On Wed, Jul 23, 2014 at 07:52:52AM +0200, Gabriel Nordeborn wrote: It's not basic and not easy. A room doesn't have 'a' frequency response, it has a zillion FRs. You'll get a different one for each position and orientation of the speaker and for each position of the mic. And if the mic isn't an omni (yours isn't), also for each orientation of the mic. And each of these, unless doctored to look presentable, will look quite chaotic and completely different from all the others. In other words it's near impossible to interpret a raw FR of a room unless it has been processed to remove irrelevant detail and keep only the features that matter. And then you need to understand the nature of that processing and its consequences. And even then just a FR isn't very interesting. How a room sounds depends very much on how it behaves in the time domain. A raw impulse response will tell you more than raw frequency response. But the relevant information is a combination of time and frequency domain data. It's quite easy to 'flatten' a room FR in the mid in high frequency regions, a combination of damping and scattering (diffusing) will do it. But unless your acoustic treatment includes the low frequency end as well you could end up with a room that is very boomy and still has a lot of resonances (room modes) in the lower frequencies. And removing those is not easy and not cheap. So in the end it's better to not overdo the mid and high frequency treatment unless you have the means to treat the low end as well. This is why near-field monitoring is popular in budget limited conditions, by placing yourself closer to the speakers you reduce the influence of the room on what you hear - it eanbles your brain to ignore the room to some extent, provided it's not too small. If you want to correct your system after the room is finished, the DRC software <http://drc-fir.sourceforge.net/> is the way to go. Make sure to read the excellent documentation, all of it, so you have and idea of what you're doing. It will explain some of the hairy things I hinted at earlier. DRC will produce IR filters which you can use with jconvolver (or with any other convolution processor). The result will be much better than when using e.g. a graphic EQ, because DRC does things that a simple equaliser can't do. If you want to get a quick idea of the overall FR you can use Japa. Send pink noise (from Japa) to a speaker (one at a time), connect the mic to one of Japa's inputs, select 'Prop' response (using the control below the display) and 'Slow' or 'Noise' speed. This is the type of measusement that would be used to adjust a 1/3 octave graphic equaliser. Note that the target is normally not a flat response but one that drops off gently above 2 kHz. Caio, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow)

On Wednesday, July 23, 2014 07:52:52 Gabriel Nordeborn wrote: .... Some of the FLOSS tools are nearer than you might think, it's your ears! :-) Here is my thoughts on small control rooms/studios, and you can do a lot before starting to measure: First of all, no matter if the room is perfect or not: When you mix, do it at an amplitude where you can speak normally. That way, the room's impact is at a minimum and your ears will be very happy! Everything "sounds good" when you play loader. If it does not sound good when you play at a low level, then it's not finished yet. And don't bother to make the room perfect, it's better to have a sweet spot or two-three in the room where it's good, first of all where you sit and mix and possible a spot or two where you can record vocals and acoustic instruments. Measure tools and software are great, but you should also trust your ears. I think that is more important. I you from your listening position plays a sinus tone from a C1 note (that''s around 33Hz) and walk chromatically up to C4 ( 262Hz), then you will easily hear that some notes probably will sound stronger and some weaker (phased out). When you identify a trouble note, you can localize where the spot in wall or ceiling or whatever that is making problems. Thankfully, not all room resonances will kick in from you listening position, but let's say that a low E (the one at approx 82 Hz, ie the low guitar e-string) is stronger, then divide 172 with 82Hz and you will get approx. 2 meters as the answer. Is there something with 2 meter of length that can create problems? It can be between two walls or even more likely the distance from your ears to where a wall and a ceiling meets. That sounds amplitude may be weaker if you move your head a little bit. You should be able to quickly identify the 3-4 worst problem areas in your listening position. Apart from that, the measuring is of course very important, but most sound engineers (at least the ones I know) don't measure, they use their ears and have also learned their rooms and gear. Jostein