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Convoluted Convo
I started this thread to discuss all things related to convolution and IRs. Following up from a discussion about Convolutor PE in another thread.
In that conversation, we were discussing the various flavors of IR-based reverb.
Ignore this test. @rs2000 caught a problem in how I set this up. I'll re-do the tests and post a link down thread.
~~To get things going, I created an audio file that has piano panned all the way to the lef and bass all the way to the right.
One version of the file was processed on my Mac through Altiverb 6 using the Gol Gumbaz stereo-to-stereo IR. Another version was created by processing the dry audio through Rooms! AU using a pair of stereo IRs that I created (for my own personal use) from the Gol Gumbaz stereo-to-stereo IR that is an attempt to create a full stereo IR. (One stereo IR is for the left channel input and one stereo IR is for the right channel input). There is a third processing that processes the source using Rooms' dual mono method -- basically provided to demonstrate why the dual mono approach used by most iOS convolution apps is problematic if you've got a stereo source that has elements panned wide.
A zip can be grabbed here with the three examples. They are named A, B and C in order to reduce confirmation bias.
https://www.dropbox.com/s/xwjzghv6bx12cc9/ReverbTestUpload.zip?dl=0~~
Comments
Guess we need a new forum section: Research groups 😅
I am curious as to how similar the full stereo versions seem to folks. I assume the dual mono will e obvious.
Totally.
I didn't expect this.
Let's go.
@espiegel123
Thanks for reducing confirmation bias.
It's a good way to do it.
File downloaded.
I'm writing as a listener here.
A the reverb is more comfortable, it has depth forward as well as width ways.
B the reverb has width, but it doesn't have a centre
C the reverb feels totally separate, it feels great for sound design but
it could easily be created by panning hard left and right and using any
standard algorithmic or convolution reverb.
Really like the piece.
Very calming.
Thank you.
@Gravitas : thanks for your comments. I am glad you didn't hate the piece -- I threw it together quickly to suit the needs of the test. FWIW, this reverb has a 23 second tail. If we hear from more people, I may try another comparison with the true stereo processing versions to minimize the possibility that differences are due to different calibration of the dry/wet settings. I am realizing that even a slight difference in the relative volumes has a big effect.
A and B similar. A has sharper, better defined high and more extreme, fraying low reflections. B appears more subdued / filtered. Preference would depend on targeted effect.
C in entirely different category (2 separate tracks).
@espiegel123 : Thanks for putting this one up for comments.
MY TAKE: B edges out A in my rankings just slightly and C just seems like wet/dry ratio is dialed back too far to compete for my tastes. Such a tricky task to design the test, IMHO. Still, I'm interested in learning which set up matches each audio. Tho' I'm still not sure I'll take the information and change anything. One of them will seek to me and not crap out too often.
If C had was less dry it might have got more of my attention. I love reverb to a fault.
It just makes impulses have an afterlife.
I also love great impulses and the source material nailed that too.
It's likely I'm going to buy the JAX Convolution IAP product just to support an interesting developer and add it to my options for IR reverbs.
@McD : one of the examples is expected to be unsatisfactory because the iOS reverb plugin (not JAX Convolutor -- which doesn't allow custom IRs) doesn't do full stereo -- it does dual mono (more discussion about that starting here: https://forum.audiob.us/discussion/comment/734223/#Comment_734223)
The reason for including the dual mono is that all of the iOS convolution apps other than JAX do dual mono (unless you use the method that I described that lets you do full stereo in Rooms). For most sources, the problems with dual mono aren't as apparent as in the examples I posted -- because my source audio has the piano and bass panned hard.
Most people (me included) hadn't even noticed that the iOS convolution apps were doing this (or at least those that knew didn't comment on it).
@espiegel123 How do you know that Convolutor PE does not do dual mono?
When you use a hard-panned source, it's is reverbed on left and right channels. In dual mono, an instrument panned all the way left has its reverb only on the left channel.
I am not sure what the picture’s significance is. A simple test for dual mono is to take a stereo file that has audio only on the left channel and run it through the reverb. With all the iOS convolution reverbs I checked other than JAX, the right channel was silent. There are workarounds using multiple instances of the AU convolutors. I don’t know what iConvolver does , though.
If you set the rev. width knob like in the screen shot, JAX will behave just like the others.
Thanks for the info. I wonder what that width control is doing.
We can only guess.
From my experience with other plugins and from listening to it I'd say that it operates like the rather common "stereo width" control:
0%=Mono, 50%=Stereo, 100%=Widened stereo (usually achieved by adding some phase-inverted component from the opposite channel).
I like it that way because it lets us increase the stereo effect of some IRs with limited stereo width.
One of the things I love in mixing is reverb and I had noticed that the reverbs on iOS didn’t have much width.
Now, with these tests,
I’m starting to understand why.
The other tool that could come in useful for others like myself is
the stereo tool, again from Jens Guell.
I place that after a reverb when
it’s being used in an Aux channel
with the setting between 25% and 50%.
A little but off topic I know but relevant to creating a sense of space.
Looking forward to
hearing more results.
I’m going to do some
more tests as well myself.
Have a great day.
@rs2000 : any thoughts about the reverbs in the examples I uploaded?
FWIW, Rooms running two different IRs (the L and R IRs of a true stereo IR pair) with 23 second tails and setup to be full stereo, runs fine with a buffer of 256 in AUM. Crackle-free on my iPad 6th Gen.
(If you have the two stereo IRs needed for full stereo, you run two instances of Rooms. Each on its own bus. Set one to mono left and the other to mono-right. When the signals are recombined they add up to a true stereo reverb.)
@rs2000 : btw, I had confirmation from AudioEase that for creating stereo-to-stereo IRs what they mean is that that when you set up the left and right speakers, you capture one stereo IR for the left speaker and then another one for the right speaker. So, true stereo is the same for AudioEase and LiquidSonics.
A: Stereo signal, mono effect
B: Stereo signal, stereo effect
C: Stereo signal with each channel processed by a mono IR
I found it a bit hard to differentiate because the IR has little treble but that's what I hear.
There's no doubt that the algorithm needs some optimization. If there's another app that does it better without using "fake news" then there must be a way.
Aah, good to know they're talking about the same thing.
AudioEase would do good in updating their descriptions to be more clear about creating IRs correctly.
I wonder how many users have already set up two speakers in the room to capture and recorded the IR with the source signal fed into both speakers
After reading the various comments, I think I should probably re-do the the examples if people are still interested. I probably don't need to include the dual mono example since it is so obviously that it is unsatisfactory for material that has anything panned very far from the center.
I think when I re-do the examples, I'll include the 100% wet signals. And I'll do the dry+wet combination in the same app to eliminate different calibration of the pots since it seems like a small difference in the dry level makes a big difference on the impression.
Would folks be interested to compare the full-wet of the AltiVerb and Rooms version?
If you have the energy, I'd appreciate the listening test and reading the views of those that
also reply and then learning from the "reveal".
I love Altiverb as a magical tool for generate a massive space... the "Taj Mahal" IR is a favorite because I was able to experience that amazing marble enclosure and experience the most surreal acoustic environment. We probably take these experiences for granted now along with the amazing synthesis engines we can pick up for $10.
Let's continue the convoluted convo(y).
Feel free to post as many audio files as you have the juice to squeeze out...
and maybe share the dry audio source so we can see how music is impacted by these tools too.
Might be able to add Convolutor PE to the mix if you capture one of its IRs and if that is usable. (Though that would limit the IRs to choose from.)
@McD: I think the IR that I used for this might be the one you meant when you said "Taj Mahal". I don't think there is a "Taj Mahal". I used the "Gol Gumbaz" IR which has about a 24 second tail: https://www.audioease.com/IR/VenuePages/golgumbaz.html
I thought there was a "Taj Mahal" IR, but it seems like I was mistaken. I have the complete AltiVerb 6 set -- and I don't see Taj Mahal listed as being in version 7.
I think when I re-do the example. I need to include some notes in higher registers.
I will also use a couple of other IRs that are shorter.
I'll wait to comment on A and B a little just to see if anyone else wants to comment.
@espiegel123 He was thinking of AlitSpace
Ah! Ok. If I am not mistaken, AltiSpace's Taj Mahal IR is an IR of the "Taj Mahal" preset of a hardware reverb.
Interesting! May have to download that one again to check it out. I couldn't figure it out last time. All of the presets sounded the same to me.
Given the current state of things, I don't know that AltiSpace is something that I'd recommend. It has some nice features, but it also doesn't do true stereo. There are now really good algorithmic reverbs and the AU convolution apps perform just as well (or poorly). AltiSpace has some bells-and-whistles but I don't know that in this day, they make it worthwhile.
@espiegel123 I'm perfectly happy with Rooms!AU to be honest. I mostly record in mono anyways. Insert Brian Wilson quip about stereo here.
Apparently, most folks do which is why it hasn't been a major point of discussion that most of the IRs floating about are of the mono-to-stereo variety.