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Article regarding THD

Andrewjvt

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Jun 18, 2014
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I found this article very interesting and educational.

https://benchmarkmedia.com/blogs/application_notes/interpreting-thd-measurements-think-db-not-percent
 

insider9

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Sep 20, 2016
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From my own acoustic measurements distinguishing an amp from THD figures is near impossible. And that includes valves, older and newer amps, budget and not. Speakers however contribute far more.

The point of % is also very valid as with volume as well as room interaction the percentage varies enormously. Noise floor also comes into play.
 

Andrewjvt

New member
Jun 18, 2014
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insider9 said:
From my own acoustic measurements distinguishing an amp from THD figures is near impossible. And that includes valves, older and newer amps, budget and not. Speakers however contribute far more.

The point of % is also very valid as with volume as well as room interaction the percentage varies enormously. Noise floor also comes into play.
You'd enjoy that
There is loads of really good articles on that site just subscribe they do t bombard you at all
Only now and again
 

insider9

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Sep 20, 2016
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I shall investigate further. I am keen to know how measurements relate to what we hear.

Been into psychoacoustics quite a bit lately. Especially as, I've been trying to perfect the house curve to voice my system the way I enjoy the most. Natural not neutral, if that makes sense. It's fascinating how some speaker manufacturers get his so right we're others fail miserably.
 
Q

QuestForThe13thNote

Guest
It’s all very theoretical and hypothetical and I don’t think you can predict things easily with too many variables, to the extent it’s not worth worrying about this stuff one way or tother in technical debate to the pursuit of good sq. Even if thd should or shouldn’t be a factor in an amp you make decisions on, you take the whole approach to looking at specs and most importantly listening. Things like price too.

im not sure I agree the point about harmonics being masked in the music. As anyway you listen and simply ask yourself does it sound better to me.
 

lpv

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Mar 14, 2013
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it’s a shame they don’t build active speakers based on their own electronics and own design drivers
 

insider9

Well-known member
Sep 20, 2016
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QuestForThe13thNote said:
It’s all very theoretical and hypothetical and I don’t think you can predict things easily with too many variables, to the extent it’s not worth worrying about this stuff one way or tother in technical debate to the pursuit of good sq. Even if thd should or shouldn’t be a factor in an amp you make decisions on, you take the whole approach to looking at specs and most importantly listening. Things like price too.

im not sure I agree the point about harmonics being masked in the music. As anyway you listen and simply ask yourself does it sound better to me. 
The beauty of measurements is that you do not predict or hypothesise. You do however need to be able to read them and understand what it is they describe.

Specs are non other than measurements that manufacturers promises the equipment delivers consistently.
 
Q

QuestForThe13thNote

Guest
The thing is though measurements are arbitrary without it showing or concluding a hypothesis, certainly around thd and whether it’s reliable to use as a basis for an amp being better on sq or not than another with a greater or lower thd measurement. Some people say one way, others the other way. I tend to think it is important as the levels can be markedly different from one amp to another and we are dealing with log scales whether presented as percentage scales or not.

But a scientist coming to views over measurements but not being able to use them with reliability to make conclusions, far from making the measurements have beauty, in fact makes them meaningless to the extent they are used/taken.

Or otherwise some measurement specs can tell us something, so sensitivity of speakers or sound pressure levels for example, which is not non other than measurement, and most would probably agree on the usefulness of such measurements.
 

abacus

Well-known member
Sep 24, 2008
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Frequency response measurements are the easiest to interpret as the effects are well known; they are also used in studio mastering via the use of EQ to get the sound correct.

EQ can achieve virtually everything needed to get the equipment to suit, and when combined with room optimisation can achieve some spectacular results.

Here is a video on room optimisation http://productionadvice.co.uk/using-eq/http://productionadvice.co.uk/using-eq/ which includes what parts of the frequency spectrum causes the affects you hear.

NOTE: These are aimed at professional use but are also relevant to home use. They are also based on facts not hypothetical theories. (So unless you disbelieve scientific facts and physics (Which a lot of Hi Fi Nuts seem to do) this is how things occur in real life)

Bill
 

Vladimir

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Dec 26, 2013
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If you have amplifier with 1% THD+N, that's considered starting of clipping. From that point distortion increases immensly with every extra watt and amplifier passes DC current to the speakers, leading to overheating of the voice coil, rubbing, destruction. Only thing coming out of an amp should be clean AC and nothing else.

If you have clipping up the chain, the amp will amplify the passed DC even more. So it's not a measured figure for audibility as much as indication of equipment safe operating margins so you can do educated system components matching. If manufacturers don't declare the clipping point of 1% on amps just because THD isn't that bad on the ear, they'll be able to state huge amounts of power on very flimsy incompetent amplifiers that will destroy many speakers. And despite regulation they still try to do this, claiming 'musical power', PMPO, hidden 10% THD+N in the fine print etc.
 

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