Audio
The Amie drivers are powered by a proprietary two-channel, class D amplifier. The audio signal is processed with electronic crossover, by correction filters for flat phase and frequency responses, and by driver protection circuitry. Each channel has peak and rms limiters that prevent driver over-excursion and regulate voice coil temperatures.
The Amie user panel includes Input and Loop output connectors for audio, and Limit and Active LEDs, as shown in the figure below.
Amie User Panel
Audio Connectors
Amie has XLR 3-pin connectors for audio Input and audio Loop output, as shown in the figure below.
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XLR 3-Pin Audio Connectors, Input and Loop Output
Audio Input (XLR 3-Pin)
The XLR 3-pin connector accepts balanced audio signals with an input impedance of 10 kΩ. The connector uses the following wiring scheme:
Pin 1 — 1 kΩ 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 1 kΩ, 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 balanced XLR audio cables with pins 1–3 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 the loudspeaker produces unwanted noise or hiss, disconnect its input cable. If the noise stops, there is most likely nothing wrong with the loudspeaker. To locate the source of the noise, check the source audio, AC power, and electrical ground.
Audio Loop Output (XLR 3-Pin)
The XLR 3-pin Loop output connector allows multiple loudspeakers to be looped from a single audio source. The Loop output connector uses the same wiring scheme as the Input connector (see Audio Input (XLR 3-Pin)). For applications that require multiple Amie, connect the Loop output of the first loudspeaker to the Input of the second loudspeaker, and so forth.
Note
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.
Calculating Load Impedance for Looped Audio Signals
To avoid distortion when looping multiple 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 approximately 20 dBV (10 V rms into 600 Ω) to yield the maximum SPL over the operating bandwidth of the loudspeakers.
To calculate the load impedance for the looped loudspeakers, divide 10 kΩ (the input impedance for a single loudspeaker) by the number of looped loudspeakers. For example, the load impedance for 10 Amie is 1000 Ω (10 kΩ/ 10). To drive this number of looped loudspeakers, the source device should have an output impedance of 100 Ω or less. This same rule applies when looping Amie with other Meyer Sound self-powered loudspeakers.
Note
Most source devices are capable of driving loads no less than 10 times their output impedance.
Tip
Audio outputs from Meyer Sound’s loudspeaker GALAXY Network Platform have an output impedance of 50 ohms. Each output can drive up to 20 Meyer Sound (10 kΩ) loudspeakers without distortion.
Caution
Make sure that all cabling for looped loudspeakers 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 loudspeakers in a system have reversed polarity, frequency response and coverage will be significantly degraded.
TruPower Limiting
The Amie employs Meyer Sound’s advanced TruPower® limiting. Conventional limiters assume a constant driver impedance and set the limiting threshold by measuring voltage alone. This method is inaccurate, because driver impedances change as frequency content in the source material changes, and as thermal values for the loudspeaker’s voice coil and magnet vary. Consequently, conventional limiters often begin limiting prematurely, which reduces system headroom and dynamic range.
In contrast, TruPower limiting anticipates varying driver impedances by measuring both current and voltage to compute the actual power dissipation in the voice coil. This approach improves performance, both before and during limiting, by allowing the driver to produce the maximum SPL across its entire frequency range while also retaining signal peaks. TruPower limiting also eliminates power compression at high levels over lengthy periods, which helps regulate voice coil temperatures, thereby extending the life of the driver.
HF and LF Limit LEDs
The low- and high-frequency drivers for Amie are powered by separate amplifier channels, each with their own limiter. Limiting activity is indicated with two Limit LEDs on the user panel. The right Limit LED, shown in the figure below, indicates limiting for the high-frequency channel and the left Limit LED indicates limiting for the low-frequency channel.
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Amie Limit LEDs (LF unlit: not limiting, HF lit: limiting occurring)
When engaged, the limiters not only protect the drivers but also prevent signal peaks from causing excessive distortion in the amplifier channels, thereby preserving headroom and maintaining smooth frequency response at high levels. When levels return to normal, below the limiter thresholds, limiting ceases.
Amie performs within its acoustical specifications at normal temperatures when the Limit LEDs are unlit, or when the LEDs are lit for 2 seconds or less and then turn off for at least 1 second. If the LEDs remain lit for longer than 3 seconds, the loudspeaker enters hard limiting where:
Increases to the input level have no effect
Distortion increases due to clipping
Drivers are subjected to excessive heat and excursion, thereby compromising their lifespan
Caution
The Limit LEDs indicate when a safe, optimum level is exceeded. If an Amie loudspeaker system begins to limit before reaching the desired SPL, consider adding more units to the system.
Amplifier Cooling System
The Amie loudspeaker is convection cooled. The amplifier’s heat sink provides natural convection cooling from the air flowing near its fins.
Caution
To keep Amie from overheating, allow at least 3 inches behind the loudspeaker for proper ventilation.
The Amie heat sink can reach temperatures up to 80° C (176° F) during extreme operation. Wait 15 minutes for the unit to cool before touching.
Active/Status LED
During normal operation, when Amie is powered on, the Active/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, you can verify this situation in Compass RMS), a reduction in SPL may be necessary. If, after a reduction in SPL and an appropriate cooling period, the Active/Status LED continues to flash red (does not return to solid green), contact Meyer Sound Technical Support.
If the Active/Status LED flashes red and the loudspeaker does not output audio, contact Meyer Sound Technical Support immediately.
Caution
If an Amie loudspeaker system consistently overheats before reaching the desired SPL, consider adding more units to the system.
Note
During startup, the Active/Status LED flashes multiple colors successively. For more information about the power on sequence, see “Intelligent AC Power Supply” on page 14.
Tip
When an Amie is connected to an RMS network, the Compass RMS software provides additional feedback about the loudspeaker’s hardware status and operating temperature. For more information, see Chapter 6, “RMS Remote Monitoring System.