1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

AAAArgh How do I rid myself of sibilance

Discussion in 'Hi-Fi Stereo Systems & Separates' started by DonMaico, Oct 11, 2004.

  1. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    just bought a new( well new to me ) pair of speakers and the level of sibilance seems greater than before. The speakers are vintage Kef Duette,. Not sure about sensitivity but they have a 15 ohm impedence. I am thinknig maybe the preamp needs replacing to a passive but phono seems just as sibilant as line level so I am not sure?????
     
  2. Laurel&Hardy

    Laurel&Hardy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    15 Ohms is a very high impedance. Most transistor amps are geared to do lower impedance, usually between 4 and 8 Ohms. It is possible that, because the power amp is now having to deliver voltage instead of current, you could possibly be running out of headroom. Just a thought, although with power handling of just 30 Watts it is a bit of a long shot. Mind you that's 30 REAL watts, so I'll bet they will still kick ass if they're asked to, especially with the monster B139 bass unit - possibly the best bass unit I've ever heard.

    I wouldn't think the preamp is the problem here, what you may find is that most hifi gear today is far more linear at the high extremes of frequency than the gear that would have driven this speaker. So it wouldn't surprise me to find out the frequency response rises somewhat in the treble, which would create sibilance especially with any digital recordings which can have a tendency to sound over bright on older kit.

    If the list of kit in your signature is driving the speakers then I am a bit surprised you have any problems. Leak power amps usually erred to the side of sweetness sound wise, the turntable is a goodie (arm and cartridge?) so that does indeed leave the preamp. I don't know very much about AI kit so I can't comment on that. All I can suggest is look at your interconnect and speaker cable. I'd certainly look at the speaker cable and, just for a trial, try some 2.5mm solid core mains (the single strand stuff). Reason for trying this is that solid core mains cable, although not really meant for speaker cable, does actually have a very smooth sound and is not too bothered about how long or short the cable run is. 2.5mm only costs about 40p/metre as well so it's quite a cheap trial. It has to be 2.5mm squared, the thinner stuff will sound too thin and the thicker stuff is impossible to work with! Only other problem then is whether the speaker terminals on the amp and speakers are man enough for the cable!!

    Hope this helps...
     
  3. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Thanks for that L&H. I am using a valve amp at the moment and my taps are set at 16ohms. Oddly the sibilance seems to be worse with phono than cd but then I am using attenuators between cd player and preamp which is why I thought maybe the power amp is just too sensitive for the pre and I should change to a no gain or passive pre. My previouys speakers( heybrook hb1 ) did not appear so sibilant but were nevertheless somewhat harsh in the upper registers. I bought these new ones ( new to me as they were made in 1967)very much on a wim from the auction room and I think with the right partnering equipment should sound fine.The bass sound seems very good I must say - its just the top end.
    The arm I have is a Xenon and the cartidge ( which i,d like to replace ) is a Grado black. Not sure whether to opt for a Shure or Grado gold tho.
     
  4. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I'll give the mains cable a try cheers!
     
  5. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Looking at the spec it would seem that the duettes are ideally suited to low power valve amps - the max input is merely 15 watts
     
  6. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    someone suggested changing the internal wiring and the capacitors as they can deteriorate with age.
    Trouble with these plug inn attenuators I use is that whilst they roll off the treble they seem to have an affect on the bass as well
     
  7. Laurel&Hardy

    Laurel&Hardy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Yes, attenuators affect the whole frequency range, personally I don't like them as they tend to soften everything and make the bass sound very wooly.

    OK, a thought I had today was this - it could be that the preamp output is too high for the Leak power amp, therefore saturating the input circuit and creating sibilance. I have heard of this before. Today's preamp outs are a much higher level than they were 30 years ago and most, if not all modern power amps have very high headroom for line input. However this wasn't the case back when Leak were making amps, partly because most preamps had very low signal output. So perhaps you may need to look at the Audio Innovations specs for preamp output and see how they match up with what the Leak is able to accept as input. Another possibility is that it could be an impedance or capacitance mismatch between pre and power amp - this will also cause problems if the disparity is large. So, some other things to check!
     
  8. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Thanks for that L&H.I was suggested to me that the Leak was too sensitive for my AI , in fact it has an input sensitivity of 100 mv for 10 watts output.,therefore the suggestion was either a passive preamp such as audio synthesis passion or a no gain version of a Croft Vitale. I tried the attenuators as a cheap interim measure until I made my mind on the pre option.The person who suggested the passive did so because they offer no distortion to the signal whatsover but the person who suggested the Croft felt that a passive would result in the sound being too thin. I thought the best thing would be to find a forum with leak enthusiasts and have indeed found one- yahoo group hjleak. I am just waiting to be accepted( bit off putting as I dont like anything that smacks of elitism or too much like a clique) so i'll see how that goes. I may seek to improve my Kefs by way of new caps and internal wiring as they are old.
    Mike
     
  9. Laurel&Hardy

    Laurel&Hardy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Yeah, refurbing the Kef's will do no harm, just make sure you use decent speaker interconnect for the rewire job and of course, when replacing the caps, ensure they are the same values. You may find you have to make them up using a range of values. For instance, when I replaced the old caps in my PRO 9TL's (sadly no more, midranges died, no replacement!) the bass ones were 80uF non-polar - no such value exists - these were made specifically for the PRO 9TL. So, I had to make these up by using a 47uF and 33uF in parallel to get the value I wanted.
     
  10. Peter Baker

    Peter Baker
    Active Member

    Joined:
    Sep 6, 2003
    Messages:
    621
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    LONDON
    Ratings:
    +37
    Have you considered if it might be a problem with the tweeters themselves. These can stiffen with age, which I would imagine would lead to a tetchy top end?
     
  11. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hmm I think I may send them to be examined by Kef . Funny thing is the sisbilance is not so noticeable with cd which then suggets the cartridge( Grado Black) which may be too bright for speakers i guess
     
  12. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    unfortunately Kef no longer supply parts for Duette but the drivers look ok to me so maybe I'll just change caps and wiring.
     
  13. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    LH why would you use interconnect and not something like QED silver anniversary cable( which I assume is speaker cable)?Only ask because someone else did precisely that.
     
  14. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I notice the tweeter is made of metal .I wonder if its original? Didnt think they used metal in those days
     
  15. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    No its not metal just looks like it.
    Well having done some listening via vynil and cd I have come to the conclusion that the cause of the sibilance lies in the recordings themselves . It is quite clear tha t the Duettes are very revealing and will expose weeknesses further up the chain including recordings.
    My aims, therefore, are:
    a)_ to replace the preamp with a passive unit such as Audio Synthesis baby Passion ,Creek OBH22 or an active buffered unity gain ( I assume this another term for a no gain pre such as Croft Vitale)
    b) replace a somewhat ragged Grado black cartridge with something smooth and neutral. I would prefer MMs because of the ease of stylus replacement, but if MC proves better then I'll opt for that.
    c) buy a better cd player as my Rotel rcd 955 is a bit long in the tooth.
     
  16. Laurel&Hardy

    Laurel&Hardy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I'd use speaker cable mainly because you are putting a fair few volts/amps through the cable and interconnect MAY cause problems here. I re-wired my old PRO's with QED cable (all I could afford at the time) and it worked really well - certainly better than the cable that was in there.

    Cartridges...I have a (now discontinued) AT-OC5, a very good cartridge indeed. This is an MC. MC's tend to be fussy about tonearms, for instance a Linn Basik LVX with the AT-OC5 didn't sound nearly as good as when it was partnered with a Rega RB300, so it may be advisable if you stick with MM's. I can't remember how tolerant the Xenon is of MC's, so check this out first. Generally though, if you're arm is OK with MC's they do tend to track better and last longer than MM's, although as you say, changing the stylus is not an option - it'll be a new cartridge!
     
  17. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I seem to remember Mike Knowles ,who owned Alphason,recommending ortofon mC cartridges and indeed I had a Goldring Eroica before I took my TT up to Eminent audio who rubbished MCs so I ended up with a Grado black MM. From What I read Ortofon cartridges are known for their transparency but not bass so much.I am thinking in terms of one of their High output ones or maybe Denon one.Either way I shall have to get a local dealer to fit it because I am simply not dexterous enough to get alignment right-m fiddly in the extreme! :D
     
  18. Laurel&Hardy

    Laurel&Hardy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    People that rubbish MC's do so because predominatly they've heard them in arm/turntable packages that generally can't handle the extra mechanical stress they impart. For instance SME series II and III arms are not kind to MC's at all because of the knife edge bearing - it chatters and you can hear this! For these arms MM's are a much better choice, and preferable low or ultra low mass ones at that. Ortofon VMS 20/30 are two examples, I used an ADC XLM III on my old Garrard 401/SME III. Ortofon gerenally tend to be a little shy in the bass, so if you don't like lean then maybe you shouldn't look here, although they are very sweet sounding. Of the high output ones the Denon DL160 is meant to be a goodie, but also consider the Goldring Eroica H (high output) and the Ortofon MC1 or MC3 would be worth an audition. Good luck!
     
  19. DonMaico

    DonMaico
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Thanks for that. I use to have a n Eroica so I may return to that one.I have also being comsidering Denon but there is another one which has been recommended to me - Dynavector10x-5 :)
     

Share This Page

Loading...