A good speaker typically distorts up to 1% on average but can be much higher at lower frequencies and depending on the room. We might have >10% distortion under certain circumstances. Yet many amp designers speak about distortion profiles and so on at <0.1%. Arguably, in a hifi system the speaker makes the most audible difference to the listener, which is justifiable on the basis that the magnitude of distortion is higher and that frequency response can vary by a similarly large magnitude. Naturally we might ask what the significance is of 0.1% distortion in an amplifier if it's being distorted again by a factor of >10 by the speaker?
the order of the nonlinearity is of importance in determining the proliferation and level of InterModulation Distortion - higher order distortion is generally considered much more objectionable than just 2nd and 3rd
while there is no excuse today for such poor design there is a historical worry about zero crossing distortion in amplifiers - particularly low bias "Class B" outputs - where the amplifier's distortion may actually rise with decreasing signal level
while there is no excuse today for such poor design there is a historical worry about zero crossing distortion in amplifiers - particularly low bias "Class B" outputs - where the amplifier's distortion may actually rise with decreasing signal level
One argument is that speakers don't produce significant levels of higher order harmonics. I would like to see some evidence of that.
It's interesting that we measure the distortion of an amplifier at its output and not via the output of a speaker. Why is that?
It's interesting that we measure the distortion of an amplifier at its output and not via the output of a speaker. Why is that?
I agree with the Professor.
When today power amplifiers are dealing with THD 0.001 % levels
it is more a question of Loudspeaker distortion
if we want to improve sound quality. Substancially.
When today power amplifiers are dealing with THD 0.001 % levels
it is more a question of Loudspeaker distortion
if we want to improve sound quality. Substancially.
What about the fact that the music allready has been through 100 or 1000 circuits (recorcing, mixing and editing) before it even gets into your amplifier. All those circuits also adds distortion, that's passed on to the next circuits in line...........
yes to improve audio reproduction we should concentrate on speakers
look at Dr Geddes posts - having explored distortion audibility he considers speaker-room interaction, directivity control, frequency response, minimizing diffraction and high order propagation modes primary - and speaker driver distortion secondary
he doesn't worry about amps at all below a easily achieved threshold of "inaudibility"
he rates amp distortion unimportant as long as its low, and decreases as level decreases - demoing his (US$ 9K/pair) speakers with a Pioneer integrated amp
look at Dr Geddes posts - having explored distortion audibility he considers speaker-room interaction, directivity control, frequency response, minimizing diffraction and high order propagation modes primary - and speaker driver distortion secondary
he doesn't worry about amps at all below a easily achieved threshold of "inaudibility"
he rates amp distortion unimportant as long as its low, and decreases as level decreases - demoing his (US$ 9K/pair) speakers with a Pioneer integrated amp
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is speaker distortion dependent on level or frequency or temperature or even the room?
If it is level dependent then at what level is 1% or 0.1% distortion measured?
At what level would it reproduce with better than 0.01% distortion?
If it is level dependent then at what level is 1% or 0.1% distortion measured?
At what level would it reproduce with better than 0.01% distortion?
You're a clever man, you can find that out. The answer is here: View the 800 Diamond specifications at Bowers & Wilkins - The World's leading Hi Fi and Home Theatre Brand
Klippel GmbH: Introduction - app notes, technical papers and measurements on speaker distortion
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One thing to bear in mind also, is that an amplifier will typically perform far worse into a real speaker load, then into the purely resistive load that most are tested under.
Granted this is also an aspect of design and an amplifier that's applicable to a given system should never clip, or it's distortion should always remain inaudible over the entire frequency range and under any dynamic situation it will ever be presented with.
This is one area that quite a lot of systems probably fall down under, but then you can always crank it up one step further, no matter how much power you've got. It might be hazardous to your hearing and the loudspeakers, but most people will turn it up beyond unreasonable at least a few times. Is clipping acceptable here? I'd prefer it not to be, but that isn't always possible.
As to Geddes comments on the importance of distortion, lets not forget that he is dealing with drive units and systems that have inherently low non linear distortion. He considers a driver that produces high distortion to be defective and one that should never be used. This doesn't mean that distortion isn't important, rather it is, but it's a factor that is easily controlled, within acceptable limits, on the performance of todays higher quality transducers.
This also doesn't have to cost a fortune, it just requires knowledge in the area and a good idea on how to maximise the performance of a given design.
I agree with him that the interaction of the loudspeakers within the room is the dominating factor with regards to sound quality and it is good to see that a few people are attempting to address this issue.
One thing perhaps to ask is, should an amplifier and loudspeaker really be considered a system as a whole? Or rather should we use a DSP before the amplifier to control the distortion profile of the music played through the loudspeakers?
Going to absolute limits you could design a system that actively introduces distortion within the electronic side of things that attempts to cancel out the distortion produced by the loudspeakers. Doing this would be no small task though.
I do remember planet10 once mentioning that the total distortion of a friends system was in fact lower with the high distortion SET driving the system, then with a low distortion amp. The SETs distortion was cancelling out the distortion produced by the loudspeaker.
Granted this is also an aspect of design and an amplifier that's applicable to a given system should never clip, or it's distortion should always remain inaudible over the entire frequency range and under any dynamic situation it will ever be presented with.
This is one area that quite a lot of systems probably fall down under, but then you can always crank it up one step further, no matter how much power you've got. It might be hazardous to your hearing and the loudspeakers, but most people will turn it up beyond unreasonable at least a few times. Is clipping acceptable here? I'd prefer it not to be, but that isn't always possible.
As to Geddes comments on the importance of distortion, lets not forget that he is dealing with drive units and systems that have inherently low non linear distortion. He considers a driver that produces high distortion to be defective and one that should never be used. This doesn't mean that distortion isn't important, rather it is, but it's a factor that is easily controlled, within acceptable limits, on the performance of todays higher quality transducers.
This also doesn't have to cost a fortune, it just requires knowledge in the area and a good idea on how to maximise the performance of a given design.
I agree with him that the interaction of the loudspeakers within the room is the dominating factor with regards to sound quality and it is good to see that a few people are attempting to address this issue.
One thing perhaps to ask is, should an amplifier and loudspeaker really be considered a system as a whole? Or rather should we use a DSP before the amplifier to control the distortion profile of the music played through the loudspeakers?
Going to absolute limits you could design a system that actively introduces distortion within the electronic side of things that attempts to cancel out the distortion produced by the loudspeakers. Doing this would be no small task though.
I do remember planet10 once mentioning that the total distortion of a friends system was in fact lower with the high distortion SET driving the system, then with a low distortion amp. The SETs distortion was cancelling out the distortion produced by the loudspeaker.
chasing tenths
I've been making fun of amp designers chasing tenths of distortion into resistor loads when speakers are in single digits distortion. Look at the thread on solid state forum on the output capacitor subjective and objective observations. Amps with output capacitors in series with the speaker are totally out of fashion, having a tenth or two of distortion. But such obsolete amps do not torch the speaker winding nearly as often as split supply amps with directly connected transistors that lack expensive SOA measurement circuits and speaker disconnect relays. There are a lot of speaker housings missing drivers, and amps with shiny new output transistors, at the music resale shop. I spent most of my limited pile of money on the speakers, then upgraded a reviled capacitor coupled output amp (seach DJoffe mod) and also bought a reviled "PA" amp that has very carefully thought out SOA (safe operating area) detection, DC crowbar Triac fault circuits, and expensive speaker disconnect relays. Programming a SOA detection circuit is so difficult even one kit builder is ducking the issue and selling microprocessor controlled clipping circuits. (He's australian) Both amps sound pretty good on the SP2 speakers to me compared to the Steinway piano located below & between the speakers.
Before I delve into distortion measurement, I'm looking for a bargain on Neumann or Shope(?) microphones. I would also have to change my computer from Linix back to the mainstream Win*X%s and suffer the viruses like a man.
As far as room effects go, I was delighted when I looked at my house that it has a living/dining room about 16'x10'x30'. I have the speakers on stands high above the piano at the narrow and, and sit on a chair about 20 feet away when I want the best sound. This shape room has been the preferred concert hall shape since at least Mozart's time. When I was in band we played the wedge shaped brick wall Junior High auditoreum, perfectly awful, and the circular Astrodome, so bad only one band in town could play it, us, and only by following visual clues and ignoring our ears. The first step in good home audio is buying or modifying your house.
I've been making fun of amp designers chasing tenths of distortion into resistor loads when speakers are in single digits distortion. Look at the thread on solid state forum on the output capacitor subjective and objective observations. Amps with output capacitors in series with the speaker are totally out of fashion, having a tenth or two of distortion. But such obsolete amps do not torch the speaker winding nearly as often as split supply amps with directly connected transistors that lack expensive SOA measurement circuits and speaker disconnect relays. There are a lot of speaker housings missing drivers, and amps with shiny new output transistors, at the music resale shop. I spent most of my limited pile of money on the speakers, then upgraded a reviled capacitor coupled output amp (seach DJoffe mod) and also bought a reviled "PA" amp that has very carefully thought out SOA (safe operating area) detection, DC crowbar Triac fault circuits, and expensive speaker disconnect relays. Programming a SOA detection circuit is so difficult even one kit builder is ducking the issue and selling microprocessor controlled clipping circuits. (He's australian) Both amps sound pretty good on the SP2 speakers to me compared to the Steinway piano located below & between the speakers.
Before I delve into distortion measurement, I'm looking for a bargain on Neumann or Shope(?) microphones. I would also have to change my computer from Linix back to the mainstream Win*X%s and suffer the viruses like a man.
As far as room effects go, I was delighted when I looked at my house that it has a living/dining room about 16'x10'x30'. I have the speakers on stands high above the piano at the narrow and, and sit on a chair about 20 feet away when I want the best sound. This shape room has been the preferred concert hall shape since at least Mozart's time. When I was in band we played the wedge shaped brick wall Junior High auditoreum, perfectly awful, and the circular Astrodome, so bad only one band in town could play it, us, and only by following visual clues and ignoring our ears. The first step in good home audio is buying or modifying your house.
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I totally agree with you except on one point - what viruses? 😕 I haven't had one in my computer in over 3 years, and i do not run any real-time antivirus, just scans every month. Anyway i'm envious about your room - in mine, the bass is louder outside the room, and my listening position is in a null. Gonna need some serious room treatment after i finish my new subwoofer.
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