B&C DE250-8 Question...

[foxfire3]

Can someone please explain to me why PE's D.O.D. tweeter has 2 spikes in the impedance curve?

http://www.parts-express.com/pdf/294-605.pdf

[Pete Schumacher ®]

Can someone please explain to me why PE's D.O.D. tweeter has 2 spikes in the impedance curve?

http://www.parts-express.com/pdf/294-605.pdf

Looks like a tuned cavity resonance similar to a ported woofer.

Other dome tweeters exhibit similar curves, but not quite as defined impedance peaks.

[foxfire3]

Thank you...

[fastbike1]

Does it matter that these aren't dome tweeters?


Looks like a tuned cavity resonance similar to a ported woofer.

Other dome tweeters exhibit similar curves, but not quite as defined impedance peaks.

[edlafontaine]

As Pete alluded to, one peak is characteristic of the driver. The other peak is a characteristic of the device it is mounted to. It is an acoustic impedance peak.

It is likely that different horns (or waveguides) would have impedance peaks at different frequencies.

Dome tweeters are not designed (or expected) to load a fully developed horn profile.

[jcpahman77]

I also noted that the spike at ~700 Hz is below the rated FR so it may not be important at all if you cross it over as spec'd.

[Pete Schumacher ®]

If you look at the rear chamber on that DE250, it's pretty hefty, and could certainly support a dual resonance profile similar to larger rear loaded domes, like this SEAS model.

Notice the double hump impedance, indicative of the larger rear chamber.

http://www.zaphaudio.com/tweetermishmash/Seas_27TBCDGB-DXT.jpg

http://www.zaphaudio.com/tweetermishmash/Seas_27TBCDGB-DXT-FR.gif

[fastbike1]

Pete / Ed: Thanks for the extra info. Prompts me to get around to measuring the Selenium D220's that are waiting in the stack.