In-Room Freq adjustment questions

[Phil_RC_1]

Hi Guys,

Do I rely on RTA measurements to setup the FR of the Systems in-room response? One of the problems being that I can't do the measurements when the room is full of people.

How bout EQ'ing stage monitors?

Phil

[Randy L]

The RTA (with a good EQ) is the typical way to "flatten" a room, but many rely on their ears. Yes, the acoustics really do change when it is filled with people. But if the speakers are properly placed to account for them the sound quality can still be maintained.

[meep]

absolutely eq the monitors. don't eq them for hi-fi awesomeness. eq them for function. get rid of any freq that feeds back. eq them with the mains off. roll of the top and bottom as much as you can stand it because they WILL bleed into the house. If your board supports it, run multiple sends so that you don't have everyone in every monitor. Even 2 mon mixes can be helpful (tho more complicated).

The big thing with RTA-ing a room is to eliminate the resonant peaks. If you don't have an RTA you can get it close with free laptop s/w, iphone apps, or the old-fashioned way. Get a CD with test tones, play it. Use a $50 SPL meter and record the dB of each frequency. the higher dB's? cut-'em on the mains eq. If you've never done it, I highly recommend trying it. You'll get a better feel for what you are doing. TAKE YOUR TIME. Get your chicken fingers, a bag of twizzlers and a diet coke and camp out there for a while. do several passes. Invite a friend or two to participate. And if you have the ear for it, one day you might be able to hear the pitch and know the freq to cut without a tool.

I like your questions. You as the right ones. :-)

M

[Paul O]

Actually... using an RTA and auto EQ to flatten speakers in a room is probably going to cause as much trouble as anything, the corrections are only valid for that mic position and if that happens to be in a null the process may make the speakers even more feedback prone than usual.

The right way to use these tools is with the speakers in an anechoic environment(outdoors away from buildings), that way you can correct the speakers response without room reflections and boundary cancellations getting in the way. The resulting baseline should then only need minor tweaking by ear to account for venue influences like boominess or bright or dull high end.

[Phil_RC_1]

absolutely eq the monitors. don't eq them for hi-fi awesomeness. eq them for function. get rid of any freq that feeds back. eq them with the mains off. roll of the top and bottom as much as you can stand it

That's what I've been thinking, but some of our band members want "HiFi" in their monitors, I guess they'll just have to live with it:)


because they WILL bleed into the house. If your board supports it, run multiple sends so that you don't have everyone in every monitor. Even 2 mon mixes can be helpful (tho more complicated).

I have also read the theory that since we know that the monitors WILL bleed into room, that you want a full mix in each monitor, so that the sound that bleeds out is a full mixed/not an incomplete unbalanced custom mix. As it is now, I have 4 custom monitor mixes.



The big thing with RTA-ing a room is to eliminate the resonant peaks. If you don't have an RTA you can get it close with free laptop s/w, iphone apps, or the old-fashioned way. Get a CD with test tones, play it. Use a $50 SPL meter and record the dB of each frequency. the higher dB's? cut-'em on the mains eq. If you've never done it, I highly recommend trying it. You'll get a better feel for what you are doing. TAKE YOUR TIME. Get your chicken fingers, a bag of twizzlers and a diet coke and camp out there for a while. do several passes. Invite a friend or two to participate. And if you have the ear for it, one day you might be able to hear the pitch and know the freq to cut without a tool.

I like your questions. You as the right ones. :-)

M

I have a Behringer RTA, I also have SoundEasy on my laptop that I can do gated measurements with, it's just finding the time and formulating an organized game plan before I get it done.

And thanx for the compliment. Actually, I'm not new to audio in general so I have an idea of what has to happen and what Q's to ask. But live mixing and the Pro-audio world is simply a different Monster and has it's own nuances and "in's & out's" then speaker design, home and car audio which I am more familiar with.

Phil

[Phil_RC_1]

Actually... using an RTA and auto EQ to flatten speakers in a room is probably going to cause as much trouble as anything, the corrections are only valid for that mic position and if that happens to be in a null the process may make the speakers even more feedback prone than usual. The right way to use these tools is with the speakers in an anechoic environment(outdoors away from buildings), that way you can correct the speakers response without room reflections and boundary cancellations getting in the way.

So then, it would make sense to do gated measurements (simulated anechoic) on the Main speakers using something like SoundEasy to get the mains base-lined flat (or near flat).


The resulting baseline should then only need minor tweaking by ear to account for venue influences like boominess or bright or dull high end.

Understood. I think even with using the RTA, the idea is to only make minor adjustments by ear, using the RTA, while roming the room, as kind-of a compass to find possible extreme problem areas. I would definitely not make a tweak that sounded horrible just because the RTA said it was right. I AM quickly learning to trust my ears regardless of what any "Test Equipment" says.

Thanx for the reply and help.

[meep]

Paul-- I'm confused by your comment to only RTA the speakers in an anechoic environment, that RTA-ing a room is generally problematic.... what??? I agree with the point about null zones--- yea boosting a dead freq is usually a power-killer and generally useless--- but tuning a room is *very* important and to a degree actually allows for greater mic-handling errors.

Methinks maybe you are looking at this from a speaker-design perspective and not a production perspective?

Room dimensions, treatment and features don't change. It's resonant freqs *generally* are consistent allowing for some variations. Temps, people, temp difference between floor to ceiling (in a tall room such as auditorium balcony) play variations. But... there's a reason digital EQ's and boards allow multiple user settings-- as a shortcut/baseline for different repeated production venues.

Furthermore when RTAing a public venue, one doesn't use the vocalist mics anyway-- as they are generally very colored. SM57 is warm and sharp, SM58 smoother, a condenser is brittle, OM1 dull, SM58B bright... it's tuned from the listener's point for the listener, not so much for feedback. Get the room flat.... FB varies per mic so use the channel strip unless it's a common band across multiple sources. two different purposes...

otoh I too learn things every day... so... am I missing something / misread your post?

Mike

[meep]

EQ-ing monitors.

The choice to go hi-fi vs selected bands is going to be your call. Alot will depend on the room, reflections off the back wall, and bleed over. Another approach since you have a good number of channels is to use less eq and more of a talent mix. So-- EQ to kill feedback and protect the monitors from excessive bass. Then only give them what they need. Lead vocalist needs lots of self, some guitars and a reduced but even BG vox. BG vox need the BG mix with some lead (or maybe not). Rhythm section needs self + some lead vox. The lead electric player needs 8x lead electric and nobody else (kidding).

OR if that's too complex you can mix by location:
Give all monitors an even mix and just highlight the folks near them. Then, subtract instruments that are already naturally heard from that mix. i.e., highlight nearby vocals, subtract the guitar cabinet, etc..

THIS one really all depends on the space and the talent in play.... in my experience. Good luck--- I find that everyone is a critic in monitor world.

M

[Paul O]

Paul-- I'm confused by your comment to only RTA the speakers in an anechoic environment, that RTA-ing a room is generally problematic.... what??? I agree with the point about null zones--- yea boosting a dead freq is usually a power-killer and generally useless--- but tuning a room is *very* important and to a degree actually allows for greater mic-handling errors.

Methinks maybe you are looking at this from a speaker-design perspective and not a production perspective? No not at all, it's based on my production experience and what I have learned from those that know more than me. RTA can be usefull to visually display how a venue is affecting the sound being produced but it really doesn't tell you much about the speakers. In room RTA is also completely mic position specific and since you can't correct for every possible mic position at the same time it's not really of much use. A speaker system that has as flat an anechoic response as possible will deliver superior results in all venues with little additional adjustment, room nodes and reflections should be addressed with speaker placement and room treatments as EQ will have little effect on these things.

Bottom line is using AutoEQ in a venue does not correct speaker deficiencies, it simply attemps to make all frequencies equal loudness at the test mic position and that isn't really desirable or usefull. Nobody wants to listen to an audio system that is accoustically perfectly flat, they want some boom and sizzle but if you try to achieve that with speakers that aren't flat to begin with you will have problems in many cases.



But... there's a reason digital EQ's and boards allow multiple user settings-- as a shortcut/baseline for different repeated production venues. Yes exactly, but the preset you save should be a product of the speakers anechoic correction plus the venue specific tweaks.


P.S. These comments are meant to address FOH speakers only, monitors will need a totally different final approach based on the individual requirements of the artist it is supporting, but again it's always better to start with a speakers system that has a flat response because it will allow more gain before feedback.

[meep]

Ahhh.... Ok I'm going to chalk this one up to interpretation.

Agreed-- an RTA is not the best choice for correcting "flattening" *speakers*. That's my bad. Agreed-- frankly best use of any eq is to minimize due to phasing and other problems.

I was looking at this as a *room tuning* discussion, where an RTA or other method of tuning the room *is* valuable and very useful. I can't imagine any successful tech bashing room tuning (tho I can see them bashing the RTA as some folks tend to "live by" them more than others-- we all have our favorite techniques).

And, in agreement, correcting sloppy speakers during room tuning is also far less pleasing than tuning a room with good speakers. However, I'm not sure I've ever truly had the pleasure of working with perfect speakers in any room-- gotta work with what I've got... and even then things like off-axis response make a "perfect" speaker become lame... so here again... gotta work with what ya got...

Regarding RTA mic placement-- I disagree with mic placement making RTA tool of little value. Tuning a room is an art as much as it is a science. You have to shoot it from multiple positions and work out the best settings that help the overall sound. Yes, it varies from mic placements, but *some* characteristics, generally the low-mids to lows, tend to be consistent. Think 250hz and down. Sometimes odd things show up 500-650 in my experience, and of course if you are dealing with large rooms with multiple clusters and adjustable XOs then it gets even more complex... I have spent hours in fixed installations and still not gotten it right... and No, the RTA is never the final word, but it is a good tool.

I do not have perfect pitch, but I am able to hear tone and identify the frequency (within reason). That said, as much as I like to go "old school" and tune it by ear, I find the RTA is useful and can provide a few quick shortcuts that I might or might not catch in my own subjectivity.

My $.02

Mike

[nj_ray]

[QUOTE=Phil_RC_1;1627623]That's what I've been thinking, but some of our band members want "HiFi" in their monitors, I guess they'll just have to live with it:)

Or suggest they drop some cash on in ear monitors and you will EQ them however they want:)

[Paul O]

in agreement, correcting sloppy speakers during room tuning is also far less pleasing than tuning a room with good speakers. However, I'm not sure I've ever truly had the pleasure of working with perfect speakers in any room-- gotta work with what I've got... and even then things like off-axis response make a "perfect" speaker become lame... so here again... gotta work with what ya got... I should point out that my comments are aimed more at products like the DRPA and DCX and how the RTA and AutoEq functions are better utilized to fix the speakers than to attempt to fix a room. No speaker is perfect obviously but a processor like this can do a lot to improve them particularly when it is also replacing the passive crossover. With your typical 2 or 3 way PA speaker system you can achieve true time alignment between drivers and when coupled with the crossover function this improves both transient and off axis response. Then apply some parametric EQ to tame the big response peaks or dips and you end up with a much better performing speaker system.




No, the RTA is never the final word, but it is a good tool. Agreed on that, when used the right way it can be helpfull to understand what is going on.

[meep]

Paul--

Ok, I thought that is where we were approaching it differently. Whew!

I agree-- I don't like the "autoEQ" systems. I'll shoot noise but prefer to make the adjustments by hand.

All is right in the small world now.

Mike