Um, I'm fairly certain Ethan didn't mean that.
I've been involved in a fair bit of low frequency absorption testing with devices in lab corners at this point and I can say, conclusively, that it won't be standardized. The reason is the results vary so widely, even with the same devices in the same room, on the same day (and so on...), but in different corners. Suffice to say, the absorption of any device in a corner cannot be quantified
absolutely in the contexts of a studio room. Whatever Ethan measured in a corner in terms of Sabins is most assuredly not applicable to any studio room.
That's not to say the results are useless. But the purpose of a standardized test is to get standardized results. Over the official frequency range - 100 to 5000 Hz - that is possible, regardless of the mounting used. But once you get into the low frequency range, even the big reverb chambers go modal. So, placing things in corners will never produce absolute results.
To say that because a device measured extremely well at 80 Hz in one corner configuration means it is universally useful at that frequency in all possible corner configurations is false. Especially since the studio room in which the device might be applied may not even have a problem in that range to start with!
Of course, I'm probably just putting things a different way. But the corner tests have always worried me. The research I had a hand in at
Auralex was enough to make me pull all the references to corner testing off the website a while ago. It's just futile to take part in something so erratic when the point is to remove as many variables as possible.
Anyway, the other thing I would mention is that there is an
ISO standard for measuring absorption at very low frequencies. The only company using it to quantify the behavior of their "traps," that I'm aware of, is
RPG. There is a rather big caveat to performing the test - the construction of the room is very exact. I.e., you can't perform the test in any ol' reverb chamber.
RPG's also done LF testing in a large impedance tube. This would also be an acceptable method, but much more involved than the reverb chamber method. Point is, if the companies that make "traps" are keen on quantifying their products in a manner that can be compared to other products tested other places, they might look into following in
RPG's footsteps.
As it stands, if the facilities aren't available for performing the
ISO or impedance tube tests, the very least all the manufacturers can do is test their products in the standard mountings - A and/or E - and publish the results over the
official range of frequencies. If other mountings and/or lower frequencies are tested, I would see two choices:
1. Disclaim the poop out of the data since they aren't official. Corner mounting is not a standard mounting method and there isn't a lab out there that's been approved to provide
official test results below 100 Hz.
2. Publish the results in the contexts of a research paper or something other than "official" test results.
Of course, that assumes the "traps" in question are of the panel variety. It's been pointed out that the A-mounting testing on
Auralex LENRDs was errant because they are actually triangular devices that are meant to be physically placed in a corner. This does introduce a degree of complexity, but nothing that cannot be overcome. Testing devices such as those in a manner that reports Sabins/unit, but with the mounting staying true to the standard, would be one way to help make things more comparable. I would imagine that standing the devices upright, spaced appropriately in the chamber, avoiding placement that came too near a wall, corner, the mic, etc., would give more useful data than any corner test. Now, the argument then would be that none of these methods reflects real-world usage. And my response to that was that real-world usage is not what's meant to be addressed with standardized testing. If that were the case, the auto manufacturers would take their cars out on the real streets of America to obtain their MPG ratings. But they don't. There has to be a standard method that everyone can use some vehicles can be compared side-by-side without question as to how the results might have been doctored. That's what happens in this industry when manufacturers stray from the standardized absorption tests. The results may look great on paper, but what they
really mean is completely unknown.
My $0.02.
