AudioControl Richter Scale III Owner's Enjoyment Manual

Series Three

Owners Enjoyment Manual

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for those who consider perfection possible

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Owner’s Enjoyment Manual

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Dealer ____________________________________

Date Purchased ______________________________

Serial Number ______________________________

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TABLE OF CONTENTS

Making Everything Equal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Speaker placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Acoustic environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Equalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Analyzing your system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Appendices

A. Why Equalize? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

B. Room Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

C. Building Crossover Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

D. Bridging your Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

What To Do If You Need Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Congratulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

A Guided Tour Of The Richter Scale

Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Installation

Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Connection tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Getting It All Hooked Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Basic Hookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Surround Separates System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

A/V Receiver System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Electronic Crossover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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Congratulations

Your new equalizer is made by the only consumer elec­tronics company in the world that specializes in equalizers,
signal processors and audio analyzers. AudioControl’s
passion for high quality, meticulous attention to detail and
professional sound heritage shows itself in the dozens of
awards we have won for our designs, products and service.

This manual is designed to help you get the most from your
new component. So, even though you’re dying to try it out,
please take a few minutes to glance over this rhetoric and learn
about the Richter Scale/crossover. Anything that has this
many functions deserves all the explanation it can get.

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Features

Lab-Grade Audio Analyzer

Knowing where your frequency response problems exist is
half the battle of setting up a good sounding system. The
warble-tone signal generator and precision relative sound
level meter built into the Richter Scale provide an impartial
judge of the peaks, dips and speaker/room interactions. The
measurement microphone included with the Richter Scale is
lab grade and flat within 1 dB. The warble-tone generator
and sound level meter combine to create a very powerful
audio analysis tool.

Sharp Subsonic Filter for Speaker Protection

Now for a moment of realism...In spite of the great claims
made in the sales literature, a subwoofer can only play so low.
Trying to force a sub to run lower than is realistic will result
in wasted amplifier power, overheated speakers, distortion,
and worst of all, possible speaker failure. An 18dB per octave,
Tchebychev alignment highpass filter provides accurate low­frequency bass protection for your speakers without cutting
into audible bass performance. You will have more clear,
tight bass than you thought possible from your stereo
system.

Audiophile-Quality Electronic Crossover

What good is it having a subwoofer to rattle the room if
you have a second-rate crossover driving it? Subwoofer
manufacturers are very good at designing speakers, but most
of them are fish out of water when it comes to creating an
electronic crossover. The Richter Scale Series Three includes
one of the best crossover topologies available: 24dB/octave,
Linkwitz-Riley alignment. The sharp roll-off of this design
makes certain the subwoofer only creates the low bass
frequencies for which it was intended. AudioControl makes
this crossover even more useful by providing plug-in pro­gramming modules to set the crossover frequency. This
allows precision matching of the crossover and your
subwoofer. The result is solid bass you have to feel to believe.

Precision Bass Equalizer

Problems in the bass frequencies will have an affect
through the entire audio system. Excessive energy caused by
standing waves will mask fine details in the high end. The six
bands on the Richter Scale control this critical bass region of

22.5 Hz to 125 Hz in one-half octave steps. The controls are
stereo ganged to ensure consistent adjustment of the left and
right channels for more solid bass performance.

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Rumble Reduction Filter

An exclusive AudioControl feature; the Rumble Reduction
filter cuts turntable rumble, reduces acoustic feedback. It
even reduces the thump that occurs if you lower the car­tridge too quickly onto a record.

Award-Winning Quality

The Richter Scale Series Three was designed and built in
the USA by AudioControl - An award winning manufacturer
of highest-quality audio components since 1977. These
products are backed up by a comprehensive FIVE year
warranty.

THE MOST IMPORTANT INSTRUCTION OF ALL:

Fill out the warranty card and mail it to us. Also, record the
serial number and put your sales receipt in a safe place. This
is very important in the unlikely event that your new unit
gets a sudden virus, or for proof of ownership if somebody
takes a liking to your theater system in the middle of the
night. Insurance companies have no sense of imagination
when it comes to things like the Richter Scale ever being in
your system.

This concludes the nagging section of this manual.

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Front panel highlights

tone generator provides a precise reference to measure your
room against.

3. Analyze Switch - When pressed in, this button
activates the warble tone generator and switches the Main
Receiver / Preamp inputs over to the internal warble tone
source.

1. Relative SPL Meter - A precision sound level meter
to use along with the warble test tone to accurately measure
your speaker and room acoustics. The meter is damped in
order to average out variations in the warble tone and
decrease extraneous transient sounds during testing.

2. Warble Tone Generator - The other half of the
audio analysis system built into the Richter Scale. This test

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4. Equalizer Switch - This allows simple before and
after comparisons of the system equalization. When pressed
in, this button activates the half-octave equalizer circuitry.

5. One-half Octave Bass Equalizer - This six band
bass equalizer gives you incredible control over the critical
low frequency region of your room and speakers. The sliders
are stereo-ganged so you can accurately adjust both channels
at the same time.

6. Subsonic (Highpass) Filter Switch - Press this
button to get rid of power robbing, distortion inducing
infrasonics. This sharp 18dB per octave filter cuts off bass
frequencies below 18Hz to protect your system against these
audio demons. The Richter Scale utilizes a sophisticated, 3­pole Tchebychev alignment design does away with subsonic
interference without any audible side effects. Almost every
stereo will benefit from this filter, so don’t be afraid to leave
it on.

7. Rumble Reduction Filter Switch - This button is
dedicated to the good old days of analog vinyl sound and the
turntable. One press and say “good-bye” to turntable rumble

and acoustic feedback. It even reduces the thump you hear if
you lower the cartridge too quickly onto a record.

8. External Processor Loop Switch - Since the
equalizer section of the Richter Scale is usually connected
into the tape monitor loop of your preamp, we thought it
was only fair to give you one back. This button works the
same as the tape monitor on your receiver and switches the
Richter Scale input between the Main Input and the External
Processor Input.

9. Crossover Low Output Mute Switch - A quick
way to shut off your subwoofer and remind you why you
have one in the first place. This button mutes the low pass
output of the electronic crossover built into the Richter
Scale.

10. Crossover Low Output Level Adjustment -

A variable gain control to match the subwoofer volume to
the main speakers. This control is recessed because it should
only need to be set when the system is initially analyzed and
set up.

11. Power switch - Need we say more???

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Rear panel highlights

first publicized by Siegfried Linkwitz and Russell Riley, two
Hewlett-Packard engineers, in a 1976 Journal of the Audio
Engineering Society article. This crossover alignment offers
flat amplitude response with a steep roll-off rate and zero
phase difference (lobing error). The result is a clearer, more
accurate sound system.

4. Bridging Adapter Outputs - Bridging is a simple
means of getting more amplifier power for your subwoofer. It
combines the two channels of a stereo amplifier into a single

1. Power Cord - Plug this into the switched outlet of

your receiver or preamp.

2. Unswitched Convenience Outlet - What??? You’ve
run out of places to plug in your turntable or CD player. We
try to make things convenient. This outlet provides a simple
place to plug in your low power accessories and source units.

3. Independent Electronic Crossover - The ultra­accurate 24db per octave Linkwitz-Riley crossover is gener­ally regarded as the best crossover design available. It was

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mono amp of higher power. Refer to the appendix on
Bridging for more details.

5. External Processor Loop - These jacks replace the
tape monitor connections on your preamplifier. They are a
great place to connect other signal processors or a tape deck.

6. Main Receiver / Preamp Connections - These
RCA jacks connect the equalizer, filters and warble tone
generator to the outside world. The signal processing (EQs,
filters, etc.) are independent of the electronic crossover in the
Richter Scale, so both sections need to be connected to get
the full benefits of the Richter Scale.

7. Calibrated Microphone Input Jack - The Richter
Scale is supplied with a laboratory-grade, phantom power,
electret condenser measurement microphone. This mic is flat
within 1dB so very accurate sound analysis is possible. Do not
plug any other type of microphone into this jack or you may
damage the microphone or Richter Scale.

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SETTING UP THE RICHTER SCALE/
EQUALIZER CROSSOVER

Placement

The Richter Scale can be placed almost anywhere in your
audio stack. Make certain not to block the ventilation slots
on any component. Also, avoid placing the Richter Scale
directly over a large power amplifier. They can get pretty hot
and frequently have large magnetic hum fields from the
power transformer.

Power

A switched convenience outlet on the back of your
receiver or preamplifier is the best place to plug in the
Richter Scale. What? You already have a CD player plugged
into that socket? No sweat. That’s what the outlet on the
back of the Richter Scale is for. Plug the Richter Scale into the
receiver; then plug the disk player into the Richter Scale. A
disk player and the Richter Scale together don’t begin to
exceed the wattage rating for a switched outlet on a modern
receiver.

Connection Tips

If you’re a hi-fi veteran, this part may seem repetitive, but
some things can never be repeated too many times (just ask
our Customer Support Department)!

• Turn off all components before making any connections

and don’t stand in a bucket of water.

• When making connections, make sure that “Left goes to
Left” and “Right goes to Right”. The obvious and time­honored way to assure this is to assign RED plugs to Right and
WHITE/GREY/BLACK plugs to the left (yellow is usually a
video or digital signal cable).

• Whenever possible, keep power cords away from signal
cables (i.e., inputs from disk players, VCRs, etc.) to prevent
induced hum. Notice that we have placed the Richter Scale’s
power cord on the extreme left side. This helps you bundle all
power cords down one side of your stereo cabinet and all the
signal cables down the other.

• Use quality interconnect cables. We’re not going to get into
the debate about whether $100 interconnects improve the
sound of your system. We know from experience however that
really, REALLY cheap connections can cause problems. They
tend to disconnect inside, causing a hum or loss of signal.

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System examples

Surround Sound Separates System Using the Crossover

Connect
Main Output
to the
Crossover Input

Basic Hookup of Equalizer

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Surround

Preamp

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A/V Receiver System with mono subwoofer output

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Using The Electronic Crossover

Your search for better sound has led you down the path
towards electronic enlightenment. You are bi-amplifying
your stereo system. By allowing the amplifiers to concentrate
on narrower portion of the audio spectrum, you gain the
benefits of lower distortion, better intermodulation perfor­mance and more efficient system power handling. The
programmable electronic crossover in the Richter Scale Series
Three is a very flexible means of getting to your goal of
audio nirvana.

The ultra-accurate 24db per octave Linkwitz-Riley cross­over is generally regarded as one of the best crossover designs
available. It was first publicized by Siegfried Linkwitz and
Russell Riley, two Hewlett-Packard engineers, in a 1976
Journal of the Audio Engineering Society article. This
crossover alignment offers flat amplitude response with a
steep roll-off rate and zero phase difference (lobing error). The
result is a clearer, more accurate sound system.

Example Crossover Connection

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An important note to remember about the Richter Scale
Series Three: The Electronic Crossover is COMPLETELY
INDEPENDENT of the Equalizer and Warble Tone Ana­lyzer portions of the unit. If you want equalization and the
electronic crossover, you need to connect BOTH halves of
the Richter Scale.

The crossover circuitry features a very clean highpass
synthesis system to minimize the signal path of the high
frequency portion. Since the highpass output is derived
from the same filter used for the lowpass output; each half
of the output is always in perfect alignment. There is no
chance of a compo­nent going out of
tolerance and
misaligning the
crossover frequencies.

The crossover frequency of the Richter Scale Series Three is
programmed with a simple, plug-in resistor module. The
module installed from our factory is 90 Hz. Additional
modules are available from your dealer or from AudioCon­trol directly. There are further instructions in the appendix
about building your own resistor modules. Installing a new
module is a simple matter of removing the top cover of the
Richter Scale. Now unplug the existing module and replace it
with your new crossover frequency. The module is not
polarized; you can plug it in either way.

WARNING!

Make certain you unplug the AC power to

the unit before opening the chassis.

Hazardous voltages are present inside.

Inside view of Richter scale showing crossover module

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MAKING IT EQUAL ­GETTING YOUR SYSTEM IN ORDER

There are three main areas of adjustment when optimizing

a sound system. They are:

1. Placement of speakers.

2. The acoustic environment.

3. The system electronics.

Work on items 1 & 2 before fine tuning with the Richter
Scale. Here are some tips to get the most out of your speaker
placement and acoustic environment.

Speaker Placement

We (and every speaker manufacturer we’ve ever talked to)
can’t over-emphasize the importance of proper speaker
placement. Some speakers require very particular placement
in relation to the back and side walls; all speakers demand
careful placement in relation to your audio systems’ charac­teristics. Start by consulting the speaker’s owner’s manual
and don’t be afraid to experiment...a lot. Pull the speakers out
from the walls. Toe them in. Move them closer or further
apart. The variation in imaging and response that different

placement can make is astonishing. Especially with the
subwoofer.

The Acoustic Environment

Every room affects speakers differently. Reflective and
absorbent surfaces, room shape and volume, even placement
of furniture can significantly change a speaker’s sound. It is
very helpful while investigating various possibilities to use
the warble tone analyzer built into the Richter Scale.
Hint...Place the subwoofer in your listening position and
move the microphone around to different locations you are
thinking about placing the sub. Look for a location that has
the highest reading on the relative sound level meter.

Doing The Deed

The Equalization Process

An important fact to remember when equalizing a system
is that the human ear is much more sensitive to abrupt
changes in frequency response than to the overall curve. Your
ear is also more sensitive to having too much of something
than too little. With this in mind, try and make most of your
equalization changes by cutting frequencies, rather than
boosting them.

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Important Note: Not all subwoofers are created equal.
Be realistic about your expectation of them. The laws of
physics apply here: An 8" subwoofer cannot physically move
the volume of air of a 12" sub (large air movement = bass). Do
not apply large (greater than 6dB) boosts to the subwoofer
EQ bands on the Richter Scale unless you are certain your
subwoofer can handle it. Some so-called subwoofers can
realistically only put out solid bass down to 40Hz. Large bass
equalization boosts and a good digital source may overheat
or damage your subwoofer.

Analysis

Adjusting the speaker response in the last three octaves is
nearly impossible to do with just your naked ears. That’s
why we built a half-octave warble tone analyzer into the
Richter Scale. The warble tone center frequency is adjusted
with the Warble Frequency Knob. What is “Warble Tone”?
Basically, it is a rapidly sweeping sine wave tone of fixed
amplitude within specific frequency limits. Is it accurate?
Very!

Example curve - Subwoofer

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Example hookup with the Richter Scale

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To use the Richter Scale analyzer, you will need to connect
the Main Receiver / Preamp jacks on the rear of the Richter
Scale to your stereo system. The Warble Tone generator has
no internal connections to the crossover, so you will not hear
the test tone using only the crossover.

What is a Real-Time Analyzer (RTA)?

A real-time audio analyzer is a test tool that allows you
to graphically view the frequency response of a room.
Unlike the bouncing lightshow seen on some inexpensive
components, an RTA gives you some very useful informa­tion. The real-time audio analyzer consists of four main
parts: 1) The test signal generator (pink noise) to play
through the speakers, 2) A reference microphone to listen
to the sound coming back from the speakers, 3) Bandpass
filters to break up the audio spectrum into several smaller
sections, and 4) A display (similar to the VU meters on
your tape deck) that displays the volume level in each of
the frequency bands. The curve shown on the display is
the actual frequency response of the sound coming in
through the microphone.

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Start with the microphone for the analyzer in your main
listening position. It’s a good idea to also take some measure­ments at other locations near the main seat. Standing waves
in the room will make very narrow areas of high and low
bass level at the resonance frequencies. If you have the mic in
one of those peaks or nulls, you won’t have a real picture of
the room response.

Now that you have the Richter Scale connected and the

microphone in place, it’s time to do the deed:

1. Set all the equalizer sliders on the Richter Scale to the
center “0” position.

2. Plug the measurement microphone into the mic jack on
the rear of the Richter Scale.

3. Press “In” the Equalize and the Analyze buttons.

4. Set the Warble Tone Frequency knob to 250 Hz.

5. Adjust your system’s volume control until the Relative
Sound Level Meter on the Richter Scale reads 0dB.

6. Adjust the Warble Tone Frequency knob to 60 Hz.

7. IMPORTANT NOTE: If you don’t have the output of the
Richter Scale going to your main speakers as well as the
subwoofer, SKIP TO STEP

8. Adjust the Low Frequency Output level on the Richter
Scale to get the Relative Sound Level Meter back to 0 dB.

9. Set the Warble Tone Frequency knob to 125 Hz.

Example microphone placement

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10. Adjust the 125 Hz equalizer slider on the Richter Scale
until the Relative Sound Level Meter is reading 0 dB. If you
are boosting any of the equalizer sliders, listen for any
signs of woofer overdrive (distortion, flames, ripping cones
or howling dogs on the next block).

11. Repeat steps 8-9 for the remainder of the slider frequen

cies.

12. Since each equalizer band interacts with the adjacent

bands, repeat steps 8-9 again on all the eq bands from 125
Hz down to 22.5 Hz. Very few woofers can put out a “flat”
response, but try to get less than 2 dB variation from one
equalizer band to the next.

13. Congratulations! You’re done. Now you can listen to the

fruits of your efforts.

APPENDIX A ­Why Equalize?

1. Your receiver is insulting your intelligence. Manufacturers
think that more than two knobs (Bass & Treble) will
confuse you, so they deny you the ability to bring out the
best in your system.

2. Your room is special. Everyone’s is. Speakers have to be
designed to compromise for a wide range of listening
environments. An equalizer can compensate for overly
reflective or absorptive surfaces and help speakers perform
their best.

3. Your speakers can do better. Everyone’s can. An equalizer
can help deepen the bass, smooth the midrange and
extend high end frequency response. After buying a good
equalizer, many audio lovers say it’s like getting a new set
of twice-as-expensive speakers. But for a lot less.

4. The source material isn’t perfect. Did you know that bass is
actually removed from many recordings so they sound
good on smaller systems or over the radio? Used properly,
an equalizer can clean up many of these problems with
the flick of a slider.

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5. There’s a company that specializes in ‘Making good
stereo sound better’. AudioControl has been designing and
building the highest quality equalizers and sound processors
since 1977. Nobody else has put that much research and
effort into the art of equalization.

APPENDIX B ­Room Acoustics

In the real world, every residential space is acoustically bad
in some way. The only acoustically “perfect” rooms are
anechoic test chambers; and unless you’re very, very weird, it
unlikely you will be working in such a space.

How Sound Works

To understand the problem, let’s first review how sound
works and the effects of a room on sound waves. The human
hear perceives sound because it is responding to both the
vibrations of the air and pressure waves produced by sound
waves. We response to the vibrations, detect it as frequency
and then respond to the pressure and detect it as level or
intensity.

All sound producing devices produce a series of ‘waves’ in
the air, water, steel or anything but a vacuum. Remember, in
space, no one can hear you scream.

A Rooms Effect On Sound Waves

As shown here, sound waves react with every surface,
barrier or boundary they encounter. There are only two
possible reactions: Reflection or Absorption. If the energy
contained in the waves is absorbed it will be converted into
another form of energy - usually heat. Surfaces that are
absorptive, such as fiberglass, draperies or curtains, reduce the
amount of energy in the system.

Surfaces that reflect or refract the energy waves will
produce a series of ‘counter waves’ of energy. There are
always multiple reflections, at differing angles, in every
reflective situation.

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Whether a surface is absorptive or reflective will vary
greatly with frequency also. A suspended ceiling or a win­dow will have great affects on higher frequency, but they are
almost completely transparent to the lower bass frequencies.
As a general rule; the more mass in a surface, the better it will
reflect low frequencies.

For our purposes, we are only concerned with those
reflective waves that can product energy peaks and dips in
the perceived frequency response of the sound system in the
room.

Remember, that despite what you may have read or have
been told elsewhere...All rooms are bad in some way. All
rooms have audio compromises.

Room Modes and Wavelengths

Room resonances (or standing waves / modes) are one of
the most significant problems affecting perceived sound
quality and loudspeaker spectral presentation. These reso­nances are caused by reflected energy bouncing around the
room from the various surfaces (walls, floor, ceiling). Every
room will have length, width and height standing wave

modes. The question we need to answer is - How bad and
where will the problems produced by these reflections be?

Let’s Do A Little Math

No groaning please, it’s just simple division.

f = Speed of sound ÷ (2 x Length)

‘f’ is the standing wave mode frequency

1130 feet per second is the speed of sound (at room tem-

perature)

For example, if the room is 15 feet long, the math is:

f = 1130 ÷ (2 x 15)

f = 37.66 Hz

So the primary resonance frequency (standing wave mode)
along the length of the room will be at 37.66 Hz. There will
also be additional modes at multiples of this frequency
(75.32, 112.98, 150.64 Hz). Where a room causes real problems
is when the dimensions of the room (height, length, width)
are even multiples of each other. This causes standing wave
modes in several directions to occur at the same frequencies.

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APPENDIX C ­Building Your Own
Crossover Modules

An electronic crossover divides your music into two or
more frequency bands. Since speakers can only be designed
to accurately reproduce a limited range of frequencies, a
crossover must be used to send the appropriate information
to each speaker.

The correct selection of crossover frequencies greatly
depends on your choice of a subwoofer. Please check with
the subwoofer manufacturer for their recommendation
regarding a good crossover point.

The Richter Scale comes with a programmable 24dB/
octave Linkwitz-Riley crossover. It is preset at the factory at
90Hz. This frequency is easily be changed by removing the
top of your unit and replacing the existing resistor module in
the socket. New modules are available either from your
authorized AudioControl dealer or directly from our factory.
If you are feeling adventurous and are handy with a solder­ing iron, you can easily make your own resistor modules.
Here’s how...

To calculate the proper resistor value for the custom

module, use the following formula:

7200

Frequency (Hz) = Resistor value (kilohms)

For example, if you need a crossover point of 150Hz:

7200 ÷ 150Hz = 48 kilohms

For a 24dB/octave crossover module, you need eight
resistors and a 16 pin DIP component header. The resistors
used to build the module should be 1/4 watt, 1% tolerance,
metal film.

NOTE: If you would like more information about building
crossover modules, check out Technical Note# 1005 - Building
Crossover modules at www.audiocontrol.com

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APPENDIX D -

Bridging your amplifier

One more feature built into the Richter Scale Series Three is
a set of outputs on the crossover that allow you to combine
the channels of a stereo amplifier into a single mono amp.
This concept will work on almost any amplifier not already

equipped with bridged outputs
(i.e. amps without common
speaker output grounds). Check
your amplifier’s owners manual
or get out the handy multim­eter to verify if the amp meets
these conditions.

In the bridged mode, each channel of the amplifier sees
half of the load impedance (i.e. 2 ohms versus 4 ohms). The
amp outputs one channel in-phase with the system and the
other channel 180 degrees out of phase. This allows one
channel to provide the positive half of the signal and the
other channel to provide the negative. The voltages are
summed at the subwoofer for a theatrical fourfold increase
in power, as demonstrated by the following calculations:

The formula for output power of an amplifier (single
channel) is:

(Peak Voltage x 0.707)

2

÷ Load Impedance (Ohms) = Output

Power (Watts)

For a normal amplifier (rated at 25 watts per channel)
driving a nominal 4 ohm load, the output power is:

(14 volts x 0.707)2÷4 Ohms) = 24.49 Watts

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For a bridged amplifier (rated at 25 watts per channel)
driving a nominal 4 ohms load, the voltage is doubled and
the output power is quadrupled:

(28 volts x 0.707)2÷4 Ohms) = 97.97 Watts

As this example illustrates, a 25 watt amplifier can provide
100 watts of power in the bridged mode, for a noticeable
increase in bass performance.

CAUTION - Limitations in the amplifier

power supply and heatsink dissipation

will always reduce the available power.

Therefore, the realized power output
increases will generally be less than four times the
amplifier’s power output.

Although bridging is the best way to maximize bass
output, check the amplifiers manual to make sure if it is
capable of driving a 2 ohm load, and that it is not
already bridged internally.

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and now a word from our legal department...

The WARRANTY

People are scared of warranties. Lots of fine print. Months
of waiting around. Well, fear no more. This warranty is
designed to make you rave about us to your friends. It’s a
warranty that looks out for you and helps you resist the
temptation to have your friend, who’s “good with electron­ics”, try to repair your AudioControl product. So go ahead,
read this warranty, then take a few days to enjoy your new
Richter Scale before sending in the warranty card and
comments.

“Conditional” doesn’t mean anything ominous. The
Federal Trade Commission tells all manufacturers to use the
term to indicate that certain conditions have to be met
before they’ll honor the warranty. If you meet all of these
conditions, we will warrant all materials and workmanship
on the Richter Scale for five (5) years from the date you
bought it, and we will fix or replace it, at our option,
during that time.

Here are the conditional conditions:

1. You have to fill out the warranty card and send it to us

within 15 days after purchasing the Richter Scale.

2. You must keep your sales receipt for proof of purchase
showing when and from whom the unit was bought. We’re
not the only ones who require this, so it’s a good habit to get
into with any major purchase.

3. The Richter Scale must have originally been purchased
from an authorized AudioControl dealer. You do not have to
be the original owner, but you do need a copy of the original
sales slip.

4. You cannot let anybody who isn’t: (A) the AudioControl
factory or (B) Somebody authorized in writing by AudioCon­trol to service the Richter Scale. If anyone other than (A) or
(B) messes with the Richter Scale, that voids your warranty.

5. The warranty is also void if the serial number is

altered or removed, or if the Richter Scale has been used

improperly. Now that sounds like a big
loophole, but here is all we mean by it:

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Unwarranted abuse is: (A) physical damage (don’t use the
Richter Scale to level your projection TV); (B) improper
connections (120 volts into the RCA jacks can fry the poor
thing); (C) sadistic things. This is the best product we know
how to build, but if you strap it to the front bumper of your
Range Rover, something might break.

Assuming you conform to 1 through 5, and it really isn’t all
that hard to do, we get the option of fixing your old unit or
replacing it with a new one.

Legalese Section

This is the only warranty given by AudioControl. This
warranty gives you specific legal rights that vary from state
to state. Promises of how well the Richter Scale will perform
are not implied by this warranty. Other than what we have
covered in this warranty, we have no obligation, express or
implied. Also, we will not be obligated for direct or indirect
consequential damage to your system caused by hooking up
the AudioControl Richter Scale.

Failure to send in a properly completed warranty card
negates any service claims.

What to do if you need service

First, contact AudioControl, either by phone [phone],
email at [e-mail] or FAX [phone].
We’ll verify if there is anything wrong that you can fix
yourself, or arrange to have it sent back to our factory for
repair. Please include the following items with the returning
unit:

1) A copy of your proof of purchase (that sales receipt we’ve
been harping about). No originals please. We cannot guaran­tee returning them to you.

2) A brief explanation of the trouble you are having with
the Richter Scale. (You’d be surprised how many people
forget this.)

3) A return street address. (No PO Boxes, please)

4) A daytime phone number in case our tech has a ques­tion about the problem you are having.

You’re responsible for the freight charges to us, but we’ll
pay the return freight back. We match whatever shipping
method you send it to us, so if you return the unit overnight
freight, we send it back overnight. We recommend UPS for
any shipments.

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Block diagram

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Response Graphs

Equalizer
Full Boost and Cut

Crossover
(Factory 90 Hz Module Installed)

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Specifications

Number of channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Frequency response . . . . . . . . . . . . . . . . . . . . . . 18 Hz -100 kHz ±1dB

Total harmonic distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.005%

Signal to Noise ratio (at full output) . . . . . . . . . . . . . . . . . . . . 120 dB

Equalizer Filter “Q” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Input Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 kilohms

Output Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 ohms

Maximum output level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V

rms

Low Output Level Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 dB

Electronic crossover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . 24 dB/Octave Linkwitz-Riley alignment

Crossover Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . Programmable (90 Hz Factory setting)

. . . . . . . . . . . . . . . . (Additional frequency modules are available)

Subsonic Filter . . 18 Hz, 18dB/Octave Tchebychev Alignment

Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5" H x 17" W x 8.25" D

Power draw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Watts

Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 lbs

Options . . . . . . . . . . . 19" Rack mounting brackets (1.5U Height)

©1986-2001 AudioControl, All Rights Reserved

AudioControl is a division of Electronic Engineering and

Manufacturing, Inc.

AudioControl and Making Good Stereo Sound Better are
registered trademarks of Electronic Engineering and Manu­facturing, Inc.

This manual was written, designed, and printed while
fighting a life-and-death struggle with giant banana slugs
and drinking a double-grandé, vanilla latté.

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For Those Who Consider Perfection Possible

tm

22410 70th Avenue West

Mountlake Terrace, WA 98043 USA

Phone [phone] • Fax [phone]

Email: [e-mail] • Internet: www.audiocontrol.com