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Looking for the chart that converts XILICA or others to others
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<blockquote data-quote="John Roberts" data-source="post: 88124" data-attributes="member: 126"><p>Re: Looking for the chart that converts XILICA or others to others</p><p></p><p></p><p>I'm not sure if we are on the same page or not. I am more familiar with analog design than DSP. In analog all the variant boost/cut EQ BWs are ultimately derived from a recognizable BP filter, but that bandpass gets added or subtracted from the dry signal differently resulting in the different shapes. So the poles could be strictly defined and still not completely define the resulting transfer function. </p><p></p><p>This is even consistent with what we see.. the CF and boost/cut is correct, just the shape of the EQ varies.</p><p></p><p>To repeat my question, if EQ in the context of speaker management is trying to correct for a single driver's frequency response, this should (?) be simple. If trying to correct for the summed response of two drivers, no longer so simple. </p><p></p><p>math is not my native language, but I had some general discussions with at least one DSP designer years ago when I first looked into this. </p><p></p><p>Yes, LR-24 and entire universe of common HP/BP/LP filter alignments are well defined wrt what BW/Q means. Only the basic boost/cut EQ section suffers from lack of clear concise definition. Note: boost/cut EQ are used in other places than speaker management, so this is a larger problem mostly ignored. </p><p></p><p>Getting really old school, I've seen RIAA or NAB EQ specifications provided literally as a full table of X dB at Y frequency, with accompanying pole and zero time constants. </p><p></p><p>That is the crux of the matter. I have designed several different parametric EQ over the decades, all different using subtly different topologies. One even had an intentional interaction between Q and boost/cut designed in, so it got narrower for large amounts of boost/cut, and broader for small adjustments (as a first order correction for apparent loudness change in a hifi application). I didn't even try to put BW numbers on the Q control with that one. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> </p><p></p><p>How many possible variants are there for boost/cut filters using the same CF and boost/cut? My premise (hope) is there are only a handful but perhaps not. If not, there needs to be some more literal description of transfer function short of the X/Y plot to accurately communicate this transfer function. </p><p></p><p></p><p>This is not the first time the industry has quibbled over standards that will create immediate winners and losers. I see benefits from defining these EQ beyond just speaker management, and it is a little embarrassing to think of this as still undefined concisely. It is the repeatability and portability "promised" by digital audio technology, that highlights this glaring discrepancy. </p><p></p><p>There has to be a better way. </p><p></p><p>JR</p></blockquote><p></p>
[QUOTE="John Roberts, post: 88124, member: 126"] Re: Looking for the chart that converts XILICA or others to others I'm not sure if we are on the same page or not. I am more familiar with analog design than DSP. In analog all the variant boost/cut EQ BWs are ultimately derived from a recognizable BP filter, but that bandpass gets added or subtracted from the dry signal differently resulting in the different shapes. So the poles could be strictly defined and still not completely define the resulting transfer function. This is even consistent with what we see.. the CF and boost/cut is correct, just the shape of the EQ varies. To repeat my question, if EQ in the context of speaker management is trying to correct for a single driver's frequency response, this should (?) be simple. If trying to correct for the summed response of two drivers, no longer so simple. math is not my native language, but I had some general discussions with at least one DSP designer years ago when I first looked into this. Yes, LR-24 and entire universe of common HP/BP/LP filter alignments are well defined wrt what BW/Q means. Only the basic boost/cut EQ section suffers from lack of clear concise definition. Note: boost/cut EQ are used in other places than speaker management, so this is a larger problem mostly ignored. Getting really old school, I've seen RIAA or NAB EQ specifications provided literally as a full table of X dB at Y frequency, with accompanying pole and zero time constants. That is the crux of the matter. I have designed several different parametric EQ over the decades, all different using subtly different topologies. One even had an intentional interaction between Q and boost/cut designed in, so it got narrower for large amounts of boost/cut, and broader for small adjustments (as a first order correction for apparent loudness change in a hifi application). I didn't even try to put BW numbers on the Q control with that one. :-) How many possible variants are there for boost/cut filters using the same CF and boost/cut? My premise (hope) is there are only a handful but perhaps not. If not, there needs to be some more literal description of transfer function short of the X/Y plot to accurately communicate this transfer function. This is not the first time the industry has quibbled over standards that will create immediate winners and losers. I see benefits from defining these EQ beyond just speaker management, and it is a little embarrassing to think of this as still undefined concisely. It is the repeatability and portability "promised" by digital audio technology, that highlights this glaring discrepancy. There has to be a better way. JR [/QUOTE]
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