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Eq-ing FOH

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Foca_Dacian View Drop Down
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    Posted: 24 September 2017 at 5:58pm
What type of an eq curve is needed for a good sound?

I have flattened a sound system I use for live sound with an RTA mic and pink noise,but it did not sound good.There was a lack of low frequencies, and also it sounded harsh in the high frequencies.

I have to mention I am new in the live sound bussines , did not go ta any specialised school and certain things I need to learn along the way and at the moment I do live sound for small bands in small indoor gigs.

Does RTA measurement take in account the Fletcher and Munson curves and it's linearity is based on that?
If not,after RTA is done and the system is flat ,I should  substract and add frequencies acording to the spl of the system and the way I percieve the sound at that level ?

I would apreciate some material or some links to read and better understand the steps I have to take to obtain a good sounding FOH.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jacethebase Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 7:10pm
Do you own the Yamaha Sound Handbook?

How are you using your RTA? How do you have it setup?
www.wedding-production.co.uk

www.stage2sound.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 7:19pm
You tune the system ‘flat’ and then tone it to taste for he mixing engineer. I prefer a flat start point and to add tone via channel strip and mixing personally but not all do. Likewise the tone will vary depending on the overall SPL you expect to run at. So the answer to your question is ‘it depends’
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 7:33pm
Originally posted by toastyghost toastyghost wrote:

So the answer to your question is ‘it depends’

The Beaver is strong with this one.....  Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FrederikMA Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 10:03pm
Beaver's apostles are right. It depends. That is not to say it's not worth studying WHAT it depends on.
Unlike a speaker manufacturer, who resists to disregard all the things a preset depends when asked to do one for simple plug and play, a mix engineer has to develop a set of tools and guiding rules when facing real world scenarios.
The Fletcher Munson is empirical derived and rests on assumptions and disregards other factors like time exposure (see ear fatigue) and signal type. Multiple curves has been developed for our ears' sensitivity to various kinds of signal. Knowing what the program material will demand from our systems is to me essential when designing the system
Best regards, Fred
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 10:24pm
If one was going to buy a book to help in this area would the Yamaha book be the weapon of choice?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pasi Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 10:43pm
My favourite answer has been soon 10 years " It depends on application"

FOH doesn't need any EQ, if the system is good and placed correctly.

Using RTA, assuming some phone program or similar, which doesn't use reference signal is waste of time as it can't tell you the important information. Hence you need a proper FFT system like Systune.

After that you need to know what you are doing and what your aim is.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 24 September 2017 at 11:16pm
Originally posted by Foca_Dacian Foca_Dacian wrote:

What type of an eq curve is needed for a good sound?
That is a very subjective question.

Originally posted by Foca_Dacian Foca_Dacian wrote:

I have flattened a sound system I use for live sound with an RTA mic and pink noise,but it did not sound good.There was a lack of low frequencies, and also it sounded harsh in the high frequencies.
Yes sounds about right.

Originally posted by Foca_Dacian Foca_Dacian wrote:

Does RTA measurement take in account the Fletcher and Munson curves and it's linearity is based on that?
No it does not.
Originally posted by Foca_Dacian Foca_Dacian wrote:

If not,after RTA is done and the system is flat ,I should  substract and add frequencies acording to the spl of the system and the way I percieve the sound at that level ?
Yes it gets very personal after that. Human hearing is most sensitive around 4khz and my ears are very sensitive around there after many years of abuse so I tend to apply a broad but shallow correction centered at that frequency, and then depending upon the high frequency response of the system I EQ so that the high end response slopes off gradually out as far as it naturally goes, and then the subs are boosted about 3-6dB across the board.  These adjustments make the system pleasant to listen to with just about any music type but note that each genre will sound totally different and I don't try to correct for that. Classic rock sounds thin compared to modern cRap and hip-hop but it is supposed to, that is the way it was recorded and how it sounded back in the day.



Edited by Conanski - 24 September 2017 at 11:26pm
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bob4 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 25 September 2017 at 3:07am
Originally posted by Foca_Dacian Foca_Dacian wrote:

I have flattened a sound system I use for live sound with an RTA mic and pink noise

There's your problem. You have used the wrong measurement signal, or haven't understood how to use that signal. 

Look at your pink noise signal in an RTA before it leaves the PC, or play back pink noise from an audio test CD, or test file into an RTA (hardware or plugin, whatever you use).




Originally posted by wikipedia wikipedia wrote:

Pink noise or 1f noise is a signal or process with a frequency spectrum such that the power spectral density (energy or power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave (halving/doubling in frequency) carries an equal amount of noise energy. 


Oops, that doesn't look flat, does it? Ouch 




But what about this:




Originally posted by wikipedia wikipedia wrote:

white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density


Your mistake was to EQ your system with pink noise as input signal so achieve the appearance of white noise. So essentially you EQ'd it
 to output white noise. Probably by boosting the highs a lot and cutting some bass. Any music you will put into the system after that will sound harsh and without bass.


Pink noise resembles natural sounds and music more closely than white noise, but it has a downward slope, if viewed on an FFT RTA (as you can see in the pictures above), unless the RTA has a slope correction feature. I use a plugin called Voxengo SPAN that has this feature, there is a freeware version available. The slope correction compensates for the constant power loss to produce a flat spectrum line. On old-school "block display" RTA's (octave or third scaling, doesn't matter) pink noise should look flat as well, because a single vertical line represents the energy in a frequency band, as opposed to showing the values for all the single frequencies (which would result in a tilted line again). The frequency bands become bigger with rising frequency (they are relative number ratios, not fixed!!), and this compensates for the inverse power loss.

Personally I think pink noise is more practical for system tuning. While both are not very pleasant, any substantial SPL level with white noise is quite painful without ear protection, and could be even harmful to the HF drivers if used at very high levels and for extended time. Also the mid and especially bass are very low in level compared to the high frequencies. 

Technically you have variations of two options: You could A) either just use white noise B) use pink noise and EQ for a downward sloping line  C) use pink noise with an RTA (plugin) that has a tilt function
D) use an RTA (plugin) that supports multiple simultaneously overlaid spectra (e.g. voxengo SPAN plus) -> overlay test signal with measurement mic input.


Edited by bob4 - 25 September 2017 at 3:08am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 25 September 2017 at 5:08am
Three options - Use a dual channel FFT and MLS/ESS stimulus to compare what goes in to what comes out instead of an RTA.

It's almost as if REW wasn't free, and included a pretty decent manual on how to use it…

Edited by toastyghost - 25 September 2017 at 5:09am
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Foca_Dacian View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Foca_Dacian Quote  Post ReplyReply Direct Link To This Post Posted: 25 September 2017 at 9:08am
I have used the RTA function on the Behringer X-32 for the measurement.
It overlays on the consoles screen the frequency response over a GEQ and is really easy to use.

I have to read and see if it take into acount the sloping of pink noise, but regarding the results I have obtained , it most likely not.

I have used the settings and stept in this instructional video from Music Group:


this is the mic used for measurements:


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Foca_Dacian View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Foca_Dacian Quote  Post ReplyReply Direct Link To This Post Posted: 25 September 2017 at 9:10am
Thank you for the replies, staring to understand.
I have downloaded REW , reading the manual.

What other paper do you recommend reading to better understand measurements and how to interpret them?


Is the ADC in the UR22 from Steinberg good enough for FFT measurements?



Edited by Foca_Dacian - 25 September 2017 at 9:21am
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