Last weekend I made some measurements of my system freq response (mains and sub) using a RS SPL meter at my listening position and a RS correction chart.
I used an old Stereophile test CD which has warble tones said to give more accurate room response. I calibrated my system to 75dB at the 1Khz tone, and here are the results form my main speakers (Energy Veritas 2.3i):
1K-75.0, 200-86.5, 160-87.5, 125-88.5, 100-86.0, 80-76.5, 63-77.5,
50-76.5, 40-86.0, 31.5-82.0, 25-74.0, 20-72.5
I made these measurments with the main speakers set to large in my Outlaw-950 pre-processor. Turned the sub and all other speakers off. I tested via digital input stereo mode and bypass, from CD two channel analog inputs and from the 5.1 analog channel inputs I use for SACD, with the 80Hz analog filter disabled. Obtained nearly identical results from each.
I'm a novice at testing for sure, so I'm not really sure what to make of this. My first though is why did it dip 10 db from 1k to 200Hz, and why ~10dB dip/notch from 50-80Hz, and then rising back to approximately the 200Hz level at 40Hz?
I was thinking I might not be getting true bypass and the Outlaw's filter was somehow in-line. I tried changing the crossover (which souldn't make a difference since I had set main speakers to large) and ) from 40 -120Hz, made no difference in the measurments.
At this point I was thinking this must be a characteristic of my speakers and started to get worried they dropped off sharply until 40Hz. Thought maybe this was where their port was tuned at and where it kicked back in.
I engaged the sub, set the mains to small, set the crossover to it's maximum setting of 150Hz. I turned the level on the main speakers all the way down so I would only measure the sub. Still had the same dip ~10dB drop from 50-80Hz. Tried various crossover settings, made not difference.
Any of you who are knowledgable with room/speaker measurement procedures have an idea what's gong on here? Am I doing something wrong with the way I measure? Do I have a null at my listening position?
Very bothersome considering this is exactly in the band where there is allot of bass material.
Help, advise, assitance, comments appreciated.
