Cheap Speaker "Isolation" Solution for 300 lb. Speaker

I am wondering if the, "O.P." ever had any luck. I have had the same problem with heavy speakers. Sorbothane "will" actually work. But you may want to contact the manufacturer directly for a baseline of recommended shapes, type/rating and etc.. "I have, several times". They were not difficult to work with. But their answers left me at times with just many more questions, especially upon further reflection.

I have used the (50/70) Durometer rated pads, (6" x 6") X 3pcs. at 1" thick. "Which brings the Natural Frequency down to about 10Hz. according to the manufacturer". 

"Or so I was told"

I was also told that these particular pads were orig. designed for autobody to chassis isolation. Which made sense. They came with documentation and were rated at (1500-2500Lbs.) per pad. "When calculating for this type of application the objects weight plus the, (Inertial force of mass, AT load), and also force vectoring must be taken into consideration". Not just a speaker's given "dead weight". Otherwise, the Sorbothane will tend to simply disintegrate during it's very brief and tortured lifespan.

Anyway, I achieved what I'll call, "Mixed Results" at best. I ended up placing all of the pads behind bass transducers in sealed cabinets which did work well at reducing resonance and interior reflections.

Trampoline is optimum. I've built two. One for my turntable and second for SVS SB-2000 pro. They are amazing. Requires some trial and error. The tramp must end up causing item to "hover" inside rack. I've used high strength bungees but it must be free enough to sort of "bounce" within frame. So for these 300 lb speakers the frame would need to exceed the footprint of speaker, and the frame must be both big enough and strong enough to weave sufficient bungees through holes in wall of frame. I used a box with books to replicate both size and weight of sub BEFORE my delivery arrived. At 300 lbs you would need four people to place the speaker onto the trampoline. It will probably tilt in one direction which will require some rearrangement of bungees. A cross weave both front to back and side to side can be accomplished with a solid length of bungee woven back and forth under and over each strand. Slider feet under frame allows the item to be slid with effort but at least you won't have to remove speaker to toe in or whatever. Your fellow tenants will bless you AND (more importantly) those speakers will sound amazingly better. Plus all the vibration shaking your other gear will be greatly diminished.

 UM...Hee hee,

I never stated the weight of the "speaker/s" I was at that time working with.

"Oop's" Sorry!

But they happened to be, (460lb.) each with a, (21" x 24-1/2") footprint and (94") tall (Line-Source) array's.

I am not sure that "Optimum" is the word which I would use to describe your "'Trampoline" config. with those numbers.

Unless maybe I had a really, REALLY intense fetish for "Bungee"!

But alas, I do not...

If you're serious, search eBay for springs. Ones you want will be about 2-3" diameter and compress to about 2" high under a 115lb load. This will be the dirt cheap solution, yet about a million times better than what you're doing now. If you don't want the speakers raised that much then make a platform and put the springs in the corners, in other words copy Townshend Podiums. This is what I did as proof of concept. Works real good.

Or just buy 4 sets of Nobsound. Four sets will easily support 460lb speakers. Way easier. Of course if you do Podiums that will be the best by far. But even Nobsound will be better than what you're doing now.