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Complex crossover networks are The Devil. As you observed, the human ear is largely insensitive to moderate variations in volume/frequency... but it's incredibl

by beat 12y ago

Complex crossover networks are The Devil. As you observed, the human ear is largely insensitive to moderate variations in volume/frequency... but it's incredibly sensitive to phase. Phase is how we discern directionality (stereo), among other things. So introducing complex phase shifts in the crossover in order to achieve flatness is a bad tradeoff, imho. To my ears, the best and most musical sounding speakers I've heard have time-aligned drivers and very simple crossovers. Tannoy, Spica, Vandersteen, and other such designs are clearer and less fatiguing. I'm a musician and have recorded numerous albums, and those speakers are the ones that match what I'm used to hearing the best. The fundamental problem is that we work on what we can measure. It's very easy to measure frequency response. It's very hard to measure phase alignment. So we fix what we can measure. If you want to see serious map-over-territory thinking, look at THD specs for amplifiers. It's super-easy to measure THD - just isolate harmonics of a sine wave a 1khz. Unfortunately, this has approximately zero to do with music, unless your idea of "music" is static sine waves. Recorded music has a 20-30db dynamic range (less in the case of modern pop) and covers ten octaves. Dynamic recovery behavior, intermodulation distortion, stuff like this is what gives amps their distinctive sounds - but it's nearly impossible to measure! So they sell what looks good on paper... THD. Sigh.

chillingeffect 12y ago
> incredibly sensitive to phase Under contrived situations such as square waves and headphones. However, in general, the ear is not particularly sensitive to phase. [0] [1] which both discuss, in particular, [2] and [3] as well as many others listed in their bibliographies. The stated conclusions are, emphasis mine, "Given the data provided by the above cited references we can conclude that phase distortion is indeed audible, though generally speaking, only very subtly so and only under certain specific test conditions and perception circumstances." [1] Reads may also be interested in an additional conclusion which reads thusly: "Room acoustics further masks whatever cues that the hearing process may depend upon to detect the presence of phase distortion." [1] [0] http://www.silcom.com/~aludwig/Phase_audibility.htm http://www.silcom.com/~aludwig/Phase_audibility.htm [1] http://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2 http://www.audioholics.com/room-acoustics/human-hearing-phas... [2] Lipshitz, Stanly P., Pocock, Mark, and Vanderkooy, John, "On the Audibility of Midrange Phase Distortion in Audio Systems,' J. Audio Eng. Soc., Vol. 30, No, 9, Sept. 1982, pp 580-595. [3] Toole, Floyd E., "The Acoustics and Psychoacoustics of Loudspeakers and Rooms - The Stereo Past and the Multichannel Future," 109th AES Conv., Los Angeles, Sept 2000.
mbell 12y ago
This comment covers much of what is wrong with common interpretations of acoustics. > the human ear is largely insensitive to moderate variations in volume/frequency... but it's incredibly sensitive to phase. No, it's not. The human auditory system is sensitive to time variation. Phase shift may contribute a time shift but only at frequencies low enough that their wavelength has reasonably relation to the spacing of the ears. For example at 10Khz the wavelength is far too short for 'phase' to impact arrival time. Ultimately what actually matters in this regard with the human auditory response is group delay, not phase. > Phase is how we discern directionality (stereo), among other things. As mentioned above, what matters in the context of what your saying is group delay, but that is far from the only thing that matters for directionality. The human psycoscoutic system is very complex, part of directionality is group delay, part of it is frequency attenuation caused by sound wrapping around the ear from the ear, part of it is a half dozen other things. 'Phase' doesn't come even close to being a catch all cause. > To my ears, the best and most musical sounding speakers And thus we've devolved from science, as this usually goes. What on earth does 'musical sounding speakers' even mean? > It's very easy to measure frequency response. It's very hard to measure phase alignment. I have no idea where you came up with this statement but it is very easy to measure the response of a loudspeaker, both in amplitude and phase. > If you want to see serious map-over-territory thinking, look at THD specs for amplifiers. It's super-easy to measure THD - just isolate harmonics of a sine wave a 1khz. THD can be measured at only 1Khz, but it isn't something intrinsic to what 'THD' means. Measuring at only 1Khz is generally indicative of a crappy amplifier manufacturer looking to inflate their power numbers. Proper specs will provide a 20-20kHz THD rating. > Dynamic recovery behavior, intermodulation distortion, stuff like this is what gives amps their distinctive sounds - but it's nearly impossible to measure! If an amp has a distinctive sound, it has failed to achieve it's core design goal. I'm not sure what you think is impossible to measure, but I assure you it is not.
- digitailor 12y ago
  Both your comments are heavyweight so I'm not trying to pick sides. (Sum your two perspectives and I think you're close to Ultimate Expert Comment.) I just want to mention that beat is talking about phase alignment between identical signals, which our perceptual network is incredibly sensitive to. Anyone who has ever done multi-mic recording can attest to the very real effect you can hear from lack of phase alignment, even if they have bronze ears. Even worse is if you duplicate two musical recordings and offset one, even by a tiny amount. This is a critical aspect of crossovers- since they contain the same signal, any phase differences between the intersecting components are easy to pick up by the ear and very difficult to measure since it won't show up as a significant frequency or amplitude differential. In the highly acoustically sensitive area where the crossover occurs, the phase distortion between the two signals is hard to pin down but it's definitely there, it's easy to hear by A/Bing. I mix on a multiple-monitor setup and the one that is most critical to me sounds like absolute garbage. However, it has a wonderfully "flat" response and allows you to get an idea of what proven aesthetically-unpleasing issues are present. It has no crossover. The goal is not to have perceived rumble, tinniness, or mud on any of the incredibly wide range of listening systems out there. I think this is what beat means by "musical"- flat speakers are actually not pleasant to the ears, but the most empirically useful. The most famous secret of many respected mix engineers is the Auratone. Michael Jackson's "Bad" was mostly mixed on this little thing. It sounds like absolute garbage aesthetically but reveals more issues in a mix than anything else. It's like when you first saw things under a "blacklight" as a kid and got to see all the particulate matter covering everything, that you can't see with the naked eye. Here's more about the Auratone. I hope my comment has helped to bridge this critical area of "musicality" vs. empiricism. http://www.trustmeimascientist.com/2012/02/06/auratone-avantone-behritone-review/ http://www.trustmeimascientist.com/2012/02/06/auratone-avant... Postscript- the listening environment is the most important aspect! Always! You can have the best mastering grade monitors on earth in an improperly treated room, and it's all for naught!
VLM 12y ago
"So they sell what looks good on paper... THD" From an EE perspective most of the "obvious" ways to screw up THD sound truly horrible. Crossover distortion, clipping, bias problems, truly excessive hum or noise... Also note that just because your final PA is a modern class D doesn't mean there's not some opamp input stage in the box that is perfectly liable to classical transistor bias problems. So you can't get crossover distortion out of a modern class D amp final device as an inherent part of how those switch the transistors, but that doesn't mean you can't screw up the input stage of the opamp that is inside the box of an amp that none the less has a D-type output final stage. In terms of circuit design, A guy who can design a nice class D stage is not necessarily (but often is) the same guy who can design a class A or AB stage. "Necessary but not sufficient" is a good way to describe good THD numbers. I would have to think for awhile how to get a good THD number with foul intermod numbers... Maybe if you fed in two noise signals outside the freq bandwidth that when nonlinear mixed gave a difference freq of 2 KHz that would sound horrible even if a pure sinewave input at 1K sounds awesome. It would take some work to screw up an amp this way but it could happen. Anyway nothing says "tradeoff" like engineering and I wouldn't trade off a pretty basic core characteristic like THD for improved ... anything, except maybe power level. I'd rather hear something good than something a couple dB louder. Reporting good THD is valid in marketing as a way to tell that you did at least the very first homework problem... I agree totally with you that there are multiple steps beyond it, but there's no point in working on any of them if you can't pass the first simple THD test. (Edited to add, I missed the PERFECT analogy: Its like passing the UL Labs certification that it probably won't burn your house down. That's kinda required, and its also possible to aim a little higher)
- beat 12y ago
  Back in the day, I used to build Class A directly heated triode tube amps for hi-fi. These are poo-poo'd by the self-styled "scientific" hi-fi community for their high THD specs. But it's important to think about not only how much distortion is happening, but where the distortion is happening. In super-simple triode tube circuits with no negative feedback loops, THD is pretty much linear to the volume. For small signals - the detail in the mids and highs - distortion is effectively unmeasurable. The mainstream A/B transistors + heavy negative feedback architecture has the benefit of low manufacturing cost (no need to match devices when you just feedback the differences out) and good specs. But where does the distortion happen? At the Class A/B crossover point, somewhere in the first watt. Until the amp hits maximum power and clips, the WORST distortion is in the first watt, where all the small signals live. To my common sense and my ears, this explains how good-spec amps can sound very harsh and cold, while bad-spec amps can sound sweet and warm. It's not "euphonic distortion", as the pseudo-scientists claim. Rather, it's that the warm amp is actually distorting less where it actually matters.

by beat 12y ago

chillingeffect 12y ago

> incredibly sensitive to phase Under contrived situations such as square waves and headphones. However, in general, the ear is not particularly sensitive to phase. [0] [1] which both discuss, in particular, [2] and [3] as well as many others listed in their bibliographies. The stated conclusions are, emphasis mine, "Given the data provided by the above cited references we can conclude that phase distortion is indeed audible, though generally speaking, only very subtly so and only under certain specific test conditions and perception circumstances." [1] Reads may also be interested in an additional conclusion which reads thusly: "Room acoustics further masks whatever cues that the hearing process may depend upon to detect the presence of phase distortion." [1] [0] http://www.silcom.com/~aludwig/Phase_audibility.htm http://www.silcom.com/~aludwig/Phase_audibility.htm [1] http://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2 http://www.audioholics.com/room-acoustics/human-hearing-phas... [2] Lipshitz, Stanly P., Pocock, Mark, and Vanderkooy, John, "On the Audibility of Midrange Phase Distortion in Audio Systems,' J. Audio Eng. Soc., Vol. 30, No, 9, Sept. 1982, pp 580-595. [3] Toole, Floyd E., "The Acoustics and Psychoacoustics of Loudspeakers and Rooms - The Stereo Past and the Multichannel Future," 109th AES Conv., Los Angeles, Sept 2000.

mbell 12y ago

This comment covers much of what is wrong with common interpretations of acoustics. > the human ear is largely insensitive to moderate variations in volume/frequency... but it's incredibly sensitive to phase. No, it's not. The human auditory system is sensitive to time variation. Phase shift may contribute a time shift but only at frequencies low enough that their wavelength has reasonably relation to the spacing of the ears. For example at 10Khz the wavelength is far too short for 'phase' to impact arrival time. Ultimately what actually matters in this regard with the human auditory response is group delay, not phase. > Phase is how we discern directionality (stereo), among other things. As mentioned above, what matters in the context of what your saying is group delay, but that is far from the only thing that matters for directionality. The human psycoscoutic system is very complex, part of directionality is group delay, part of it is frequency attenuation caused by sound wrapping around the ear from the ear, part of it is a half dozen other things. 'Phase' doesn't come even close to being a catch all cause. > To my ears, the best and most musical sounding speakers And thus we've devolved from science, as this usually goes. What on earth does 'musical sounding speakers' even mean? > It's very easy to measure frequency response. It's very hard to measure phase alignment. I have no idea where you came up with this statement but it is very easy to measure the response of a loudspeaker, both in amplitude and phase. > If you want to see serious map-over-territory thinking, look at THD specs for amplifiers. It's super-easy to measure THD - just isolate harmonics of a sine wave a 1khz. THD can be measured at only 1Khz, but it isn't something intrinsic to what 'THD' means. Measuring at only 1Khz is generally indicative of a crappy amplifier manufacturer looking to inflate their power numbers. Proper specs will provide a 20-20kHz THD rating. > Dynamic recovery behavior, intermodulation distortion, stuff like this is what gives amps their distinctive sounds - but it's nearly impossible to measure! If an amp has a distinctive sound, it has failed to achieve it's core design goal. I'm not sure what you think is impossible to measure, but I assure you it is not.

digitailor 12y ago
Both your comments are heavyweight so I'm not trying to pick sides. (Sum your two perspectives and I think you're close to Ultimate Expert Comment.) I just want to mention that beat is talking about phase alignment between identical signals, which our perceptual network is incredibly sensitive to. Anyone who has ever done multi-mic recording can attest to the very real effect you can hear from lack of phase alignment, even if they have bronze ears. Even worse is if you duplicate two musical recordings and offset one, even by a tiny amount. This is a critical aspect of crossovers- since they contain the same signal, any phase differences between the intersecting components are easy to pick up by the ear and very difficult to measure since it won't show up as a significant frequency or amplitude differential. In the highly acoustically sensitive area where the crossover occurs, the phase distortion between the two signals is hard to pin down but it's definitely there, it's easy to hear by A/Bing. I mix on a multiple-monitor setup and the one that is most critical to me sounds like absolute garbage. However, it has a wonderfully "flat" response and allows you to get an idea of what proven aesthetically-unpleasing issues are present. It has no crossover. The goal is not to have perceived rumble, tinniness, or mud on any of the incredibly wide range of listening systems out there. I think this is what beat means by "musical"- flat speakers are actually not pleasant to the ears, but the most empirically useful. The most famous secret of many respected mix engineers is the Auratone. Michael Jackson's "Bad" was mostly mixed on this little thing. It sounds like absolute garbage aesthetically but reveals more issues in a mix than anything else. It's like when you first saw things under a "blacklight" as a kid and got to see all the particulate matter covering everything, that you can't see with the naked eye. Here's more about the Auratone. I hope my comment has helped to bridge this critical area of "musicality" vs. empiricism. http://www.trustmeimascientist.com/2012/02/06/auratone-avantone-behritone-review/ http://www.trustmeimascientist.com/2012/02/06/auratone-avant... Postscript- the listening environment is the most important aspect! Always! You can have the best mastering grade monitors on earth in an improperly treated room, and it's all for naught!

VLM 12y ago

"So they sell what looks good on paper... THD" From an EE perspective most of the "obvious" ways to screw up THD sound truly horrible. Crossover distortion, clipping, bias problems, truly excessive hum or noise... Also note that just because your final PA is a modern class D doesn't mean there's not some opamp input stage in the box that is perfectly liable to classical transistor bias problems. So you can't get crossover distortion out of a modern class D amp final device as an inherent part of how those switch the transistors, but that doesn't mean you can't screw up the input stage of the opamp that is inside the box of an amp that none the less has a D-type output final stage. In terms of circuit design, A guy who can design a nice class D stage is not necessarily (but often is) the same guy who can design a class A or AB stage. "Necessary but not sufficient" is a good way to describe good THD numbers. I would have to think for awhile how to get a good THD number with foul intermod numbers... Maybe if you fed in two noise signals outside the freq bandwidth that when nonlinear mixed gave a difference freq of 2 KHz that would sound horrible even if a pure sinewave input at 1K sounds awesome. It would take some work to screw up an amp this way but it could happen. Anyway nothing says "tradeoff" like engineering and I wouldn't trade off a pretty basic core characteristic like THD for improved ... anything, except maybe power level. I'd rather hear something good than something a couple dB louder. Reporting good THD is valid in marketing as a way to tell that you did at least the very first homework problem... I agree totally with you that there are multiple steps beyond it, but there's no point in working on any of them if you can't pass the first simple THD test. (Edited to add, I missed the PERFECT analogy: Its like passing the UL Labs certification that it probably won't burn your house down. That's kinda required, and its also possible to aim a little higher)

beat 12y ago
Back in the day, I used to build Class A directly heated triode tube amps for hi-fi. These are poo-poo'd by the self-styled "scientific" hi-fi community for their high THD specs. But it's important to think about not only how much distortion is happening, but where the distortion is happening. In super-simple triode tube circuits with no negative feedback loops, THD is pretty much linear to the volume. For small signals - the detail in the mids and highs - distortion is effectively unmeasurable. The mainstream A/B transistors + heavy negative feedback architecture has the benefit of low manufacturing cost (no need to match devices when you just feedback the differences out) and good specs. But where does the distortion happen? At the Class A/B crossover point, somewhere in the first watt. Until the amp hits maximum power and clips, the WORST distortion is in the first watt, where all the small signals live. To my common sense and my ears, this explains how good-spec amps can sound very harsh and cold, while bad-spec amps can sound sweet and warm. It's not "euphonic distortion", as the pseudo-scientists claim. Rather, it's that the warm amp is actually distorting less where it actually matters.