Autoformer on Khorn tweeter

[MarkF]

I am planning on using a T-350 tweeter which is more efficient than the stock tweeter. Has anyone put an autoformer on a tweeter? I am using ALK crossovers.

[D-MAN]

There would be too much insertion loss from an autoformer to the tweeter, I think. Also L-pads have quite a bit of loss, too. But it depends on the amount of attenuation you are shooting for. I had a pair of T-350's years ago, and they did not require special attenuation that I can remember, so my advice is wait-and-see.

Most choose the fixed (or adjustable) resistor approach to keep the losses down. Check out John Warren's site and circuit design for an example using the higher output tweeter JBL 2404H.

John Warren's site

Also, Al Klappenberger has an adjustable (by high quality rotary switch) resistive circuit design for exactly that purpose, too, I know because I asked him and he emailed me a copy.

BTW, Thanks Fini for the instructions on inserting web links!

DM

[WMcD]

I have an old EV advertisement. It shows the RETMA Sensitivity ratings and magnet weights of:

T35B 54 dB, 4 oz.

T35 57 dB, 7 oz.

T350 60 dB, 1 lb.

Note the doubling of magnet weight (generally) and according doubling of sensitivity.

I can't find my notes on conversion of the older RETMA to dB/watt/meter.

I'd think there would be nothing wrong with trying a 3 dB down tap. Generally the mid is already driven off that one and all you have to do is hook up your tweeter network to it. The input to the autotransformer is typically just a high pass, not a band pass.

Gil

[WMcD]

I have an old EV advertisement. It shows the RETMA Sensitivity ratings and magnet weights of:

T35B 54 dB, 4 oz.

T35 57 dB, 7 oz.

T350 60 dB, 1 lb.

Note the doubling of magnet weight (generally) and according doubling of sensitivity.

I can't find my notes on conversion of the older RETMA to dB/watt/meter.

I'd think there would be nothing wrong with trying a 3 dB down tap. Generally the mid is already driven off that one and all you have to do is hook up your tweeter network to it. The input to the autotransformer is typically just a high pass, not a band pass.

Gil

[Al Klappenberger]

MarkF,

Yes, you can use a transformer to cut down the tweeter. You will also need the swamping resistor. To get 3 db, use taps #4 - 0 output. Input to #5 - 0 and connect 15 Ohms 5W from #5 - 0.

AL K.

[Tom Mobley]

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On 1/15/2005 3:44:19 PM Al Klappenberger wrote:

MarkF,

Yes, you can use a transformer to cut down the tweeter. You will also need the swamping resistor. To get 3 db, use taps #4 - 0 output. Input to #5 - 0 and connect 15 Ohms 5W from #5 - 0.

AL K.

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Al, let me clarify a little? to get 3db reduction, use another UT 3619 autoformer, connect the input from the rest of the network to the #5 tap, connect the 0 tap to ground, also attach a 15 ohm 5 watt resistor from 5 to ground. Then wire the tweeter positive to #4 tap and tweeter ground to 0 tap or ground. Is this right?

A good place to tap into the network might be right after the first Hovland 2.2uf? RIght by the big woofer inductor?

[WMcD]

Found it.

djk had advised us that you add 30 dB for the 1 watt and 19 dB for the 1 meter.

Therefore you add a total of 49 dB to the RETMA rating to get 1 watt at 1 meter.

Gil

[Al Klappenberger]

Tom,

"A good place to tap into the network might be right after the first Hovland 2.2uf? RIght by the big woofer inductor?"

WHAT? I don't understand! If you are going to attenuate the tweeter, connect the attenuator (transformer and resistor) between the output of the network and tweeter. Why would you want to "tap into" it?

BTW: you are correct about the transformer and resistor hookup.

Al K