More digital questions (spawned from the other thread) - "summing"?

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wes480

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in the other digital thread, sjoko2 said

"lets put it in the easiest way: "therein lies the summing problem" This is not just a problem with Pro Tools, most DAW software has a same or similar problem. When tracking with a DAW, always consider it as NOT having a level control option at all, and you'll be fine.

I first discovered this problem years ago when I was wondering why one session I had recorded using a Neve Legend console as a front end, going through good A/D converters straight into Pro Tools, sounded great (and I mean.... GREAT), and a subsequent session I did using the same gear, same artist, sounded considerably less.
The only difference was that in the first session I had not touched the faders.
A subsequent test proved this to be the definite problem / answer.
Please note that, yes, the summing problem does exist. Don't overestimate it though. If, as I had said to many times, you use accurate clock and good converters, you have won the biggest part of the battle. "

I am wonder about how my situation applies to this. I have an AardvarkQ10, where the preamps are all built into the breakout box, and the "mixer" is totally software, controlled by Aardvarks Drivers. Can anyone guide me on if I am somehow getting a much worse sound than i could be? And any more information on "summing" in general...I am confused.
 
IMHO...:)
This issue is quite high up the food chain if you get my meaning.
When tracks in a mixer or daw are combined for a mix, they are summed, added. Some are missing the tone they get when they don't send their tracks from the daw back out analog to a mixer, or don't like what they are getting from the daw mix.
There's a good chance this wouldn't make or break a song.
A good reality check for us sound tech types is: Have you ever gotten rather emotional over a song even though it was on some shitty little radio speaker?

Wayne
 
The whole "not having level controlls at all" is kind of a vague statement, don't you think?

I mean, there are an awful lot of level controls. Which one is that particular post refering to?

Am I supposed to pretend that it has no master level? In this instance, I assume I am to bring the master level up or down by raising or lowering the volume on the individual tracks?

Or does it mean the opposite?

Wish people could talk straight instead of in parables or vague generalities.

From the way I am interperating it, it has nothing at all to do with summing - rather it is refering to the "tracking" stage. And I'm like "duh" - of course you shouldn't be messing with the input levels. Keep those on zero and use your preamp's (or mixer, compressor, whatever) outputs to control incoming levels.

What this has to do with summing, I have no idea.
 
It's been said that just changing the levels in the daw messed with the sound quality.
I'm just passing it along, and hopefully not messing it up to bad in the process.
 
I think we need to put this topic firmly in perspective.

Please note that I am NOT talking down to anyone, but recording is my business, so when I'm talking (in another post) of doing test and finding summing problems, I'm talking about test undertaken on many hundreds of thousands of dollars worth of gear.
Therefore, if you are concerned about audio quality...... believe me, unless you are working on large, expensive, high end pro systems, in special audio environments, summing is likely the least of your problems.

There are many, many elements in a system which cause more damage to audio quality. As I have said about a millon times, digital audio quality depends for 99% on a few things, bitrate, clock accuracy/speed, and converter quality. So unless you recprd in the full knowledge that all those elements are first class - you've got other things to worry about.

However, summing problems are a reality- even tough on most 'homers' monitoring systems - you will most likely not even hear the difference.
So, the best thing is to make it your habbit to work in such a way that those problems are avoided as much as possible.

Where does the summing problem occur? I'll stay away from the technical crap - just focus on straight forward operating reality.
Summing problems do in the main NOT occur if you mix in a DAW. The most audeable problems occur when you are tracking or doing transfers onto a DAW - multiple tracks at the time.
The optimum DAW fader position is level - 0 dB. So when you record multiple tracks at the time (like drums), or transfer multiple tracks onto a DAW, just don't touch your faders, ensure your audio enters your system at an optimum level - so you can keep your DAW faders at o dB. If you do this (mainly by using your pre's, converter inputs etc.), you have avoided the summing problem.

The funny thing is........ in reality we're back to "optimum" operating behaviour for analogue as well.

Conclusion:
1. Summing is likely the least of your problems.
2. A little knowledge and 'good audio habbits' will allow you avoid most summing problems - if you can or cannot hear them.
 
Just one thing sjoko about what you said.....

The more you care about your audio quality the more every little thing counts.

I know you know and mean that... but to clarify this issue that comes up every 2-3 weeks here.

If you take the whole chain from a good musician to a good instrument to a good room to a good pre to good gain staging to a good cable to a good DAW to making the right desicions and every thing else I left out ........It's going to make the world of the difference !!.
Take even a little problem - the more you load on the bus the more the summing problem becomes clearer.

So I ask you sjoko....were does it end on this BBS.... when DOES it become a problem? when IS it important ?!!? When does cheap gear become an issue? Is the answer ALWAYS going to be "it's the song"...(if it is the song then why did I waste SOOOOO much money all these years?:eek:

Why are people talking all day about this sample rate conversion that converter this pre that DAW .....

Somebody tell me exactly at WHAT point is it going to matter.
If its the song, lets all go back to recording on a single cone that goes to the needle that engraves a groove on a flat peice of black junk.

You'll get people arguing and tearing out their hairs about Behringer Versus Mackie but go tell them about summing and it's not an issue for them?
If they can't hear summing problems then they cant hear the difference between a Behringer and a Mackie.

If they dont have the gear or the ability to hear the difference then with out insulting anybody, better they save their money and have fun recording on cheap gear !!! they will have the same amount of fun but save a bundle !
To bad so many follow the herd and go out and buy converters for $1000 when they could use the converters on a Behringer digital pre and get 8 ins at the same time.

That is what I call putting it into perspective.
 
Please define a littel better

I beleive I know what you mean by summing and I also believe that I have experienced something like it. First off, are you saying that summing is something to the effect of the whole being greater than the sum of its parts and therefore, when there is more going on, the ultimate level can be effected. I record on a Mac G4 into Digial Performer through a MOTU 2408. That is the basic set up. I have wondered for a while if I should have a single clock source to contorl everything and if this would improve my ultimate result. I have not considered buying one though becuase I have not yet exhausted the use of what I have and I think that such things are still a bit (pardon the pun) technically over my head. Nevertheless, When I record, I never change the level meters in the Digital Performer console, I change them on the mixer, the preamp, etc. and the sound I get is fine and has no real problems. when I have tried changing the meters on the DAW mixer, I have always experienced problems with distortion. I don't think this is the summing problem you referred to, however, it just seems that digital is a very unforgiving medium and there is little reason to change the fader level at the DAW level. It is the only thing that always causes a bad result. I say all this because when I first experienced this phenomenon, I thought it was my inexperience as an engineer that was causing the problem. Now, I am wondering if a) it is a summing problem or, b) it is an inherent truism of digital recording or inherent functional factor of digital. So, in the end, if Sjoko or anyone else could better define summing and/or the problems with levels in digital recording notwithstanding discussions about improving the signal chain through better converters, clocks etc. this would be greatly helpful for newbies and possibly for seasoned pros as well.Thank you.
 
Your post link isnt working.

I was wondering about this issue myself. If a DAW program lets you go over unity in the software mixer are you actually adding any noise or artifacts?

Or is the maximum fader level on the software mixer actually unity?

I guess this is kinda like "mine goes to 11".
 
Try this one, then- it looks like Sjoko's paste here fell apart on the semicolons that that BBS uses in its search results. That BBS uses semicolons, this BBS doesn't appear to believe that they can be part of a URL:

http://www.recording.org/ubb/ultimatebb.php?ubb=get_topic;f=21;t=000032

Yup- that initially fucked up as well, and I had to go back and edit it to move the url tag after the semicolons. Apparently you can't paste a URL that has a semicolon in it. This BBS stuff is such bizarre software....

Anyway, in case that doesn't work (or stops working), it's in the "Micing, tracking, mixing, and editing" forum from 8/21/2001, entitled "Summing buss headroom/floating point". For me, it appeared on page 16 of that forum in "show all posts" mode.

But but this site and that one are in tarpit mode this afternoon: page refreshes are taking many minutes. Pain in the butt...
 
Does this say that the daw may have a problem doing a (math)level change while inporting tracks that it would not have with the same level changes to tracks if they were already in the daw, or is it more that the levels were simply never optimized going in?

<Summing problems do in the main NOT occur if you mix in a DAW. The most audeable problems occur when you are tracking or doing transfers onto a DAW - multiple tracks at the time.
The optimum DAW fader position is level - 0 dB. So when you record multiple tracks at the time (like drums), or transfer multiple tracks onto a DAW, just don't touch your faders, ensure your audio enters your system at an optimum level - so you can keep your DAW faders at o dB. If you do this (mainly by using your pre's, converter inputs etc.), you have avoided the summing problem.>
 
I just can't believe that anyone who called themselves a professional . . . wouldn't know to keep the faders on their daw up to "0" and thus spurred all this supposed "summing" quandry that's been going on for way too long now. It's just one of those things where you try bringing the faders down a bit and ask youself . . . "Gee, what did I accomplish?" Try, uh, NOTHING. :)

Loser.
 
hmm. well, I guess i won't really worry about this for now. I feel like there is SO MUCH to learn out there just in terms of digital *other* than just learning how to have amazing mic placement etc.

Gonna get there though....anyone know off hand -

the new U2 album, "All That You Can't leave Behind" - if it was recorded digitally? or...a mix of both maybe?

I really love the sound of that record - something about it "sounds" digital to me...but, that's just a stupid thing to say. Just becuase it sounds very clean...etc.

I looked around on the net for some info on it but could not find any.
 
chessrock said:
I just can't believe that anyone who called themselves a professional . . . wouldn't know to keep the faders on their daw up to "0" and thus spurred all this supposed "summing" quandry that's been going on for way too long now. It's just one of those things where you try bringing the faders down a bit and ask youself . . . "Gee, what did I accomplish?" Try, uh, NOTHING. :)

Loser.
Click to expand...

It has nothing to do with unity gain as in a pro DAW like PT they jump to unity gain automaticly so the "loser" who had hear the problem, heard it with no connection to the faders moving.

Yes the faders being moved will effect the sound as well but the summing is all about trying to sum on the same buss a load of information and comming out witht the same result at the end of the buss.

In any case were you try to output in the mixer (software) more then two tracks you will get the summing problem. The more tracks you load the worse it gets. Just do a little panning and you have some summing, even if the faders are at Unity. Just output the tracks even with the faders at unity through your main output and you will hear the summing. Send you tracks to a group and you have summing.
If you output via the seperate outputs then that a different story
That is the way I understand it and HEAR it.

Not to mention the DAW also suffers from combining the tracks to a single stereo file making the "save on the HD" not worth while if you wish to obtain the authenticy of your original mix.

So it's not just all about some faders at unity gain or not.
It's about mixing on a software mixer.
 
I'll restate the question simce I didn't direct it well the first time.

<sjoko2 said
Where does the summing problem occur? I'll stay away from the technical crap - just focus on straight forward operating reality.
Summing problems do in the main NOT occur if you mix in a DAW. The most audeable problems occur when you are tracking or doing transfers onto a DAW - multiple tracks at the time. >

Does this say that the daw may have a problem doing a (math)level change while inporting tracks that it would not have with the same level changes to tracks if they were already in the daw, or is it more that the levels were simply never optimized going in, and are thus dammaged?
And this is a summing issue? I thought that the various conversations floating about with regard to summing were directed squarely at the the issue of combining multiple tracks and the the resulting errors and/or distortions, good or bad, whether dig or analog mixing.
Wayne
 
Shailat's response above is essentially correct. It is very difficult to explain this stuff simply, because every response would require further explanation.

Shailat also stated correctly that summing occurs with every action you take within a DAW. However the most audeable effect can be heard when entering a DAW incorrectly - and when exiting through a LR bus.

The above is a key reason why I always advocate to write a track full when recording on a DAW (despite the many people who tried to hit me over the head for it over here in the past).

Let me try and explain the reason why summing problems occur. Please note, I say summing problems. Summing itself is something you always do, its not a bad thing, its just combining multiple tracks basically.
It is a misunderstanding to think that summing occurs because there is "to much data going through a bus", it all has to do with a DAW's fixed point processing, as opposed to floating point processing, which is something you find in high end gear like for instance, Stagetec and Euphonics digital consoles.
Just imagine you record something on a DAW at 24 bit, at unity level. Now you have twentyfour bits of data at unity. Now grab the fader and reduce the level, say by about 40dB. If you do that in a floating point system, you still have a 24 bit signal at 40dB lower level. In a fixed point system you will now have a 17 bit signal, even when you move your fader back up to unity again.
This is what occurs within a fixed point DAW when you are mixing and when you are mixing tracks down to a stereo pair.

Of cause there are solutions, personally I get very good results by doing a lot of grouping and exporting groups out of the DAW and importing them again through a sample rate converter, without going through a conversion.

In other words, its getting complicated again, goodnight!


I'm going to leave it at that :)
 
Fair enough.:)
I was just curious about the input level change vs after it's in.
And this is apparently not the same as just not getting opt. level at the AD.
Thanks for responding. We're always learning as we go.
Wayne
 
Christ, now I'm getting confused. I think what we are all looking for is the best method for doing dumps of multiple tracks and mixdowns.

Can you tell us what not to do? Obviously we have to use a master bus at some point in the mix down so summing has to happen. Is this one of those esoteric points that we are obsessing over too much?
 
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