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Mackie Thump 15A started "farting out" since...

S

selftitled907

Feb 2, 2011
247
1
Wasilla, Alaska
#1
To start I hope this is the right forum for this thread. Suppose it will get moved if not.


Well, I personally do all the sound for our band at soundcheck and have for over 2yrs now. All sorts of different bar sizes from cramped to larger outdoor venues. And this time after sound check, we all get up to start playing and as soon as we start in I hear a horrible cracking sound coming from all 4 monitors so I step out front for a moment (during a song) and stand in front of the front of house speakers and I can literally see the speakers moving in and out what looked like 2 inches back and forth at least. then I look at a monitor oding the same thing.

So when I finally get everyone to stop playing and excuse the crowd with electrical issues, I let everyone in the band know that we probally just smoked our entire PA. The sound coming out was only describable as a huge farting sound, with a little bit of static sound mixed in. but now it wont go away.

All this story so that I can ask if anyone knows where exactally the problem might be. i opened up all 4 speakers in the front to find absolutly no tear in any of the speakers which suprised me. The 2 York 15s/horn (same as mackies just not powered) Sound a lot better but still fart just takes more to get em to that point. The mackies im kinda hesitant to open up cause they are powered. But any ideas would be greatly appreciated.

I understand that to fix all 4 speakers im lookin at around 400 bucks....and thats if i do it myself. I was told it was probally the magnet/spring that are behind the speaker cone but I have no real experience in this kind of thing. So what I'm really looking for would be...

a. Where does it sound like the problem would be based on what I have told you?

b. What would be some decent replacements.

c. If I'm going about this the wrong way and/or you need more information to get a good answer to me please let me know.

Thank you all TBers for taking the time to read this and all your answers are appreciated. Thank you in advance for the advice/suggestions.
 
#3
Something weird is going on if both monitors and mains started doing it at the same time. Maybe the problem isn't the speakers. Have you tried a different mixer? I believe you can plug a microphone directly into the thumps. You might try it and see how it sounds. WARNING- Be sure that if there is a mic/line switch that it is in the right position and start with the speaker volume all the way down and bring it up SLOWLY.
 
#4
Check and make sure you used the right power cords to plug in everything. I've always just grabbed one and plugged it in, even if that meant scalping one from my computer or printer. At a gig last weekend I thought my tweeter was blown on one of the monitors. Switched power cables and voila, no problem. The voltage rating is at the female end where it plugs into your amps/board.

This may not be your problem but hopefully so, since it's a cheap fix.
 
#5
modulusman said:
Something weird is going on if both monitors and mains started doing it at the same time. Maybe the problem isn't the speakers. Have you tried different a different mixer? I believe you can plug a mictrophone directly into the thumps. You might try it and see how it sounds. WARNING- Be sure that if there is a mic/line switch that it is in the right position and start with the speaker volume all the way down and bring it up SLOWLY.
Click to expand...

You can plug a mic directly in.
 
#6
Like stated in the original post, there wasnt enough power once everyone started playing and the amps started pulling seriouse juice. I think that was the problem, either way the mains (yorks and mackies) fart constantly.

I appologise my original post was a bit losely put together. Im pretty certain that power was the issue that caused the farting. Since that happened they have started farting out quite often.

The speaker cones arent torn and im sure at least 3 of the 4 tweeters (horn speaker) are still intact. Which leaves me to believe that something is wrong with the speakers i just odnt know where to look.
 
#8
Hi.

Mains power, or more precisely the lack of it, can't blow a speaker.

It can however blow a badly designed amp, which in turn blows the speaker.

IMLE, the modern drivers are less likely to crease or tear the cones than the vintage ones are, even when the X-Max is exceeded. Feeding the drivers sine signal through a known good amp is the way to determine whether they're working as they shoul or not.

I don't know the topology of the said amps, but hum/static/early break-up are often signs that either side of the output device banks have lost a device and thrown the bias off. Or one or more devices leak the rail voltage into the output.

Since these are SS, measuring the DC at the speaker connections is easy. There should be none.

In any case, a trip to a tech, or a once-over from a competent El guy can save a lot of grief and money in the long run.

Regards
Sam
 
#9
modulusman said:
Did you try plugging the mic into the thump directly or not? BTW the thumps are a terrible choice if you need lots of volume. The maximum SPL is only around 115db. A Mackie 450 would be twice as loud.
Click to expand...


Yes we have plugged mic's directly into the mackie and they work fine....its when its getting the full spectrum from the entire band that they start acting up.

Im also now aware at how terrible the Mackie's are for overall volume but they carry the low end really well considering we dont use subs. But the yorks carry the volume and the mackie's kind of act like cheap subs.

Either way the mic alone isnt doing anything that it shouldnt, even screaming its fine. I keep my bass very low in the FOH mix to help back off of that fine line we have now before we get farts as well as have been turning down the drums. (roland electric kit) Unfortunatly we have gigs coming up and might have to use a different PA if i cant fix these fairly easy.
 
#10
T-Bird said:
Hi.

Mains power, or more precisely the lack of it, can't blow a speaker.

It can however blow a badly designed amp, which in turn blows the speaker.

IMLE, the modern drivers are less likely to crease or tear the cones than the vintage ones are, even when the X-Max is exceeded. Feeding the drivers sine signal through a known good amp is the way to determine whether they're working as they shoul or not.

I don't know the topology of the said amps, but hum/static/early break-up are often signs that either side of the output device banks have lost a device and thrown the bias off. Or one or more devices leak the rail voltage into the output.

Since these are SS, measuring the DC at the speaker connections is easy. There should be none.

In any case, a trip to a tech, or a once-over from a competent El guy can save a lot of grief and money in the long run.

Regards
Sam
Click to expand...

thank you for this input Sam. however im a little confused. does this mean I "should" check the DC at the speaker connections? just to be safe? is this standard practice for troubleshooting speaker issues? Like I said, Im new to this kind of repair and want to do it myself if Im capable. Anyhow, any further explanation would be appreciated.

Oh yeah also, the reason I say power, or lack there of, was the problem cause when I went to check where we had power from....it was 1 outlet with 2 extension cords plugged into it. I removed 1 of them and put it on a dedicated outlet (1 outlet for the 1 breaker) this did fix all issues that we had for the time being but we still had to turn everything down because the farting didnt get fixed. Not sure if this bit of info will help but thats how it went down.
thanks,
Gabe
 
#11
Hi.

selftitled907 said:
thank you for this input Sam. however im a little confused. does this mean I "should" check the DC at the speaker connections? just to be safe? is this standard practice for troubleshooting speaker issues? Like I said, Im new to this kind of repair and want to do it myself if Im capable. Anyhow, any further explanation would be appreciated.

Gabe
Click to expand...

You're welcome.

Yes, You should check the if there's any DC present in the amplifier outputs. It's not as much a speaker troubleshooting method as it's an SS amplifier troubleshooting method. Any DC in the output will manifest itself as reduced performance of a speaker though, as the cone travel is reduced on either end. Obviously.

Most if not all modern amps do have a protection circuit that detects any DC and shuts the amp down if any is present though. It was a more common problem back in the stone ages ;). Pretty rare nowadays.

Just vocals are about the worst diagnosing signal one can feed into a SR system, other than for determening whether the system is dead or not. A test signal of some sort or even just mp3 music is way better. IME anyway.

Regards
Sam
 

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