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Super Tweeters bargain? need help with setup please.

Discussion in 'Home Cinema Speakers' started by Prometheus, Mar 8, 2005.

  1. Prometheus

    Prometheus
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    Hi all

    I read some very interesting research recently about using frequencies beyond the audible range. After looking around at what manufacturers are offering at the moment they are way out of my price range Tannoy ST50's@ £600 a pair :eek: , seems a hell of a lot for inaudible sound. It made me think about a certain story about a certain emperor and his clothing or lack of ;) . However there does seem to be some quite compelling evidence to show that it does have a discernable effect. I thought about making a set with some ribbon tweeters or something, but I came across these (see pic#'s 1,2 &3) on Fleabay and thought that they looked promising, so I bought a pair which all in cost me £38.00 for the pair inc priority shipping from the USA :smashin: . Here are some specs:

    Super Tweeter
    (400-1310) Specifications
    Type:................................................................ Dome
    Diameter:........................................................10/16 in.
    Diaghragm Mat'l:................................................. Almineum
    Voice Coil Dia:..................................................10/16 in.
    Voice Coil Impedance:......................................8 ohms at 9 kHz
    Magnet Type:........................................................60 x 8
    Crossover Type:........................................ L - C Cut Net Work
    Sound Pressure Level:.......................................96 dB +/- 2 dB
    Operation (Sine Wave):.......................................3 V at 10 kHz
    Magnet Weight:.............................................. 2.86 oz (81g)
    Speaker Weight:.............................................22.8 oz (646g)
    Power Handling Capacity:......................50 Watts maximum music power
    Frequency Response:............................5000 Hz to 40 kHz +/- 10 dB
    Impedance:..............................8 ohms, +/- 15% at 6 kHz, 1.0 volt

    Frequency response chart see pic#4

    Anyway to my question. The instructions with the units explain how to set them up externally with level controls (pic# 5). I bought some l-pad pots (pic# 6) to use for this. Now to where I am uncertain. my plan is to make a small plinth and remount the tweeters on to it with the level controls :cool: . I would like to know from some knowledgeable folk in this area......

    1) Can I increase the crossover point in the internal crossover from the 5K setting up to around 18K to match the roll off from my tannoy tweeters so that I don't get overlap and therefore harsh reinforcement of the high end.

    2) Is this done by changing the capacitor? I have no idea about electronics, but I have noticed that tweeters with higher crossover points have higher rated capacitors. Can it really be as simple as this? :confused:

    3) If so..... will adding a high rated capacitor externally as in the instructions (diag b) create the ability to adjust the crossover point?

    4) are the pots that I bought sufficient for the job? this is the description that they had on ebay (sorry about the length but it seems relevant)
    -----------------------------------------------------------------------------------------------
    NOS/unused "L-pad" level controls for use with vintage-style 2 or 3-way speaker systems, to adjust the output level of midranges and tweeters, especially horn-type drivers such as EV, Jensen etc (or the Altec/University compression drivers that I have listed in a seperate auction). It is a little-known fact that one should not use ordinary potentiometers (pots) to adjust midrange or tweeter speaker levels, as this would cause the impedance of the circuit to vary----with an ordinary "pot", turning the output level down would increase the resistance and actually lower the crossover point of the high-frequency drivers! (Vintage AR speakers make this "mistake", by the way!). By contrast, these L-pads actually use TWO "tapered" resistance units internally to maintain a relatively constant impedance to the crossover network regardless of their volume setting. Much better for hifi reproduction and offers better protection of the driver at higher volume levels (a lowered crossover point would stress the drivers and might lead to blown mids/tweeters). Designed for best response with 8 ohm speakers (use with 16 ohm speakers would lower the crossover point slightly unless you modified the crossover to compensate); power handling (judging from their size, since they're not marked) is at least 10, possibly 15 watts (remember that 15 watts to a high-efficiency vintage horn would blow you out of the room!).
    -------------------------------------------------------------------------------------------------

    5) The above description mentions the impedance of the system. The instructions say that I can just add the S/Tweeters to the top of my speaker and just connect them direct into the speaker terminals as is. If I were to do this is there a chance that I may damage something, either amp or speakers by overloading it and increasing or affecting the impedance of the system. Or is it OK because they are all 8ohms :confused: :confused: :confused: .

    As I said I am certainly not into electronics and don't really understand these issues :rolleyes: :( .

    I think that's all at the moment. I am really keen to get this project sorted and see what all the fuss is about, so I would appreciate any help that anyone has to offer.

    Who need's a pair of Tannoy Dimension TD8's @ £000's (dual concentric 8" drivers with an st50 supertweeter on top) when you can have tannoy Saturns on offer (dual concentric 8" drivers) with supertweeters on top for £160.00 a pair brand new :D :D :D .

    :) :) :) :) :) :lease:
     

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  2. phillfyspoon

    phillfyspoon
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    looking at the Frequency response chart there is a massive steep curve to get upto 10khz most good ribbon tweeters have a good straight line from 1khz to 40khz. im no expert but im sure they are not very good.
     
  3. Prometheus

    Prometheus
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    I appreciate your point and for the money i'm sure they aren't the best but I don't want the bit from 1Khz to 10Khz or am I missing the point? i only want the 20Khz - 40Khz bit which seems to have a reasonably flat response please explain if I am interpreting the graph incorrectly.

    Does anyone have any answers for my earlier questions?
     
  4. Prometheus

    Prometheus
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    :hiya: :lease:
     
  5. avanzato

    avanzato
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    I'm not really clear myself on speaker design but the instruction say it's an L - C cut crossover which would be an inductor and capacitor. Have you taken the tweeters apart yet as presumably the crossover is inside the case. If it is then you can calculate new values for the components.
     
  6. Prometheus

    Prometheus
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    Hi avanzato

    Thanks for replying. I really don't know anything about electronics and I'm afraid that you have lost me already. I will take them apart now and post a photo. check back in 10 minutes.
    :smashin:

    .
     
  7. Prometheus

    Prometheus
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    Here is the pic of the Xover bits. The black unit has 'Tokin (brand name) 0.35mH' written on it. The grey thing has 'Unicom Bi-Polar 50V 2.7mfd' on it.

    How do I calculate new values for the components??? :lease:

    :confused: :rolleyes: :confused:
     

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  8. eviljohn2

    eviljohn2
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    The black thing is a 0.35milli Henry inductor (the "L" in the description and the grey thing is a 2.7milli Farad capacitor.

    By replacing these with the same type of component (ie. inductor or capacitor) you can change the frequency that the crossover works at. For the more technically minded, what do people think about this simple first order filter? For a design like this I'd be tempted to go for a higher order high-pass filter but I'm not an audio expert. :)
     
  9. Prometheus

    Prometheus
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    I'm all ears :laugh:. I like the idea of improving on what i've got but I'm afraid that I'll need to be walked through any changes :( , but i'm a quick learner and I'll do a bit of reading to see if I can get up to speed. Any suggestions on where to start would be gratefully received. :D
     
  10. eviljohn2

    eviljohn2
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    I don't think anybody can guarantee any improvements but I think there could be the potential for it particularly as the tweeters weren't that expensive to start with.

    Just done a quick google and found this:
    http://www.radio-electronics.com/info/circuits/lc_highpassfilter/lc_hpf.php
    which is about as entry level as it gets. You'll notice that in the notation used in that link that there is a "T-type" filter in your crossover. :)
     
  11. Prometheus

    Prometheus
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    Thanks John

    I will study this and get my thoughts together, and come back with questions when I have them if I may :smashin: . Thanks for replying.

    P.S. the tweeters were cheap, but I have read a few things about them that were quite hghly regarded in the 70's despite being a Tandy corporation product.
     
  12. avanzato

    avanzato
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    If you search for 'crossover calculator' you'll find several sites with simple tools for calculating the components to a basic level. Put in the impedance of the super tweeter and the crossover frequency you want and select the 'order' of crossover you require. The order is how fast the crossover rolls off the frequency per octave: First order is 6db attenuation, Second order is 12db, Third order is 18db. First order is the easiest as it is just a capacitor in series with the tweeter, your tweeter looks to have a second order network.
     
  13. Prometheus

    Prometheus
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    Thanks a lot this makes things a little easier........ I think. My next question is:

    In order to calculate the desired crossover point where should I put it?

    I have the Tannoy S8 Saturns with dual concentrics (see my thread) do I need to find out exactly where the tweeters roll off and try to match the crossover point to that or do I go straight for 20Khz which is the quoted upper frequency response for these speakers???

    Also what difference does the db attenuation point make?

    Thanks in advance.
     
  14. Prometheus

    Prometheus
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    I am using the crossover calculator for the second order crossover as per here:
    http://ccs.exl.info/calc_cr.html

    and I am asked to make a choice between the following:
    Linkwitz-Riley crossovers match attenuation slopes so that system response is flat at crossover point.
    Butterworth crossovers yield to a peak at the crossover frequency.
    Bessel crossovers have a frequency response between Linkwitz-Riley and Butterworth crossovers.

    Am I right in assuming that these are named systems for crossover design thus affecting the choice of component, depending on the desired effect required.

    If so.... which one do you think would be best for this application?
    logic or instinct guides me to presume that a flat response at the crossover point would be preferable...... am I right?

    Thanks
     
  15. severnsource

    severnsource
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    Bessel and Butterworth are transfer functions named for the mathematicians who created them. In electronic terms Butterworth filters have a maximally flat frequency response in the pass band but a poor phase response resulting in some degree of ringing, Bessel filters have optimum phase response - no ringing but slow frequency roll off rate. Linkwitz-riley filters are designed to give maximally flat acoustic response in the crossover region when used in a properly designed system.

    In your case what filter shape to use is completely irrelevant, just choose any one you like, or you could just use a 1 to 1.5 micro farad capacitor in series which will raise the turn over frequency to the 12-18KHz region.

    I'm curious to know what material you will use to test the ultrasonic qualities of this system. CDs have no output above 22KHz, most broadcasts have no output above 15KHz, LPs have only noise and distortion at HF (fairly small amounts with a good cartridge, higher amounts with a poor cartridge). The only systems with ultrasonic capabilities are SACD and DVD-audio and most of the catalogue seems to consist of reissues of old analogue material which is also likely to only have noise at ultrasonic frequencies. Even modern recordings are pretty unlikely to contain significant ultrasonics as most studio microphones roll off at HF.
     
  16. Londondecca

    Londondecca
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    I would recommend www.diyaudio.com huge amount of detail for crossovers, super tweeters etc
     
  17. Nimby

    Nimby
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    It's no use blinding them with science severnsource. :)

    Supertweeters are just another way of parting fools from their money. :D

    If you extend the frequency response upwards you'll want to balance it at the lower end. If you haven't a completely flat response down to 2-3 Hz then a supertweeter is utterly wasted.

    Take my word for it. :cool:

    Nimby
     
  18. Prometheus

    Prometheus
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    Hi Nimby

    Thanks for your words of wisdom :rolleyes: . Have you tried a supertweeter arrangement for yourself or are you an expert at reading chart data? I'm inclined to think from the way that you responded that the latter is the case :) .

    Much as I must humble myself to your clearly evident knowledge of said sciences. I however believe firmly in giving it a try despite what the charts might say. I have read quite a few differing opinions (not just the stuff pumped out by Tannoy incidentally) and scientific documents including the paper by Tsutomu Oohashi, where using EEG results he finds evidence that we are able to perceive of frequencies beyond the audible range. Also there are other parallels to be drawn with digital recording rates. With 96kHz DAT machines Pioneer introduced in the early 1990s, sound quality was clearly superior at 96kHz sampling rate to that of the same machine operating at 44.1 or 48kHz, even though resolution remained the same in both cases at 16-bit. In reference to your comment about having a flat response down to 2Hz, if I were only after achieveing perfect oscilloscope sound then I am sure you are correct. However there is an argument that the introduction of a supertweeter can and does cause phase distortion in the audible range, which on paper is a negative and undesirable effect. That being said live instruments and speech and myriad other sounds in nature must produce similar effects because as we know nature does not care about our audible range when going about it's business of creating the cacophony of sound enveloping us in our world ;).

    In conclusion as I said at the outset, whether or not the effect that is produced can be seen on paper to be a positive or a negative one. The fact seems to be that it does have an effect, and as such the only way (as is so often quoted here on the forums when talking about subjective speaker reviews) is to give it a try and see. So here I am giving it a go to see for myself what many other people have seemingly strong opinions about despite thier level of actual experience. :D ;)

    In light of this (my opinion that is) I would appreciate some help with my question rather than casting aspersions about the foolishness of experimentation without which the world may still be deemed to be flat. You do believe that it's a sphere do you Nimby? :devil: :D .

    .

    .
     
  19. Londondecca

    Londondecca
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    Whats that...the Earth is not flat? Next you will be telling me it is not carried by an elephant which stands on a turtle.

    I think there is little doubt about our ability to perceive very high frequencies and the whole psycho acoustics area is very interesting but does the introduction of another driver with very different propagations properties help. I do not know the answer. Maybe the introduction of new phase distortions might explain why super tweeters have a mixed reaction. By this I mean not only the acoustic distortion but electrical as well.

    If the tweeters were mine I might be tempted to roll off the highest frequencies as we do not know how the driver behaves at say 50Khz. There could be horrible driver distortions or any number of things which might impact on the sound.
     
  20. Prometheus

    Prometheus
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    Thanks for the other info severnsource. The point you make here is a very good one. I have DVD-A capability so this is where I intend to use the capabilities of the ST. Having said that I read somewhere that by adding a ST' differences are made to standard 22KHz recording too. I cannot remember the details, I will try to find the article and report back on this as logic says this makes no sense. Either way it'll be fun trying to work out whether I can hear a difference or whether the Emperor really isn't wearing anything ;) .

    Thanks again for the other info, I'll get there in the end. If nothing else they will make interesting speaker candy as I am intending to make some new egg shaped bodies for them out of cherry wood to match the saturns finish. I'll post pics when I have them.

    regards.
    dave.
     
  21. Mroizouk

    Mroizouk
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    I'd be disinclined to extend frequency response up beyond 22khz unless you're building hi-fi for dogs.
    Its not even like sub-bass which you can feel if not hear, or do extreme high frequencies have similar phychological and physiological affects as extreme LF are reported to have?
     
  22. Prometheus

    Prometheus
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    :laugh: :laugh: :laugh:

    Please excuse my ignorance, am i correct in assuming that you mean to cut off the frequencies above 50KHz thus preserving the 18KHz - 50KHz region?

    If so then how can this be done?
     
  23. Londondecca

    Londondecca
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    And yet we accept that a subwoofer can help by producing subharmonics
     
  24. Prometheus

    Prometheus
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    That is exactly the question which led me to see for myself. :smashin: .


    .
     
  25. deanym

    deanym
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    My supertweeters are not diy, however the addition of them to my system made the treble a lot smoother, and removed some of the splash from lesser recordings.

    The bass is also improved although far more subtly. I don't use a sub for music, so i can't comment on how a sub and supertweeters integrate.

    Best of luck though in your project, let us know what results you get.
     
  26. Prometheus

    Prometheus
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    What supertweeters do you have Dean?
    Townsend?
    Sequerra?
    Tannoy?
    Fostex?
    Realistic/Radio Shack?

    ,
     
  27. Londondecca

    Londondecca
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    The way low frequencies affect the body is completely different but both high and low frequencies are perceived by the brain and fall outside of the normal 20 - 20Khz range.
     
  28. Nimby

    Nimby
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    What do I care? I'm as deaf as a bat above 1.5KHz. :rolleyes:

    Nimby :D
     
  29. Prometheus

    Prometheus
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    :laugh: :laugh: :laugh:

    .
     
  30. Nimby

    Nimby
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    But I can still hear them as pressure in the ears! :devil:

    Nimby

    (stumbling from one overwhelming truth to another with no time to pick himself up) :cool:
     

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