mackie srm 450 problem

[djdamianos]

Hi to all,
I have mackie srm 450 the tweeter is working perfect but the woofer is playing very low according the tweeter,
something problem with the amplifier I think,
I measured the low unit circuit I haven't find something problem,
can help me someone please?

[Jazz P Bass]

Is that model a SRM450 or a SRM450/2
They are totally different amplifiers (internally)

[djdamianos]

hi,its simply srm450

[Jazz P Bass]

Mackie SRM 450 SM

Here is the service manual & the schematic.
Check the output transistors for shorts.

[djdamianos]

ok thanks a lot ill measure the output tranzistors with my multimeter

[Jazz P Bass]

I guess the first item should have been the speaker.
By 'gently' pushing on the cone you can tell if it moves freely or if there is voice coil rub evident.
The SRM450 schematic for the preamp shows the expected db gain or cut expected at each stage .
By following the signal through the preamp you will be able to tell if it is a pre or a power amp problem.

[djdamianos]

no the woofer is brand new and tested with another speaker,maybe the problem is from preamplifier at the stage of LF because some times the sound of woofer is distortion said to me the previous owner.
Anyway now ill go to check the output of LF exit componets,
thanks for your usefull advises