my DIY supertweeter thread.

Discussion in 'DIY Discussion' started by bottleneck, Sep 17, 2005.

  1. bottleneck

    bottleneck talks a load of rubbish

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    Im not very good at this sort of thread but I thought I'd have a go.

    What the hell? :)

    Also I have a digital camera now (all thanks to a kind gent on the forum) so can take pictures as I go.... any excuse!

    I'll put up posts as I go.

    Im 'subcontracting' the work to friends and people I know in the right trade, because I want a good job, not for it to look/sound crap.

    ok, here's a few points I should make which should explain the rationale..

    1) Altec and Vitavox horns cut off at about 16k. Hearing (I have read) goes to about 18k. The graphs of the Altec horns I have begin to drop from about 14k, and are pretty low when they get above 16k. The idea of adding a tweeter is to get just a little 'spark' or 'tiz' or 'fiz' or 'add your own silly hifi word here' - basically just that top air and space thing. At the moment (on only some recordings) things sound a little restrained at the top.

    2) I am cheating, the drive units I am using are not supertweeters - they go up to about 25k - so thats just a particularly good tweeter.. maybe I should change the title of the thread.. no bollocks to it...

    3) I AM however going to get the crossover set with an L-pad, so that the resistance (attenuation/volume/whatever) can be altered according to amplifier & room variables over time. Just like on a supertweeter.

    4) I am told I am getting a first order crossover with an L-pad, for those of you to whom that means something.

    5) I selected the JBL 2405.. for a few reasons...
    i. Because Living Voice use them for the same purpose above the Vitavox horns they use, so thats a similar situation and a good model!
    ii. because they are 99db efficient and 16 ohm which matches well with the horn
    iii, because they are used in pro studio monitors and the like, and are supposed to sound very good and be very robust
    iv, because they are supposed to have the right kind of 'sound difusion' to go with a horn or something.

    Anyway, step one and two have already happened.. more to come..
     
    bottleneck, Sep 17, 2005
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  2. bottleneck

    3DSonics away working hard on "it"

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    Hi,

    In case you use a 1st order X-Over please note that with really high crossover points the voice coil inductance is large enough and the capacitor sufficiently large tp cause a resonance, I tend to damp this one using a simple resistor across the Tweeter. Worthwhile simulating/measuring and tuning out.

    Also, as the 2405 is a slot radiator it has a very narrow vertical radiation which especially in the vertical will become narrower with rising frequency but very wide horizontal radiation which may be a problem (same for ribbons btw), a spherical radiation horn with a 40 degree or wider radiation pattern may be a better choice.

    Ciao T
     
    3DSonics, Sep 17, 2005
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  3. bottleneck

    bottleneck talks a load of rubbish

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    no idea what this means, but I will feed it to my technical guy.

    Ciao T[/QUOTE]

    Surely the dispersion depends on what angle you fire the slot, for example vertically, horizontally, or at an angle?
     
    bottleneck, Sep 17, 2005
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  4. bottleneck

    bottleneck talks a load of rubbish

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    right... where was I..

    oh yes, bought the drive units from America, arrived earlier in the week..

    [​IMG]
    [​IMG]

    they have seen heavy wear and are used, but they have been sold by a pro-audio company and tested to spec before shipping.

    second hand makes the price on them more acceptable, although they were still far from cheap.

    Next stage is to get little boxes made up to house them. I will use my local friendly cabinet maker, and get the boxes made out of walnut to match the cabinets of the speakers. The boxes will sit on top of the main speakers (plenty of space).

    I hit on an idea, and printed out lots of brown boxes, and photographed the paper sheets next to the speaker, to help the cabinet maker to colour match the stain.

    Here's the photo..



    Next stop is more liasing with people who can help build the crossover and the cabinet maker.

    Quite a fun little project all in all, and should get me a good result.
     

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    bottleneck, Sep 18, 2005
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  5. bottleneck

    3DSonics away working hard on "it"

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    Hi,

    Yes but my point is that the dispersion pattern is very narrow in one direction and wide in the other (nature of slot radiator). No matter which way you point the slot, you will have a problem getting a reasonably wide coverage somewhere, vertical or horizontal.

    If you use a horn with a spherical coverage you merely need to point the tweeter broadly at the listener and you have a wide coverage.

    BTW, I use the Visaton TL-16H as supertweeter for mainly these reasons (and performance of course).

    Ciao T
     
    3DSonics, Sep 18, 2005
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  6. bottleneck

    bottleneck talks a load of rubbish

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    Im sure you're right to some extent .... except that...

    1) IF it was that much of a problem you wouldnt get them in studio monitors, and they wouldnt have wide spread acceptance
    2) IF it was that much of a problem then Living Voice (and most people on the vitavox forum using horns) wouldnt have adopted them
    3) A big round horn would look ridiculous and far too large
    4) big round horns would have cost a lot more (a big factor)
    5) I couldnt give a monkeys nuts, because I have the drive units already.
    6) You like meatloaf ;)
     
    bottleneck, Sep 18, 2005
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  7. bottleneck

    3DSonics away working hard on "it"

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    Hi,

    Actually, in studio monitors you will find them with a much lower crossover point, around 5KHz and with a lowpass on the Midrange horn. Under those conditions the directivity blends quite well with the equally differing vertical/horizontal directivity of the main horns .

    I suspect many of them again use them as actual tweeters in a multiway system and NOT as "Supertweeter" to fill in above the range covered by a equalised horn Midrange/Tweeter.

    Who said anything about big? At 10KHz (and you will cross over higher) the wavelength is around 3.5cm, so a hown needs not to have any greater diameter.

    Big round horns may cost what they want, but I was merely suggesting spherical radiation. There are many suitable examples in Pro Audio and with certain HiFi Makers (Fostex, Goto, Visaton come to mind).

    Perfectly good argument, in that case you may neverlethess wish to take account of the directivity to seehow you can make best use of them.

    I will not dignify this with a reply. :p

    Ciao T
     
    3DSonics, Sep 18, 2005
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  8. bottleneck

    zanash

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    The disperssion should not be too much of a problem ....more the sweat spot will be relatively small, therefore bottleneck will have to curtail his ballroom dancing listening technique. It will take a bit of effort to get the right possition ....but if it was easy everyone would be doing it.
     
    zanash, Sep 18, 2005
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  9. bottleneck

    bottleneck talks a load of rubbish

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    Good point that.

    Not as far as I can see. Have a look on the Living Voice website..
    http://www.livingvoice.co.uk/airscout.htm
    These speakers work very well. The 45 degree angle on the 2405's have probably been chosen to control dispersion.


    If the 2405's dont work at all I can always replace them with another unit. I suspect (given the Living Voice examples, and advice on the Vitavox and Altec forums) that they will work well. They are taking care of such a small frequency band that they are really overkill.

    I may angle the boxes to fire 'down' by using feet with threaded tapers on them, if you see what I mean, or some kind of shim.
     
    bottleneck, Sep 18, 2005
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  10. bottleneck

    bottleneck talks a load of rubbish

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    The tweeters have now been put into boxes by my local cabinet maker. A very fine job I think, the only thing spoiling the front being the silver screw heads. I think I'll replace these.

    Next the crossovers..

    Not really a DIY thread this really, as I'll be getting some industry pros to do that for me too.

    ... well better to get it right eh?
     

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    bottleneck, Dec 8, 2005
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  11. bottleneck

    Tenson Moderator

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    I'd have thought a narrow horizontal or vertical dispersion would give less boundary reflections and thus suit your philosophy Thorsten?
     
    Tenson, Dec 8, 2005
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  12. bottleneck

    3DSonics away working hard on "it"

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    Hi,

    I would think 25 Degrees Vertical is too narrow outside PA Applications and 90 - 120 Degrees horizontal (assuming normal orientation of the Slot radiator) is way too wide in normal rooms.

    Compared to that 50 - 60 Degrees spherical are probably about "just right".

    The Visaton TL-16H I use has 60 Degrees -6db and 80 Degress -10db beamwidth at 10KHz and up.

    Ciao T
     
    3DSonics, Dec 8, 2005
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  13. bottleneck

    Stereo Mic

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    Nice one Chris, how are they sounding? I know the JBL is a real favourite of the Altec/ Vitavox crowd.
     
    Stereo Mic, Dec 8, 2005
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  14. bottleneck

    bottleneck talks a load of rubbish

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    cheers!

    havent got them running yet, hope to have the crossover built up in the next few days, and get them fired up by next week.

    should be fun :)
     
    bottleneck, Dec 8, 2005
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  15. bottleneck

    bottleneck talks a load of rubbish

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    got the x-over built up by my proffesional friend.

    For now am using Philips Orange drops, which are a great sounding budget component. The other component is an inductor.

    The x-over is a 2nd order. Big thanks to Kevin Scott at Definitive Audio (www.definitive-audio.co.uk) for the schematics for the x-over.

    some pics (low quality camera phone)


    Got them fired up, and the whole thing has been a big success.

    Im really pleased I went to all the trouble of buying these drivers from America, getting the cabinets proffessionally made and getting the cross-over right.

    They sound great, and Im pleased with the result.

    I may play with different up market components, but to be honest the basic sound is so great right now I equally might not bother.
     

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    bottleneck, Dec 17, 2005
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  16. bottleneck

    bottleneck talks a load of rubbish

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    got some posh new parts to put in.

    some silver cable (not a believer in cable, but WTF it only costs a few quid, so what the hell)
    some M caps to replace the orange drops

    and nothing to do with the speaker, a new volume control for the pre (100k stepped attenuator).

    Bits all came from www.hificollective.co.uk

    Here's some pics of my latest bits n bobs

    Kind of fun this upgrading malarky..

    cheers
    chris
     

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    bottleneck, Dec 27, 2005
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