any crossover gurus here?

Discussion in 'DIY Discussion' started by shrink, Oct 7, 2011.

  1. shrink

    shrink

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    looking to change the relative output of the treble on my castle conway 3's.

    to the tune of around +3db on the tweeter.

    what steps can I take to make this change to them... what information do i need... is there an easier way.. etc etc
     
    shrink, Oct 7, 2011
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  2. shrink

    Cable Monkey

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    Find and post a copy of the cct diagram.
     
    Cable Monkey, Oct 8, 2011
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  3. shrink

    shrink

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    given castle are now defunct, i'm not entirely sure how i'd go about doing this.
     
    shrink, Oct 8, 2011
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  4. shrink

    Tenson Moderator

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    Do you have bi / tri -wire posts? If so, you can put a resistor network on the treble ones.

    If not, you need to show us a photo of the crossover and tell us the values marked on each part.
     
    Tenson, Oct 8, 2011
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  5. shrink

    shrink

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    Hi tenson

    they are biwireable. But if possible i would prefer to achieve this change by changing the values at the tweeter side, as its likely they are a bit more sensitive than the bass units and are likely being held back by the crossover.

    If i put up some very hi res photos would anyone here be able to advise?
     
    shrink, Oct 8, 2011
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  6. shrink

    RobHolt Moderator

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    Go for it Shrink, we'll try.
     
    RobHolt, Oct 8, 2011
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  7. shrink

    shrink

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    Thanks guys. Will whip them out and take a few detailed pics.

    Im happy to solder etc. Its more a case of knowing what changes i need to make so as not to mess with crossover frequency and phase alignment etc. But i hear there are programs that can calculate and take this into account
     
    shrink, Oct 8, 2011
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  8. shrink

    shrink

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    shrink, Oct 9, 2011
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  9. shrink

    shrink

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    seems a few chaps over at pinkfish are suggesting my best course of action is to replace the upper left resistor with perhaps a 1.2 or 1.5 ohm model instead.

    but I can test out the effect of this by putting a 1.8ohm resister parallel to the existing one and see what difference it makes.

    any further opinions?
     
    shrink, Oct 10, 2011
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  10. shrink

    Tenson Moderator

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    The guess on PFM is as good as any, but I'd not like to say without seeing more of the board. Can you photo the underside to show where the binding posts are connecting? I know you won't want to lift it off the back panel but maybe you can see enough down the gap?
     
    Tenson, Oct 10, 2011
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  11. shrink

    shrink

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    i'll see what i can do tenson

    my memory tells me the back board was quite firmly attached to the PCB, and as such wasnt seperable, without de-soldering.

    but i'll see what I can do.

    for what its worth... the bass terminals would be underneath towards the left hand side, and the treble to the right.... the cables on the right would be facing upwards inside the speaker cabinet.

    perhaps that helps
     
    shrink, Oct 10, 2011
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  12. shrink

    shrink

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    ok tenson.. theres nothing on the back of the panel

    the tracks are all on the surface of the panel that you can see... im uploading a new pic in a second that will indicate this better.

    having followed the tracks around to the best of my ability, i can safely say that the top left resistor is just for the tweeter.. the other one is linked into the bass circuit. so its changing this that i need to do.

    heres the pic:

    [​IMG]
     
    shrink, Oct 10, 2011
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  13. shrink

    shrink

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    if you look at the bottom left (inside the coil) you'll see the screw that comes out the bass terminal... the track for the bass on that side, goes straight into the bottom resistor, and then into one of the caps. so i'm confident that this one has nothing to do with the treble.
     
    shrink, Oct 10, 2011
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  14. shrink

    Tenson Moderator

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    If the other resistor is in the bass circuit then as you say it likely has nothing to do with the tweeter level.

    Seems like a resistor in series, then a capacitor in series followed by an inductor in parallel. This means the resistor will be changing the top end of the tweeter response more than the lower end. This is probably good news for you since it won't upset the crossover much.

    As suggested, try reducing it to about 2.2 or 1.5 ohms.

    http://www.ebay.co.uk/itm/10W-1-5-o...785?pt=LH_DefaultDomain_0&hash=item3f09732d21

    http://uk.rs-online.com/web/p/high-power/6150274/
     
    Tenson, Oct 10, 2011
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  15. shrink

    shrink

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    does this mean i'm likely not to see an increase across the whole spectrum of the tweeters abilities? which may not be what i'm trying to achieve... i'm trying to lift its entire range as best as possible, rather than specifically its top end.

    it depends just how much i'd be missing, whether this is a worthwhile endeavour

    also any particular reason for those recommendations for resistors.. are they of particular quality... am i as well using models identical to that they are replacing (resistance varying of course)
     
    shrink, Oct 10, 2011
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    Tenson Moderator

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    I don't think you want to increase the entire tweeters level as this will make an uneven response around the crossover. The changes should give a gently increasing level from where the tweeter comes in. Similar as using a treble tone control I guess.

    I only gave the links to make it easy for you, they are nothing special, but they are suitable. Resistors are pretty non-reactive components they won't have much sound of their own except that of their resistance.
     
    Tenson, Oct 10, 2011
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  17. shrink

    shrink

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    thanks for that...

    i'll double check connections back to the tweeter terminals with a volt meter, and then set about replacing that resistor.

    going to test first by tapping on a 2.2 ohm on top of the 3.3

    should give me an effective 1.5, and is a basis for comparison. The plan if my sums arent hugely far off, and based on other people suggesting that going from 3.3. to 1.6 would yeild around a 1.5db increase. i'll be looking to go to around a 1.2 or 1.5 ohm resistor. But will try larger values first to make sure.
     
    Last edited by a moderator: Oct 10, 2011
    shrink, Oct 10, 2011
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  18. shrink

    shrink

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    well folks... bought a pair of 3.3 resistors today from maplin (it was all they had that was even close to what i wanted)

    and put them on in parallel to my existing 3.3's. Giving me 1.65ohms. and as mentioned earlier a potential 1.5db lift.

    The resultant change is subtle but evident. The sound has opened up ever so slightly and has gained sparkle. Some of the boxiness around vocals has gone, as a result of the air around the top end. This is close to what I want to achieve.

    I think that this experiment proves that i'm on the right track but would like just a little bit more. Therfore I think what i'll do is replace the 3.3 with either a 1.5 or a 1.2 ohm resistor. I suspect the 1.5 will sound pretty much the same as the current 1.65ohm solution. SO i'm more keen to go with the 1.2. I can always go back up if need be.. these arent expensive components after all.

    Thanks for all the help :)
     
    shrink, Oct 12, 2011
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  19. shrink

    Tenson Moderator

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    Good to know it's working out. :)
     
    Tenson, Oct 12, 2011
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  20. shrink

    shrink

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    certainly no nasties off the back of it.. ive left the stacked 3.3's on for now, and put them back into the cabinets so i can have an extended listen.

    definitely better, but not quite there yet... I suspect 1.2 is the way forward. A nice easy job too, very accessible part.
     
    shrink, Oct 12, 2011
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