Autoformer for crossover - HELP!

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I would be grateful if someone could point me to a dealer that sells autoformers for loudspeaker crossovers. The autoformer is going to replace the L-pad for my midrange driver.

I'm also curious to see if the autoformer is going to change the values of the caps? Lynn Olson, I believe, says the device is going to flatten the rising impedance... he speaks highly of transformer based attenuation.

If you have experience with autoformers then please speak freely. I would appreciate any input.

The only mainstream manufactors of AF's that I know of is Fostex and Sowter - both are too expensive for my taste.

I have recently found these two companies:
http://www.intactaudio.com/atten.html
http://www.alkeng.com/ (press the Klipch logo and go to "Tweeter attenuator")

My threshhold of pain is 200$ for a pair.

Sincerely
Kris
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kevinkr

Administrator
Paid Member
The alkeng transformer looks very interesting to me.. Seems like it could be a good choice if the offered attenuation range is suitable for your drivers.

The one thing I wonder about is how these guys maintain a constant reflected impedance regardless of the attenuation used, not doing so would result in shifts in x-o frequency with varying levels of attenuation.
 
Dave Slagle at Intact Audio would be my first choice for an autoformer attenuator, and I design and build transformers for a living.

Dave has done more work with this format and at these impedance levels than I have. If you cannot afford Dave then PM me or get hold of Jack at Electraprint.

As for whether an autoformer is a better device than an isolation transformer, it will depend upon the driver and what level of detail it can reveal. Bare ribbons might do better with full isolation. Others will be fine with a tapped coil, especially low frequency drivers

Bud