There are two basic issues in rooms: absorption and reflection. Acoustics panels are usually absorbers sucking up sound, some are diffusers (add more reflections). Most home listening acoustic problems are related to too many similar reflections off large surfaces like walls and floors and windows. All of these emphasize particular frequency bands. Bass problems are different, usually related to the room dimensions of the room our speakers are in. Few rooms can accommodate a 32Hz note (that wave length is well over 30 feet long so you'd need a minimum 30 foot room dimension) but the energy of that too long wave is still in your room and causes all kinds of issues at harmonics (64 Hz, 128Hz etc). We use bass traps to absorb these "extra" low frequency waves so the original flat response from the speaker is not covered up with room modes and standing waves.
Because the materials used to address our two basics (absorption and reflection ) are effective only in select portions of the audio band and to a different degree depending on materials used, we need to know "where" in frequency our absorber works in and how much does it absorb? That's why its quite complicated and we all have varied results because we usually don't know how much absorption or reflection to use and where? That's why there is such a mix of results when we compare notes.
The Dynaudio quote earlier in then thread is ridiculous, written by a marketing person no doubt. DSP solves absolutely nothing in the acoustic realm. You cannot fix acoustics with an electrical solution any more than you can fix electrical problems acoustically. What DSP "room correction" does is sum all the direct + reflected audio at your [measurement mic] location and then apply an opposite signal to the original. When this opposite or corrective signal is added back to the original direct+ reflected sound [based only on that one mic location or an average of multiple locations] this new sum looks better in linear frequency response terms. Sort of the noise cancelling headphone idea: add the unwanted noise back in at 180 degrees and its magically gone! . It cannot address delays, or echoes or long reflection times, phase linearity of the speaker, source issues, etc. These DSP fixes are band aids on wound that never heals, but they can still be helpful. It can take a system from unlistenable to listenable. It cannot take a listenable system and make it great. Basically you are changing what's theoretically right (the direct sound from good sounding speakers) based on "what's wrong" (the reflections of these speakers in the room). Now everything is changed and undergoes the same room/reflection based changes it always did.
Since we rarely hear direct sound, most of us are unfamiliar with what our speakers actually sound like. We can find out by taking our speakers to a boundary free environment like outside in our back yard and pointing the speaker up at the sky: boundary free playback. This is why speakers usually sound better in a larger room- the boundaries are further away. So we are always stuck listening to a sum in our room of direct + reflected energy. This is why I find speaker demos so useless, for if you buy "what sounds good in my room" you are buying a speaker with the opposite problems of your room! Unless you have a great sounding room. The "home demo" is more about your room than the speaker, nearly 100% of the time. Its really more about what your room will do to the speakers than the other way around.
Room correction DSP banks on the idea that the NEW sum (direct +reflected+ corrective DSP audio signal ) sounds better than the direct + reflected signal alone. Sometimes it does. But your ear/brain is way more sophisticated than this simple new sum of injecting a "fixer" signal into what already sounded good but was messed up by your room. Sit closer to the speakers, reduce the level of reflected energy at your ear vs the direct sound. (This is exactly the idea of nearfield monitors: sitting closer to speakers reduces the amount of "room sound" at your ear compared to direct sound.) Fix your room so it sounds good. But most importantly, find the places in your room that sound better than others. I often find people shocked when i walk in, move the speakers one inch and everything is better. They look at me like is magic or something. People rarely move speakers around in a room to experiment how different it can sound.
So while DSP can help, it can make a really awful situation better. But it's a major compromise. No DSP is as good as not having the acoustics problem to begin with! Solving acoustic problems with acoustic solutions is the unavoidable answer and we all hate the idea but its true. Now if we could just know the target it would help, right?
Brad
Lone Mountain Audio -ATC USA.
