
design). Beveridge System 3 (low end colored by severe cabinet panel resonances, electrostatic mid-top has wonderful imaging but a serious high-end rolloff, impedance falls to 1 ohm at 20 kHz; later samples may be better). B&W DM7 (spacious, transparent, largely uncolored, its only important fault is its high U.S. price). DCM Time Window (latest improved version is a clear best-buy at its price; transparent, smooth, detailed, can play very loud). Fried model C
(latest version is substantially improved; slightly edgy but rather good overall). Magneplanar MG-1 (no deep bass or extreme treble, severe ringing, but imaging is good). Onkyo F-5000 (smooth frequency response, but poor imaging, serious ringing, no time-alignment). Perspective Mk2 (measures flat, sounds awful, severe ringing, expensive, a rip-off). QLN 1 (transparent and focused, but crossover frequency is too low and impedance load is difficult to drive). SoundLab R-1 electrostatic (needs work, but a contender for "best," extremely transparent, uncolored, but hard for some amplifiers to drive). Swallow CM-70 (edgy and fatiguing). Vandersteen IIA (improved version the "best-focused, least colored, most balanced-sounding" dynamic speaker, but won't play loud). A Genuine Breakthrough (p. 35): A rave review of the $200 NAD 3020 integrated amplifier: "wipes out most $1000 preamps plugged into most $1000 power amps." Amplifier Reviews (p. 37): Amber 70 (best in its class, sounds a little better than the Hafler and PS). Audionics BA-150 (sweet, smooth, edgeless, but somewhat veiled; lots of IM measured). Audire Crescendo (transparent mid, edgy top). Audire DM700 (ditto). Bedini 25/25 (class A, sounds fantastically good under the right conditions). Bedini 45/45 (good but not great). Hafler DH-200 (followup report: production samples have varied, units after #3946000 are better). JVC 7050 (class super-A, sounds great, the best big amp). PS Model One (extremely good, competitive with Amber and Hafler). Sonotron PA-2000 (measures well, sounds spiky and fatiguing). MC Step-up Devices (p. 43): RWR MCT-1 transformer (almost as good as the Cotter), Marcof PPA-1 (the best head amp, a clear best-buy at its price, but not equal to the best transformers). Denon HA-1000 head amp (not recommended). Denon AU-340 and Signet Mk12T transformers (good but not great). Tape Deck (p. 45): Tandberg TD 20A open-reel deck (splendid in both mechanical performance and sound). Record Playing Devices (p. 46): DB Systems DBP-10 phono alignment protractor (neat, convenient, correctly calibrated, highly recommended). Dennesen Soundtraktor alignment protractor (ditto, but depends critically on your knowing the exact lateral pivot location). Denon 401 tone arm (OK, nicely made). Denon 303 cartridge (not as good as the 103D). Denon DP-80 turntable (it's fine when mounted in the Cotter B-i base). Discwasher Discfoot vibration isolators (worth a closer look). Fidelity Research FR-14 (gorgeously made, but no VTA adjustment). JVC MC-1 m.c. cartridge (smooth, transparent). JVC 7045 tone arm (well designed, VTA adjustable during play, may be a best-buy). Kenwood KD-650 turntable (improved version of the KD-500, relatively good arm included, isolation poor, becomes a best-buy system when mounted on a Cotter B-2 base). Linn-Sondek LP 12 turntable (overpriced, subject to low-bass feedback under the wrong conditions, parts of it are acoustically live). Ortofon MC-30 m.c. pickup (a big disappointment). Thorens TD 115 turntable (another disappointment). Wheaton 240 straight-line arm (nicely made, arm is hollow and resonant). FM Tuners (p. 51): Sequerra Model 1 judged best, with Yamaha CT-7000, Pioneer Series 20 Model F-27, and NAD 4080 close behind in audible comparisons, but FM broadcasting judged too poor to justify any serious tuner reviewing. Preamplifiers (p. 53): Audionics RS-1 (not first class but one of the best at its price). Audire Legato (pretty good but for an equalization error). Baumann Pro 4000 (measures terrific, sounds good but not great). Cotter System Two (costs $3280, not yet in real production, but is the reference standard). Hegeman HAPI Two (simply beautiful, second only to the Cotter and much more affordable). Precision Fidelity C7 (a tube phono stage plus volume control, extremely good, smooth, mellifluous). PS Audio III phono stage and LCC control center (transparent and neutral, an unequivocal best-buy, except for a mediocre m.c. head amp).

HiFi Stereophonie (Germany), March 1980 opera choir.
Opera Choirs-An Mass Ornament or People's Voice? (p. 284): About the changing role of the The Anonymous Opera Protagonists (p. 289): An analysis of the economic situation of the opera Musical Actors or Singing Walker-Ons? (p. 290): The opera business in view of the choir at the

choirs in Germany.

Benjamino Gigli, the Rat-Catcher of Recanati (p. 294): Critical remarks to the complete Disco as a Ritualized Free Time (p. 301). Small Labels: FMP, Enja, SteepleChase (p. 308). Test Reports (p. 358): Three mini components, the Hitachi ACT-M2, the Korting Series 100,

Vienna State Opera.

discography, just released by EMI Italiana.
and the Siemens Hi-Fi-System 666 (good at their respective prices), the Luxman K-12 cassette recorder (weak in several respects), the Nakamichi T-100 Audio Analyzer (very fine and versatile), The Akai SR-1100, the Acoustic Research AR25, the B&O Beovox S45-2, the Hitachi HS-3, the Sharp Optonica CP-2711, and the Technics SB-F3 loudspeakers in a psychometric test (the Sharp Optonica ranked first). Shrill Sound, Annoying Hum (p. 403): Things not to be overlooked in setting up the phono equipment, namely the interface aspects. HiFi Stereophonie (Germany), May 1980 Inflation of Music Festivals (p. 560): The aspects of this manifold phenomenon discussed. Records and Music Festivals (p. 562). An Interview with the Intendant (General Manager) of the Berlin Festival (p. 564). Folk and Minstrel Festivals Between Consumption and Contact (p. 568). Bombay Jazz-Yatra '80 Festival (p. 571). Winter Music '80 in Baden-Baden (p. 576). Cassette Recorder Anatomy (p. 611): The basics of its typology, electronics, transport mechanism, and recording level indicators explained. Test Reports (p. 632): Six cassette recorders compared: the Akai GXC-706D (good), the Dual C 810 (second best in this group), the Grundig CF 5000 (good, but the operating flexibility is a bit li mited), the Philips N 5331 (meters rather slow), the Sony TC-K 35 (best of the group), and the Uher CG 310 (good). The 65th AES Convention in London (p. 653). Festival du Son 1980 in Paris (p. 658). Modern Recording, April 1980
Reviews (p. 70): Sansui B-1 power amp (expensive, powerful, clean, conservatively rated). ADC
Sound Shaper Three graphic equalizer (flexible tuning of band frequencies, works fine, measures well). Nakamichi 680-ZX cassette deck (superb at standard spped, amazing at half-speed, obviously the best deck on the market especially with metal tape; low-end extends to 10 Hz). Ursa Major Space Station digital delay/reverberation unit (better than most other electronic reverberators, not as good as the best spring reverbs). Popular Electronics, April 1980 super-discs.
Stereo Scene (p. 14): Real and mythical differences among amplifiers, plus notes on recent
Test Reports (p. 22): Dual 606 turntable with Ortofon ULM 55E pickup (superb tracking of normally unplayable warped records, system resonance around 12 Hz but quite broad, good arm geometry, effective mass with cartridge only 7.5 grams, cartridge is pretty good, needs extra capacitance for flattest response). Mitsubishi MS-40 loudspeaker (neutral, uncolored, measures somewhat bright). Audio-Technica 1010 tone arm (medium mass, good geometry, resonance damper, outstanding tracking of warped discs).

Sound and Specs (p. 38): A thought-provoking review by Daniel Queen of why it is very difficult
to develop specs which correlate well with a loudspeaker's real-world subjective performance, and another by Bob Berkovitz noting some of the difficulties of reliable subjective evaluation and reporting on a remarkable experiment (cross-correlating signals from mikes in a dummy head) which mimics our perception of localization and maps it objectively. 3-Way Drive System (p. 46): A homebrew electronic crossover. Stereo Review, April 1980
Audio/Video News (p. 26): David Ranada reports on the first dbx encoded discs from digital
masters: wonderful potential, not fully realized in the initial issues. Audio Basics (p. 34): A really basic intro to preamps. Tape Talk (p. 36): Answers about dropouts, fugitive highs, etc. Technical Talk (p. 41): Debates about stereo imaging. Test Reports (p. 42): KLH 1 speaker (swaybacked response curve with overwhelmingly strong bass, can be played extremely loud without distress, analog "computer" optimizes bass output while protecting woofers against overdrive). Sonus Dimension 5 phono cartridge (tracks well at 1.5 g, top-end response rises to an undamped 30-kHz peak, sounds like a moving coil). Philips AH180 digital tuner (very good performance, extremely flexible digital tuning, will not be obsoleted). Spectro Acoustics 200SR power amp (very conservatively rated, has lots of dynamic headroom and lots of peak output current, no current-limiting, a best-buy candidate except that its IHF slew factor is only 2.0, so it should be used with an ultrasonic filter in the preamp). Eumig FL-1000 cassette deck (expensive, superb, auto-bias system works well, can be interfaced with computers for extreme operating flexibility, flutter is ultra-low). Equalizers (p. 72): Dan Shanefield discusses the assorted uses of EQ. - Peter Mitchell (Massachusetts) and Jiri Burdych (Czechoslovakia)
March BAS Meeting Business Meeting The March 23, 1980 general meeting of the BAS was held at GTE Labs in Waltham. Society President Peter Mitchell began the business session with a summary of the most recent Executive Committee meeting (March 15, postponed from February 28) decisions: the BAS has accepted a subscription to Wireless World; the Ivie spectrum analyzer has been ordered; the Test Equipment Committee will henceforth be a permanent standing committee-this means that chairman John Schlafer is now a member ex officio of the Executive Committee; Peter mentioned that the new draft BAS Constitution and Bylaws are to be presented to the membership at the April general meeting. The next Executive Committee meeting was scheduled for April 13. The Program Committee has developed a suggestion form listing among other items possible candidates for speakers at future meetings, subjects for meetings, test clinics, and other BAS activities. Your participation is requested. On the subject of publicity, it was announced that the BAS will run paid advertisements in the Boston Phoenix and the Real Paper (local "alternative" tabloid weeklies which often run hi-fi supplements). Also, a BAS promotional flyer is now ready from the printer. These flyers will be distributed in local and (hopefully) outlying audio stores, etc., with the goal of inducing more audiophiles to join the Society. Members (especially those from the hinterlands) are urged to help distribute the flyers. Quantities may be picked up at future BAS meetings. Jack Stevens is exploring ways to computerize the BAS mailing lists in the face of anticipated membership growth. He is interested in a good, reasonably cheap microcomputer system (used, perhaps?). In addition to maintaining the mailing lists and reducing the drudgery for Henry Belot, Frank Farlow, Jack, and others, the computer system might be used in conducting experiments on audio equipment (e.g., analyzing loudspeaker impulse response measurements, etc.). Anyone with helpful suggestions should contact Jack Stevens. Open Forum Al Foster began the Open Forum session with an offer of $5-per-foot "Mogami" speaker cable to someone willing to test the stuff and report on its effectiveness in a hi-fi system. Al went on to remind members that last November the nice people from Empire Scientific distributed various "goodies" on the understanding that recipients would report back their results of use. He complained that no such reports had been received yet. Scott Kent announced that the list price of his records is going up-to $9; therefore, his discount prices to meeting attendees will go up from the current $ 5. Peter Storkerson reported that WBUR has improved its facilities again: the station now uses SME Series III tonearms and has installed a new stereo exciter. Louis C. Souther, d/b/a Southern Engineering Products, displayed a pair of homebrew tonearms: first, an operational wooden version of the Dynavector DV-505 arm (the huge, complicated thing)-Mr. Souther claims considerably improved tracking ability for his ultra-lightweight model; second, a not-quite-completed straight-line-tracking arm system of his own design, which he promised would be ready for demonstration in the near future. Interested members might get in touch with Mr. Souther at upcoming meetings. Finally, several members discussed some of their experiences with video equipment, e.g., difficulties in duplicating videocassettes, incompatibilities between different video recorders, problems encountered in receiving certain TV channels, etc. Those seeking further details are encouraged to attend future BAS meetings.

Meeting Feature The featured speaker was Stephen F. Temmer, founder and President of Gotham Audio Corporation, New York. Gotham Audio is the U.S. distributor for several lines of German professional recording equipment: Neumann, EMT, Telefunken, and DIN test records, among others. Gotham Audio is 22 years old, but most of us didn't become aware of Stephen Temmer until about a year or so ago. That was when he effectively stalled the Audio Engineering Society Digital Standards Committee by wondering out loud (and within earshot of the Justice Department) whether that committee's activities might not violate antitrust laws. [See the February 1979 Speaker (page 5) and also Mr. Temmer's comments in the May 1979 Speaker (page 4).] The resulting flap earned him, among other things, an invitation to address the BAS. Mr. Temmer, born in Austria, was once a Vienna Choir Boy. He studied piano with Moriz Rosenthal (a pupil of Franz Liszt) and plays a Bosendorfer piano at home. His education includes a short stint at M.I.T., but he doesn't consider himself a technician. Rather, he relies on his musical ear to tell him whether things sound good, although he admits that the older he gets, the less inclined he becomes to pronounce judgment about what things sound like. His standard answer to hi-fi demonstrations is, "It's not obviously bad." It is fair to say that Mr. Temmer is still a sufficiently opinionated person to infuriate some people in the audio industry, especially the manufacturers of professional digital recording equipment. In Stephen Temmer's perfectionist view, the people in the pro audio industry have an obligation not to compromise their standards for consumer purposes. A year ago he sensed a "clear and present danger" that some in the industry, eager to promulgate the use of digital technology both in the interest of better sound and for commercial gain, would push through a half-baked digital standard which would impede further progress. His major complaint is against the proposed sampling rate standard, which would be somewhere in the vicinity of 50 kHz. Now it happens that for good technical and economic reasons, a 50-kHz sampling rate is just about the best that pro audio manufacturers can build and sell these days. That rate is compatible with current and proposed digital telephone and satellite communications systems. It is convenient, but according to Temmer is not based on listening criteria. In his opinion the rate should be at least 100 kHz, and maybe as high as 200 kHz. At a sampling of merely 50 kHz or so, he finds that the high audio frequencies "grate on my nerves"--above 2-3 kHz the sound is "discontinuous." Although most people are impressed by today's digital sound, he predicts we will all be tired of it in another 5 years. Mr. Temmer has heard experiments which demonstrate to him that as the sampling rate goes up, the sound becomes smoother, "less harsh." The ear is educable. (Anyone who has learned to play a musical instrument, or has repeatedly upgraded a hi-fi system, knows what that means.) Mr. Temmer gave an instructive example. Some years ago he (and others, including M.I.T. Professor Francis F. Lee) helped found the company now known as Lexicon. They built the first commercial digital delay line system. The first model had 60 dB of dynamic range; even with a great deal of pre-emphasis, it sounded awful. Adding more bits to get 72 dB made little improvement. Even at 96 dB it isn't perfect and still needs pre-emphasis. (Note: in a PCM system, each additional bit per sample adds about 6 dB of dynamic range.) The point of this story is that the customers thought the system impressive at first; a year later they were unhappy with the sound and clamoring for a better "next generation." In short, Mr. Temmer doesn't think we truly understand digital technology well enough to agree on standards yet. Standards impede progress. He likes the videocassette market, which is doing very well in spite of six competing systems. Such a situation may be economically expensive, but it does lead to rapid technological progress. He noted the historical consequences of too-early standardization: the English railway system (narrow-gauge, incompatible with the rest

The mechanical playback system is the simplest and cheapest of all. It uses the principle of the piezoelectric phonograph cartridge; only the recovered information is in digital form rather than analog. The disc material need have no special electrical or optical properties-high quality PVC will do. Again, it is necessary to protect the record surface from contamination. There is widespread acknowledgement that Japanese industry is besting its U.S. counterpart in terms of productivity growth, innovation, research and development, marketing, quality controlyou name it. The results are obvious when you walk into any consumer-electronics store. Stephen Temmer would agree that U.S. manufacturers are not doing a good job of competing in the consumer market. He cited the German hi-fi market as a good example of what ought to be done instead. There, he says, the German manufacturers have challenged the Japanese and are winning; he offered the Teldec digital disc as an illustration of what is possible. Teldec apparently began working on a videodisc system in March 1966, after hearing a false rumor that CBS was starting to work on the same problem. By the early-mid 70's, Teldec had a product; it was a technical triumph and, alas, a marketing flop. Today it still survives as an audio-visual instructional device for German doctors. Teldec has now adapted the technology to an audio PCM disc. Some of the specifications for the playback system are as follows: Disc material Playback system Stylus pressure Disc diameter Playing time Audio channels Groove spacing Groove speed Rotational speed Resolution Storage density Transmission bandwidth Sampling rate Quantization Dynamic range Channel separation Redundancy High-grade PVC Piezoelectric 1 milligram 13.5 cm (5.3 in.) 60 min/side (both sides playable) grooves/mm (15,240 grooves/in.) 1.66 micron/groove (0.065 mil/groove) 1.89 m/sec Between 278 rpm (near edge) and 695 rpm (near center) 0.61 micron (0.024 mil) Approx. 1 Megabit/mm (645 Megabit/in. ) 3.072 Megabit/sec 48 kHz 14-bit linear 85 dB 120 dB 8%
The master is cut into a copper blank. No "horns" result, as when cutting into lacquer. The grooves are vertically modulated by the digital information. The "chip" that results from this cutting process is finer than any copper wire that can be drawn, and is salvaged and sold by Teldec. While the master is centered on the lathe, another tool is used to introduce a locating shoulder (referenced to the same center as the grooves, of course) in the center of the disc. This ensures that each side of the final product can be perfectly centered in the playback system.

Mr. Temmer concluded his interesting presentation with playback of a copy (third generation) of one of the first true stereophonic recordings made: a performance of a Beethoven piano concerto (No. 5) by Walter Gieseking et al. made in October 1944 in Berlin using 3 Neumann CMV3 "bottle" microphones (a 1928 design still in use in places today) and an RE2 tape recorder. Aside from poor bass, especially considering the date and circumstances of the recording; antiaircraft guns could be heard in the background noise. (Note: this recording has been released on LP recently. It is reviewed in the January 1980 Hifi News & Record Review on page 119.) - Pieter Bras
The Boston Audio Society does not endorse or criticize products, dealers, or services. Opinions expressed herein reflect the views of their authors and are for the information of the members.
Acoustical Comb Filter Effects F. Alton Everest The following article is reprinted from Recording engineer/producer magazine, Volume 10, Number 4 (August 1979). Re-e/p, as it is known in the trade, is sent free of charge to qualified recipients in the U.S. Those not connected with the pro audio business may subscribe by sending $10 for surface mail delivery, $17 for air mail, for one year (six issues) to: Gallay Communications, Inc., 1850 N. Whitley Avenue, Hollywood, CA 90028. This particular issue contains a series of articles on reverberation, both natural and artificial, by BAS meeting guest Alan Fierstein, local member David Griesinger, and others. F. Alton Everest is a well-known acoustical consultant and author of many reference books on professional audio; one of his best-known works, Acoustic Techniques for Home and Studio (Tab Books, Summit, PA, 1973) is an excellent survey of sound in small and large rooms, with many practical suggestions for construction and evaluation. The author has advised us that the following corrections should be made to the piece as printed: 1. The caption of Figure 1 should read: "The diaphragm of the microphone responds to the vector sum of sound pressures from A and B." 2. Figure 2(A) is for 0.1 ms delay and Figure 2(C) for 1.0 ms delay. 3. Figures 9(C) and (D) are reversed. We would like to thank the publishers of Recording engineer/producer and Mr. Everest for their permission to reprint this article. E.B.M.
Acoustical COMB FILTER Effects (. how to keep them out of your hair. )

by F. Alton Everest

hasing and flanging are certainly well known today and those using such effects generally associate them with the term "comb filter." Less widely apprciated is the fact that in many common recording and reproduction situations comb filter effects mess up our desired flat frequency response. This is a form of amplitude distortion which is inherent in practically every listening and monitoring setup, every single or multiple microphone mono pickup, as well as many mixdowns from stereo to mono. The magnitude of this distortion depends primarily upon the geometry of the setup, although other factors enter in. Delay is the key word 1.Indealigwth sound as an acoustical phenomenon, delay is a direct result of the finite velocity of sound. For normal temperatures and near sea level sound travels about 1,130 feet per second, or 1.13 feet per millisecond. In evaluating practical problems, a very convenient thing to remember is that sound travels about one foot per millisecond. A microphone is a rather blind sort of i nstrument. Its diaphragm responds to whatever fluctuations in air pressure occur

cancellation. The same is also true in combining identical, but highly complex, signals. A B
Figure 1: The Microphone is the Vector Intersection of Sound Waves 'A' and 'B.'
It is helpful to consider how this interference effect acts down through the audio spectrum. Comb filter interference can radically affect the overall frequency response even though the system components are flat. Let us assume that a microphone diaphragm is actuated by the combination of two signals, a signal direct from the mouth of one talking, and the same signal delayed 0.1 millisecond. Without the
delayed signal let us say that the system response is flat and represented by the straight line at 0 dB in Figure 2(A). Adding to a given signal the same signal delayed 0.1 ms, the response undergoes some surprising changes. At those frequencies at which constructive interference takes place the response is boosted 6 dB. Midway between the 6 dB peaks, destructive interference creates dips infinitely deep, theoretically, 20 or 30 dB deep in practical situations. Significant energy is removed from the
signal spectrum in the vicinity of 5 kHz and 15 kHz and unnatural peaks introduced below 2 kHz, above 18 kHz, and in the 9 - 12 kHz region. Note that a linear frequency scale is used to show the symmetry of the peaks and dips. If the delay is increased to 0.5 ms the peaks and dips are much closer together as shown in Figure 2(B). It is now apparent why the comb filter name was applied to this effect. Peaks now occur at 2, 4, 6, and 8 kHz and at every other 2 kHz interval up through the spectrum. Between each pair of peaks is the accompanying dip. Figure 2(C) illustrates the comb filter effect when a signal is combined with itself delayed 1 ms. Peaks are now separated 1 kHz, as are the dips. Now that it has served its purpose of showing the inherent symmetry of the comb filter response, let us abandon the linear frequency scale for the more familiar logarithmic scale. Figure 3(A) shows the 0.1 ms delay case plotted in conventional semilog form. This gives a much better "feel" as to the effect of 0.1 ms delay on signal quality. The notches at 5 and 15 kHz would significantly color both speech and music. The 6 dB increase in level as a widening of the effective width of the dips. The 0.5 ms case is presented in Figure 3(B) on semilog coordinates. The dips appear very narrow in this plot, especially at the higher frequencies. Readers who have had experience with controlling feedback frequencies in sound reinforcement systems by applying numberous narrow notch filters might say that the dips of Figure 3(B) might be tolerable, but not welcome. No matter how it is viewed, it is a significant deviation from a flat response. Figure 3(C) illustrates the 1 ms delay example on a lot frequency scale. Dips at 500, 1,500, 2,500 Hz, etc., are interspersed with peaks at 1, 2, 3 kHz, etc. Looking at all three parts of Figure 3 we note the general principle that the longer the delay, the more the dips extend toward the low frequencies. Table I tabulates the location of the first null and spacings between adjacent nulls and adjacent peaks for delays from 0.1 ms to 50 ms. The same information in graphical form

Delay Ins 0.1 0.5 1. 5. 10. 50.
Spacing Between Nulls Spacing Between Peaks Hz 10,000 2,000 1,100 20
delayed version of itself are combined in a linear network. Applying a repetitive swept sine wave to the input and observing the output on a cathode ray oscilloscope for different delays, the responses of Figures 2 and 3 are readily reproduced. Example #1 Getting out of the laboratory and into the real world, consider the podium microphone arrangement of Figure 7. Believe it or not, such arrangements with both mikes. feeding into the same , amplifier can still be found.
is shown in Figure 4. The broken lines between the cancellation lines of Figure 4 show, of course, the location of the peaks. Effect of Relative Amplitudes In Figures 1, 2, and 3 it has been assumed
the case of multiple sources close together, each source associated with its own microphone. Let us consider the singing group of Figure 8 with each of the four singers having his or her individual microphone. Singer A is d1 inches from his or her own mike and d 2 inches from the next mike. The voice of A, picked up by both mikes, is mixed in the mixer with all the comb filter effects resulting from the path difference between d 1 and d 2. As each singer's voice is picked up, one degree or another, by all microphones, the situation gets more and more complex. Fortunately, sounds picked up by the more distant microphones are weaker and the comb filter boosts and dips are correspondingly reduced as per Figure 5. The experiments reported by Burroughs 2 i ndicate that if singer A's mouth is at least three times farther from the neighboring mike than from his own, the comb filter effects are negligible. If all singers place their microphones inside their mouths (some come close to this), the comb filter effects are submerged by other problems. If the "proximity effect" of the microphone boosts the bass, perhaps this amount of proximity will completely eliminate the highs as well as comb filter effects. Example #3 Single microphones, like single men and filter interference effect would be negligible. The soloist now moves back to a point 50" from the microphone, either to improve "ambience," simply shrinking in fear, or for some other reason good enough for us to get on with this example. The direct path (50") is now somewhat more comparable to the reflected (122.7") and the reflected component arrives at the mike about 5.4 ms later than the direct. This would put the first null around 100 Hz, the second one near 300 Hz, which could be serious if the amplitudes are close enough in magnitude. It turns out that the inverse square loss is about 7.8 dB to which we must add 0.4 dB for floor reflection and something like 1 dB for cardioid pattern 66 off axis making a total of something like 9.2 dB. This corresponds to a ratio amplitude of about 0.35 which, from Figure 5, indicates we can expect nulls about 4 dB deep and peaks about 2 dB high, or overall perturbations of our response of about 6 dB. There are things we can do to improve the situation if the soloist must be 50" from the microphone. A rug placed at the position of the floor bounce can be very effective in the upper audio frequency range. A super- or hyper-cardioid microphone could be used to reduce the reflected component another decibel or two. Thus our readily available remedies are quite limited, leaving the 50" distance to the microphone with basic

of the technique of time delay spectrometry 6 introduced in 1967 by Heyser brings acoustical comb filter effects out of the 000 closet.
References: 1 - Bartlett, Bruce, A Scientific Explanation of Phasing (Flanging), Journal Audio Engineering Society, Vol. 18, No. 6, December, 1970, p. 674. 2 - Burroughs, Lou, Microphones: Design and Application, Sagamore Publishing Company, Inc., Plainview, NY 11803 (1974). Chapters 10 and 11. 3 - Davis, Chips and Don Davis, (LEDE) Live End - Dead End Control Room Acoustics, (TDS) Time Delay Spectrometry, (PZM) Pressure Zone Microphones, Recording Engineer/Producer, Vol. 10, No. 1, February, 1979, p. 41. 4 - Everest, F. Alton, The Complete Handbook of Public Address Sound Systems, Tab Books, Blue Ridge Summit, PA 17214, (1978), pages 6266. 5 - Everest, F. Alton, Handbook of Multichannel Recording, Tab Books, Blue Ridge Summit, PA 17214, (1975), Fig. 6. 7. 6 - Heyser, Richard C., Acoustical Measurement by Time Delay Spectrometry , Journal Audio Engineering Society, Vol. 15, No. 4, pp. 370-382. Editor's Note: Additional information: Pearson, Don; Leo, Gary and Lubin, Tom, Impulse Alignment of Loudspeakers and Microphones , Recording Engineer/Producer, Part 1 - Volume 9, #6, December, 1978, page 88; Part 2 - Volume 10, #1, January, 1979, page 65. 24

A Publication of the BAS

Speaker Cables Compared Charles R. Ward, James E. Thompson, and Mallory T. Harling
In the last few years there have been a number of new "high definition" speaker cables placed on the market. Reading the cable manufacturers' hoopla leads one to believe that using these new cables will make as big a difference in the sound of an audio system as buying new speakers. You will notice a lifting of the veil that has been concealing your music, more space around each instrument, and an increase in dynamic range-or so the claims go. Two articles by R. A. Greiner in the Boston Audio Society Speaker (December 1978, March 1979) presented electrical information on a variety of cables that cast some doubt on the claims made by the manufacturers of these special cables. The figures do not refute the subjective findings of many audiophiles that these cables sound different than more conventional cables, but they do indicate that some of these differences maybe due to cable-induced distortions. The three important electrical parameters of eleven speaker cables are shown in Table 1. These data were compiled from figures reported by Greiner, manufacturers, and our own measurements. All of the cables use stranded wire construction, so skin effect should be negligible at frequencies in and beyond the audio range. Resistance values are shown as the sum of both leads of a single cable. Table 1. Electrical Specifications of Speaker Cables Cable No. 18 No. 16 No. 14 No. 12 Monster Lucas Fulton (Gold) Polk Mogami Discwasher Audiosource Inductance (H/m) 0.52 0.59 0.43 0.39 0.40 0.63 0.32 0.10 0.052 0.01 0.15 Capacitance (pF/m) 1990 Resistance (ohm/m) 0.042 0.026 0.016 0.010 0.0061 0.010 0.0010 0.026 0.010 0.016 0.021

Some of the performance differences noted for the "high-performance" speaker cables versus the more, usual speaker cables could be accounted for by the following: a. The special cables are available in precut lengths which are usually shorter than the wires otherwise supplied in hi-fi stores. This may encourage purchasers to use shorter cables. b. The special cables usually have solid, well-made connectors. This lowers the contact resistance in the amp -cable -speaker interface. c. The special cables are usually a heavier gauge wire than most people use. The lower resistance of the wire, the more power is transferred, along with a reduction of the other problems mentioned earlier. d. The special cables featuring high capacitance could be contaminating the signal by introducing high-frequency distortion. This might initially be mistaken for "better highs." The first three items would lead to more gain in the amplification chain when using the special cables. Anyone familiar with comparative listening tests will know that "louder sounds better," especially when other sonic differences are non-existent. In an attempt to collect data to test hypothesis (d), we set up the following experiment. A Hafler DH-200 power amp was connected to an 8-ohm dynamic speaker using an assortment of the cables shown in Table 1. A 10-kHz square wave was fed to the amp and monitored on an oscilloscope at the speaker input terminals. The following 14-ft lengths of cables were used: No. 16, No. 14, Monster, Polk (12 ft), Discwasher, Fulton Gold, and a twisted pair `of No. 8 wire. The waveform obtained when the amp was driving a purely resistive load was compared to those obtained using the various 14-ft cables. They were all exactly alike, exhibiting a nearly perfect waveform with a 2.5-s rise-time (10-90%). Even on an expanded range there were no differences to be observed. The same results were obtained with 20-Hz square waves. This is an interesting result when compared to claims made by Discwasher and Polk that regular parallel cables will not transmit a square wave. We repeated the experiment using 30-ft lengths of the following cables: No. 14, Polk (24 ft), Discwasher, and Audio Source. This time, using the expanded range, there were clear differences among the various cables. The cables which use a special wrapping construction (Audio Source, Polk) showed distinct saw-tooth edges on the leading and trailing edges of the square wave. The high capacitance Audio Source cable showed the most distortion. The coaxial-design Discwasher cable was a little better than the Polk cable, but the best of all was the No. 14 wire. Representations of the waveforms are shown in Figure 1. These data support our original contention that a speaker cable should be as large as possible to minimize resistive losses, constructed in such a way as to minimize capacitance, and as short as possible. Regular No. 12 or No. 10 stranded wire fits this description well.