Amplification and Audio
HMS-15AC’s drivers are powered by an efficient onboard two-channel amplifier that uses minimal AC power when idle. Internal signal processing includes a crossover, frequency and phase correction, and limiters that prevent driver overexcursion and regulate voice coil temperatures, ensuring maximum driver lifespan.
Audio Connectors
HMS-15AC includes 3-pin XLR audio connectors for Input and Loop Output.
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The USW-112P compact narrow subwoofer provides big bass sound for very tight spaces. Its compact rectangular enclosure and slanted connector panel enable flushmounting of the cabinet against wall surfaces, reducing required installation depth to 12 inches, including connectors.
Audio Loop Output Connector
The male XLR Loop connector allows multiple HMS-15AC loudspeakers to be looped from a single audio source.
Connect the Loop Output of the first loudspeaker to the Input of the second, and so forth. The Loop Output connector is wired in parallel to the Input connector and transmits the unbuffered source signal even when the loudspeaker is powered off.
To avoid distortion when looping multiple HMS-15AC loudspeakers, make sure the source device can drive the total load impedance of the looped loudspeakers. In addition, the source device must be capable of delivering 20 dBV (10 V rms into 600 ohms) to yield the maximum peak SPL over the operating bandwidth of the loudspeaker.
To calculate the load impedance for the looped loudspeakers, divide 10 kOhms (the input impedance for a single HMS-15AC) by the number of looped loudspeakers. For example, the load impedance for 10 HMS-15AC loudspeakers is 1000 ohms (10 kOhms / 10). To drive this number of looped loudspeakers, the source device should have an output impedance of 100 ohms or less. This same rule applies when looping HMS-15AC loudspeakers with other self-powered Meyer Sound loudspeakers and subwoofers.
Note
Most source devices are capable of driving loads no smaller than 10 times their output impedance.
Tip
Meyer Sound’s Galileo® GALAXY Network Platform is highly recommended for driving systems with multiple loudspeakers. In addition to maintaining signal integrity for long cable paths, GALAXY processors offer independent inputs and outputs and presets for optimizing HMS-15AC array performance and subsystem integration.
Audio Loop Output Connector
The male XLR Loop connector allows multiple HMS-15AC loudspeakers to be looped from a single audio source.
Connect the Loop Output of the first loudspeaker to the Input of the second, and so forth. The Loop Output connector is wired in parallel to the Input connector and transmits the unbuffered source signal even when the loudspeaker is powered off.
To avoid distortion when looping multiple HMS-15AC loudspeakers, make sure the source device can drive the total load impedance of the looped loudspeakers. In addition, the source device must be capable of delivering 20 dBV (10 V rms into 600 ohms) to yield the maximum peak SPL over the operating bandwidth of the loudspeaker.
To calculate the load impedance for the looped loudspeakers, divide 10 kOhms (the input impedance for a single HMS-15AC) by the number of looped loudspeakers. For example, the load impedance for 10 HMS-15AC loudspeakers is 1000 ohms (10 kOhms / 10). To drive this number of looped loudspeakers, the source device should have an output impedance of 100 ohms or less. This same rule applies when looping HMS-15AC loudspeakers with other self-powered Meyer Sound loudspeakers and subwoofers.
Note
Most source devices are capable of driving loads no smaller than 10 times their output impedance.
Tip
Meyer Sound’s Galileo® GALAXY Network Platform is highly recommended for driving systems with multiple loudspeakers. In addition to maintaining signal integrity for long cable paths, GALAXY processors offer independent inputs and outputs and presets for optimizing HMS-15AC array performance and subsystem integration.
Limiting
When source levels for HMS-15AC exceed optimum input levels for its drivers, limiting is engaged and is indicated by the two Limit LEDs on the user panel. The bottom LED indicates limiting for the low-frequency channel. The top LED indicates limiting for the high-frequency channel. When engaged, limiting not only protects the drivers, but also prevents signal peaks from causing excessive distortion in the amplifier’s channels, thereby preserving headroom and maintaining smooth frequency responses at high levels.
When source levels return to normal, below the limiter’s threshold, limiting ceases.
HMS-15AC performs within its acoustical specifications at normal temperatures when the Limit LEDs are unlit, or if the LEDs are lit for two seconds or less and then turn off for at least one second. If an LED remains lit for longer than three seconds, the loudspeaker 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 LEDs indicate when a safe, optimum level is exceeded. If an HMS-15AC loudspeaker begins to limit before reaching the required SPL, consider adding more loudspeakers to the system.
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Limit and On/Status LEDs
On/Status LED
During normal operation, when HMS-15AC is powered on, the On/Status LED is solid green. If the loudspeaker encounters a hardware fault, or the unit begins to overheat, the LED flashes red. In some instances, the loudspeaker will continue to output audio while the LED flashes red, though with a reduction in the limiter threshold and acoustic output to protect the loudspeaker.
If a loudspeaker is overheating (for RMS-equipped loudspeakers, this situation can be verified in Compass RMS), a reduction in SPL may be necessary. If after a reduction in SPL and an appropriate cooling period the On/Status LED continues to flash red (does not return to solid green), contact Meyer Sound Technical Support.
If the On/Status LED flashes red and the loudspeaker does not output audio, contact Meyer Sound Technical Support immediately.
Caution
If an HMS-15AC loudspeaker system consistently overheats before reaching the desired SPL, consider adding more units to the system.
Note
During startup, the On/Status LED flashes multiple colors successively. For more information about the power on sequence, see Intelligent AC Power Supply.
Tip
When HMS-15AC is connected to an RMS network, the RMS software provides additional feedback on the loudspeaker’s operating temperature. For more information, see RMS Remote Monitoring System.
Amplifier Cooling System
HMS-15AC’s amplifier relies solely on natural convection for cooling from air flowing over its heat sink. The efficient design of the amplifier and heat sink profile keeps temperatures low, even when the unit is used at high ambient temperatures in tightly packed conditions, and when driven continuously at high output levels.
Caution
The HMS-15AC heat sink can reach very high temperatures during extreme operation. Use utmost caution when approaching the top of the loudspeaker.