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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
jax2 OP
3,031 posts
 
Sean and all- I just wanted to listen carefully again to confirm what I already had perceived: Listening to the recording at a lower volume, at least on the SET/horn system at work, I really can't tell that there is any distortion on those same high notes that would otherwise be quite obvious at higher volumes. On some I can hear it, but I'm wondering if that is is fed by my expectations. On most I cannot hear any distortion listening around 80db+ (very moderate level for a large space). I do recall listening to the same CD on my friends system with a Unico Unison (80W hybrid amp) and having the similar objections which I attributed to the SS rearing it's ugly head. So I'm thinking that it is the recording and not the gear since it occurs on three entirely different systems. Weird that it doesn't occur to me at the lower volumes though. Perhaps I need to get my hearing checked.

As far as the recording techniques, unfortunately there is no notation as to how it is recorded (there are extensive multi-lingual notes relating to the history of the piece and the proposal for the performance itself). The CD is made in Austria by Sony and is not marked with the typical acronym for how it was produced (ie AAD, DDD, etc.). I checked another of box-set I have on the AllaVox label of Jordi Savall performing solo. Again, no references to recording techniques and lots of history. On that recording, which is also outstanding, I believe they must have had the mics very close to the performers as the breathing is very pronounced. Almost to the point of distraction, but ultimately the music is so powerful, and the presence of the instrument(s) so remarkable, that I it just enhances the intimacy. I mention it because it definitely occurs to me as a unique recording in that respect.

I'd be curious to hear from anyone else who's heard the recording in question (Sibil-La) and could comment directly to having heard this.

Thanks to all who posted for taking the time to respond.

Marco
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
>

PS... Anyone wanna guess what make / model speaker this was and what magazine reviewed it?
bibasset
6 posts
 
Great thread! I'm the guy to whom Marco was referring . That particular listening session in his studio took place shortly after I had just switched to a solid state amp in my system (McCormack DNA .5) and was feeling sensitive to what I felt was an increased hardness or brittleness to upper midrange and high
frequency reproduction. While some of that may in fact be the amp ( and would probably be improved by Steve McCormack's mods) some of it I also believe was increased resolution and transparency of the new amp revealing deficiencies in my digital playback system-a quite aged Pioneer PD-65 with no outboard DAC. Hence, when I heard a similar effect in Marco's much more sophisticated system it prompted a discussion. I found the post regarding the natural hardness/distortion of the human voice interesting, although I can't say that I've ever heard a live, unamplified soprano hitting the upper registers and sounding brittle and a-musical, harder perhaps. And then there is the issue of hall overload and distortion. Avery Fischer hall for example with the orchestra and brass going full tilt gets unlistenable in my opinion-might as well doze the joint! While the old Carnegie was perhaps a bit overdamped, it was always wonderful. Benaroya hall here in Seattle is terrific, although all seats of course do not sound the same regardless of the propoganda.
jax2 OP
3,031 posts
 
Since writing the original query, and only just recently, I've done a couple of major changes to the studio speakers (LaScalas). I was finding that in the much larger space of the studio, and with the very loose wood floors sucking up much of the bass, that they speakers occured to me to be out of balance. I went back to the ALK crossovers which allow some tweaking in the form of varying attenuation in the Squawker. In the smaller room in my home that the speakers were once in (see my system pics) I preferred the AA crossover with the ALK sounding less 'musical' to my ears there (for lack of a more authorative description - I did go back and forth extensively). In the hayloft that is my studio, the ALK's worked wonders and actually sounded better than the AA's. I found also that the recording in question, which remains a favorite, sounded a bit better, but still displayed similar, albeit less pronounced, breaking up at those highest notes. OK, so recently I tried switching tweeters from the stock K77, to a pair of Fane tweaters (English made, used in Edgarhorns - very sensitive. Huge magnet. Slot tweeter). Initially I thought the new tweets sounded a bit hot (110db efficiency was a bit too much), but they did display a remarkable improvement in smoothness and clarity in the high end. I contacted Al Klappenberg, who was kind enough to consider the specs on the Fanes and run the figures through his filtering program to suggest a pair of resistors to pad down the tweets about 6db. He'd nailed it and, with a slight bit of tweaking with the Squawker settings they now blend in seemlessly, and that clarity is remarkable. So the other upshot of this is that I put that very CD on as a test just the other day and low and behold, those highs are no longer distorting anywhere nearly as much. In fact, I can barely perceive any at all. I have to listen again to prove this to myself, but I was quite amazed the first time round. I've also changed amplifcation sources at home since posting this and have yet to try it there. More to come......

Marco
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