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[EMILIANO ECHEVERRIA ZAPATA]

More pics
https://mega.nz/#F!WgVC2BhR!3w7lBcuX8E_2-_qPK3Y93A

So the building mesures
10 meters wide
30 meters deep
4.64 meters high

Celing it's sheet metal, the construction al concrete and a walk of windows

Oh and we have about 500 people when its full

[Jean-Pierre Coetzee]

Looking at the way that system is setup and the response curve you have shown I would suspect that the horns are blown in those JBLs. Run a sine wave sweep through the system, 100Hz - 12kHz should be sufficient to notice if the horns are blown, if you hear any rattling at all during the sweep likely there is another driver also blown.

Make sure you always mute channels before unplugging things, also make sure you turn on and off the system in the correct order.

On:

1. Sound desk
2. Anything in between the sound desk and the amps(should be some sort of speaker processor/crossover&EQ combo)
3. Amps for speakers

Off

1. Amps for speakers
2. Anything between the sound desk and the amps
3. Sound desk

Don't worry about acoustics right now, there are a lot more problems with the system deployment but check that all the drivers are working first before we move on to the next steps.

[Lee Buckalew]

Looking at the way that system is setup and the response curve you have shown I would suspect that the horns are blown in those JBLs. Run a sine wave sweep through the system, 100Hz - 12kHz should be sufficient to notice if the horns are blown, if you hear any rattling at all during the sweep likely there is another driver also blown.

Definitely test for driver problems but I would suggest not jumping straight to "driver is blown".  Think about a driver not producing sound that you can hear and what might cause this.  Driver damage may well be the case but I have also seen insects nesting in horn throats cause what seems like a blown driver.  I have also seen cabinets that were stored and transported, uncovered, face up, collect a lot of debris in the horn throats and partially block the output.

I am not trying to correct anyone here, just reminding the OP that there may be more than one possible cause for the same result.  Don't get tunnel vision when trouble shooting.

Lee

[Jonathan Johnson]

Celing it's sheet metal, the construction al concrete and a walk of windows

The ceiling appears to be corrugated metal with a fire retardant coating. This should have reasonably good acoustic dispersion (and possibly absorption) properties, so I wouldn't expect it to be a problem.

A concrete floor is a very effective reflector for sound, as is a wall of windows. Human bodies also absorb sound well, so when the room is full, the floor shouldn't be too much of a problem.

If you have parallel flat surfaces (opposite walls), those can create standing waves which generally end up sounding like low-frequency feedback. Breaking up these surfaces to create some dispersion can help control the standing waves. So can absorptive materials, but that can make a room seem "dead."

[Jean-Pierre Coetzee]

The ceiling appears to be corrugated metal with a fire retardant coating. This should have reasonably good acoustic dispersion (and possibly absorption) properties, so I wouldn't expect it to be a problem.

A concrete floor is a very effective reflector for sound, as is a wall of windows. Human bodies also absorb sound well, so when the room is full, the floor shouldn't be too much of a problem.

If you have parallel flat surfaces (opposite walls), those can create standing waves which generally end up sounding like low-frequency feedback. Breaking up these surfaces to create some dispersion can help control the standing waves. So can absorptive materials, but that can make a room seem "dead."

That wall looks like drywalling to me and the other end looks like windows, neither are very good reflectors of sound. I really doubt acoustics is a problem.

[Mac Kerr]

That wall looks like drywalling to me and the other end looks like windows, neither are very good reflectors of sound. I really doubt acoustics is a problem.

Huh??? Both drywall and glass are very good reflectors of sound, and often the cause of strong "slapback" off rear walls of performance spaces. What are you trying to say?

Mac

[Jean-Pierre Coetzee]

There's no horn pointed there and they are invisible to low frequency sound, has anyone looked at the pictures he posted.

I know they can cause slap, he has two cheap jbls flown horizontally so effectively 60° horns which will never hit those side walls.

Acoustics is not the problem here regardless because his "measurement" only shows a rolloff above 1kHz despite what he said.

If there was an excess of hf by all means use treatment on those walls, diffusion would still not solve the problem.

Yes they do reflect hf but in his situation it makes no difference, there happens to be blinds over the windows as well so no that wall is acoustically neutral.

[EMILIANO ECHEVERRIA ZAPATA]

Looking at the way that system is setup and the response curve you have shown I would suspect that the horns are blown in those JBLs. Run a sine wave sweep through the system, 100Hz - 12kHz should be sufficient to notice if the horns are blown, if you hear any rattling at all during the sweep likely there is another driver also blown.

Make sure you always mute channels before unplugging things, also make sure you turn on and off the system in the correct order.

On:

1. Sound desk
2. Anything in between the sound desk and the amps(should be some sort of speaker processor/crossover&EQ combo)
3. Amps for speakers

Off

1. Amps for speakers
2. Anything between the sound desk and the amps
3. Sound desk

Don't worry about acoustics right now, there are a lot more problems with the system deployment but check that all the drivers are working first before we move on to the next steps.

Very good I'll do the frequency sweep and then check the horns for debree or insects

[Irvin Pribadi]

Emiliano welcome to this forum.

Do your ears agree with the measured results from your phone RTA app?
Before chasing down this issue based on an RTA screenshot, I'd like to hear what you think of the sound in general.

[Ken Webster]

I'll just add that it's best not to jump to conclusions about equipment because losses in other equipment can also affect the frequency response curve.  You need to do isolation testing to determine which component is faulty.  Simplify the signal path by bypassing components like the desk and the equalizer etc.  Swap out Amps and/or speakers for ones you have tested independently of the system and know are good.  Reconnect and retest one component at a time until you identify which component makes it sound bad.  We had similar sound curve issues and found the equalizer was the problem.  Fixed it with fader lube spray but did all the switches and trimmers on the board cleaned and reconditioned all the plugs and sockets with Deoxit.   All just normal regular maintenance stuff but it had been neglected for may years. So eventually went over the whole system in this way, also resistance tested every cable, re-soldered bad connections.  It sounds very good now but a lot of work.....

While testing the system like this is recommended as what you can do now (cheaply), given the timing of a problem occurring immediately on changing the room and if there were no changes to the system, I have to suspect altering the room may be the underlying issue or perhaps a contributing factor.

Regards Ken

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