Please, no misunderstanding, my tone here is entirely amiable.
Bosso, you're moving too fast for me*. This bottom octave range is fascinating, and to that end ... great contributions such as many of yours over time, have really inspired me to learn more and more. But you made bold statements "tossing theory out on it's ear", focused pointedly on Carps graphs, posed questions about specific behaivior that doesn't fit the known physics, claiming your theory does explain it, soliciting answers otherwise. I answered them, *now you want to move on without further discussion? .. without even finishing your
contention about Carps graph.
I've been around long enough to know how you, Bosso, would have reacted if a contributor did that to you.
I'm far from the sharpest dude around here, but I do attempt to always maintain a positive manner of comportment. No ******** Jedi Mind Tricks
here, like Sweet Brown says,.. there's no time. But yeah, I'd like to discuss both your room, or any room all in order, but we've not yet finished with your initial Carp example, and the very thought provoking position you've taken.
You, using Carps room, measurements and graphs, because they aligned perfectly with your theory, etc. You stating "in Carp's thread about my theory for room gain. I've tossed PVG out on it's ear and focussed on actual data
", let's focus on those contentions prior to moving on. Like I said, I'll be glad to move to your room's examples too, but I took exception to your new theory, you posed a few questions and I answered them. I'd appreciate wrapping that up first. If not I understand, I'm in no position to steer this thread.
One of us wasn't correct. You stated you didn't want any of this feel good BS,...where everybodys right, etc. I aggree.
Also, you claim this theory allows you to accurately predict a room gain profile down into the bottom octaves without inclusion of a room's dimensions.
I disagree. There's no way, unless there's more you've yet to disclose. If so, please do.
Originally Posted by Ricci
Note that modal issues stop below a certain point but that leaves a whole plethora of other things that can still affect the energy in the space below that point. The structural makeup and transmission losses of the room boundaries (perhaps even from one corner to the next, brick walls in one versus wood in another for example) differences in shape, distance, size and positioning of the subwoofer from the LP and even the furnishings close range can all cause change in the response delivered to the LP below the modal region. Generally the differences are smaller than what you would see above the modal region but they are still there. For example when LTD02 mentioned large openings such as hall ways and ducts acting as giant Helmholtz resonators and messing with the response down low he was generally scoffed at but I am convinced this behavior does occur. I believe Tom Danley has commented on seeing effects of this as well. How much of an effect it has in the real world on most systems is debateable but it could have some effect depending on the circumstances. I am convinced that walls and floors can have sympathetic diaphragmatic movement that can cause resonance issues and cancellation of energy in the very deep bass as well.
I agree, and mentioned all this and explained Carp's effects Bosso interpreted as unexplained. I explained and accounted for the change that he pointed out and insist don't occur within the current theory. If he's commented about my explanation to his theory and Carps example, I've not seen it.
Originally Posted by Ricci
I have not taken the time to read some of the papers LTD02 has linked which he seems to believe explains the behavior below the modal region in typical rooms.
I haven't either.
Originally Posted by Ricci
To my eyes there are some things going on below the modal region that are not readily explained by a simple PVG theory
emphasis mine. I don't know what you mean by simple PVG theory.
That segment of my post you quoted, is accepted, widely understood, and none of this falls outside those aspects of the known physics.
"The acoustic gains elicited by PVG (or whatever term one wishs to call the results of that phenomenon), cannot begin within the modal range. Any acoustic gain enjoyed within that range is either boundary gain, or simple superposition effects. Moving a LF source can easily excite stronger modal interaction, less modal interaction, stronger panel resonances, or less panel resonances. The distances between two boundaries, determine the standing wave/modal freq therein. Anything less than a fully rigid boundary, interacts with that distance in a less than ideally well defined manner.
I'm guessing over time Bosso had witnessed other odd behavioral examples similar to the Carp example he cited. However, nobody commented upon me explaining what could easily account for the odd behavior Bosso's cited. It is interesting, absolutely. But inexplicable? No.
About the "sympathetic diaphragmatic movement", I contacted you long ago about this, as I saw it in some of your measurements. I recognized it, as I've seen it myself, in my room. Jordan, aka Krypt**, also discussed this with me and yeah, these boundary impedances are absolutely a factor. Any energy moving such a panel is detracting from the SPL experienced at the LP.
And perhaps most importantly, yes, re-locating the LF source exterts a varying amount of energy, via selective mode cancelation/excitation. The entire point behind multi-subs being the path to bass bliss; changing the modal interactions. Put 'em all up front, they're going to drive that length mode maximally. Spread them out, lessens the effect.
Is this thing on?
I think most just gloss right over these long, bordering on self indulgent posts. But I read every word of the mega posts, so I know some cull all they can.
**may he rest in piece, I loved the guy, we PM'd all the time, and I wish I could share all the variety of things we discussed, what an amazingly inquisitive dude, he's truly missed. In Nascar, there's cookie cutter 1.5 mile tracks. Well, I suppose there's cookie cutter AVS'ers too. Jordan, was anything but.
Sincere and amiable thanks