I stumbled on this thread by chance recently and it has really grabbed my attention.
I was going to buy one of these but I realized I already have some of the Auralex PlatFoam left over from about a year ago. I had purchased a sheet of this stuff to isolate my XBOX 360 which sits on a glass shelf. I only needed a section large enough to match the dimensions of the XBOX so I had the majority of the sheet left over. The only difference is mine is 1" thick instead of the 2" thickness they use on the SubDude/GRAMMA isolation platforms. I also still had some Studiofoam left over from when I applied it to my walls. So, I decided it would be pretty economical to build one of these things considering the material I had on hand. The only thing I was missing was the MDF, which I assumed I could grab pretty cheap at Lowe's. Unfortunately, the smallest size they had a Lowe's was 8' x 4' and that wasn't happening - I didn't have the wife's minivan or the desire to buy a sheet that large so I could cut out a 21" x 24.5" section (the dimensions of my sub). I did find a 3/4" sheet of birch lament that came very close (24" x 24") to the dimensions of my sub so I grabbed it and headed home.
I cut four 4" x 24" strips of the PlatFoam out of the sheet. I used some of the spray adhesive I had left over to permanently join two strips of the PlatFoam together and get the same 2" thickness used on the SubDude/GRAMMA. I also used two 12" x 12" Studiofoam panels in the middle section of the platform (like on the SubDude/GRAMMA). I did not cut the wood to exact dimensions, cover the wood, or permanently attach the foam to the bottom since this was intended to be a quick experiment. My plan was test it out and either finish it or take the wood back to Lowe's depending on the outcome.
I took measurements with REW before and after placing the sub on the isolation platform so I could have data to prove or disprove any changes I perceived in my listening tests. I also listened to a combination of music and scenes from movies that I was already familiar with. They are scenes I use to demo my system for people.
I made a couple interesting observations during this exercise. First, I did notice a significant reduction in vibrations and resonance in the floor and a mild reduction in the walls. The second thing I noticed was a bigger than expected gain in output volume from the sub when it was on the platform. I’m not sure why this occurs but my best guess is the hard wood plank is substantially more reflective than the carpet and thick pad the sub is normally sitting on. A second contributing factor could be the space between the woofer and the floor/platform due to the sub sinking into the carpet/pad.
I did NOT notice any change in the characteristics of the subwoofer after placing it on the platform. It did not sound any tighter or more musical to my ears. The removal of the vibrations/resonance in my floors were very noticeable and welcome but I could discern no difference in the tonal qualities of the sub.
Here are the graphs from before and after placing the sub on the platform. I was a little surprised to see the larger dip at ~30Hz after placing the sub on the platform. All in all, not a whole lot of difference.
While I didn’t notice any change in the sound quality of the actual subwoofer, the reduction/elimination of the resonance from the floor vibrations was very noticeable and could be perceived as a less “muddy” sound in the room when playing intense LFE passages. The floorboards were essentially adding sound to the environment and it is a noticeable improvement after it has been removed. It is worth noting I do not feel any reduction in the tactical impact of the sub. This sub hits really hard and extends pretty low. Nothing has changed in that regard. The fact this platform has removed the audible vibrations without any tactical reduction is kind of surprising the more I think about it.
I will trim the board down to match the width of the sub and do something to make it look nice. I haven’t decided what I want to do for ascetics yet. I’m thinking about wrapping the whole contraption, including the foam, with a lightweight black fabric. Or I might paint/stain the wood and use some material as a valance to cover the foam. Or I could….Oh, I don’t know yet so I will leave it alone until I come up with something…
Additional Note: I bypassed the BFD filters and ran another series of measurements and then applied new filters to compensate for the extra dip at 30Hz prior to my listening tests.
Here is some information on the equipment, environment, and material I used during the evaluation.
- 11’ x 15’6” room on the first floor
- Standard wood floors covered with carpet and a thick carpet pad (note: the floors are pretty “springy” in this room.)
- Drywall walls/ceiling
- Absorption on the wall behind the speakers and on the side walls at first reflection points
- Bass traps in front corners – floor to ceiling
- AVR – Onkyo TX-SR705
- Speakers – Paradigm Monitor 7 v4 mains, CC-370 center, ADP-370 surrounds and back surrounds
- Sub – Elemental Designs A5 – 350 (Crossover @ 50Hz
- Blueray player – PS3
- HD-DVD – Toshiba HD-A35
- DVD player – I used my XBOX 360 (Media Center Extender mode) for playback of all clips marked listed as DVD. I have all of these clips ripped and saved on the hard drive on a computer running Windows Vista Media Center. I stream them with the My Movies Media Center Plug-in.
- SACD/DVD-A player – Marantz DV6001
- Sub PEQ - Behringer Feedback Destroyer Pro [FBQ249]
- Measurement software - Room EQ Wizard (REW) Version 4.00 build 673
Demo Material: I listened to each of these before and after placing the sub on the platform.
- Babylon Sisters - Steely Dan/Gaucho (SACD)
- Hey Nineteen - Steely Dan/Gaucho (SACD)
- Gaucho - Steely Dan/Gaucho (SACD)
- Summer Fling - Spyro Gyro/The Deep End (SACD)
- Monsoon - Spyro Gyro/The Deep End (SACD)
- As You Wish - Spyro Gyro/The Deep End (SACD)
- Hotel California - Eagles/Hotel California (DVD-A)
- New Kid in Town - Eagles/Hotel California (DVD-A)
- Life in the Fast Lane - Eagles/Hotel California (DVD-A)
- Victim of Love - Eagles/Hotel California (DVD-A)
- Snowbound - Donald Fagen/Kamakiriad (DVD-A)
- Comin' Home Baby - David Sanborn/Timeagain (DVD-A)
- Man from Mars - David Sanborn/Timeagain (DVD-A)
- Rest in Peace - Extreme/III Sides to Every Story (CD)
- Color Me Blind - Extreme/III Sides to Every Story (CD)
- Flight of the Pheonix - The crash landing (Blueray | DTS HD-MA)
- Incredibles - The scene where the missles are chasing and then hits the plane carying the mom and the kids (DVD | DD EX)
- Master in Command - The first naval battle (DVD | DD)
- Matrix Revolutions - When Neo meets with the machine "face" to discuss peace (DVD | DD)
- Finding Nemo - Daria glass tapping (DVD | DD EX)
- Star Wars: Episode I - Amadella's shiny silver ship landing / decoy bombed (DVD | DD)
- Star Wars: Episode I - Pod race (DVD | DD)
- U-571 - Depth charges (HD-DVD| DTS)
- Cloverfield - From the point they're on the roof right before the SOL head comes crashing in until the thing is past. (Blueray | TrueHD)
- Cloverfield - When the military first attacks the thing. (Blueray | TrueHD)
- THX - Cavalcade (DVD | DD EX)
- THX - T2 (DVD | DD)
- THX - TEX (DVD | DD)
- THX - TEX 2 [Moo Can] (DVD | DD)
- THX - Amazing Life (DVD | DD)
- Dolby Digital - City (DVD | DVD)
- Dolby Digital - City Redux (DVD | DVD)
- Dolby Digital - Rain (DVD | DVD)
- Windows Media 9 - Factory (DD)
- Windows Media 9 Series - Pinball (DD)
FWIW, here are is the frequency response, LF Decay, and waterfall for the sub blended with the mains and BFD filters applied.