Hi I am Fabian, Music producer and DSP analyst. In this blog I will analyze and review, commercial and non-commercial audio plugins mostly in their analogue modeling accuracy – More about my work and background can be found at: www.prezjaproductions.com
This by all means will not be your run of the mill review posts, so before you get to the reviews there are a few concepts I need you to understand.
This is not a series of Reviews/Analysis focusing on the subject if something sounds good or not, but rather if the products can be considered analogue modeled, in regard to the generic analogue characteristics & behavior. Putting into test the developer claims.
Introduction to our measurements:
These ‘Graphs’ we will be looking at are called plots; the tool to look at a plot is an FFT analyzer.
- FR – Frequency Response
FR will be the first test that will provide us with the FR of the unit in question; there will be two types of FR. One will be Frequencies over Magnitude (dB) and Frequencies over Phase (Rotation, FR phase relationships).
- THD & THD+N (True Harmonic Distortion & True Harmonic Distortion + Noise)
To understand a system with an input and an output, such as an audio amplifier, we start with an ideal system where the transfer function is linear and time-invariant. When a signal passes through a non-ideal, non-linear device, additional content is added at the harmonics of the original frequencies. THD is a measurement of the extent of that distortion.
Simplistic Explanation: This type of measurement shows us if the unit distorts and how it distorts.
- DSC – Dynamic Static Characteristic
DSC is the unit’s envelope, and dynamic response. Analogue units do not have a linear dynamic response, they might have near linear FR that will automatically have a near linear DSC. To get a rough idea think of your digital compressor graphs that twist downwards as you increase the ratio. While the former is just a visual representation of the performed setting. DSC is conducted in real time and is the actual envelope representation.
While these plots might seem like a series of isolated tests, some -are very connected to each other and some are not.
Bellow I will demonstrate the most common relationships:
Signs to represent the connection =>, <=, <=>
- A=>B = A effects b
- A <=B = B effects A
- A<=>B = They are interlinked
- A*<=>B= They are interlinked if a special criteria is met in the implementation of A
- A<=>B*= They are interlinked if a special criteria is met in the implementation of B
Common relationships are:
- FR<=> DSC: This relationship tends to be one of the strongest it both if FR is pre/post DSC. The more extreme the FR (post DSC) the easier it is for the DSC to look like it has a nonlinear response, this is sort of a false positive while there is a optimal threshold for dsc rougness that can be preserved only when FR is pre DSC, as in analogue units the fr will almost always be pre DSC and the interconnection with DSC is to be expected and logical. In other words, a true analogue envelope response is directly derived from an analogue modeled FR that is pre DSC.
- DSC<=>FR*: This relationship exists when the dsp module that is related to FR is pre DSC, while post DSC the FR module does not have this relationship. This is something common in compressors when the units envelope will effect the Fr. This could not happen if the fr is post the envelope.
- FR=>THD: This relationship in most cases is not strong, it has minimal interaction but it exists.
- THD*=>FR: In some instances the distortion increase/decrease can interact with the FR.
- DSC=>THD: This relationship exists both in analogue modeled units, and digital ones. Sometime domain parameters such as attack/release/hold etc. have an effect on this relationship. It is important to notice that the relationship can be split into three categories, DSC effecting harmonic order relationships and Klirr, DSC effecting only Klirr and DSC being almost autonomous.
I’ll be commenting on the graphs in the reviews so you can really get how the ‘evaluation’ train of thought goes. It is important to read the reviews in chronological order! Not every case will be the same, and the commentary & additional information will differ. That’s why this is very important, since I will take into account this and skip additional explanations if posted in a previous review/analysis, in order to create a texture of understanding & a productive workflow.
Q: Why should I even care about this tech/geeky stuff, my ears tell me all the truth I need to know?
A: Let me put it simply, these reviews, are data. Data that will help us evaluate the nature of any DSP product. In other words, you’ll know if the juice was worth the squeeze.
Q: What software/plugins do you use for your measurements ?
A1: In my private research I use a variety of analyzer software
Here is a list of these software:
- SpectraPLUS – http://www.spectraplus.com/ ( Hardware measurements)
- Sonic Visualizer – http://www.sonicvisualiser.org/ (General Tasks)
- Voxengo Span – http://www.voxengo.com/product/spanplus/ (Inside DAW analysis)
- Christian-W. Budde – VST Analyzer (automated analysis for pluggins ) http://www.savioursofsoul.de/Christian/programs/measurement-programs/
The lab plots are mainly from Christian-W. Budde – VST Analyzer, although my version is not the public version.
Any future lab posts about hardware analysis are from SpectraPLUS.
Let me make clear that. it is one thing to make a plot and another to read & translate the data properly, this is in fact what I’m doing in my Lab posts.
I would suggest to wait for the DIY posts, for instructions in these matters. Its is very common to build false impressions if there is no prior extensive experience and knowledge.
All the best