This is a perfect example of what I have been saying for quite some time. I just do not trust all of the measurements I see from some of the subs being tested. I just cannot beleive that at 75 dB we can get so much room gain from some of the systems being tested. I would think that most systems would somewhat resemble the results of the modeling software- within reason. Some room gain should be expected, but for the graphs to roll up below tuning is hard for me to beleive. That is why I keep asking about repeatability with different computers and equipment. I am super happy you got some good data. Repeatability is my biggest problem with this setup. I am getting close with my REW setup, but I want to be able to judge my results against another independent tester. That was the purpose of my GTG, but little interest has been given to the idea. Maybe at a different time of the year.I gave this a try on another computer... 0 to 200Hz sweep using 128, 256k, 512k, and 1M sweep lengths (graph 1, seperated traces is turned on). Graph 2 shows 0 to 20,000Hz sweeps at 128k and 1M.
Computer 1 is my HTPC... 2.5ghz dual core, Gigabyte GA-E7AUM-DS2H motherboard using the onboard Realtek Digitial Input and Output.
Computer 2 is a Lenovo ThinkPad X61T, Core2Duo 1.6Ghz, using USB Soundblaster X-Fi.
As you recall, my initial question surfaced when my results from a 0 to 200Hz sweep were different from the results from a 0 to 20,000Hz sweep between 0 and 20Hz (graph 1 below for reference).
Anyway, comparing these with the earlier readings, it looks the computer was the source of the difference and not the sub or pre-pro. Is my understanding correct? (I suppose if I was really motivated, I'd connect the X-Fi to Computer 1... just don't have the time or energy right now.). Any thoughts on why this might be the case?
Good job finding out about the measuring problem.