Rane MX 22 User Manual

OPERATORS MANUAL MX 22

STEREO 2-WAY CROSSOVER

QUICK START

Whoa, hold on there. Even if you don’t read manuals as a matter of principle, at least read this section to avoid hurting

yourself or your equipment.

Connect the MX 22 with the power off. Balanced XLR cables are recommended, but if you must convert to ¼" connec-

tors, buy or make a cable like the ones on page Manual-11 and keep them as short as possible. This device uses low imped-

ance balanced line drivers. Do not connect the “+” or “–” output pins to ground, as this may cause the power supply to
shut down. For unbalanced use, leave the unused output pin (“+” or “–”) unterminated.

Consult the speaker manufacturer for the correct crossover FREQUENCY setting. As rugged as some drivers are, many
(especially compression drivers) will not accept frequencies outside of their normal range without producing distortion and
possibly self-destruction.

With all equipment turned off and LEVEL controls down, begin making connections to the system as shown on page
Manual-4 or 5. When turning on the system, switch on the power amplifiers last. Now, feed the MX 22 some program
material. Start by turning up the LOW LEVEL and HIGH LEVEL to the 0 dB marks. Slowly increase the INPUT
LEVEL, even if it goes all the way to 10, so the +4 dBu (green) light blinks occasionally and the OL (red) light stays out.
This delivers the best signal-to-noise performance.

The MONO SUB OUTPUT is a sum of the Left and Right Low Outputs. The MONO SUB LEVEL adjusts only this
Output and is not affected by the LOW LEVEL control.. When using a single subwoofer along with full-range cabinets
that have internal crossovers, set the 100 Hz FILTER to OUT, allowing the front panel FREQUENCY to control the
subwoofer crossover point. When used with biamp cabinets and a subwoofer, set the 100 Hz FILTER switch to IN to
allow only frequencies below 100 Hz at this output jack. This way, the MX 22 almost does the job of a Stereo 3-Way
crossover, but without removing that awesome bass from the Left and Right Low Outputs.

WEAR PARTS: This product contains no wear parts.

Manual-1

RISK OF ELECTRIC SHOCK

DO NOT OPEN

CAUTION

IMPORTANT SAFETY INSTRUCTIONS

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any ventilation openings. Install in accordance with manufacturer’s instructions.

8. Do not install near any heat sources such as radiators, registers, stoves, or other apparatus (including ampliers) that produce heat.

9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A ground­ing-type plug has two blades and a third grounding prong. e wide blade or third prong is provided for your safety. If the provided plug does not
t into your outlet, consult an electrician for replacement of the obsolete outlet.

10. Protect the power cord and plug from being walked on or pinched particularly at plugs, convenience receptacles, and the point where it exits from
the apparatus.

11. Only use attachments and accessories specied by Rane.

12. Use only with the cart, stand, tripod, bracket, or table specied by the manufacturer, or sold with the apparatus. When a cart is used, use caution
when moving the cart/apparatus combination to avoid injury from tip-over.

13. Unplug this apparatus during lightning storms or when unused for long periods of time.

14. Refer all servicing to qualied service personnel. Servicing is required when the apparatus has been damaged in any way, such as power supply
cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does
not operate normally, or has been dropped.

15. e plug on the power cord is the AC mains disconnect device and must remain readily operable. To completely disconnect this apparatus from
the AC mains, disconnect the power supply cord plug from the AC receptacle.

16. is apparatus shall be connected to a mains socket outlet with a protective earthing connection.

17. When permanently connected, an all-pole mains switch with a contact separation of at least 3 mm in each pole shall be incorporated in the electri­cal installation of the building.

18. If rackmounting, provide adequate ventilation. Equipment may be located above or below this apparatus, but some equipment (like large power
ampliers) may cause an unacceptable amount of hum or may generate too much heat and degrade the performance of this apparatus.

19. is apparatus may be installed in an industry standard equipment rack. Use screws through all mounting holes to provide the best support.

WARNING: To reduce the risk of re or electric shock, do not expose this apparatus to rain or moisture. Apparatus shall not be exposed to dripping

or splashing and no objects lled with liquids, such as vases, shall be placed on the apparatus.

NOTE: is equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. ese
limits are designed to provide reasonable protection against harmful interference in a residential installation. is equipment generates, uses and can
radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communica­tions. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning the equipment o and on, the user is encouraged to try to correct the interference
by one or more of the following measures:

• Reorient or relocate the receiving antenna.

• Increase the separation between the equipment and receiver.

• Connect the equipment into an outlet on a circuit dierent from that to which the receiver is connected.

• Consult the dealer or an experienced radio/TV technician for help.

CAU TION: Changes or modications not expressly approved by Rane Corporation could void the user's authority to operate the equipment.

is Class B digital apparatus complies with Canadian ICES-003.
Cet appareil numérique de la classe B est conforme à la norme NMB-003 du Canada.

WARNING

To reduce the risk of electrical shock, do not open the unit. No user
serviceable parts inside. Refer servicing to qualied service personnel.

e symbols shown below are internationally accepted symbols that warn
of potential hazards with electrical products.

is symbol indicates that a dangerous voltage
constituting a risk of electric shock is present within
this unit.

is symbol indicates that there are important
operating and maintenance instructions in the
literature accompanying this unit.

INPUT LEVEL control and
indicators

This controls the overall level without
altering the relative settings of the Low and
High frequency Outputs. Input gain is +6 dB
at “10”. With signal applied, set this control
so the +4 dBu LED lights occasionally,
indicating sufficient signal. Flashing of the
OL (overload) LED during peaks can be
avoided by turning the INPUT LEVEL down.

LOW LEVEL control

This controls the level of signal going to the
LOW OUTPUT jacks. Unity gain is reached at
the “0 dB” mark with the INPUT LEVEL set
to “10”. This control does not affect the
MONO SUB OUTPUT level. Refer to Operating
Instructions on page Manual-6.

MONO SUB OUTPUT,
LEVEL trim, and
100 Hz FILTER switch

HIGH OUTPUTS

These are balanced Output jacks. Connect
the LEFT HIGH OUTPUT to the left channel
input of the high frequency amplifier, and
the RIGHT HIGH OUTPUT to the right
channel input of the high frequency
amplifier. When using different model
amplifiers for the low and high outputs, use
the amplifier with the most power for the
low outputs.

This Output contains the summed signals of
the LEFT and RIGHT LOW OUTPUTS. It may
be used instead of, or along with the LOW
OUTPUTS. The output may be adjusted with
the LEVEL trim from +6 dB to -10 dB. Unity
Gain is straight up at 12:00. Switch the 100
Hz FILTER to IN when using a subwoofer
along with the LOW OUTPUTS. This sends
only the very lowest frequencies to the
subwoofer.

Manual-2

LOW/HIGH FREQUENCY control

HIGH LEVEL control

Power ON switch and LED

This 31-position selector sets the crossover
frequency between the Low and High
frequency Outputs in both Channels. Consult
the manuafacturer of the drivers or cabinets
for the correct setting.

LOW OUTPUTS

This controls the level of signal going to the
HIGH OUTPUT jacks. Unity gain is reached at
the “0 dB” mark with the INPUT LEVEL set
to “10”. Refer to Operating Instructions on
page Manual-6.

INPUTS

These are balanced Inputs. It is best to use

Your basic, straightforward power switch.
When the yellow LED is lit, the MX 22 is
ready to go.

Cable Wiring

In agreement with IEC and AES/ANSI
standards, Rane wiring convention is pin 2
Positive (hot), pin 3 Negative (cold or
return), and pin 1 signal grounded and
chassis grounded (to allow unbalanced

operation). The XLR case is chassis
Connect the LEFT LOW OUTPUT to the left
channel of the low frequency amplifier, and
the RIGHT LOW OUTPUT to the right channel
of the low amplifier. When driving a single
subwoofer, use the MONO SUB OUTPUT jack
instead.

balanced lines, especially when connecting
cables over 10 feet in length. If you are
feeding the MX 22 from a device that does
not have balanced XLR connectors, consult
SOUND SYSTEM INTERCONNECTION on page
Manual-10.

grounded.

balanced line drivers. Do not connect the

“+” or “–” output pins to ground, as this

may cause the power supply to shut down.

For unbalanced use, leave the unused output

pin (“+” or “–”) unterminated.

This device uses low impedance

Manual-3

APPLICATION — ACTIVE 2-WAY WITH (or without) MONO SUB

Manual-4

Use this configuration if you have separate speaker inputs for the low
and high drivers, regardless of whether they are in the same or
different cabinets.
Connect as shown for a mono subwoofer. Set the 100 Hz FILTER
switch to the IN position. If a mono subwoofer is not used, the
FILTER switch setting will not matter, since all low frequencies will
be sent to the LEFT and RIGHT LOW OUTPUTS.
The front panel LOW/HIGH FREQUENCY control determines the
frequency division between the low and high drivers, and only low
frequencies below 100 Hz will be sent to the mono subwoofer.

APPLICATION — PASSIVE 2-WAY WITH MONO SUB

PASSIVE 2-WAY WITH MONO SUB

Use this configuration if you have full-range cabinets with passive
crossovers built-in, i.e., no separate speaker inputs for the low and
high drivers.
Connect as shown for a mono subwoofer. Set the 100 Hz FILTER
switch to the OUT position. The front panel LOW/HIGH frequency
control determines the frequency division between the main cabinets
and the mono subwoofer.

Manual-5

OPERATING INSTRUCTIONS

Selecting Crossover Frequencies

Most speaker manufacturers supply low and/or high
frequency cut-off points for each driver, especially if these
are supplied in a system. These cut-off frequencies are based
on each driver’s performance, with a certain safety margin to
accommodate more gentle filter roll-offs.

The MX 22 utilizes a 31-position precision DC control
voltage potentiometer to select the LOW/HIGH FRE­QUENCY point. This crossover circuit design assures
consistent accuracy from Channel-to-Channel and unit-to­unit. This is a distinct advantage over continuously variable
designs using ganged potentiometers which can yield large
variations in channel-to-channel matching. Even with 31
choices it is possible that the exact recommended Crossover
Frequency may not fall on one of the detents on the selector.
Not to panic, for drivers have their own gradual rolloffs and
tolerance variations. Just pick the closest one. When in doubt,
choose the higher Frequency setting.

The illustration and table below details the crossover
frequencies available on the detents that are not labeled. For
best overall system results, try to choose the speaker compo­nents so that each operates well within its recommended
limits. This provides valuable leeway so that crossover points
may be adjusted in order to fine-tune the system. This also
yields higher system reliability. If at all possible, always use
some kind of realtime analyzer to tune your crossover, and
then fine-tune each system with an equalizer. Keep reading
for further alignment details.

Setting the Output Level Controls

The INPUT LEVEL is an overall system sensitivity
adjustment. Use this control to decrease the overall sensitivity
of the entire sound system, including the mono subwoofer if
you are using one. You will generally want to start with this
control in the full clockwise (or 10) position.

The LOW LEVEL, HIGH LEVEL and MONO SUB
OUTPUT LEVEL controls allow you to compensate for
sensitivity variations in amplifiers and drivers. Do not use
these to adjust overall system sensitivity unless you plan to
re-align the system afterward. With these set to the 0 dB mark
and the INPUT LEVEL set to 10, the crossover yields no
level change from input to output. This is the best gain
structure and provides the best signal-to-noise performance.

Crossover Philosophy

Now it gets real fun. The idea is to set the output LEVEL
controls on the crossover so that the entire speaker system has
a uniform, flat response. Unfortunately, the room in which
the speakers are placed has a habit of always getting into the
act, so things get messy. As a result there seems to be two
schools of thought regarding the use of active crossovers.

The Set-lt-Once-And-Glue-lt School

The philosophy here is to use the crossover to flatten
system response as much as possible without room acoustics
involved. This means setting up the system outside (unless
you happen to have a very large anechoic chamber handy)
and with the aid of a realtime analyzer and pink noise source,
adjust all of the crossover outputs so that the system is as flat
as possible. Once the system is tuned, the crossover is then
locked behind a security cover (posted guard is optional) and
never again touched. It is then the job of the system
equalizer(s) to normalize or flatten the response for each
different room.

The Fix-lt-With-The-Crossover School

Here the crossover knobs get a good workout, for the
crossover is used at each location to help flatten the system
along with the equalizer.

Regardless of which school you profess, the absolute
importance and effectiveness of some kind of realtime
analyzer in your system cannot be overstressed! An analyzer
saves tremendous amounts of time and provides the absolute
consistency, accuracy, and plain old good sound that very few
ears on this earth can deliver. They are affordable, easy to use
and amazingly effective. You owe it to yourself and your
audience to at least look into one of today’s cost-effective
analyzers—you’ll wonder how you managed at all without

Figure 1. See unmarked Frequency detent steps below.

STEP 0 123456 789101112131415161718192021222324252627282930

SILK

100 125 200 250 325 500 650 1000 1500 2000 3000 3200

SCREEN

CALC.

100 100 100 107 123 141 162 187 214 246 283 325 373 429 492 566 650 746 857 985 1131 1300 1493 1715 1970 2263 2599 2986 3200 3200 3200

FREQ.

one.

Figure 2. Frequency detent table with actual frequencies of all detent steps.

Manual-6

Setting the Mono Sub Output Level

Begin with the MONO SUB OUTPUT LEVEL trim set at
MAX. The LOW LEVEL control has no affect on the MONO
SUB OUTPUT. Make subwoofer level changes with either
the MONO SUB OUTPUT LEVEL or with the amplifier level
control. If you are using the MONO SUB OUTPUT instead of
the LOW OUTPUTS, be sure the 100 Hz FILTER is switched
OUT.

Setting Levels With a Realtime Analyzer

Any good 1/3-octave realtime analyzer will do, however,
Rane makes a rather inexpensive yet accurate one—the
RA 27. We had to get our plug in.

1. Set the INPUT LEVEL as described previously on page

Manual-2, and the LOW and HIGH LEVEL controls to
minimum; leave the FREQUENCY control as it was set
previously.

2. Place the analyzer microphone at least 15 feet away from

the speaker stack, on axis (dead ahead) and about chest
level. Minimize any background noise (fans, air condition­ers, traffic, wild animals, etc.) that could affect readings.

3. Run pink noise through the system, either through a mixer

channel or directly into the crossover. Turn all amplifier
controls at least half way up.

4. Slowly turn up the LOW LEVEL control until you hear a

healthy level of noise through the low frequency drivers (it
should sound like rumble).

4. Adjust the display controls on the analyzer so that it shows

the greatest number of 0 dB LED’s (green on Rane
equipment) below the crossover frequency.

6. Now slowly turn up the HIGH LEVEL control until the

display shows the same high frequency output level
average as the low frequency section.

IMPORTANT: Compression driver or horn high frequency
roll-off, bass roll-off, and room acoustics usually cannot be
corrected by the crossover.

If, for example, you are adjusting the HIGH FRE­QUENCY LEVEL control and observe a decline in frequency
response somewhat above the Crossover point, then set the
HIGH LEVEL control for equal display level near the
crossover point and leave it there. Use an equalizer to correct
the roll-off problem.

If you are tuning the system in a room, the acoustics will
greatly influence the system response, as shown by the
analyzer.

Move the microphone and check the analyzer system
response at several other locations. Adjust the crossover to
reach a fixed compromise setting as necessary. If you plan to
use the analyzer only once to set the crossover, set up the
speaker system in a quiet place outside or in a very large
concert theater, and run pink noise at low levels with closer
microphone placement to keep the room acoustics out of the
picture as much as possible.

Setting Levels Using an SPL Meter and Pink Noise
Generator

First, obtain a good SPL meter from a local electronics or
hi-fi store. Second, and perhaps a little trickier, get a pink
noise generator—again try electronics stores. You may also
use a sweep or tone generator in place of a pink noise
source—be sure to look at several different tones within each
crossover section to get a good average of driver response.

1. Run pink noise into the crossover Inputs (through the mixer

or directly, as is convenient).

2. Make sure all crossover LEVEL(s) are turned all the way

down and all amplifier level controls are at least half way
up to start with.

3. Turn the crossover INPUT LEVEL all the way up. Place

the SPL meter at least 15 feet from the speaker stack and
about chest high. Once positioned, make sure that the SPL
meter remains in the exact same location for the rest of the
procedure. Minimize all background noise (fans, air
conditioners, traffic, wild animals, etc.) to get accurate
readings. Set the SPL meter to “C-weighting” and “slow” if
those switches are present.

4. Slowly turn the LOW LEVEL up until there is a healthy

rumble coming from the bass speakers. Adjust the SPL
meter and/or LOW LEVEL until you get a 0 dB reading on
the meter. After this point do not change the controls on

the SPL meter.

5. Make a note of the LOW LEVEL control setting at the 0

dB adjustment just obtained, then reduce the LOW LEVEL
to “0” so that the pink noise disappears from the bass
speakers (revel in the silence...).

6. Now slowly turn up the HIGH LEVEL control so that pink

noise is heard from the high frequency speakers. Without
changing any settings on the SPL meter, adjust the cross­over HIGH LEVEL control until you obtain a 0 dB reading
on the SPL meter.

7. Return the LOW LEVEL to the previously recorded

setting. Now the low and high speakers are set at the same
level. The crossover should now be aligned. Make any
overall level adjustments with the INPUT LEVEL controls
and leave the output LOW and HIGH LEVEL controls
unchanged.

It is possible that you may turn one of the frequency
section output LEVEL controls all the way up and still not
have enough volume for a 0 dB reading (as determined by
previous section levels). This is probably due to different
sensitivities of amps, speakers and other level controls in the
system. When this happens, re-set the SPL meter so that it
reads 0 dB on this frequency section (you may have to “down
range” the meter and re-adjust the crossover INPUT LEVEL
control). Now go back and re-adjust the previous crossover
LEVEL controls, turning these down to get a 0 dB reading on
the meter.

Manual-7

SOUND SYSTEM INTERCONNECTION

Rane’s policy is to accommodate rather than dictate.
However, this document contains suggestions for external
wiring changes that should ideally only be implemented by
trained technical personnel. Safety regulations require that all
original grounding means provided from the factory be left
intact for safe operation. No guarantee of responsibility for
incidental or consequential damages can be provided. (In

other words, don’t modify cables, or try your own version of
grounding unless you really understand exactly what type of
output and input you have to connect.)

THE ABSOLUTE BEST RIGHT WAY TO DO IT

Use balanced lines and tie the cable shield to the metal
chassis (right where it enters the chassis) at both ends of the
cable.

A balanced line requires three separate conductors, two of
which are signal (+ and –) and one shield. The shield serves
to guard the sensitive audio lines from interference. Only by
using balanced line interconnects can you guarantee (yes,
guarantee) hum-free results. Always use twisted pair cable.
Chassis tying the shield at each end also guarantees the best
possible protection from RFI [radio frequency interference]
and other noises [neon signs, lighting dimmers].

THE NEXT BEST RIGHT WAY TO DO IT

The quickest, quietest and most foolproof method to
connect balanced and unbalanced is to transformer isolate
all unbalanced connections. Your audio dealer can recom­mend such a transformer.

The goal of transformer adaptors is to allow the use of
standard cables. With these transformer isolation boxes,
modification of cable assemblies is unnecessary. Virtually
any two pieces of audio equipment can be successfully
interfaced without risk of unwanted hum and noise.

Another way to create the necessary isolation is to use a
direct box. Originally named for its use to convert the high
impedance, high level output of an electric guitar to the low
impedance, low level input of a recording console, it allowed
the player to plug “directly” into the console. Now this term is
commonly used to describe any box used to convert unbal­anced lines to balanced lines.

THE LAST BEST RIGHT WAY TO DO IT

If transformer isolation is not an option, special cable
assemblies are a last resort. The key here is to prevent the

shield currents from flowing into a unit whose grounding
scheme creates ground loops (hum) in the audio path (i.e.,
most audio equipment). Do not be tempted to use 3-prong to
2-prong “cheater” adapters to lift grounds. This is a danger­ous and illegal practice.

It is true that connecting both ends of the shield is theo­retically the best way to interconnect equipment – though this
assumes the interconnected equipment is internally grounded
properly. Since most equipment is not internally grounded

properly, connecting both ends of the shield is not often
practiced, since doing so can create noisy interconnections.

involves disconnecting one end of the shield, even though one
can not buy off-the-shelf cables with the shield disconnected
at one end. The best end to disconnect is a matter of personal
preference and should be religiously obeyed; choose inputs or
outputs and always lift the side you choose (our drawings
happen to disconnect the outputs). If one end of the shield is
disconnected, the noise current stops flowing and away goes
the hum — but only at low frequencies. A one-end-only
shield connection increases the possibility of high frequency
(radio) interference since the shield may act as an antenna.
Many reduce this potential RF interference by providing an
RF path through a small capacitor (0.1 or 0.01 microfarad
ceramic disc) connected from the lifted end of the shield to
the chassis. The fact that many modern day installers still
follow this one-end-only rule with consistent success indi­cates this and other acceptable solutions to RF issues exist,
though the increasing use of digital and wireless technology
greatly increases the possibility of future RF problems.

your particular interconnection needs. Find the appropriate
output configuration from either your mixer output or the MX
22 output (down the left side), and then match this with the
correct balanced or unbalanced input to the MX 22 or the
amplifer (down the right side.) An “off-the-shelf” cable may
be available or modifiable. Soldering should only be at­tempted by those trained in the art.

SUMMARY

balanced wiring with shields tied to the chassis at the point of
entry, or transformer isolate all unbalanced signals from
balanced signals) then there is no guarantee that a hum free
interconnect can be achieved, nor is there a definite scheme
that will assure noise free operation in all configurations.

WINNING THE WIRING WARS

• Use balanced connections whenever possible.

• Transformer isolate all unbalanced connections from

• Use special cable assemblies when unbalanced lines cannot

• Any unbalanced cable must be kept under ten feet (three

“Sound System Interconnection”. If you would like the
complete note, call or email the factory, download it from
Rane's web site (addresses on the rear of this manual), or ask
your dealer for a copy.

A common solution to these noisy hum and buzz problems

See the following page for suggested cable assemblies for

If you are unable to do things correctly (i.e. use fully

balanced connections.

be transformer isolated.

meters) in length. Lengths longer than this will amplify
the nasty side effects of unbalanced circuitry's ground
loops.

This information was condensed from Rane Note 110,

Manual-8

VARIOUS XLR CABLE ASSEMBLIES

Manual-9

MOJO GLOSSARY

balanced line The recommended method of interconnecting audio
equipment. A balanced line requires three conductors: a twisted-pair
for the signal (positive and negative) and an overall shield. The

shield must be tied to the chassis at both ends for hum-free intercon­nect.

bandwidth Abbr. BW The numerical difference between the upper
and lower -3 dB points of an audio band.

clipping What occurs when a unit tries to produce a signal larger
than its power supply. The signal takes on a flat-topped, or clipped
shape. When an amplifier tries to go above its max power, it clips.

compressor A signal processing device used to reduce the
dynamic range of the signal passing through it. For instance, an

input dynamic range of 110 dB might pass through a compressor and
exit with a new dynamic range of 70 dB. The modern usage for
compressors is to turn down (or reduce the dynamic range of) just
the loudest signals. Other applications use compressors to control the
creation of sound. When used in conjunction with microphones and
musical instrument pick-ups, compressors help determine the final
timbre by selectively compressing specific frequencies and wave­forms.

connectors Audio equipment uses different styles:

RCA An unbalanced pin connector commonly used on

consumer and some pro equipment; aka phono plug
XLR A 3-pin connector common on pro audio equipment.
Preferred for balanced line interconnect; aka Cannon plug
¼" TRS 1. Stereo ¼" connector consisting of tip (T), ring (R),
and sleeve (S) sections, with T = left, R = right, and S =
ground/shield. 2. Balanced interconnect with the pos & neg
signal lines tied to T and R respectively and S acting only as an
overall shield. 3. Insert loop interconnect with T = send, R =
return, and S = ground/shield. [Think: ring, right, return]

¼" TS Mono ¼" connector consisting of tip (T) [signal] and
sleeve (S) [ground & shield] for unbalanced wiring.

constant-Q equalizer (also constant-bandwidth) The
bandwidth remains constant for all boost/cut levels. Since Q and
bandwidth are interrelated, the terms are fully interchangeable.

decibel Abbr. dB (named after Alexander Graham Bell). The
preferred method and term for representing the ratio of different
audio levels. Being a ratio, decibels have no units. Everything is
relative. So it must be relative to some 0 dB reference point. A suffix
letter is added to distinguish between reference points:

0 dBu A reference point equal to 0.775 V
+4 dBu Standard pro reference level equal to 1.23 V
0 dBV A reference point equal to 1.0 V

-10 dBV Standard reference level for consumer and some pro

audio use, equal to 0.316 V. RCA (phono) connectors are a
good indicator of units operating at -10 dBV

dynamic range The ratio of the loudest signal to the quietest signal
in a unit or system as expressed in decibels (dB).

expander A signal processing device used to increase the dynamic
range of the signal passing through it. Expanders complement

compressors. For example, a compressed input dynamic range of 70
dB might pass through a expander and exit with a new expanded
dynamic range of 110 dB. Modern expanders usually operate only
below a set threshold point, i.e., they operate only on low-level
audio. The term downward expander describes this type of applica­tion.

ground Any electrical reference point for measuring voltage levels.
Usually a large conducting body, such as the earth or an electric
circuit connected to the earth. Chassis should always be at earth

potential.

Never use an AC line cord ground-lift adapter or cut off the
3rd pin. It is illegal and dangerous.

WARNING: SHOCK HAZARD

headroom The level in dB between the typical operating level and

clipping. For example, a nominal +4 dBu system that clips at +20
dBu has 16 dB of headroom.

hum Unwanted sound contaminating audio paths due to EMI
(electro-magnetic interference) caused by AC power-lines &
transformers getting into unbalanced, poorly shielded, or improperly
grounded connecting cables. Hum has a definite smooth (sine wave)
repetitive sound based on the harmonics of 50/60 Hz such as 100/
120 Hz and 150/180 Hz.

interpolating Term meaning to insert between two points. If a
graphic equalizer’s adjacent bands, when moved together, produce
a smooth response without a dip in the center, they are interpolat-
ing between the fixed center frequencies.

levels Terms used to describe relative audio signal levels:

mic-level Nominal signal coming directly from a microphone.

Very low, in the microvolts, and requires a preamp with at least 60
dB gain before using with any line-level equipment.

line-level Standard +4 dBu or -10 dBV audio levels.
instrument-level Nominal signal from musical instruments

using electrical pick-ups. Varies widely, from very low mic-levels
to quite large line-levels.

limiter A compressor with a fixed ratio of 10:1 or greater. The
dynamic action prevents the audio signal from becoming larger than
the threshold setting.

Linkwitz-Riley crossover The most preferred active crossover
design. It features steep 24 dB/octave slopes, in-phase outputs, and
flat amplitude response. Due to the in-phase outputs the acoustic
lobe resulting when both loudspeakers reproduce the crossover
frequency is always on-axis (not tilted up or down) and has no
peaking.

noise 1. Interconnect. Unwanted sounds contaminating audio paths.
RFI (radio frequency interference) caused by broadcast signals
leaking into unbalanced, poorly shielded, or improperly grounded
connecting cables. Also by light dimmers, motor controls and
computers. 2. Music. A random mix of audio frequencies not
harmonically related, sounding like radio static.

polarity A signal’s electromechanical potential with respect to a
reference. For example, a microphone has positive polarity if a
positive pressure on its diaphragm results in a positive output
voltage. polarity vs. phase shift: polarity refers to a signal’s
reference NOT to its phase shift. Being 180 degrees out-of-phase and
having inverse polarity are DIFFERENT things. We wrongly say
something is out-of-phase when we mean it is inverted. One occurs
over a period of time; the other occurs instantaneously.

Q (upper-case) Quality factor. Defined to be the ratio of the center
frequency f divided by the bandwidth BW for a bandpass filter.

signal-to-noise ratio The ratio in dB between a reference level
and the noise floor. For example, a signal-to-noise ratio of 90 dB re
+4 dBu, means the noise floor is 90 dB below a +4 dBu ref.

unbalanced line An audio interconnect scheme using one wire
with an overall shield. The shield must perform two functions: act as
the return signal path (ground) and to protect the conductor from
noise (shield). Consequently this method is vulnerable to hum &
noise problems.

unity gain A gain setting of one. The level out equals the level in.

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