Old 04-11-2019, 12:16 AM   #1
Cranky Emu
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Default Impulse Response Creation

I've been slowly accumulating Impulse Responses (Reverb) and it occurred to me that on the farm we have a lot of highly reflective sheds. Most are tin structure, there is also the concrete milking yards. In addition there are a lot of local halls of varying size and one Blue-stone hall that I could get access to easily.

I've done a bit of looking around the net on how to create reverb impulse responses and am really no further ahead than when I started looking. Some suggest using some form of clapboard, others a starters gun (not sure if you can just buy and use one willy-nilly in Australia), or using balloons and popping them. I have a laptop with Reaper on it, and the Focusrite 2i2 interface, as for mics I have the Focusrite CM25 (small) condenser mic. I am not keen on dragging my monitor(s) into these sheds, as they are full of dust and assorted farm rubbish and gunk. Would I be able to successfully record reverberations with say 2x CM25 mics, the interface and Reaper? I would like to record them in stereo if possible, then if the end-user only wanted mono, they could deal with that on their end.

I don't have a huge collection of mics, as I do not record, but am happy to purchase another CM25 (if possible), or a pair of mics suitable for the job that isn't going to send me broke. Only on a disability pension, so can't afford to be forking out for high-end mic's like U87's or something. I would like to have a go at recording different spaces and uploading the results to the Reaper Stash for all to use.
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Old 04-11-2019, 02:09 AM   #2
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I've had success recoding my own impulses with a handheld recorder (Zoom H4n) and packing balloons/bags/pillows.



Just stomp on it for the impulse, or pop it in your hands for different reflections.

I've also found that some editing and EQ to the impulse can get you a nicer result when you come to convolve it.

You should be able to puck up a Zoom or Tascam stereo handheld recorder second hand pretty cheap. Lots more convenient than a laptop, interface and mic's.
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Old 04-11-2019, 02:14 AM   #3
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Thanks for the tip.
Excuse my dumbness on this, but what do you mean by convolve. Is there specific software required for this. I am guessing it is not just a matter of recording the reflections and some editing/eg?
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Old 04-11-2019, 02:15 AM   #4
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Some suggest using some form of clapboard, others a starters gun (not sure if you can just buy and use one willy-nilly in Australia), or using balloons and popping them. I have a laptop with Reaper on it, and the Focusrite 2i2 interface, as for mics I have the Focusrite CM25 (small) condenser mic. I am not keen on dragging my monitor(s) into these sheds,

heh-hey- well you know m8,this would be a perfect time for someone to kindly demonstrate the true power of reaverb! reaper can do all this itb.
it will create the testing tone sweep for you to playback+record..=deconvolution process.
to my knowledge there is no video showing this technique in action-you can do it maaan!!
you have the powers!! -ok,but you would actually need to take some kind of speaker--to the environment!! to playback the testtone.
+oh make sure all rates match 100% !
if reaperblog or kenny g has a video on this-be nicer for others to know_how...right?
cheerz.
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Old 04-11-2019, 02:28 AM   #5
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Thanks for the tip.
Excuse my dumbness on this, but what do you mean by convolve. Is there specific software required for this. I am guessing it is not just a matter of recording the reflections and some editing/eg?
Convolution is the name of the process when the impulse response file is used to affect whatever source you feed into it.
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Old 04-11-2019, 02:29 AM   #6
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heh-hey- well you know m8,this would be a perfect time for someone to kindly demonstrate the true power of reaverb! reaper can do all this itb.
it will create the testing tone sweep for you to playback+record..=deconvolution process.
to my knowledge there is no video showing this technique in action-you can do it maaan!!
you have the powers!! -ok,but you would actually need to take some kind of speaker--to the environment!! to playback the testtone.
+oh make sure all rates match 100% !
if reaperblog or kenny g has a video on this-be nicer for others to know_how...right?
cheerz.
I've had better results with clapping and balloon popping than sine sweeps. Probably because I've never had access to a speaker that had reference-grade frequency response for making IR's.
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Old 04-11-2019, 02:33 AM   #7
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I've had better results with clapping and balloon popping than sine sweeps. Probably because I've never had access to a speaker that had reference-grade frequency response for making IR's.

yes well--good points--but is a balloon or clap actually giving a full response anyways? not actually sure tbh..
the testtone would need a decent playback speaker for sure--but most household speakers are full range..or close to---i guess the creation part is also amp dependant...less amp=less responses--more amp-- louder recordings..?
i also guess with greater ampage-there comes the greater chances of room resonances to consider... heh
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Old 04-11-2019, 02:40 AM   #8
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Some info about using ReaVerb's sine sweep to create IR's here: https://www.soundonsound.com/techniques/reaverb-part-2
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Old 04-11-2019, 02:47 AM   #9
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Here's a video:

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Old 04-11-2019, 02:50 AM   #10
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I don't want to be using a speaker and/or amp. That (from what I've read) is the best way of doing it. Might get adventurous down the track, for now I just want to record some reflections for use with ReaVerb and make them available for everyone else to use as well.

Convolution: Okay so when you use an impulse in like ReaVerb, got it. Thanks.

Thanks for the article link. I think I will start basic just recording balloon pops etc, maybe even bash a hammer against something
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Old 04-11-2019, 02:51 AM   #11
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Here's a video:
Watching...
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Old 04-11-2019, 02:57 AM   #12
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maybe even bash a hammer against something

lol! please do not start getting creative with this!! it goes against all rules!! and could be highly contagious!! heh... why not? ..a gong..a bong..a gentle song--they all can be used as the dirac pulse..
the thing is--reaper has the ability+ as a user,so do you,to create your own stuff.kool huh?
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Old 04-11-2019, 03:04 AM   #13
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lol! please do not start getting creative with this!! it goes against all rules!!
Rules huh
Well since you have said not to, you can be pretty well assured I will

'Curiosity kills the cat' as they say, and I have this thing where I need to know how something (that I'm interested in) works or it drives me mental till I know. Would just be interesting to experiment with using different things to generate the reverb.

One thing that I might have a big problem with is external noise. Being on a farm it isn't exactly quite. The old blue stone school would be great to do I think, it is pretty big and very high peaked ceilings.
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Old 04-11-2019, 03:05 AM   #14
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Here's a video:
Thanks mate, great video. So just to get this right, basically record it and then edit out the whacking sound (as in where he hits the floor) and what is left is your impulse?
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Old 04-11-2019, 03:07 AM   #15
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One thing that I might have a big problem with is external noise. Being on a farm it isn't exactly quite. The old blue stone school would be great to do I think, it is pretty big and very high peaked ceilings.
This is where editing comes in. You can help the reverb tail with a fade, you can EQ out frequencies you don't like so much, you can use ReaFIR to reduce noise...
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Old 04-11-2019, 03:21 AM   #16
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This is where editing comes in. You can help the reverb tail with a fade, you can EQ out frequencies you don't like so much, you can use ReaFIR to reduce noise...
Thanks for the help. Over the next few weeks I will start working on some and see how it goes.
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Old 04-11-2019, 03:28 AM   #17
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Thanks for the help. Over the next few weeks I will start working on some and see how it goes.
Good luck!

Like Bri says, it's good to experiment too. Try clanging a piece of sheet metal and you can make your own super-cheap plate reverb IR!
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Old 04-11-2019, 03:43 AM   #18
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Try clanging a piece of sheet metal and you can make your own super-cheap plate reverb IR!

lolz^ hmm- i had an experience working a short time in construction--we was lifting a seriously heavy metal plating tobe attached to a wall as a permanent bracing--some crazy whacko decided to smash a hammer against the solid steel--as all our ears were close to the fixing... think i still have the reverberations from that sonic boom>> to this day! < would'nt recommend that! to anybody.. tbh
have fun,but as always,use precautions in ear defenses+ wear a hardened tinfoil hat,just to be sure
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Old 04-11-2019, 05:17 AM   #19
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Thanks so much for this thread; learning about this has been on my to-do list for a while.

I do all my recording in live spaces (no studios) and normally it's just acoustic instruments but I recently got a MIDI keyboard and will be adding accompaniment with that afterward. I wanted to have a way to match the room reverb in the MIDI instrument so it sounds like it was in the same room. Recording an IR file for the room seemed like a good solution, but initial research kept pointing me to Altiverb (e.g., https://www.creativefieldrecording.c...lse-responses/), which is expensive. Nice to know I already have a solution in Reaper!
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Old 04-11-2019, 06:27 AM   #20
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Your biggest enemy is background noise.

If you're in a dead quiet place, a sweep would give more resolution. In practice, you can't use it. No speaker has enough output for large spaces and it's frequency response will be far from flat.

So any impulse noise will do. Balloons in general give less low end reflections. A starter gun is better, if allowed, because it's a hell of a lot louder. The best is a spark from a spark plug, but that's not loud enough. What you need is a sharp peak with as much SPL as possible. That's hard, so we resort to balloons...

At least, with a peak, you can wait for a quiet moment. I've had too many sweeps ruined by traffic, or even sheep.
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Old 04-11-2019, 12:27 PM   #21
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Your biggest enemy is background noise.
Would you recommend dynamic mics over condenser's, considering condenser's will pick up a lot more ambient sound/noise?

The halls are going to be the easiest to do, the sheds on the other hand may be a work of patience. I don't want to be buying to much additional gear for this, happy to buy some decent mics as they can always be used for other things. Already have stands, so that is not a problem.
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Old 04-11-2019, 12:49 PM   #22
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Would you recommend dynamic mics over condenser's, considering condenser's will pick up a lot more ambient sound/noise?
Based on what I've read, you'd be best off with an omni condenser mic; a good but very affordable one is Line Audio's OM-1. But this advice may apply more to the "sweep file" method than the "clap" or "pop" slate/clapperboard method.
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Old 04-11-2019, 12:55 PM   #23
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Based on what I've read, you'd be best off with an omni condenser mic; a good but very affordable one is Line Audio's OM-1. But this advice may apply more to the "sweep file" method than the "clap" or "pop" slate/clapperboard method.
It's just what is most often used for room mic's, because you pick up the reflections from all around the mic.
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Old 04-11-2019, 02:09 PM   #24
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Would you recommend dynamic mics over condenser's, considering condenser's will pick up a lot more ambient sound/noise?

recommend the sos article-especially the bonus sections..
was aware of the previous posted video,but still to date,no1 has shown the testone method on video--this would be kool for reaper users who have no idea of what reaverb can do..
ahem..enter....from da home of hiphop!!.... > kenny g plz!
am surprised this has not been fully covered on vid yet... *rollz eyez*
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Old 04-11-2019, 04:21 PM   #25
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Would you recommend dynamic mics over condenser's, considering condenser's will pick up a lot more ambient sound/noise?

The halls are going to be the easiest to do, the sheds on the other hand may be a work of patience. I don't want to be buying to much additional gear for this, happy to buy some decent mics as they can always be used for other things. Already have stands, so that is not a problem.

Don't think gear. Think time.

Make a few. Process. Use. Listen.

Rinse and repeat.
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Old 04-11-2019, 05:40 PM   #26
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...considering condenser's will pick up a lot more ambient sound/noise?
Common misconception. A condenser is generally more sensitive than a dynamic. That means it picks up more of everything - both the wanted "signal" and the unwanted "noise" in the room. If all other things are equal, the proportion of S to ambient N will not be different. But it actually will usually have a lower S/N ratio in terms of "electronic noise" - self-noise and noise picked up between the microphone and the ADC.

It's my understanding that the sine sweep method can produce better S/N if the noise is more or less steady state because the deconvolution process tends to average the noise out. Deconvolution isn't necessary with an impulse source, and therefore you just don't get that benefit.

The sound you get out of the IR is going to be the frequency response of the original source track (including the room it was in and mic you used) filtered by the response of the impulse or sweep source (the speaker you ran the sweep through, or the specifics of whatever you used as an impulse) AND that of the room the IR captured AND the mic used to capture it. Any one of those things that is not completely flat is going to color the results to some extent. It's best to consider the effect more like "reamping" into the room, rather than actually putting the original source in the new room.

Most room effects are in fact perfectly linear as far as amplitude changes. That is, it resonates and reflects the same no matter how loud the source is. That's a good thing, too, since an IR can't actually reproduce nonlinear effects like compression, distortion, or if louder sounds caused a disproportionate amount of extra reflections.

It's important to remember that if you want a true stereo IR - where you can run a stereo source through and maintain relative panning information - you not only need two mics, but you need to shoot the IR twice with the source in different places.

Edit to add - Any strong tonality or extended ringing in the impulse source is going to come through the IR also. Hitting something like a box of a metal tube or something might give you something interesting, but it will be rather unnatural sounding and usually not what we want. If been known to use drum or even cymbal samples as IRs in the past, and while it can be pretty cool, it definitely doesn't sound like I just put my source in the room.

Last edited by ashcat_lt; 04-11-2019 at 05:48 PM.
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Old 04-11-2019, 10:21 PM   #27
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Common misconception. A condenser is generally more sensitive than a dynamic.
So what is your recommendation? Dynamic or Condenser.
I am kinda leaning towards condenser's as I plan on using them for recording sound (ambient) effects as well.

The condenser's I was looking were the Rode M5 MP's, they tick the financial box
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Old 04-12-2019, 01:44 AM   #28
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So what is your recommendation? Dynamic or Condenser.
I am kinda leaning towards condenser's as I plan on using them for recording sound (ambient) effects as well.

The condenser's I was looking were the Rode M5 MP's, they tick the financial box
The M5's will be fine.

If you can stump up a bit of extra cash, the NT-5 will allow you to get the NT45-O omnidirectional capsule at some point in the future, giving you the option of cardioid or omni.

Another tip: don't always point you mic's at the impulse source. Try pointing them up at corners of the ceiling or anywhere else that looks like it might give interesting reflections.
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Old 04-12-2019, 02:16 AM   #29
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The M5's will be fine.

If you can stump up a bit of extra cash, the NT-5 will allow you to get the NT45-O omnidirectional capsule at some point in the future, giving you the option of cardioid or omni.

Another tip: don't always point you mic's at the impulse source. Try pointing them up at corners of the ceiling or anywhere else that looks like it might give interesting reflections.
I just looked at the NT5, it is probably out of the budget range right now. Keep it in mind for later on down the track though for sure.

As for positioning, all noted. I will start with the big shed down at the yards, which may mean some early morning or very late night wanders. Be pretty hopeless during the day, with the traffic on the road, animals screeching, dogs barking their heads off etc etc.
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Old 04-12-2019, 12:46 PM   #30
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I mean, you assess your goals, decide what you're trying to achieve, and pick a mic that you think will get it for you. Most people don't use dynamics for room mics, but there's no reason you couldn't as long as you can accept the extra noise.
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Old 04-13-2019, 02:46 AM   #31
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I mean, you assess your goals, decide what you're trying to achieve
Thanks to all the the comments and help.
Today I ordered a Rode M5 condenser matched pair, along with some additional mic cables. Hopefully have something useful to upload to the stash within a few weeks.

I also record a lot of ambient sound stuff, which I used to sell at markets - for some reason people want to buy CD's of waves crashing. Unfortunately the mic's I had for doing that got drowned on an outing.

Not sure if anyone here would be interested in ambient sounds, or sound effects - if there are I am more than happy to upload them to stash as well if there is a section for that, or put them somewhere for people to download.
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