My work in audio electronics was always on a parallel path with music - separate but parallel. That is, until the two paths merged in the '80s to become different aspects of the same activity. The skills in both areas were complimentary and interactive. It became clear that these intertwined skills provided an advantage to me over those who had considerable abilities in either music or audio, but not both.
One thing that must be understood about a great many of the projects described on this website is that I have always been inclined to custom design and build to my own needs. This included audio designs for a variety of purposes and also woodworking/cabinet construction. Occasionally, I will be using the word "custom" in a description: Now you know what that means.
Before I begin to list my activities in audio here's a fundamental piece of important information: You didn't want to be an electronic device around me when I was young - I would disassemble you to see how you worked. Disassembly was easy, the trick was successfully putting things back together in working order - my percentages were high but not without casualties. Phonographs, radios, televisions, and tape recorders were among the equipment that fell prey to my explorations. These unfortunate devices would actually squirm when they saw me entering the room.
What, When, and How
There is so much chronological information to list in this section that I am going to take this opportunity to uncharacteristically write in clipped and fragmented sentences! Deep breath, here goes:
- Voraciously devoured technical books on electronic circuit design for reel-to-reel tape recorders at age 11, beginning a long obsession with recording equipment and related electronics.
- Designed and built a tape recorder magnetic "head" about that time out of parts from the local hardware store - didn't work well, looked odd, but was a nice try and taught me a great deal about the requirements of such an exacting device, especially the impracticality of DIY magnetic gap construction.
- Ran an intercom system between my ground floor bedroom and the upstairs bedroom of an adjacent house to communicate with friends in 1959. I should check my messages.
- Received a monaural portable tape recorder as a Christmas gift in 1960.
- Combined the tape recorder with a phonograph turntable to allow experiments with higher tape speeds vs. frequency response performance in 1961.
- Experimented with transistor amplifiers and crystal microphones in 1961.
- Designed and built my first dynamic 2-way speaker system in 1962. Delved into passive crossover design for the first time.
- Acquired a monaural portable AIWA tape recorder in 1962. As a high performance tape recorder it was primarily cute.
- Recorded at the 1962 World's Fair*1and junior high school concerts.
- Designed and constructed a tape recorder from scratch in 1963 for a science project. Biggest challenge was the mechanical design of the capstan/pinch roller/reel drive motors. Record/playback/erase heads and amplifiers were cobbled together from items available in mail order catalogs. Most interesting part of the design was a high frequency bias oscillator for reducing harmonic distortion, if that's your idea of something important.
- Acquired a German-designed Butoba MT5 monaural portable tape recorder in 1963. Photo on right. Used it for field recording and manipulation of playback speed for experiments in audio special effects. Yes, it got disassembled. Many, many times.
- Designed and constructed an LP turntable and arm in 1964. Re-purposed many standard hardware store parts in the construction and cannibalized an old record player. Learned much about turntable suspension systems and arm/cartridge alignment and balancing.
- Designed and built several solid state preamps and power amplifiers in 1964 with different design types (class A, A/B, etc.) Placed frequent orders to Polypaks, a company that packaged bargain-priced, below-spec parts that, nevertheless, gave me raw material in the form of resistors, capacitors, transistors, diodes, etc. to paw through for my projects. Great stuff for the inveterate electronics experimenter on a kid's budget!
- Recorded high school concerts.*2
- Designed and built a custom Theremin using metal pie plates (!) - may have been the first boysenberry Theremin in history.
- Built an audio workstation in my bedroom. The photo to the immediate right shows what it looked like circa 1966. The blowup to its right shows a portion of the photo focusing on the exposed internal mechanics of the, by then fully assaulted, Butoba tape recorder. It also shows my new Acoustic Research turntable in the foreground - before any inevitable modifications had taken place. The full shot reveals, beneath the AR turntable, the exposed electronics of the tubed receiver with which I had tinkered extensively. Nothing was safe from my prying and inquisitive fingers. Make up your own jokes.
- Designed and built a wall-mounted subwoofer system that used the attic as a baffle. Any birds landing on the roof quickly thought of themselves as earthquake detectors. It would actually cause a flaking around their claws called "Richter Scales."
- Designed and built a direct/reflecting speaker system with integrated compensatory equalization in 1968. I'm sure you can imagine the inspiration for that one.
- Designed and built, from scratch, a modular music synthesizer and created a 2.5 octave controller keyboard for it in 1968. The electronic modules consisted of oscillators, filters, envelope generators, and various modulation sources (see synthesizer link in last sentence.) I used a patchcord system to link the various modules. Composed a few electronic music pieces using this setup, none of which have survived. We'll never know whether this is a bad thing or a good thing.
- Acquired a Sony stereo reel-to-reel tape recorder in 1968.
- Recorded college concerts (again, all tapes apparently lost, to my puzzlement.)
- Experimented with razorblade tape editing techniques and sound effects in 1969.*3
- In 1970, experimented with acoustic delay lines for ambience extraction employing the "Haas (precedence) effect" to separate non-correlated reflections from direct sound arrivals based on research articles in the Journal of the Audio Engineering Society. Loved that periodical - always inspired ideas for experimentation.
- Designed and built a 5 band graphic equalizer in 1971. Used it to experiment with concepts of room equalization even though the filters were too broad for truly effective compensation of typically narrow room modes.
- Acquired a Sony 4 track reel-to-reel tape recorder in 1972 and experimented with indoor and outdoor multitrack recording. Built a custom console for the recorder and a Phase Linear preamp plus other audio equipment. Expanded the audio playback system to 4 channel. Photo on right: You can also see Dynakits, an octave band graphic equalizer, Philips turntable, and other equipment stacked around the custom console. Audio hardware accumulating. Bank account shrinking.
- Modified Large Advent speakers to time-align the tweeters with the voice coils of the woofers and reduced the effect of diffraction on the radiation pattern of the tweeters through separate offset mounting.
- Experimented with piezoelectric excitation of glass plate high frequency radiators and also with ribbon tweeters in 1973. By then, few people had any idea of what I was doing or why. See, you're not alone.
- Acquired a Sony portable stereo cassette tape recorder and used it to extensively document travel in 1974.*4 As you can see by now, Sony hit the price/feature sweet spot for me at the time.
- Modified Dahlquist DQ-10 speakers to have mirror image driver layout between left and right speakers. Designed and added a single, shared subwoofer to the system.
- Began experimenting with binaural recording in 1975. This started with the purchase of a Sennheiser Binaural microphone/head combination.*5
- Designed and built a custom listening chair that incorporated near-field surround speakers in the chair structure in 1977. An early 8 bit digital multiple delay line with controls installed in the arm rests was used to adjust ambience extraction and simulate different sized rooms from the listening position without having to get up from the chair to make those adjustments. The modified Dahlquist DQ-10 speakers were used up front. I think you'll agree: The transition to mad scientist was complete.
- Modified a Magnepan line source planar magnetic speaker system for lower diffraction and designed a dual 10" push-pull subwoofer system to augment its bass in 1982. On left:
- Fully re-designed and built a 6ft tall 4-way line source planar magnetic speaker system (with a new, custom 4 ft. tall ribbon tweeter array) using phase coherent passive crossovers. Actually raised the floor to accommodate four floor-mounted dynamic subwoofer systems using the space between the new joists as baffles in 1983. Above right. Even the couch and equipment cabinet in that photo were custom built.
- Designed and built another turntable in 1984 using parts from an old commercial design while adding a new arm and suspension system along with brushed aluminum cosmetics. On right:
- Designed and built inverted, soffit-mounted 3-way dynamic near-field monitors with ribbon tweeters for the studio in 1984. On right:
- Designed and built an experimental seven channel surround sound music system in 1986 as an extension of the large planar magnetic speaker system. It used a Yamaha DSP-1 digital room simulator and several self-designed surround speakers for soundfield immersion.
- Delved into MIDI (Musical Instrument Digital Interface) and sampling keyboards for the first time in 1987. Also acquired my first MIDI sequencer and drum machine (Alesis MMT-8 and Alesis HR-16.)
- Was hired to operate an Alesis MMT-8 hardware MIDI sequencer during on-the-fly recording of music for TV productions in first job for PBS in 1988.
- Designed and began building the first dedicated professional version of the new The Vocal-Free Zone recording studio in late 1988/early 1989 as described on the Vocal-Free Zone page of this site.
- Designed and built near-field dynamic monitors using Focal drivers in 1991. The monitors were mounted to the bridge of the console of the studio, as seen in the photo on the right:
- Worked extensively with synthesis/sound design, audio sample recording/programming, plus computer integration of sequencing and digital audio recording between 1988 and 2000 for use in PBS productions and personal projects.
- Worked as an audio and acoustical consultant in studio design and was troubleshooter for local recording studios between 1987 and 2000 (often for difficult-to-resolve ground loop issues - "hum a few bars and I'll trace it.") Occasionally hired out as a recording engineer to other studios and also for live performance location recording for various groups.
- Designed and built reference speaker monitor systems for other recording studios in the early 1990s.
- Designed and built reference dynamic speaker monitors incorporating honeycomb internal bracing, minimum diffraction external geometry, time-aligned drivers, and phase coherent crossovers with integrated push-pull subwoofers for The Vocal-Free Zone in 1994.*6
- Custom-built additional computers dedicated to Gigasampler software in 1998 and several thereafter, as needed in the studio, for additional capabilities and upgrades. Custom built computers were economical and tailored to exact work needs. Knowing how they worked reduced "down time" when something broke because I knew how to fix it without relying upon a repair service.
- Redesigned and built 2nd version of The Vocal-Free Zone in 2000. Supervised, engineered, and edited the recording of many brass, woodwind, string, keyboard, and percussion instruments used in Garritan sample libraries between 2001 and 2011. Recorded myself on various brass instruments for these libraries where I forced myself to perform at the highest level by threatening to release outtakes of the worst performances if things didn't go well. In fear for my reputation, I successfully convinced myself that I played flawlessly. Blackmail averted.
- Redesigned and built scaled-down 3rd version of The Vocal-Free Zone in 2011, tailored to post-retirement composing and recording projects.
- See Vocal-Free Zone, PBS, and Garritan pages for more info and pictures. Full sentences and generally acceptable syntax will now resume, but I make no guarantees.
The Zoom r16 was my primary field recorder for several years until I no longer needed a field recorder. It is compact and convenient. It also has the ability to record up to 8 tracks at a time onto an SD card while monitoring and has a bevy of mixing features (which I rarely use since I export the raw tracks to the computer for editing and mixing.) Sound quality is excellent. Out of curiosity I tried to list the cost of equipment I would have needed 20 years ago to duplicate the capabilities of this little $400 wonder. I stopped counting at $35,000.
*1 1962 World's Fair. This excerpt was recorded with an AIWA portable tape recorder running at 1 7/8ips with a small dynamic microphone. The condition of the tape has deteriorated badly over the years and the quality of the sound was pretty awful to begin with but it's a fascinating document from 50 years ago! This selection was recorded in the House of the Future exhibit. I chose the excerpt because this part of the exhibit looked "into the future" of home technology (beyond the distant year 2000) and the guesses were remarkably prescient in conception if not in the details of just how things would come about. These prognostications included home projection television, personal video recorders, home computers, online banking and magazines, etc. It's also amusing to hear the very 1950s slant on male and female roles - we certainly lived in a world of confined expectations back then - "good old days" indeed. Roll your eyes and snicker at will. The photo above shows my younger brother Rick and me, with recorder slung over my shoulder, standing in front of one million silver dollars or, as we affectionately called it, "pocket change":
*2 High School Band - Director: Wally Rants. This is a Christmas concert excerpt. Recorded with the monaural Butoba portable at 3 3/4ips using the dynamic microphone that came with the recorder. I'm in the band so my mother is being indulgent enough to press "record" and "stop" for me. Her patience sometimes reached a limit with comments like, "Oh Tommy, put that thing away, you don't have to record everything." Fortunately, I didn't take her advice and can now hear her voice (and many others' long departed) anytime I wish:
*4 1974 - Disneyland - Taken from the many hours of material I recorded in Southern California that year including these Disneyland clips. This uses a Sony Stereo portable cassette recorder with Dolby Noise Reduction and a Sony stereo electret microphone. The recording quality is excellent and very vivid, especially over good headphones. I've included two clips: One of the Disney band on Main St., and one of children on Tom Sawyer's Island with a Dixieland band passing on the river boat. How odd to realize that those little children heard enjoying themselves in this recording are now nearing 50 years of age! Not a pleasant thought:
*5 1993 Binaural- I created the following recording for friends as a demonstration of the remarkable verisimilitude possible with binaural recording. It requires the user to wear superb headphones or earbuds to fully experience the effect. The effect cannot be achieved with speakers of any kind. Set the volume level to be as natural as possible for the distances that are being identified by me as I talk on the recording - use your intuition. Under the right conditions this recording can be uncannily realistic to thesides, behind the head and above - it can give the illusion that events from 20 years ago are happening around you right now! Recorded with a binaural head, AKG460 cardioid capsule mics pointed into the binaural head ears and then recorded directly to Digital Audio Tape. Most binaural heads incorporate the microphones into the ear canals of the head. That's the purest way of recording binaural sound but the external method I used is still very effective. I named the binaural head Eric (ear ache):
The Design and Construction of a Reference Studio Speaker System
The most advanced speaker system I designed and built over the years was a three-way dynamic reference studio monitor for the Vocal-Free Zone in 1994. I incorporated virtually everything I had learned concerning speaker design, much of it borrowed from the best commercial designs of the time. I mixed many ideas together into an unusual speaker system of remarkable prowess. The resulting system was neutral in signature, extended in range, and excelled at producing precise imaging with a wide, very deep soundstage. It was my main studio workhorse for over 15 years and truly was reference quality. I never felt the desire to replace it with a commercial system of any kind – it was that good. I retired it when I retired. It now lives happily at another musician's home. I still get a card from it at Christmas.
What I'm going to do here is describe how this system was built, a process that is definitely not for the faint of heart! First, let me point out that this article is not a detailed step-by-step on how to build such a beast; it's just an overview to show what the goals were and how I constructed it. To be clear: I'm not including crossover circuit schematics, a materials list, or dimensions . . . but the information is really, really interesting if you have ever wondered how something like this could be done.
The primary technical goals included: Extended, extremely linear amplitude response (an honest 20hz to beyond the audible spectrum within a couple of decibels;) linear phase response over as much of the spectrum as possible (on general but unnecessary principles I wanted it to pass a recognizable square wave;) copious output (play louder than I could stand to listen;) minimal edge diffraction, cabinet resonances, or internal interference modes; and nicely finished - just because.
Each side of the design consisted of two cabinets. The top cabinet was a two-way design that handled frequencies from 80hz on up. The lower cabinet (upon which the upper cabinet sat) was the subwoofer section which handled frequencies from 80hz on down. The entire system, therefore, acted as a complete 3-way system. Both top and bottom cabinets were sealed designs. All drivers were sourced from Dynaudio. The top cabinet crossovers were passive, linear phase, 6db/per octave configurations which, in conjunction with the time-aligned positioning of the drivers delivered nearly linear phase response across the full operating range of the system. The drivers were specifically chosen to handle the enormous wide bandwidth demands of these lower order slopes. The subwoofer crossover used a passive linear phase 18db/per octave design which ensured that frequencies beyond its intended range were effectively suppressed. The subwoofer design also used a dual push-pull downward-firing driver arrangement which was intended to be pointed at a carpeted floor; the carpet aided in the acoustical suppression of unwanted higher frequencies so the upper frequency rolloff was actually steeper than strict calculations would predict. The push-pull arrangement of the subwoofer drivers was engineered with the drivers facing one another and wired out of phase with respect to each other – thus causing the cones to move in unison pistonic action. The air trapped between the two driver cones bolstered the cone stiffness; the drivers' waveform nonlinearities at maximum voice coil travel were inverted in phase with respect to one another, so 2nd harmonic distortion was effectively canceled; and twice the magnetic motor force was applied to the large enclosed volume of air in the cabinet, lowering the system resonance point and, thus, extending the low frequency cutoff point to reach the bandwidth goal for the cabinet size. The crossovers were placed in a separate chamber at the outer back of the subwoofer cabinet, isolating electronic components from any internal air pressure changes caused by driver motion. All crossover components and wiring were carefully chosen and tested using the finest parts available at the time. Critical portions of the crossover circuitry were made adjustable so that the design could be “tweaked” during the final phase of testing and refinement, which included long and careful listening sessions once measurement goals had been confirmed. Ears were the final arbiter of success. In this case at least, measurements and ears reached the same conclusions. It wouldn't have been pretty had things degenerated into a huge disagreement between the two. If the disagreement had actually ended up in court I suspect it would have been called a hearing hearing.
The functions of the speaker cabinet were manifold. It needed to be as inert as possible, contribute minimal internal standing wave resonances, and effectively compliment the function of the speaker driver by determining, as a system, the point and rate of driver response roll-off. Ideally, in a sealed enclosure design, only the drivers should be radiating energy into the room, not the enclosure walls. The cabinet should also minimize diffraction effects on the exterior front surface to avoid secondary wave propagation disruption while also time-aligning the voice coils of the different drivers with the ideal backward slant (relative to the exact intended listening position.) The photos in the sidebar to the left reveal the construction techniques used to approach these goals. Note the following:
The walls were constructed of two layers of 3/4” MDF laminated with glue for increased rigidity and mass.
The side-to-side and front-to-back surfaces were angled to minimize and spread specific internal reflective frequency nodes over a range of frequencies. The front-to-back angled front baffle also accomplished the voice coil time alignment for the woofer and tweeter in the upper cabinet while the side-to-side angle spread the frequency components of the external edge diffraction.
Internal honeycomb bracing was employed to further strengthen the rigidity of the cabinet with internal support and damping of the walls spaced every few inches in all directions. The honeycomb construction used strategically placed holes to allow coupling of all the internal air so that the primary driver “sees” the maximum internal air volume while obtaining maximum structural rigidity of the cabinet. The liberal use of glue for maximum strength of structural coupling can be seen in the photos.
All internal surfaces were coated with silicone caulk for additional damping of structural resonances and vibrations.
The tweeter mounting hole was closed off to the rest of the cabinet using a subchamber so that air pressure from the top cabinet woofer could not penetrate to the tweeter driver.
Once assembled, the exterior finishing process began with sanding and filling to create a smooth external surface.
The cabinets then were sprayed with flat black paint.
Solid oak panels were then attached to the sides of the top cabinets to add still greater mass and strength to the largest side cabinet surfaces. Damping of the side walls was also increased by the density differences of the various layers. The total thickness of the side walls was an unusual 2.25 inches.
About two dozen coats of glossy Varathane were then sprayed to complete the external finish of the cabinets.
The subwoofer cabinets underwent a similar finishing process.
Fiberglass was loosely packed into the cabinets for absorption of energy and the additional beneficial thermal effect on the free air resonance of the woofer and subwoofer.
The drivers were installed along with wiring and crossovers. All crossover components were housed in a separate chamber attached to the upper back of the subwoofer cabinet.
Rollers were installed on the bottom cabinets for convenience in moving these behemoths around (each side weighed over 150lb.)
Finally, testing and adjustments were done with a combination of careful measurements and analysis, plus extended listening tests. The adjustment process took about four months. I never found it necessary to revisit the final adjustments. The entire project took about 6 months to complete from start to finish.
I had intended to name them the "Platinum" model but a friend, for whom I had designed and built a previous studio monitor system, said, "Hey, I wanted mine to be the 'Platinum' model!" I acquiesced. His speakers got to be the "Platinum" model . . . mine became the "GRAND MASTERS!!"