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Author Topic: Frequency Drop Off  (Read 1069 times)

Paul G. OBrien

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Re: Frequency Drop Off
« Reply #10 on: April 04, 2021, 04:08:55 pm »

Sounds like some methodical troubleshooting will be required.

That is an understatement, virtually every component in your setup may be a contributing factor including your mixing technique.

If this problem manifest and then corrects itself like a switch being thrown in and out but without anybody touching anything PA related then this is most definitely a hardware problem, but it could be anything from anywhere in the signal chain from a mic to the mic cable to a dodgy connector or a loose ribbon cable or dirty pot in the mixer to a cold solder joint on a circuit board in the powered speakers.

As for how your mixing technique plays into this, my first hand experience with these MG series mixers indicates they don't have much headroom, mixing a full band on one of these requires all inputs remain solidly in the green because the combined signal level will easily overload the output bus. Things just start to sound congested and brittle when the board is overloaded, I can't say I hear it as a drop in level it just gets dirty sounding a bit too easily.
As a former Markie Thump owner I can also say these are definitely a potential source of your problem. The boxes I had suffered blown drivers as well which interestingly presented early on with random drops in output level. In my case it was the woofers that died but with a 2khz crossover they also contribute quite a lot of mid output.
IMO these boxes are marginal for recorded music playback at moderate levels and would be quite unsuitable for live sound applications, I remember being quite underwhelmed the first time I heard 4 of these being used for a DJ event in a high school gym(with subs), they just didn't produce much output and even the DJ wanted more mids. They are processed with a music playback friendly scooped mid response(even when set flat), and the 1000w rating is a hilarious over exaggeration.. I doubt there is really more than 250w available so it's all too easy to push them into limiting.

So bottom line is you have some work to do, you need to borrow or rent another board and speakers and either buy or borrow a cable tester to check the health of your cable inventory, setup your rig and try to replicate the problem and then start swapping things. You have to be methodical and go though the signal chain from mic to speaker one channel at a time, wiggle connections, exercise controls, leave the equipment on for a day or two to see if heat is a contributing factor. If you can setup a second PA.. even just a small mixer and a single powered speaker you can quickly check to see if your mics or cables behave the same on that system.

If you can isolate the problem and say for example it turns out to nobody's surprise be the speakers, then I'm sure the consensus would be to cut your losses and upgrade to something better. There is a whole world of better out there in terms of powered speakers but that will require investing some good money, you won't get appreciably better results with entry level speakers from any manufacturer.
« Last Edit: April 04, 2021, 04:13:18 pm by Paul G. OBrien »
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Aaron Baxter

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Re: Frequency Drop Off
« Reply #11 on: April 06, 2021, 12:09:27 pm »

Sounds like some methodical troubleshooting will be required.

First up, find another way of getting signal directly into the speakers (FWIW, having worked with them, I'd advise replacing them asap anyway). Phone/laptop is usually a good place to start. Verify whether or not the speakers themselves are working properly without the mixing desk.

If they're working fine, on to step 2: the mixing desk. If I had to bet, I'd say it's the likely culprit. I don't know what the storage conditions have been, but it sounds to me like dust/moisture in the pots and faders could be the cause of your problems. Play music from the phone/laptop/whatever into the problematic channel(s). Figure out if it's just some of the channels, or all of them. Try the headphone output as well as the main outputs feeding into the Mackies (which you've verified are working fine).

The mics may be the issue. I've heard of saliva build-up seriously degrading a mic's performance, which makes sense: if the internal foam becomes saturated, the HF performance will be very different. You can check easily enough by taking the grille off and poking a finger inside to see how the foam's holding up.
To fix that in the future, external foams swapped out occasionally would likely help.

Let us know how you get on.

Chris

Chris/all,

Thanks for the troubleshooting ideas. 

Turns out it was indeed the mics.  I ran music through one of the channels and it sounded pretty ok (mind you the EQs were set for specific singers vocals) so I replaced them with SM58s and that solved most of the issue.  The rest I was able to EQ out on the board/speakers.  Granted the board still has other issues like inconsistent volume levels depending on what mood it's in, and apparently the Thumps are not popular on the forum, but for now it's tolerable.
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Mike Caldwell

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Re: Frequency Drop Off
« Reply #12 on: April 06, 2021, 11:52:16 pm »

Chris/all,

Thanks for the troubleshooting ideas. 

Turns out it was indeed the mics.  I ran music through one of the channels and it sounded pretty ok (mind you the EQs were set for specific singers vocals) so I replaced them with SM58s and that solved most of the issue.  The rest I was able to EQ out on the board/speakers.  Granted the board still has other issues like inconsistent volume levels depending on what mood it's in, and apparently the Thumps are not popular on the forum, but for now it's tolerable.

How many mics are you using?

You said about 70% time things sounded muffled. When the system would start working was it just all at once it popped on so to speak and all sounded good instantly for sounding bad or was it one day it sounded bad and the next day everything was working?

Did you ever play recorded music back through the system when the vocal mics were sounding bad?

Aaron Baxter

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Re: Frequency Drop Off
« Reply #13 on: April 09, 2021, 07:11:02 pm »

How many mics are you using?

You said about 70% time things sounded muffled. When the system would start working was it just all at once it popped on so to speak and all sounded good instantly for sounding bad or was it one day it sounded bad and the next day everything was working?

Did you ever play recorded music back through the system when the vocal mics were sounding bad?

It would generally be when you turned the board on.  It seems to be moody but with the new mics it's providing a much cleaner input so it sounds better.  The sound most all of the time was either all live or all recorded and the rare times it was mixed it wasn't acting up (that I can recall that is).  It seems to be bad mics exasperated by the board because it's still not as clean and clear on the 4 mic channels.  I could play musical channels, but IMHO the game isn't worth the candle since I pray in a few months I can replace it with an X32.  I've had all the channels sound muted/muffled at one time or another so I'm leaning toward the preamps going out in the channels.  I'll rebuild the board, if possible, as a spare and for fun (lol) after it's replaced. 
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Mike Caldwell

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Re: Frequency Drop Off
« Reply #14 on: April 09, 2021, 07:57:26 pm »

I'm guessing the board is the main problem. The Yamaha MG series is know for bad switches and becoming intermittent over time.

As for a digital replacement there are other options that work great and maybe faster to get up to speed on for a volunteer sound team (assuming this is for a church) than an X32.

Aaron Baxter

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Re: Frequency Drop Off
« Reply #15 on: April 12, 2021, 08:46:04 pm »

I'm guessing the board is the main problem. The Yamaha MG series is know for bad switches and becoming intermittent over time.

As for a digital replacement there are other options that work great and maybe faster to get up to speed on for a volunteer sound team (assuming this is for a church) than an X32.

Good to know about the sticky switches.  Whenever I get around to rebuilding it, I'll know where to focus.  Tonight wouldbhave been horrid with the old mics as the board was super driving the bass but at least we could hear the highs.  It is a church, and well, they were getting by with limited knowledge.  Thankfully I do have more experience than others here but am by no means an expert.

What I like about the X32 is I can setup some automatic presets that should work 96% of the time for most places we'll travel but gives me and whoever I can train a crazy amount of options.  It'll be a large curve for me too, but I'm computer systems engineer so it's a matter of merging my physical rack knowledge and my software knowledge.  Thankfully there are a tons of great YouTube vidoes, even one guy that's from a HoW and lots of other how tos on the x32/m32.
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ProSoundWeb Community

Re: Frequency Drop Off
« Reply #15 on: April 12, 2021, 08:46:04 pm »


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