The Inert, Immobile Speaker Platform Project

[KuruPrionz]

This started here a week or two ago when Craig mentioned the Primeacoustic Recoil Stabilizers and how much better his speakers sound on top of them. Here is a link to a Tape Op review.

https://tapeop.com/reviews/gear/62/rx7-recoil-stabilizer-speaker-platform/

 

The concept makes sense, it should work well. I started to buy a pair but the current supply chain delays slowed me down and I thought about making something similar (but probably not quite as pretty).

 

There are two things that need to be done to improve the sound of a monitor speaker sitting on a shelf - like mine. First you want to reduce the transmission of resonance from the speaker cabinet to the surface that supports it and secondly you want to prevent the speaker itself from moving, causing phase shifts and cancellations that detract from the sound. Both are important and related, there is no conflict between these benefits.

 

I found one aspect of the Recoil Stabilizers interesting and a bit troubling. If you want to isolate resonance you don't want the entire bottom of the speaker to make contact with the platform and you don't want the entire bottom of the platform to make contact with the shelf. That is theory and I'm certain the Primeacoustic stuff works great but I went a little different direction.

 

I'm hoping to make a better platform at a lower cost partially by using my own labor but primarily by designing something that is less resonant but still very stable. Inspiration struck one day when I was grocery shopping. I saw cutting boards made of some sort of composite material (the dust from sanding sticks to a magnet but the heat from cutting with a saw causes melted plastic curls). The bottoms of my Mackie HR824 speakers are 10" wide by 10 1/2" deep, the cutting boards were 9 12" wide by 15" long and $4.99 each so I bought 4 of them. Acoustically, they are pretty much dead, they don't ring when struck at all.

 

I found a closed foam yoga mat at the thrift store for $3, 3/8" thick like the cutting boards and dense foam.

 

I cut the boards down to 11" long and used a spray adhesive to glue a "sandwich" of cutting board / foam / cutting board for a platform. Research led me to favor Sorbothane rubber for the feet and for the speaker to rest on as it converts motion to heat and is very sticky - both desirable traits. The total hight of the platforms is 2 3/8" tall and each weighs 3 lbs 6 oz. They feel solid and sonically unresponsive. And the contact surfaces are very sticky, I don't think these will move willingly.

 

Photos attached of the present state, just the bottom side. The feet are hemispheres 2 1/2" in diameter and self adhesive. The tops have strips of 1/8" thick Sorbothane around the edges of the platform. I don't want to put the feet down on anything until I place these in their new resting places and I've left the protective covering on the top strips. I'll take more photos as I get around to putting these under the speakers. The shelf and the bottom of the speakers will need to be cleaned with alcohol first.

 

The top strips are thicker and wider on the front and back and the side strips leave openings for air to escape - eliminating resonance caused by air pressure. The speaker is more or less supported by the edges, which are much stiffer than the center of a panel. Total contact between the speaker and the platform is reduced considerably and total contact between the platform and the shelf is reduced to the bottoms of the 4 large sticky feet.

 

To test, first step will be to bring up a drum loop in MODO Drum and turn it up a bit with the system in place as it is now. The Tape Op review above mentions touching the speakers to feel the vibration/movement and I had thought of that myself so I will do that as well as listen. Next, I plan on clearing off the shelf, cleaning it with alcohol, placing the platforms and peeling off the protective sheeting. Put the speakers back in place and play the same loop at the same volume. I will listen and touch and see what happens. I am hoping for good things.

 

This might take until the weekend. Meanwhile, take a look at the photos and feel free to chime in with opinions, questions or insults (cuz they kinda ugly!)

[Anderton]

Wow, a cliffhanger! I'll say one thing, your project has balls.

[KuruPrionz]

I tested today. I used a couple of beats from MODO Drums to compare.

Honestly, the front baffles on the Mackies barely vibrate at all when a solid kick drum punches at a volume level I would prefer not to exceed.

 

It has been many years since I somehow made the desk resonate, I don't remember how I did it but it was definitely energy transferred from the speakers.

They were probably insanely loud, I had a small MOTU interface that could not be turned down enough, it did not get to live here for very long.

 

I felt no resonant vibrations on the underside of the shelf the speakers are on with either the foam or the stands. I also felt no vibrations under the platforms on the new widgets, there is really no way to check under the foam I had before and I didn't turn the speakers on their sides to see if the bottoms resonate.

 

I thought the kick sounded tighter on the platforms and it could be true but it could also be wishful thinking. Either way I am going to leave everything the way I have it now.

If I had a set of the Recoil Stabilizers I could swap those in and see if them made any difference.

 

I might hear more difference with another pair of monitors but who knows? I'll give Mackie this, those are solid little boxes.

And, I do not have a conclusion to offer MPN except that these platforms will cause no harm that I can hear.

[KuruPrionz]

As of 11:45 this evening, the speakers are stuck right where they are. For all that, the sorbothane hemispheres on the bottom can be made to move laterally but it takes considerable force and the bottoms do not slide at all. By the description, Sorbothane converts motion into heat, I don't think the woofers have the mass to transmit enough motion to exceed conversion, at least not at the levels I listen and mix with.

 

It does change how I would build another one of these. I would use 3 of the 1.25" diameter hemispheres in the corners, being smaller they will be stiffer as well.

 

It wouldn't be too hard to do it, it might be more effective with some speakers than others.

 

In Kaizen they say "fail early". It can accelerate learning or at least lead to refinement. There's nothing that can't be done better in some way.

[KuruPrionz]

A follow up.

When I positioned the speakers, one of them was over to one side of the platform about 3/8". It shouldn't bother me but it sort of did.

Tonight, after leaving them on the platforms since early November I set the one that was a bit off center on it's side and tried to remove the platform.

 

To be honest, I was surprised by how difficult it was to get the speaker off the shelf, the 4 hemispheres were really attached to the shelf.

The platform itself? Not going anywhere any time soon. I made a solid attempt to remove it, failed and put the speaker back where it was.

 

These are definitely stable and inert, if you build a pair be sure to put everything together just how you want it!!!!!!