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Old 15th March 2004, 06:19 AM   #1
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Default sound reproduction and distortion

have a look here: http://www.linkwitzlab.com/reproduction.htm

and scroll down to the distortion section.

Amplitude response is given higher priority than freq response but arent they roughly the same?


Here is a graph: http://www.seas.no/kit/Trym%20måling.pdf

There are relatively large bumps in the crucial 200Hz - 1Khz section. Some people at Madisound say that smoothing out these bumps wouldnt make any real improvement. However the graph of the Thor, for example, is much flatter in the same region. Correct me if im wrong but I would think they are large enough that judges would tell the difference in a speaker competition.

Isnt a really flat response one of the most important things in acheiving better sound quality; I would want to smooth out these dumps and get the most out of these horribly expensive drivers, or do you think I would be wasting my time doing so? if so why?
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Old 15th March 2004, 06:27 AM   #2
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Amnlitude response or freq response are generally speaking used for the same graph: amplitude versus freq. And yes, those bumbs are Not Good. But Linkwitz didn't say amplitude response, he said non-linear amplitude response. Meaning that an increase in say 10dB of input level doesn't cause the same 10dB in sound level: the graph of input amplitude versus sound level is non-linear. That leads as he says to compression, IM etc.

Jan Didden
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Old 15th March 2004, 08:28 AM   #3
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I don't know how wise it is for Linkwitz to rank various negative effects on sound-reproduction in order of importance, when their importance might be different for different people and vary with different situations. Here's a different list of negative influences on sound-quality in MY order of importance:

1)Resonances and interferences in the reproduced sound - eg, overshoot and ringing of a reference signal such as a step or impulse, across a wide range of audible frequencies. Box colourations, diffraction effects, comb-filtering etc.

2)Smoothed frequency response curves - eg: is the sound bass-heavy, bright, thin, etc?

3)Classic Distortion - eg: THD, both types of IMD.

4)Resonances and reflections after the sound is reproduced - room resonances and echoes.

5)Smoothed phase response curves - eg: is the bass delayed by filtering and mechanical design (including ports), etc?

Obviously each effect may vary in importance depending on the particular set-up. If some music is played in a stone dungeon with a 5W transistor amplifier saturating almost half of the time, obviously a few subtle box colourations aren't the biggest problem.

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Old 15th March 2004, 09:40 AM   #4
sreten is offline sreten  United Kingdom
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Linkwitz's weighting of factors is specifically for use in small open
baffles, where larger than normal excursion requirements apply.

sreten.
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Old 15th March 2004, 06:09 PM   #5
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Quote:
And yes, those bumbs are Not Good
is it possible to filter out those bumps by modifying the passive crossover, or is active equalization the only way?
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Old 15th March 2004, 07:15 PM   #6
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Quote:
Originally posted by CeramicMan
I don't know how wise it is for Linkwitz to rank various negative effects on sound-reproduction in order of importance, when their importance might be different for different people and vary with different situations. Here's a different list of negative influences on sound-quality in MY order of importance:
[snip]
Obviously each effect may vary in importance depending on the particular set-up. If some music is played in a stone dungeon with a 5W transistor amplifier saturating almost half of the time, obviously a few subtle box colourations aren't the biggest problem.

CeramicMan
?? So you DO agree with SL that compression is more objectionable then some ringing (which you would have a hard time to hear anyway)?

Jan Didden
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Old 15th March 2004, 08:58 PM   #7
Bose(o) is offline Bose(o)  Canada
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If one could, one may rank all problems with reproducing sound from a loudspeaker as the same in importance. I like to think of a problem as one link in the chain, if you compromise everything about say, resonances, then you break the chain and thus results inferior sound quality.

Anyway, you have to determine which links you will not need to have completely though, still have enough to complete the chain. If not, then you will not be engineering and nor will you ever finish. The Perfect Loudspeaker is an oxymoron.
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Old 15th March 2004, 09:20 PM   #8
Volenti is offline Volenti  Australia
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Quote:
Originally posted by tech.knockout


is it possible to filter out those bumps by modifying the passive crossover, or is active equalization the only way?
bumps can be passively EQ'd out.
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Old 15th March 2004, 09:42 PM   #9
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Quote:
Amplitude response is given higher priority than freq response but arent they roughly the same?
The freq. resp. is always shown at one amplitude level. For those to be the same there is one dimension missing. We would need a frequency response for all amplitudes what makes it a 3D and not a 2D graph.

The frequency response is the main point of interest of most people, and all Hifi marketing people. But who tells you a frequency response perfectly flat at 1W is also flat at 100W input power to your speaker? And music surely consists out of different frequencys, but are they always same SPL? If i listen to an orchestra the room is also not really flat in frequency response. My ear is not really sensitiv to this, the build in DSP in my head manages to deal with differend frequency responses. But the orchestra plays also somtimes very silent and sometimes very loud. This effect is very impressive - with an real world orchestra which has much more dynamik range than our reproduktion systems. How impressiv it is from your speakers depend much more on the amplitude response than on frequency response - i suspect.

But as most people this days don´t listen to orchestras but to some red hot chili peppers compressed to 6dB dynamik range car radio music - amplitude response of corse is not of interest anymore.
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Old 15th March 2004, 11:31 PM   #10
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Quote:
Originally posted by janneman


?? So you DO agree with SL that compression is more objectionable then some ringing (which you would have a hard time to hear anyway)?

Jan Didden
Well, compression isn't a very accurate way of describing some types of nonlinearities anyway, plus it depends on the amount. What I described was some pretty severe distortion in a really bad listening environment. In a more ordinary situation, even though some resonance effects may not be audible, they can still be a big cause of listening fatigue.

IMO the ripples on the graph of the Seas kit are largely caused by box resonances. If those sorts of resonances were hard to hear then people wouldn't be so fond of open-baffled speakers.

CM
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