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Digital harshness or Clipping?

Category: Amplifiers

My good friend, who is largely responsible for getting me hooked on this hobby over twenty years ago, stopped by my studio yesterday for listen. My SET system is now there at work instead of at home as it indicates in my virtual system. We've both been addicts for twenty years and listen to a lot of different music. We always have a fun time introducing each other to new stuff. One of my recent favorites on frequent rotation, that I've brought up on another thread here, is an early music recording Jordi Savall's excellent label, AllaVox. The CD is, "El Cant de la Sibil-La" (Alla Vox AV9806), with his wife Montserrat Figueras, who has a remarkable soprano voice. I put this one on after we'd been listening for a while and my friend was very impressed with the system. I was curious to see what he'd say about this recording as I had my own theories. Of course, he noticed it right away: When the soprano hits the highest highs of those upper registers, there is a "brittleness" to the sound, almost a kind of breaking up of the otherwise remarkable smoothness of her voice. I have a few Alla Vox recordings and they are astounding in quality. So I'd thought it was more likely something other than that. I'd thought, because I'd brought my 8 watt amps and 115db efficiency speaker into a much larger space that it actually had them clipping at that point (yes, we were listening at a substantial volume (I'm guessing 90+ db in the listening position). The room is over 1000 sq feet in the wood loft of a horse barn with 12 foot ceilings. My friend Jon, who is a big fan of vinyl, thought instead that it was the digitits rearing it's ugly head. My front end at work is pretty darn good, a Naim CD5 with HiCap. The rest of the system is as my virtual system indicates, though speaker wires are now Au24's. When I take the CD home and play it on the system there (35 watts of push/pull into 90db floorstanders in a small room), at higher volumes I can hear the same thing albeit a bit more 'rounded' off. There my front end is a Muse Model 5 & Model 2-Plus DAC so also pretty good. The breaking up is much less apparent when the volume is down to more reasonable levels.

So my question is; do you guys think this is clipping beginning to happen at the higher volumes, or is it an artifact of digital reproduction amplified to bring out the worst at an extreme given the louder volume?

Someone recently posted the great suggestion of a "Questions for Sean" section.....This is just the kind of question I'd like to get your input on Sean, as well as others of course!

Best,

Marco

PS Should anyone have this same recording I'd be curious to hear if they encounter a similar effect. There are two versions I've found of this one with the same performers, and this is the one an Alla Vox and is a much better recording and performance, IMO, than the other.
jax2

Showing 3 responses by sean

sean
6,231 posts
 
There was a recent article i read about this phenomena. According to recent studies, the human voice / speech reproduction system distorts as both amplitude and frequency climb. As such, many of the singers that can hit very high notes actually have a natural distortion / "brittleness" to their voice. The logical deduction here is that what you are hearing could be part of the recording or her natural voice being pushed to the limits.

As far as clipping goes, do you hear this phenomena at lesser volumes? If not, then it is stricly the recording or her voice. Sean
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sean
6,231 posts
 
I agree. It could be distortion of the recording equipment i.e. mic overload, clipping of the input stage, etc... The end result would be that it ended up on the recording and is not related to Marco's system giving out. When it comes to this type of situation and distortion, it is either the recording or the equipment. How the distortion ends up in the recording could be anyone's guess as there are many ways that it can occur. Sean
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sean
6,231 posts
 
Marco: It is not abnormal for the frequency response of a system ( especially speakers ) to change as volume is varied. As such, you could simply be "highlighting" a flaw in the recording and / or demonstrating system non-linearities. My guess is that you might be experiencing a little bit of both.

As a side note, you REALLY have to watch how speakers are rated and measured, especially in reviews. By measuring a speaker at a lower volume, it is possible to produce a flatter i.e. "better looking" response curve.

I just stumbled across a review a while back where the baseline frequency response reading for a $4K+ speaker was taken at an average of about 77 dB's. They tested the speaker in this manner even though it is WAY more sensitive than that with one watt fed into it. Why would anyone do such a thing? Well...

If someone wasn't paying attention or know what to look for, the results look much better than they really are. At this level, the speaker measured 18 Hz to 20 KHz +/- 3.5 dB's. To try and persuade the reader that this speaker was "really flat", they even went so far as to say that the speaker was +/-2.5 dB's from 35 Hz up to 10 KHz. This same article went on even further to say that "across the midrange, response tightened up even further, to be flat +/-1.5 dB's". If one didn't know better or really study the graphs that they displayed, this would look to be a pretty well designed speaker.

In another section of the same review, they drove the speaker well above this 77 dB baseline and charted the individual output of each driver. When doing an over-lay and splicing all of the composite curves together onto one graph, they revealed that this speaker had a huge plateau that starts at 40 Hz, hits a peak of appr +7 dB's at 110 Hz and then levels back out at appr 200 Hz. Needless to say, the linearity of this speaker went out the window, regardless of how smooth they tried to tell us it measured at ridiculously low listening levels. When the speakers' linearity went out the window at higher spl's, it also took any credibility that the reviewer had with it. Sean
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PS... Anyone wanna guess what make / model speaker this was and what magazine reviewed it?
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