i plan on getting this job done for locals by placing an ad in the newspaper, but i only plan on traveling in a 30-40 mile radius.
since i cant physically be there for everybody (and those that i can be there for might already have a calibrated microphone) i figure i will share with you, and maybe together we can heighten the experience of movie watching togther.
first of all let me point out the importance of getting your microphone calibrated, because i too used a microphone that was an analyzer mic but wasnt calibrated.. the difference after i got it back from calibration was remarkable to say the least.
(it allows your tool and your time to be less than a waste, because without the calibration.. the results are worthless, and sometimes the final result is worse than if you would of simply left it alone.)
i recommend putting each front speaker in the corner of the room to allow the room to fill up with sound.
because when the front speakers are placed closer together, the properties of physics doesnt allow the gap between the speaker and the corner to fill up with audio.. and the only audio that does get in there is the sloppy reflections.
to put it into perspective, air is a gas that moves kinda like water.
the only way to fill the room 'solid' is to place the speaker in a position that gives a fair chance to grip the water.
why is it even being brought up as important?
because the audio effects rely on the reflections of the walls to create the virtual speakers.
it is true, there are times when a speaker doesnt need a reflection to create a virtual speaker.. but this is only valid with lots of speaker cone movement.
here is a kindergarden example..
you throw out a sound that is positive phase, then throw out a negative phase of the same sound at twice the speed of the positive phase.
when those two pieces of air combine, they should cancel out.
what if the negative phase signal wasnt exactly opposite of the positive signal?
well that means the soundwave's amplitude will be almost cancelled out, but the audible energy will still be there at a lower perceived volume.
..what if you increase the gap between the two phases again?
the perceived volume will be louder again.
so how does a virtual speaker work?
the above 'dimming' of the audible signal takes place, then one of two things happens:
1. the same speaker throws out another signal after some time has passed with a collision course for the first signal.. and when those two signals meet, the sound is heard.
2. the other speaker throws out the second signal with a collision course for the first signal.
see.. if the speaker cone was going to throw out the signal and try to smack the first signal in the rear, then that signal would need to travel with more speaker cone movement to catch up to the first one.
but thanks to diffusion audio engineers know the soundwaves are causing ripples in the water, and they also know those ripples will spread out, and they also know if those ripples hit a wall.. then those ripples will spread out farther.
if you had an empty room that was square, and you removed the ceiling as well as the floor.. then placed a single speaker placed in a hole in the wall.. that speaker could play a tone and the ripples in the water would go on and on with the same pattern (including the bouncing ripples off the wall).
looking at that, a sound engineer can visualize the lines of the ripples as they move across the air and bump into eachother.
so for the virtual speaker to work, all the audio engineer has to do is decide what two lines bump into eachother for the virtual speaker to be at that location .. and then calculate how long the second signal must wait to get the two lines of ripple to line up with eachother.
there is a choice.
because crashing a soundwave into eachother with a head-on collision is the most violent, choosing a line of ripple that crashes head-on can sometimes produce the loudest effect.
sometimes it wont because the soundwave had to bounce _____ number of times before it was properly aligned head-on .. and by then the soundwave has lost too much energy compared to using a line of ripple that is more sideways (known as a T collision).
for a receipt of validity, go here and read:
virtual speakers dont trick the brain using phase and time variables, the sound waves literally collide in the air at the location heard.
the only way to 'trick' the brain is to place a microphone inside an ear of a virtual dummy head and record the impulse response from behind the ear.
the problem with this is, it only works when the shape of your ear is the same (or close to identical) as the dummy head because the reflections that bounce off the skin (as well as the soundwaves that are blocked) is exactly what was recorded with the impulse response.
there is a whole bunch of timing and phase information recorded in the impulse response because of the reflections that bounce off the skin and the soundwaves that are blocked, and it is that exact information that your brain has been listening to since when you first began listening.
you cant listen through another persons ears and be able to locate a sound behind you because the timing and phase information doesnt match what your brain is experienced with.
(if they are somewhat the same shape, you will know if it is in front or behind you.. but you wont have any idea about the degree of angle the sound is ... and that means you wont know if it is 54 degrees behind you or 80 degrees)
it can be done by taking the most basic averaged shape of the ear and recording the impulse responses.
you then get direction about to the side or behind you, but the result wont be accurate enough to scare the living light out of you (also known as 'made you look' ).
with that said..
getting those ripples to fill the room equally is very important.
placing the front speakers next to the television stand far away from the wall doesnt give those ripples a fair chance to exist.
it means if one speaker does the job and relys on a reflection, the sound arrives late.. and sometimes the sound can be heard more than once in the gap between the speaker and the corner of the room.
(it isnt loud, but it is just as bad as the room ringing .. and we all know the room ringing doesnt give the details and character of the audio a silent chance to be heard)
...it forces audio engineers to use the other front speaker to get the virtual speaker to work.
here is the problem..
many people put their couch right up against the wall, and that means the two ripples must make contact with eachother before the ripples hit the wall behind the couch and pour out into the room like a broken water pipe.
...and this is exactly why people always say it doesnt matter if the two front speakers are next to the television stand or in the corner, because they both create a line of 'possible' virtual speaker from one edge of the listening position to the other.
(and that is why they always tell you to leave a little bit of speaker cone facing the outer edge of the couch to increase the line width)
why did i say something about pulling them apart then?
because of a few reasons:
1. you limit your width of the virtual speaker location, because the two ripples arent very far apart when using one signal from one speaker and another signal from the other speaker.
2. not all sound engineers will choose to use the other speaker to reinforce the virtual speaker, and when they do.. you wont be there to catch much of a difference (if any at all).
you start to realize the second signal can come from the rear speakers, but there is why the distance delay is absolutely critical.
really think about it..
why snack on a stereo fade that is only as wide as your television stand when you could be hearing it from one wall to the other?
(this is especially true if the distance between your listening position and the speakers is small)
they already tell you this.. if you want to increase the soundstage width, simply seperate the speakers more.
you are going to thank me later when you realize not all of the ripples are counted from the second speaker, but the reflection off the wall is also used to help:
1. add amplitude to the sound
2. add detail & character, either because of signal to noise ratio .. or simply because the phase the sound engineer needs to shape the soundwave quickly and easily comes from the reflection off the wall.
there is always going to be two different types of virtual speaker sounds:
1. the typical fade from left to right or front to back, and the special 'something inbetween'
2. the sound of rain that seems to transform the entire room into a landscape you can almost smell the change of wetness in the air.
if your speakers arent in the corner, be certain your room wont will up with number 2.
(sure, some of you will get some of the affect.. but it will be with the added noise between the front speaker and the wall reducing your signal to noise ratio, as well as pouring out distorted ripples of soundwaves into the air causing a loss of detail heard by the ear)
when the pattern of ripples in the water change from that empty square room, you can expect the transferred results to be different.
rectangled rooms dont need to worry much because the major focus is 'cube' .. meaning four walls, a floor, and a ceiling.
those of you with your front speakers away from the corner are trying to 'delete' one of the four walls.
cubic doesnt work with 5 .. it works with 6 .
what do i mean when i say cubic?
referring back to the empty room without any floor or ceiling, watching those ripples in the water as they remain constant in time and frequency variances .. some type of mathematical function must capture the existance of those ripples since they are constantly the same and reliable.
..............well here is the issue:
TRIgonometry works with triangles, thus THREE variables.
but that room has four sources.
if you add the floor and the ceiling, that is six sources and a double of three.
but.. if you dont let the front speakers use the front wall as a reflection because there isnt any line-of-sight from the cone to the wall ... that brings the number of sources back down to five and trigonometry doesnt fit the bill once again.
why would i say anything about cubic then?
because cubic works in powers of four, and is the next step up from trigonometry.
how does four fit into six sources? .. easy, there are two remaining.. one for positive and one for negative (or one for +180 degrees of phase and one for -180 degrees of phase).
really.. it should make sense that those two free variables allows the surround affect to move through the air freely when added with trigonometry.
...how does that make sense you ask?
because if you have six and you are using seven.. that means there is always going to be an extra one that you can use as a layer onto the existing six.. and that is how the sound can be hidden as it moves to the physical location before it explodes in a collision like a firework shooting up into the sky and bursting into color & sparkles.
if you can see how to use seven, you might as well go on and move up to two iterations of cubic, because that brings the total number up to eight.. and that gives you one for the left and one for the right.
(or one for positive phase and one for negative phase)