Of course cost is a factor. I could have said "MDF is the most practical and cost-effective material". It's more acoustically opaque than using real wood, for example (I'm not referring to real-wood veneer but actual boards of cherry, pine, birch, etc.) Plywood is better than the latter because it's layered but it's still not as dead as MDF.

Alan

Alan Lofft,
Axiom Resident Expert (Retired)