Would this work?

[warnsey]

G'day guys,

I am looking to add a bit more 'sparkle' to my speakers. I have a pair of custom made speakers that use vifa xt25 tweeter, SS 12M/43100G mid and 21W woofer with a 3-way passive crossover.

I was thinking of getting a Fostex T90a tweeter or similar and adding it on top of my speakers for a bit more top end.

My question is: could I just connect it to the binding posts at the back of my speakers? and if I could would I need to add any Capacitors before connecting the T90a to the positive terminal?

Cheers,
Warnsey

[Brisso57]

Originally posted by warnsey
G'day guys,

I am looking to add a bit more 'sparkle' to my speakers. I have a pair of custom made speakers that use vifa xt25 tweeter, SS 12M/43100G mid and 21W woofer with a 3-way passive crossover.

I was thinking of getting a Fostex T90a tweeter or similar and adding it on top of my speakers for a bit more top end.

Cheers,
Warnsey

A piezo would be the cheapest solution. Cross over high.

Doug

[warnsey]

So how would I wire it in? Would I just add a Cap in between the positive post of the tweeter and the binding post of the speakers, bypassing the internal passive crossover network of the main speakers? I apologise if the question may seem a bit 'simple' but this is one area I don't know to much about.

[planet10]

A cap XO for the T90 would need to be quite high to get the level down enuff...

A piezo needs speciial treatment.

http://www.planet10-hifi.com/piezo-XO.html

dave

[warnsey]

Hi Planet 10

How high would the cap need to be for the T90A? My speakers are 91db efficiency?

And could the Cap just be hooked up in between the tweeter positive terminal and the speaker binding posts?

[Brisso57]

See also

http://www.audiokarma.org/forums/sho...ighlight=piezo

Doug

[wigginjs]

Yes, you can just connect the T90A to the binding posts on the back of your speakers. No, you should not connect it without at least a capacitor in place because the full range signal could damage (probably would actually) the T90A. The value of the capacitor would need to be calculated depending on where you want the T90A to come in (8000Hz? 10000Hz? 15000?). You can calculate this value based on the impedance of the T90A. Try searching for "first order crossover" on google. You will probably also want to implement an "L-Pad" to match the sensitivity of the T90A to the rest of the speaker. This part is kind of optional depending on how much extra "sparkle" you want.

Of course, I'm thinking you probably cross over to the Vifa tweeter pretty high because you are using a 4" mid. If there is an L-Pad in place on the Vifa tweeter you could always just remove it. Or put one into place on the other two drivers. This could produce a very similar effect to adding the T90A.

[planet10]

Originally posted by warnsey
Hi Planet 10

How high would the cap need to be for the T90A? My speakers are 91db efficiency?

And could the Cap just be hooked up in between the tweeter positive terminal and the speaker binding posts?

There are 2 approaches... use an L-Pad to bring the levels down and then XO where you'd like (15K?)

If you find the LPad sucking the life out of the supertweeter then the other is to let the 1st order XO do the attenuation by crossing over high. In this case you need ~15 dB of anttenuation which means pushing the XO urnover some 2 1/2 octaves above where you want, so if 15K then you calc for an 80-90 kHz XO... so with a nominal 8 ohm impedance you'd start with a 0.25 uF cap.

dave

[warnsey]

Thanks guys. I was thinking of crossing it at about 15K.

So lets see if I have this. most of the calculators reccomend using a Cap of 1.35 for a first order Cross. However, If I did it this way that would then mean I would need an L-pad for attenuation . Or alternatively I could use a lower value Cap of around 0.25 which would alleviate the need for an L-pad and still cross at around 15K.

Am I on the right track?

[Pano]

Yes you are. I use the "too small cap" trick all the time. Works a treat.

Try both methods to hear what works for you.