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Help with Convolution Reverbs Reverb & Delay Plugins
Old 8th September 2011
  #1
Gear Head
 
ipizzo's Avatar
 

Help with Convolution Reverbs

I am doing my audio engineers studies thesis about convolution reverb operation... how do they work.

I need some help regarding Digital Signal Processing (DSP) and the Convolution principle... Any electric engineer available?

I would reaaaally appreciate if someone give me a hand here!



Thank you very much in advanced!!!

Italo.
Old 8th September 2011
  #2
Moderator
 
matt thomas's Avatar
When someone is doing an assignment I'm always not sure how much to tell them, as they are meant to be researching it themselves.

Think about where you might find info on this and look there.

Like google. Type in "convolution reverb" and the first result is the wikipedia entry (another good place to look) which describes it.

The manufacturer of the most popular convolution reverb has a video on their website explaining it simple terms. That would have been another good place to look..





matt
Old 8th September 2011
  #3
Gear Maniac
 
Richardwynne's Avatar
 

Quote:
Originally Posted by matt thomas View Post
When someone is doing an assignment I'm always not sure how much to tell them, as they are meant to be researching it themselves.

Think about where you might find info on this and look there.

Like google. Type in "convolution reverb" and the first result is the wikipedia entry (another good place to look) which describes it.

The manufacturer of the most popular convolution reverb has a video on their website explaining it simple terms. That would have been another good place to look..





matt
+1 for not being a lazy piece of ****
Old 9th September 2011
  #4
Gear Head
 
ipizzo's Avatar
 

I have done lots of research and I'm really working on my project, however I wanted to have some gearslutz opinion as an extra source and extra point of view... Not to have just the wikipedia one.

Thanks anyway,

i!
Old 9th September 2011
  #5
Registered User
There's always the Search button if you want opinions from Gearslutz.

or just read a few pages ... the subject comes up frequently. Maybe it will be shortened to "IR" - since a convolution reverb is all about the quality of the Impulse Response audio files.

Have you used one yet? It would cost you nothing. The only way to really learn is to find out for yourself.
Old 9th September 2011
  #6
Gear Maniac
 

HI,
i would also like the highest qualified person (or committee!) to answer my vague questions!
Old 9th September 2011
  #7
Gear Head
 
ipizzo's Avatar
 

Hey guys, I'm not a complete newbie. Of course I've used convolution reverbs, I have Altiverb and Waves IR1 and a lot of of IR... I know what an IR is and have mixed a lot with CR.....
I just need help with DSP and how do they storage the samples taken on real environments and convolve them with the dry signal you are recording...
Is it that hard? Can anyone refere me and not send me to google?
I know you guys are telling me this for me to learn and not being a slacker but you can be completely sure I am not.

Thanks, still waiting for some help if possible.
Old 9th September 2011
  #8
Gear Head
 
ipizzo's Avatar
 

Matt, thank you for the video anyway, it helped a lot!
Old 9th September 2011
  #9
Lives for gear
 
mmcfarlane's Avatar
 

For audio reverbs applications you have an input signal (an audio track, e.g. a vocal track), and the convolution operator. For convolution reverbs the convolution operator is typically created using a microphone recording of the reverberation of room (if it is a room reverb). The reverb sound can be created by exciting the room with short burst (impulse signal) of acoustic energy, for example popping a balloon (there are other techniques, particularly if you want to emulate hardware where there is no room to excite) and the reverb of the room is recorded.

Now you just run the math, convolving the input signal with the operator. Wikipedia surely has the formula.

One easy way to visualize convolution (without doing the math) is as a replacement operation. Every sample of the input signal is replaced by the convolution operator, scaled by the amplitude of the input sample.

A reasonable way to get a mental handle on this process is to do the math on paper with something like a 10 sample input signal and a 3 sample operator.

If the input signal is a single spike surrounded by zeros, the result of the convolution operation is the convolution operator, i.e. you get exactly one copy of the operator, scaled by the amplitude of the spike. This is easy to check in a DAW, just create a track with a single spike in the middle, next apply reverb, next save the output, and finally load it back into the DAW and you will see the convolution operator that is being used.

That's convolution reverb in its simplest form.

Software vendors add other features like ways to shape the tail (end) of the reverb (convolution operator) or to apply EQ to the reverb,...

The theory is simple. The practice of designing a good sounding convolution reverb that doesn't consume every cycle of CPU power is the art.
Old 9th September 2011
  #10
Lives for gear
 
Warp69's Avatar
 

Convolution and forward.
Old 10th September 2011
  #11
restpause
Guest
They actually teach a college course just about convolution at the Berklee school of Music. Maybe get in contact with them, find out who teaches it, and interview them. That might get killer results for your assignment.
Old 10th September 2011
  #12
Gear Guru
 
kafka's Avatar
Quote:
Originally Posted by mmcfarlane View Post
The theory is simple. The practice of designing a good sounding convolution reverb that doesn't consume every cycle of CPU power is the art.
+1. It's a very CPU intensive operation by nature, and also, if there is no cleverness to the design, adds huge latency. The difference between convolution plugins is in efficiency and the quality of the impulse responses.
Old 10th September 2011
  #13
Lives for gear
 
jupiter8's Avatar
 

Quote:
Originally Posted by kafka View Post
+1. It's a very CPU intensive operation by nature, and also, if there is no cleverness to the design, adds huge latency.
Actually if you do them in the simplest possible way they have no latency what so ever.
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