Signals & Noise (Letters to Editor) (Dec. 1992)

Felt Found in Rogers ...

Dear Editor:

I enjoyed Richard J. Kaufman's September article, "With a Little Help from My Friends," about improving loud speaker imaging with foam rings or felt blankets. Eager to obtain maximum sound at minimum expense, I rushed to my listening room and pried the cover from one of my Rogers LS3/5A speakers. Lo and behold, I found that Rogers had already enclosed the tweeter with a rectangle of felt.

I have always been pleased with the imaging of the Rogers. Even today, 14 years after purchase, I am still very satisfied with the sound. I guess the felt really does work!

-Mark Urban-Lurain, Mason, Mich.

... and Spica and Vandersteen

Dear Editor:

In his September article on the effectiveness of foam rings and felt pads in speakers, Richard J. Kaufman says, "I don't know of a currently produced commercial speaker that uses a felt blanket on the baffle." I think there are at least two. Unless I'm mistaken, the Spica TC-50 has a felt blanket on the entire front baffle (excluding drivers, of course), and the Vandersteen 2Ce (and perhaps other models from Vandersteen) has a felt pad surrounding the tweeter. Both speakers are noted for excellent imaging and smooth highs, qualities that Kaufman noted in his own experiments with foam and felt.

-John Holdren; Greenwood, Va.

Editor's Note: Spica confirms that both the TC-50 and the Angelus employ the felt blanket described. According to Vandersteen, the 2Ce has a felt shroud covering the front of its tweeter enclosure; the Models 1B and 3 also use felt in this fashion.

-K.R.

More Felt Tips

Dear Editor.

I read with interest Richard J. Kaufman's article in the September issue. I have been experimenting with felt tweeter rings and baffle blankets for several years, and I concur with author Kaufman and the "Critic." In fact, my ears suggest that covering the baffle with felt will have a more audible effect than adding a tweeter ring. A "singing" or underdamped baffle will blur the output of all drivers. Small woofers in two-way systems are particularly susceptible, especially if they are surrounded by large baffles. Double-sided tape works well as an adhesive for the blanket, and there is silicone for the truly committed.

Boxes with rounded baffle edges will benefit from a tweeter ring, as will those with sharper edges. It need not be a ring (a square will do), and it need not have a round hole (I find an octagon easier to cut in thick felt). The hole should be about 2 inches in diameter for a 1-inch dome tweeter.

Finally, I would humbly like to point out that the wavelength of 2.7 kHz is 5 inches, not 2.

-William Reynolds

Duntech's Foam Original

Dear Editor:

I was surprised at the article by Richard J. Kaufman in your September issue discussing the placement of foam and felt surround on loudspeakers. In the mid-1970s, a company I represented as an attorney, Duntech Labs, placed an ad in your magazine for its Model DL-15 speaker system, with one of its main attributes being foam surrounding the midrange and tweeter to eliminate diffraction effects.

This treatment is subject to a patent issued to John H. Dunlavy, Jr., who was president of Duntech Labs at that time. Mr. Dunlavy has many patents in the antenna field, which has been his main area of expertise for over 40 years. He remains involved in the audio industry and is probably best known for the Sovereign line of Duntech loudspeakers.

I would appreciate your letting your readers know who was responsible for using this technology in speakers.

-Donald M. Feferman, Corpus Christi, Tex.

More Books on Hearing

Dear Editor:

I would like to know if Diana Deutsch, the author of your magazine's review of the second edition of Stanley A. Gelfand's Hearing: An Introduction to Psychological and Physiological Acoustics ("The Bookshelf," July), might have other, more up-to-date texts or summations of the subject to recommend. I intend to prepare a booklet that combines the insights of the audiophile and audiology communities with respect to techniques that might be used to sharpen perceptual skills in the auditory sensory domain.

-Michael D. Riley; Santa Monica, Cal.

Author's Reply: Mr. Riley raises an interesting question. Examples of the new approaches to hearing I referred to can be found in several journals, such as Music Perception, the Journal of the Audio Engineering Society, and the Journal of the Acoustical Society of America, though this may take some digging. You can also consult general reference works on perception, such as the Handbook of Perception and Human Performance (Wiley, 1986).

John R. Pierce's book The Science of Musical Sound (Scientific American Library, 1983) is a beautifully clear introduction to the field, written by an author with a rare understanding of the key issues involved. My own edited volume The Psychology of Music (Academic Press, 1982) will go into a second edition shortly, and I anticipate that several texts combining the in sights of audiophiles, musicians, engineers, and scientists will be published over the next few years.

-Diana Deutsch, Dept. of Psychology, Univ. of California at San Diego, La Jolla, Cal.

Hail Lieberson!

Dear Editor:

In a sidebar accompanying his splendid salute to the late great Goddard Lieberson ("The Audio Interview: A Classic at Columbia," September), Robert Long kindly mentions my grandfather, Emile Berliner, inventor of the microphone and the disc record and co-founder of Victor Records, among other accomplishments. In this respect, I am disappointed Long failed to mention that in 1964 Lieberson was presented the Maker of the Micro phone Award "for an outstanding contribution to the world of sound," a tribute to his innovation in bringing Broad way to America's back porches.

As one who is oft accused of living in the past-where it comes to the record business, at least-I'd like to point out one or two of my laments, alluded to in the article. Decca Records used to own Universal Pictures. MCA, Inc. now owns Universal and has abandoned the famous Decca label in favor of the not-so-famous MCA label. Sony has seen fit to abandon the world's oldest label, Columbia, to push the Sony logo. And where Bertelsmann Music Group continues to use (who wouldn't?) the "His Master's Voice" trademark (created by Emile Berliner in 1900 and now licensed to North American users by General Electric), we see the GE logo atop Manhattan's RCA Building and the BMG logo atop Holly wood's. What a shame.

-Oliver Berliner; Beverly Hills, Cal.

Circuit Board of Appeals

Dear Editor:

It was in 1981 that Audio published the project of the Total Harmonic Distortion Analyzer by Robert R. Cordell.

Circuit Works was listed as the source for the printed circuit board. From the start, the response was far greater than we ever expected, and it has continued all these years. We have made several additional production runs, and we still keep getting calls for more boards. With each order, we enclose assembly addenda that Mr. Cordell has furnished. Fortunately, we still have about 10 sets that are available to Audio readers.

This success story is truly a tribute to the brilliant engineering of Mr. Cordell and the vision of Audio.

-Milton Edelman; Circuit Works 85 West Sylvania Ave., Neptune City, N.J. 07753

The Job Hunt Is On

Dear Editor:

In April 1990, President Bush issued a directive for Chinese students and visiting scholars. Accordingly, I can apply for a job in the U.S. This is a great opportunity for me, and since I am looking for a job in audio engineering, perhaps some of your readers would take an interest in my skills.

I was a senior acoustics engineer in the Research Institute of TV and Electro-Acoustics, Beijing, China. After I graduated from Nanjing University in 1966, I worked in the field of electroacoustics in this Institute, including transducer and sound system re search, design, development, and evaluation. I have a very strong technical background in electrical and electroacoustical engineering, and excel lent technique with research, product management, and new product design cycles. Over the years, I have achieved much in electroacoustics, especially with loudspeakers, micro phones, and sound systems. I was awarded four prizes for my research work in these fields by the Chinese government. I also have a patent for a miniature electret microphone that was approved by the Chinese government in 1989. Since August 1989, I have been working as a visiting scholar on psychoacoustics and architecture acoustics at the University of Florida.

-Cangpu Li; 702 S.W. 16th Ave., #208 Gainesville, Fla. 32601

"Virtual Reality" with Fake Sound?

Dear Editor:

In his July "Behind the Scenes," Bert Whyte makes a dramatic statement, which is highlighted on page 21, to wit:

"For virtual reality to be successful, we must have sound quality that rivals the visual stimuli." It is becoming more evident to more visually creative people just how important sound can be to any visual stimuli. If one is able to turn a reason ably fine meal at a highly rated restaurant into a mediocre experience by the ambience or music reproduction system, then one can surmise that sound may often be even more important than visual stimuli.

As a software producer and proponent of "quadraphonic" sound (there. I said it and I'm glad!), I was recently asked a simple but very serious question: If I had only two choices, would I opt for discrete multi-channel systems for recording and reproduction, or would I be satisfied with artificial simulation of multi-channel sound as long as it was digital? My answer, of course:

Discrete multi-channel capabilities far outweigh the importance of the actual archival format-analog or digital! But since we now have the benefit of both-discrete multi-channel systems with digital sound, in both professional and consumer applications-why are we wasting time on attempts to defy the laws of mathematics? In order to present believable and accurate audio stimuli, a sound field must be created. A sound field re quires a minimum of four balanced audio channels and loudspeakers, and a recording technique that emulates the symmetry, time, amplitude, and phase that allow the human ear/brain computer to localize images. A four-channel headphone set is possible to accomplish this task as well (I have one).

Suffice to say, you cannot solve four unknowns (the mathematical proper ties of a sound field) with two simultaneous linear equations! This law applies to 4-2-4 matrix schemes as well as to phase manipulation schemes, no matter how complex the algorithms nor how powerful the computer.

Since most HDTV formats, new consumer and professional digital video formats, and film soundtrack formats of the future all contain [or will contain] discrete multi-channel and digital capabilities, what on earth are we still doing, talking about anything that synthesizes or simulates reality like a cartoon? For special effects, like equalization, echo, flanging, exciters, and so forth, I can buy it. But to suggest that sound fields can be created by defying the laws of mathematics heaps scorn on a professional audio industry that could do without it.

What those of us in the creative com munity must do is learn how to implement discrete multi-channel audio in order to lend that credibility to our creations, as Whyte suggested with his "virtual reality" comment. Our hands have been bound for too long, limited to two-channel delivery formats. No more, and it couldn't have come too soon to suit me!

-Brad S. Miller; Mobile Fidelity Productions of Nevada; Incline Village, Nev.

Editor's Note: Brad S. Miller was the music industry representative on the National Quadraphonic Radio Commit tee (NQRC), which was cosponsored by the FCC and the Electronic Indus tries Association (EIA) and was charged with testing and evaluating four-channel broadcast systems. He also was the founder of Mobile Fidelity Sound Lab.

-E.P.

(adapted from Audio magazine, 12/1992)

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