This is the way I found the proper X-2 value for my amp from the Vandersteen Q&A:
Stuart (3/22/06): This is just a suggestion from Stuart: In setting up 2w or 2wq subwoofers, the user has to select the proper crossover capacitor to use between the pre-amp and power amp. If one knows the input impedance of the power amp, this can be calculated using c= 1/(2*PI*R*80) where R is the input resistance of the power amp and PI=3.14. Unfortunately, the input resistance of the power amp is often not published, or even if published, the published value is often not accurate. The input resistance of the amp cannot be easily measured (a multi-meter will not work). An an alternative to determining the right capacitor I suggest the following: 1. Wire the subwoofer and main speakers to separate speaker outputs on the amplifier. 2. Download and burn a test tone cd containing an 80Hz test tone ( available from
http://www.realtraps.com/test-cd.htm ) 3. Play the cd alternating between the main speakers and subwoofer. 4. If the proper capacitor is chosen (with the sensitivity/db pot in the back of the subwoofer properly set), the main speakers and subwoofer will each have the same loudness. You could use a dB meter to determine loudness, but the ear is really sufficiently accurate.
Answer: HELLO STUART, THANKS FOR THE SUGGESTION. THE MOST IMPORTANT PART IN THE SET UP IS GETTING THE 3DB DOWN POINT OF THE CUSTOMERS (MAIN) AMPLIFIER. THIS SUGGESTION IS MORE ACCURATE. TAKE ANY DIGITAL VOLTMETER SET TO AC VOLTS. WITH THE MAIN AMPLIFIER PROPERLY HOOKED UP TO THE MAIN SPEAKERS, VOLT METER ACROSS THE BLACK AND RED OUTPUT TERMINALS. PLAY A TEST DISK WITH TEST TONE AT 1000HZ ADJUST THE PREAMP VOLUME FOR EXACTLY 1 VOLT. PLAY THE 80HZ TRACK AND THE VOLTAGE SHOULD BE .707 VOLTS. IF IT IS HIGHER THAN .707 ADJUST THE WX-2 TOO A HIGHER IMPEDANCE SETTING. IF THE VOLTAGE IS LESS THAN .707 ADJUST THE WX-2 TOO A LOWER IMPEDANCE SETTING. ACCURACY OF THE EXACT X-OVER FREQUENCY IS NOT AS CRITICAL WITH THE 2WQ AS WITH THE 5'S AND QUATRO'S WHICH NEED TO BE RIGHT ON.
http://www.vandersteen.com/vandersteenaudioqs.htm
