Sibilance when playing canned music

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Hello all! I am a sound man in progress, learning from mistakes and lots of hours reading this forum.

I DJ and set up sound equipment for social country western dances at various locations near the university I attend. Lately I have been having a terrible time with sibilance in my music and I simply don't have enough experience to know what I'm doing wrong. I have done a fair amount of googling, but most of the advice has to do with mixing live vocals or creating mixes in a program.

I'll list the specifications for the sound system at the bottom of my post, however here is the general set up. The dances are in a basketball gym. Music purchased from itunes is played from a laptop at 70% volume and routed to the mixer through the stereo RCA in jacks. I usually set the channel fader about 3/4 of the way up, a little below unity. The main fader is about 1/3 up. L and R audio is then sent to the two powered speakers set 40 feet apart using the XLR out on the mixer. And that it! There's no real mixing going on. The problem I am having is that I have started to have some painful sibilance.

I have tried turning down the highs, but that has only made the lyrics muddy. I turned up the laptop volume until the VU lights are hitting right where they should, and then raised the channel volume fader and dropped the main fader. That helped some, but it was still bad and the music was muddy.

I am almost certain it is caused by operator error and not the equipment because I have used this exact same set up for previous dances in the same location and did not have a problem. The music format may be contributing, however I have used the same music files before with no issue.

What are common causes of sibilance when playing professionally produced music over a PA? Any advice anyone has would be appreciated. Thank you for helping a noob out!

Equipment used:
Yamaha MG12XU mixer
2 Peavey PVXp15-DSP 800W 15" Powered Speakers
Lenovo laptop playing music from itunes
No experience of PA systems playing from laptops myself but in my experience sibilance is often caused (or exacerbated) by common-mode noise generated by SMPSUs. Is the laptop running from its internal battery? If not, try running it without the external switching supply and see if that improves the sibilance.
Sibilance is not caused by frequency response issues. It is usually caused by high frequency ringing or presenting the high frequencies for longer than they should occur.

When you look at the spectrum it may show a boost in high frequencies depending on the type of analyzer. When using a Fourier based analyzer the problem will show up in the phase response. It depending on the analyzer may show up as the phase shift being 360 degrees.

I suspect the issue is with your high frequency loudspeakers. This can be caused by a Helmholtz resonator accidentally occurring near the energy source.

First step try a different loudspeaker system even at lower volume. If it goes away look for holes or depressions you can fill with fiberglass or even stuff Kleenex in them to test for the problem.

If it is not a loudspeaker problem get an outboard D/A as that would be another area of possible problems.

Odds on it is the Peavey loudspeaker and might be acoustic or in the internal DSP. I don't think you can do anything about the internal DSP.
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Could be lots of things, but you seem skeptical about the source.
Have you tried different digital files, that are known to be good/better?
Even to experiment with some ferrites over the cables to see if you can isolate it to one component would be worth a try.

The people I know that do that will use an isolation transformer for the low level components 120v supplies.
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I have a real problem with sibilance on very compressed music, in some places where the vocalist is more dominant and the instruments are a bit lower. Some compressor settings seem to try and get max level no matter what's in the mix, torture if it's an "sssss".
Did you check the one knob compressor ref Turk 182^?
Wow! So much help! Thanks guys!

In regards to the inquiries about grounding and the laptop charger, I think I have dealt with that issue. The whole system is plugged in to the same power strip, a furman SS-6B, and all the plugs have ground pins and the strip is plugged into a grounded outlet. The laptop does not have very good battery life, and so it has to be plugged in. This has caused problems with humming, but we recently added a ground loop isolator to the line in cable and this fixed the problem. I tried the system with and without the isolator and it didn't seem to affect the sibilance however.

There is no EQ added in the system, besides the high and low adjustment knobs. The one knob compressors are only on the first 4 mic channels, and not on the stereo channel that we use as an in I believe, so I don't think that is the issue.

I am not all that familiar with DSP, besides knowing what it stands for. I believe I mislabeled the model of our speakers though, because they do not have the DSP interface, just jacks and a volume knob. They are kept at the school so I'll have to check when I am on campus tomorrow for the model. I pulled the model number from sweetwater because I know that is where the club bought them from. They look the same as the model I thought they were, except that they are plain Peavy powered speakers without DSP adjustments.

Concerning music, I have not tried using a lossless file, an oversight on my part. That is definitely an easy check I will do. However, we use the same music files each time and I know that we have not had a problem with causing sibilance until recently. I only took over sound last year because there was no one else. Prior to that the club had a sound man who knew what he was doing, and I never heard sibilance from his setups even though he was using the same music files. This is what makes me think I am doing something wrong.

In general, would you consider AAC from iTunes high enough quality for playing over a sound system? I know it is supposed to be better than MP3, though it is still lossy. I have not tried any type of live music as we don't have the equipment for that. We do use a shure mic for announcements which I have never had a problem with sound wise, though I think that is not a very good comparison.

Lastly, in regards to isolation transformers, do you think that is something I should look in to now that you know the ground and charger situation? I was under the impression that the Furman power strip was designed to help with that. Is there a way to test to see if a transformer would help besides just buying one? If I understand correctly, there are ones which are for the power plugins, and ones which go in-line with the XLR cables. Which one might help in my case?

Thanks so much again. I know a lot of this is elementary knowledge so I appreciate you all being patient with me as I learn.
well you've stated that you've tried with and without the isolator and there's no difference with the sibilance but does it affect the low frequency response?

if you loose bass what remains will seem dominated by what's left....
sibilance is a specific effect but the way your describing it i think your dealing with dominant treble and unfortunately the EQ facilities of the MG 12 are 10k shelving types and the knee is higher than your "sibilant" frequencies of interest.
beg, borrow or rent a 1/3 octave EQ put it inline with the mixers output and notch out the frequencies between 4 to 6k those are the typical offenders (can go as high as 8k but without hearing it who knows) that should remedy your problem or go down the rabbit hole of designing an inline notch filter if you like...
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The problem I am having is that I have started to have some painful sibilance.

You can probably isolate the problem using some powered computer speakers or headphones. Is the problem audible coming out of the laptop? If not, see if it is audible coming out of the mixer. If not, that leaves the speakers. Try a different source to feed the speakers to verify if they always exhibit the problem, etc. In other words, break down the problem into smaller problems which will narrow your search for the cause.
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Kaffiman is closest.
Your problem is not source, ringin g or anything of that kind but the cheesy compressor used.

Poorly setup ones, as he mentions, try to keep **everything** same level, no matter what.
Work reasonably when playing general music but burn through your ears with a vengeance when a solitary "sssssss" is present.

Older "good" compressors (think 80´s Rane and similar) added a "sibilance attenuator" or "de esser" switch or setting; later when Audio Products became a commodity and price became the main "Technical spec" that was dropped off or forgotten.

Best would be to get a real (hardware) compressor/limiter which includes that function; Plan B is to get a plugin.

Fine when recording, sort of "slow" if used for live vocals, but since you play Music from a Notebook it might do.

A couple de-esser plugins:



Notice they even offer a "Male-Female voice" setting :eek:

I guess you might process the Music program only through de-esser and leave live/stage Audio un processed .

In any case, apply less compression from the built-in one which obviously must be a very simplified (crude?) one.

Obviously a "single knob" compressor can NOT be adjusted except for amount of compression, everything else is rigidly preset.
De-esser plugins are a poor band aid. Best to record properly in the first place, second best with an existing recording is to manually correct the excessive esses on vocal tracks by automating volume and or EQ until each occurrence of excessive ess sound is made to sound natural. Last choice and worst sounding, but quick and easy, is a de-esser which is narrow band compressor at the ess sound frequency.
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“Using the same music files”, he said, not necessarily the same equipment. I’ve had MP3 rips that sound positively awful through some class D chip amps. One of my full range car amps seems to be rendered unusable with MP3. It really is that bad. The same files show no hint of problems with ordinary class AB amps or a better class D. Analog music through the former amp sounded fine as well. Something about the sampling frequencies just isn’t compatible, and something is mixing back into the audio band. It wouldn’t surprise me to see some sort of similar interaction going on here.
So it sounds like what you all are saying is I maybe jumped the gun a little trying to fix the problem and need to do little more work narrowing down the issue. I'll go through everything with headphones to see if I can narrow down the source of the sibilance better. That might help me know whether I should look for an EQ, isolator, mixer, something with the speaker cabinet, or a better sound source.

On the subject of the mixer EQ, the stereo channel only has a 2 band EQ, whereas the mic channels have 3 band. If I eliminate the laptop as the issue would it be worth using 2 mono channels as input instead of the stereo channel in order to have the 3 band EQ? Or is that still not going to be narrow enough to make a difference? Also, I may know someone that would let me borrow graphic EQ to test. If that fixes the issue, would that or a de-esser be a better option?

Regarding isolators, assuming I eliminate everything up to that point, is there anything I'm looking or listening for to tell if its an issue it might fix?

I don't think I ever explained the situation with the sound system. It is owned by a student club, The Country Western Dance Club. I was elected sound man and was briefly trained by the graduating sound man, however at the time I had never worked with sound so I spent most of the time just learning the basics. He has since graduated and moved far away, which is why he can't come and physically help. I did message him, but he didn't have particular ideas what was wrong without being able to actually look at it.

As always, thank you for all the help!
going through the components of the system is a good idea.

on the subject of EQ i would use channels with the three band eq for a better latitude of tonal control (don't neglect the channel pans!) and imho a 1/3 octave EQ is far and away more useful in allowing tonal tailoring in the various venues versus a dedicated de-esser. (you did say there's multiple locations?)

hopefully it's not something like a x-over problem or damaged hf driver how comfortable would you be in evaluating that kind of fault?
The mic channels with 3 EQs have more gain than the line input with 2 EQs. They may also be XLR inputs, whereas the line inputs may be unbalanced. Don't know about the particular mixer, but often the case.

With possibly the correct XLR adapters the laptop output might be usable though the mic inputs, but might easily overload them. It may be necessary to add an attenuator pad or turn the laptop volume way down. Since most software volume controls are not dithered, turning down laptop volume would probably mean loss of resolution.
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