Oddity at sound gig tonight

Hi folks:

So tonight I'm running sound at the local folk club and since their main mixer is out on a different gig I bring in my 12-in Yamaha board. I'm running through a Rane 23-band EQ and a Parasound power amp (via transformer). I plug everything in and turn it on, and say my usual One-Twos through the mic, and it sounds like somebody has cranked the treble way the hell up. (I'm using an E-V RE15 microphone, which is pretty damn flat.)

So I finish setting up, and the musicians get there and start talking and doing sound check, and it's still sounding bright as hell. I check the house curve -- it's absolutely standard. So I shrug, turn the treble EQ down on the channel strips, we finish sound check and I go drink coffee.

Showtime comes...and the brightness is almost gone; by the midbreak it's completely gone. And it stays gone for the entire second half of the show.

Look, I know gear takes some time to warm up when it hasn't been used for a while. But I used the Yamaha two weeks ago. Do the caps deform that fast??

I've heard stuff like this happen when I hadn't used the Yamaha in several months, but not when I'd used it 2 weeks ago, fer cryin' out loud.

Weird. But I know what I'm burning in for 24 hours before the next time I use it.

Peace,
Paul

(PS. Perhaps the problem was the Parasound, but I *think* they use that pretty regularly. And I know the Rane stuff is used every weekend.)

Quite impossible for even one cap in the Yamaha to do that.  If a rail starts to go you will lose headroom at all frequencies.
Best to look towards the EQ or Parasound, though even an intermittent contact on a PCB would most likely affect only one channel, and you are stereo, right?
It's always tough live!
Mike

Weird!

What speakers where you using? Were they 2-way boxes? Maybe the issue was in the crossovers/drivers? Did all speakers seem to sound the same?

Were there any on stage monitors as well? Did they sound similarly bright?

Did you try listening to your mixer on headphones - did it sound bright?

Did other people notice the unusual  brightness? Maybe your ears were having a "freakout" - pressure imbalance or fluid or something? - i could maybe believe that for one ear, but both going south at the same time, in the same way seems very unlikely!

OR.... Maybe all the fans raised the temperature and humidity??!  ;D

http://www.prosoundweb.com/article/print/in_the_heat_of_the_night_the_thermodynamics_of_a_rock_show

If the Parasound is rarely turned on, I could imagine it having a gross distortion issue during a long settling time after start up, which might translate as excessive brightness through PA speakers.  It at least seems like the most likely culprit. 

The Dave Rat reference is probably good for what to expect from big dog live sound gigs.

The meat sacks in the room, that weren't there during sound check, and temperature/humidity changes will make incremental differences, but nothing as dramatic as you appear to be describing.

I am not not familiar with the exact models you used, but would not generally suspect the Yamaha (or anybody's) mixer for such dramatic spectral shift. Likewise, RANE gear is well respected and unlikely to vary as you describe.

I am not familiar with Parasound amps, and from a quick google they appear to be Hifi not sound reinforcement amps, not that there should be a significant difference in nominal performance. John Curl is pretty well known in deign circles, while again not professional SR (AFAIK, and I have not been that active in design for live SR for years).

If you suspect the Yamaha, like it appears you do, it should be pretty straight forward to test it, before the next gig. Something that audible should be easily measured. This is not normal behavior for even a hifi amp (IMO) so perhaps something faulty to troubleshoot. I like the suggestion of cans,, often a pair of  600 ohm cans , can be plugged into sundry line level audio outs, at least in a quiet environment, not in a loud room, where you would need closed back, usually lower Z cans, that could load outputs.

Good luck..   

JR

haima said:

What speakers where you using? Were they 2-way boxes? Maybe the issue was in the crossovers/drivers? Did all speakers seem to sound the same?

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Yes, they did. E-V Sx100s.

Were there any on stage monitors as well? Did they sound similarly bright?

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No monitors that night.

Did you try listening to your mixer on headphones - did it sound bright?

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Nope; I didn't bring my cans with me. Next time I will.

Did other people notice the unusual  brightness? Maybe your ears were having a "freakout" - pressure imbalance or fluid or something? - i could maybe believe that for one ear, but both going south at the same time, in the same way seems very unlikely!

Click to expand...

Yes, the guy who was being my assistant engineer heard it too, and he heard when it slowly went away as the first set went on.

OR.... Maybe all the fans raised the temperature and humidity??!  ;D

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All eleven of them? Plus one staff person and the two engineers, in a room that seats 100. This was not one of Focal Point's more successful concerts.

Peace,
Paul

lets map what we know so far

you had a yamaha mixer, ev speakers, an ev mic, a rane graphic eq  and a parasound power amp.

before the show the entire set up sounded overly bright.

By the time the show started the the high frequency started to drop in level.

There are many factors involved in this that could be a cause.

Live sound is tough in the fact you only get one shot to do it.

is it possible you popped/damaged both HF drivers/tweeters?

The "slow fade" nature of the fault is definitely strange...!

Both sides (L/R) seemed to be acting the same? Was the system running in true stereo or were the two speaker boxes running off one mono signal?

How many sources (Mics/DIs) were you running - if it was just one mic, perhaps the problem lay there? If there was a handful then the fault must have been upstream somewhere...

Are you likely to be mixing there again in the near future?

A somewhat related story: I mixed a show in Malaysia a few years ago - the FOH rig was supposed to be a stack of Nexo PS15s + subs. We got there to find boxes that LOOKED like PS15s but were in fact "clones" - same shape boxes, but when you pulled the front off they had random, cheap drivers in them. Incorrect Processors. Eeek. Sounded terrible. EQed to the hilt, which ate up whatever headroom there was....

During the show the the whole PA limited and faded in and out on the left and right, each band - sub, mid, hi independently. Amps and processors going into limit and thermal overload, then recovering one after the other. Mixing was like surfing a wave of frequencies - one second you'd have all subs and only HIs on the left, then the next minute you have only midrange, then for a moment you'd have everything, then you'd loose the subs.. etc. CRAZY. One of the weirdest shows ever to mix. The kids didn't seem to mind! We were told we were the first western band play there since Fugazi in '96, or something...  :

pucho812 said:

lets map what we know so far

you had a yamaha mixer, ev speakers, an ev mic, a rane graphic eq  and a parasound power amp.

before the show the entire set up sounded overly bright.

By the time the show started the the high frequency started to drop in level.

There are many factors involved in this that could be a cause.

Live sound is tough in the fact you only get one shot to do it.

is it possible you popped/damaged both HF drivers/tweeters?

Click to expand...

Nope. I've worked that room a lot over the years, and know what it usually sounds like. The brightness at the beginning of the night was the abnormality; when it faded, it faded to a good normal balance for that room (a good-sounding place). And I worked the same place two days later with a different electronic setup (same speakers, but just running spoken word through them via an E-V RE16 and an E-V Entertainer head). The speakers are fine.

Unfortunately, I won't be using the Parasound rig again for a few months. I may have the Yamaha out before then, though, for one of our band gigs.

Peace,
Paul

My $.02... was it a gain in treble or a loss of bass?  I had an old crown amp i used for a PA rig that would occasionally do something similar.  But it wasnt an apparent gain in treble, the bottom end just kinda not making thru like it should and made everything sound too bright. (same deal though, after a while of being on, it would even itself out)  The amp blew up on me less than a year later, had it completely repaired and never had the problem again.

Gain in treble; I heard a whole lot of sibilance that wasn't supposed to be there.

Imperfect bias leading to crossover distortion, settling into proper bias with warmup?

Peace,
Paul

pstamler said:

Gain in treble; I heard a whole lot of sibilance that wasn't supposed to be there.

Imperfect bias leading to crossover distortion, settling into proper bias with warmup?

Peace,
Paul

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Not likely. Crossover distortion is only occurring at exact transition from + to - swing, so it pretty much becomes inaudible as signal levels increase beyond pretty modest levels.

The bass dropping out could be an intermittent bad DC blocking, or gain leg capacitor.  Not a very common failure to be intermittent but stranger things happen. 

JR

JohnRoberts said:

pstamler said:

Gain in treble; I heard a whole lot of sibilance that wasn't supposed to be there.

Imperfect bias leading to crossover distortion, settling into proper bias with warmup?

Peace,
Paul

Click to expand...

Not likely. Crossover distortion is only occurring at exact transition from + to - swing, so it pretty much becomes inaudible as signal levels increase beyond pretty modest levels.

Click to expand...

Well, pretty modest levels is what we're talking about here; I first heard the problem while saying my one-twos into a mic plugged into the board for checking. I heard it during the sound check -- we're talking acoustic duo, man and woman singing and each playing a guitar. Audience = 11 customers + 3 club staff. (Bad night.) The SPLs were modest enough that when the woman started playing the mountain dulcimer I pulled the fader on her instrument mic down to zero; it was plenty loud enough to match the man's guitar and the two voices. I'd guess I was topping out at about 0.25W average power. (The Sx100s have about 98dBSPL sensitivity at 1W 1 meter, and I'd guess my average level would have been 92dBSPL up on the ceiling a meter from the speakers. A lot less, of course, in the seats.) That sounds like a place where, if there was crossover distortion happening, it could be audible.

The bass dropping out could be an intermittent bad DC blocking, or gain leg capacitor.  Not a very common failure to be intermittent but stranger things happen. 

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The bass didn't drop out at any point. It just sounded like the treble got boosted in the sibilance region. After they'd been performing about half an hour it had disappeared and the system sounded normal again.

I've got another Parasound sitting here that I haven't fired up in about 6 months. Maybe I'll plug it in and run a quick series of 1W HD measurements in the first few minutes it's on.

Peace,
Paul

Sounds like that could be a possible cause - It's an unusual problem, normally sound reinforcement amps have more problems due to hitting their upper headroom.... not problems due to hanging down in the crossover region! ;D

I have done the odd FOH gig where you end up pulling a fader all the way down...  I once mixed vintage australian rocker, Billy Thorpe (RIP) at a small regional winery - dinner and show kind of thing - the show was supposed to be "acoustic".... he rocked up with two amp stacks and a pile of pedals. Proceeded to rip the heads of the first row of wine sipping retirees - I got quite a few dirty looks that night, dispite having every fader at -inf apart from his vocal  :