TECHNICAL LETTERS
Over the years, Altec, and
Altec Lansing, produced a large number of technical letters for use by
consultants and contractors. We have many of them available now online
to help you.
We now have a large assortment of Altec Techincal
Letters for your use and enjoyment.
If they help you, let us know, and, as always, your donations are
both needed and willingly accepted (just use the PayPal
DONATE button on
the main page). 
CLICK ON THE LINKS BELOW TO DOWNLOAD
THE LITERATURE YOU ARE
INTERESTED IN:
TL-102
= Amplifiers In Parallel - Instructions for constructing a
circuit using an Altec 15067 Autotransfomer that makes it possible to
parallel the outputs of two power amplifier. May 16, 1960.
TL-103
= Loss In Telephone Cable Circuits
- Informative Chart. May 16, 1960.
TL-104
= Zone Volume Control - Instructions for building a zone
volume control for distributed, 70-volt speaker systems. May 16, 1960.
TL-105
= Area Covered By A Horn Beam
- Subtitled "A Problem In Geometrical Projection", this Technical
Letter
is an excellent resource for those wishing to get in on the basics of
the behavior of multicellular and sectoral horns.
TL-106
= Altec 70-Volt Matching Transformers
- Excellent information on Altec transformers for use in 70-volt
distributed sound systems. Includes pictures, charts, and comparisons
with competitive products of the time.
TL-107
= Essential Requirements For Speech Reinforcement Systems
- An excellent early
paper on application and design of sound systems. Often misunderstood
by today's system designers, these principles are A MUST SEE!
TL-108
= Sound System Power Requirements
- Our old friend Don Davis' influence really begins to shine through
with this Technical Letter. Another excellent paper on proper
design of amplifier power requirements for sound systems that gives
principles most designers today have forgotten (if they ever knew).
Includes a helpful nomograph.
TL-109
= Ventilation Or Sure Death
- An interesting TL regarding the importance of keeping transformers in
sound systems cool, and so increase their life expectancy. Note the
references to owners of Altec sound systems keeping them for 30+ years.
TL-113
= Loss Due To Speaker Lines - Excellent instructions
for calculating the size of wire needed for a specific application.
TL-121
= Protection For High Frequency Driver Units
- Dr. John K. Hilliard's expertise in making applications of Altec
Lansing
products interesting, understandable, and practical show here. Includes
information on AL passive crossovers and protecting HF drivers from
static discharge.
TL-122
= Line Voltage Compensation
- Another Hilliard-influenced Tech Letter for those who have problems
with varying power sources for their sound system equipment.
TL-123
= Altec 755C Loudspeaker
- An interesting TL replete with application information and frequency
response charts for this very famous speaker.
TL-124
= Output Power and Maximum Gain
- More technical information forgotten by the modern sound system
designers/installers. Covers concepts and includes a chart about
calculating electrical gain in Altec sound systems.
TL-128
= Altec Voice Warning System, Part 1
- Pages 1 - 8 of the original manual on how to design and install a
properly operating Emergency Warning System using voice projection.
Later called "BIG VOICE" and then "GIANT VOICE", systems of this type
are still the BEST way warn the public in an emergency.
TL-128
= Altec Voice Warning System, Part 2
- Pages 9 - 12 of the original manual on how to design and install a
properly operating Emergency Warning System using voice projection.
Later called "BIG VOICE" and then "GIANT VOICE", systems of this type
are still the BEST way warn the public in an emergency.
TL-128
= Altec Voice Warning System, Part 3
- Pages 13 - 16 of the original manual on how to design and install a
properly operating Emergency Warning System using voice projection.
Later called "BIG VOICE" and then "GIANT VOICE", systems of this type
are still the BEST way warn the public in an emergency.
TL-133
= Standard Pads - An invaluable tool for designing
audio pads. Every sound system designer and installer should have and
use this!
TL-134C
= Typical Specifications for Altec Lansing Voice Warning Systems
- Originally prepared for Vandenberg Air Force Base, these
specifications were for system designers to use as a basis for writing
"specs" for similar systems they might be called upon to design for
bidding. Circa 1963.
TL-135
= Typical Mounting Of Three #31A Horns For 360-degrees Of Coverage
- Interesting.
TL-136
= Engineering Information For The 695A Microphone
TL-137
= Altec 21BR Microphone
- A complete listing of all of the versions of one of the most famous
of all the Altec microphones.
TL-139
= Wind Noise Reduction In Microphones
- Windscreen applications for the famous Altec M-20 and M-30 Condenser
Microphone Systems, many of which are still in use. Nothing sounds
better!
TL-140
= Special Application For the 695A Microphone
- One of the BEST of all of the hand-held paging/announcing microphones
ever built by any manufacturer, the Altec 695A Noise Canceling
Transistor Microphone, this TL shows how to adapt it so that there will
not be any "switching pops" when in use.
TL-141
= Handbook Of Altec Sound System And Installation Data
- Again, our friend Don Davis' abilities to educate shine through in
this, the first thorough manuals on "how to" design a properly
functioning sound reinforcement system. Topics covered include: Time
Delay; Accessory Panels; Priority Systems; Compressors; Impedance
Matching; Hybrid Transformer; Signal Circuit Wiring; Cable Capacity;
Design of Standard Pads (almost NO ONE knows how to do this today!);
Voltages for Various Power Levels; Number of dB for Voltage or Current
Ratio; Electrical Power vs Electrical Power Level; SPL vs Acoustical
Pressure; Length of Cable vs Loss at 10 kc & 20 kc. FASCINATING and
another MUST READ for
all those in the design and installation of sound reinforcement
systems!!!!
TL-143
= Adapting the Altec 695A Microphone For Use With Altec 1568A and 1569A
Amplifiers
TL-145
= Modification Of Altec 351C Amplifier For Use With Altec 695A
Microphone
TL-146
= Altec 351B Modification For Microphone Operation, Using Altec 1578A
Preamplifier
TL-147
= "Profitable Business Management"
- Address given at the 1964 Altec Lansing Seminar by Mr. C. R.
Rininsland, Altec Lansing's VP of Finance. Very good!
TL-148
= Two Papers On Microphones
- Presented by our good friend, Mr. Bill Hayes, at the 1964 Altec
Lansing Conference, this TL covers very interesting and valuable
information about the design, construction, and use of high-quality
microphones.
TL-149
= "Over 40 Years In The Sound Business"
- This address, which was given at the 1964 Altec Lansing Conference,
was presented by Mr. Milton Boom, President of BOOM Sound Engineering
of Chicago. One of the most interesting men to ever be in the sound
business, Mr. Boom presents his experiences in a manner that is both
informative and entertaining. EVERY person interested in sound systems
needs to read this gem!
TL-156
= Two Papers On Selling
- Second only to Dr. John K. Hilliard, W. H. Johnson was THE PREMIER of
all salesmen for Altec. These two papers, "What Is A Salesman" and
"Satisfied Customers (the function of selling)", ought to be
required reading for everyone in sales operations, regardless of their
field of selling. DON'T MISS THIS ONE!
TL-157
= The "How" and "Why" Of Writing Altec Specs
TL-158
= Acoustical Tube Delay System
- One of the finest men to ever work for Altec, Ed Seeley worked for
ERPI, and came along with George Carrington, Alvis Ward, etc., when the
formed the All Technical Service Company in 1936, and stayed with Altec
until his retirement. Mr. Seeley wrote this interesting article on
pre-digital delay problems and a practical solution to them! Mr. Seeley
died not too long ago of Alzheimer's disease - a sad thing to happen to
such a great mind!
TL-159
= Objective Technical Specification for the Altec M50 Solid State
Condenser Microphone System
TL-160
= Advertising Sales Brochures
- VERY INTERESTING! A neat set of examples of Altec's sales literature
in the mid-1960's.
TL-162
= Sound Coverage: Degrees vs Distance - Still
accurate and up-to-date, this TL from Don Davis shows how to calculate
coverage for a ceiling-mounted distributed loudspeaker system. EVERY
SOUND SYSTEM DESIGNER & INSTALLER SHOULD READ THIS ONE!
TL-163
= Amplifier Comparison Tests -
A VERY GOOD primer on how to test power amplifiers for output
performance.
TL-165
= Altec "TRUTH BOX" Transformer Demonstration Board -
Even today, those who saw the Altec "Truth Box" in operation vividly
remember it's ability to demonstrate how cheaply built most "other"
transformers were. Someone ought to build one and test TODAY'S
transformers - it might be quite surprising to hear the results...
TL-162
= Sound Coverage: Degrees vs Distance -
Still accurate and up-to-date, this TL from Don Davis shows how to
calculate coverage for a ceiling-mounted distributed loudspeaker
system. EVERY SOUND SYSTEM DESIGNER & INSTALLER SHOULD READ THIS
ONE!
TL-166
= Decibels
- Don Davis is at it again: training Altec Engineering Sound
Contractors and acoustical consultants how to understand the behavior
of sound and help them design and install better systems!
TL-166
= Quick Reference Chart For 70-volt Systems -
Another Tl that is still useful today! Shows watts, dBm, Load
Impedance, & Speaker Wire Size.
TL-169
= Graph Relating Thermal Noise To Bandwidth -
Jim Noble was one of the really brilliant minds at Altec during it's
heyday. In this TL, he gives a simple illustration as to the proper way
to design a noise-free sound system.
TL-169
= Instructions For Detailing "Typical Specification" Sheets -
In this TL, Jim Noble shows how Altec developed the format of the "spec
sheet". Still in use today, and largely unchanged, this is a VERY
interesting piece of Altec history. March, 1967.
TL-170
= A Collection Of Questions By Sound Engineers Concerning The
Alternating Current Meter
TL-171
= 70-volt Line Impedance Bridge - Our
ever-practical friend Don Davis wrote this TL to help Altec sound
contractors make sure that the systems they install perform without
failure. Still accurate and up-to-date, EVERY SOUND SYSTEM INSTALLER
SHOULD READ THIS
ONE!
TL-172
= Peak Factor Demonstration Test Set -
Altec's Lou Graner shows how to build a test set that will show the
difference between RMS voltage and the true peak voltage encountered in
the complex waveforms of music and speech.
TL-173
= Portable Peak-Responding Voltmeter, Calibrated In RMS Volts
-
In this TL, Lou Garner shows how to build and use this device.
TL-174
= DC Capabilities Of Altec All-Solid State Amplifiers -
Altec's Jack Shechtman gives a veritable gold mine of valuable
information regarding Altec's early solid-state amplifiers.
TL-175A
= Replacement Transistor List -
Much like a "tube substitution chart" for vacuum tube radios and
televisions, this TL gives invaluable information owners of older Altec
solid-state amplifiers when in need of repair.
TL-181
= Inverse Square Law Calculator -
As our friend Don Davis pushed the Altec contractors and acoustical
consulting community into ever-deepening seas of sound system
performance prediction and design, this TL became the cornerstone of
all that he and his dear wife Carolyn would spend the rest of their
professional careers doing: writing, training, and educating. EVERY
SOUND SYSTEM DESIGNER AND INSTALLER
SHOULD READ THIS
ONE!
TL-182
= Engineering Loudspeaker Locations -
Another milestone in the writings of Don Davis, the principles for
proper loudspeaker system design - largely forgotten today - are well
explained here. Another MUST READ for EVERY sound system designer &
installer!!!!
TL-183
= Directivity Of Loudspeakers And Microphones - Written by
our friend and colleague, Don Davis, this is one of the BEST articles
ever written on the subject. Includes a reprint of the now famous paper
on the subject by Hopkins and Stryker.
TL-187
= Altec 9473A Limiter Amplifier -
Specifications for this early two-channel limiter. Interesting!
TL-192
= Amplifier Impedance Effects On The Transfer Characteristic Of Filters
And Equalizers -
Altec's Director of Engineering, Jim Noble, shows how to make certain
that the input impedance to Altec amplifiers is not altered by external
filters or equalizers. Interesting!
TL-196
= Calculating And Using Critical Distance -
Here's Don Davis again with a TL that, coupled with TL #'s 181, 182,
& 183, makes for excellent reading. It would do the modern
generation of system designers and installers to read it!
TL-197
= Calculating The Maximum Electrical Power Required -
Again Don Davis shows us methods now forgotten by modern system
designers (until something blows up). How often have we seen systems
shut down when the A/C power breakers tripped because the designer or
installer forgot (if he ever knew) the principles laid out here?
TL-198
= New Ways To Look At Potential Acoustic Gain -
As we get into the second generation of sound system designers and
installers who have never heard of PAG/NAG, it would do them well to
read this! Thanks Don!
TL-199
= Finding A Realistic EAD -
Don't know what EAD is? Well, it's not surprising! Read here to find
out as Don Davis - again - makes it clear how to design sound systems
that work BEFORE they are installed!
TL-201-A
= Useful Directivity Data For Reverberant Sound Fields -
Altec's Chief Engineer in Acoustics, Bob Beavers, gives valuable
directivity information on famous Altec horns, including the 811B,
511B, 311's, and multicellular models. If you use these horns, this
will interest and hep you!
TL-202
= Modification of Altec 1591A Compressor For Use As A Line Amplifier In
Altec Acousta-Voicing Network
TL-203
= Measurement of Nominal Sensitivity Ratings For Horn-Driver
Combinations Commonly Used In Acousta-Voicing
- An interesting TL on the performance of large-format
Altec Lansing drivers and horns. A similar one for the smaller horns
can be found as TL # 220.
TL-204
= Altec Rotary Attenuators
TL-205
= High Frequency Driver Protection Capacitor For Biamplified Sound
Systems - Written by Paul Spranger, this is another excellent
article for those who design or install professional sound systems.
TL-206
= 1588B Gain And Overload Characteristics
TL-207
= Useful Directivity Data For Reverberant Sound Fields -
Altec's Chief Engineer in Acoustics, Bob Beavers, gives valuable
directivity information on famous Altec horns, including the 811B,
511B, 311's, and multicellular models. If you use these horns, this
will interest and hep you!
TL-207
= A More Accurate Way Of Calculating Critical Distance -
Here's Don Davis again - pushing the envelope in an MUST READ Technical
Letter!
TL-208
= Architectural Uses Of The Critical Distance Concept -
More from Don. Another essential paper for all sound system designers,
users, and operators! Published February, 1972.
TL-210
= Calculating Percentages, Pages 1 & 2 -
EXCELLENT materials on how to conduct your sound contracting business
in a more business-like manner. Pages 1 & 2.
TL-210
= Calculating Percentages, Pages 3 & 4 -
EXCELLENT materials on how to conduct your sound contracting business
in a more business-like manner. Pages 3 & 4.
TL-210
= Calculating Percentages, Pages 5 & 6 -
EXCELLENT materials on how to conduct your sound contracting business
in a more business-like manner. Pages 5 & 6.
TL-210
= Calculating Percentages, Pages 7 & 8 -
EXCELLENT materials on how to conduct your sound contracting business
in a more business-like manner. Pages 7 & 8.
TL-211
= Notes On Loudspeaker Directivity - One of the most ignored
and misunderstood concepts in the sound system design world today is
that of loudspeaker directivity. In this TL, Don Davis again shows why
he is so well able to communicate these important concepts in an
understandable manner. DON'T MISS READING THIS ONE!
TL-212A
= Useful Equations For The Sound Contractor - A basic primer
on the equations that every sound system designer USED to know how to
use when designing a system. If every acoustical consultant, system
designer, and sound contractor would learn and use them again, the
quality of the systems being designed and installed would improve
tenfold!
TL-213
= Using The General Radio 1564 Analyzer To Measure THD
TL-214
= Time Delay Calculations - Any sound contractor who has
tried to set a digitally delayed loudspeaker systems needs to read this!
TL-217
= Using Altec Line Transformers and Autotransformers With European
100-volt Speaker Distribution Systems
TL-218
= Acoustic Attenuation With Increasing Distance - Here's a
great TL by Don Davis that will help ANY sound system designer,
installer, or user! It's amazing how much has been forgotten...
TL-219
= Improving The 1605A NOALA For Operation Under Adverse Noise Conditions
- Altec's Bob Bird, a true genius in electronic design and application,
developed the first properly operating automatic level control for
paging systems called NOALA -
"Noise-Operated-Automatic-Level-Adjustment". The NOALA worked so well
that many are still in operation all over the world. Only the advent of
digitally-controlled sound processing e equipment made it possible to
improve upon his design.
TL-220
= Measurement Of Nominal Sensitivity Ratings For Horn-Driver
Combinations Commonly Used In Monitor And Playback Systems -
Similar to TL #203, which deals with the larger AL horns, this is an
interesting data on the smaller Altec horns.
TL-221
= Directivity of Altec Loudspeakers - Mark Engebretsen's excellent
paper on loudspeaker Q verses frequency.
TL-222
= Application Of Telecommunication Products To Commercial Sound Use
TL-223
= Altec Horn-Driver Sensitivity Ratings In Metric Units -
Some very helpful information for those who still use the Metric system
of measurement.
TL-224
= Examples Of Simplexing For The Sound Contractor
TL-225
= Modifying The 9860A Active Equalizer For Low-Level Signal Applications
TL-226
= Measuring Loudspeaker Impedance By The Constant-Current Method
TL-227A
= Notes On Noise Masking/Speech Privacy Systems -
Interesting TL by Richard Forbes and John Eargle (before he went over
the the dark - orange - side)...
TL-228
= Understanding And Using Hybrid Circuits
TL-229
= Control Of Feedback In Systems With The White Model 3900 Narrow-Band
Filter Set - A GREAT primer on system equalization!
TL-230
= Application Of Component Loudspeaker Power Capacity Ratings To The
Design Of Two-Way Systems - Mark Engebretsen's EXCELLENT
Technical Letter on how to determine the manner in which a loudspeaker
will perform without failing, rather than merely rely on a
manufacturer's spec sheet.
TL-231
= Three New Compression Drivers
- Mark Engebretsen and Bill Hayes introduce Altec's 288-8G (there's a
nice chart comparing it's performance to the JBL 2440), the 291-16B,
and the 290-4G.
TL-232A
= Equalization Techniques And Practices - Our long-time
friend Ted Uzzle wrote this sterling paper on the proper use of
equalizers in live sound reinforcement systems. A MUST READ!
TL-236
= Control Of Radio Frequency Interference In Sound Systems -
Paul Spranger wrote these instructions for controlling RFI in sound
systems - another MUST READ for system installers!
TL-237
= Directivity Response Of Single Direct-Radiator Loudspeakers In
Enclosures - Clifford Henrickson authored this exceptional
paper on a incredibly misunderstood topic.
TL-241
= Applications For The Altec Lansing MANTARAY® Constant Directivity
Horns - Our friend Chris Foreman wrote this helpful
and practical paper on how to use the BEST constant directivity horns
ever designed or built to date - the Altec MANTARAY's!
TL-242
= Applications For The Altec Lansing 1690 Mixing Console
- Here's Chris Foreman with a TL on how to use one of the nicer
mixers that Altec made - the 1690.
TL-255
= Coverage Of Altec Lansing Loudspeakers - Ted Uzzle's
expertise in making the complex understandable and usable is easily
seen in this, the FIRST application of modern computer-assisted
loudspeaker coverage and system design techniques. Still a valuable
tool for understanding how loudspeakers work, it is a valuable addition
to the knowledge of sound system designers everywhere. June, 1981.
TL-257A
= Sound Distribution On A Plane Normal To A Loudspeaker Axis
- Rex Sinclair authored this paper on designing distributed loudspeaker
systems. Very nicely done!
TL-258B
= Uniformity Of Coverage In Distributed Sound Systems - Rex
Sinclair again enlightens us on this important and often misunderstood
topic.
TL-262
= Coverage Of Multiple MANTARAY® Horns - Our
friends Mark Ureda and Ted Uzzle teamed up to write a paper whose
concepts are still not understood by most modern acoustical
consultants, sound system designers, and sound contractors - how to
cover large areas with multiple horns while minimizing phase
interference, and maintaining apparent apex. Another MUST READ!
TL-263
= Modifying The Altec 2204 Power Amplifier For 16-ohm or 70.7-volt
Operation - Again, Ted Uzzle's years of cinema work shine
through as he describes how to get the most out of a wonderful
amplifier, the Altec 2204.
TL-264A
= Using Thiele-Small Parameters - Rex Sinclair wrote this
outstanding paper on how to use Thiele-Small parameters to design
loudspeaker systems. Every loudspeaker designer should read this one!
TL-266
= Articulation Loss In Consonants For Distributed Sound Systems
- Rex Sinclair's expertise with distributed sound systems shows up
again
in this often ignored design topic.
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© Altec Corporation
Copyright © 2002 by Todd W. White.
A
SPECIAL THANKS TO ANDY ANDERSON OF AUDIO-TECH IN ATLANTA FOR MANY OF
THE SCANS WE HAVE HERE!
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