HeySoundGuy
Assisstant
Joined: 03 Jan 2004
Posts: 32
|
| Tuning a PA? |
 |
|
OK in another post you talk about EQing and Tuning??
What is the difference...I am fairly new to all this and I have never heard the expression "Tuning" a PA
Little Help?? |
Thu Mar 25, 2004 12:02 pm |
|
|
wailingalleycat
Forum Manager
Joined: 07 Oct 2003
Posts: 694
Location: Jersey C.I (UK) |
Do you understand about frequency response?
That is a frequency response graph, notice how it fluctuates in certain areas.
Only the most expensive speakers have a perfect frequency response. When tuning a pa you use a graphic equalizer to make the frequency response flat across the range, However different rooms and places affect the frequency response of a PA so you need to adjust it every time you move the speakers.
This is usually done with an real time analyzer which plays pink noise then either tells you what to adjust or automatically adjusts itself.
EQing is when you use an equalizer to make things sound better or to eliminate feedback which i went into in the post before this one.
HTH
-Paul
_________________
If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer.
Last edited by wailingalleycat on Wed Apr 07, 2004 12:59 am; edited 1 time in total |
|
Fri Mar 26, 2004 1:36 am |
|
|
|
|
HeySoundGuy
Assisstant
Joined: 03 Jan 2004
Posts: 32
|
I understand....thank you that was easy.... |
|
Fri Mar 26, 2004 2:04 am |
|
|
john_BB
Tape Op
Joined: 16 Oct 2003
Posts: 23
|
| Tuning a PA? |
|
|
quote:
Originally posted by wailingalleycat
Do you understand about frequency response?
However different rooms and places affect the frequency response of a PA so you need to adjust it every time you move the speakers.
This is usually done with an real time analyzer which plays white noise then either tells you what to adjust or automatically adjusts itself.
Paul
Do you mean Pink noise?
Also I would dispute that a room changes the frequency response of a PA system. (In a real world situation. Yes if you put it in vacumn bell jar in a lab it might behave differently!)
If you are playing a CD through the PA then the only thing you are eq-ing is the sound from the CD and the Room is not affecting the movement of the speakers. What you are referring to is an acoustical phenomenon and EQ cannot remove that.
Sure if the room sounds really "toppy" then if you remove some HF then it's less "toppy" but you have done nothing to change the ratio between direct and reflected sound (which is the reason that PA's "sound different" in different rooms) which is an acoustic problem that can only be changed by different placement of the speakers, putting up absorbative material such as drapes or by removing the buildings walls.
Your RTA at mix position will be displaying the effects of the PA in the environment its in. If you moved the mic to within 1M of the left stack and made an alley of drapes to reduce reflections you would get a better idea of the response of the system.
Also a dip in the frequency response which is possibly a phase cancellation cannot be corrected by the EQ and such a correction is made using delay units (if the problem is driver misalignment) or if it is a polaity problem by temporarily inverting the polarity on the X-over (or permanatly by rewireing the PA) |
|
Mon Apr 05, 2004 8:35 pm |
|
|
|
|
wailingalleycat
Forum Manager
Joined: 07 Oct 2003
Posts: 694
Location: Jersey C.I (UK) |
Yeah sorry i do mean pink noise. ill change it now
The surfaces in a room can cause reverberations etc. and different rooms have different levels of absorbency and so on. When tuning a PA if the acoustics of the room enhance the 1K band for example you can reduce that frequency on your PA this will reduce any peaks and dips and your system will have a flat frequency response. For example a small stage tends to increase bass a huge amount so if you reduce the bass on your eq it will sound alot better.
-Paul
_________________
If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer. |
|
Wed Apr 07, 2004 12:58 am |
|
|
wailingalleycat
Forum Manager
Joined: 07 Oct 2003
Posts: 694
Location: Jersey C.I (UK) |
Just in case you dont know, pink noise is a a frequency rich sound (noise) that closely represents the way the human ear hears sound.
_________________
If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer. |
|
Wed Apr 07, 2004 1:00 am |
|
|
|
|
john_BB
Tape Op
Joined: 16 Oct 2003
Posts: 23
|
|
|
|
quote:
Originally posted by wailingalleycat
When tuning a PA if the acoustics of the room enhance the 1K band for example you can reduce that frequency on your PA this will reduce any peaks and dips and your system will have a flat frequency response.
But that is not true. The frequency response of the PA is not determined by the rooms acoustics. You are trying to EQ the room using the graphic or parametric which is impossible. The room does not change the movement of the drivers!
As I said before notching the graphic does not change the acoustics of the room and you don't change the ratio between direct sound (from the Speakers) and reverbarated sound by using a graphic/channel Eq or feedback destroyer!
What you would be doing by hacking out frequencies is probably "unequalising" your system (presuming your PA is set-up correctly and has a moderatly flat frequency response to start with) in order to try and get an acceptable level of performance. (in the sense that by stopping a PA producing 125-400hz so that the audience doesn't hear unpleasant sounds as a result of a rooms acoustics.)
Having worked with the same system commercially in many venues it is a fallacy to say that a graphic will correct the performance of a system in different rooms.
Incidentally most PA's don't have a flat frequency response deliberatly because modern engineers like large quantities of sub bass in order for the audience to feel the music as well as hear it. |
|
Wed Apr 07, 2004 9:03 pm |
|
|
mommi
Joined: 21 Apr 2003
Posts: 47
Location: Tallinn, Estonia |
|
|
|
quote:
Originally posted by john_BB
The frequency response of the PA is not determined by the rooms acoustics. You are trying to EQ the room using the graphic or parametric which is impossible. The room does not change the movement of the drivers!
I guess what wailingalleycat had in mind was the overall frequency response of the
whole
system, not just the PA. The whole system I mean consisting of the PA
and
the room. Say the room favors some frequency over the others by 5 dB. You adjust the graphic equalizer so that the output of your PA is 5 dB less at that frequency, compared to others. In total, then, you get -5 dB +5 dB = 0 dB, instead of simply accepting the +5 dB offered by the room alone.
Am I wrong there?
quote:
Incidentally most PA's don't have a flat frequency response deliberatly because modern engineers like large quantities of sub bass in order for the audience to feel the music as well as hear it.
This surely is a matter of (artistic or whatsoever) intentions and cannot be generalised too much. Enhanced sub bass might be well justified in some occasions (eg dance music) and totally unacceptable in others. Classical music and jazz, for example, convey very much information in upper regions instead of relying mostly on strong low beats. There simply is no place for favoring bass instruments over the others there.
I would say starting with a flat response is a necessity, how you further
shape
your sound is your option. Yes, the PAs do not work in a vacuum, but rather in real rooms with real resonances and frequency responses. Exactly because of that is the graphic equalizer necessary. If you are after a flat response of your PA purely, your choice would be a devoted equalizer that you adjust once in an open air and then leave it so forever. To get the best of different rooms, however, you should add another equalizer for adjusting every time you move to another place. |
|
Tue Apr 13, 2004 12:25 am |
|
|
|
|
john_BB
Tape Op
Joined: 16 Oct 2003
Posts: 23
|
| Tuning a PA? |
|
|
quote:
Originally posted by mommi
I would say starting with a flat response is a necessity, how you further
shape
your sound is your option. Yes, the PAs do not work in a vacuum, but rather in real rooms with real resonances and frequency responses. Exactly because of that is the graphic equalizer necessary. If you are after a flat response of your PA purely, your choice would be a devoted equalizer that you adjust once in an open air and then leave it so forever. To get the best of different rooms, however, you should add another equalizer for adjusting every time you move to another place.
That is why manufacturers offer settings for your DSP crossover, or alternatively sell a system controller for the PA in question. If you unlock a XTA DP226 running an L'Acoustics rig and see all the processing that is going on you will be quite frankly astounded. Furthermore the Nexo Alpha http://www.nexo.fr/set_4.html controller which utilises a sense return uses variable parametric EQ and protects the speaker against thermal and excersion damage. |
|
Fri May 14, 2004 4:31 am |
|
|
 
|
|
Goto page 1, 2 Next
All times are GMT. The time now is Fri May 16, 2008 10:30 am
|
|
|
|
| |
