Mackie SRM1550 Owner's Manual - Smart Protect

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SRM1550 Powered Subwoofer

Smart Protect

There are advanced DSP protection mechanisms  

to safeguard the subwoofer and amplifier from  

inadvertent damage.

The protection circuits are designed to  

protect the subwoofer under reasonable    

and sensible conditions. Should you choose  

to ignore the warning signs [e.g. excessive distortion], 

you can still damage the speaker in the subwoofer  

by overdriving it past the point of amplifier clipping.  

Such damage is beyond the scope of the warranty.

Limiting

The driver has its own compression circuit which 

helps protect it from damaging transient peaks.    

The compressor is designed to be transparent and  

is not noticeable under normal operating conditions.

Overexcursion Protection

The SRM1550 has a 24 dB/octave high-pass filter  

at 30 Hz just prior to the low-frequency amplifier.  

This prevents very low frequencies from being amplified. 

Excessive low-frequency energy can damage the  

woofer by causing it to “bottom out,” also know as  

overexcursion, which is equivalent to a mechanical  

form of clipping.

Thermal Protection

All amplifiers produce heat. SRM1550s are designed 

to be efficient both electrically and thermally.

In the unlikely event of the amplifier overheating,  

a built-in thermal switch will activate, muting the  

signal.

When the amplifier has cooled down to a safe  

operating temperature, the thermal switch resets  

itself, and the subwoofer resumes normal operation.

If the thermal switch activates, try turning down the 

level control a notch or two on the mixing console (or 

the back of the subwoofer) to avoid overheating the 

amplifier. Be aware that direct sunlight and/or hot stage 

lights may be the culprit of an amplifier overheating.

AC Power

Be sure the subwoofer is plugged into an outlet that 

is able to supply the correct voltage specified for your 

model. It will continue to operate at lower  voltages,  

but will not reach full power.

Be sure the electrical service can supply enough  

amperage for all the components connected to it.

We recommend that a stiff (robust) supply of AC 

power be used because the amplifiers place high    

current demands on the AC line. The more power that  

is available on the line, the louder the speakers will play 

and the more peak output power will be available for 

cleaner, punchier bass. A suspected problem of “poor 

bass performance” is often caused by a weak AC supply 

to the amplifiers.

Never remove the ground pin on the power 

cord or any other component of the SRM1550. 

This is very dangerous.

Care and Maintenance

SRM subwoofers will provide many years of reliable 

service if you follow these guidelines:

•  Avoid exposing the subwoofers to moisture.  

If they are set up outdoors, be sure they are 

under cover if rain is expected.

•  Avoid exposure to extreme cold (below  

freezing temperatures). If you must operate  

the subwoofers in a cold environment, warm 

up the voice coils slowly by sending a low-level 

signal through them for about 15 minutes prior 

to high-power operation.

•  Use a dry cloth to clean the cabinets. Only do 

this when the power is turned off. Avoid getting 

moisture into any of the openings of the  

cabinet, particularly where the drivers are 

located.