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Thread: Mackie SRM450 v1 problem?

  1. #1

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    Default Mackie SRM450 v1 problem?

    Hi Guys ( and girls )
    newbie to the forum, i found it when i was trying to find and answer to a problem i have?

    i have a pair of Mackie SRM450s ( version 1 ) and have recentley been having a problem with one of them. the problem being, at the start of the night they both work fine...clear as a bell....but as the night goes on, one of them starts to crackle, then i lose all low end altogether (high end still works fine ). i usually work the same venue playing 1950s music so im not blasting them. in fact the peak light has never blinked on either of them...at all. i have the volume set at 12, o'clock and both the contour and low cut turned off. there is no sign of the thermal light coming on either.

    i had the speaker into an audio repair shop, who said he ran it off and on for a week, did diagnostics and couldn't find anything wrong with it? but still the problem continues.

    i was wondering.....because its fine at the start of the night and the problem starts usually around 2-3 hours into a gig, could it be a overheating fault? as i said neither the peak or thermal lights have ever come on? i have kept an eye ( hand) on the heatsink panel on the back and it never gets too hot.......i'm just baffled !

    I'm not technical at all, so be gentle with me...lol


    Cheers

    Rob

  2. #2

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    Hope this doesn't come across as teaching grandma to suck eggs, but my immediate thought would be cable. Try a new audio cable and see if that holds up. There's also a possibility that it could be a playout fault on one channel?

  3. #3

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    Hi Musicology,

    Thats been mentioned to me too. i mainly use a laptop for playing music and have tried both Line/Phono channels on my mixer. i also have spare cables ( 3 sets in fact ) and have tried them all to no avail. seems to me that if it were a mixer/ cable problem then it would be faulty from the off....not just 2-3 hours into a gig ( but i have been known to be wrong....frequently )

    But thanks for the reply, all hep is good help

    Rob

  4. #4

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    Quote Originally Posted by rockabillyrob View Post
    Hi Musicology,

    Thats been mentioned to me too. i mainly use a laptop for playing music and have tried both Line/Phono channels on my mixer. i also have spare cables ( 3 sets in fact ) and have tried them all to no avail. seems to me that if it were a mixer/ cable problem then it would be faulty from the off....not just 2-3 hours into a gig ( but i have been known to be wrong....frequently )

    But thanks for the reply, all hep is good help

    Rob
    Have you also tried swapping the outputs over (i.e. put the left speaker in the right output, and vice versa) ?

    Just to rule out mixer problems, sometimes when a mixer heats up it can behave differently so not always spotted from the off.
    Semi-Retired Multi Award Winning DJ

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  5. #5

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    I pretty much agree with all of the above but an easier way would be to run the speakers until the fault occurs then quickly (so as not to let it cool down) swap over the input cables at the mixer end, if the fault stays with the same speaker it rules out both the mixer and the cables. Next I'd remove the speaker grill from the faulty speaker and gently push the cone in and out looking out for the cone 'scraping' or showing 'drag' it should move freely, if it doesn't it could well be the speaker windings breaking down.

    If the cone seems to be OK swap over the amp modules, it's a pretty easy job assuming you have a decent cross head driver that fits the screws properly. If the fault moves with amp you have located the seat of the problem. The next step is obvious, find a repair shop that knows what they're doing (not all do)

    I've used THIS chap several times in the past without any problems and the amp is returned with an oscilloscope readout of the amps current performance. You can phone him and have a chat and seek his opinion before committing yourself to a repair, I've always found him to be helpful, but ultimately use your own judgment to his suitability.
    Inside every old person, is a young person wondering 'What The Hell Happened'. Tempus Fugit

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  6. #6

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    Quote Originally Posted by ppentertainments View Post
    Have you also tried swapping the outputs over (i.e. put the left speaker in the right output, and vice versa) ?

    Just to rule out mixer problems, sometimes when a mixer heats up it can behave differently so not always spotted from the off.
    Thats something i havent tried....i will do this weekend.

    Cheers

  7. #7

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    Quote Originally Posted by musicology View Post
    . There's also a possibility that it could be a playout fault on one channel?
    As ppents says That's kinda what I was saying

  8. #8

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    I wouldn't have thought the playout system was at fault as the OP says he loses the LF driver... unless the playout system cuts off at the same frequency (and roll-off order) as the Mackie!

    My first thoughts would be either heat and old solder joints, or, a loose cable inside. As someone has had the back off already I would assume they have checked the cables and connections (and cleanly re-seated them all), so it would leave me to think a dodgy joint on the circuit board. IIRC the HF and LF amp sections use separate power supply drivers (i.e. they're not run from the same voltage, the HF is a 'chip' amp if memory serves me correctly), so my first look would be at the LF PSU section.

    If you don't know about electronics (and the high voltages and shock potential) let someone who does do it. Personally don't know anyone in the Co Durham area, so can't suggest sorry.

    P.S. Did the repairer you took it to check the LF driver itself? It may even be a fault in that. I've had the 'tinsel' wires (that go from the connections to the cone) come adrift... took bloomin' ages to find that one!

  9. #9

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    I've turned up to a gig once & tested the PA only to find that there was no bass coming from one side. Turned out to be a duff XLR cable. Yes, I'd have assumed a dead short would do away with all the sound but no, apparently not (the active speaker amp must have a very high input impedance!).

    Anyway with the SRM450v1 if it's just the LF driver cutting out & not because it's going into protect mode (never rule out that the protection LED isn't working anymore!) it could be any number of causes. Dry joint in the active x-over circuits, the LF amp, the wiring to the LF driver and then the LF driver itself. Since you have a pair of them maybe you can try swapping amp modules from one to the other or even LF drivers & giving them a jolly good test.

  10. #10

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    Quote Originally Posted by musicology View Post
    As ppents says That's kinda what I was saying
    ahh yes..... i misread the post....i blame my age and eyes.

    call it a gut feeleing but i still feel its a speaker problem and not a cable/mixer problem. although i am willing to try any suggestions, and to make sure i'm going to retry the changing of mixer channels this weekend. if i can i'll try and get a video if the problem reoccurs.

    Rob

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