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active distortion reduction

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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Topic: active distortion reduction
    Posted: 02 June 2017 at 11:42am
interesting stuff - which professional products are using this approach? my cheap portable PA system seems to use something like this but I'm not sure exactly how it works. quite surprised that it sounds nearly as good as my hi-fi system which cost five times as much.

 http://www.klippel.de/fileadmin/_migrated/content_uploads/ACTIVE_REDUCTION_OF_NONLINEAR_LOUDSPEAKER_DISTORTION_02.pdf
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2017 at 12:49pm
It is a very interesting paper to read, but at the heart of it is feedback. You can implement it with an amplifier to some degree by including the driver as part of the global feedback loop but the Klippel paper is more sophisticated with regards to checking derivatives of motion and using those in the feedback correction too.

The most obvious product that uses a similar technique would probably be the iPal. Anything motor controlled will have similar control loops in it. Servodrive etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote corell Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2017 at 4:32pm
Fulcrum Acoustic has a whitepaper about their THD reducing system available to download on the website. Check it out!
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2017 at 10:50am

What I found interesting about distortion is, the majority prefer music with distortion than without it. If many would accept it for what it is and not get brainwashed into others beliefs that distortion is a problem many would enjoy the composition of the song.

 

Best Regards,

Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2017 at 11:22am
True, though just to add I believe that depends on the nature of the distortion i.e. harmonic distortion might sound pleasant, while IMD or noise might not.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2017 at 8:38pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

What I found interesting about distortion is, the majority prefer music with distortion than without it. If many would accept it for what it is and not get brainwashed into others beliefs that distortion is a problem many would enjoy the composition of the song.

 

Best Regards,



yes it's not all bad. a driver could be designed to distort in a musical way i.e. more 2nd than 3rd harmonic. this requires intentional asymmetry at high excursion.

distortion is also a good indicator that your driver is about to break - dynamic feedback means you can run much closer to the limits of the equipment without damage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2017 at 3:42am

There is definitely a market for those looking to add Harmonic Distortion in the mix.

https://www.youtube.com/watch?v=FbcuH9NAoYU

 

The above video is using the Culture Vulture Super 15 which is a £2700.00 kit. Could you imagine assuming your woofer is the root of the problem while having such a device mixed in the audio tracks you are using as reference?

 

Subtle Total Harmonic Distortion is not frowned upon anymore particularly in the Digital Audio Market. It is a highly desired effect as it offers Analogue characteristics.

 

Only a few Loudspeaker Manufactures are willing to post distortion figures. The majority that do not offer distortion figures knows their loudspeakers distort a lot which, is why they do not offer distortion figures.

 

I am not in any trying to discourage anyone seeking very low distortion loudspeakers. However, if the tracks offer distortion, you may find yourself running around a tree trying to find the bark’s starting point. You know what I mean?

 

Best Regards,   

Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2017 at 7:34am
Of course less distortion is desirable. How else would you ensure that your system plays the music back exactly as the artist/mix engineer/mastering engineer intended?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2017 at 11:49am

Rightfully so! What I am trying to explain is our sound systems can reveal issues that many consumers systems cannot due to the magnitude of its size. There are a large amount of tracks that offer distortion that can lead you astray assuming the speakers are the root of the problem when it is indeed to source.

 

Even as our sound systems progress throughout the decades in sound quality, it allows us to hear the flaws in the tracks that were not as expressive when our older loudspeakers were not as revealing compared to what we use today.

 

Achieving that flawless loudspeaker might reveal so many imperfections in the audio track you may find yourself despising the end results. There is a reason why High End Audiophiles listen to very obscure music.  

 

Best Regards,    

Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2017 at 1:25pm
I think the point on what kind of distortion you are attempting to eliminate is the key.

Most sources, say a violin or guitar or whatever, are far from perfect. Part of their "sound" is the harmonics and reverberations designed in at source. A "well" designed source has "distortion" that is believed to sound desirable to the overall output of the source.

IIRC most "naturally" occurring distortion tends to be odd harmonic. Our brains therefore hear odd harmonics as acceptable, maybe even pleasing. Even order harmonics tend to manifest from artificial sources, so our brains perceive them as unnatural, and therefore unpleasant. 

Consider the old valve stuff. Harmonic central. But many find them highly desirable, versus the "cold" sound of transistors and silicon based noise.

Whilst, in our domain, I acknowledge that what you get out of the system, should be just what you put in with gain, it may be easier to allow pleasant distortions, whilst eradicating unpleasing ones?
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2017 at 5:20pm
Just to chip in here, when I listen to my home music system, I want as close to the original recording as possible which I think I get, I mean a transparrent sound with very little bass, say Eric Clapton live with a nice low double bass, sounds amazing, very little distortion throughout the range.

The P.A. is a different concept, most of the bass is distortion by design, comp drivers are pretty harsh and in general high output systems have inherent characteristics that preclude them from getting anywhere near a top end hi fi in terms of distortion.

In terms of reducing distortion in a system, speaker design is the starting point for me, without a system capable of reproducing what is put in to it, it is bound to disappoint, just my take on it.
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