Receiver vs Sibilance..article...Advice

Discussion in 'Archived Threads 2001-2004' started by Richard_s, Apr 8, 2002.

  1. Richard_s

    Richard_s Second Unit

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    Below I have included some text from a Q&A that I found while researching sibilance on the internet. My system sounds great as I have talked about in other posts but exhibit moderate but anoying sibilance (JBL N26 fronts, N-center). My next purchase will be a new receiver with DPL II in addition to DD5.1 as a minimum (the DPL II is to improve my sound from my "digital" cable service which does not give me SPDIF output only downconverted L&R analog). The DD5.1 etc is for my DVD movies/music.
    OK now my question
    I really don't understand the information presented below but it does make me beleive that not all receiver amplifiers will be the same with regard to sibilance. The last thing I want to do is make this worse. Given your experience or based on the following information Is there a particular brand/model that would be best. I can wait for the new models that are comming out.
    The Text:
    Could it be said that amplifiers with high damping factors use a lot of negative feedback, and therefore, would be expected to have excessive sibilance?
    A We can say that a high-damping factor, by definition, means a low output impedance. The benefits of negative feedback are lower distortion, wider bandwidth, and lower output impedance, at the cost of reduced gain. That, in itself, would not increase sibilance. However, in some situations where the "designer," usually not qualified for the term engineer, will twiddle with the negative feedback circuit in order to either try to cheat the gain/bandwidth tradeoff by using the negative feedback circuit to apply what turns out to be positive feedback on the upper end, creating a slightly rising frequency response in the audible range and a peak in the ultrasonic portion of the amplifier's bandwidth, which then suffers from very poor phase response and poor stability because of it. In such a case, it would be very possible that the rising response, or more likely, distortion elicited by driving a reactive load which made the amplifier unstable, would add a harshness or edge to the upper mid-range and treble, making it appear perhaps fast or revealing, or simply, sibilant. It may also be that the "designer" simply used negative feedback to get good numbers for a spec sheet out of low quality parts and a poor design, and that the amplifier, if measured intelligently, would test very poorly, exhibiting a significant ratio of its distortion spectrum in the higher harmonics. Lots of negative feedback can lower the overall amount of THD, but add some harmonics up around the fifth or seventh, which are very noticeable and very irritating. That is one big reason why class A single ended triode amplifiers, using no negative feedback at all, can have THD of 1% and the listener is in heaven, while a mass market receiver with 0.001% THD and significant amounts of negative feedback, sounds bad.
    So while it may be accurate (or may not) to say that some amplifiers with very "good" damping factors may be sibilant because of the particular and individual use of negative feedback in that model, I don't think one could say that an amplifier that uses a good deal of negative feedback and has, as a result, a "good" damping factor, would be necessarily sibilant. The sibilant amplifier would be sibilant because of poor engineering, or rather a poor engineer. I think that it's interesting to note that after testing a bunch of DVD players in Redmond, Washington a few weeks ago, although the specs provided by the manufacturers in the manuals are probably quite similar in nature, NONE of them measured the same. This not only raises questions that measurements aren't sensitive enough to characterize sonic differences, and challenges the usefulness of manufacturer's "specs" as well. Personally, I think they're pretty useless (manufacturer's specs, that is). Lastly, there are lots of very fine amplifiers that use a little negative feedback. It is the overuse of negative feedback that gives it a bad name
     
  2. Larry B

    Larry B Screenwriter

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    Richard:

     
  3. Richard_s

    Richard_s Second Unit

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    Larry:

    The anoyance is livable its anoying yes but not all that bad. There is no way I can get anything else even close in price to $249 so that is a factor as well.I would like some advice on this topic on what receiver make/Model may either minimize the sibilance or at least not known to emphasize it and make things worse. For anything but a few types of voice situations there is no sibilance and Music and HT is outstanding with tremendous presence and sound quality. Things sound TRUE and the speakers appear to be timber matched. Also for the music I listen too I prefer "bright" speakers so the sibilance I do have I feel is unavoidable.
     
  4. Saurav

    Saurav Cinematographer

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    I remember an older thread on this - what advice did you get there? Have you tried playing with your speaker positioning, especially toe-in? Wall hangings and/or floor rugs? A lot of times, the room's contribution to sibilance is as much as, if not more than, the equipment.

    Also, is it "a few types of voice situations", or a few recordings? Some recordings are more sibilant than others, and that's something you just live with. The only way to remove sibilance on all recordings is to have a system with a slightly rolled-off top end, and it sounds like that would be against your sonic tastes.
     
  5. Richard_s

    Richard_s Second Unit

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    I am not sure yet if it is just some sources (TV, CD). Its hard for me to know I guess. What I need is some recording that If I have a "real" sibilance problem I will hear it and if I don't here it then I will know it is only certain cases.

    The new Diana Krall "live in paris" was recommended as a test. What I am not sure is if this has sibilance of its own or will only have sibilance if it is my system causing the sibilance. It was recommended because it is a "REFERENCE Audio Quality DVD" but I am not sure if that means it should not have any inherent sibilance.

    I don't know if this helps me answer the question but if I listen to my favorite classical station over the old Antenna this sounds great and all of the hosts (female has a "bright voice" and male) have no sibilance.

    Any other recommendation to test if the sibilance is my system or the source would be appreciated. Also recommendations for a make/model receiver that will be a good choice for me (Budget well $300-$400).
     
  6. Aslam Imran

    Aslam Imran Second Unit

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    Get a warm sounding amplifier with rolled top end like a Rotel or a B&K and that should reduce the sibilance considerably. Brighter amplifiers have a higher amount of sibilance (or atleast it stands out more) depending of course on the amount of negative feedback used. Brighter speakers with a bright amp will only aggravate this situation, so if your preference is a bright sounding system then you might have to live with it.
     
  7. Richard_s

    Richard_s Second Unit

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    Thanks for the information.

    Yes you are right I do like a "bright" sounding system so this sibilance is something that may be unavoidable. That is kind of why I stated that "the sound is great but there is a moderate sibilance that is anoying".

    Is there a way to tell from a receivers specification if it has a "warm" amplifier or maybe there is a review/comparison somewhere.

    I am quite new to this more technical side of audio so bear with me. What is "rolled top end" is that the same as a rolloff at say 10khz at -2db/decade? If so from what I read the sibilance is in the 6khz frequency area so I am confused how a "rolled top end" will help?
     
  8. Saurav

    Saurav Cinematographer

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    Well, yes, sibilance isn't in the top octave, but a brighter sounding receiver will probably have slightly accentuated higher frequencies, which would apply even below 10 KHz. A rolled off top end just means a curve which slopes back down. And in theory you're right, you could have a receiver with a pretty rolled off treble which can still accentuate the sibilance frequencies, but that would be unlikely.
     
  9. Richard_s

    Richard_s Second Unit

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    Saurav: Thanks makes sence.

    What I did is try my sons bedroom receiver which is a Kenwood kr-a5080 (cheap $100 but kicks out plenty of power). This is an inexpensive stereo only receiver. Now what I found is this:

    It did improve the sibilance some but not much. The the treble was set to 0db. The system seems to lack the overall "brightness" that I like. Violins, trumpets, piano just do not sound "real" to me. My Pioneer VSX 602s is definitely brighter and definitely has a little more sibilance. I also definitely like the sound I get with the Pioneer over the Kenwood.

    Is there any way to build an atenuator that effects the sibilance with minimal effect on the rest of the high frequencies (kind of a notch filter). Probably impossible just thought I would ask. It seems that I can not improve my system when I replace my receiver since I definitely like my sound "Bright".
     
  10. Saurav

    Saurav Cinematographer

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    I'm not sure how easy that would be. You might be better off getting a good equalizer, something that (a) is transparent enough that it doesn't mess with the rest of the sound, and (b) is flexible enough to allow you to adjust narrow frequency bands. I know equalizers are generally frowned upon, but I believe the technology has advanced a lot recently, and modern equalizers do more good than harm.
     
  11. John Sully

    John Sully Stunt Coordinator

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    I guess that I'll be the dissenting voice here. If you have sibilance problems I would look at the speakers first. The speakers are the first place that sibilance problems should be looked at. Generally this indicates a peak in the 4K to 8K region. While the JBL's are generally well thought of here, they may have a peak in an area which you are sensitive to. The best thing to do is to audition several differnt speakers in your room and find the one that sounds best to you. Axiom seems to be making some really nice low priced speakers, but PSB, Paradigm and Boston (and there are many others) make very nice low priced speakers. Personally, I'm using Boston CR9's and find no sibilance problems with them. Since they have recently be discontinued, they can be picked up for a very low price (~$250), see if you can find them and give them a listen.
     

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