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Author Topic: What should a Sound System frequency response look like?  (Read 1973 times)

Frank Koenig

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Re: What should a Sound System frequency response look like?
« Reply #20 on: November 11, 2019, 12:38:46 pm »

The bit I don't get is that everyone seems to think a "flat" system sounds bad. I find they sound great, but of course my reference (home HiFi) is also flat so it's definitely what I'm used to.

I think you are in the bass-averse minority :) Pretty much everyone in my experience, whether involved with pro-audio or not, seems to like a substantial bass boost when playing back commercially mastered music. This is irrespective of the playback level or style of music. When soft they want boost so they can even hear the bass, and when loud they want exaggerated bass to flap their trousers. I usually use a low shelf starting at ~500 Hz and  ~+8 dB at 100 Hz.

The exception is cinema. Movies mastered for home viewing always seem to have plenty of bass (low frequency effects?) and I play them back flat to get better vocal clarity.

My theory is that this goes back to phonograph recordings that had limited dynamic range at low frequencies and has persisted, perhaps because of the limited low frequency capability of small consumer payback systems (it sucks when the plastic box rattles). The folks who want bass, and have a system that can reproduce it, turn it up. I'd love to hear about this from the point of view of any mastering engineers here.

Now when it comes to developing speaker settings, I'm all for flat. White canvas and all that.

--Frank
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Brian Jojade

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Re: What should a Sound System frequency response look like?
« Reply #21 on: November 11, 2019, 01:36:44 pm »

Recorded vs live are very different things.  Personally, I like to tune my overall system fairly flat, then adjust each thing in the mix appropriately.  That being said, I rarely rely on measurement mics for this anymore.  I can simply listen to the system and get it close enough for me to work with it. If it's off by a dB here or there, it doesn't much matter, since I'm compensating for things in the mix anyway.

For music playback, it's kind of interesting that a system tuned flat does seem a bit, well, flat.  You'd think that studios would be tuned flat and want the music to sound good on a flat system.  But they do seem relatively consistent at least.
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Eric Snodgrass

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Re: What should a Sound System frequency response look like?
« Reply #22 on: November 11, 2019, 07:58:25 pm »

For music playback, it's kind of interesting that a system tuned flat does seem a bit, well, flat.  You'd think that studios would be tuned flat and want the music to sound good on a flat system.  But they do seem relatively consistent at least.
It depends on the music and also how and where it was mixed.  There are some well-known studio mixers who mix some projects using headphones and laptops.  I've read articles where they say they've mixed while traveling in airplanes or staying in hotel rooms.  Doing that takes the studio room out of the equation.  So they're mixing to the sound of their headphones and possibly whatever room simulation plugin they've put on the master bus. 

When I'm EQing a system I have never had a goal of creating a "flat" system tuning.  I'm just trying to find and lessen frequencies the p.a. is exciting in that particular space.  If I don't have the luxury of time to use a measurement system (which is 98% of the time), I'm using whichever type of "money" microphone that will be used the most (wireless handheld, lectern mic, lavalier, headset mic, etc.) to hear how the system is reacting to the acoustic space and correct any frequency anomalies I hear.  I aim for vocal clarity.  That method for me leads to good results for everything else played through the p.a., because I've learned that if a vocal mic is exciting frequencies around 150 in a room then everything else that can reproduce that frequency will also excite that frequency.
I've found that most new speaker systems that I've heard, from mid-level MI powered boxes to high-end arena systems, sound pretty darned good right out of the gate (thanks to manufacturer DSP and tunings).  So when I'm mixing FOH I'm finding it extremely rare these days (to the point of being almost non-existent) when I'm tweaking EQ for the mains because of the sound of the speaker itself. 
It's great when I do have the luxury of time to make measurements in a room.  It helps me pinpoint any issues with the reaction of the room.  I never expect a certain shape to the frequency response graph. 

So, the TL;DR - a sound system frequency response chart should look exactly like how the sound from the speaker system is reacting within whatever environment it is placed. 
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Kevin McDonough

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Re: What should a Sound System frequency response look like?
« Reply #23 on: November 12, 2019, 05:54:39 am »

I think we often misunderstand the difference between what is meant by flat vs that of linear.

When you use an RTA, you are measuring the sound in a space and this includes reflections, nodes, comb filtering ( mic placement matters here ) and losses due to distance. So you EQ tills it's flat and it sounds like ass because the bass is low and the highs are exessive. The system is flat though..... The problem is that you don't have a reference. It is just noise in the venue that you assume is correct from the source and the mic picks up what is hears and you see a reading.

Linear is a different animal. Linear can mean two things. It can mean that what goes in, is what comes out ( which is the basic idea ) or it can mean that the system is devoid of large irregularities that are obviously not intended. Let's say that all you have is pink noise and an RTA setup. If you can get the RTA data from the source media you can compare it to the RTA data you get from your room mic. If there is a large hole around 250hz in your room reading, that does not correspond to your source media, there is a reason for that. You have to decide if it is mic placement, room modes, comb filtering or otherwise. But if your RTA reading is relatively smooth and tracks the source media pretty closely, chances are good that if it sounds good in the room, it is fine. Linear system response is ideal and the general basis is that it corresponds closely to what the source media is. The challenge to acquiring a linear system is a way to monitor and compare your source media to your measurement of the PA.

this is the most sensible post in the thread so far.

Firstly, no one wants a "flat" system in terms of the exact same SPL for every frequency 20hz to 20khz. As many people have said it'll sound too bright and lacking bass. But a "flat" system and a flat transfer function are two very different things.

I think also, I rarely have a single system tuning I'll use, it often depends on the genre of music.

In all of the work I do, tuning a sound system usually comes in 3 stages:

1) measure each band of speakers (usually the tops and then the subs, but maybe also mid bass cabs as well if you have specific cabs for that etc) using the transfer function of Smaart, Systune etc. At this stage I'm looking to check that they're broadly flat, and that there are no obvious holes or dips. If there are try and see if it's a room reflection, positioning issue, etc etc and see if it's solvable.

2) Compare the crossover region where these different speaker bands meet, make sure they're delayed and in phase as much as possible.

Once I know that the elements of the sound system are all operating correctly then....

3) Tune to taste.

this is the most important step. The other two are just checking everything is working correctly and you have a blank canvas to start with, this step is now setting the system for the show. And here I'll be using my ears as much as the measurement system.

Firstly I'll play some of my common test tracks. These will check that the system sounds broadly OK and I'll make a few level/EQ adjustments here. Everyone loves to rhyme off their favourite test tracks, but the actual track itself is less important, what's most important is that you know it inside out, back to front, and know exactly how it should sound, that way if it doesn't sound like that you can quickly pick out any issues. Generally I'll probably put a bit of a boost on the subs, maybe pull out a few db around 2k. If it sound boxy I'll pull out a little around 400-800hz, boomy usually around 200hz. In these cases I will sweep the eq back and forth a bit until i find the sweet spot that evens it out. Will also listen to the top end and decide if I need to make any EQ changes there. And of course the room makes a big difference, the same sound system might have quite different EQ depending on the room.

Also, get to know your voice! I know most people hate the sound of their voice, but getting used to it is a big thing for system tuning. A big part of your tuning regime should be to talk through the PA with whatever vocal mic your artist(s) will be using, and make sure it sound natural and even at the tuning stage. Obviously with EDM or something this is less important, but assuming the vocals are a big part of the vocal sound, spending the time at this stage making sure your voices sound clear and natural in the PA will save a pile of hassle when it comes to actually sound checking and doing the show with the act.

But secondly I'll play some tracks that are relevant to the genre of the show, and probably adjust a little more from there. If I'm doing an acoustic/folk music show the subs might only be boosted a touch above the main PA. A rock show usually 6db or so. Big bass heavy hip hop might have the subs 20db up on the mains, and Dance/EDM music the subs at least 20db as well, but also probably a fairly noticeable scoop out the mids.


K

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Bill Meeks

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Re: What should a Sound System frequency response look like?
« Reply #24 on: November 13, 2019, 04:31:24 pm »

Lots of good information from the various responders, but I take issue with the folks who say (paraphrasing) "...forget the meters and use your ears...".

The problem with that mindset, in my opinion, is those are YOUR ears. They are NOT the ears of your audience. What if you have been in this business for years and are old (I'm old, too, so take no offense please) and have listened at loud volumes for too long and your hearing is like -20 dB down at 10K compared to a young adult? Or what if you have hearing issues in other ranges and don't realize it? What sounds "great" to you might sound borderline awful to others.

Meters and analyzers are more objective. Yes, I understand all the details about room nodes, comb filtering, phasing and all that, but you can compensate for those limitations by taking several measurements around the venue and averaging. Certainly not perfect, but it helps.

Using just YOUR ears is akin in my opinion to letting a color blind person design a light show or choose paint colors for a room. The end result is not likely to match up with what the majority of non-color blind folks might choose.
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Caleb Dueck

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Re: What should a Sound System frequency response look like?
« Reply #25 on: November 13, 2019, 07:36:18 pm »

Lots of good information from the various responders, but I take issue with the folks who say (paraphrasing) "...forget the meters and use your ears...".

The problem with that mindset, in my opinion, is those are YOUR ears. They are NOT the ears of your audience. What if you have been in this business for years and are old (I'm old, too, so take no offense please) and have listened at loud volumes for too long and your hearing is like -20 dB down at 10K compared to a young adult? Or what if you have hearing issues in other ranges and don't realize it? What sounds "great" to you might sound borderline awful to others.

Meters and analyzers are more objective. Yes, I understand all the details about room nodes, comb filtering, phasing and all that, but you can compensate for those limitations by taking several measurements around the venue and averaging. Certainly not perfect, but it helps.

Using just YOUR ears is akin in my opinion to letting a color blind person design a light show or choose paint colors for a room. The end result is not likely to match up with what the majority of non-color blind folks might choose.

Agreed. 
Along with this, knowing how to use Smaart/Systune allows you to tell why you like or dislike a particular voicing.
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brian maddox

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Re: What should a Sound System frequency response look like?
« Reply #26 on: November 13, 2019, 11:01:03 pm »

So here's the thing...

Sound Sources [musical instruments, etc] vary WILDLY in their sonic signature depending on their construction, their design, how they are played, how loudly they are played, the direction they are facing when played, etc.  To capture this widely variable source we use...

Microphones, which vary WILDLY in their sonic signature depending on their construction, their design, what direction they are facing, how loud the source they are capturing is, and the electrical characteristics of the system they are plugged into. 

We then run that signal through a system of filters, attenuators, gain stages, various pieces of copper, aluminum, silicon, etc. all of which have an effect on the sound that is then produced by our ...

Loud Speakers, which vary WILDLY in their sonic signature depending on their construction, their design, what direction they are facing, and how loudly they are reproducing the signals given them.  Which then excites...

A room full of Air that will vary WILDLY in it's sonic signature depending in it's temperature and humidity, the room's size and construction, it's design, the relationship of the room to the sound sources [which may be a mixture of reinforced and un-reinforced]. 

This Milieu is then captured by...

Ears, which vary WILDLY in their frequency response depending on Age, Size, Shape and that signal is then shipped off to

Brains, that vary WILDLY in how they perceive all of this information depending on biases, relationship to visual information, and a dizzying array of experiences that are literally different for every single human...

Yes, i'm stating the obvious [and ironically over simplifying].  But it bears remembering.  What we are attempting to do is 90 percent science, 90 percent art and another 70 percent Black Magic.  There is no definitive answer to the question "What should a Sound System frequency response look like?"  That doesn't make it a bad question.  In fact, it's a GREAT question.  But the closest we're gonna get ultimately to an answer is...

it depends
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Uwe Riemer2

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Re: What should a Sound System frequency response look like?
« Reply #27 on: November 14, 2019, 04:46:37 am »

The array processing target from d&b is a good start.
Applied with reason and said technique from said manufacturer will give you this in more than one place.
« Last Edit: November 14, 2019, 04:53:57 am by Uwe Riemer2 »
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Randy Pence

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Re: What should a Sound System frequency response look like?
« Reply #28 on: November 14, 2019, 06:57:40 am »

Using just YOUR ears is akin in my opinion to letting a color blind person design a light show or choose paint colors for a room. The end result is not likely to match up with what the majority of non-color blind folks might choose.

I once worked at a club whose owner was colorblind. I only found out as I was doing some troubleshooting on the phone for him and he of course could not see any red lights in the rack, lol

He also did the interior design and architectural lighting. It was actually quite tasteful. Lots of brown woods, orange, and reds. Very little blue. I have no idea what he actually saw.
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Peter Morris

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Re: What should a Sound System frequency response look like?
« Reply #29 on: November 14, 2019, 07:47:30 am »

The array processing target from d&b is a good start.
Applied with reason and said technique from said manufacturer will give you this in more than one place.

These ....
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Re: What should a Sound System frequency response look like?
« Reply #29 on: November 14, 2019, 07:47:30 am »


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