[jaddie]

Quote:

Yes. A short search resulted in quite cheap bookshelf speakers (less than €80) that have pretty low THD. Unfortunately the y-axis doesn't extend far enough for the 90 dB SPL THD-curve to be visible.
 

Well, one point might be that most speakers aren't listened to at 1m, which means the level of interest would be closer to 100dB than 90, which I admit even if you back off another meter or so,is still pretty loud, but that curve is at 5% at 100Hz.  You would hit the 100dB/1m curve with peaks with "normal" levels at a "normal" listening distance.  Yes, play them lower, they're cleaner.  Kind of what a cartridge does too. I think if we hunt we could find exceptions to anything.  But generally these days the speaker is the highest distortion point in the playback system unless there's vinyl involved.

 

[xnor]

Yeah, but I want to mention some points.
I'd use these speakers or small monitors in the nearfield. So maybe 1.5 to 2m distance.
90 dB SPL is measured already with 1m distance, even if you double that distance (loss about -6 dB iirc) there's still a second speaker (+3 dB -> total of -3 dB).
87 dB is quite loud.
You won't find real music with that much energy in low frequencies as a single full-scale 100 Hz tone. So theoretically THD will be much lower and imho IMD will be a much bigger problem.

 

[jaddie]

Quote:

Yeah, but I want to mention some points.
I'd use these speakers or small monitors in the nearfield. So maybe 1.5 to 2m distance.
90 dB SPL is measured already with 1m distance, even if you double that distance (loss about -6 dB iirc) there's still a second speaker (+3 dB -> total of -3 dB).

Right, but only if the signal is equal in both speakers.
 
Quote:

87 dB is quite loud.

Yes, if that were the average SPL, but most music has a peak to average ratio of 10dB or so.  Average at 76dB SPL is quite common, and that puts peaks at 86dB SPL, and that puts us at over 90dB at 1M per speaker.  Loud-average would be more like 85dB SPL, and that gets you to 101 @ 1m, peak. 
Quote:

You won't find real music with that much energy in low frequencies as a single full-scale 100 Hz tone. So theoretically THD will be much lower and imho IMD will be a much bigger problem.

You find it in movie tracks all the time, the subs usually save the day, but typically cross at 80Hz, so 100 is not a good place for loud peaks. 
 
I agree, IMD is a much bigger problem, much less tolerable.  
 
Let me head off the "THD audibility time" argument in advance.  Yes, you can't hear it if its short in duration.  The entire PPM meter standard is based on the idea of ignoring short duration distortion.  But, the standard Type 1 PPM response to full scale -1dB is 10ms, the period of 100Hz is 10ms, so a few distorted cycles at 100Hz would be audible depending on the degree of distortion, spectrum of the products, duration, etc.  The thing is, the specific SPL at which this can happen, based on peak energy, and normal distances, does fall into the area well above 3% fairly easily.  And, likewise, the peak distortion characteristics of cartridges trying to track vinyl is sort of similar, ignoring specific groove modulation vs SPL calibration of course.  
 
Back into the thread track, sort of, the vinyl system and speakers mush into higher distortion zones potentially during fairly normal conditions, whereas digits actually present less and less distorted signals as levels go up (more bits involved), until the system clips.  
 
BTW, sort of a side not, theres a lot less distortion cut into the groove, they've worked out quite a bit of feedback around cutter heads to linearize them.  That's part of why you can actually cut a clean untrackable groove, as long as it's a low frequency one.  HF levels are limited by the maximum velocity of the stylus along with it's rear faucet. Cut to much at HF and the back facet whacks into the trailing groove wall and ruins it. A lathe is quite a beast, all around. The cartridge is much more limited in THD performance.  And, from this discussion, seems worse than speakers at low volumes, and since we haven't mentioned this quite, cartridge THD happens in the mid band.

 

[xnor]

edit: removed, have to think this through..
 
I don't listen to movie tracks, but would you care to recommend some bass heavy ones?

 

[jaddie]

Bass-heavy movies? Any action flick in the past 20 years, any SciFi, probably even more.  THX "Reference level" is 85dB SPL with 20dB headroom at the listening position, single speaker driven.  Subwoofer channel level has 10dB of gain in it for explosions etc, max is at 115dB SPL (just try to do that at 20Hz!).  All of that is too loud for most people at home, who typically think "home-loud" is about 8dB - 10dB below real reference level.  
 
I do realize the bookshelf speakers won't do that, and aren't intended to.  Cal levels are set with band-limited noise, and the cal point set allows for the 20dB of headroom. 

 

[xnor]

Phono preamp Musica Ibuki (€ 700):
 

SNR for MC/MM is 73/83 dB.
 
AUDIO (german magazine) gave it 100 points for the MC sound quality and 105 points for MM. Overall sound: "excellent".
 
I'm speechless.