The Grateful Dead's Wall of Sound
motherboard.vice.com
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Much of live sound today sounds pretty poor and a great sound tech and producer, Lennart Östlund from the ABBA Polar Studio, told us (small workshop on mixing) that the cure was exactly what the Dead did. A PA per instrument. If you can't do that at least split the vocals to a separate system. Which he had actually tried with great success several times.
I also have a hard time believing that a separate system will make it sound better. You still need to adjust the level of each PA to create a good mix.
You hardly ever pan main vocals anyway, so you're normally using your stereo pair to produce a mono sound. In other words, both speakers are producing the same sound at the same time. Since hardly anyone in the audience is an equal distance from both speakers, they'll hear a messy comb-filtered version of the main vocals, rather than them cleanly.
You can make a very good argument for not bothering with stereo at all for live sound (except for effect stuff, but then we're back into separate-pa-for-each-instrument grounds...). The trouble with that is how much harder that is to rig. If you're stacking stuff on the ground at all, then you can't really stack center stage, you need to stack to the sides. (Or behind the stage, with all the feedback issues that involves). If you do fly your PA, then you still need legs, usually. And a big PA is stinking heavy, and flying it near the legs is a lot easier than near the middle, due to lengths of truss, loading points, etc.
I've never tried it personally, but people who's ears I trust all say that besides all of that, just using a secondary sound system for vocals still makes them come through a lot clearer and everything sound better.
One possible reason for that is that a speaker is essentially just a paper cone with an electromagnet on it. There are physical limits on what that one bit of paper can do in terms of vibrations. We like to pretend the world is a lot more digital and measurable than it really is. By separating out the vocals from the other instruments, you allow the speakers to only move when the vocalist is singing. I can see why it could be cleaner. I believe the Chilli Peppers may be doing 2 PAs at the moment splitting off the vocals to their own mix...
You'll still always need a good sound guy, and you'll still need somehow to control the (vocals:instruments) ratio in the audience.
Ideally, bands would think of the sound guy as a member of the band. Kind of like the conductor of an orchestra is a vital member of the orchestra. A good sound guy is very similar. A bad sound guy has all of the same control, but none of the feeling.
They did this by using two microphones, using one of the microphones for the singer, the other for the background noise. By inverting the phase on one of the microphones and then summing these two signals they filtered out the background noise. At least this was my understanding.
Sometimes it's really great how far we have come with technology and what tricks they've used in the past.
@good sound guy: you're absolutely right - but most of the good and / or big bands have their sound guy anyways.
I always wondered if it still sounded natural, or if there was some kind of comb-filtering to the vocals that just didn't matter due to the style and volume of the music.
I've played with multiple out of phase mics myself (to try and reduce drum bleed from the main vocalist mics) but never found it as effective as I'd hoped.
I think the problem was just how stinking loud the ambient drums just in general were to the room. Maybe outdoors with a bigger rig it would have worked.
Still pretty fun to play with though.
There's so much mad stuff you can do when you start playing with out of phase mics, delay, etc. As a party trick I occasionally pull a mic up to the point of feedback, whistle until I have a stable loop, and then can whistle in harmony with myself.
You can tell what kind of parties I go to...
But I think it was a big improvement to what they had before.
It's probably on Youtube, so you can listen and judge yourself ;).
I know one example of this: Front 242. Bressanutti (the group's founding member / reclusive "mastermind") would man the mixer for live performances.
Said this to a friend (who was standing some metres off) and he said everything sounded fine for him. Went 3 metres to the right and suddenly I've heard the bass player. Talked with the sound guy afterwards and he said that the PA simply sucked. Never heard this so extreme.
I would say it is a thing of many factors: the PA, the band (their equipment) and of course the sound engineer.
Saying a PA system 'just sucks' is a bit of a blanket statement. Given how incredibly complex audio actually is, and how little people want to pay, it's sometimes surprising it works at all.
(I'm not trying to be defensive here, or argumentative, in case it sounds that way...)
Yes - a lot of PA systems are cheap, nasty, and stupidly designed, but quite often they're fine - just our expectations of what is possibly with them is somewhat against physics.
Bass is pretty unintuitive. Due to the very long wavelength (100hz is around 10ft give or take), if you try and use a stereo system to produce bass frequencies, you do get all kinds of troughs and peaks where the system ends up cancelling things out. Peak sound from one speaker reaches a point in the audience at exactly the same time as trough sound reaches that same spot, and the sound is cancelled out. Half a meter away in one direction, you get both peaks, and they add together, and half a meter in the other direction and you get something else weird. And this happens differently with every single frequency. Above 200-300hz or so you stop really noticing it, but below that it's horrible.
A lot of that can be solved by using a single point source for subs (bass), thus the 2.1, 5.1, etc systems. (The .1 means a separate bass subwoofer).
The trouble with doing that with a large enough system, is that you now have phase issues between the subwoofers, and the mains.
Say your subwoofer is set to only reproduce sounds up to 100hz, and your mains are set to only produce sounds above 100hz... You still have an area where both the mains and the subs are producing that sound. It isn't a binary state of producing or not producing sound.
So if the subs are (say) 20ft from the mains, (in a triangle configuration, with the subs on the floor) then you still will get phase issues with either full out cancellation in places, or else very messy comb filtering which also sounds crap.
Sound moves quite slowly (again, extremely roughly, 1130ft a second). So say a guitar is coming out of both mains, and because you're slightly to the right of stage you are 10ft closer to the R than L, you hear the sound twice, first from the R speaker, then 10ms later, from the L. 10ms is right on the border of you being able to tell it's a separate sound, so it doesn't sound like an echo, just a single slightly muddy sound, coming from slightly left of the main R speaker. (Wikipedia the Haas effect, if you're interested). This is one of the problems with stereo sound for a big live PA - only very few places in the audience will actually be able to experience the stereo effect - most will only get mono, realistically.
In a small domestic system where the mains are only a few feet from the sub, you don't notice it. In a big set up, you do.
You can get around a lot of that by flying your subwoofers. But then, as you don't get the 'floor carrying the bass' effect where the sound is literally moving along the ground, you need to use much more powerful bass amps and speakers to get the same kind of feeling.
My preferred solution is called 'aux fed' bass, where you send sound to the sub(s) from a separate mix than the main L/R speakers. Then I'll send the bass, kick drum and perhaps a few other things directly to the subs, and nothing else. This has many advantages, you get a lot less of the 'pop' sound from microphones when people are talking, the bass tends to sound a lot cleaner (as the speaker isn't vibrating along with every other sound), etc. However, it's a lot more complex to set up, and if you're playing back backing tracks or pre-recorded music that isn't mixed for it, it'll usually sound quite messy.
This is where the separate PA per instrument thing can help.
The trouble with that is how complex it is to control, how much space it all takes up, sight lines, and so on.
The article really didn't go into how hard it is to stop feedback when your speakers are behind the mics. That's why they had all that insane multiple mics out of phase stuff.
That's why we normally put the main speakers in front of the stage. You want them as far away and pointed as far away from the microphones as possible.
But if they're in front of the stage, then you want them as small and out of the way as possible, so as to not muck up people's sight of the stage / screens / lighting, etc.
At the end of the day, live sound is all about compromise. There are no perfect systems, rooms, bands, audiences, or engineers. If possible, we try to make as many people happy as we can. If that includes whoever is paying us, that's usually good. If it includes the band, that's even better. If it includes the audience, well, that's just a bonus, really. :-) (It'll probably never include the sound engineer. We're all grumpy old sods and never happy).
I get new headphones. Yay! I plug them in, I start listening to music.
Something sounds... odd. I can't quite put my finger on it. Then I load up a track and notice that the vocals are missing. Completely. The backing track's there, but the singer isn't. I switch back to my old headphones. Yup, the singer's there. I call my cow orkers over to verify that I'm not simply going mad. I'm not; they hear it too.
What was happening, we eventually discovered, was that I hadn't noticed that the headphones used a three-ring jack rather than an ordinary two-ring stereo jack, and when plugged in to a two-ring socket, the left and right channels were being shorted together. Because the singer was in the centre of the mix, his vocals were in opposite phases in the two channels, and were therefore cancelling out. The backing track was offset left and right from centre, and so weren't.
Phase artifacts are weird.
The difference is astonishing - much more significant than you'd expect if you're used to thinking of volume as a function of power. It was an awesome wall of clear, clear sound, and we had to keep it turned down a fair bit in order to keep from driving people out of the dance area. 100 more watts doesn't seem like much, but separating sound-reproduction responsibilities among three different amps clearly makes a really big difference.
I did notice some of the problems the article describes with stereo, though. There were definitely parts of the field where you could hear one side but not the other, and it was distracting. We clearly have more to learn about this whole business.
Just by chance you crossed the diamond with the pearl,
You turned it on the world,
That's when you turned the world around.If you never been in one, I highly recommend. Very different experience. They are usually somewhat underground so takes some research into what dub and reggae is.
He's the sound guy for the Red Hot Chili Peppers, among others, and it currently testing out a double line array system - with separate systems for vocals and instruments.
Audio is cool, and the rabbit hole on it goes really, really deep.
For instance, I learned that Kalliope uses something called a cardioid array for its subwoofers, meaning that some of the speakers are pointed forwards (towards the crowd), and some are pointed backwards (away from the crowd).
The result is that the pressure created by the subs pointed backwards is collapsed by the pressure wave created by the subs pointed forward.
(Alex, the audio engineer calls this a warp drive).
The amount of thought that goes into designing some of these things is astounding to me. Building PA systems is NOT a matter of plugging speakers into amps and pointing them where you want them, and making loud sound systems is NOT a matter of getting more speakers.
Explains why Garcia had no time to learn fingerings outside of the pentatonic box. :)