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PostPosted: Fri Sep 08, 2017 4:39 am 
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Joined: Thu Aug 21, 2008 10:17 am
Posts: 12034
Location: Santiago, Chile
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No matter how i edit the pictures they go upside down on here. Its a exif bug with phpbb.
There's over 22,000 members here, and as far as I know, pretty much all of them manage to get their pictures the right way up... :) Try saving in a different format... Sometimes re-saving a gif as a jpg or png will force the image editor to correctly identify the origin corner of the image, in the metadata.

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Nice guide Stuart can you explain the 60 degree tilt for me?
Omni mics are, in theory, "omnidiretional", and pick up all sounds perfectly equally from all direction. Theory is fine, but in practice that's not entirely true. Omni mics are slightly more sensitive in some directions, and slightly less in others. Specifically, they are slightly less sensitive directly behind, due to the "shadow" of the mic body itself. Some places tell you to aim the mic directly forward, in between the speakers, not angled either up or down, but that means that the rear end of the mic (least sensitive) is pointing towards the BACK of the room, and there's a lot of bad things happening at that back that you really do want to see as well as possible. Other places tell you that, for this very reason, you should point your mic directly upwards, at the ceiling, so it does not suffer from that problem, and picks up all sides equally. But that means the rear of the mic is facing the floor, and there are things happening between the ceiling and the floor that you want to know about. Yet others say that the best angle is 45°: neither directly forward nor directly upward, to get a "50/50" view: 50% forward/backward, and 50% up/down, and they are partly right, but have the wrong angle! a 45° angle does not give you 50/50: it gives you 70.7% / 29.3% For most mics, it's the cosine of the angle that gives you the best balance. At 45°, the cosine is 0.707. But at 60°, the cosine is 0.5, which gives you the 50/50 balance you are looking for. In addition, at 45° the rear end of the mic is probably facing towards the rear corner of the room, or close to it, and corners are interesting things, acoustically, not to be ignored. But at 60°, it is facing somewhere around 1/3 of the distance from the rear wall to the front wall, which, as it turns out, is about the smoothest spot in the room for modal stuff anyway (remember the 38% "rule"? it holds true for the rear wall as well...) So with the mic pointing 60° up, the rear end is pointing at the spot in the room that is the least interesting, acoustically, and doesn't really matter too much...

In other words, by angling your mic upwards at about 60°, you are getting the best-balanced acoustic picture of the room, not enhancing too much the direct sound from the speakers, and not ignoring too much the rear of the room, or the corners, and also not enhancing too much the ceiling reflections. It's not perfect, but it's about the best you can hope for.

If you want to prove this to yourself, do some tests yourself: set up your mic carefully aimed at 0°, dead forwards, and stretch strings across the room in all three directions, crossing over exactly at the tip of the mic, and run a REW test like that. Then do a a series of additional tests, adjusting the mic stand each time so that the mic is angled upwards in increments of 10° while ensuring that the tip of the mic remains in exactly the same place, at the point where the strings cross over. You might be surprised at just how much difference there is in the results as you change the angle, especially considering that an acoustic measurement mic is supposed to be omni! The difference is not enormous, but large enough to be interesting, and noticeable.

Of course, for all of these tests, you must be outside of the room when the test actually runs.

- Stuart -

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PostPosted: Tue Dec 05, 2017 7:44 pm 
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I usually purchase all of the roof insulation materials I need from [SPAM LINK REMOVED BY MODERATOR. ANONYMOUS SPAMMER WARNED] Their prices are always competitive and their staff are a great help in store.


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PostPosted: Tue Dec 05, 2017 8:03 pm 
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Location: Milton Keynes, UK
I have finished my build now and guess what company is opening in the next month or so. Haha

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