M Amplifiers

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M Special Edition
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Technical Questions




Into 4 ohms @ 12.5/14.4 VDC

25/65 WRMS x 2

Into 2 ohms @ 14.4 VDC

70 WRMS x 2

Bridged into 4 ohms @ 14.4 VDC

140 WRMS x 1




Into 4 ohms @ 12.5/14.4 VDC

50/85 WRMS x 2

Into 2 ohms @ 14.4 VDC

120 WRMS x 2

Bridged into 4 ohms @ 14.4 VDC

245 WRMS x 1



Into 4 ohms @ 12.5/14.4 VDC

100/185 WRMS x 2

Into 2 ohms @ 14.4 VDC

230 WRMS x 2

Bridged into 4 ohms @ 14.4 VDC

500 WRMS x 1



Into 4 ohms @ 12.5/14.4 VDC

40/55 WRMS x 4

Into 2 ohms @ 14.4 VDC

80 WRMS x 4

Bridged into 4 ohms @ 14.4 VDC

105 WRMS x 2


Frequency Response

+/-1dB from 20Hz to 20kHz

Signal to Noise Ratio


Input Sensitivity

200 millivolts to 2 volts

Input Impedance

>10k ohms

Input Voltage Range

10.5 volts to 15.0 volts

Typical current draw at idle

750 milliamps

Crossover Frequencies

30Hz to 600Hz

Crossover Slopes

12dB per Octave

Bass EQ

0 to + 12dB @ 45Hz

Minimum Impedance

2 ohm bridged/1ohm stereo

Dimensions, M44 & M100

18.0"L x 10.6"W x 2.0"H

Dimensions, M50

11.25"L x 10.6"W x 2.0"H

Dimensions, M25

8.25"L x 10.6"W x 2.0"H


 What year where the M series amps produced?



 How much power does my M series amplifier make at 2 ohms bridged?

The continuous power at 2 ohms or 1 ohm bridged remains about the same as it was for 4 ohms bridged. 

When designing the M series amps, we wanted a design that made its best power at normal loads. By normal, we mean 4 ohms bridged. We know that no matter what we say, or how loud we say it - People will still hook the amp up to lower impedances trying to get more power. So, our number one goal is that the amp continue to operate at lower impedances. The only way to do that is to limit the continuous power output of the amp when it's hooked up to lower impedances. Here's why -

Wattage is equal to voltage times current. Running the amp at 2 ohms bridged means more output current. Current makes heat. We can't allow the amp to make more heat than the heatsink can reasonably dissipate. With the addition of cooling fans, the heatsink can manage a more heat than what's generated from a 4 ohm bridged load so there's some room for a bit more power. Here's how we limit the power increase to what's manageable:

The M series amps have a circuit that detects the amount of current leaving the speaker terminals. If the current is high enough, AND lasts long enough (longer than 50 milliseconds), the circuit limits the amount of voltage that the power supply can produce. This in turn limits the power output of the amp. So continuous power output remains about the same with the power composed of more current and less voltage.

There is a bright side to all this. Remember I said that the excess current demand had to last longer than 50ms. The dynamic peaks in most music last less than 20ms. Therefore, the circuit never has a chance to affect the power supply voltage for musical peaks. All this means that the amp is allowed to make more power with musical peaks while continuous power remains about the same. You could say that the "headroom" of the amp is increased.

If you want to run the amp 2 ohms bridged, go for it. Just understand that it will run warmer (fans may be necessary) and will pull more current from your car to make those musical peaks (add more capacitors). I wouldn't recommend running it 1 ohm bridged. The amp will shut down (red LED) if the output current gets too high (looks like a shorted speaker).


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Copyright © 1999 Phoenix Gold Corporation. All rights reserved. 
Last modified: Thursday October 21, 1999.