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Abe The Babe View Drop Down
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    Posted: 24 November 2012 at 5:56pm
I made a comment two days ago about designing a mid side speaker array. 
I have put a lot more thought into this since the comment and I'm not sure how it can actually make sounds appear left or right as the time of arrival differences would be next to non existant (which is part of the idea) and I don't understand how you recieve the guitar for example at a higher level at one ear than the other. It does make sense though that by altering the amount of a sound in the side speakers the image can be made wider, or further away, maybe general area left or right based on the reflections from the left side of the room vs right side, but if that were the case the more you tried to make an instrument appear left or right the further away the sound would appear.


Edited by Abe The Babe - 26 March 2015 at 12:52pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 24 November 2012 at 7:27pm
have you got a link to the thread u mentioned? im not familiar with this mid side technique. do you refer to a left center right deployment?

if i understand you correctly about how the brain interprits the direction sound is comming from, i believe it is similar to triangulation (like what the gprs networks do to locate your position) it is quite amazing realy, but perhaps not so much as the eyes ability to judge distance through a similar method, given the light is sooo much faster than sound and the differences in arival time are even more minute.

i was sitting the other day listening to dogs barking in the distance and marveling that my ears and brain were able to tringulate the direction over a distance of perhaps 1km, even though my ears are only 20co or so apart.

sorry if i have missed the point there

cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 24 November 2012 at 8:44pm
http://forum.speakerplans.com/constant-dispersion-2khz-15khz-point-source_topic72566_page4.html 

Mid Side is normally a stereo mic'ing technique, using a directional mic and a mic with a fig. 8 polar pattern. The directional mic is pointed at the source, this provides the direct sound and the centre of the stereo image. The fig 8. is placed perpendicular to the directional mic with their diaghrams coincident, this is referred to as the side mic. The signals from the 2 mic's are run into a mixer (or daw). The mid mic is unpanned sending equal polarity and level to both speakers. The side mic is sent to two individual channels, they are hard panned left and right and one of the channels is polarity reversed the faders are grouped. When the signals are summed acoustically after leaving a conventional left right speaker system the stereo image is created by the interaction between the three signals. 


Edited by Abe The Babe - 26 March 2015 at 12:53pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 24 November 2012 at 10:07pm
http://www.artofrecordproduction.com/index2.php?option=com_content&do_pdf=1&id=224 I just found this. Explains a bit, still an interesting idea.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2012 at 12:18am
right. thanks for clarifying. i cant imagine that method of miking being much more than a source of feedback on a live stage, but i must say ive never tried. as a matter of fact this is the first time i hear of the technique.

ive not had time to check out that link above, but ill have i peek later.

i must say im a little scheptical of it being used in a speaker, as i can only imagine it working at short wavelengths, which would be directional and not too audiable from the front, but hay, it would be great if someone more learned could come along and shead some light on the subject.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2012 at 12:57am
The mic'ing technique is more for recording than anything else tbh. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 27 November 2012 at 2:16pm
No panning can be done.

Edited by Abe The Babe - 26 March 2015 at 12:55pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 27 November 2012 at 2:55pm
I would think it would work more like a surround setup minus the rear speakers.  There could be a center stack, and two wide stereo stacks.  The center stack would play all the mid program, and the side stacks would obviously play all the side programming.  If you put all of the stack together, you would lose the wide stereo separation and I would think it would sound similar to just running a mono stack.  Personally, I would set mid section up to run full frequency and the sides just with mids and highs.

I use mid side processing in logic all the time, and have given some thought to setting my PA up, but I don't have a good gigging laptop.  I have hardware which I could use to do it too, but have never actually done it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 28 November 2012 at 3:23pm
This guy yeah?

Be interesting to do it on a large scale. One would simply feed three directional mid-highs, placed at 90 degrees to each other, with the outputs of a standard MS encoding done on a mixing desk with the aid of a couple of y-splitters. So forward facing speaker receives L+R (mono sum), left and right facing speakers receive L-R (signals summed out of phase), either left or right facing speaker is run polarity inverted.
Now, if a sound pans from L to R on the original recording, it should also appear to pan L to R in the soundfield from this mid-side stack.

Directivity would be interesting, on the face of it you would expect a nice 180 degree dispersion but the side speakers aren't playing all the music so there would be some loss of information as you move outside the coverage of the forward-facing speaker.

No-one I know actually has three big loud narrow dispersion mid-highs all of the same model, so it'll be a while before I get to try this....


Edited by studio45 - 28 November 2012 at 3:24pm
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 28 November 2012 at 3:59pm
In true mid side processing, the mid program should just be playing what is identical on left and right, and the side programs are playing only the material which is not identical on the left and right.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote boab Quote  Post ReplyReply Direct Link To This Post Posted: 28 November 2012 at 8:01pm
I have tried this in my studio/ test room.
Its has more stable spacial effect across the listening field but is less convincing than true stereo for the main area.
I found it to work well will with Guitar as you can use two cabs as long as the back cab is at 90deg to the front cab and is open back. I set up and tweeked delays with good effect.

Best Boab
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Monkeys Quote  Post ReplyReply Direct Link To This Post Posted: 28 November 2012 at 11:27pm
Originally posted by thepersonunknown thepersonunknown wrote:



if i understand you correctly about how the brain interprits the direction sound is comming from, i believe it is similar to triangulation (like what the gprs networks do to locate your position) it is quite amazing realy, but perhaps not so much as the eyes ability to judge distance through a similar method, given the light is sooo much faster than sound and the differences in arival time are even more minute.




Just thought I'd let you know that the way the brain interprets distance from information from the eyes is very different to the way it does so from the ears.

With the eyes the brain mainly uses the differing information from the left and right eyes to determine depth, called 'spatial disparity'. This is how 3D glasses give the perception of depth, by delivering two slightly different images to each eye.

With the ears, since the speed of sound is relatively slow, the different times at which a sound reaches each ear can be used, as you said, to perform a sort of 'triangulation' of the origin of the sound, this is also coupled with the differing loudness in each ear to give better accuracy.

The really impressive part, for me at least, comes in the brains ability to interprets sounds in 3 dimensions, that is, in front, behind, above, or below. As merely using the difference in timing and loudness in each ear would only really give you the location relative to left or right. If that were the case, then an identical sound coming from 2 o'clock, would be perceived the same as if it came from 4 o'clock. But it isn't, we are able to perceive when something is behind us, or above or below us, even with our eyes closed.

This is something which is actually still relatively poorly understood from a neuroscience perspective. It is believed that it involves a very subtle interaction between the sounds timing information and the shape of the ears, and the way that the sound is 'funneled' into the ears. So that a sound coming from above, will be funneled in along the base of the ear canal, and then stimulate a specific part of the cochlea more strongly than if it were coming from the bottom, and vice-versa. Giving the perception of 3 dimensions!

Hopefully someone finds that as interesting as I did writing it! I did a degree in Neuroscience and hardly ever get to use the information that I've learned, so thought I'd jump at the opportunity
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