DIYMA has been the home of many enthusiasts seeking quality sound for over half a decade. Many of the members have to come to treasure 3rd party tests and the scientific method. With the revival of speaker testing on this site, we can help too by testing the final product.
I have set up a few simple tests to capture a generous amount of data from any member vehicle. The last So. Cal. meet was a lavish expression of technical might, with a wide variety of testing gear. Since I frequent the local meets this is where most of the volunteer cars will come from. That's not to say I will only test So.Cal. vehicles, I'll test anybody's car, stock cars etc. With the latest generation of testing equipment we can perform the majority of speaker tests in a car with no headaches. The only requirement for the test is a standard CD player.
Next I will list the basic layout of the tests. I can submit a post later on data interpretation and cater to each of you as needed.
I will have these available at the meets as a printed PDF file. For those that want to type in ahead of time send me a PM so I can send you either the empty PDF or the Lyx file.
Enter power per sheet entry line in continuous RMS at the speaker terminal.
-SPL is minimum 90db A-weighted L+R (to get good noise rejection and emulate human hearing)
-use sine sweep for best quality data
-minimum 30 samples averaged (left ear, left front, straight ahead, right front, right ear; minimum 6 of each)
-3 tests total, left speakers, right speakers, all speakers
-1/6th octave smoothing (one step better than human hearing, ears pickup 1/3)
-5db steps for the DB axis
Harmonic Distortion testing:
-test at 90db A-weighted first, and then move on in 5db steps until the owner stops giving me the ok. All cars will do fine at 90db imo, even if your crossovers and EQ are all out of wack. Based on the first result I will go ahead and test at louder level if the owner agrees.
-test right speaker only. If I test the entire system some people will have their left speaker turned down lower compared to the right because they are closer. This will give them a disadvantage in HD. The same car could get better HD by simply equalizing the gains between left and right. 5.1 guys can get exceptions.
There is no reason to believe the left speaker will have different HD. The drivers and crossovers are the same. Reflections would be different but that reduces my testing variance as well, which is good.
-in the same plot: 2nd,3rd,4th,5th and 2nd-5th order harmonics along with the FR
-maximum HD test is at 120db, mic clips a little after that
-valid resolution 12hz - up to 10,000hz depending on the test (basically only the frequencies that matter, where HD is audible)
So at the minimum there will be three files per car: info, FR, HD @90db. This will be the base. From there it depends on how loud you want to be tested for HD. As always, all liability is on the owner, I can teach you how to click buttons if you want to do it all yourself.
Previously I said that people would be able to re-test if they want to tune based on the initial results and improve their car. To that extent I talked to Ant about letting me edit my own posts indefinitely in this thread. He agreed to take the editing requests upon himself so, while clunky there is a system to update now.
I will always appreciate your input on how to improve testing, so if in doubt, let it out.