downfiring a sub/seal it "for lows" in a small cabin goes around alot but it's bs lol. Flip the sub. It honestly dosn't matter as much where the sub is at in a small cabin vs a bigger one but you shouldn't have the cone too close to anything as that sort of gain is better for upper end.
ahhhh. not necessarily. Due to loading factors, the down-firing of a driver, depending on the type of down-fire(slanted, constant area) under the driver, will, much like having the cone closer to any object, aid in the low frequency response IF IT IS DONE CORRECTLY. But having it just down-fire to say a floor with no other resonance barriers within 2 ft at most of the designs driver output location (not port output for this case), will have such a small effect that it will be inaudible. The main thing that it changes is the phase response of the passband, which in turn can cause possible cancellation of certain frequencies depending on the out of phase areas within the passband along with the frequency band of those out of phase areas. Meaning that if it were out of say a greater than 90 degree phase(for sealed designs, which anechoically cannot happen-this is only for boundary effects) for only a 3Hz band, then also depending on the rest of the phase within the passband of the system, it will determine the cancellation effect involved when playing multiple tones, such as a music recording.
What that says is, when down-firing a design, or even trunk loading it through a blowthrough area without incorperating that area as part of the loading effects on the design, it will have an effect either audible or not on the LF response EVEN THOUGH the most part of the LF band is acoustically smaller than the cabin area( a small on as the example).
I see what you are saying, but there is much more involved than what you can "hear" in an audio system. Take for instance a HF response in a larger room vs a smaller room. You can noticably hear the difference in phase shifting at specific positions causing cancellation not even related to the physical part of the design other than directivity. But put it is a smaller room that is in fact acoustically small compared to the passband used, and you will not notice audibly the phase changes as easily, though they still happen. Ever put your head closer to the window and hear the bass increase? Or into a corner due to gain? This is the same effect as in phase response. Most of the area outside of a 45 degree span on either side of the 0 degree listening position is out of phase from the systems response, and has an effect on audible and inaudible changes. This happens even in a vehicle with sub frequencies. Its just less noticable when two things occur.......1. you base it on a single listening position, and 2. you have the acoustical pressure(spl) increased per square inch to a point where the resonances are camoflouged into the space due to timing effects and intensity over time.
here is an example: a speaker is in front of you, playing at a certain level where you can hear it at a certain db level as well. Now, say you increase the distance between you and the speaker. What happens to the dB levels? They decrease due to time and distance over intensity. Now, what happens when the level(volume) is decreased? You hear it also with less dB output. Two factors that create a major part in sound reproduction based on propagation. These still occur in any given space regardless of size. But lets say you put resonant walls on each side of the speaker between you and the speaker where the mirrored out of phase imagery of the signal reflects directly to the listener? you increased the dB level based on resonance even though it took more time to get there as a resonance, the loss in dB that is an important factor in resonance is considered to be nulled greater than a -60dB level. So, if that resonance hits you before the original signal decreases to a point greater than -60dB, than the dB level at the listening position is increased by the dB level created from the reflected signal. So, in a vehicle, this reflective dB increase happens so frequently, that an audible difference if pressure and intensity is increased based on power levels, is less noticable from so many of these reflections occuring before the original signal is greater than -60dB over a specific time(usually measured in ms).
So, I can see how you mean that if the size of the cabin is small (compared to the frequency), that placement and such are not a factor. But when time constants and intensity are involved, they become a huge factor, especially when dealing with stereo imaging, but for sub frequencies as well even though they span over a greater distance. So, yes, the placement can be less sensitive over a smaller area based on time and distance, but still can have an effect on the sound whether audible or not, such as the cancellation effects caused by phase changes, which are based on placement and positioning as well. And since those phase changes can effect the response output, then it directly related to the frequency response of the system.
I typed this really fast, so I apologize if there are mistypes or it becomes confusing. I might have jumped around a bit, but the concept should be that regardless of how intense the effect is on any change in the physical part of a design within its environment, it still can have a huge factor or role on the outcome of the response if not carefully considered.
