• Ceiling Speaker Calculator

  • PendantConnect Speaker Cable

  • Amplifier Energy Usage and Thermal Dissipation

  • Amplifier Power Required

  • dB to Volts

  • Inverse Square Law

  • Ohm's Law

  • Power Ratio

  • Voltage Ratio

Audio Calculators A collection of convenient, easy-to-use audio calculation tools from Extron

PendantConnect Speaker Cable Calculator

To calculate the length of PendantConnect speaker cable to pre-cut prior to installation, use the calculator below. Enter the distance from the floor to the bottom of the ceiling electrical box in the Ceiling Height box. Enter the desired distance from the floor to the bottom of the pendant speaker in the Speaker Height box. Then click on Calculate. The results will be displayed on the right, along with a printable diagram.

Hide Labeled Diagram View Labeled Diagram
Pendant Cable Calculator Diagram
+ Show Advanced Options
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Note: Results are shown to nearest 16th of an inch and nearest 0.1 cm
+ Show Advanced Options
- Hide Advanced Options

Note: Results are shown to nearest 16th of an inch and nearest 0.1 cm

Amplifier Energy Usage and Thermal Dissipation

Enter the type and quantity of Extron amplifiers required for your project. This tool will calculate the total input power, heat load, and the required cooling.
AC Input 115 VAC/60 Hz 230 VAC/50 Hz Reset
  Ohms Ohms
  Ohms Ohms
  Ohms Ohms
  Ohms Ohms

Annual Calculation
INPUT POWER = Watts kW-hr

Amplifier Power Required

Enter the following values and then press "Calculate" to determine the power output required for the amplifier.
Distance to farthest listener Meters   Feet Reset
Desired sound pressure level at listener dB SPL
Loudspeaker sensitivity rating (at 1 Watt at 1 meter) dB  
Amplifier headroom dB ("0" if none desired)

Watts Calculate

dB to Volts

Enter any value and then press "Calculate" to find out the equivalent values in volts, dBV, or dBu.
dBu Reset
Volts Calculate

Inverse Square Law

Enter the following values and then press "Calculate" to determine the sound pressure level at the new distance from the source.
Reference distance from source UOM (ft, yd, m, etc.) Reset
Sound pressure level at reference distance dB SPL
New distance from source UOM (ft, yd, m, etc.)
Note: Distances must be expressed in the same Unit of Measure, e.g. feet, yards, or meters.

dB Calculate

Ohm's Law

Enter any of the two values and then press "Calculate" to determine the other values.
Voltage Volts (V) Reset
Current Amperes (A)
Resistance Ohms (Ω)
Power Watts (W) Calculate

Power Ratio

To determine the power ratio in dB from one wattage level to another, enter the values below, then press "Calculate".
P1 Watts Reset
P2 Watts
Difference dB Calculate

Voltage Ratio

To determine the voltage ratio in dB from one voltage level to another, enter the values below, then press "Calculate".
V1 Volts Reset
V2 Volts
Difference dB Calculate

Ceiling Speaker Calculator

To calculate the number of ceiling speakers required for your project, enter the room dimensions, Extron ceiling speaker model, anticipated type of playback content, and allowable variance in sound level between speakers. Results can be viewed and printed by selecting the VIEW/PRINT COVERAGE MAP button in the Results section. The Ceiling Speaker Calculator also determines the amplifier power necessary to drive the speakers.

+ Show Advanced Options

The recommended cable for distributed speakers systems with cable runs under 100’ (30M) is Extron SPK 16, 16 AWG Speaker Cable. For runs over 100’ (30M), use SPK 14, 14 AWG Speaker Cable.

Extron Audio Calculators

These are a series of audio calculators that sound system designers, engineers, and technicians frequently need to access, such as determining amplifier power requirements, converting between dBu and dBV or volts, or estimating the loss in sound pressure level with an increase in distance. All of the easy-to-use calculation tools are accessible right here by clicking on any of them above.

What It Is

Extron XTRA Series amplifiers are highly efficient Class D amplifiers that draw less power than conventional amplifiers. As ENERGY STAR qualified amplifiers, they also automatically enter a very low power "sleep" mode after 25 minutes in which no signal is present at the input. System designers frequently want to know the energy usage of a rack of amplifiers, as well as how much cooling will be required. Since amplifiers generate significant waste heat, this is a key factor.

This audio tool calculates the total input power draw, thermal dissipation or waste heat, and the required cooling for a collection of amplifiers. Up to four types of Extron XTRA™ series of amplifiers can be selected. Select the line voltage for the region in which the amplifier will be used, select the type and quantity of amplifiers, select the desired speaker impedance for amplifiers with low impedance outputs, and then press Calculate.

Essential Formulas

Power Draw and Thermal Dissipation figures at 1/8th power output are taken from the XTRA Series amplifier product specifications found at www.extron.com.

Cooling Required follows the industry practice of measuring air conditioning cooling capacity in tons. The required capacity is calculated by dividing the BTU/hr heat load by 12,000.

Annual Calculation assumes amplifiers are operating for 2,080 hours at 1/8th power, and 6,680 hours in standby mode.

For more information, see the white paper at www.extron.com/xtrapaper. Please see the XTRA Series User Guide for proper amplifier spacing requirements.

What It Is

Sound system designers frequently want to know much amplifier power will be needed to deliver adequate sound pressure levels for the application. This can be determined based on the desired listener distance from the speaker, the desired sound pressure level of the audio at this distance, and the loudspeaker's published sensitivity rating to provide the reference acoustical output at 1 watt at 1 meter. For Extron speakers, use the dropdown box and select the desired Extron speaker to automatically load its sensitivity into the calculator field. Additional headroom should be added for the amplifier, for example, 10 dB, to account for variability in program audio levels.

This audio tool calculates the acoustical attenuation from the reference location of 1 meter (3.28 feet) to the listener, and then applies this, together with the sensitivity rating and amplifier headroom, to determine the necessary output power from the amplifier.

Essential Formulas

APR = 10((LP + H – LS + 20 log (D2/ DR))/10)


APR = amplifier required power

LP = required SPL at listener

H = desired amplifier headroom

LS = loudspeaker sensitivity at 1 watt and 1 meter

D2 = distance to farthest listener

DR = 1 meter or 3.28 feet reference distance

What It Is

Volts, dBV, and dBu are three units describing voltage levels that are used interchangeably in professional audio based on the point of reference. This audio tools provides a quick and convenient means to convert between them. dBV refers to a voltage magnitude referenced to 1 volt, while dBu is referenced to 0.775 volts.

Essential Formulas

dBV = dBu - 2.21

Volts = 10(dBu / 20) x 0.775

dBu = dBV + 2.21

Volts = 10(dBV/20)

dBu = 20 log (Volts/0.775)

dBV = 20 log (Volts)

What It Is

Sound pressure level - SPL decreases 6.02 dB as a listener's distance doubles from the sound source. This number is commonly rounded down to 6 dB. The opposite is true as the listener halves the distance to the source, so that the SPL decreases or increases by 6 dB with every distance doubling or halving, respectively. The Inverse Square Law is used to calculate the change in SPL with distance, and is useful in predicting the sound pressure level a listener will experience as speaker placement and sound levels are considered.

Inverse Square Law

Essential Formulas

LN = LR - 20 log (DN/DR)

DR = reference distance

DN = new distance

LR = SPL at reference distance

LN = SPL at new distance

What It Is

Ohm's Law describes the relationships that exist between voltage, current, and resistance. Quantities of these properties are expressed in volts (V); amperes, "amps" (A); and ohms (Ω) respectively. The product of voltage and current is the applied power and is expressed in watts (W).

Ohm's Law/ Watts Law

Essential Formulas

E = IxR

W = ExI

What It Is

A change in power, from P1 to P2 can be expressed as a ratio in decibels with the equation dB = 10*log(P2/ P1) . A doubling in the power level translates to a power ratio of 3 dB. Similarly, halving the power equals a -3 dB power ratio.

Essential Formulas

dB = 10 log (P2/P1)

What It Is

A change in voltage, from V1 to V2 can be expressed as a ratio in decibels with the equation RV = 20*log(V2/ V1). A doubling in the voltage level translates to a power ratio of 6 dB. Similarly, halving the power equals a -6 dB voltage ratio. This calculator can also be used to express differences between two distances or pressures.

Essential Formulas

dB = 20 log (V2/ V1)

What It Is

Sound system designers and sales engineers need to know how many ceiling speakers are required for proper coverage in a given application. Each environment is different based on the room dimensions and ambient noise. Consideration must be given to the listener height, audio program content, desired SPL - sound pressure level, and how much the client will tolerate sound pressure level variances throughout the space. Since speakers are often tailored for specific applications, their design and performance play a major role in determining quantities and positioning.

This audio tool utilizes a database of speaker coverage angle values for Extron ceiling speakers, based on the type of audio content and amount of SPL attenuation. Speaker performance data for traditional polar plots were normalized and then linearized onto a horizontal plane to calculate sound pressure levels for standing or seated listeners. This tool also provides power recommendations and transformer tap settings based on speaker sensitivity data and desired SPLs.

Essential Formulas

RC = (HC - HL) tan (A)
DC = (HC - HL) / cos (A)
ΔLA = 20 log [DR / (HC - HL)]
ΔLE = 20 log (DR / DC)

RC = Radius at coverage angle and listening plane
HC = Ceiling height
HL = Listener height
A = Coverage angle at isobar
DC = Distance from speaker at coverage angle and listening plane
ΔLA = Distance loss for listener on-axis (inverse square law)
DR = 1 meter or 3.28 feet reference distance
ΔLE = Distance loss for listener at isobar
LMINREF = Minimum target level on-axis at reference distance
LMIN = Minimum needed level for listener at isobar
Isobar = Boundary with a specified SPL attenuation
LMAXREF = Maximum target level on-axis at reference distance
LMAX = Maximum target level for listener on-axis


What It Is

PendantConnect™ speaker cable is an Extron exclusive hybrid design incorporating the speaker wires and steel support cable into a single outer jacket, allowing the integrator to achieve an absolute vertical hang with only a single visible cable. PCC-1 cable is used exclusively for the SF 3PT SoundField Pendant Speaker while PCC-2 cable is used exclusively for the SF 26PT SoundField Pendant Speaker.

This audio tool calculates cut, strip, and reference mark points for PendantConnect speaker cable based on ceiling height and desired speaker height.

Essential Formulas

The calculator on this page is used when pre-cutting cable prior to cable termination. The simplified formula below may be used when the PendantConnect speaker cable has already been terminated at the speaker end.

Room Height - Bottom of Speaker Height = Cut point on cable, measured from the top of the speaker cap. Then strip six inches down from the cut point.

Extron Audio Products

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White Papers

Provide further insight into key Extron audio technologies behind our high performance amplifiers, speakers and DSP products.

Technical Articles

Learn more about DSP and audio amplification technologies as they relate to Extron audio products.

Audio Glossary

A comprehensive glossary of audio terms applicable to pro AV systems.