PMC IB1's close to rear wall, is this O.K.?

It is hard to say if you are going to have issues with placing IB1s close to the back wall.
I have IB2 and they are approximately 4 ft from the back wall, in a room that is approximately 18X18ft of unusual shape with no corners, so I have no issues of any kind with bass, ASC tube traps did almost nothing positive in my room (I had a chance to try).
A friend of mine has IB2s less than 2 ft from the back wall, in a room that is approximately 1/3 smaller than mine, of classical shape, but he managed to get quite good performance without huge peaks and dips by treating the room acoustically (pair of 13” tube traps, acoustic panels on side walls and ceiling).

If I recall bass goes like this Spendor - Harbeth - PMC - Proac in increasing order. ATC is actually regarded as bass lean by most people compared to "average" consumer speakers that tend to be a little bass heavy (bass sells).

Shadorne, do you mean Spendor would be the most bass shy? Or is your scale based on quality as in Spendor has the best bass in general.
Thanks

Alun,

Yes indeed I was trying to give you an idea of bass strength...these are all good speakers including your existing speakers, selection being a matter of taste.