First reflection is likely from the side walls, which I can't see clearly in the picture.
You can "see" the first reflection with... a mirror... From the listening position, the mirror will reflect one of the speakers and what's a straight line for light is also a straight line for treble frequencies.
Front to rear bare surfaces will also have some resonance, most likely in the midbass region (based on the dimensions you mentioned).
Absorbing material can be as simple as a blanket, a framed cross-stitch or decorative oriental scrolls. You can buy accessories that are made for audio use, but they don't have the WAF of a nice decor that also does the job.
In the extreme case you can cover the whole wall with acoustic foam, as I've seen in one installation. The result of that particular room was too "dead" for my taste. You could clap your hands near the speakers and hear no echo whatsoever - eery... Perhaps too sterile for simulating real-life sound retrieval, which is the ultimate goal of a home sound system.
Bottom line is that you have to experiment and determine for yourself when it's "too much of a good thing"... Invite some friends for a pizza and beer listening session and you'll speed up the whole process. That's known as the "attack of the audio nerds"... :-)
You can "see" the first reflection with... a mirror... From the listening position, the mirror will reflect one of the speakers and what's a straight line for light is also a straight line for treble frequencies.
Front to rear bare surfaces will also have some resonance, most likely in the midbass region (based on the dimensions you mentioned).
Absorbing material can be as simple as a blanket, a framed cross-stitch or decorative oriental scrolls. You can buy accessories that are made for audio use, but they don't have the WAF of a nice decor that also does the job.
In the extreme case you can cover the whole wall with acoustic foam, as I've seen in one installation. The result of that particular room was too "dead" for my taste. You could clap your hands near the speakers and hear no echo whatsoever - eery... Perhaps too sterile for simulating real-life sound retrieval, which is the ultimate goal of a home sound system.
Bottom line is that you have to experiment and determine for yourself when it's "too much of a good thing"... Invite some friends for a pizza and beer listening session and you'll speed up the whole process. That's known as the "attack of the audio nerds"... :-)