setting up a drum bus??

Discussion of music production, audio, equipment and any related topics, either with or without Ableton Live
Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sun Sep 06, 2015 4:19 pm

OK, so I did some more testing as this was quite hard to hear.

I resampled the same drum sound routed to a drum buss and sending to a compressor in a return track, once with the return going to the master and a second time when going back the drum buss that.

When playing these together in stereo or if panned hard left and right they did sound quite similar. When in stereo and adding Utility with the polarity inverted on the second track it was clear that they didn't cancel each other out. A copy of the first recording did cancel out.
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Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sun Sep 06, 2015 5:25 pm

brian sansone wrote: When I do that , something goes horribly wrong. The audio coming out sound terrible with what sounds like phasing problems.

What am I missing??
The fact seems to be that sends are not fully delay compensated in some routing schemes. To me this feels like an overlook and not something to be expected.
Stromkraft wrote: I resampled the same drum sound routed to a drum buss and sending to a compressor in a return track, once with the return going to the master and a second time when going back the drum buss that.
I analyzed my 2 resampled recordings with normal routing (1 below) and rerouted back to the drum buss (2 below) and it's clear these 2 are not synced timewise.
Image
Last edited by Stromkraft on Sun Sep 06, 2015 8:08 pm, edited 1 time in total.
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Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sun Sep 06, 2015 5:40 pm

Stromkraft wrote:
The fact seems to be that sends are not fully delay compensated in some routing schemes. To me this feels like an overlook and not something to be expected.
Well, further tests indicate sends are possibly never delay compensated. Maybe there's some explanation for this, but it's still a letdown. That was good you catched this, Brian. Thanks for sharing your concerns and I apologize for my initial lack of ability to grasp the full issue at hand here.
Last edited by Stromkraft on Mon Sep 07, 2015 12:11 pm, edited 2 times in total.
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Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sun Sep 06, 2015 5:49 pm

Here's some older background from [nis] Nico in 2009 on the feeding back routing. I'm not sure how it applies today, but likely most of it does apply.
[nis] wrote:
1. PDC on Send/Return tracks:
Plugins on return tracks will be fully compensated just like on any other tracks. One thing that won't work is to feed a send into itself. This makes plugin delay compensation technically impossible as its caught in an endless loop.

2. No phase cancellation when you route returns back to an audio track:
This is true. The reason for this is the way how Live calculates your audio signals. A complete explanation would be a bit too much here, but in a nutshell it works like this: Live looks at all your tracks, collects the data of the current sample which needs to leave your computer next and sends it to your audio driver. This is one calculation cycle. Once this has been done, it starts the next calculation cycle for the next sample and so on. The return tracks are the last parts included in a calculation cycle. If you now route an audio signal from a return track back into an ordinary audio track, it will always be late, because the previous calculation cycle (which contained the data of your audio and MIDI tracks) has already been finished and has literally left your computer. This makes it impossible to get complete phase cancellation in such a scenario. In theory you should get the same problems in any other DAW, perhaps just at a different point than on the return tracks.
Scary thread about Live on KVR - please address!
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Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sun Sep 06, 2015 7:19 pm

brian sansone wrote:Well I thought I knew what how to set up a bus in Live.

So I route several tracks hosting drum sounds ( played by a simpler) over to a track named "Drum Bus"

That way I can process the drum sounds all together. but.... I also have a return channel set up with parallel compression.
The processed compression signal is sent to the master track.

So If I try to do a filter sweep on the drums via a filter on the "drum Bus" track, the drum bus signal affected, but the parallel
compression signal is not affected. I want to do a sweep on the entirety of drums.

So I thought I could just send the parallel compression signal to the drum bus . That way all the drum audio is running through the drum bus
and can be processed as a whole.

When I do that , something goes horribly wrong. The audio coming out sound terrible with what sounds like phasing problems.

OK, so I've found also a simple technique I overlooked when reading up about this situation: simply deactivate the sends on the drum buss by right-clicking on them and selecting that option. This will improve audio somewhat. In my quick newer experiment involving Utility on the return as the only effect it did not make polarity cancellation occur, but sound was certainly improved with or without Utility active (reversing the polarity or phase of the signal). EDIT** As you see in the next post this wasn't really true. I got these initial results because of different levels, so this first test was flawed ***

Again it was info from Nico, this time from 2011 (My bolded sections):
"There will be latency (*) on a return track if you route the return track's audio back into another audio track. The following problems will occur:

1. Such a routing can cause an infinite feedback loop, because you could (in theory) use the audio track's SEND controls to feed the signal back into the return track and so forth. In this case, Live cannot compensate latencies anymore, so the latency compensation will be deactivated for all tracks which are involved in this feedback network, regardless if the SEND control is indeed used by you or not. A possible solution is to deactivate the SEND controls on the audio track (right-click on the SEND control and choose "deactivate").

Note that the same problem may occur when you activate the SEND controls on the other return tracks, e.g. activate SEND B on RETURN A and SEND A on RETURN B.

2. There will always be at least 1 sample delay when routing a return track back into an ordinary audio track. This has to do with the computation cycle of the audio engine. Here's a (simplified) explanation: Live basically "scans" each of your tracks from left to right and "collects" each track's audio data, sample by sample. At the very end of each cycle, the master track's audio (or anything that is routed to your soundcard's output) will be sent to the DAC. Then it starts over, calculates the next sample and so forth.
Now, if you route audio from a return track back in to an ordinary audio track, this signal will always be delayed, because it falls into the next computation cycle. Thus you will never be able to reach full phase cancellation in such a routing scenario. There is no workaround for this. Note that this really only affects return tracks which are routed back into audio tracks. Routing an audio track into another audio track is no problem, regardless into which direction.
Re: Latency in Return Tracks
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Stromkraft
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Re: setting up a drum bus?? Possible fix

Post by Stromkraft » Sun Sep 06, 2015 7:59 pm

Follow-up:

I can report that I totally removed time-based phase issues with removing sends on any buss that the audio is routed trough in this simple experiment:

Source MIDI instrument 1 SynthDrum routes to 2 Drum buss which routes to Master. All of these faders are on xdB position.

SynthDrum sends 100% to the return track Utility Reverse (containing Utility switching polarity of the signal) with xdB fader position, which send its signal either to Master or Drum Buss, doesn't matter which. There is total cancellation provided the buss sends are disabled also when routing the return to the drum buss. If sending return to master it doesn't matter.

I'd say problem is solved! What do you think?
New Rule: Disable sends on busses or accept and deal with possible and nasty phase issues
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brian sansone
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Re: setting up a drum bus??

Post by brian sansone » Sat Sep 19, 2015 3:18 am

It does sound like comb filtering.
I would love to use only groups, but I have complicated set ups that cant always be grouped. Why.... I dont know.Ableton should allow groups
of groups, or groups of anything. I wish I could take a group, a midi track, two additional audio tracks, and group them all into a master drum buss.

brian sansone
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Re: setting up a drum bus??

Post by brian sansone » Sat Sep 19, 2015 3:39 am

so how the hell does one filter sweep an entire drum stem???

I just mentioned drums, but im going to have the same problem with all my stems; drums, synths, basses, etc....

I am trying to set up to dj my projects by simplifying everything to a few stems, and then doing your typical dj style stuff from there.

I never imagined I run into such prblems.

Thanks for all the input though


There must be an easy way. Render everything to audio??

Stromkraft
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Re: setting up a drum bus??

Post by Stromkraft » Sat Sep 19, 2015 4:12 pm

brian sansone wrote:so how the hell does one filter sweep an entire drum stem???
Well, you can do it directly on the buss. You don't have to use send and returns. We use all kinds of stuff on masters and busses all the time so I fail to see the issue, unless you must use sends on busses. Do you really?

Are you saying that removing the sends on the busses didn't change anything?
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