Interpreting THD + N graph for speakers

[KEW]

These are Soundstage measurements for Energy RC-10:

Top curve: frequency response @ 90dB SPL
Bottom curve: THD+N @ 90dB (50Hz - 10kHz)

I know speakers don't come close to the 0.02% THD of electronics, but this looks pretty dire!

Is there a good way to convert 75dB for 95dB signal into % distortion?

Is that likely to be audible?

I have these speakers and while they are not the cleanest, I have not been especially offended by them and considered them a deal when they were selling between $200 and $300/pair!

Here is the same graph for the Paradigm S2 (signature series)

 

[Steve81]

Is there a good way to convert 75dB for 95dB signal into % distortion?
........
Is that likely to be audible?

I have these speakers and while they are not the cleanest, I have not been especially offended by them and considered them a deal when they were selling between $200 and $300/pair!

http://www.soundstagenetwork.com/measurements/test_loudspeakers.htm

Chart 3 - Total Harmonic Distortion + Noise (THD + N)

• THD+N variation with frequency at 90dB - Measured at 2 meters (equivalent to 96dB at 1 meter) from 50Hz to 10kHz. The top curve of the chart shows the frequency response of the loudspeaker at the determined SPL level (i.e., 90dB) while the bottom curve shows the distortion component of the signal (values below 40dB should be ignored because they are too close to the noise floor of the test equipment to be of use).
  
  Both curves are reported in dB which can be read off the vertical axis. In order to convert to a percentage one must read the top line (frequency response) and then determine the dB difference between that line and the bottom line (THD+N line). Translation from dB to % is as follows:
  
  Equal (or 0dB difference) = 100 %
  -10dB = 31.6%
  -20dB = 10.0%
  -30dB = 3.16%
  -40dB = 1.0%
  -50dB = <0.5%
  
  Please note: an SPL level of 90dB measured anechoically is very loud and considered far beyond normal listening levels, particularly for small loudspeakers. To give more information for real-world listening levels, if it appears that the speaker is being strained beyond its output abilities at this level we will provide a second measurement at at lower SPL (the SPL level will be printed with the chart).
  
  Purpose: Measures THD+N output at discrete frequency intervals for above-normal listening levels. Please note that 90dB output at a 2-meter distance is equivalent to an SPL level of 96dB at a 1-meter distance.
  
  What it tells you: Audibility of distortion varies as to type of distortion and also the frequency at which it is occurring. Distortion measurements for loudspeakers are usually many times that of electronics (i.e., amplifiers, receivers, etc.). Furthermore, certain types of distortions are more audible than others and the audibility of that also depends on the frequency. Our distortion measurements give a general indication of how much distortion is occurring for a given output level at above normal listening levels. Distortion levels will be less (sometimes much less if the speaker is being stressed beyond capabilities at 90dB) at lower SPLs.

TLDR: The single graph doesn't really tell us much as there's not enough data (distortion breakdown, distortion at different drive levels, etc.) to say anything beyond whether or not the DUT is obviously straining at the given playback level.

 

[Irvrobinson]

The distance between the graph lines at any given frequency is the amount in decibels that the distortion is below the signal. So in the first chart at 1KHz, the distortion is -45db from the fundamental, or about 0.6%. At 800Hz it looks to be more like -35db, which is about 1.78%.

What was your measuring distance?

 

[Verdinut]

Normally, a loudspeaker does not generate noise. It will if it is badly overdriven beyond its xmax with real possibility of damage and even burning of the voice coil.
Usually, if there is a noise coming out of a speaker, it is generated by the source signal, such as a defective amplifier or sound processor, or simply a cable.

I read the info for the Chart 3 (THD + N). This is rather misleading as the noise part does not generate from the speaker but totally from the test equipment noise floor.

 

[Beave]

The distance between the graph lines at any given frequency is the amount in decibels that the distortion is below the signal. So in the first chart at 1KHz, the distortion is -45db from the fundamental, or about 0.6%. At 800Hz it looks to be more like -35db, which is about 1.78%.

What was your measuring distance?

Are your numbers off by 10dB or am I making a mistake and misreading the graph for the RC-10?

I see a difference of 35dB at 1kHz and 25dB at 800Hz.

 

[TheWarrior]

From our subjective review that speaker had difficulty keeping complex orchestral music on a balanced sound stage. Although my writing tried to keep a positive tone, that speaker was not able to emit the sounds of many instruments or voices simultaneously, essentially 'choosing' one over the other. Many of those sounds would fall under the frequency range in question.

That said, considering a pair of active JBL LSR305's are the same price, the difference in performance is enormous! Given your other listening options, I would not give a second thought to offloading the RC10...

 

[Irvrobinson]

Are your numbers off by 10dB or am I making a mistake and misreading the graph for the RC-10?

I see a difference of 35dB at 1kHz and 25dB at 800Hz.

You're correct. I was working on my laptop system and make a mistake. -35db is 1.8% distortion and -25db is 5.62%.

 

[KEW]

From our subjective review that speaker had difficulty keeping complex orchestral music on a balanced sound stage. Although my writing tried to keep a positive tone, that speaker was not able to emit the sounds of many instruments or voices simultaneously, essentially 'choosing' one over the other. Many of those sounds would fall under the frequency range in question.

That said, considering a pair of active JBL LSR305's are the same price, the difference in performance is enormous! Given your other listening options, I would not give a second thought to offloading the RC10...

This thread is about understanding the measurement/graph and it's interpretation, especially in the context of the more familiar % distortion.
I'm not looking at getting rid of the RC-10's (though I have little reason to keep them). I wanted to check their efficiency (for testing the Monolith for shipping damage) and came across this chart.

They are not a bad speaker for a bedroom or office, but they are pretty small for a living room.
Though Philharmonic AA's or Sony CS5 handily beat them in today's market.

 

[TheWarrior]

This thread is about understanding the measurement/graph and it's interpretation, especially in the context of the more familiar % distortion.
I'm not looking at getting rid of the RC-10's (though I have little reason to keep them). I wanted to check their efficiency (for testing the Monolith for shipping damage) and came across this chart.

They are not a bad speaker for a bedroom or office, but they are pretty small for a living room.
Though Philharmonic AA's or Sony CS5 handily beat them in today's market.

"Many of those sounds would fall under the frequency range in question." - as it pertains to the measured distortion. It's all in the mid range where we had difficulty hearing multiple instruments simultaneously. I would call that distortion.