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Amplifier Power: How much do you really need and your system’s dynamic range.

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My Purifi amp struggles driving my 86dB / 6Ohm speakers while playing large orchestral music. All this since I implemented Dirac Live! Waiting for the 1kW Purifi ...
 

Easternlethal

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My Purifi amp struggles driving my 86dB / 6Ohm speakers while playing large orchestral music. All this since I implemented Dirac Live! Waiting for the 1kW Purifi ...
Woa. What do you mean by "struggles"? I have 8R 91db jbl speakers and was just about to place an order for purifi eigentakt rated 200w into 8 thinking it's more than enough..
 

eddantes

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Am I misunderstanding... I thought room correction software drops the relative output to ensure that any corrective peaks don't clip. I would've thought that before you got clipping, you'd have a complaint about not getting loud enough...
 

solderdude

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It will be higher obviously. What is you point?
I would guess 'average' frequency of music is closer to 1000 than 30 Hz, obviously depending on music. My earlier observations were based on King/I Feel the...., iirc.
My test tone is 31.5 Hz
Perhaps I I'll try it.
I would expect ~0.35 W ?

The point is that music spectrum is mostly bass and if one considers A-weigting @ 30Hz = -40dB.
So... when you are listening to music on average A-weigthed levels low bass is not taken into account.

Would be interested what happens when you use a 30Hz warble tone and set the meter to A weighting set level to 70dBA and measure the output voltage of your amp.
 

solderdude

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Ingenieur

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levimax

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Am I misunderstanding... I thought room correction software drops the relative output to ensure that any corrective peaks don't clip. I would've thought that before you got clipping, you'd have a complaint about not getting loud enough...
The added power requirements of room / speaker DSP are underestimated by most. I think part of it is the "drop the peaks" vs "fill the dips" discussion. While "drop the peaks" instead of "filling the dips" will buy you some headroom in the digital domain once it get to an analog amp there really is not a difference as the "dip frequencies" are going to be boosted relative to all the other frequencies which just takes away headroom. Most room correction software will reduce headroom by 6 to10 dB which translates into a lot of additional power requirements.
 

gonzoucab

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The question remains, should i add more power to the system.

the answer is always yes.
 

Ingenieur

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I wonder what the frequency spectrum of music is? We know it is music dependent. It also takes more power the lower the freq to get equal loudness with higher ones.

Here's one FFT of music found with a quick search. I could not find the name of the music.
 

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Pdxwayne

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I wonder what the frequency spectrum of music is? We know it is music dependent. It also takes more power the lower the freq to get equal loudness with higher ones.

Here's one FFT of music found with a quick search. I could not find the name of the music.
It really is music dependent.

I like music like this:
Spectrum_analysis_65536.PNG.png
 

solderdude

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spectrum.png


A-weighting:
600px-Acoustic_weighting_curves_%281%29.svg.png


Since speakers output SPL which is directly related to the input voltage I prefer not to use the term dBA when talking about power and music.
of course at 1kHz whether the reading is Z-weighting or B or C or D will give the same results.
 

Frgirard

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The spl level perceived is function of the distance, the decay or reverberation, the room volume.

The spl desired - function of the music or sound - could cause distortions by the speakers and the power amp.
The tweeter oscillation can destroy a power amp not enough powerful.
The watt price today is low. There are no reason to do not take advantage.
See the thx rules about the spl level.
 

Ingenieur

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spectrum.png


A-weighting:
600px-Acoustic_weighting_curves_%281%29.svg.png


Since speakers output SPL which is directly related to the input voltage I prefer not to use the term dBA when talking about power and music.
of course at 1kHz whether the reading is Z-weighting or B or C or D will give the same results.
The NIOSH app has C weighting, -3 dB at 30 Hz
 

solderdude

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Looks like pink noise?

Nope. it is just a song I used and analyzed when writing an article (If I am not mistaken 'Keb 'Mo) You are correct that it resembles pink noise and is the reason pink noise exists.
If it were really pink noise the 10dB peaks and dips here and there would not be visible.
 

solderdude

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The NIOSH app has C weighting, -3 dB at 30 Hz

Yep, just use a warble tone (wobble) at 30Hz and use the SPL meter on C and A weighing. There should be a 40dB difference.
 

Ingenieur

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With headphone you can have 8 Hz.
The 2hz is two pressure by second. Nothing to do with a room size.
So the air pressure is oscillated 2/sec or 2 Hz.
Isn't that what a speaker does?
Causes a pressure variation?
What is the wavelength of a 2/sec air pressure variation?
 
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