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FAD, a proposed extension to FRD file format
I've been thinking about this for some time, and I feel an expanded and more robust format that is semi-backward compatible with current FRD would be very attractive to me. I'm not sure about others though, and hence the discussion. To make this work the software guys would have to be on board for support. Ultimately my goal here is to sell the idea to those and users. Here are my ideas:
Frequency Analysis Data (FAD), an extension on FRD file format.
The current base format of FRD would be maintained, as such: Asterisk denotes a comment. Each line contains Frequency <delim> Amplitude <delim> Phase. Values are floating point, as current standard.
First change: More Columns. A special three Asterisk *** comment in the header lists the format of each line. This always begins with FP0 AP0 PH0, which defines Frequency Point 0, Amplitude 0, Phase 0. It may also contain: THD, HD2, HD3, HD4, HD5. When these are present additional columns with Total Harmonic Distortion, and Harmonic Distortion order X is present as well on each line.
Second change. Column Tagging. Placing an *@ at the end of a column denotes a tag. Tag text follows. Example: *@ Spliced near field to far field here.
End Changes.
The proposed changes allow HD data to be placed inside the FAD file for display in crossover simulations.It also allows the recording of tags in the response to record important measurement notes.
In order to allow backward compatibility, the current FRD standard needs to change wording such that it ignores anything after the first three floats on each line. I don't think that is a difficult or demanding change to implement, personally.
Thoughts?
Frequency Analysis Data (FAD), an extension on FRD file format.
The current base format of FRD would be maintained, as such: Asterisk denotes a comment. Each line contains Frequency <delim> Amplitude <delim> Phase. Values are floating point, as current standard.
First change: More Columns. A special three Asterisk *** comment in the header lists the format of each line. This always begins with FP0 AP0 PH0, which defines Frequency Point 0, Amplitude 0, Phase 0. It may also contain: THD, HD2, HD3, HD4, HD5. When these are present additional columns with Total Harmonic Distortion, and Harmonic Distortion order X is present as well on each line.
Second change. Column Tagging. Placing an *@ at the end of a column denotes a tag. Tag text follows. Example: *@ Spliced near field to far field here.
End Changes.
The proposed changes allow HD data to be placed inside the FAD file for display in crossover simulations.It also allows the recording of tags in the response to record important measurement notes.
In order to allow backward compatibility, the current FRD standard needs to change wording such that it ignores anything after the first three floats on each line. I don't think that is a difficult or demanding change to implement, personally.
Thoughts?
= Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
Comments
I have been surprised in the past by the effects different crossover topologies have on non-linear distortion and not sure if that is predictable within a simulator or not, so as far as developing advanced modeling capabilities it may be somewhat limited similar to the diffraction/off-axis modeling currently available.
Extra data is always a good thing, however - and a certain tool I was working on sporadically up until about a year ago when a VS update broke my fucking code would fold nicely into this concept.
Essentially, I was calling it the "Loudspeaker Analyzer" and it was to import FRD/ZMA files and extract, based on user input of a reference frequency (default choices of 100 or 1000), a summary of +/- response, Zmin/Zmax, phase angles, actual crossover point (if a system FRD with a reverse null was entered), and upper/lower F3/6/10.
It ended up being very much more ambitious than I originally intended - scope creep got the best of me and when I spent a weekend writing a bass model module in order to generate an overlay consisting of modeled extension and baffle step loss in order to help hone in on BSC I realized I was A: in over my head and B: absolutely uninterested in reinventing the wheel as all of these features, while not present in any single piece of software, are nonetheless widely available.
The FAD format sounds simple enough and seems like it would be backward compatible, older software just wouldn't read the HD columns, right? I have taken programming classes, so my knowledge is very basic, I can read over code and have an idea of what it does, but that's about it.