Rational Acoustics



Dr. J
August 20th, 2010, 10:45 AM
Hi everyone, this question pertains to system optimization and mixing. I don’t always get to mix BUT I do handle the system optimization every time.

I have noticed on the mixing console that our sound guy boosts the low end on the kick quite a bit. There are other boosts as well like 225Hz for guitar, 3kHz for vocals and some more 5kHz for vocals.

I can kind of see why vocals are boosted up higher in the spectrum BUT I can’t figure out why the kick frequencies are boosted so much when I set the low end response at 12dB strong at 40Hz which then tapers gradually down to 1K & from 1K on out -- flat as I can get it.

SO – my thinking is that EITHER I need to set my low end response stronger that way our sound guy doesn’t boost the kick (63Hz) so much OR find out from the sound guy if he is assuming the kick NEEDS to be there FIRST for some reason and then trying to get everything up enough to match it. Does that make sense?

I know the frequencies are going to be boosted and cut on some BUT I would like to come up with my own personal curve or response I guess – that requires less EQing at the console.

I am trying to figure out if this is a sound guy error or an optimizer’s error or both. I read almost everyday on forums where sound guys argue over what frequencies need to be boosted and cut and I am thinking to myself, “It depends on how the Frequency Response of the system is set up. Mine is strong ( I thought) in the lower half of the spectrum. There should be more leaving it alone & cutting than boosting.

What do you guys think? Am I crazy?

The PA system is mine so I have the luxury of having the same system venue after venue & it is easy to pick out patterns. Just want to be the smartest SMAART guy around in this area……..:D

Christian Tepfer
August 20th, 2010, 01:14 PM
I wouldn't be concerned about a mixer boosting low end on the kick drum.
In fact when I mix I boost low end on the kick drum most of the time and decide where I put the kick drum in the subs that way. So depending on the music style, the kick drum and other sub carrying signals I put the kick drum into different regions. I also put a Lo Cut below my boost. But that's mixing style.

So you could ask the mixing engineer if he would like some more sub level (so you can re-adjust your system due to the risen acoustical crossover). You could even adjust your system to the headliner's mixing engineer's taste if you know how he likes the system. That would mean you can time-align your system with the actual levels the show actually uses.

Dr. J
August 20th, 2010, 01:45 PM
Thanks Christian! I hope my question made sense. So in other words -- I know or at least thought my system was strong in the low end so my thinking was -- why should you have to boost anything BUT I guess you are saying that even though it may be strong already, certain frequencies of the kick may still need to be boosted to bring them out. Is that right?

Ok -- how about this: You are a FOH guy and you also understand that the system has been optimized and you can probably (most likely) visualize the frequency response curve you got going on -- so what instrument do you start with that sets the stage for all other instruments? What I am gettting at here is to avoid a circular reaction. I have a strong low end but the kick is boosted. Now my vocals need boosting to get up and out front..... and so on and now back to boosting the kick some more.....

Really all I am trying to do is look at the mixer after a gig and see where all the MAJOR boosts took place and maybe the next time I run Smaart on my system try to help out in those areas so the sound guy doesn't have to do radical EQing. Our sound guy uses more boosts than cuts.

I guess it is all in the mixing strategy.

Christian Tepfer
August 20th, 2010, 03:58 PM
Tricky question, cutting or boosting?
Just because a mixing engineer boosts a frequency doesn't have to mean he thinks your system is weak in that area and needs more input at that frequency. Well, when he's +15 on the desk and on the graphic it may well mean that.

Let's take the Kick Drum as an example:

Boost 60 Hz or cut 100 Hz? With a boost the gain is maybe lower, so the same energy is put into the subs.

I don't think big boosts are evil by nature, they can be as can be cuts when you have to crank up the gain on the channel.

I tend to start with the Bass Guitar to set a my low and sublow frequency range and place the Kick Drum after that. If I boost sublow on the Kick Drum depends on the fact "is the Kick Drum in the right frequency area or not".

Ferrit37
August 23rd, 2010, 05:20 PM
Hey Guys,
What I do as a systems engineer is look along the chanell eq's (easier to do on analog than digital console) and look for comonality's. then i would ak the engineer would he like to move these into the system EQ to free up the chanell strip for more useful things. As too boosting for the kick drum would you want the lead vocal Eq affected by the kick eq? surely a linear approach that allows the engineer to apply artistic interpretation would be better.
I'm not saying flat here, I still end up with the typical "haystack" bass, reasonable flat to about 3k(ish) then a gradual -3dB slope out, a "house-curve" if you will depending on the music genre.

my 2p

Dr. J
August 23rd, 2010, 06:58 PM
Thanks guys for the input. Ferrit -- when you say "Haystacked" on the low end -- what does your curve look like?

When I first got into using Smaart -- I set my response as flat as I could all the way across the spectrum. At the gig -- I found out real quick how much the system lacked in the low end. A friend of mine who uses Smaart told me that some guys set it to taste. he told me to start off with around a 12dB boost from 35-40Hz and taper it down to 1K and go flat from there. Wow -- what a difference that made. Here I am about a year down the road now & I feel comfortable trying different things and comparing since my system EQ has "Presets". If i don't like one -- I can ditch it and go back.

I saw a video where Dave Rat likes to set his response on a complete gradual taper from 20Hz to 20K. So would you mind telling me what you have had success with? It is strange that a lot of things Dave Rat discusses is the same type of thinking I do and before a couple of weeks ago -- I have never really heard of him.

How strong do you have the low end set (dB wise) and does it taper down to ??? And is any part of the response actually flat?

Any help would be greatly appreciated. Thanks!

Ferrit37
August 24th, 2010, 12:56 AM
Hey Dr J,
I think the first thing is to try and feel out what the engineers preferences are, this is easier if you're doing several shows rather than just one night with him.
Also the typical "haystack-bass" is genre specific, I would expect about a +10dB from say 35Hz out to 125Hz relative to the 1kHz level for a typical "rock" application, for Dr Dre or Snoop this would increase to maybe +20dB but then so would the sub/top ratio from say 2:1 to 1:1 or higher :) for corporate/classic I would be looking at a much more neutral setting (maybe no subs?)
another thing that's going to affect this is aux sub versus standard L/R (there's been plenty of stuff on this posted here)
The area between 125hz(ish) to 3k(ish) is reasonable flat and then I taper off (bit like the x-curve)
These preferences are entirely subjective hence the name "house-curves" I'm sure if you asked around you would get some different answers from different people.
Dave Rat likes to use an analog RTA KTdn6000 if I remember correctly, but it certainly works for him.
I'm sure Harry, James and Jamie will chime in here.
if it sounds good....its right

Dr. J
August 24th, 2010, 10:24 AM
Thanks Ferrit! Yeah I would like for others to chime in as well on this. I don't run Aux Fed Subs and I am not totally opposed to it by any means -- I just don't know how I would use Smaart to do it. It seems to me that smaart would view it as contamination BUT I think I have read somewhere on here where guys have figured out a way to do it. Anyway..... Thanks for your help.

James Woods
August 28th, 2010, 03:57 PM
Exactly. When you run the subs from a separate output from the mains, the corresponding bass on the trace will show up pretty as a big boost (Ferrit´s haystack). This is because Smaart is seeing a much bigger level that what is comming in on the reference channel. If you turn off the subs, those "haystack" frequencies tend to flatten out.

My view is do what needs to be done, and what sounds good and maintains a good amount of headroom, not to mention EVEN coverage. The method needed to get there can differ, according to the show, band, the engineer, the venue, and all those other variables. Seeing +20dB at 50-60Hz is not necesarily a bad thing. It´s what your system is doing with the program you are reproducing.

In the end ask yourself, "Does this sound good?", ¿Can it sound better? What other approach can I make to get the same sound but be more efficient, not waste so much power, or get less room interaction.

In a recent festival (30 days) I experimented a lot (and learned a few things). I got good results with radically different EQ settings, and system settings. In the end, the setting I liked most was the one that did less (less is more). In other words, the line array was pretty much at the same level (it had three divisions), and little EQ. I investigated some lobing between loudspeaker boxes that gave me a dip between 3K and 5K in one seating area. Everywhere else was stellar. Trying to "fix" that area would ruin larger portions of other areas. In the end, I found level change and EQ between the Array sections achieved the most natural sounding result.

Ferrit37
August 29th, 2010, 01:25 AM
Hey Guys,
It's not my haystack I was just looking for nesting materials :)

The mantra "do least harm" springs to mind, one curve doesn't fit all.

Dr. J
September 15th, 2010, 10:37 AM
Hi Guys -- I wanted to ask one more thing before I get busy on my system. I re-did the system with averaging and I felt that it sounded similar to ground plane EXCEPT the fact that it did have more even coverage throughout the listening space.

The high end spectrum like I was describing earlier in this post seemed like everything had to be boosted on the channel strip EQ to bring clarity out of it.

I know many of you (probably all of you) use music material as a check source to see if you are on track. I am a fairly young guy and I have no idea what would be a good music source to use.

What do you guys consider is a good CD to check your system with?

Some say Steely Dan, Toto & Tom Petty........ The older stuff must have been recorded uncompressed and as pure as possible.

Thanks!