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paulfk 14th March 2009 01:43 PM

supertweeter problem
 
Hi all. I made some supertweeters using fostex horn tweeters FT17H and use them with my CSS FR125SR fullrange bass reflex speakers and very impressive they are too. Make vocals much clearer, cymbals etc. Now when I connected them to my fostex horns and on another occasion my mates proac studio 140's they were much quieter and laid back, could still hear them but very faintly. I don't have crossovers on the full rangers ( obviously) or the fostex horns that are full range too. Also when connected to the proac's they were connected to the binding posts BEFORE the crossovers. Why would that be so ?

mazdapowered 14th March 2009 06:30 PM

Re: supertweeter problem
 
Quote:

Originally posted by paulfk
I don't have crossovers on the full rangers ( obviously) or the fostex horns that are full range too.
If I've read that right you don't have any cross over on the FT17H? If not you'll need a capacitor atleast to prevent damage to the tweeter. This would also explain why you had problems with the proacs.

I use my FT17H's as a super tweeter and use a .22uF with an L-Pad. If using them as a helper tweeter on a full ranger you might need a larger cap.

planet10 14th March 2009 07:46 PM

You absolutely need an XO (a cap at minimum) on the FT17. If not you will burn up the voice coils and they will get REAL qiet.

dave

paulfk 14th March 2009 07:47 PM

thanks for the reply, yes I have a 1.5uf cap and l pad attenuator fitted. I have no problems with the CSS speakers, but when used with the fostex horns and proacs they were almost inaudible. If I use a meter what should I expect to find when testing across the terminals and adjusting the L pad. Just a thought, could it be that the CSS are 85.5db and so less loud than the Fostex 93db and the proacs 91db.

mazdapowered 14th March 2009 09:00 PM

Good new on the cap :) . Given you've connected the tweeter up the same as the datasheet. Measuring across my l-pad the resistance stays pretty constant at around 8.5 Ohm.

When using mine as super tweeters I can hardly tell their on, even with my ear at the tweeter only very liitle sound is evident. At the listening position though it is easy to tell that the top end is crisper and cleaner.

Cal Weldon 14th March 2009 10:15 PM

Quote:

Originally posted by paulfk
[BJust a thought, could it be that the CSS are 85.5db and so less loud than the Fostex 93db and the proacs 91db. [/B]

You already know the answer. ;)

Cal Weldon 14th March 2009 10:18 PM

Re: Re: supertweeter problem
 
Quote:

Originally posted by mazdapowered
even with my ear at the tweeter only very liitle sound is evident.
Quote:

Originally posted by mazdapowered
.22uF with an L-Pad.
That's not surprising is it? Pretty small cap.

paulfk 15th March 2009 07:39 AM

Quote:

Originally posted by mazdapowered
[B]Good new on the cap :) . Given you've connected the tweeter up the same as the datasheet. Measuring across my l-pad the resistance stays pretty constant at around 8.5 Ohm.
if the resistance is constant what is the purpose of the L pad and what position should it be turned to


planet10 15th March 2009 08:15 AM

Quote:

Originally posted by paulfk

if the resistance is constant what is the purpose of the L pad and what position should it be turned to

The purpose of an l-pad is to shunt more or less energy to the tweeter and allow you to set the level without changing the impedance (and therefore keeping your XO in the same place.

dave

paulfk 15th March 2009 08:19 AM

thanks dave, so a difference in output should be noticed when rotating the L pad.


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