Sure but that doesn't invalidate gated measurements. There's an accuracy level that is good enough. Gated measurements are good enough if one understands the limitations and uses them correctly. Which I think is what I did with my Alpair measurements.
I seem to remember seeing something akin, if not almost exactly that last year on one of the forums. Not sure which; I'll see if I can find it somewhere.
The pronounced null and peaks that show in the manufacturer and vendor data sheets are still missing, even with the "expanded" scale. It will be interesting to determine why . . .
As I've said several times, I'd concur. Nothing wrong with your measures with two caveats -the frankly excessive expectations of off-axis performance (it's not going to happen with a 4in out past 30 degrees. Would that it did) & that I'd be wary of assuming how accurate those are out past 30 with the gear. I said the same to X above, as you probably noticed. I've said the same elsewhere. The results in both / all cases might be better than indicated (not impossible) -they might also be worse (likewise). For the sake of interest, I asked a bod I know over at the University of Salford who does a lot of work in their anechoic chamber for his views. Same reaction. This is not a personal remark, or denigrating anything or anybody -it's just what it is.
What illusion? Gated measurements or ground plane measurements are described in numerous publications and software documentations like the REW or ARTA manual. Of course there are limitations but you make it sound like there's no way to obtain meaningful data other than paying a lab and that's simply not true.
Even data measured in a lab has its limitations. You can probably get more reliable low frequency data from a ground plane measurement taken at an empty parking lot on Sundays than from any lab in the world.
Yes, works great in a FASTish system. See post 194 or the "Cheap And FAST OB, Literally" thread, or the Nautaloss thread.
They might have changed it. Rare, but not unknown. I recall Troels Gravesen measured a pair of little ~2 1/2in Scan Speak units with his Clio setup and found them substantially better than the advertised data. Too different for just differences in measurement equipment; IIRC he speculated that the data sheet may have been using the data from prototypes while the production units were modified / slightly revised.
I have said multiple times that they are useful & provide meaningful data, as well you know. It's there in the posts above for all to read. I have simply pointed out that there are limitations to this as well. Period.
Please present your detailed, peer reviewed evidence showing this to be the case. The acoustic research department at the University of Salford, other such institutions & their commercial lab equivalents will no doubt be intrigued.
Regarding home measurements vs lab measurements with "Professional Lab grade equipment": I used to use very fancy microphones and preamps for acoustic measurements in a lab way back in the day. These were Bruel & Kajer, Kistler, etc... $2500 calibrated mic's (just the element), ultra low noise preamps, etc. IMO, what we have access to today for about $70 in the UMM-6 USB mic is perhaps just as good if not better than fancy lab mics because the preamp and DAC sits only 4 inches away from the mic element in the same housing and there is NO noise pickup in the cables, and it is one cohesive unit. It may not be as sensitive or have as wide a dynamic range, but for speaker measurement from 30dB to 120dB SPL, they probably are better than lab gear from 15 years ago. The anechoic chamber is what the home user lacks, and going outdoors can achieve some of that at the expense of increased background noise.
I can't possibly imagine what that means, but it sounds absolutely filthy.
Now, try to get yer most beloved 4" design sound as an elephant with stomach problems...
Regards
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Every anechoic chamber has a lower limit. The lower limit of a parking lot is determined by the closest boundary which can be quite far away. It's physics, no peer review necessary.
Now, try to get yer most beloved 4" design sound as an elephant with stomach problems...
Regards
You are giving the Vogon poets a run for their money. ;-)
There is a nice set of measurements of many many subs using the outdoor method that is well documented here: About The Sub Zone: Testing Methodology and Environment - Home Theater Forum and Systems - HomeTheaterShack.com
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