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Author Topic: PA Speakers touch ceiling not as clear  (Read 2633 times)

Armando Ramos

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PA Speakers touch ceiling not as clear
« on: September 23, 2016, 02:50:10 pm »

Does placing PA speakers up against a hard-surfaced ceiling (see attached photo "close-up of main speaker”) cut some of the higher frequencies (5kHz and up)?

Reason I’m asking is my church had the ceiling tiles in the main auditorium over-laid with plastic decorative tiles (see attached photo "church and main speakers”) and ever since then both of my EAW fr129z main PA speakers aren’t as clear in the higher frequencies as they use to be. These speakers have always been up against the ceiling, ever since I took over sound at my church.

I did some measuring with SMAART and saw a downward cut in the 5kHz range, as if I had placed a Low Pass Filter at 6kHz. I tried fixing this issue with a parametric EQ by using a high-shelf gain increase at 6kHz to fill in the downward cut. Although this made the EQ flat in the 5kHz - 20kHz frequencies, I sometimes I get loud ringing sounds in those areas.

Is EQ the only way to fix this problem? What would you guys suggest?
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lindsay Dean

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Re: PA Speakers touch ceiling not as clear
« Reply #1 on: September 23, 2016, 03:27:49 pm »

You had some absorption with the old acoustic tiles,
allowing the horns to be against the ceiling,
now you have a reflection.
 causing arrival time differences between the original and
reflected output .
you will have to reposition/ tilt the mains to get back some clarity.
trying to jack up those frequencies will most likely cause  feedback
and reduce gbf .
« Last Edit: September 23, 2016, 03:30:00 pm by lindsay Dean »
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Mac Kerr

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Re: PA Speakers touch ceiling not as clear
« Reply #2 on: September 23, 2016, 04:23:29 pm »

You had some absorption with the old acoustic tiles,
allowing the horns to be against the ceiling,
now you have a reflection.
 causing arrival time differences between the original and
reflected output .
you will have to reposition/ tilt the mains to get back some clarity.
trying to jack up those frequencies will most likely cause  feedback
and reduce gbf .

On the other hand, because the speakers are so close to the reflecting surface the path length difference will be minimized, minimizing the effect.

Mac
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Ivan Beaver

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Re: PA Speakers touch ceiling not as clear
« Reply #3 on: September 23, 2016, 08:32:16 pm »

Have  you measured in different locations?

Does the response change?

Do the notches in the response change freq?

This can give you an idea if it is a reflection or not.

If it changes, then it is a reflection.

EQ WILL NOT fix it.  It will only make it worse for most people
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Armando Ramos

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Re: PA Speakers touch ceiling not as clear
« Reply #4 on: September 24, 2016, 12:06:15 am »

Have  you measured in different locations?

Does the response change?

Do the notches in the response change freq?

This can give you an idea if it is a reflection or not.

If it changes, then it is a reflection.

EQ WILL NOT fix it.  It will only make it worse for most people

I'll measure in different locations and part my findings.
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Stu McDoniel

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Re: PA Speakers touch ceiling not as clear
« Reply #5 on: September 27, 2016, 08:02:11 am »

Does placing PA speakers up against a hard-surfaced ceiling (see attached photo "close-up of main speaker”) cut some of the higher frequencies (5kHz and up)?

Reason I’m asking is my church had the ceiling tiles in the main auditorium over-laid with plastic decorative tiles (see attached photo "church and main speakers”) and ever since then both of my EAW fr129z main PA speakers aren’t as clear in the higher frequencies as they use to be. These speakers have always been up against the ceiling, ever since I took over sound at my church.

I did some measuring with SMAART and saw a downward cut in the 5kHz range, as if I had placed a Low Pass Filter at 6kHz. I tried fixing this issue with a parametric EQ by using a high-shelf gain increase at 6kHz to fill in the downward cut. Although this made the EQ flat in the 5kHz - 20kHz frequencies, I sometimes I get loud ringing sounds in those areas.

Is EQ the only way to fix this problem? What would you guys suggest?
Place a diffraction panel or an absorption panel on the ceiling where the waveform first hits the ceiling or build a shelf and flip them over with the horns on the bottom.
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David Allred

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Re: PA Speakers touch ceiling not as clear
« Reply #6 on: September 27, 2016, 03:10:23 pm »

Does the 5Khz+ return when you set the speakers on the ground?
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Armando Ramos

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Re: PA Speakers touch ceiling not as clear
« Reply #7 on: September 27, 2016, 03:32:53 pm »

Does the 5Khz+ return when you set the speakers on the ground?

I haven't tried this yet but will do so soon.
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Armando Ramos

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Re: PA Speakers touch ceiling not as clear
« Reply #8 on: September 27, 2016, 03:33:52 pm »

Place a diffraction panel or an absorption panel on the ceiling where the waveform first hits the ceiling or build a shelf and flip them over with the horns on the bottom.

Thanks for the tip!
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ProSoundWeb Community

Re: PA Speakers touch ceiling not as clear
« Reply #8 on: September 27, 2016, 03:33:52 pm »


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