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Importance of SPL-Response Linearity

ahofer

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I keep looking at these graphs in Erin’s reviews and thinking these measurements deserve more discussion. Doesn’t a lot of difference hear suggest that the speaker’s dynamic response is poor?

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These plots indicate change in frequency response (linearity) with volume and are a reasonable indication of increasing distortion as the volume goes up. It is a family of frequency response linearity plots so not something a single plot would tell you (you need to sweep power over frequency). Most speakers start falling apart in the bass, but some (like the Wharfedale) also exhibit problems at higher frequency when played loudly. The graphs will tell you when a speaker starts to distort heavily ("break up"). Whether it is "poor" depends upon how loudly you listen, but if I liked it loud and clean the KEF is much better than the Wharfedale.

Personally I like seeing these plots, but they can stress (ahem) a speaker so understand why they are not routine. Nobody likes to explain how they destroyed a driver during testing. All the same, some speakers (especially smaller or lower-excursion speakers like bookshelves or panels) get really bad at fairly low levels and it is nice to know that.

FWIWFM - Don
 
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Time is a transform of frequency (with certain constraints), so in theory this doesn't tell us anything that we can't work out from a FR plot.

But many subjectivist reviews talk about "timing" or "rhythm", so I do wonder if there is something we should spot in these plots.

Huh?
 
I keep looking at these graphs in Erin’s reviews and thinking these measurements deserve more discussion. Doesn’t a lot of difference hear suggest that the speaker’s dynamic response is poor?

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These plots show that the Wharfedale compresses significantly at 102dB. That's really loud for most people, I would guess. At 86dB and 96dB, it's pretty good (generally less than 0.5dB compression).

The KEF compresses less at high levels and is outstanding performance.
 
I keep looking at these graphs in Erin’s reviews and thinking these measurements deserve more discussion. Doesn’t a lot of difference hear suggest that the speaker’s dynamic response is poor?

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I've been fascinated by the graphs as well, some small speakers have very odd behaviour around their port tuning, e.g.
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This seems to mainly affect small speakers, unsurprisingly. I'd be interested in the same speaker being tested with its ports plugged, and see if this is badly done ports, or simple displacement limits.
 
Good observation. It looks like that speaker compresses just above port tuning (in the range of about 50 to 90Hz), and it amplifies the output in the range below port tuning (from about 40 to 50Hz). My slightly-educated guess is that the woofer is basically unloaded by the cabinet below port tune and its motion is "overshooting," ie, inertia is making it travel farther than the magnet can contain. Yeah, that's a bunch of hand-wavy analysis because I haven't taken a physics class in over 30 years. :)
 
Indeed, I think these graphs are pretty important, what they can tell you about compression you can't necessarily guess from other charts.

@MaxwellsEq I think you looked too quickly and mistook these for impulse response charts. These show how FR changes depending on how loud the speaker is playing, and whether output level doesn't increase linearly with input.
 
I keep looking at these graphs in Erin’s reviews and thinking these measurements deserve more discussion. Doesn’t a lot of difference hear suggest that the speaker’s dynamic response is poor?

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The graphs hugely amplify the differential. Between 86 and 96 dB, there is less than 0.5 dB change in Wharfdale above 60 Hz! Even at 50 Hz it is just changing 1 dB.
 
I kinda like these graphs. I do think it's helped me get a broad brushtrokes feel for some speakers capability before purchase on more than one occasion E.g. do they go loud across the board or do they run out of woofer too soon for my use case? And in practical terms it's previously helped guide me on where I might need to cross to sub wrt maintaining a certain SPL capability at LF.

The distortion graphs often tell a similar story (and more), but (obviously....) they're not the same thing.
 
I keep looking at these graphs in Erin’s reviews and thinking these measurements deserve more discussion. Doesn’t a lot of difference hear suggest that the speaker’s dynamic response is poor?


I would look at it like this:

  1. Those speakers are better in a smaller room for lower volume listening
  2. Or as Obi Wan would say, “These are not the speakers you’re looking for” … if you want to play them loud.
 
In my limited experience such measurements are more important at active loudspeakers with dynamic limiters which reduce the level of a driver or for example increase the highpass filtering of a woofer.

For lack of audible distortion at high SPL levels I find his multitone measurements more relevant in regards to audibility at all other loudspeakers.
 
@MaxwellsEq[/USER] I think you looked too quickly and mistook these for impulse response charts. These show how FR changes depending on how loud the speaker is playing, and whether output level doesn't increase linearly with input.
Sorry, I was. Had been doing some research on transforms and misread those graphs. :facepalm:
 
The graphs hugely amplify the differential. Between 86 and 96 dB, there is less than 0.5 dB change in Wharfdale above 60 Hz! Even at 50 Hz it is just changing 1 dB.
True. Gotta pay attention to scale.

Is there a reason you don’t perform this type of test?
 
I'll raise the (heretical?) thought that speakers that compress slightly at normal listening levels may sound more laid-back.
 
Interesting thought. However having listened once to tiny passive 2-ways with a 4" woofer played too loud the term "laid back" does not come to my mind, rather its opposite like "stressed".
 
Interesting thought. However having listened once to tiny passive 2-ways with a 4" woofer played too loud the term "laid back" does not come to my mind, rather its opposite like "stressed".
Perhaps there's a happy medium? Or not...
 
Interesting thought. However having listened once to tiny passive 2-ways with a 4" woofer played too loud the term "laid back" does not come to my mind, rather its opposite like "stressed".
In my experience that "stressed" sound is mainly a result of high multitone distortion which often exceeds 10%.
 
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