Lowering distortion two steps forward and one step back

[Light Dependant Resistor]

Hi
This article is interesting regarding the pursuit of lower and lower harmonic distortion with the question asked that low level resolution has been missed in the process and general comment that it has been two steps forward and one step back. http://www.nutshellhifi.com/library/tinyamps.html

Cheers / Chris

[SPS]

I tend not to comment too much on this sort of thing, as a user of speakers and amps, based on designs that originated in the 30's, my view is crowhirst knew his stuff back in the fifties, but since then hi fi speakers got less efficient but measured better, again tending to exchange accuracy in what is being measured for a less real overall sound and this also effect the amplifiers performance
A good system from the early 50's in crowhirst time would have been a less than 10 watt triode px4? pushpull amp, a very large and efficient speaker, tannoy, lowther or one of the many equivalents and a good quality record player. The fact that that very same kit now commands high prices says alot more than anyone who has not experenced or understands its virtues.
The real trouble is that what is commonly measured not always what effects or spoils the music, What we have today is too many compromises in size, cost and understanding of what the ideal components should look like (in technical terms) to perform.

[fatmarley]

I tend not to comment too much on this sort of thing, as a user of speakers and amps, based on designs that originated in the 30's, my view is crowhirst knew his stuff back in the fifties, but since then hi fi speakers got less efficient but measured better, again tending to exchange accuracy in what is being measured for a less real overall sound and this also effect the amplifiers performance
A good system from the early 50's in crowhirst time would have been a less than 10 watt triode px4? pushpull amp, a very large and efficient speaker, tannoy, lowther or one of the many equivalents and a good quality record player. The fact that that very same kit now commands high prices says alot more than anyone who has not experenced or understands its virtues.
The real trouble is that what is commonly measured not always what effects or spoils the music, What we have today is too many compromises in size, cost and understanding of what the ideal components should look like (in technical terms) to perform.

Good post and pretty much sums up how I feel about the situation.

Surprised this thread hasn't caused more debate.

[Reffc]

I tend not to comment too much on this sort of thing, as a user of speakers and amps, based on designs that originated in the 30's, my view is crowhirst knew his stuff back in the fifties, but since then hi fi speakers got less efficient but measured better, again tending to exchange accuracy in what is being measured for a less real overall sound and this also effect the amplifiers performance
A good system from the early 50's in crowhirst time would have been a less than 10 watt triode px4? pushpull amp, a very large and efficient speaker, tannoy, lowther or one of the many equivalents and a good quality record player. The fact that that very same kit now commands high prices says alot more than anyone who has not experenced or understands its virtues.
The real trouble is that what is commonly measured not always what effects or spoils the music, What we have today is too many compromises in size, cost and understanding of what the ideal components should look like (in technical terms) to perform.

I have a lot of sympathy for those views and can't help but smile as you have hit some fundamental nails on their fundamental heads. The article is useful in flagging up one main point: that THD on it's own is really quite meaningless as an arbiter of sound quality, but what do we expect in an industry with no hard and fast standards where the old measures in context with even order distortion have been taken partially out of context with today's technology?

Whilst equally, for the sake of balance, it has to be said the the pursuit of accuracy is a good one, but not at the expense of everything else; this is partially why so many are returning to kit of yesteryear.

I do take issue with a few points made in that article, the first being the complete nonsense that 44.1/16 bit is somehow "inferior" for decent audio. It's not. fact. Like everything else, the secret behind a really good sounding 44.1/16 bit recording is in the mastering, something which used to matter a lot, especially with classical and Jazz/Blues recordings, but less so with much of today's manufactured and highly compressed music. Not that pre 1980's vinyl was all sweetness and light, as truth be told, there were as many shockers out there recordings-wise as there are now. The other thing that people need to bear in mind is that whilst technology marches on and higher and higher resolution files become available, there is a limit to what human hearing can discern and Red Book done properly is about as good, basically, as it needs to get.

The thing that I find goes against the grain with many of today's systems have less to do with whether they hark back to golden olden times or not, but why so many are still so darned inefficient. To look into this, we come back to that bugbear of the author, which is accuracy. There are various technical camps, none claiming that they are right and everyone else is wrong, just different ways of doing things. The so-called high end seems by and large to favour inefficient speaker design due to the complexities of achieving accurate (phase and frequency response) sound reproduction with vanishingly low harmonic/phase distortion at the expense of power, because power is cheap (relatively speaking). Whilst there are sort of sound reasons for claiming this, it does tend to throw up systems that all sound rather too clinical for my tastes, perhaps as so few can do the dynamics thing well (if at all) at lower listening volumes, unlike so many more efficient systems.

You can achieve perfectly respectable accuracy with far more efficient systems not needing all this power, so yes, it would be good to see far more sensitive speaker designs and affordable well designed valve amps that don't make your ears bleed if they are pushed a bit hard. Trouble is, the author has failed to grasp that it isn't necessarily technological developments for the sake of them which have led us to where we are today but things like WAF, ever smaller listening spaces and fashion dictating smaller and more compact speaker designs meaning a loss in efficiency and a need for greater power (which after all IS cheap relatively speaking). Companies continue to churn out bling boxes year after year, competing for the technology-for-the-sake-of-it market and what wins WAF in most homes. Whilst that in itself is NO guarantee of advancement, it is easily achievable to claim things like low THD. That might fool some of us, but savvy buyers will I think remain savvy. The question then is "is true hifi enthusiasm gone underground" and been replaced with mass market appeal? I think so.

There is also a distinction to be made about what is good (forgive the term) "high end" hifi, and just expensive jewellery designed to part the gullible from their easy/hard earned fortunes. Probably more so these days due to choice and ever more sophisticated marketing than there ever was. One thing is for sure. It's getting harder to recognise what might be landmark developments today and what are just over hyped marketing claims.

[Macca]

Good post that Paul. Interesting piece that seems to have it right in some respects and wildly wrong in others. It didn't take 20 years to improve cd players as a listen to my 1989 Technics SLP1200 Broadcast would tell you (if it was still working...). Nor is anything 'lost' in a 16/44.1 bit recording. So 5 out of ten from me :)

[SPS]

Surprised this thread hasn't caused more debate.

Me too, but there again it could be close to high efficiency vs low efficiency speakers... or valves vs solid state debates, so it probably best where it is...
Cheers..

[Light Dependant Resistor]

The article refers to a paper that in part can be read on Google titled Rethinking distortion: Towards a theory of 'sonic signatures' Bernd Gottinger PhD Dissertation New York University 471 (2007)

here is the google link http://books.google.co.nz/books?id=G3vkSkvTf-cC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

The common theme is that higher order distortion figures is absent from present THD measurements, and that THD then becomes less meaningful, bordering on misleading as a measure of equipment pecking order where these figures are absent. The partial article is great reading. Appears the full paper currently is unavailable but hopefully will be published again.

Cheers / Chris

[Reffc]

The article refers to a paper that in part can be read on Google titled Rethinking distortion: Towards a theory of 'sonic signatures' Bernd Gottinger PhD Dissertation New York University 471 (2007)

here is the google link http://books.google.co.nz/books?id=G3vkSkvTf-cC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

The common theme is that higher order distortion figures is absent from present THD measurements, and that THD then becomes less meaningful, bordering on misleading as a measure of equipment pecking order where these figures are absent. The partial article is great reading. Appears the full paper currently is unavailable but hopefully will be published again.

Cheers / Chris

Good stuff although the OP article linked was full of flaws.

[awkwardbydesign]

I think one problem with claiming distortion isn't (or is!) audible is the assumption that all hearing is equal. I know mine isn't.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Image_zpsbdd271e1.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Image_zpsbdd271e1.jpg.html)

[SPS]

Thats the flaw, its actually. not about hearing distortion, we all actually hear it unless one has an impairment, its about recognising it ...which is a very different thing

A good set of measurements may have been only be a good thing with regard to protecting the kit from those who may just know what to listen for?

I think the real issue is is what is measured, and the point was in the 50's some may well have thought it was possibly the wrong thing, or at least that they do not give the full picture ?

[awkwardbydesign]

Thats the flaw, its actually. not about hearing distortion, we all actually hear it unless one has an impairment, its about recognising it ...which is a very different thing


My point was, I think you are mistaken. We DON'T all hear it. My family, and others, simply CANNOT HEAR some of the things that I can. Maybe MY hearing is flawed, certainly my left and right ears are different, but the assumption that "we all actually hear it" is factually incorrect. We don't! I know this idea is offensive to many, but I don't understand why. After all, it is accepted that some can see better than others, or taste too, but differences in hearing ability seems to get some people riled. Odd.

[awkwardbydesign]

Interestingly (to me!), when I worked in one noisy workshop, I couldn't hear the internal phone. It made a low pitched "meep, meep" sound, and it was swamped, for me, by all the higher frequencies I could hear but the others couldn't. If I wore earplugs I could hear it!

[SPS]

My point was, I think you are mistaken. We DON'T all hear it. My family, and others, simply CANNOT HEAR some of the things that I can. Maybe MY hearing is flawed, certainly my left and right ears are different, but the assumption that "we all actually hear it" is factually incorrect. We don't! I know this idea is offensive to many, but I don't understand why. After all, it is accepted that some can see better than others, or taste too, but differences in hearing ability seems to get some people riled. Odd.
I think we will have to agree to disagree on this one, i've known so many occasions at hifi shows and meets when poeple say they can not hear some distortion, then once its pointed out where to listen for it, they then can, this is how I learnt to 'listen' unfortunately its a skill that usually has been learnt in my view.

[Macca]

Very true had a friend around the other day who is a professional sound engineer. he remarked how good the sound quality was. I said to him 'You don't think it is a bit muddy?'
He listened for another 5 minutes and then said 'yes it is a little bit muddy I see what you mean now'.

[awkwardbydesign]

I think we will have to agree to disagree on this one, i've known so many occasions at hifi shows and meets when poeple say they can not hear some distortion, then once its pointed out where to listen for it, they then can, this is how I learnt to 'listen' unfortunately its a skill that usually has been learnt in my view.
I am not denying that we can learn to become aware of sounds we didn't notice before. I do it myself, but that is not the same as measurable differences in hearing response. So how are we going to "agree to disagree"?
My hearing is measurably different from my wife's. At 8kHz (the limit of the test) my hearing was rising, not dropping, which actually explains why certain things bother me more than other people. This test was very basic, with no pretense at great accuracy, but the RELATIVE differences are clear to see. Or are you saying this test is meaningless? Unless the volume of certain frequencies are raised considerably, she simply cannot hear them. Even putting her ear to the offending noise source she CANNOT HEAR IT! Sorry to capitalise, but there are differences in abilities, no matter how much you dislike the idea.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Image_zps9a4b7bc8.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Image_zps9a4b7bc8.jpg.html)
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Image_zpsbdd271e1.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Image_zpsbdd271e1.jpg.html)

[SPS]

Richard i was taking about hearing distortion, i would class that as different to some of the frequencies you hear being louder or quieter?
Im in the same position, my hearing is not perfect i just need a little more volume to compensate, not good, but its my age...

[awkwardbydesign]

Well, I can hear HF distortion, sibilance for example, that others around me can't, even if it is pointed out to them. So, what would appear to them as clean and undistorted, appears to me as distorted. On those 2 tests, my wife's hearing at 8kHz is 60dB down on mine. 60dB! To her the distortion is below the threshold of hearing, while to me it is extremely irritating. Nothing to do with focus, just physical hearing difference. I used to hate the colour TV line whistle, 15-16kHz. She and her sister simply couldn't hear it.
Possibly why I prefer valves to SS, class A to class A/B. Higher order harmonics will be more audible to me.

[fatmarley]

I always assumed that peoples hearing was pretty much the same but as you got older the higher frequencies became harder to hear. I never knew that people hear certain frequencies louder than others - interesting...

[awkwardbydesign]

I have searched my "archives" and found this- http://www.vinylengine.com/turntable_forum/viewtopic.php?t=39071 I would recommend it to anyone who has an open mind.
It is a thread/blog that rings so true for me. Now I don't claim to have Golden Ears, or anything like, just that my hearing is not the same as yours. Nor is yours the same as anyone else's! Ted Jordan, a great designer and one of the fathers of speaker design, 20 years ago couldn't hear that one of his tweeters was dead. I heard it as soon as I walked into the room, he had to put his ear to each speaker to tell the difference. This isn't bragging, he could probably hear other things that I couldn't, but at those frequencies my ears picked out sounds (or lack of) that he couldn't.
Assuming that we all hear the same is fair enough, after all that is what we are led to believe. But why? Sight, taste, smell, we all accept variations in ability (I could never be a wine expert, or perfumier, or tea taster), but mention differences in hearing to hifi enthusiasts and wait for the explosion. Bizarre!
I did the colour blindness test as part of my training to be a telephone engineer ( I passed the test, but failed at the job!), and the differences are accepted as normal. So why the frothing at the mouth over hearing differences?
I used a signal generator recently to find resonances in a room, and was horrified to find I could only hear 12kHz while a friend could hear 14 kHz! The speakers may have limited HF (I hope) and I am sure my hearing HAS deteriorated, but my point is still valid.

[awkwardbydesign]

BTW, Matt, the biggest problem I am having with my Troels Gravesen Jenzens is the treble. Changing speaker cables made a big difference, but there is still something not quite right. I suspect this is why I have weakness for ribbons, planars, and electrostatics; they don't have that dome tweeter resonance.

[Ali Tait]

Yep, used to have the same problem with high frequency noise from tv's. I could even hear an "ultrasonic" anti rodent deterrent that a neighbour bought once. Drove me nuts. Luckily we were on good terms and he stopped using it, or I would have had to move!

[fatmarley]

BTW, Matt, the biggest problem I am having with my Troels Gravesen Jenzens is the treble. Changing speaker cables made a big difference, but there is still something not quite right. I suspect this is why I have weakness for ribbons, planars, and electrostatics; they don't have that dome tweeter resonance.

It's a shame you're not into crossover design because you could tune the speakers to suite your ears. If you could play around with a graphic equalizer until you find the problem frequency, you could try contacting Troels to see if he could help you adjust the crossover.

[fatmarley]

Yep, used to have the same problem with high frequency noise from tv's. I could even hear an "ultrasonic" anti rodent deterrent that a neighbour bought once. Drove me nuts. Luckily we were on good terms and he stopped using it, or I would have had to move!

I bought one of these - LINK (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230989500237) - to stop the cats crapping at the bottom of the garden. I can hear it on every setting but my girlfriend can't hear it at all.

The cats obviously can't hear it either :(

[awkwardbydesign]

I bought one of these - LINK (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230989500237) - to stop the cats crapping at the bottom of the garden. I can hear it on every setting but my girlfriend can't hear it at all.

The cats obviously can't hear it either :(
But did it stop YOU crapping at the bottom of the garden?

[SPS]

BTW, Matt, the biggest problem I am having with my Troels Gravesen Jenzens is the treble. Changing speaker cables made a big difference, but there is still something not quite right. I suspect this is why I have weakness for ribbons, planars, and electrostatics; they don't have that dome tweeter resonance.

I know exactly what you mean, rough treble can be down to the speaker and / or the amps, i would guess capacitance in the cables will work like a tone control on the top end, but not remove the cause
I would say you have a weakness for good quality speakers.. When you have lived with clean speakers its hard not to recognise what other speakers may impart on the sound

[anthonyTD]

Higher order distortion IMHO Is a common concern when using solid state equipment, even in smal amounts, which again IMHO is one of the reasons some manufacturers strive to acheive and publish the lowest posible THD figures, it can however be difficult to establish what the real issues are in a system that has an agresive treble, or higher mid range frequency agrevation, some of the time it is down to the limitations of frequency response in either source, preamp, or power amp.
A...

[Reffc]

I know exactly what you mean, rough treble can be down to the speaker and / or the amps, i would guess capacitance in the cables will work like a tone control on the top end, but not remove the cause
I would say you have a weakness for good quality speakers.. When you have lived with clean speakers its hard not to recognise what other speakers may impart on the sound

If there is dome tweeter resonance, then the tweeter is faulty/not much good, OR there's an issue with source or crossover design.

I have designed and built plenty of speakers using dome tweeters and generally speaking, most modern quality dome units are well damped unless run too low where rising impedance towards self resonance also equates to rising distortion which in a 2 way especially leads to distortion in the summed response, which is very audible. If the crossover is properly designed and the (quality dome) tweeter not run too low, then there should be no audible HF distortion (usually it is recommended to run a tweeter two octaves above resonance but you can introduce LCR filters to quash impedance at resonance hence lowering output and distortion). It's horses for courses, and one cannot really generalise about dome tweeters. It's all down to design and implementation. I usually select dome tweeters for a nice flat response, with no obvious spikes in response and there's a huge choice out there of excellent candidates from as little as £25 a pop these days.

Ribbon cannot be run as low, and have their issues too (their off axis response doesn't equal the best dome tweeters for example, and this is for me a problem unless they are crossed over quite high up....say in a 3 way system).

[fatmarley]

But did it stop YOU crapping at the bottom of the garden?

It stops me wanting to mow it, that's for sure.

[awkwardbydesign]

If there is dome tweeter resonance, then the tweeter is faulty/not much good, OR there's an issue with source or crossover design.

I have designed and built plenty of speakers using dome tweeters and generally speaking, most modern quality dome units are well damped unless run too low where rising impedance towards self resonance also equates to rising distortion which in a 2 way especially leads to distortion in the summed response, which is very audible. If the crossover is properly designed and the (quality dome) tweeter not run too low, then there should be no audible HF distortion (usually it is recommended to run a tweeter two octaves above resonance but you can introduce LCR filters to quash impedance at resonance hence lowering output and distortion). It's horses for courses, and one cannot really generalise about dome tweeters. It's all down to design and implementation. I usually select dome tweeters for a nice flat response, with no obvious spikes in response and there's a huge choice out there of excellent candidates from as little as £25 a pop these days.

Ribbon cannot be run as low, and have their issues too (their off axis response doesn't equal the best dome tweeters for example, and this is for me a problem unless they are crossed over quite high up....say in a 3 way system).
I've highlighted these points mainly because they may point towards my particular sensitivity. And I am only guessing at the reasons for my preferences. Whatever the reasons, I definitely get on better with other types of tweeter. and I am not referring to the low frequency resonance anyway, more the breakup at higher frequencies.
I have just come from a 3 way active system, with no passive filters, to squash resonance or otherwise. I suspect the overuse of filters is part of my problem.

[Reffc]

Filters are there for a reason...to lower distortion and flatten response/impedance. Adding a resonance filter (L-C-R) is not an over-use of filters in any speaker designer's arsenal where it is necessary, besides which it does not lie within the signal path so cannot be "heard" or otherwise. I agree that there can be mis-use or poor design but that is a different thing entirely. I do my fair share of crossover rebuilds and measuring speaker response never cease to be amazed at just how badly designed many filters are. Good one's are however, worth their weight in pure gold. It just rings alarm bells with me when I hear generalisations, but yes, phrased differently I can understand a preference for a specific driver.

[SLS]

Well, I'm using a 20w 300B-XLS amplifier. I was using some 89dB PMC speakers and was looking at something a little more sensitive, and now have Harbeth SHL5+ rated at 86dB and 6 ohms nominal impedance. It's not meant to work, but it does.

[Reffc]

Well, I'm using a 20w 300B-XLS amplifier. I was using some 89dB PMC speakers and was looking at something a little more sensitive, and now have Harbeth SHL5+ rated at 86dB and 6 ohms nominal impedance. It's not meant to work, but it does.

It will work but your absolute SPL and therefore dynamic range will be limited by the limitation in wattage. You can run any 20W amp into distortion and not notice much except the warmish lower even order distortion creeping in. I used to be the owner of SHL5's and ran them with Croft amplification which was more than enough. I believe that they (the speakers) were voiced for around 85W programme.