blackhawk1928 :
Well...on the system I'm talking about, the sub has a cut-off at 200hz (yes I know its high). and I've got another sub also. When I make the phase to reverse, the bass is extremely concentrated in the front corners and the middle gets almost no bass, while when phase is set to normal, the bass is much more equally distributed around the entire room.
that is exactly how it is supposed to work.
if you have lots of acoustics on the outside perimeter, then flipping the phase will make the inside of the room more acoustical.
it is simply a matter of in and out, and where the in's are as well as where the out's are.
yes, the pressure is going to be in the corners again..
but
when two soundwaves come into contact with eachother, they can cancel eachother out..
or
they can increase in amplitude.
it should make obvious sense that the waves making contact in the middle of the room are touching eachother in a way that is canceling out the sound.
thereby flipping the phase, those soundwaves would then do the opposite.
accumulated pressure is and remains accumulated pressure within the room.. that fact can keep the corners 'air-y'
and the only way to move the pressure someplace else is reverb.
sometimes the reverb isnt powerful enough to stretch out long enough that is needed to pass the corner and continue into the middle of the room.
it is a jigsaw puzzle without visual indentification.
but
you can kinda get a glimpse yourself if you realize that the cone pushes outwards and the air is like a gelatin.
the wave will go out in all directions, and the center of the wave depends on the dustcap.
the outside of the wave depends on the shape of the cone indent.
some speakers have a completely flat cone (some old precision power subwoofers)
and even still, some subs have a much less curve.. like the jl audio w7
megamer would be right to argue when the problem is tickled ears from too much pressure.
decibels are not the same as wind that can blow out a candle.
the difference in size is humongous for sound pressure.
some speakers can spit out decibels without moving much at all.
and those speakers rely completely on the tune of the box to play lower notes.
sometimes these subwoofers dont have the box tuned right, and the subwoofer cone belches in and out (and is often pushed extra until the speaker bottoms out - or the voice coil frys)
this leads to the pressure problems.. and a whole lot of bass you can feel, as it rattles the windows.
some people consider an elegant system to be one that plays all the notes, but doesnt do it with a lot of window shaking power.
this means much much bigger boxes, and can have the benefit of less amplifier power.
pretty much how they did it in the 60's and 70's
but
i think the 70's introduced more speaker cone excursion, with enough that could rattle a window.
probably those giant paper 15 inch woofers with the 'newer' foam surround instead of the paper accordian type.
and then there was still people who had 15 inch woofers with the accordian surround, but there was more ability to move in and out.
some people went to theater type speakers (or concert speakers) because they were larger and could play the bass to keep up with the competition.
then in the 1990's..
speakers like cerwin vega really pumped up the box to speaker cone excursion ratio.
they would belch out bass.
then in the mid to late 1990's the dedicated subwoofer came out for dolby digital.
the industry has been pushed forwards towards the dedicated subwoofer ever since, and it seems like only a rare few ever look back.
i tell people pretty quick and simple.. no matter if your room has 15 inch woofers for the front/center/rear speakers.. the dumbed down audio mastering is still going to put some bass on the LFE channel.
it could be a copy of what goes onto the front or center channel.
and
it could also be something specific to make your room shake.
it should be expected that one day we will have the proper 12 or 15 inch woofers in every single speaker, and there will be tremendous bass that is positionally accurate.. and there will still be 1hz - 20hz (or is it 1hz - 10hz ?) from a very large speaker, or an array of speakers, to specifically build pressure in the room.
it isnt necessary at all when the main speakers are given all of the audio.
and any LFE effects would then be completely digital FX designed to add thrill to the experience.
weaker systems can appear to raise the floor of a room.. kinda like a 3d effect, but done with pressure.
stronger systems can make the floor appear to fall.
if there is a system put in place, the floor could be tilted front to back .. side to side .. back to front.
this could be really cute when watching some jet pilot do manuevers.
or
imagine the floor dropping every moment when the 'bullet time' was activated in the movie 'the matrix'
this is kinda far away.. because people need better dedicated listening rooms.
drywall just isnt going to cut it, as it will crack and bust to be remaining as an embarassment.
concrete works.. and maybe some blocks that have had their inside wall drinking glue.
maybe some type of fiberglass between them.. but i would think the fiberglass would crack too (just not as quick as drywall)
dedicated listening rooms of such magnitude require either going into the basement.. or choosing somewhere in the middle of the house, and put some jacks under the area to support the concrete walls.
but
concrete cracks too.. eventually.
plastic would be awesome if it didnt vibrate.
carbon fiber would vibrate too.. unless you did lots of layers, and that is too expensive.
acoustic paneling isnt going to help in this situation.
the acoustic paneling will not drop the pressure in the room without adhering to the soundwaves and their phase.
you have to realize that there is wind (like from a fan) that needs to be pointed somewhat precisely to get the wave in opposite phase to come into contact with the wave by the acoustic panel.
flat panels wont do it unless they are aimed in all sorts of crazy patterns.. and expect to lose as much as 3ft - 4ft per wall.
diffusion panels can be designed for a specific frequency.. but there is no way of them knowing how big your room is and where the panel is going to go so that they can design the shapes perfectly.
a single soundwave of 80hz is false.
there will be other soundwaves bouncing into the diffusion panel.. and if those soundwaves are 80hz too, then your chances are higher.
but
rooms dont all work like that.
since acoustic panel sellers dont openly advertise their willingness to help people with their room size and frequency.. one could assume that those details are private.
either private for 'industrial' use.
maybe private for 'commercial use'
or
downright private to force custom installers to make their own.
there are waves bouncing from one wall to the opposite wall.
waves bouncing from one wall to another connected wall.
waves bouncing from the floor to the ceiling.
waves bouncing from the wall to the ceiling.
if you wanted 'custom' help..
they would need to know where exactly the panel is going to go, and what soundwave pattern is touching that area of the wall.
that is the only way to do it correctly with perfect results (especially without any reverb).