rolled fiberglass vs "batts"

[LSP]

Can anyone attest to the effectiveness of owens corning rolled fiberglass stacked in the corners, vs the "batts" that are wrapped in plastic, for bass traps.

The reason I ask is because I was going to purchase more rolls for the other corners in my small studio, and discovered that Lowe's and Depot didn't carry the Owens Corning rolls anymore, and the brand they do carry was shorter in height, and larger in circumference. This would mean I would have to purchase more of them in order to make an 8' trap. Moreover, the Owens rolls were tightly wrapped, which, after covering in muslin cloth, creates a nice looking trap.

It takes 6 of the owens corning rolls to create an 8' high trap, or 2 of the "batts" stacked to create 8'. As mentioned, the rolls seem to be much tighter, or denser than the batts, which seems to be just sheets of fiberglass, pressed together and shrink wrapped.

Trying to save cost, I went ahead and purchased 6 of the plastic wrapped batts, covered them, and placed them in the corners. Now, I'm thinking I made a mistake. Another member on a previous thread gave the opinion that the smaller in diameter, yet denser rolls, would out perform the larger in diameter, yet fluffier "batts".

Should I take the batts back and continue to search for the owens corning rolls?

Also, does it make a difference which "R" factor is used. I believe my previous rolls, and the current batts are 13. I chose them simply because they were cheaper than the 19 or above.

Thanks,
Marc

[SAC]

I might suggest that you read any of the 40,000+ threads on bass traps and the gas flow resistance or the density ratings for bass traps....and not focus on 'corner traps made of rolled thermal insulation'. (search on "Avare" and "bass traps" Read everything he says!)

Sorry, but its effectiveness at LF is not measured in acoustics in terms of R values or in units of rolls of thermal insulation. Besides, the R values you encounter in the stores generally apply to different thermal coefficients (thicknesses) of the same density. Be careful with this value, as it is not an absolute value and not the same as density which changes the compression.

If perusing the myriad bass trap threads, of which there have been MANY recently (read; posted over and over and over and over again), I think you might find that generally, bass traps benefit from greater depth of less dense fill!

Thus size (spacing from the boundary) matters and high density does not! That being said, they are most effective at the 1/4 wave length from a boundary and fill closer to the wall can help but becomes less effective as the sound velocity approaches 0 at the boundary. Thus an air gap of approximately 1/2 the total spacing from the wall works nearly as well as a completely filled space.

In your case, less compressed rolls are fine - and are probably an advantage, as they are most likely larger in diameter and more loosely compressed - a desirable feature - all other factors being equal.

All in all, you would probably save money by simply using lower density fill in framed corner traps rather than buying more volume and density than necessary. And with reasonable precautions (lest this precipitate yet ANOTHER 'is Fiberglas a carcinogen thread!) one could fill easily sewn cloth bags (with a plastic lining or light bags if you feel the need) with batts or loose fill fiberglass - or any of the readily available alternative fills available) and support them with a simple frame in the corner.

But whatever methods you choose, good luck.