Close-wall speaker design

I've seen some people ask why their speakers sound too bright, thin, and lack of bass, or something tonal imbalance. And many replies suggest your speakers are designed to position close to the wall or somewhere with boundary.

I wonder what are the design criteria of close-wall or far-wall speakers?

If I understand correctly, the close-wall speakers will sound a bit increase at high, the bright tone, while the far-wall speakers will sound decrease at high, or warm tone. Am I correct?

And which one do you prefer?
Most speakers are not designed to work near a wall. The strong reflection off the wall will cause significant cancellation dip/s and raise the level of the low frequencies above that of the intended away from wall position. The low frequency boost can be equalised away to a fair extent but the cancellation dip requires handling in the speaker design. This can be done in at least 3 ways. The most common approach is to make the speaker shallow and wide in order to weaken the reflection. Not ideal but improves things. The second is to place the mid on the front, the woofer on the sides and arrange the crossover so that the cancellation dip for the each drive is outside the passband. This is pretty rare. Examples anyone? The third is to create a cardioid radiation pattern so that no sound radiates towards the wall. This is potentially the best performing approach but because it is done with sound cancellation it needs to use significantly larger drivers than normal in order to achieve clean SPL at standard levels. It is more expensive and complex.
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diyAudio Moderator
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If you go through and determine the reflections that each range will create for each driver/baffle combination, you should find the right motivations for designing the baffle to control a particular range. A near wall speaker isn't as simple as adjusting for tone since you can't very well equalise a cancellation, two times zero still equals zero.
AR-9 series speakers, could they be?

Yes the 200 Hz crossover over with an18 dB/octave slope looks like this was likely part of the design.

In more modern example, NHT 2.5 series?

Maybe not because the low 100 Hz crossover frequency and the 6 dB/octave slope on the midrange is likely to have a dip in the midrange passband.