Rational Acoustics



Dr. J
January 25th, 2014, 01:43 AM
Ok.... Can someone set me straight here.... I understand why the recording industry finds a common ground on how things should be mixed... It seems that they do it this way because it sounds better on the majority of listening devices... Hi-Fi, Low-Fi, iPod ear buds, radio shack headphones, laptop speakers, cheap car stereos...etc.

From a live sound system perspective... You do your best to give the band engineer's a consistent common neutral platform for them to do whatever they want with. I understand that.

What if the recording engineer, the guy mastering or even the system tech, band engineer says ... I want this one to be for myself... I have had it trying to please everyone else... Lol. What would that Phase or Magnitude response look like? Just curious.

Can you have a flat linear phase response but not a magnitude response? I know the other way is easy to achieve...

I own my system. It goes everywhere with me. I use the same gear, same mics, same cables day in and day out.... I would like it to be more linear in phase but not magnitude necessarily..

Any thoughts? Just thought the forum needed a little spice during this dreaded winter..

I appreciate all of you guys. Most of you on here I consider my mentors. Thanks!

Arnau Pro Audio
February 12th, 2014, 09:42 PM
I was wondering about the same question few months ago,
And after talking with many engineers about it there are many diferent opinions.
Usually many people tends to have a flat magnitude response but i think they're not pointing in the right way.
First of all, we need to put things in contest. As we all know not's the same tweaking a PA for a Rock Concert than making it linear for a Theater Acoustics.
As i mainly work in a Night Club and Concert Gigs, i tend to have clearly more SPL in the lowend response.
Which are the levels? +9? +6? There's no answer for this.
But as you've said, just phase it up, correct the room modes for the stationary waves, and then make the gain structure between x-over bands as you consider appropiate. And remember: Trust your ears!

Ferrit37
February 13th, 2014, 11:59 AM
Hey Guys,
I don't want "flat" what I want is Linear, I want to get out of the system whatever I put in, with no hype.
I want my "artistic" judgments on the sound to be transmitted through the system and Not have to compromise to make up for system deficiencies.

I think we can (should) all agree that "FLAT", 20Hz-20KHz +/- XdB, is wrong and that various contours to suit the artistic goals are necessary, otherwise everyone should perform with measurement mics.
It's like Telling Leonardo "you're only using green today mate!"
If everything sounded the same, wouldn't it be boring? It's about ART, with a hefty dollop of Science helping it out.

my 2c

merlijnv
February 14th, 2014, 05:08 AM
Hey Guys,
I don't want "flat" what I want is Linear, I want to get out of the system whatever I put in, with no hype.
I want my "artistic" judgments on the sound to be transmitted through the system and Not have to compromise to make up for system deficiencies.

I think we can (should) all agree that "FLAT", 20Hz-20KHz +/- XdB, is wrong and that various contours to suit the artistic goals are necessary, otherwise everyone should perform with measurement mics.
It's like Telling Leonardo "you're only using green today mate!"
If everything sounded the same, wouldn't it be boring? It's about ART, with a hefty dollop of Science helping it out.

my 2c

+1

Does your second paragraph concern microphones and other components upstream or does it refer to the system mentioned in the first paragraph?

Iím a bit confused. If you want a system to reproduce what you put into it, only louder, then i.e. 1 Volt should create equal SPL at 100 Hz, 1kHz and 10 kHz. A contour applied to the system would alter this relationship. Even if itís an attempt to compensate for the way our hearing mechanism behaves.

There are a lot of justifiable reasons for various contours. Our loudness perception changes over frequency and level, social-cultural differences, program material, etc.. Clearly thereís no common denominator. In the absence of one, I prefer an equal amplitude system. A system that produces equal SPL for the same amount of input voltage over frequency.

That being said, from an artistic POV, I do share the need for low frequency emphasis. However thereís various points along the chain where this can be achieved. Going from downstream to upstream, it could be done in the speakers, at the processor output or input or at the mixing desk output. These are all global solutions. Local solutions would be channel strips and ideally at the source. The latter involves microphone selection and positioning.

Global solutions ease the mixing engineer, local solutions make for better desk recordings.

If Iíd be a lighting engineer, itís like choosing between tungsten lamp (global) with a nice warm light or a neutral white lamp. The latter would allow me to use filters (local), when and where I choose, to achieve the same result. It would also allow me to have expectations on the combined result. A red filter in combination with the tungsten lamp will most likely produce a result more orange than I intendedÖ

Ferrit37
February 14th, 2014, 12:37 PM
Hey Merlijnv
I think I would like from the console on out to the listeners to be as linear as possible, it certainly might have some "flavor" added to it but that would be a "global" contour, warmth etc.
It would also contain any/all room corrections.

I want to reserve mic choice/position and board eq for artistic purposes. With this type of setup what appears at the output of the console is a fair representation of my mix.
I certainly wouldn't contour the system EQ to make the Kick sound good then expect the Vocal to have to pass through that :( (I've heard it done this way)

When it comes to LF I prefer the lower octaves to be a part of the system not overpower it, but I understand that adding a "haystack" to the LF adds excitement/power but +25dB yikes!

I think were saying the same thing, just different words.

Dr. J
February 15th, 2014, 12:48 AM
Is it possible to have a flat phase response and NOT a flat Magnitude response? I know the other way around is possible. Recording guys shoot for a response that sounds better on most devices..... What is that response? Completely flat phase as possible? Is there any curve in there?

So that means they cater to millions of people with many different types of speakers....

Live sound guys cater to people with one set of speakers..... The exact opposite of the recording guys... Just trying to wrap my head around the reasoning.

I think most people agree that a system that is in phase sounds better which I guess is literally matching the input and output. I am curious if the magnitude trace can deviate from flat and the phase stay put..??

Dan Currie
February 16th, 2014, 10:44 AM
Dr. J,
Here's a relatively flat phase response. Bottom wrap is because of the low to sub filters. Another mic placement probably would have added in some top end and flattened out the phase some more.

On a side note I've always liked the Barefoot Micromains for studio monitors. I took some measurements and they are essentially flat. Strange how I don't prefer a flat PA for live sound. I've always blamed this on Fletcher and Monson curves.(insert smiley)

773

Dr. J
February 16th, 2014, 11:38 AM
Thanks Dan!

Dan Currie
February 17th, 2014, 04:08 AM
Recording guys shoot for a response that sounds better on most devices..... What is that response? Completely flat phase as possible? Is there any curve in there?

So that means they cater to millions of people with many different types of speakers....

Live sound guys cater to people with one set of speakers..... The exact opposite of the recording guys... Just trying to wrap my head around the reasoning.


Since phase shift comes from multiple drivers interacting (and their crossover filter selection), recording guys really don't worry about the phase response of their boxes. Mix on ns10's, KRK's, Mackies etc...I'd put $$ on few studio guys have really examined the physics of what they're hearing in a box. Sure they may treat the control room but as far as monitors they're pretty black and white. They like a monitor or they don't. They may mix for different speaker systems but us live guys mix for one system in a room that would ideally sound the same in every location in the venue. The bummer is that once a left/right scenario is setup that goal is impossible.

Chris Tsanjoures
February 17th, 2014, 11:48 AM
It is my belief that well designed system will come from the manufacturer with an ideal phase response. Speaking for myself, and many others I'm sure, we are concerned with the transition between flown and ground stacked elements (front fills and mains) or the Sub to Low Mid crossover, since that is what we have control of (in terms of timing). So this being said, the idea of flat phase is relative when talking about different studio monitors and various live sound reinforcement systems. For all I know, JBL studio monitors may have the same phase response as their VerTec Systems. Do I want to alter the driver to driver relationship in a complex line array? No. Especially not on a show day. I want to know that the system works as expected and then adjust the frequency response for the venue/my taste.

I think this debate is really about magnitude (frequency response). Also, I don't think it is much of a debate. Studio mixing is more clinical, whereas a show is more...well show-y. There is a spectacle element, that when you go to a rock show you expect to feel the kick drum as well as hear it. Dan mentioned the Fletcher-Munson curves, that frequency response and level are directly correlated. If you were mixing a record at 103 dB A, you will find that when you turn the control room down (phew), you will not have something that translates at lower, more practical listening volumes.

What is "Flat" varies from live engineer to live engineer as well. Flat to one guy may mean +6 below 100Hz, flat from 100-2kHz and a -3db roll off up to 10 KHz, or so. For high-powered Rock n' roll, generally you don't need a whole heck of a lot of anything past 10-11KHz. One of my favorite mix engineers rolls the entire PA off at 8kHz, and he's produced some of the best sounding shows I've ever heard.

Furthermore, in live sound what is 'flat' is an aesthetic decision based on what the program material is. A classical performance will warrant a much different frequency response than a EDM show. Speaking as a System tech, we are setting the table for a mix engineer to make their life as easy as possible. On one-off shows, I will consult the headlining engineer as to what they like a PA to sound like, and go from there.

***Shameless Plug*** There are essentially three things to consider here, Studio vs. Venue, Playback vs. Reinforcement, and Tonality vs. Intelligibility. I would go into more detail, but I will save that for the classes. ;)

Dr. J
February 17th, 2014, 11:44 PM
Thanks Chris! I really like what you are saying. I have talked to you over at the Presonus forum where my screen name is JerryD. It used to be Dr. J over there until they revamped their forum awhile back and I lost the name. I have been the biggest advocate for Smaart over there and it is mind blowing what you guys are doing with the VSL integration.

It is funny that you said your favorite FOH guy rolls everything off past 8kHz. Just two weeks ago I ran for a band in a much smaller club than usual. These guys are loud! The drummer thought he was at some outdoor stadium so he plays very aggressively. He is also wearing a headset mic that probably didn't cost much... So you can already see that I may not be able to be very creative with my mix and instead switch to combat audio.

After about a minute or two into the set with all the glistening high end going - I made a bold move and starting cutting every high end slider on the graphic and when I got to the 8 kHz it was incredibly quieter and cleaner sounding on top. It was a moment that made me question why I have the top end of the spectrum so nice and straight.... I actually have a high shelf with a slope of 12 I think and about a -3db cut. I then worked on the individual guitar the same way but on the channel strip....same thing here - guitar sounded much smoother.

My current magnitude response is anything but flat. It is certainly smooth but has some curves in there. I started out flat but also recorded my main out mixes. This told me whether or not my system was on track. Initially my main mix recordings were dull - I then knew I needed to dull down the System EQ which in turn allowed me to EQ a bit brighter on the console and when I recorded the next time - my mix seemed closer to being accurate. This took me several gigs to get it right but my main mix sound matches my system a lot closer now. My final magnitude trace is anything but straight. It is curvy like a roller coaster all the way down.... I am ok with that.

Well - I guess there is no need to probe further with why recording engineers and system techs shoot for a particular baseline..... You got to get it to sound good in every seat in the house and not just the mix position.

Chris Tsanjoures
February 19th, 2014, 12:17 PM
Cool J! Nice to make the connection. I'm glad you are on-board with what we've been doing with PreSonus. I love seeing people like yourself spreading the good word in that market. Feel free to contact me directly whenever you'd like :)

Ben Clarke
March 17th, 2014, 06:56 PM
I will consult the headlining engineer as to what they like a PA to sound like, and go from there.

You mean we have to work as a team????? oh man...