Speakers made for close placement to front walls

Speaker placement will be all the more important with tuned port speakers, which have their own non-linear resonances. You would probably be better off with a sealed box: a design which will be more forgiving on placement.

Placing speakers anywhere close to a rear wall will boost base response by a few db, but will also cause a frequency dip from rear reflected base frequencies that cancel the forward radiating energy. This can be as much as a 20db hole in your frequency response in the base. As you place the speakers closer to the wall you will move this interference upwards in frequency and make it more evident. (This problem does not affect mid and higher frequencies as they radiate almost entirely forward from the speaker and not backwards)

If you can get your speakers 1.8 Meters from the rear wall (measured from front baffle) then you will have a dip at 50Hz ....this is a good distance to use for linear sound quality but obviously impractical in most rooms! It also means you lose a few db in base response as the reflected energy does not add to the forward radiating energy.

If you place your speakers at 50 cm from the rear wall (measured from front baffle) then the problem will occur at 170 Hz: a problem!

At a mere 25 cm from the wall then the hole in LF frequency occurs at 340 Hz: a definite problem!

Generally this means that almost no practical home speaker setup will be immune from this problem; a fact which many audiophiles are unaware of, but one of the principle reasons people keep struggling with speaker placement. Of course, some source material brings out the problem more than other material, but it is hardly practical to keep moving speakers according to what you are listening to!!

The formula for where your frequency dip/cancellation will occur is 340 / (4 * distance from front baffle to rear wall in meters).

A base trap on the wall behind the speakers can help but the only way to completely eliminate this problem is to soffit mount the speakers - just as they do in studios. This is what I have done at home.