He does say "without seriously affecting other performance variables"...:daydream:few rules of thumb: Stuff small enclosures – those with up to about 3 cubic feet of internal volume or less – with 1.5 pounds of fiberfill for each cubic foot of internal volume and you should get about a 30-percent increase in box volume without seriously affecting other performance variables. For larger enclosures, add stuffing at a rate of approximately 1 pound per cubic foot and you should get a virtual-space boost of about 25 percent. One thing's certain: You'll impress the **** out of your friends at the art gallery and bistro.
You can expect excursion to increase as the effective Qtc drops. That could be a benefit, or a detractor depending on the driver, power on tap, and bandwidth you're looking at. Group delay should flatten out a bit and that's the important part. When it comes to group delay, high or low isn't as much of a concern as variation is.Okay...cool!
Now I have a second question. Stuffing up to 1.5 lbs per CF makes the box look bigger - which is a good thing. After that, diminishing returns and too much is definitely not good. What's happening with cone excursion and group delay with optimal fill? Does it remain unaffected? In other words, is it all good until the point where box resonance starts to rise again due to over fill.
Also, is it worth putting closed cell or open cell foam in a sealed box you plan to stuff at the 1.5 lb rate?