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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: vantheman on December 07, 2022, 10:18:04 AM

Title: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: vantheman on December 07, 2022, 10:18:04 AM
I looked around a bit for some answers to this, but I'm not using the right search terms. The situation is you have a stage mix with one instrument off to one side. I've seen this discussed in the context of bass that it's possible to shift the low end frequencies into the center of the mix where they belong. But I'm not sure what post production tools allow you to do this, or what applications have the tools. I do the bulk of my work in Audacity but I also use Izotope RX7 and Ozone 9. I'm thinking something like Izotope RX's spectral rebalance but for stereo image rather than levels.

I've thought about taking the entire mix, running a low pass filter on it, summing to mono and placing center in the mix, but is there a more intelligent way?

As a follow-up question - what are the limitations that one can expect from doing this? For example, with bass guitar, I can see it being straightforward (hypothetically with the tool I'm trying to identify) to move everything <120hz into the center of a stereo image, but then what can you expect for the higher registers of the instrument without making the mix sound even weirder?
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: hoserama on December 07, 2022, 11:06:41 AM
Try the Imager in Izotope Ozone. You can create a crossover around 120hz, and then just mono out everything below 120hz.

Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: nulldogmas on December 07, 2022, 12:25:14 PM
I looked around a bit for some answers to this, but I'm not using the right search terms. The situation is you have a stage mix with one instrument off to one side. I've seen this discussed in the context of bass that it's possible to shift the low end frequencies into the center of the mix where they belong. But I'm not sure what post production tools allow you to do this, or what applications have the tools. I do the bulk of my work in Audacity but I also use Izotope RX7 and Ozone 9. I'm thinking something like Izotope RX's spectral rebalance but for stereo image rather than levels.

I would use music rebalance in RX to separate the stems, then pull them all into Audacity and pan the bass stem way over to get it to where it sounds centered. I've done this before and it can work very well.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: Gutbucket on December 07, 2022, 04:47:40 PM
What nulldogmas said, assuming you are talking about the bass instrument sound.

I've not used RX myself. But a tool such as it's music rebalance function designed to isolate things like the bass instrument sound is more likely to do a better job of pulling that out and isolate it from everything else (assuming good functioning without significant artifacts), upon which you can adjust its level, panning, EQ, dynamics, effects or whatever else.

In contrast to that, a stereo imaging tool works on the entire program content.  Many stereo image manipulation tools have a multiband option built-in, which splits the frequency range of into several frequency ranges, typically three, allowing you to make separate adjustments to each band.  Applying something like that to the entire mix can sometimes be useful, but applied the above case makes for a rather blunt tool, affecting everything below the chosen crossover point in addition to the low frequency content of the bass instrument itself.  Also, that approach is likely to not fully address the entire range of the bass instrument sound - any fundamental frequencies or harmonics higher than the crossover frequency won't be effected.

Two different tools.

If the problem is something like the PA subwoofers being louder on one side, such that all music sources have their low bass frequencies skewed to that side, it may be more appropriate to use a multiband stereo imager on the recording without music rebalance. 

Or if that's not the case and instead the bass instrument sound itself is smeared in terms of its panning location across different frequencies, yet other instruments are not, maybe do both. First isolate the bass instrument sound using music rebalance (the isolated output of which should be in stereo) then "straighten it out" using a multiband imaging tool to get it's lower and higher frequency content aligned with each other in the panning sense, and then pan that were you want it to be the mix.


A warning on stereo image manipulation which "monofies" all low frequencies- Be careful when narrowing all bass content.  Doing so can be useful as a way to improve a specifically problematic recording, and is sometimes be useful in other ways, but don't mono low frequency content just because or by rote, or because that's what EDM music mixers do or whatever.   Doing so is not likely to make a recording unlistenable, but a lot of the feel of space, openness and "you are there-ness" of the live performance space is conveyed by way of low frequency difference information. It's one of the things that makes great live recordings special IMHO, and that gets minimized if not thrown out entirely when monoizing all low frequency content., and you are less likely to notice the severity of that if mixing on headphones or small speakers.  So use it, just don't' abuse it.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: EmRR on December 07, 2022, 06:13:34 PM
Some workstations have tools that allow separate control of middle and side, such that you can lose the side info up to the point it centers the bass.  There are also 3rd party panning plug-ins that offer centered bass.  Lots of options. 
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: nulldogmas on December 07, 2022, 06:29:53 PM
What nulldogmas said, assuming you are talking about the bass instrument sound.


Right, that. I assumed that's the case given the OP said "a stage mix with one instrument off to one side" — if it's one frequency off to one side, that's a whole nother kettle of fish.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: vantheman on December 07, 2022, 09:54:12 PM
I tried to be clever and create a versatile thread title, but yes I’m referring solely to centering the bass in my case. Thanks for all the replies. I’m going to think about this and take a crack at it this weekend.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: heathen on December 09, 2022, 09:18:37 AM
As a follow-up question - what are the limitations that one can expect from doing this? For example, with bass guitar, I can see it being straightforward (hypothetically with the tool I'm trying to identify) to move everything <120hz into the center of a stereo image, but then what can you expect for the higher registers of the instrument without making the mix sound even weirder?

The biggest limitation is that even with a muffled 60s bass tone the bass guitar sound extends well above 120 Hz.  The upper harmonics are going to be at least up to the 1 kHz range, and for anything but the most muffled tone they will go even higher.  So if you're hearing bass guitar off to one side and want to center it, moving everything below 120 Hz to mono in the center of the mix will almost certainly not move the sound of the bass guitar to the center.

To illustrate the point, here is a waterfall plot someone else made of a fretless bass playing the note F1:

(https://i.imgur.com/hmtTBLn.png)

I believe this had flat or tapewound strings, but even still look at those harmonics above 120 Hz.  If this was done with your average fretted bass, and particularly with roundwound strings, there would be noticeably greater energy in the upper harmonics and they would extend even higher in the frequency range.

All this is to say that unless you've got access to the multitrack that isolates the bass guitar in the mix, you're most likely not going to move it to the center of the mix.  Note, however, that I've never used RX.  If it can actually pull this off without noticeably altering the sound of the mix (other than where the bass guitar is heard in the stereo image) I'd be VERY impressed.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: nulldogmas on December 09, 2022, 10:53:28 AM

All this is to say that unless you've got access to the multitrack that isolates the bass guitar in the mix, you're most likely not going to move it to the center of the mix.  Note, however, that I've never used RX.  If it can actually pull this off without noticeably altering the sound of the mix (other than where the bass guitar is heard in the stereo image) I'd be VERY impressed.

It can, though obviously results vary depending on the source material. It is frickin' magic, or at least near Peter Jackson-level sorcery.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: heathen on December 09, 2022, 11:09:31 AM

All this is to say that unless you've got access to the multitrack that isolates the bass guitar in the mix, you're most likely not going to move it to the center of the mix.  Note, however, that I've never used RX.  If it can actually pull this off without noticeably altering the sound of the mix (other than where the bass guitar is heard in the stereo image) I'd be VERY impressed.

It can, though obviously results vary depending on the source material. It is frickin' magic, or at least near Peter Jackson-level sorcery.

Wow, that is wild!
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: capnhook on December 09, 2022, 03:01:58 PM
So good, it won an Oscar in 2021...

https://emmaazelborn.com/2021/02/rx-8-wins-academy-award/
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: Scooter123 on December 09, 2022, 10:27:07 PM
On RX7, just make a new track with Music Re-Balance, picking only the Bass Slider.  On Reaper or any other DAW, move the balance to left, center or right as your preference may dictate.  Then take the original track and remove the bass with a high pass filter below 180-300.
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
Post by: nulldogmas on December 10, 2022, 10:35:32 PM
On RX7, just make a new track with Music Re-Balance, picking only the Bass Slider.  On Reaper or any other DAW, move the balance to left, center or right as your preference may dictate.  Then take the original track and remove the bass with a high pass filter below 180-300.

That'll work, but I find it easier to split into four stems (bass, vox, percussion, other) in RX and then remix those in a DAW as I see fit.

Here's an example of the four stems I got from a recent Sarah Shook recording — listened to in isolation they're pretty artifacty, but once remixed they sound fine:

https://www.dropbox.com/sh/fweb030e3jzn56h/AADKZz0r-wa6AcIX0QJfUTYna?dl=0
Title: Re: Moving Frequency Ranges (Bass) Around in a Stereo Mix
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