Originally Posted by markus767
At low frequencies wavelengths are longer than room dimensions. You don't get far with the classic mirror image model. You can't "break up" low frequency "reflections" by pointing your sub in a certain direction. Wavelengths are too big.
You can change the room modes affected by turning the sub. This may or may not help your frequency response at your listening location (i.e. who cares if the bass response is uneven in the back of the room if no one is sitting there). In my case, however, I didn't just "point it" in a different direction as I indicated before. I pointed it at a semi-circular cabinet (end table) largely creating a new dispersion pattern leading to what I imagine were multiple wavefronts colliding at the listening couch instead of two primaries from two parallel walls. So instead of huge dips/peaks where the two primary wavefronts align and cancel, I have multiple primary interactions competing with one another, leading to the overall response being evened out to relatively minor amounts from 150Hz to 21Hz with two dips at 55Hz and 110Hz that can be corrected relatively easily compared to the massive variations I had when I put the subwoofer in any other position in the room (often 8-20dB across the listening couch alone).
Turning the subwoofer or placing it at different points in the room would change the response, but the dips were still too large between seating locations at various frequencies. Using the rounded end table more or less as the sonic equivalent of a diffraction grating is what solved my room problem with the subwoofer. Given the huge variances before, I think the term "breaking up the standing waves" is perfectly descriptive as that's exactly what pointing the subwoofer at a curved reflection surface did for the room.
Ultimately, what are my alternatives for this room short of changing the walls in it as you seem to think is ideal? A DBA won't work because of the bookshelves and windows. You either use a room correction system (assuming it's not so extreme that it CAN correct it) including room treatments or alter the sound dispersion somehow where the problem is (either through bass traps and room treatments or altering the pattern so it's not a big issue at the listening location. I did the latter). And this is what I was getting at. If you have a real house with a real room in it and you want to set up a "home theater" that doesn't cost two arms and two legs, you have actual limitations you can't just build another room to solve.
The main satellite speakers in my room are placed to align with the projection screen edges and center, not in its corners which would cause the sound stage be ridiculously wide compared to the movie on the screen and potentially lead to all kinds of phase issues caused by the sheer proximity to two different parallel wall surfaces to the sides of the speaker.
Looking up see WTF a "flush mounted" "corner" speaker is, I'm getting images closer to this (http://www.lightsoundjournal.com/ima...ott_Photo2.jpg
) which is NOT what is meant by a "corner" of the room if you have to insert angled walls to make it work! That is clearly a special case and NOT AT ALL related to what I was originally talking about (90 degree corners of actual real world rooms, not custom built walls to flush mount onto).
My "home theater room" is in a house built in 1973 when home theater didn't exist. To do this so-called "flush corner mount" thing would require modifying or putting in new walls in the room, which again is beyond the scope of most average people's home theater rooms (in my case there are two bookcases at the ends of the room and window in-between. I can't just alter the room willy-nilly without consequences.
Read Toole and things should become clearer. I can't give you a lecture on that in a forum post when others need a couple of hundred pages in a book to explain it. Better sit down and read such a book. I've provided references. I'm afraid it doesn't get easier than that.
Here's a good introduction: http://www.wghwoodworking.com/audio/...production.pdf
I'll take a look, but it doesn't change the fact you're talking about something completely different than what I had in mind when I said "corner location" (as in an actual typical house 90 degree corner, not some odd shaped room or added walls).
It's not me not answering but you not listening, so I'll repeat: by flush mounting L and R in corners I remove very early reflections that cause imaging problems and spectral distortion. In other words, I prevent reflections from occurring because it's easier than eliminating unwanted acoustical energy once it is out in the room.
If that photo I linked is what you're referring to as a "corner" of a room, then it's small wonder there's a pointless argument going on here. I wondered what you meant by "flush mount". I should have figured you'd be talking about a special situation 99.9% of the typical home doesn't have or use.
Very likely. Here's just a random example from a user that posted measurements of L from the listening position. Note the excess phase group delay peaks (= non-minimum phase regions):
Other than "very likely" you didn't really address what I was getting at, which is how does the group delay from sub frequencies matter when the human brain detects the "tightness" of something like a bass drum not by the lowest frequency, but by the harmonics at much higher frequencies? Group delay at subwoofer frequencies are generally ignored by the human auditory system. This is why you can get by with ONE subwoofer instead of stereo subwoofers. The human auditory system can't tell direction (phase) of bass below about 80Hz and thus the group delay of the subwoofer is largely irrelevant. So AGAIN, what does group delay of the sub matter with a subwoofer placed in a corner location?
And what is this "random" measurement of a left speaker? What type of speaker? What kind of crossovers is it using (those greatly affect phase and group delay). Where is it located? That appears to be one speaker, not a subwoofer and satellite speaker in two different locations. I don't know what that graph has to do with the question of putting a subwoofer in a corner or not when it's crossed at 80Hz and has insignificant output above 160Hz.
So what were you talking about if it wasn't room reflections? Standing waves from the back and side wall?
I had two things in mind. One is clearly stereo imaging. Unless your screen is wall to wall in your home theater, putting speakers in the corner of TYPICAL REAL WORLD ROOMS is going to cause mismatches for things like panned dialog effects and most music tracks played are going to have extremely wide sound stages for in-phase stereo sounds. The other is yes, room interaction. Typical speakers are not designed for corner placement (let alone using real world unmodified rooms) and just putting a typical loudspeaker in a corner location will probably NOT sound good. It may be impractical as well (real rooms have things like furniture and doorways and all kinds of things in them that build-to-order rooms typically do not).
Frankly, I think you knew full well what I was originally talking about and you still decided to engage in an argument anyway, knowing I was referring to normal rooms that do not have non-parallel wall setups. This is akin to using something like a semi-circular room (rounded on one end only) for a home theater. Yes, that might be nice for removing standing waves from the equation, but how many houses have rooms shaped that way?
So I still don't follow why putting speakers in a room corner is "the absolute worst possible place to put a speaker". It can be one of the best IF correctly implemented.
So you're taking a general statement about typical home theater installations and twisting it until it fits a pretty large IF? I also can't help but notice you purposely left off the "among" part in your quote as it makes it appear to say something I didn't really say (implying THE absolute worst and instead of one among many of poor places to put (clearly typical) loudspeakers in a typical room).