Al,
Enjoyed your good thoughts on this. However a given frequency of sound (vibrating air molecules in a wave lenghth) does not care how many inches, meters or hand spans, for that matter, it is away from any given surface. When a surface reflects more vibrating air molecules (sound waves) at the same frequency of vibration into other parts of the room which have identical vibration frequencies, at an identical decibel level, they will cancel each other out, thus creating a null or no sound at all at the frequency played.
Conversely, when a given frequency builds up with more identical frequencies around it but at different decibel levels, you have a peak at that frequency. Bass boom is the most common result of this. A given bass frequency, such as 40Hz builds up in the corner of a room, and, at the speed of sound, a pulse of the same 40Hz frequency follows behind the original 40Hz frequency trapped in the corner of the room for a nano second. Thus, one 40Hz sound joins in with another identical 40Hz sound buy at a slightly lower decibel level which makes that 40Hz sound louder (hence a boom is heard).
If the room's dimensions, location of the speakers in that room, and the sitting position of the listener are all uneven to each other (not dividable by 2, be it a metric measurement or English measurement, the odds of cancellations, nulls and peaks are greatly reduced or tamed.
All frequencies have a precise wave length. The lower the frequency of moving air molecules, the longer the wave length of the sound heard. Since the room in which the sound is produced has nearly an unlimited number of wave length receptors (walls, ceiling, floor, furniture, etc.) and the speakers produce nearly an unlimited number of wave lengths from approximately 32 feet (deep bass) to less than an inch (high treble), there is going to be thousands of ripples in the sound heard that will be from a 1/8 of of decibel to as high as 30 decibels referenced from a straight line flat room response. This, of course, is dependent on the frequency and its relationship in the atmosphere in the room and its reflection of a large number of surfaces before it drops below a decibel level (sound volume) which cannot be heard.
In my former discussion with you, I spoke of dimensions of an ideal size room and then the dimensions of the room in question (10X18X8 feet). Since we were dealing in feet and not the metric measurement system, I used feet to express what's so regarding said rooms and how sound within those rooms would likely be if the room was not treated and the sound from the speakers digitally equalized to counter room caused sound problems. We can reduce feet to millionths of an inch if you wish and do the same with meters, too. The method of measurement is not important. What is important is that the measurements from one surface to another in relationship with ones speaker's positions and the location of one's ears at their sitting position while listening to music being reproduced from said speakers is what is very important. If the primary large surfaces of the room measurement numbers end up being not dividable into each other or by 2, from where one's ears will be while listening to music the decibel rise and fall of every frequency produced will be less molested or disturbed, thus allowing for a flatter frequency response within the room which results in hearing the sound produced by the speakers and not badly altered by the room before the sound gets to one's ears.
Once again, I'm not making this up or working from some sort of placebo driven audiophile hype. I'm simply remaining within the realm of the science of AUDIO acoustics working within known and proven math configurations. If you wish to use meters in an 10X18X8 foot room with concrete walls, and from there determine where you should sit, place speakers, install room treatment, and at what frequencies to equalize your speakers to correct for room issues using metric measjurements, then be my guest. Using fractional inches, complete inches and feet will get the same result. You live where the metric system is used. I do not. I live where the English measurement system is primarily used for commercial products and home construction. It matters not which is used, as converting the English measurement system to metrics, and using the equal dividing rule of 2 or 1 into 1 as previously detailed will get you the same exact ideal results. And, like I said previously, the person who asked about his room in reference to feet measured tells me to give an answer in the English measurement system (feet, inches, etc.). Had I responded with a conversion to the metric system, the person who inquired about his room would probably not understand what to do or how to measure in that manner as his tape measure is obviously in feet, inches and fraction of inches and not meters.
Regarding your comment on "single frequencies, not frequency bands", be advised that if a 40Hz tone slams into another 40Hz tone at the same time and at the same decibel level but one of the 40Hz tones came from the speaker and the other from a reflection off of a wall from a 40Hz tone played a micro second before the next 40Hz tone played from your speaker(s) at the exact same decibel level, you will not hear that 40Hz tone. When both 40Hz tones collide, they cancel each other out and no sound is heard. This creates a null in the sound at that frequency for as long as that frequency is played by your speakers (such as long 40Hz note from a bass pedal of an organ). This is true of all frequencie...period. Now, Al, what happens when several frequencies close to one another, say from 80 cycles to 40 Hz are being played by your speakers at an 80dB sound pressure level at your sitting/listening position. These frequencies of moving air molecules first hit your ears, then a micro second later those same frequencies of moving air molecules (sound) are hitting your ears by being bounced off the floor, walls, ceiling, etc. and slam into the same frequencies hitting your ears. Since said frequencies are not hitting each other at the exact split, micro second, but otherwise are micro close, they will not cancel each other out, but they will reduce their decibel level, thus causing a dip in the sound frequency from 80Hz to 40Hz. So, Al, sound can be effected by the room not only at a give narrow frequency (say 40Hz or 80Hz to 40Hz in this example) but also many related frequencies near each other, thus causing dips and swells in the sound caused by the room. Therefore, this is where room treatment comes into play to control the large dips and swells in the frequency band affected. EQ is also ideal for very narrow frequency band adjustments such as a large 8dB spike at 81Hz to 83Hz that annoys and should be reduced by 8dB of sound pressure by reducing the current at thpse frequency to cause a -0- flat response in the room at that frequency. There is also EQ which can manage large swells and dips, too. Keep in mind that anytime you equalize any frequency to sound flat where you are sitting and listening to music, it will throw out a molest a flat frequency elsewhere in the room which was previously flat. So, make a 40Hz dip of 5dB become flat to 0dB where you sit, and you have taken a flat area somewhere else in the room and caused it to dip 5dB at 40Hz. This is acceptable so long as where that occurs no one is sitting to listen to music. This is why it is very difficult to equalize a home theater to a flat room response to all seated in the the theater. One can only "average" the frequency response in all seat areas for, at best, a compromised EQ'd room. Therefore, the person sitting in the middle front row of chairs gets a flat + or - 3dB frequency response from 20Hz to 20kHz at 75dB at that seat. The person in the second row of chairs, in the right side of the room chair may hear a + or - 9dB frequency response of the same sound at a slightly decreased decibel level (because they are further away from the speakers and reflections form the walls, ceiling and floor molests the sound while listening to it in that particular theater seat.
Got all of that? In short, acoustic science and engineering often boggles the minds of those who even have a PhD in that field. It seems like one is chasing their tail when they get the mind wrapped around what is happening acoustically due to the dimensions of their room, position of their speakers, where they sit to listen to music and where many other objects are positioned in the room, plus if the room leaks air into other areas outside of the room and if the interior walls are rigid (concrete) or flexible (thin sheet rock).
Finally, I advised you of my listening rooms dimensions, what's so in that regard with your room? Just curious.
"Nuff said' Doc
), I quickly learned to hate the big tower speakers (expensive from a very well known brand) that had served me so well in a large room. They just didn't work. I am much happier with my current setup, even though that is not a brand recommendation.... Speakers are a very personal choice.
