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Matching tweeters for output + SNAXO setup guide (Julian's?)

Discussion in 'd.i.y.' started by ewencummins, Jan 31, 2019.

  1. ewencummins

    ewencummins pfm Member

    Hello,

    Another post along a similar line, but can anyone point me in the direction of matching tweeters for db output. As it happens I have 2 pairs of SL2s, and we may be expecting out third (bless!). So in addition to a possible general tweeter upgrade for one or all pair(s) of SL2s, I was thinking of buying 3 or 3+ pairs of tweeters with a view to matching pairs up.

    Presumably this is about getting a pair of tweeters together that like one another, rather than rejecting all tweeters that don't measure up to e.g. Marlene Dietrich; i.e. if 2 tweeters are +3db out of whack, 2 are perfect and 2 are -3db out of whack then pair them up accordingly, rather than throwing away the out of whack ones.

    If anyone's got a link to guidance on this (or why it's completely wrong headed) I'd be very grateful.

    And if anyone has Julian's guide to setting up a SNAXO I'd be more than interested.

    Yours,

    Ewen.
     
  2. colasblue

    colasblue pfm Member

    EZ tweeter matching is all absolute "rowlocks"

    I suspect I speak for more than a few active system users here.

    1) we blow tweeters like popcorn (Rontoolsie's term but fairly accurate, I reckon on average I go a couple of years and a lot longer with a "good" (whatever that requires) non pair)
    2) first time it happens we buy a Naim "factory matched" replacement pair ($$$$$$$).
    3) second time it happens you wang the live one from the old pair in 'cos you still have it.
    4) no obvious degradation in performance whatsoever.
    5) Myth busted.

    I'm currently running my NBL's on one factory matched d2010 from about 2011 which came as half a pair and one original SBL Scan 2008/11 which was replaced as a precautionary measure in an incoming pair of used SBL's which are currently residing in my loft (from around 1997).

    Two different tweeters though same spec bar the bezel!

    It's fine though the d2008 is is secured into the NBL spring with one bolt only.

    Not a permanent solution and I will buy another 2010 or a pair of 2905/95000's but if I go with 2010 I'm only intending to buy one!

    Having broken the dead one open it's obvious that there's nothing to degrade (ferrofluid filled ones are probably a little different) so provided the manufacturing process hasn't changed a new one is exactly the same as an old one!

    Obviously over 20 years there may be a few issues of change in components and manufacturing processes and therefore my temporary fix involving a 2008 is questionable - But I can't hear the difference!

    The correct way to set up the SNAXO to default settings is unity gain over the pass bands. Test signal at appropriate frequencies and DVM is all you need to do it.
     
    Suffolk Tony likes this.
  3. Suffolk Tony

    Suffolk Tony pfm Member

    Yep, spot on there Mr colasblue. I did buy a factory pair of tweeters for my active DBLs to start with, but that was 'cos I'd claimed on the house insurance - total paid with no question from Farmer's Union. I've since just bought single ones from various reputable suppliers with no discernible difference in sound quality, once they've had a few hours' run-in. I haven't popped one for a couple of years now (famous last words) but I've got a spare waiting in the wings.

    Worth pointing out that the production methods for these tweeters have inevitably improved over the many years of production, so there's less chance of getting an audibly mismatched pair anyway.
     
  4. MJS

    MJS Trade: Consultant at WH Audio

    I've only had to change these a couple of times, but I've always done them in pairs bought together. Then they're both the same age, modern made etc.
     
  5. Suffolk Tony

    Suffolk Tony pfm Member

    I always buy them in pairs, but I discovered just replacing one, rather than the pair didn't have any adverse audio consequences I could hear. That way I always have a spare.
     
  6. hp1

    hp1 pfm Member

    I think back in the day naim had a test rig for the bass /mid loudspeaker units they bought in from mordaunt short and elac and later to test and match the ones they made in house . this rig was also used to match the tweeters but also to add a bit of value to there complete loudspeakers and to
    rope folk into believing replacements were only available from the factory.
     
  7. MJS

    MJS Trade: Consultant at WH Audio

    Yes, they did test and match every driver but I don't remember much about the test rig I'm afraid.
     
  8. ewencummins

    ewencummins pfm Member

     
  9. colasblue

    colasblue pfm Member

    OK easy enough request.

    By DVM I mean digital volt meter. In fact pretty much any digital multimeter with a range of 0-2V or similar will do perfectly well. It doesn't need to be expensive- just consistent.

    You use it on the AC volts scale at whatever range is closest to 0-2V (or even 0-1V at a pinch).

    Assuming a 2 way snaxo or naxo you need obtain only two test tones. You will need a pc of some sort with a dac (the internal one on headphone jack will do) which you can hook up to your preamp and some audio playing software that can put a track on continuous gapless repeat. Pretty much any of them will do.

    You then need to find a couple of test tone files well within the pass band of each filter. Say 250Hz for bass and 10Khz for treble.

    These ones will do though plenty of others out there.

    https://www.mediacollege.com/audio/tone/download/

    You then hook up your PC/Dac to a preamp line input, hook up the preamp to the snaxo with it's lid off and don't connect anything to the power amp outputs of the snaxo.

    Start the PC playing the tone, turn up the vol to your normal listening level and measure the preamp input to the snaxo on each channel with the meter.

    Twiddle the appropriate pair of trim pots until the same level appears at the appropriate amp outputs (ie HF or LF depending on which test tone is playing)

    Then play the other tone and go through the exact same process for the other pair of trim pots.

    You'll know if you have the right pots (ie which pot does what) by whether or not they adjust the appropriate outputs. You should confirm your methodology by checking for zero level on the other pair of amp outputs, ie with the HF tone playing the LF outputs should be zero and vice versa.
     
  10. hp1

    hp1 pfm Member

    The rig for the bass /mid units was a suitable enclosure for the unit being measured with the mounting hole facing upward and a mic hanging from above at about 1mtr away, the units were connected up and just sat on the rim of the hole using there weight to hold them. Then a suitable sweep is applied to the unit and measured/recorded ? with the mic.
     
  11. Mal45

    Mal45 pfm Member

    I'm intrigued - I was half thinking about going active with an Olive Naim system but if the price is new tweeters every so often - it gets to appeal somewhat less! So are the tweeter blowups inherent in some way in the nature of an active setup (if so what) or down to operator error in redoing cabling (which I can understand) or something else entirely?

    Malc
     
  12. colasblue

    colasblue pfm Member

    I think it's having the XO before the power amp, so you effectively have a thumping great power amp connected to a tweeter which it's easily capable of destroying.

    Hence any spurious signal getting into that system can cause a problem and even some that aren't quite so spurious such as turn on thump.

    Fortunately the tweeters Naim use are not too expensive and £50 every couple of years isn't such a hefty price really.
     
  13. chrisn

    chrisn pfm Member

    I have also bought new matched tweeters for my IBLs from Naim at huge expense. I don't think they are any better than the originals or a replacement second hand pair which I used one at a time. I think in my case it is just down to "operator error" when messing about. Obviously if you connect the tweeter to the LF output it is destroyed. Also disconnecting the tweeter before turning the amplifier off and waiting for it to power down completely does he same, the crossover seems to protect in this circumstance.
    So it is just being careful when setting up. I always listen to LF first before turning on the HF power amps to confirm I have it right. By doing this the Naim pair have lasted over 2 years.
     
  14. Mal45

    Mal45 pfm Member

    Thanks to you both colasblue and chrisn - useful to know for future reference and apologies for the slight thread digression.

    Malc
     
  15. MJS

    MJS Trade: Consultant at WH Audio

    I've done a few SNAXO re-wires and mods for people so often have to test this out. I still have a pair of the passive XOs for the SBLs. I simply leave those in first and if they confirm the frequencies are going to the right speaker then they've proven the wiring correct.
     

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