Mackie SRM-150 Power light on but no sound at all.

SOURCE: I have a pair of

you have one of two problems.1) the woofer is blown(most likely) or 2) the crossover is fried(rare). Take the woofer out and press on the speaker cone(softly). If there is a scratchy feeling when you move it or if it doesn't move at all, you'll either need a new woofer, or get that one reconed.
good luck.

SOURCE: Repair a Mackie SRM 450 Speaker

You probably need to replace the diaphragm. The diaphragm is located behind the back cap. Simply remove the back cap, remove the diaphragm, clean the voice coil gap with a piece of masking tape, install a new replacement diaphragm, reinstall the back cap. That it!
You can see videos on how to replace diaphragm at this link.
http://www.soundspeakerrepair.com/speaker-parts-c/INST/Installation+Instructions
You can buy a new Mackie SRM450 diaphragm at this link.
http://www.soundspeakerrepair.com/speaker-parts-cp/SRM450-DIA/DIA-Mackie/Mackie/

SOURCE: Hi i have a Mackie srm 150 monitor and have blown

The speaker can be purchased from Mackie directly. Follow the link below to go to the support page and continue from there. I would call them with the specifics of your unit to get the correct replacement driver. It is common for different serial numbered units to use different drivers. They can confirm this when you call. I have dealt with them many times and have found them to be very helpful and prompt for parts delivery.

Dan

Link: http://www.mackie.com/support/index.html

Testimonial: "Thanks Dan will contact them "

SOURCE: Mackie SRM-450 tweeter distorts sound

I wish to change access to the diaphragm

SOURCE: hello there i have a

The most common cause of this is a blown horn. A replacement can be ordered from Mackie directly. Remove the screws that hold the plastic horn in place. At the rear of this part will be the tweeter assembly that unscrews from the horn. This needs to be replaced.

Another possibility is that the tweeter driver has broken from the horn itself and is inside the cabinet. Remove the horn and you may find that the aluminum part has broken. Replace the horn which comes with that part and you should be fine.

Dan