So here's a head-scratcher posted in the Acustica Audiophiles group on Facebook, paraphrased:
If you have a reasonably dead room and then globally process your audio with an impulse response of a great diffused control room, what are the pros, cons, and differences you can expect?
I can suppose that you won't get the same effect with processing as you would in reality if you move your head. A real room will give a different response whereas you would only get the off-axis response of your speakers in the dead room. That doesn't seem to be very relevant.
Another difference is that you won't get the benefit of diffusion when your speakers are off.
But let's restrict this to pure mixing or mastering. How much different would this be?
Post by Michael Lawrence on Jul 3, 2018 3:42:59 GMT
Interesting question, for sure.
There's a good article here that Ethan sent me a while ago.
In theory - important phrase there - an anechoic impulse response, convolved with the impulse response of a reverberant space, is mathematically identical to the impulse response of the original source in the space. IR reverb effects have only come into practical use recently because of the immense amount of CPU power that is required to do the convolution - effectively you're multiplying every sample in your source audio file with every sample in the IR audio file. That's a lot of math, and so only recently has it made sense to try and do such a thing without bring your computer to its knees. But obviously the result, in terms of realism, is far beyond what you are likely to accomplish with the old delay tap feedback algorithmic reverb.
If I understand your post correctly, you're asking about having a dead space and substituting that with artificial reverb through the monitors? That's basically how live sound reinforcement works, but it won't sound the same as a reverberant space because all of the sound is still coming at you from the loudspeakers, whereas true reverb comes at you more or less equally from everywhere. That's less true in a small space like a room but still far different than it coming from two speakers only.
It might be enlightening to look at the electroacoustic reverb systems like Meyer Sound Constellation, which use a large number of speakers in the walls and ceiling to do exactly what you're talking about. I've heard such a system at the Sweetwater headquarters in Fort Wayne, Indiana, and the effect is pretty stunning.
To to recap, it's not the IR itself that's the issue, it's the directional characteristics of the source that I think would be the problem.
it's not the IR itself that's the issue, it's the directional characteristics of the source that I think would be the problem.
I agree. Though your "here" link above doesn't work, and I don't have direct experience with this. But I have a theory anyway.
First, no matter what you do to process the audio from two speakers in a small dead room, it can't envelope you with sound as in a large room. Related, some years back the people who run the Danbury Music Centre where I used to play in orchestras decided to look into improving the acoustics of their rehearsal space. It's a large former library, with many concave sections on the ceiling. So it's not only too live sounding, but the sound is focused in unusual (not good) ways. I usually played the cello, but sometimes I played percussion. So I'd be next to the other percussion people at one end of the large room, 20-30 feet from the woodwinds near the middle of the room. One time I noticed I couldn't hear the snare drum just a few feet away very well, but due to the concave ceiling areas focusing sound it sounded like the flute player was right next to me. Anyway, I digress:
I offered to donate a bunch of RealTraps panels, but they didn't want to change the look of the room, and there's an issue with getting the city's permission because the building is "historical" and they have a $1 per year rent deal they can't mess up. So they contacted Lexicon, who apparently do venue acoustics as well as studio reverb effects. The Lexicon guy came and said that for a large sum (about $50K as I recall) they'd make this large space mostly dead with absorber panels, then add a bunch of microphones and speakers all over to allow dialing in custom acoustics electronically. I thought the idea was brain dead, and I still do. At least for an orchestra rehearsal room. But this is probably what you'd have to do using "convolution reverb" to apply the sound of some large space onto your small home-size room.
Post by Michael Lawrence on Jul 4, 2018 20:49:23 GMT
Link fixed. Thanks, Ethan. That's pretty much the idea, and it's becoming more common in performance venues because building a hall to sound great for orchestra means you can't book much else in that room and most orchestras can't pay their own bills, so we are seeing a trend toward electroacoustic reverb systems. The Lexicon quote sounds suspiciously low. Usually you're in the 300k to 500k range for small-mid sized venues. Wenger makes a system too. The advanced ones can actually create different acoustic environments on stage and in the house.
Ok, thanks for the responses. That makes sense. I have no experience with diffusers but I can recognize my fan whirring behind me. So the takeaway seems that, if mixing in stereo with this effect, it'll just sound like you put your mix through an impulse response and nothing more.
Having just started using reverb more methodically, I'm excited to check out that SoS article on convolution. I remember reading somewhere that you can use any sound, like pink noise, as an impulse response. That article looks like it explores those ideas more deeply.
I'm not sure what DAW you prefer, but Logic Pro X has a binaural audio panner. I'm sure you could find the same thing as a third party plugin for other DAWs. [INFO] It works with headphones, because they bypass the HRTF (the reflections off your pinna and torso that help your brain localize) but allows you to manipulate the audio to sound like it's coming from anywhere, behind you, above you, etc. It's certainly worth playing with. Maybe get a couple of different mono reverbs set up and processes them all individually with binaural processing to put them at different locations around your head. True you have to wear headphones but if you're interested in learning about and experiencing the effect it's a start.
Also, look into the klang:fabrik system. It applies this principle to in-ear monitor mixes. It's shockingly effective, from what I hear. The cool thing is that you can download their app and demo the software even if you don't own the processor, so you can hear how it works.
Another thought is that you could put a few loudspeakers to the sides and back of you like the surround setups, and insert reverbs on their feeds. Adjust predelay to put yourself in a space (how long before the first reflection, basically setting how far away the wall is) and you can get a surround sensation going, at least. They also actually make 5.1 reverbs. Logic Pro has these as well.
Experiments are a great way to "test the waters" of a concept like this.