franman wrote on Sun, 08 February 2009 14:30 |
We use Membrane Traps, Helmholtz Resonators and other Broadband LF trapping to INCREASE the amount of percieved bass in a (small) room like a control room. In other words, the more we trap, the better and tighter and more detailed the Bass sounds. It is a popular misconception in control room treatment, that bass traps will "remove" bass from the room...
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When trapping or using resonators, you
are taking (LF) energy 'out' of the room, into heat. And because you do so, you even out the freq response of the room, by reducing and sometimes basically stopping any interactions between direct field energy and reflected/re-emitted energy. I don't think it is wrong to say that one takes bass out of the room - but I agree it should not be mistaken for another concept, that bass is not existing anymore in the room.
franman wrote on Sun, 08 February 2009 14:30 |
BUT, this seems to be what both are you are implying unless I'm not understanding correctly>>> that too many loose panels acting as membranes will take bass response away from the room.... Am I getting this right?? sorry for my confusion.... Maybe it's totally different in large performance spaces, but I know how larger recording rooms behave and we still strive to add sufficient LF trapping in these rooms to ensure the bass is tight and the decay is comparable to the rest of the spectrum... as you know it's easy to absorb too much High and Mid frequency and end up with a boomy sounding room.
Thoughts>????
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What can happen in such a room, is that the decorative loose panels (which for most I suspect have the same overall size) are acting as resonators with a certain bandwidth.
Also, in these types of room, for the vast majority of the public, the ratio of
(direct energy) / (reverberated energy) will be in clear favor of the reverberated field, which therefore implies the most energy perceived by the ear is from the reverberated field.
If those panels are such that they resonate and kill, say, the 100Hz / 150Hz band (because of differences of incidence), for those freq you are only left with direct energy, and none in the reverberated field. Which means that overall, this will be perceived by the public as a lack of bass, because it creates an imbalance in the reverberated field - which accounts for most of the perceived energy. Decay very is messed up freq wise.
Chances are these re-emit in the LMF band too, therefore increasing perceived energy with regards to bass, increasing the imbalance. (Those modern rooms I have visited have little to no MF treatment as well. Treating HF is no use, air does that job pretty well.)
EDIT: having a very live, but very balanced room reverb is important for those halls. They can't be deadened - or they sound dull and life less. This is an important difference with studios.