The Cork you mention is non linear and effects only the uppermost frequencies. You're better off using Owens Corning or Johns Manville fiberglass. Both companies make high density products specifically designed for this purpose.
Their materials requires only one inch thickness to be effective well into the lower midrange frequencies. Applications of up to five inches are linear into the lowest bass region, but unless you are really dedicated, one or two inches is sufficient.
Covering the panels has been discussed here many times, begin with acoustically transparent cloth that suits your taste and either cover the entire wall, or begin with just the problem areas.
To find the very first point of reflection, have a friend hold a full length mirror against the side wall. Viewed from your listening "hot spot," and moving the mirror until you see the speaker's reflection. This is the first reflection point.
The two acoustic companies links follow:
http://www.owenscorning.com/around/sound/acoustic.html
http://www.jm.com/wallcoverings/index.shtml
Their materials requires only one inch thickness to be effective well into the lower midrange frequencies. Applications of up to five inches are linear into the lowest bass region, but unless you are really dedicated, one or two inches is sufficient.
Covering the panels has been discussed here many times, begin with acoustically transparent cloth that suits your taste and either cover the entire wall, or begin with just the problem areas.
To find the very first point of reflection, have a friend hold a full length mirror against the side wall. Viewed from your listening "hot spot," and moving the mirror until you see the speaker's reflection. This is the first reflection point.
The two acoustic companies links follow:
http://www.owenscorning.com/around/sound/acoustic.html
http://www.jm.com/wallcoverings/index.shtml