When I use an SLP meter to set up my system can I use the built in test on my receiver for the test instead of purchasing a CD. Do I start test, then say when (L) appears turn volume up until 70 appears on meter etc. I can do this for L,R,Center, Rear but how do I do it on my subwoofer. Doesn't show on my receiver. Do I turn the frequency or volume up on receiver to get it set properly? Sorry for being so stupid. The Meter's here are $100.00 just wondering if it is worth purchasing.