If you haven’t yet checked out Acustica Audio’s Nebula VST plug-in, i highly recommend it. Read my comprehensive Nebula review.
For those of you that are using the plug-in, and would like to get the very best sound quality from it, the good news is that there are various tweaks that can be applied to do just that. The best tweak to my knowledge is altering the way that the plugin plays its various kernels for each individual program.
What Is A Kernel In Nebula VST, And Why Would I Want To Alter How It Plays?
If you have used a convolution reverb you will be familiar with the term ‘impulse’. In the case of a reverb program it is a static snap shot of a room’s reverb taken by making a recording of the room in the real world. You can think of Nebula’s kernels as impulses, but there are a lot more of them and they record much more data about the sampled hardware.
These sampled kernels must be processed along with your audio to produce the final sound. Nebula’s engine has 3 different modes that can be used to perform this:
- 1. FREQD mode
This uses the same standard convolution engine that programs like Altiverb and Space Designer use, FFT (fast Fourier transform). In the Nebula support forum the programs’ designer himself, giancarlo, said:
“Freqd is the classic fft algo used by best plugins around, so it’s not so bad”
- 2. TIMED mode
This is also known as ‘direct convolution’. It is very CPU intensive, but more accurate and produces better sound quality. How much better we will discuss later.
- 3. SPLIT mode
This is a hybrid of the 2 modes. It is assumed that the main advantages of using TIMED mode is in the effect on the transients of the sound, the very first portion. It is in this first part that the listener hears many subconscious cues about all sorts of interesting aspects of the sound. It is also the part responsible for the punch of percussive instruments.
SPLIT mode lets you process the first part of the sound in TIMED mode (ie the transients), and the second part (the tail) in FREQD mode
OK, What Button Do I Press To Increase The Sound Quality!?
Sorry, this is Nebula we are dealing with 🙂 Nothing is easy or straight forward. We need to jump through a few hoops first, but don’t worry, all the info you need is right here. We need to make a global settings change, and then alter each program one at a time.
Step 1 – Modify The XML File
Nebula VST by default is installed in your DAW plug-in directory as 2 versions. Nebula and Nebula Reverb. Nebula Reverb is the same as Nebula but with higher quality, higher CPU use defaults. We of course use this version as a starting point.
The .DLL file that is the actual program has a corresponding .XML file with the same name. This contains the settings, and this is what we will be modifying in a text editor.
It is possible to change the names and copy the files of the .DLL and the .XML files if you want to make different versions of Nebula with different settings for latency and quality. This is what i have done, but don’t let it bother you. My main Nebula files live in C:Portable Apps/Reaper(x64)/Plugins/VST/acustica and are called:
Yours may differ, they could be in Program Files/Steinberg/Cubase Studio 4/VSTPlugins/acustica… i am sure you can find them in whatever plug-in directory they live.
I am using windows, so regret i can’t comment on the mac version, but i am sure any text editor will do. In windows open the XML file in notepad by right-clicking the file and selecting open with notepad:
You will now have the following open in your text editor, i have highlighted the only line you need to change:
The parameter is changed to <LTIMED> 100000 </LTIMED> . This lets us use up to 100ms of a TIMED kernel, any more and your CPU may explode, and it’s not needed. Hit save, boot up your DAW and we will go straight to the video to explain how to change the settings inside Nebula:
So now you can alter your own preamp programs to run on TIMED kernels! Hit the save button to make the change permanent, or better still make a copy of the program first so you don’t mess anything up by accident.
How much better is the sound quality in TIMED mode?
There has been quite a lot of talk on the Nebula forum about this subject, the main related thread is:
I would like to thank all the forum members who contributed to this thread as they were the inspiration for this article.
I can detect different things in different audio. I don’t want to put ideas in your head of what to listen for, but a subtle ‘tightening’ and little more punch is what i am mainly picking up. Its not massive, but if you are into sound quality and have a decent CPU well worth it for the 5 minutes it takes to edit the program.
Download An Example Of TIMED vs FREQD
I have rendered for you 2 versions of an interesting old stereo percussive bongo loop (16bit / 44.1 / FLAC) through the Analog In The Box ‘Fate’ compressor preamp using both TIMED and FREQD:
Please let me know in the comments below what differences you can detect, it would be very interesting.
If you want to get deeper into this subject I highly recommend you check out my Nebula Explained Udemy course. There is a section devoted entirely to the Kernel page.
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