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servo or feedback speakers

Discussion in 'Home Cinema Speakers' started by Dubbing Mixer, Jul 21, 2002.

  1. Dubbing Mixer

    Dubbing Mixer
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    I am fascinated by Uncle Eric and Nic Rhodes advocacy of 'servo' sub-woofers.

    Various strategies were tried several years ago both in professional monitor speakers and hi-fi designs. Phillips were particularly keen on the idea, if I remember correctly. In fact the last ones I saw remaindered a couple of years ago were Marantz.

    After the initial enthusiasm all these designs were ultimately seen as flawed by the majority of critics which is presumably why they fell out of favour.

    So my questions are these:

    Is there some new development which has suddenly made this technology truly viable?

    Or is it simply that the restricted frequency range of a sub makes the problem less intractable?

    If the former, it would be interesting to hear about it and the likelyhood of seeing new full range designs on the market.

    As a result of Uncle Eric's enthusiasm, I shall make sure I hear some examples of the subs soon.
     
  2. GaryG

    GaryG
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    I can't comment on the servo mechanism but I came across this thread on another forum which suggests that Velodyne performance is available at much lower cost if you're a DIYer.

    www.harmonicdiscord.com/forums/viewtopic.php?t=6251


    Disclaimer: I'm no longer a dealer for Adire Audio.
     
  3. Dubbing Mixer

    Dubbing Mixer
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    Thanks Gary,

    I'm not sure I'm any the wiser, but an interesting thread!
    I'll follow it a bit further.
     
  4. Dubbing Mixer

    Dubbing Mixer
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    OK, I followed it further. In terms of extension and SPL there may be something here but they do not go into the all important subject of distortion in any great depth.

    At present, the Velodyne's/Servo's still look very interesting.
     
  5. MikeK

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    Why is this all important?

    Don't be too blinded by figures which may be a bit meaningless in the real world - a servo sub can have ample distortion too, but even this isn't the be all and end all.

    Unless you push a sub towards it's limits, then IMO, distortion isn't as big an issue as you may think.

    I wouldn't argue that "potentially", a servo sub "may" have less driver distortion, but I don't believe it's anything like what you may think, and driver distortion is by no means the only distortion you'll get from a subwoofer.
    A servo controlled driver is no guarantee of low "end product" distortion and high performance - if it were, don't you think more manufacturers would be using the idea - after all, it's been around for decades - Velodyne themselves have been using the principle for nearly 20 years (although to be fair, they are constantly developing/refining it).

    Now, I'm not going to argue about whether you can better this or that sub if you go DIY - it's very hard to say as it depends on so many factors. The Velodyne subs mentioned may be "as good as it currently gets" (and some would say as expensive too) - so actually bettering them DIY may be difficult.
    Doesn't mean you can't get close though, and probably for a fraction of the price too!

    Still, I suppose until you actually try DIY - many people will always be skeptical about what you can actually achieve for relatively little money.
    I think that's unfortunate, but each to their own as they say, and I'll freely admit that DIYing isn't for everyone.
    Personally speaking, I think that's sad, as if there is one area of AV where I believe the DIYer can actually get ahead, it's here.
    But that's just my opinion - doubtlessly there are others who will disagree - and in many cases they may well have a point (just as people may be loathe to admit they've spent £500 on an average subwoofer, so they are even more loathe to admit that the design they have constructed themsleves is anything less than the best subwoofer this side of the planet Bass. More often than not (although experimentation is all part of the fun), it's because they've ignored basic design concepts and attempted for instance to design a 0.3 cuft enclosure with a 12" very long throw sub-bass driver - it's been tried thousands of times before and it just won't work, physics sees to that - but it doesn't stop people trying!
     
  6. Guest

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    Hey Mikki,
    Another one whos gone from expert to novice in three posts.
    Make up your mind for petes sake. First its good then no good then its good then distortsion don't matter then it does. Then suddenly, Velodynes are the best. Man your going round in circles, I'm goin dizzy :D
    Wheres my mates charlie whithorse and garments when I need them. At least they dont keep contadicting themselves. :D
     
  7. Guest

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    Mr Mixer,

    You're right about Marantz doing some (fed via a three-core speaker cable of which I have a 10m length somewhere...). However, I own a pair of the rare Yamahas AST-S1's. Okay, okay I own three pairs of them. With a suitable stereo amplifier (of which I have two) and a special cartridge (supplied with the speakers) the same technology used in Yamaha's subs is employed on the full range speaker (mostly in the nether regions though). The bass port pseudo-magically becomes an "air woofer". We're talking Helmoltz Resonance. I think they sound excellent, incidentally. Not long after Yamaha marketed these speakers a U.S. company called AST issued a legal demand for "Active Servo Technology = A.S.T." to be withdrawn and everything since has been YST (=Yamaha Servo Technology).

    I've P.M.'ed you on the offchance that you might want to own them at a bargain price. :D

    Mike.
     

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