MH (and anyone else that’s interested) –

Here are the plots of my subwoofer operation with my 950 set to different crossover points. This is how I did it: I had my trusty Rat Shack analog meter set up where my ears would be in my normal listening location, with the mic pointed straight up, set to slow response and C weighting. According to the frequency response chart that comes with the meter, using C weighting the meter response is very flat in the range I was checking here, so I made no compensation for meter response. I used Stereophile’s Test CD 3, track 17, which is a series of 1/3rd octave warble tones that are the actual frequency points listed in the chart. The CD is in my Sony CD changer, which connects to my 950 using input Optical1. The test tones run from 200 Hz down to 20 Hz. I was running in straight stereo mode, so I was only running my main front speakers and my sub. My main speakers are Klipsch KLF –20’s, which are large floor standing speakers with 2 10” woofers driven in parallel, and a rated frequency response of -3 dB at 34 Hz. My subwoofer is a Definitive Technology PF18, which has an 18” front firing driver in a “pseudo” transmission line cabinet driven by a 325 watt amp. I have the internal crossover in the sub totally switched off. (This is one of few subs that will let you do that.) I had the meter range set to 80 dB, and the volume control on my 950 was set to –24 dB. Subwoofer level was set the same for all tests. Yeah, I could have produced a more accurate graph if I had an honest to goodness sweep generator, but this method, while not necessarily accurate between points on the graph, served my purposes. I believe the dip at around 80 Hz is probably a room “node” at that frequency, and I’m willing to bet that the hump at around 25-32 Hz is more likely EQ that is built into the sub amplifier to compensate for driver response. Still, I get within +5 and –5 for real room response at my seat, which I don’t think is too bad considering I haven’t done any response shaping treatments to my room. If you have any comments or questions, let me know.



[This message has been edited by Skyfish (edited September 22, 2002).]