For the acoustical and some electrical measurements, I am using a chirp sine-sweep technique (100Hz to 20KHz sweep in 2.972 seconds). With this technique you can estimate the impulse response of the system under test. Distortion can also be estimated, they are separated in the time axis from the main impulse response (this is described in one paper that I linked). I can see distortion in some measurements (it is low), but I have try to quantify it more precisely. My software is not written for this at this time.
For the paper from Geddes, I have not seen it. I may take a look.
The microphone is a "Bruel & Kjaer 2238 Mediator". It is calibrated every two years. The measurement setup is simple. It is a laptop (with a good sound card), a good microphone, a CD (test track) and the headphone output of a laptop. For the software, I modified the code from
https://ccrma.stanford.edu/realsimpl...nt_Theory.html
The software run in Matlab (expensive), it should also run in Octave (free). To do the electrical measurements, I made a simple pad to lower the level and a DC block (less than $1 of parts). The microphone that I use is expensive. An altenative can be found for less than $100 at
http://www.cross-spectrum.com/ ,
http://www.parts-express.com/pe/show...-801&FTR=emm-6
Note: You need a phantom power for this mic.
If anyone interested, I can share the software.
I do not have any noise after the amplifier. I did the installation per instructions. In addition, I added 2 ferrite beads (left an right harness to/from the speakers/HU) to prevent noise. The part that I used is similar to
http://www.parts-express.com/pe/show...number=110-450
The measurements are from 100Hz to 20KHz because this is the range that is mostly improve by the Alpine kit. I did not upgrade the woofer. For frequencies below 100Hz, in a car, you feel them more than hear them. I did make some measurement at lower frequencies. It is not flat at all, the woofer (and car?) is a tuned resonnator at 55Hz. This measurement is done with the bass=-2 and the switch on the Alpine amp at #1. I am now running the amplifier with the switch at position #2, the peak at 55Hz should be 4dB lower.
To see how distortion show up in the time response, see "Impulse Responses" in Room Equalization Wizard (free software)
http://www.hometheatershack.com/room...tml/index.html