Sub60hz mixing...

[aikan]

Quote (Bubbagump @ July 12 2005,20:24)

You are hearing the harmonics which are multiples of the frequency… perhaps two or three times the fundamental. I can almost guarantee the mda plug is adding harmonics above and beyond those in the subsonic level… I actually happen to think the sub part is probably the least of what the plugin does. Quote Distort Takes the existing low frequencies, clips them to produce harmonics at a constant level, then filters out the higher harmonics. Has a similar effect to compressing the low frequencies.

i totally forgot about harmonics! that makes a lot of sense.

you have reminded me that a lot of times i’m not really hearing what i think i’m hearing (or i think i’m hearing something that i’m really not). it takes a while to learn that and the spectral analyzer is a lot of help for that – i started using it on that same electronic album, and did indeed high pass every track cause the super-lows were kicking up to like +30dB (the sub synth, now that i think about it, was on a different project).

speaking of the sub synth, where’d you get that description of it? i couldn’t find the docs on the mda

(also, i’d like to mention that i am aware of the need to have an honest listening environment, but i didn’t realize that subwoofers were not likely to be honest. if nothing else, i guess it’d be handy to have around for checking mixes on.)

anyway, thanks for the help! i keep forgetting how little i really know about this stuff.

[Willy]

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I wonder if most would agree that applying, say 4" foam directly behind them would help with the situation.

Might help. I’ve for two inches of semirigid fibreglass almost behind mine for killing reflections, although the yorkies are about 1 1/2 feet away from the wall.

[TomS]

Quote (aikan @ July 13 2005,23:10)

you have reminded me that a lot of times i'm not really hearing what i think i'm hearing (or i think i'm hearing something that i'm really not). it takes a while to learn that :/ and the spectral analyzer is a lot of help for that -- i started using it on that same electronic album, and did indeed high pass every track cause the super-lows were kicking up to like +30dB (the sub synth, now that i think about it, was on a different project). speaking of the sub synth, where'd you get that description of it? i couldn't find the docs on the mda :/ (also, i'd like to mention that i am aware of the need to have an honest listening environment, but i didn't realize that subwoofers were not likely to be honest. if nothing else, i guess it'd be handy to have around for checking mixes on.)

Actually looking at the mix is a must, IMHO. Do the same with some professional stuff you really like, and see what it looks like. There are also things out there that will give your mix the same freq curve as another recording, like the Harmonic Balancer thing reviewed here (I think phoo has some experience with it, I tried it but it seemed a bit costly for me):

http://www.soundonsound.com/sos....da4d7bf

Also, having a sub woofer to check mixes is a very good idea, seems to me.

[Bubbagump]

Quote (Scantee @ July 13 2005,19:26)

As I said, I can understand how room reflections can cause issues with harmonics, cancellation, etc., but room aside–in some open space outside, for example–I can’t see how sitting 2 feet or 20 feet from the subwoofer could affect the accuracy because the “sound is not completely FORMED”; the only thing I can see happening is the sound weakening over increasing distance. Your eardrums are points in space, and eventually each “wave” will “pass by” in its entirety as long as you’re standing still within earshot, no? Yes? Again, what I’m saying doesn’t deal with room reflections–once you’re in a room or put some closed-back headphones on or whatever, yes, I understand that all kinds of weird things start happening. Tony

Let’s not forget reflections… You ear cannot determine direction with bass frequencies. So many times what you are hearing is the bass as it is coming back from bouncing on the walls… maybe even the walls in the next room.


Please read this to get a better understanding of what I am talking about. You have to understand nodes etc. to get the whole picture. All that to say, you are not hearing the low bass in its pure form due to reflections. What you are hearing is adulterated… (I love that word… adulterated. )

Look at the first graph, notice it bounces off the wall and then comes back to the listener for the wave to be fully formed. This is what you hear in a small room, this bouncing back. Then you mix that reflection with direct field sounds, phase cancellation, other bass waves bouncing back, etc… your bass has just been butchered.



And Tony, unless there is a fully complete wave form, there is no sound. If you only get 1/4 of the way through the periodicity, you won’t hear the tone… really. Make a pure sine wave at 40 hz, go into an open field while standing 2 feet from the source, and play it back. What you hear, if anything is bouncing off the ground or from some tree… Really.

[billthecat]

So, when I go to Guitar Center, should I feel safe and secure that the monitors I’m listening to (remember: I’ve brought my copy of Sting, et. al --music which I’m really familiar with) is devoid of these standing waves and has sufficient bass traps? Can I be confident of purchasing a piece of equipment based on what I hear at GC?

I’ve got that funny feeling that if I asked the pimple-faced-grunge-rock-kid-with-the-half-pack-of Winston’s-in-his-Mega-Death-T if the room was sufficiently trapped, he’d look at me like a mule looking at a new gate and say something like “I think so”.

[Bubbagump]

Can you be confident, no. One other piece I did not mention is walking around. Don’t just stand in one place. Walk around and listen. Get the pimple faced kid to leave you alone and take your time. Unless you have immense amounts of money, this will never be an exact science. Don’t over think it. When you go to hear monitors, some will expose flaws right away and others will be much more what you are looking for. Even better, see if you can find a proaudio shop in town (AKA, locally owned, no pimple faced kids, they actually do this for a living vs as a summer job, have treated listening spaces, etc.) and listen. The extra $20 you spend at a place like that may be worth it.

[Scantee]

Quote (Bubbagump @ July 14 2005,06:32)

And Tony, unless there is a fully complete wave form, there is no sound. If you only get 1/4 of the way through the periodicity, you won’t hear the tone… really. Make a pure sine wave at 40 hz, go into an open field while standing 2 feet from the source, and play it back. What you hear, if anything is bouncing off the ground or from some tree… Really.

Thanks for the article link, Bubba. Though it’s focused on room reflections, the author says this:
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In a free field with no boundaries, you could stand at any reasonable distance from the speaker and hear flat, even bass, because the alternating peaks and valleys just keep going right past you, no matter where you stand.

I understand and agree completely that if you don’t get through the entire period of the waveform, there is no sound. What I’m saying is that even at a distance less than the sound’s wavelength, the entire waveform would reach your ears eventually even without reflections, as the waves of changing air pressure move like ripples on water and propagate through the air.

Ok, get ready for my own scientific graphic link :

Reflections/cancellations aside for now, the only way I could see the complete waveform not reaching the ear would be if sound did not propagate through the air. But it does, and I would think that this sound without the reflections would be as unadulterated, untouched, pure, virginal, etc., and as it gets.

I completely comprehend that reflections are a reality, and that in every situation we deal with in daily life, there will be reflections, and we must account for them when recording and listening. Even floating in some infinite air space with nothing but me and a subwoofer, there would be reflections off me and the subwoofer. But I don’t see how reflections would be necessary to hear something at a distance less than the wavelength of the sound.

And if I’ve completely misunderstood what you’re saying, then just shoot me.

Tony

[Ali_G]

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And Tony, unless there is a fully complete wave form, there is no sound. If you only get 1/4 of the way through the periodicity, you won’t hear the tone… really. Make a pure sine wave at 40 hz, go into an open field while standing 2 feet from the source, and play it back. What you hear, if anything is bouncing off the ground or from some tree… Really.

I know what you’re saying Bubba, but I’m not sure that I entirely agree with how you’re saying it, and I have to agree with Tony here.

The ear cannot tell the difference between 'field" effects and “waveform” effects. As far as it is concerned, it’s just pressure variations. And if the field effects contain sufficient power, you’ll hear them.

It’s like a radiating antenna; near the dipole you don’t even think about travelling waves, just the near field, but that near field will still fry you!

Or think about a pair of cans for a wee minute.

Distance between transducer and eardrum; approx 2 inches, which is about the wavelength of a 6kHz wave.

I know my cans go a lot lower than that.

I know that a lot of the acoustic amplification in the bass region is due to the fact the the cans are enclosed, but that is fairly insignificant in the mid area.

Or think about sitting close in front a speaker with an SPL meter, and that speaker vibrating at 20 HZ. That meter willl tell you pressure variations are happening. And if you don’t believe it, throw it away, and just stick your face close, you’ll feel the draught!

So, near field effects are important, but as you say, in the bass area especially, reflections, or more importantly, standing waves, tend to dominate.

Ali

[Ali_G]

But to get really controversial…

I’d argue that we don’t “hear” any music down in the bass region at all.

So, here’s my argument:

(1) Our frequency discrimination is very poor at LF.

(2) Down low, it’s often difficult to tell whether one is hearing a sound or feeling it.

(3) I can quite clearly hear a bass run by Jack Bruce, and identify the notes, on my wee portable tape machine, and its lower end is no better than 200Hz.

(4) LF provides no spacial information, neither of direction nor of distance.

(The reason for (3) of course is due to two factors; the difference tone between the upper harmonics, and the “missing fundamental” factor added to the difference tone phenomenon.)

OK, so I’ll change my argument slightly; there is music down there, but what it is, is “tonal quality”, and only tonal quality. Everything else “musical” is added by the upper harmonics.

And returning to the original post, that tonal quality is more determined by the listener, his equipment and his room, than it is by us. We can get a good tonal quality on our gear, but hoping that it can be passed on to others is still more hopeful than anything.

Anyway, items (1) through (4) can easily be confirmed by experiment.

My conclusion however, is merely my opinion, and is undoubtedly a load of old bollox.

Ali

[Bubbagump]

Quote (Sceptic Tank @ July 14 2005,14:07)

And if the field effects contain sufficient power, you'll hear them. It's like a radiating antenna; near the dipole you don't even think about travelling waves, just the near field, but that near field will still fry you!

Thank you, yes, much better said.

[Scantee]

Quote (Sceptic Tank @ July 14 2005,11:07)

It’s like a radiating antenna; near the dipole you don’t even think about travelling waves, just the near field, but that near field will still fry you!

Nice analogy, Ali. The audio equivalent might be that when a subwoofer is cranking a 60Hz tone at 140dB with nothing around to reflect the sound back at you, putting your ears 2 ft from the subwoofer won’t save them!

Tony

[Ali_G]

Sorry Tony, but this time you’re absolutely wrong.

60Hz is a special case because it’s a prime sub multiple of the 1st Balmer Hydrogen Line. (Strangely enough, it’s also a prime sub multiple of the resonant frequency of earwax.)

So, in your example, sitting close to your speaker in your reflectionless environment with your hydrogen filled body (and earwax), you would indeed hear nothing.

However, taking into account the world is round; then approximately a day and a half later as you sit contentedly eating your Cheerios, the sound will zoom around from behind you and blow your f***ing socks off!

It’s the acoustic equivalent of Karma (but with slightly less curry).

[Scantee]

Quote (Sceptic Tank @ July 14 2005,21:07)

Sorry Tony, but this time you’re absolutely wrong! 60Hz is a special case because it’s a prime sub multiple of the 1st Balmer Hydrogen Line. (Strangely enough, it’s also a prime sub multiple of the resonant frequency of earwax.)

Oh, I’m sorry…I meant to say 60.013Hz. My mistake!



Well, with this, I guess the Forum Correctness Cancellation Phenomenon will now cause my previous, lonesome, “right” to be “muted”. Oh well, it was good for my soul while it lasted. I’m ready to go back to being my good ol’ wrong and confused self again!

Tony

[Ali_G]

Don’t talk about 60.013Hz Tony.

You checked the resonant frequency of the gonads?

[Scantee]

Whoa! Expect spam from me soon regarding my new 60.013Hz ummm…invention!



Tony

[system]

a special thanks to Scantee and Septic Tank for bringing a note of sanity (60,013Hz) into this thread. I wonder what 60,013Hz would sound like in a septic tank, kinda muddy I guess.
cheers

[crazy-trousers]

Excellent thread.

Should I get a sub to complement my nearfields when mixing?

[Ali_G]

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Should I get a sub to complement my nearfields when mixing?

Well, you gotta cut a hole in the ceiling for the periscope, and that can be a wee bit of a pain when it rains.

Ali

[TusterBuster]

I’ve been enjoying this thread. I love this forum!

A while back Sweet asked about pink noise. It is one of the two types of random noise used in audio as a broad spectrum signal that can be used to test frequency response. Lets see if I remember something… I hope someone will correct me if I’m wrong.

One way to test frequency response is to generate a constant level sine wave and sweep it through the frequency range. Another is to generate a signal that effectively contains all frequencies all the time (gaussian random noise) and do a fft (fast Fourier transform) spectrum analysis. That’s what white and pink noise are often used for.

White noise has a flat signal level across the spectrum and is usually used for checking electronics. Pink noise has flat signal power density across the spectrum and is often used for checking loudspeakers. To our ears, pink noise sounds more bassy / rumbly, while white noise is more hissy. It’s called pink because of this weighting towards the low end, as an analogy with light; pink light has more lower frequencies than white light.

Hope that helped. Cheers
TusterBuster