# Need Understanding



## Audiodreamer (Jan 11, 2009)

Hello all! To a degree I understand speaker sensitivity. I have plans to build one of the proven designs from Speaker Design Works. What really interest me is the statements II. I also like the sentorians. If anyone has any input on either of these, I would be interested in hearing. Primarily for music purposes, however much or little. I am sure it will please for home theater also.

Now to the real point. Look at measurements on a given speaker, I see......system harmonic distortion. "This is with1/48 octave smoothing and was measured at approximately 96db/1 meter. Note the HD through the midrange region is about 0.1% at this level, while the ribbon was slightly higher, but still very acceptable at 0.3%"

What does this mean to me?

Thanks


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## fusseli (May 1, 2007)

The Statements have always been popular although I don't know much about the IIs.

That just means they had 96 dB of SPL 1m away from the speaker during the test, in which either driver had 0.1% or 0.3% THD. Either figure is very good and would be essentially inaudible, meaning 0.1% of the 96 dB sound was distortion caused by the driver. That would mean the distortion is -50 dB to -60 dB down from the fundamental sound the speaker is meaning to play.


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## Audiodreamer (Jan 11, 2009)

fusseli;974761/ said:


> That would mean the distortion is -50 dB to -60 dB down from the fundamental sound the speaker is meaning to play.


is this minus 50 and 60? If so how did you come up with these numbers? That seems like a big drop from 96 to 50.



I only ask, because because I had not seen anything about distortion on my current speakers, or many others. however I have not looked at specs on 1000's of speakers either.


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## fusseli (May 1, 2007)

Audiodreamer said:


> is this minus 50 and 60? If so how did you come up with these numbers? That seems like a big drop from 96 to 50.
> 
> 
> 
> I only ask, because because I had not seen anything about distortion on my current speakers, or many others. however I have not looked at specs on 1000's of speakers either.


For THD figures it's simple, you just convert the percentage to dB using 20*log10(THD%). And yes, those would be "minus" dB relative to the fundamental signal being played. For the 96 dB SPL @ 1m output this would mean the ribbon was putting out distortion at 46 dB SPL at the same time.


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