Looking for the chart that converts XILICA or others to others

[Jeroen van Waterschoot]

Re: Looking for the chart that converts XILICA or others to others

I wonder if there would be resistance to bandwidth definition by some manufacturers because their filter definitions give a particular "sound" to their particular product, errors and all. In theory, if everyone's filter parameters matched, they should sound identical.

In an ideal world, there would only be one problem: How would all published settings and / or existing presets out there map onto the standard Q/BW definition? Even with no real-world technical reasons why DSPs sound different, and with no business reasons to want incompatible definitions, the transition to a standardized Q/BW definition would not be easy. Replacing many thousands of presets / units so that the "new" settings will sound correctly, while still being able to use them in a mixed setup with "old" products is not going to happen. So manufacturers will stick to their existing definitions until a standard emerges that they are forced to adopt for some reason.

Plus: The world is not ideal. Even with matching Q/BW definitions for Bell filters and shelving filters, DSP units will sound differently because of real-world limitations. The most obvious being sample rate. On the same processor, with the same Q/BW definitions, a given filter will sound differently when you switch from 48kHz sample rate to 96kHz sample rate. This is due to the "warping" of filter responses at frequencies near (or even not quite so near) half the sample rate, but also because of secondary effects such as simply the difference in the used anti-aliasing filters. Not to mention the percieved "sound" of different A/D and D/A converters, and analog signal paths that would cause the engineer to choose a different setting just because some opamps may sound different than others. Not to mention processing accuracy and dumb but human mistakes.

So, even with a fully standardized filter response, a 1:1 match would never be possible. And for reasons already stated in earlier posts, maybe not even desirable - from a manufacturer's point of view.

That being said, I am a strong supporter of standardizing Q/BW as a function of gain. I just don't see it happening.

 

[John Roberts]

Re: Looking for the chart that converts XILICA or others to others

In an ideal world, there would only be one problem: How would all published settings and / or existing presets out there map onto the standard Q/BW definition? Even with no real-world technical reasons why DSPs sound different, and with no business reasons to want incompatible definitions, the transition to a standardized Q/BW definition would not be easy. Replacing many thousands of presets / units so that the "new" settings will sound correctly, while still being able to use them in a mixed setup with "old" products is not going to happen. So manufacturers will stick to their existing definitions until a standard emerges that they are forced to adopt for some reason.

Perhaps. But until there is a standard there is no right and wrong, just closed solutions that only work on a named platform.

Once we have a standard there will be incentive for all who are not "correct" to get correct. It may not turn out to be a simple either or choice, but a handful of Q/BW types that can be specified. Digital interfaces are actually pretty good at re-mapping response, between different types, if the data exists to do so.

Plus: The world is not ideal. Even with matching Q/BW definitions for Bell filters and shelving filters, DSP units will sound differently because of real-world limitations. The most obvious being sample rate. On the same processor, with the same Q/BW definitions, a given filter will sound differently when you switch from 48kHz sample rate to 96kHz sample rate.

This is known and can be part of the specification for filters that range up into the upper octaves where such interactions are significant. Most crossover heavy lifting is at lower frequencies, but there are not that many choices for different sampling rates these days.

This is due to the "warping" of filter responses at frequencies near (or even not quite so near) half the sample rate, but also because of secondary effects such as simply the difference in the used anti-aliasing filters. Not to mention the percieved "sound" of different A/D and D/A converters, and analog signal paths that would cause the engineer to choose a different setting just because some opamps may sound different than others. Not to mention processing accuracy and dumb but human mistakes.

Differences due to execution will always be with us, and not my concern. As long as we can know precisely what transfer function is meant by X dB of boost, with Y Q/BW, even if we must also specify type Z Q/BW. The rest can fall within the +/- X dB window of accuracy.

So, even with a fully standardized filter response, a 1:1 match would never be possible. And for reasons already stated in earlier posts, maybe not even desirable - from a manufacturer's point of view.

That being said, I am a strong supporter of standardizing Q/BW as a function of gain. I just don't see it happening.

Me too... I see a multiple part problem. #1 come up with a characterization for the sundry different Q/BW variants. Once we can name/list them, then #2 becomes relatively straightforward to map between them. #3 officially declaring one correct, and the others not, can be left to the marketplace to prosecute with purchase preferences. The customers just need to be informed, so they can make informed choices. I could live without #3 if we had #1 and #2. Digital isn't perfect, but it is generally repeatable. Without concise definitions it is uncharacteristically chaotic.

JR