Blind Taste Test: Passive Summing vs ITB

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Blind Taste Test: Passive Summing vs ITB

Post by spacelabstudio » Thu Sep 30, 2010 12:17 pm

Hi Folks. This could have gone in any number of a the forums on here--it seems to defy category. But I picked here. ;)

I built a passive summing box. You know, the kind that are all the rage these days. Easy/cheap to build and lets you mix OTB. Basically a DIY Folcrom, designed to plug into a pair of mic pre channels for make up gain.

I'm trying figure out what I think the results actually are and have concocted a blind listening test to see what people think without their prejudices getting in the way. What I've done is I took a track I mixed recently for some friends of mine and made several new mixes. I was particularly interested in isolating the effect of just running the tracks through an extra D->A and A->D conversion with a mic pre in between, versus actual analog summing, so I have one mix that is the ITB mix run through the passive summer and a Sytek preamp in addition to a mix that actually bust instruments out onto separate channels before running through the summer. I also, of course, compared the sounds of different preamps in my collection.

The mixes are:

- ITB, everything mixed in the computer
- Mixed ITB, run 2 channels through Sytek
- Mixed OTB, Sytek
- Mixed OTB, Sytek Burr Brown
- Mixed OTB, RNP
- Mixed OTB, Great River
- Mixed OTB, Hamptone Tube Pre

Since I had previously done this mix entirely ITB and happened to have a software compressor across the drums, I took the lazy route and brought the drums out as a two channel stem rather than mix individual drum mics in the passive box. So on the tracks mixed OTB, what you're really hearing is the drums, bass and guitar mixed as stems. There is a spring reverb on the guitar and a software reverb on the drums that each got their own channels on the summer as well.

I have then taken the first 30 seconds of each mix, shuffled randomly, and posted them here:

http://spacelabstudio.com/passive_summing_fixed/

Anyone who would like to play should just reply to this thread. I'm interested in hearing:

1) Which version to you think sounds the best.

2) Can you describe the differences that you hear between the versions?

3) Which wav files do you think are which mixes? Can you match them up?

It would be great if you didn't read other people's responses before taking the ITB vs OTB challenge.

Thanks all!

Chris
Last edited by spacelabstudio on Fri Oct 01, 2010 5:47 am, edited 1 time in total.

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Post by nordberg » Thu Sep 30, 2010 3:41 pm

i don't know what's what, but my favourite is 7. followed not so closely by 3 and then 1.
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Post by eeldip » Thu Sep 30, 2010 7:05 pm

7 has some sort of different phase relationship than the other ones. my guess is that its some sort of hardware phase fuck up that sounds good.

the rest of them seem to have very very very minor differences in soundstage and tonal balance. i really don't have a favorite out of the rest of the six. it would probably depend on the day of the week and how much treble i was enjoying that day. or if i wanted slightly more focused or slightly wider soundstage.

i would say, that whatever is going on with 1-6, the differences aren't worth much fuss.

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Post by redmoon411 » Thu Sep 30, 2010 7:46 pm

I agree that 7 sound the most different, kinda mono, but I think that 6 has the most clear sound.

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Post by Peterson Goodwyn » Thu Sep 30, 2010 7:46 pm

Thanks for uploading this, it's really fun to listen to. One note, though: these aren't very well volume matched. #3 is more than 1 dB louder than #2.



I was suprised how different the stereo image was between them.
#7 sounded kind of murky and mono, but with a lot of attitude in the low end. I like the saturation on the bass, but don't really like this one overall because of the lack of clarity and stereo width.
#3 The plucking guitar on the right sounds louder than in the other mixes. Which, to me makes the image more balanced than some of the others, which I like. Overall I like the spectral balance of this one a lot.
#5 has a nice clarity and distinctness to each element. Probably my favorite.


I am reluctant to pick a favorite, because I generally liked the louder ones best.
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Post by vvv » Thu Sep 30, 2010 8:24 pm

Listening in 7506's, I like #2 the best as it seems a bit cleaner, neutral ... ?

#7 is louder, but more of a mono image?

#1 sounded dead.

#'s 3-6 are pretty similar, even # 2, to me.

I did D/L the files and listen to 'em thru the irfanview player.
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Post by spacelabstudio » Fri Oct 01, 2010 5:55 am

It is with deep embarrassment that I am forced to admit that in the rush to play with my new toy I completely failed to notice that one channel was out of phase with the other in all of the mixes that passed through the summing box. I apologize humbly for having had you listen to f'ed up mixes. Listening this morning, the error was pretty obvious.

I have used a wave editor to flip the phase in the right channel of each wav file. And I have rerandomized the ordering, so they are now in a different order again. I have changed the url above, but here it is again:

http://spacelabstudio.com/passive_summing_fixed/

Sorry about that. Some days have more fail in them than others.

Interestingly, most of you seemed to prefer the out of phase mixes.

Chris

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Post by chris harris » Fri Oct 01, 2010 7:02 am

spacelabstudio wrote:Interestingly, most of you seemed to prefer the out of phase mixes.
That's exactly why these blind, gotcha tests are mostly useless. The reason most of the people chose the out of phase mixes is because most of them would have mixed the song with a bit wider of a stereo image than you did. It's still so subjective, even in a blind test, because it's more about "how would I have done it" than it is about "which one of these sounds 'better'"?

These "tests" can be interesting just from the perspective of hearing the same thing passed through different gear. But, they don't really teach us anything about what might be "better" or what would work better in our own hands. In fact, in your attempts to keep things "scientific", you've made the results even less useful. So much of the value of a piece of gear or a technique lies in how we AS INDIVIDUALS put that gear or technique to use in real world scenarios. A more useful, though less scientific test, would be for you to mix a few songs ITB and get them sounding as good as you can. Then, mix the same songs again, starting from scratch, THROUGH your summing box. This test would tell us more about how the two methods influence the way YOU work and the results that YOU can achieve.

The one thing that I almost ALWAYS learn from these "tests" is that I would almost always have done something differently than the person administering the test. This instantly disqualifies their results from being relevant to my day to day engineering life.

A test like this doesn't necessarily show you what a piece of gear or a technique can do. It shows you what the gear or technique did do in the hands of someone else.

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Post by jnTracks » Fri Oct 01, 2010 7:37 am

wow, this is hard.

ok, on my personal (not studio) computer. with 7506's

my first listen through: 1 and 5 seemed less clear somehow and came away thinking 2 was the best. then i listened to them again and, now i'm all messed up and i can't be sure i hear a difference in any of them.

jeeze.... so for what that's worth.
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Post by eeldip » Fri Oct 01, 2010 8:12 am

eeldip wrote:7 has some sort of different phase relationship than the other ones. my guess is that its some sort of hardware phase fuck up that sounds good.
.
this was the ITB one... LOOKS LIKE YOU ARE WRONG.

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Post by eeldip » Fri Oct 01, 2010 8:17 am

subatomic pieces wrote: That's exactly why these blind, gotcha tests are mostly useless.
i think this test proves that summing for the sake of summing, and passing signals through hi fi preamps that aren't being pushed, is a game of millimeters.

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Post by spacelabstudio » Fri Oct 01, 2010 8:31 am

subatomic pieces wrote:
spacelabstudio wrote:Interestingly, most of you seemed to prefer the out of phase mixes.
That's exactly why these blind, gotcha tests are mostly useless.
Well, there is a widely touted claim that analog summing is better than digital summing. It is also a well known phenomenon that expectation conditions perception--we often hear what we expect to hear. This test is designed to test the widely held belief that adding signals together in the analog domain is going to sound better than adding them in the digital domain. Testing the differences between different types of make up gain is kind of a sideshow.

There are other factors, as you point out, that might impact the end result. I might be more prone to plug in outboard gear if I'm doing external summing. As a semi-scientific experiment, though, I need to focus on a single hypothesis and as simple a controlled test of that hypothesis as possible. That's more or less how scientific experiments work. If there wasn't such a widely held belief that merely moving the summing into the analog domain versus the digital was going to have some profound effect on the sound quality, then this experiment wouldn't be nearly as interesting, but the community has put forward this hypothesis, as it were. I haven't seen anyone put it to a truly blind test. I'm already seeing some interesting results from this experiment. Interesting to me, anyway.

FWIW, I've shuffled the tracks in such a way that even I don't know which is which for the time being, and I'll be administering the same test to myself shortly.

Thanks!
Chris

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Post by roygbiv » Fri Oct 01, 2010 9:09 am

spacelabstudio wrote:....This test is designed to test the widely held belief that adding signals together in the analog domain is going to sound better than adding them in the digital domain. ...... As a semi-scientific experiment, though, I need to focus on a single hypothesis and as simple a controlled test of that hypothesis as possible. That's more or less how scientific experiments work....

Indeed, well put. +1

Thanks for doing this. It it is indeed a very interesting test of the hypothesis that "OTB mixes sound better because (and only because) they have been sent outside of the box".

To me, your results suggest there are more variables to it than that. Perhaps workflow issues as you and subatomic suggest, gain staging, other hardware, etc.

Doesn't mean that summing is not useful, just that under these defined conditions, other factors are likely more important.
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Post by vvv » Fri Oct 01, 2010 10:13 am

Aiight, thru the 7506's again, for consistency:

No preference.

Thru Tannoys: no preference except not #3 as the snare sounds somehow weak.
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Post by chris harris » Fri Oct 01, 2010 11:05 am

spacelabstudio wrote:Well, there is a widely touted claim that analog summing is better than digital summing.
Possibly in the advertising world... but, in the real world, and especially where "science" is concerned, this isn't a "widely" held belief at all.

The more accurate, and widely held, and CORRECT claim is that analog summing sounds DIFFERENT than digital summing.

Your "experiment" can and does prove that. But, it cannot and will not prove or disprove something that is subjective like "sounds better".
spacelabstudio wrote:As a semi-scientific experiment, though, I need to focus on a single hypothesis and as simple a controlled test of that hypothesis as possible. That's more or less how scientific experiments work.
Real scientists would find this hilarious! You cannot prove or disprove something that is subjective. Calling what you're doing "science" doesn't make it any more scientific.
spacelabstudio wrote:If there wasn't such a widely held belief that merely moving the summing into the analog domain versus the digital was going to have some profound effect on the sound quality, then this experiment wouldn't be nearly as interesting, but the community has put forward this hypothesis, as it were. I haven't seen anyone put it to a truly blind test. I'm already seeing some interesting results from this experiment. Interesting to me, anyway.
Of course. Your test proves that changing the signal path has SOME effect on the sound. I don't really think that was ever a disputed fact, though. And, I can assure you that you're not the first to put it to a test. There are dozens of these tests, some administered much more "scientifically" than yours, both here and at Gearslutz.

Changing the signal path will OBVIOUSLY have some effect on the sound. Whether or not that change is "better" is subjective. And, whether or not that change is subtle or obvious, the change exists. And, it informs and affects the way that we mix.

The loopback test can really only prove something that's not really in dispute. That is, that the resulting sound is different. It can also prove what eeldip noted, that there's no magic box that will change the game by simply running the same signal through it. But, those subtle differences can turn into something much more significant if you actually mix INTO the process, rather than just taking the same signal and passing it through. And, those differences can manifest themselves in "better" sound, or improved workflow, or any number of things that cannot be proven scientifically.

You mix with your ears. Not with boxes and GUIs. You mixed this with your ears FOR the way it sounded ITB. Then, you take the same mix, and apply it to a different process or circumstance and expect that it's a fair test of how that process or circumstance measures up. That's definitely not science. And, my main point is that even if it was, it wouldn't be very relevant to how most of us work.

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