Audio Control AEQ-26 User manual

®making good stereo sound better®
22410 70th Avenue West • Mountlake Terrace, WA 98043 • Phone [phone] • Fax [phone]
www.audiocontrol.com
AEQ-26TM
Architectural Equalizer
®
Installation Manual
and Consciousness Guide

AEQAEQ
AEQAEQ
AEQ-26 Architectural Equalizer-26 Architectural Equalizer
-26 Architectural Equalizer-26 Architectural Equalizer
-26 Architectural Equalizer
Contents
CONGRATULATIONS! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Quick Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
A Guided Tour Of The AEQ-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Installation: The Long Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Hooking Up Your System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Audio Hook-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Doing The Deed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 9
A Short Introduction To Equalizers And Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Information For Control Freaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
A Brazen Plug For Other AudioControl Products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Appendix A - Building Your Own PFM Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 16
The WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 17
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

CONGRATULATIONS!
You are now installing a component that will dramati-
cally improve the performance of any multi-zone audio
system, especially those utilizing in-wall speakers. The
AEQ-26 is an American-designed, American-built “set and
forget” component which will provide a lifetime of trouble-
free service.
The new AEQ-26 is made by the only electronics com-
pany in the world that specializes in equalizers, signal
processors and audio analyzers. And the company whose
professional sound division sells the most popular one-third
octave real time analyzer in the world, the SA-3050.
AudioControl’s passion for high quality, meticulous atten-
tion to detail and pro sound heritage shows itself in the
dozens of awards we have won for our designs, products and
service. Now, as when we began, our greatest satisfaction is
our reputation for sonic excellence and reliability among
people just like you throughout the world.
This manual is designed to help you get everything you
can out of this new architectural equalizer. So, even though
you’re dying to see it in action, please take a few minutes to
slog through our not-so-weighty prose and learn how to get
the most from your new AEQ-26.
1

only those frequencies they can use by “chopping off” bass
below an installer programmed frequency (40Hz is the
factory setting). The woofer is protected and can do a better
job of reproducing mid-bass and higher frequencies. It also
helps keep the speakers in one piece when the teenagers get
control of the stereo.
Made in the Northwest Rainforest - The AEQ-26
began its existence at our factory in Mountlake Terrace,
Washington, a few miles north of Seattle. Here, we also build
precision test instruments, home audio equalizers and
analyzers and a totally awesome line of car stereo compo-
nents. AudioControl began in 1977 and has won so many
audio industry awards for design and engineering excellence
that our reception room wall is starting to sag. But enough
about us. Let’s start getting the most from your audio system!
The AEQ-26 Product Highlights
Specially Designed Frequency Controls - The
AEQ-26 is engineered to provide a dramatic sound improve-
ment for “small” speakers, such as those with 8-inch or
smaller woofers. The AEQ-26’s 45Hz, 150Hz, 300Hz, 700Hz,
2500Hz and 12kHz band centers were chosen to optimize in-
wall and small 2-way box speakers at critical frequencies
where adjustment is most advantageous. The bandwidths (or
‘Q’ as our engineering types call it) have also been optimized
for the difficulties that in-wall speakers present. This allows
the AEQ-26 to improve the sound of these smaller speakers
better than any other equalizer.
Programmable PFM Bass-cut Filter - The AEQ-26’s
programmable bass-cut circuitry is an installer adjustable
low frequency blocking filter which protects small speakers
from too much low end and improves their overall sound.
The smaller woofers found in most in-wall or bookshelf
speakers cannot reproduce the bass of a larger speaker (the
laws of physics intervene). If called upon to reproduce a bass
note that would cause the speaker to move PAST its maxi-
mum cone travel, damage can result - and even if it doesn’t,
severe audible distortion DOES. The solution is
AudioControl’s exclusive PFM circuit. It gives small woofers
2

Experienced Installers Quick Hook-Up Guide
What follows are “Express” hook-up diagrams for profes-
sionals and experienced audio buffs.
Make sure to fill out and mail the warranty card.
The PFM filter module comes factory set at 40Hz. See
page 15 for details on changing the PFM module. A complete
range of frequencies is available from the factory and
information is also available on building your own modules
in Appendix A. Modules are also available from any Audio-
Control car stereo dealer in a pinch.
Final adjustment of The AEQ-26’s boost/cut controls in
each zone is best done with a one-third octave real time
analyzer and pink noise test signal, but it can also be done by
ear, especially if you desire to emphasize certain frequencies.
3

Multi-amp / Zone System
4

2) if (assuming the speakers aren’t built in) you move them
significantly, such as from a bookshelf to floor stands, or
3) if your room acoustics change through addition or
rearrangement of furniture, wall or floor coverings, large
hairy dogs, or other sound reflective or absorptive sur-
faces.
3. Bypass Switch - This switch allows you to bypass the
equalization controls on the AEQ-26. When the button is
in the OUT position, the equalizer is defeated.
A Guided Tour Of The AEQ-26
Front panel:
1. Power LED - Nothing too tricky here. . . if you have the
Master Power switch (on the back panel) turned on and
the AEQ-26 is plugged into an active AC outlet, this little
red light will shine forth.
2. Speaker Optimization Controls - This gang of
knobs provide up to 12dB boost or cut at 45Hz, 150Hz,
300Hz, 700Hz, 2500Hz and 12kHz. After initial adjustment
the only time you would change the control settings are
1) if you connect different speakers into the system,
1. Power LED 2. Speaker Optimization Controls 3. Bypass Switch
5

Back panel:
1. Input - These unbalanced RCA inputs connect to your
control preamplifier’s outputs.
2. Output - This pair of jacks feed out into your power
amplifier.
3. AC Power Fuse - This power fuse is here just in case
something really awful goes wrong.
4. Accessory AC Outlet - This unswitched and unfused
outlet allows you plug in almost any other components
that draw less than 500 watts (CD, tuner, VCR, etc.).
1. Input 2. Output
3. Fuse
4. Outlet
5. Switch
6. Power
Cord
5. Master Power Switch - This switch shuts off the main
AC power. Normally the only time you need to turn off
the master power is if the homeowner is going to be gone
on vacation for a few weeks.
6. Power Cord - The AEQ-26 draws a scant 6 watts (about
the same as most clock radios). Don’t worry about
plugging several AEQ-26’s into a power strip.
6

7
Installation: The Long Version
What follows is a step-by-step guide to integrating the
AEQ-26 into your multi-zone system. If it seems overly
detailed, please forgive us. We would rather tell you too
much than too little.
First, check your new AEQ-26 for any shipping damage.
We pack ‘em pretty securely, but it’s a vicious world out
there and anything can happen between Mountlake Terrace,
Washington and your install site.
Paperwork
Yes, filling out the warranty registration card is about as
exciting as cleaning out your sock drawer, but we’d definitely
like the card back after you’ve hooked up the AEQ-26 and
played with it a while. We DO read each and every incoming
card and react to your suggestions. That’s how great products
like this are created.
Next, record the serial number on the sales receipt and
make certain the home owner puts it away in a safe place.
Stashing the receipt away is very important in the unlikely
event that your AEQ-26 ever needs servicing, or. . . well things
do happen. . . you sometimes need to prove to an insurance
adjuster that something as great as the AEQ-26 was installed
in the system.
Placement
The AEQ-26 is a not very particular about it’s location. As
with all electronic components, keep it away from any place
that is too hot or too wet. Just as a reminder, you should also
avoid putting any leaky potted plants in your stereo stack.
AC Power
Under normal operating conditions, the AEQ-26 only
draws 6 watts of AC power. Don’t worry about plugging
several of these units into a single AC outlet and ganging the
power through the convenience outlet on the rear of the
AEQ-26.

Hooking Up Your System
What youll need:
1. The AEQ-26.
2. RCA audio hook-up cables.
3. (Optional) A balanced line driver if you are going to
mount the AEQ-26 more than 20 feet from the preamp or
amplifiers.
4. Although you can set the speaker optimization controls
by ear, a real-time audio analyzer such as the
AudioControl SA-3052 is very helpful.
Audio hook-up
If you’re an installation veteran, this may seem repetitive,
but some things can never be repeated too many times (just
ask our Customer Support Department).
1. Turn off ALL components before making any connec-
tions.
2. When making connections, designate RED RCA plugs as
RIGHT and WHITE, BLACK, or GREY plugs as LEFT. In
fact, this is a good idea for ALL signal connections made
in your audio system. The key is consistency. Stick with
the same color-coding and you’ll reduce possible prob-
lems.
3. Whenever possible, keep power cords away from signal
cables to prevent induced hum. This is especially impor-
tant if you bundle the cables to keep the installation neat
looking.
4. Use quality interconnect cables. We’re not going to get
into the debate about whether $100/meter cables improve
the sound, but we know from experience that really,
REALLY cheap cables can cause a multitude of problems.
They tend to break inside or corrode, causing a loss of
signal or hum. They also have poor shielding.
8

5. If you need to run the RCA audio cables more than 20 feet
you should consider using a balanced line driver for the
signals. This will provide better noise rejection against
nasty things like hum, spikes, local talk radio, etc. Ask
your AudioControl representative for more information
about line drivers.
9
Doing The Deed
Before proceeding on to setting up the Speaker Optimiza-
tion controls on the AEQ-26, it’s a good idea to make sure
that you have everything connected and working properly.
1. Double-check all connections. Make certain that all of the
audio and speaker connections are firmly seated and
tightened down.
2. Turn on your audio system. The Power LED on the AEQ-26
should be on.
3. Continue checking to ensure that every zone plays
properly.
4. Congratulations! You’re ready to go on to setting the
Speaker Optimization controls.
You’re almost done! Now for the details of operation. . .

above. Since sound is energy, the way it reflects depends
upon the angle of the surface, the type of material and the
frequency of the sound wave. Because your listening posi-
tion is likely to be towards the back of the Free Field shown
in the diagram, you also get part of the reflected Reverberant
Field as well.
A Short Introduction To
Equalizers And Acoustics
Magazine reviewers and audio system owners spend
much time critically appraising speaker and other stereo
components. Unfortunately, a phenomenon that has a very
large effect upon sound is not is easily judged or changed.
That effect is the ACOUSTICS of the environment in which
you are listening.
Room acoustics is a complicated subject about which
entire textbooks have been written. We simply want you to
be aware of a few basics that have a direct effect on real time
audio analysis.
Sound is waves, as you probably learned in junior high
school. In a stereo system, these waves are created by the
speakers. Like waves in a pond created by a splash, sound
waves emanate from the transducers (drivers) in your
speakers and spread out into the room. If your room were
infinitely big, that’s all there would be to it. But just like
waves in a pond reach the bank and reflect back, sound
waves bounce off walls, ceilings, and floors, reflecting,
reinforcing and canceling each other as shown in the figure
10

Now we add the next set of complications: Different
frequencies of sound have different wave lengths (a function
of frequency and the speed of sound). Each frequency’s
wavelength contributes differently to the Free and Reverber-
ant Fields because they are different sizes. For example, a
32Hz bass note has a wavelength of 35 FEET, while a
16,000Hz note has a wavelength of just under a tenth of an
inch. Tiny treble waves can be caught and neutralized by
draperies, carpeting, upholstered furniture and gangs of
indolent Persian cats. . . while gigantic bass waves simply
slosh back and forth in the room.
Another set of variables is the shape and volume of your
listening room. Large rooms require more bass energy to
excite waves within them. Small rooms need less energy, but
reflect it differently. And then there’s the fact that most
rooms don’t have four walls anymore, but open into dining
rooms, lofts, cathedral ceilings, etc. All of this means that
predicting sound interaction patterns is very difficult due to
the irregularities of the room shape.
As you can see, room acoustics is an important but
complicated subject. (To learn more about room acoustics,
download AudioControl’s Technical Paper 107, “Small Room
Acoustics De-Mythologized” from our website.) The overall
point that we’re trying to make is that the various rooms in
your home function as gigantic mechanical equalizers,
boosting or cutting certain frequencies depending on size,
shape, volume, acoustic treatment and the position of the
speakers.
Audio Analysis Using Pink Noise
It may take several series of adjustments since there is
some interaction between each eq control. We have included
some sample settings and general descriptions of each
control’s function beginning on the next page.
After initial adjustment the only time you would change
the control settings are 1) if you connect different speakers
into the system, 2) if (assuming the speakers aren’t built in)
you move them significantly, such as from a bookshelf to
floor stands, or 3) if your room acoustics change through
rearrangement of furniture, wall or floor coverings, large
hairy dogs, etc.
The following are examples of typical settings along with
short descriptions of each AEQ-26 Speaker Optimizer control.
Naturally, the results of adjustments will vary depending on
the acoustic environment, type of speaker and sound sources
you are using, but this is a good starting point.
11

For an extensive description on the use for the SA-3052
real time spectrum analyzer for these settings, please see that
product’s manual.
Information For Control Freaks
Here is a brief introduction to each of the Speaker
Optimization control frequencies and what their effect on
your music is.
45Hz - Low bass. This is about the lowest frequency
which in-wall, extension and small bookshelf speakers can
achieve. Boosting it too far might cause problems, even
though The AEQ-26’s PFM filter cuts frequencies under 40Hz.
But if your speakers can take it, a mild boost will enhance
bass instruments such as Fender bass, kick drum, floor toms,
timpani and double bass violas.
150Hz - High bass. There’s a lot of bass information at
this frequency. In fact, most modern music is mixed to
enhance this area of the frequency spectrum. 150Hz also
determines the depth of male vocals and contains reverber-
ant information which contributes to the spaciousness of
sound. Boosting 150Hz can add “POW!” and impact to bass
or it can make the sound “bonky” and “boomy”. This is a
critical adjustment with small or in-wall speakers. Experi-
ment with it.
300Hz and 700Hz - High and low midrange. These
controls directly effect the sound of instruments and vocals.
12
Example Control Settings

These bands also determine the speaker’s presence (whether
the music sounds far away or close in). Small speakers often
produce too much midrange, so these controls are candidates
for being turned down slightly during your initial experimen-
tation. Definitely consider reducing 700Hz if you are only
using your extension speakers for background music.
2500Hz - Treble. Female vocals and the “edge” of instru-
ments such as guitars, snare drums, saxes, violins, etc. are
found in this range. If accentuated too much (by boosting
this control) sounds in the 2500Hz range can seem harsh and
fatiguing to the ear due to excessive output by the speaker or
because of live, reflective room acoustics.
12kHz - High treble. The fine detail, texture and sheen of
music is found here. The breathiness of vocals, the “sheen” of
cymbals, the high overtones of piano and strings. Actually,
there’s audible music information up to 20,000Hz on some
CD’s and most adult’s hearing is still pretty good at 15,000Hz.
But we’ve chosen 12,000Hz because it provides more useful
control to compensate for room acoustics and common small-
speaker deficiencies.
The Truth About Bass And The Programmable
Frequency Match Filter
Now that digital audio is the preferred musical source,
there’s more low bass running around in a typical system.
Low bass injects large amounts of power into ANY kind of
speaker - up to 60% of your amplifier’s output is being used
to reproduce frequencies under 100Hz. That can really tax a
system which is driving multiple speakers from a single
amplifier channel. The second problem is that bass produces
heat in the speaker. If more heat is built up than the speaker
can dissipate, the driver coil can literally go into meltdown
(or worse).
In addition, ultra-low bass and small speakers don’t
always get along, ESPECIALLY when you DO have ample
power. The low bass music content can cause over-excursion:
The speaker cone attempts to travel farther than its physical
limits, potentially causing damage (in some cases you can
actually hear a clacking sound!) Even before destruction sets
in, there are other problems with feeding super-low bass to
small speakers. Most bookshelf and in-wall loudspeakers are
2-way systems. That means that the woofer also handles a
large part of the critical midrange area. When the woofer is
bashing around trying to reproduce unrealistically low bass,
13

it’s ability to produce midrange is compromised due to
intermodulation distortion. So not only don’t you get low
bass, you get lousy vocal and instrumental reproduction.
Pragmatically, it boils down to this: If you want ultra-low,
foundation-shaking bass from an in-wall speaker, you should
add in a separate subwoofer, a somewhat expensive ap-
proach. A more economic approach is to equalize the speaker
for maximum low bass output WITHIN IT’S PRACTICAL
RANGE and eliminate lower frequencies which either can’t
be reproduced or which incite excessive cone travel.
The equalization part is handled by the AEQ-26’s 45Hz
control. The prevention part is handled by the AEQ-26’s
Programmable Frequency Match filter circuit. While it may
seem surprising, actually cutting off some of the lowest bass
will make the bass sound cleaner, punchier and even louder.
AudioControl’s Programmable Frequency Match circuit is
an adjustable subsonic filter which cuts off low frequencies.
The PFM filter’s cut-off point is adjustable via a small resistor
module inside the AEQ-26. When you receive your unit, it is
programmed with a 40Hz bass cut-off. Depending on the
application, you may want to change the filter frequency.
Don’t let ego get in the way and set the PFM too low because
14
somebody thinks that a 6" woofer should be able to play
down to 20Hz.
The following standard module frequencies are available
from AudioControl: 20, 25, 35, 40, 45, 50, 60, 70, 80, 90, 100,
120, 130, 150, 200, and several higher frequencies going up to
6000Hz which probably aren’t applicable except in very
special circumstances. Each module’s frequency is deter-
mined by 6 resistors inside a 14-pin DIP network. See Appen-
dix A for details on building your own modules.

Changing The PFM Module A Brazen Plug For Other
AudioControl Products
AudioControl started out making graphic equalizers in
1977. In a way, the AEQ-26 is an equalizer and, like our other
models, can make a greater improvement in the sound of
your system than almost any other addition or upgrade.
More bass, better bass, less harshness and the ability to hear
music the way you want it.
We make our equalizers easy to use by incorporating
features such as paired or ganged sliders, as well as subsonic
filters and, in some models, built-in test analyzers that let
you make accurate adjustments to instantly compensate for
main system speaker and room deficiencies. In fact, Audio-
Control was the world’s first manufacturer of a SEVEN
CHANNEL equalizer for home theater use.
We also make other enhancement devices so unique and
so dramatically enjoyable that we have received patents for
them as well as numerous industry awards. These, along with
our Multi-Room Controller and Balanced Line Driver,
provide a rich assortment of products to make certain that
your audio system sounds it’s best.
15
WARNING: Unplug the AEQ-26 from AC power
before beginning. There are dangerous voltages
present inside.
The first task in changing the PFM module is to remove
the top chassis of the AEQ-26. To do this, remove the 5 screws
on the top of the AEQ-26. The PFM module is indicated on
the circuit board (see figure).
Use a small screwdriver to gently pry the existing module
from it’s socket taking care not to bend the contact pins.
Now you can install the replacement module. There is NO
POLARITY to
these modules so
they can install
in either direc-
tion.
Now you can
put the top back
onto the AEQ-26
and go back to
enjoying your
music.

Okay, enough commercials.
Once again, we thank you for adding an AudioControl
component to your system and hope you enjoy a lifetime of
performance and convenience.
Appendix A -
Building Your Own PFM Modules
AudioControl PFM filters use resistor modules for fre-
quency programming. All modules are constructed in the
same way, with the exception of the actual value of the
resistors used. In each module, ALL resistor values are equal.
The resistor value for any given frequency is chosen accord-
ing to the following equation:
Resistor (kilohms) = 7200 ÷frequency (Hz)
Example: To find the resistors needed for 1000 Hz.
R (kilohms) = 7200 ÷1000
R (kilohms) = 7.2
R = 7.2 K = 7200 ohms
Building Modules
PFM modules require 6 resistors mounted on a 14-pin DIP
header. In the 14-pin modules, the middle resistor position is
unused and may be left unconnected. We recommend 5%
1/4watt carbon film resistors, or if you really want to be spot-
on, 1% metal-film resistors (difficult to get).
The DIP headers are available from most electronic parts
distributors.
It will make things easier if you buy a 14-pin IC socket as
well. You can chuck the socket in your vise and have a
handy fixture to hold the header while you solder.
Do not be confused by the modules from the factory that
do not show individual resistors.
They really are there, just
encased in plastic.
16

Frequencies by Resistor Value
Five-percent resistors are available in 24 standard values
per decade (this means that from 10 to 100 ohms, there are 24
values). The following table lists the crossover frequencies
that result from using these standard 5% values.
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 electron-
ics”, try to repair your AudioControl product. So go ahead,
read this warranty, then take a few days to enjoy the new
AEQ-26 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 AEQ-26 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 installing the AEQ-26.
2. You must keep your sales receipt for proof of purchase
showing when and from whom the unit was purchased.
We’re not the only ones who require this, so it’s a good habit
to get into with any major purchase.
17
Frequency Value
117 Hz 62 KΩ
106 Hz 68 KΩ
96 Hz 75 KΩ
88 Hz 82 KΩ
79 Hz 91 KΩ
72 Hz 100 KΩ
66 Hz 110 KΩ
60 Hz 120 KΩ
56 Hz 130 KΩ
Frequency Value
48 Hz 150 KΩ
45 Hz 160 KΩ
40 Hz 180 KΩ
36 Hz 200 KΩ
33 Hz 220 KΩ
30 Hz 240 KΩ
27 Hz 270 KΩ
24 Hz 300 KΩ
22 Hz 330 KΩ
20 Hz 360 KΩ
15 Hz 470 KΩ