If you imagine the speaker rocking back and forth a bit in reaction to the woofer's movements, you can see that it approximates an upside-down pendulum. The most effective place to add mass would be on top of the speaker.
I have had best results with a solid mass rather than with say sand or lead shot. But a solid 25-pound lump of lead is hard to come by. On the other hand, it's pretty easy to get a 25-pound bag of lead shot at a local sporting goods store that sells reloading supplies.
Put the 25-pound bag of lead shot in a heavy-duty zip-loc bag, and give it a turn or two of duct tape so that it makes as neat a sausage-shaped bundle as possible. Then put the zip-locked shot bag into a thick black sock. Tie a knot in the end of the sock. Then put the socked, zip-locked shot back into another thick black sock, knotted end first. Tie a knot in the second sock as well. This will give you an environmentally friendly, visually acceptable 25 pound weight you can position on top of the speaker cabinet (tuck the "tail" of the sock up under it for best looks).
This will help deaden panel resonances a bit, and the added mass will lower the natural rocking frequency of the upside-down pendulum to, hopefully, below the audible frequency range and improve the imaging a bit.
I have no useful experience with resistive loading.
Best of luck to you!
Duke
I have had best results with a solid mass rather than with say sand or lead shot. But a solid 25-pound lump of lead is hard to come by. On the other hand, it's pretty easy to get a 25-pound bag of lead shot at a local sporting goods store that sells reloading supplies.
Put the 25-pound bag of lead shot in a heavy-duty zip-loc bag, and give it a turn or two of duct tape so that it makes as neat a sausage-shaped bundle as possible. Then put the zip-locked shot bag into a thick black sock. Tie a knot in the end of the sock. Then put the socked, zip-locked shot back into another thick black sock, knotted end first. Tie a knot in the second sock as well. This will give you an environmentally friendly, visually acceptable 25 pound weight you can position on top of the speaker cabinet (tuck the "tail" of the sock up under it for best looks).
This will help deaden panel resonances a bit, and the added mass will lower the natural rocking frequency of the upside-down pendulum to, hopefully, below the audible frequency range and improve the imaging a bit.
I have no useful experience with resistive loading.
Best of luck to you!
Duke