I am in the process of building a studio and treating my room.. I watched that episode of Pensado's Place: #21 - The secrets behind tuning your room and I made notes for my refrence while doing the build..
Im putting the notes on here so if you dont want to watch the hour long vid you can read my condenced version.. sorry about spelling, it was very late when i took notes
Pensado's Place: #21 - The secrets behind tuning your room!
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http://www.youtube.com/watch?v=AUTe7F0Q ... r_embedded#!
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70% of what you can do for yourself is finding that one magic place in the room where the speakers and the listner want to be, there will be ONE PLACE in the room that will sound best
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get the room sounding as good as possible without and use EQ as a last resort.
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70% listner & speaker placment
-minimise speaker/boundary interaction (200hz and below)
25% accoustical treatment
-solve first order reflections (absorption)
-adjust room size perception (diffusion)
-solve bass issues (traps)
5% EQ
-icing on the cake/ fine tuning
-apply standards (dolby X-curve)
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EQ's in room treatment
in certian cases EQs can address low frequency problems that otherwise would be too costly to do or if you dont have enough space to address low frequency problems, EQs can then take more of that percentage and can sometimes even save your butt!
Bob Hodas generally does "cut only" EQ on the room - this is normally the first point of call. boosting is dangerous for a few reasons
1) every time you boost you take headroom out of your system, so by adding 6db of boost you are basiclly taking half the headroom of the frequency out, so you can drive your system into overload more easily.
2) if you have a cancelation creating a hole the more energy you boost into it the increase in the "out of phaze" ness caused by the canceling if a hole is more than 6db in a room you generally want t address it accousticly rather than by EQ
low frequencys are the main problem as they are the hardest to control, high frequencys are really easy to control.
speakers are omni directional below 200hz
the best way to even out the frequency responce is to MOVE THE SPEAKERS & THE LISTNING POSITION AROUND until the reflections coming off the walls & ceiling "comb" themselves into a "fairly" flat responce ( also can use room EQ wizard?)
moving the speakers 4-6 inches can show you a significant diffrence
try to find the best placment for your speakers that give you the smoothest bass responce, then it becomes easier to find the first order reflections.
when moving speakers around focus & listen mainly on the low frequencys, as high frequencys are prettys easy to controll
common accoustic foam has little mass and is only good for first reflections/ high frequency absorption, not good for absorbing low frequencys because low frequency wavelengths are bigger. A 100hz wavelength is 11ft wide (132 inch), so in order to absorb 100hz you wan about 2.5ft (30 inch) of trapping. accoustic foam is only good for about 3000-4000hz and up.
a good way to get better results from 4" bass traps/ foam is to leave a gap behind it by giving it an airspace and move it out a couple of feet (2-4"), all of a sudden the wave has to go through the foam/ panel, hit the wall, come back through the air, hit the foam again, and come back out.. doing this will help controll the low frequencys better than just having them flat against the wall
note that you can find a spot in the room where the bass sounds great but the stereo imaging is poor, this is due to not being in an "equilateral relationship" with the speaker.
The equilateral Triangle.
The diffrence between the left & right speakers should be fairly close to the distance from one of the speakers to the listner. if you imagine a equilateral trianle of 3x 60 degree angles you should be positioned "inside" the triangle just a little bit, because if you are seated directly at the apex then you will fade in and out of the center image every time you move your head slightly. Speakers should be "focsed" or "meeting" just behind your head. generally if a room is particularly small or has very bd accoustics, the "sweet spot" could be no bigger than the size of a watermellon even after treatment
symmetry is the most important thing ever in setting up a room becuase symmetry (e.g speakers the same distance from the front & side wall, not stacking all gear up in one side of the room, etc) will greatly effect how the bass behaves in the room. If you want good stereo imaging you need the speakers to peform the same with the same frequency response..
symmetry is the main starting point
Advantages of symmetry.
-applies to walls, equipment & speakers
-accoustical treatment works for both speakers
-beter side to side imaging
-better center image
if your 2 speakers have a diffrent frequency responce you will have phase cancelations in the center (due to sound bouncing off walls)
the problem trying to controll low frequencys is the addition and cancelation of certian low frequencys based on first reflections from the walls - 200hz and below is "omni-directional" by having speakers built into the wall you eliminate one boundary = less reflections
it can sometimes be worth putting speakers near a wall/ in corners in order to use the build up of bass there to get a better responce. although this should be approached with caution as it may lead to a 3db to 6db increase in low frequencys that may give a false picture! experment with placment to find the best place.
whatever works, works.. no rules of thumb, if it sounds good, it is good.
measure with things like room wizard to test the room.
even something like having your desk against a window can be good, the sound going straight out the window may reduce interfearance, it may not. ultimatly - where does the bass give you the best responce? listen, and test by taking mesurements!
rule of thumb - you want your speakers 2ft (24") away from any boundary (front & side walls), but again, this does not work for every room
bass traps in corners are a good starting point, but beware because you may be sucking out frequencys that you DONT want to suck out, everything is interactive.
if you dont have room wizard or a similar tool, get a freind to move round the room with a panel/trap while you sit in your listening postion until you find the best spot.. when treating a room you cant just put panels anywhere and expect them to work.
for bobs home made bass traps he uses 2 to 4 inch 703 (or rockwool equivalnt) glued to a sandwich of sound board (crumbly brown stuff, used to be used in construction - johns manville sound board?? kind of like the stuff in drop ceilings, but not as dence.
the way these traps work is they turn sound enegry into heat by movment, this how they absorb the fequency, they move a little bit and it transfers the energy. the waves pass through soundboard and makes it move.
Bass Traps.
-more universal fix throughout room
-larger sweet spot
-trap styles
tuned membranes/ broadband & low frequency
large broadband
electronic tunable trap
-always measure
not all corners are bad
placement critical
newby room treatment - speaker placment
use RPG room optimiser to get a good idea of speaker placement & first order reflection points - £100(80% success rate)
http://www.rpginc.com - saves you a LOT of time
51:09 - the "mirror" trick - how to find first high frequency reflections
