[Me]

Hey guys.  Just picked up a pair of Be tweeters and cheapo 106k (10uf) caps to break everything in.  When playing music through these components, it seemed as though the tweeters were reaching a lower frequency than they should have (I could hear 500hz and slighty below).  Do you guys think the caps are bad or they are not the right value?  Right now, I am just breaking them in and need a simple way to do this.  If I am not using the correct caps, what should I be using?  Also, what is the best method to break them in?  I want to take measurements when they have fully settled.  If any of these questions can be answered, I would greatly appreciate it.  Thanks.

[richidoo]

http://www.scan-speak.dk/datasheet/pdf/d3004-664000.pdf

500 Hz is audible because that's where the driver resonance is, and resonance has a 21ohm impedance peak. The filter frequency (-3dB) is a function of cap value and load impedance. So at 500Hz, the 10uF cap is -18dB if the impedance is 4 ohms. But at 21 ohms, then the attenuation is much less, maybe only a few dB below pass band. The impedance peak of the driver is allowing low frequencies to get through the cap.

To eliminate this effect you can flatten the impedance at the resonance peak with a LCR series notch. Then the 10uF cap would attenuate smoothly at -6dB/octave from 4kHz and be -18db at 500Hz. Without the series notch, it is probably only a few db below the passband at the resonance peak.
More info: http://www.diyaudioandvideo.com/Calculator/SeriesNotch/Help.aspx

Playing loudly with just the cap can be dangerous if you apply too much power. But it is good for quick break in by loosening up the suspension faster if you keep the power low, like 1W or less (<1V at the amp with a 4kHz sine signal, then play music at that level and no higher.) If you have been playing music through it at low levels for an hour, then it is probably already broken in. 

Enjoy that awesome tweeter!!
Rich

[Me]

That all makes sense.  I never really took into account the rise in impedence at that frequency. Doh.  I'll take care of it.  Thank you for the info, and I'm sure when everything is taken care of, the tweeter will sound fantastic!