MM-10AC Subwoofer
The MM-10AC subwoofer includes an internal power supply and locking AC PowerCON connectors. The MM-10AC receives audio from an XLR female Audio In connector, and also includes an XLR male Audio Loop Out connector for daisy-chaining audio signals.
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MM-10AC Rear Panel
MM-10AC AC Connectors
The MM-10AC subwoofer combines advanced loudspeaker technology with equally advanced power capabilities.
Understanding voltage and current requirements, as well as electrical safety issues, is critical to the safe operation of the MM-10AC. The MM-10AC rear user panel includes the following PowerCON AC connectors:
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MM-10AC AC Input (Left) and AC Loop Output (Right) Connectors
AC Input Connector (Blue)
The blue AC Input connector supplies power to the MM-10AC. The input is rated at 20 amps and uses a PowerCON AC mains locking connector that prevents accidental disconnections. A 10-foot AC power cable, rated at 15 amps, is included with each MM-10AC. If you replace the included AC power cable, make sure to use a cable with the appropriate power plug (on the other end) for the region in which you will operate the unit.
The AC Input connector also supplies power to any additional subwoofers connected to the MM-10AC’s gray AC Loop Output connector. Each MM-10AC requires approximately 0.9 A rms maximum at 115 V AC and 0.4 A rms maximum at 230 V AC.
Caution
When using the included AC power cable, do not loop more than 15 additional MM-10ACs from the AC Loop Output connector at 115 V (16 total for the circuit), and not more than 36 at 230 V (37 total for the circuit).
AC Loop Output Connector (Gray)
The gray AC Loop Output connector allows multiple
MM-10AC subwoofers to be looped and powered from a single power source. Connect the AC Loop Output of the first MM-10AC to the AC Input of the second MM-10AC, and so forth. The AC Loop Output uses a PowerCON AC mains locking connector that prevents accidental disconnections.
The maximum number of subwoofers that can be looped from the AC Loop Output connector is determined by the voltage of the power source, the current draw of the looped subwoofers, the circuit breaker rating, and the rating of the AC power cable connected to the MM-10AC.
Circuit Breaker/ Connector Rating | 115 V AC | 230 V AC | 100 V AC |
|---|---|---|---|
15 amps | 15 looped (16 total) | 36 looped (37 total) | 12 looped (13 total) |
Note
The current draw for the MM-10AC is dynamic and fluctuates as operating levels change. The numbers in Table 4 assume that operating levels are normal and not such that the subwoofers are constantly limiting.
Each MM-10AC ships with one AC looping connector for making AC looping cables. Assembled AC looping cables are available from Meyer Sound.
Caution
Do not exceed the current capability of the 20-amp Input connector for the MM-10AC. When looping MM-10ACs, consider the total current draw for all units on the circuit, including the first.
Power Connector Wiring
The MM-10AC requires a grounded outlet. To operate safely and effectively, it is extremely important that the entire system be properly grounded.
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AC Cable Wiring Scheme
When wiring international or special-purpose power connectors:
Connect the blue wire to the black terminal, or the terminal marked with an N.
Connect the brown wire to the red terminal, or the terminal marked with an L.
Connect the yellow and green wire to the green (or green and yellow) terminal, or the terminal marked with an E.
Caution
When creating AC power cables, it is important to preserve AC line polarity and connect the earth ground on both ends of the cable. The MM-10AC requires a grounded connection. Always use a grounded outlet and plug. It is extremely important that the system be properly grounded to operate safely and properly. Do not ground-lift the AC cable.
MM-10AC Voltage Requirements
The MM-10AC operates safely and continuously when the AC voltage stays within 100–240 V AC at 50 or 60 Hz. The subwoofer allows any combination of voltage to GND (neutral-line-ground or line-line-ground).
If the voltage drops below 90 V (brownout), the MM-10AC uses stored power to continue operating temporarily; the subwoofer will shut down if the voltage does not rise above the low boundary before the stored power is used.
If the voltage rises above 264 V, the power supply could become damaged.
Caution
The power source for the MM-10AC should always operate within the required voltage range, at least a few volts from the upper and lower ranges. This will ensure that AC voltage variations from the service entry — or peak voltage drops due to cable runs — will not cause the subwoofer’s amplifiers to cycle on and off or cause damage to the power supply.
MM-10AC Current Draw Requirements
The current draw for the MM-10AC is dynamic and fluctuates as operating levels change. Since different cables and circuit breakers heat up at varying rates, it is important to understand the following types of current ratings and how they affect circuit breaker and cable specifications.
Idle Current — The maximum rms current during idle periods.
Maximum Long-Term Continuous Current — The maximum rms current during a period of at least 10 seconds. The Maximum Long-Term Continuous Current is used to calculate temperature increases for cables, to ensure that cable sizes and gauges conform to electrical code standards. The current rating is also used as a rating for slow-reacting thermal breakers.
Burst Current — The maximum rms current during a period of around one second. The Burst Current is used as a rating for magnetic breakers. It is also used for calculating the peak voltage drop in long AC cable runs according to the following formula:
V pk (drop) = I pk x R (cable total)
The Burst Current can also be used to calculate the AC looping capability of the MM-10AC.
Ultimate Short-Term Peak Current — A rating for fast-reacting magnetic breakers.
Inrush Current — The spike of initial current encountered when powering on.
You can use the following table as a guide for selecting cable gauges and circuit breaker ratings for the system’s operating voltage.
Current Draw | 115 V AC | 230 V AC | 100 V AC |
|---|---|---|---|
Idle Current | 0.13 A rms | 0.13 A rms | 0.14 A rms |
Maximum Long-Term Continuous Current | 0.40 A rms | 0.25 A rms | 0.46 A rms |
Burst Current | 0.9 A rms | 0.4 A rms | 1.1 A rms |
Ultimate Short-Term Peak Current | 2.0 A peak | 1.4 A peak | 2.3 A peak |
Inrush Current | 4.0 A peak | 2.4 A peak | 4.0 A peak |
The minimum electrical service amperage required by an MM-10AC subwoofer system is the sum of the Maximum Long-Term Continuous Current for each unit. An additional 30 percent above the minimum amperage is recommended to prevent peak voltage drops at the service entry.
Note
For the best performance, the AC cable voltage drop should not exceed 10 V, or 10 percent at 115 V and 5 percent at 230 V. Make sure that even with AC voltage drops that the AC voltage always remains within the operating window.
Electrical Safety Issues
Pay close attention to these important electrical and safety issues.
The MM-10AC requires a grounded outlet. Always use a grounded outlet and plug.
Do not use a ground-lifting adapter or cut the AC cable ground pin.
Do not exceed the current capability of the 20-amp AC Input connector for the MM-10AC. When looping MM-10ACs, consider the total current draw for all units on the circuit, including the first.
Make sure the AC power cable for the MM-10AC has the appropriate power plug (on the other end) for the area in which you will operate the unit. In addition, the AC power cable must be rated for the total current draw of all MM-10ACs looped from the power source.
Do not operate the unit if the power cable is frayed or broken.
Keep all liquids away from the MM-10AC to avoid hazards from electrical shock.
MM-10AC Audio Connectors
The MM-10AC includes an XLR female Audio In connector and XLR male Audio Loop Out connector.
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MM-10AC Audio In and Audio Loop Out Connectors
Audio In Connector
The XLR female Audio In connector accepts balanced audio signals with an input impedance of 10 kOhm. The connector uses the following wiring:
Pin 1 — 220 kOhm to chassis and earth ground (ESD clamped)
Pin 2 — Signal (+)
Pin 3 — Signal (–)
Case — Earth (AC) ground and chassis
Pins 2 and 3 carry the input as a differential signal. Pin 1 is connected to earth through a 220 kOhm, 1000 pF, 15 V clamped network. This circuitry provides virtual ground lift for audio frequencies while allowing unwanted signals to bleed to ground. Make sure to use standard, balanced XLR audio cables with all three pins connected on both ends.
Telescopic grounding is not recommended, and shorting an input connector pin to the case may cause a ground loop, resulting in hum.
Tip
If unwanted noise or hiss is produced by the subwoofer, disconnect its input cable. If the noise stops, there is most likely nothing wrong with the subwoofer. To locate the source of the noise, check the audio cable, source audio, and AC power.
Audio Loop Out Connector
The XLR male Audio Loop Out connector allows multiple MM-10AC subwoofers to be looped from a single audio source. For applications that require multiple MM-10ACs, connect the Audio Loop Out of the first unit to the Audio In of the second, and so forth.
Note
The order in which subwoofers are connected when looping audio signals is unimportant. The Audio Loop Out connector is wired in parallel to the Audio In connector and transmits the unbuffered source signal even when the MM-10AC is powered off.
To avoid distortion when looping multiple MM-10ACs, make sure the source device can drive the total load impedance of the looped subwoofers. In addition, the source device must be capable of delivering approximately 20 dBV (10 V rms into 600 ohms) to yield the maximum peak SPL over the entire operating bandwidth of the subwoofers. Most professional audio equipment can transmit these source levels.
To calculate the load impedance for the looped subwoofers, divide 10 kOhms (the input impedance for a single MM-10AC) by the number of looped subwoofers. For example, the load impedance for 10 MM-10AC subwoofers is 1000 ohms (10 kOhms / 10). To drive this number of looped subwoofers, the source device should have an output impedance of 100 ohms or less. This same rule applies when looping MM-10AC subwoofers with other self-powered Meyer Sound loudspeakers.
Note
Most source devices are capable of driving loads no smaller than 10 times their output impedance.
Caution
Make sure that all cabling for looped subwoofers is wired correctly (Pin 1 to Pin 1, Pin 2 to Pin 2, and so forth) to prevent the polarity from being reversed. If one or more subwoofers in a system have reversed polarity, frequency response and coverage will be significantly degraded.
MM-10AC Input Polarity Switch
The Input Polarity switch swaps the polarity of the audio source signal, which is sometimes necessary to acoustically align the subwoofer with other loudspeakers in the system. When the switch is in the up (+), non-inverting position, pin 2 is hot relative to pin 3, resulting in a positive pressure wave when a positive signal is applied to pin 2. When the switch is in the down (–), inverting position, pin 3 is hot relative to pin 2, resulting in a positive pressure wave when a positive signal is applied to pin 3.
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MM-10AC Input Polarity Switch
Note
The Input Polarity switch only affects the subwoofer signal. It has no effect on the Audio Loop Out signal.
MM-10AC Limit LED
The MM-10AC has a three-color Limit LED on its rear panel that changes color to indicate the subwoofer’s status.
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MM-10AC Limit LED
Powering On (Green)
When powering up the MM-10AC subwoofer, the following startup events occur and are indicated by the Limit LED:
The LED flashes green and then yellow during power-up.
The LED turns solid green indicating the subwoofer is ready to reproduce audio.
Caution
If the Limit LED turns red and stays solid red after powering up and the audio is muted, the subwoofer has encountered a failure and may need to be serviced. Contact Meyer Sound Technical Support.
If the Limit LED turns solid red and the MM-10AC continues to output audio, though at reduced levels, the subwoofer’s voltage may have dropped below 25 V DC. When these conditions are encountered, operation of the subwoofer should cease and its power supply and cabling should be verified.
Limiting (Yellow)
Limiting activity is indicated when the Limit LED turns yellow. When engaged, the limiter protects the subwoofer’s driver and prevents signal peaks from causing excessive distortion in the subwoofer’s amplifier, thereby preserving headroom and maintaining smooth frequency responses at high levels. When the level returns to normal, below the limiter’s threshold, the LED turns green and limiting ceases.
The MM-10AC performs within its acoustical specifications at normal temperatures when the Limit LED is green, or if the LED turns yellow for two seconds or less and then returns to green for at least one second. If the LED remains yellow for longer than three seconds, the subwoofer enters hard limiting where:
Increases to the input level have no effect.
Distortion increases due to clipping and nonlinear driver operation.
The drivers are subjected to excessive heat and excursion, which will compromise their life span and may eventually lead to damage over time.
Caution
The Limit LED turns yellow when the subwoofer’s signal rises 2 dB above the limiting threshold, and indicates a safe, optimum level has been exceeded. If the MM-10AC subwoofers in a system begin to limit before reaching the desired SPL, consider adding more subwoofers to the system to achieve the desired SPL without exposing the subwoofers to excessive levels and possible overheating.
MM-10AC Temperature and Limiting
The Limit LED turns solid yellow when its heat sink temperature reaches 65° C (145° F), indicating the unit is reaching its maximum heat dissipation and a reduction in SPL is recommended. While the MM-10AC will continue to operate while the LED is yellow, the limiter threshold is lowered to a safe level (causing the output level to be lowered by 6 dB) to prevent the subwoofer from overheating. When the temperature of the heat sink cools to 50°C (122°F), the LED changes from yellow to green and the limiter threshold returns to normal.
Clipping (Red)
The Limit LED flashes red when its input signal causes the amplifier to overload. If the LED flashes red continuously, the subwoofer is severely overloaded and a reduction in the input level is recommended.
Caution
If the Limit LED turns solid red and the subwoofer continues to output audio, though at reduced levels, the subwoofer’s voltage may have dropped below 90 V AC. When these conditions are encountered, operation of the subwoofer should cease and its power supply and cabling should be verified.