DIY Speaker Risers

[kirkbross]

I just bought a pair of Dynaudio BM5a's... nice. Anyway I want to elevate them about 5" but don't want to drop a bunch of dough on Auralex or some other expensive speaker riser product.

Any tips for making some risers, perhaps with some kind of dense foam rubber to isolate a little?

[knightfly]

Are you putting them on stands, or on a desk, or??!? Steve

[kirkbross]

I actually ended up getting four 2" slabs of cinder block tops from Home Depot (two per speaker) so I have 4" concrete risers now (8"W x 16"D).

I glued them together with construction adhesive and covered them with clear rubber / plastic like you would line cupboards with. I bought the roll of lining at Home Depot too.

[knightfly]

Good choice... Steve

[Ro]

Seems like a nice thing to photocapture and post it here

[kirkbross]

It's actually kind of ugly... I just bought four 2"H x 8"W x 16"D gray cinder block slabs from Home Depot. I think they're called cinder block "tops" or something like that and they're about $2 each. I glued them together in pairs with construction adhesive so each side had two slabs and was 4" tall. I also bought a roll of thick rubber / plastic and wrapped each riser width-wise like a burrito to protect my speaker bottoms from the coarse concrete -- the fronts and backs of each riser are exposed -- but it actually didn't work so well because I didn't use any adhesive, I just duct taped the seam. I would recommend just cutting a rubber placemat to 8" x 16" and putting it on top.

[lmno921]

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[Ro]

This, obvious, SPAMMER account should be disabled by a MOD.

[Sandersd]

It's actually kind of ugly... I just bought four 2"H x 8"W x 16"D gray cinder block slabs from Home Depot. I think they're called cinder block "tops" or something like that and they're about $2 each. I glued them together in pairs with construction adhesive so each side had two slabs and was 4" tall. I also bought a roll of thick rubber / plastic and wrapped each riser width-wise like a burrito to protect my speaker bottoms from the coarse concrete -- the fronts and backs of each riser are exposed -- but it actually didn't work so well because I didn't use any adhesive, I just duct taped the seam. I would recommend just cutting a rubber placemat to 8" x 16" and putting it on top.

Instead of bonding with construction adhesive, use green goo to decouple the two slabs and prevent vibration transfer. There are commercial products available using this same arrangement.

[Soundman2020]

I don't think Green Glue would accomplish that. It's not meant to decouple things. It is a viscoelastic polymer designed to damp resonance in drywall, not to decouple it.

- Stuart -

[xSpace]

It is designed to shear under deformation(vibration) and in this process lose the energy created by vibration. Isn't that what a constrained layer damping assembly does?

Semantics

[Soundman2020]

It is designed to shear under deformation(vibration) and in this process lose the energy created by vibration. Isn't that what a constrained layer damping assembly does?

Well, yeah, that kind of is what I said, isn't it? Green Glue is designed to damp resonance between sheets of drywall. But it is not designed to DECOUPLE them, which is what you want for a speaker stand. It damps drywall layers very well, because it is designed to be a constrained layer damping material for drywall.

You gave the long, technical explanation, which is correct of course, while I gave the abbreviated layman's, version. (We seem to have our roles reversed there!!! )

But constrained layer damping is not what you need in a speaker stand. You need decoupling.

The thickness of Green Glue between two layers of drywall is, according to their web site, practically nothing. It comes out of the tube quite "runny", and ends up as a very thin layer between the drywall sheets. Between two layers of porous concrete, I reckon it would be even thinner! I don't see how it would be able to decouple them.

The way I see it, what you need for a speaker is to decouple it completely from the stand, not just to damp the resonance with a very thin layer underneath it. Most designs I've seen for speaker decoupling use neoprene, rubber, or foam for that purpose, or even some kind of suspension system. It's the same basic concept as walls and ceilings: Mass-Spring-Mass. You need something to act as a spring between the mass of the speaker assembly above, and the mass of the stand assembly below. Neoprene, rubber, and foam all make good springs in that application, if you load them correctly. Green Glue isn't thick enough, and isn't designed to be a spring. As you correctly pointed out, it is design to be a constrained layer damping material.

If you think it would make a good decoupling spring for speakers, then what degree of compression do you think would be appropriate? Should it be compressed 10%? 20%? More? Less? What loading would you need to get that compression? The manufacturer of Green Glue does not publish that data AFAIK, so I don't know where you'd get it. (My guess is that they don't publish it because their product is not designed to be a speaker decoupling spring!)

As with all MSM decoupling systems, getting the spring loaded just right is the key. Load it too much or not enough, and it will flank. If it flanks, your speaker is coupled to your stand. Without that compression and loading data, I don't see how you can build such a stand, even if you assume that Green Glue does in fact have useful properties as a speaker decoupling spring.

IMHO, using Green Glue for something that it wasn't designed to do, about which the manufacturer makes no claims at all (and provides no data), doesn't seem like a good idea: After all, if it really DID work for decoupling speakers, then I reckon they would have figured that out by now, and would be talking about that in their marketing, and providing the same amount of data as they do for the normal application of damping drywall resonance, as another way to sell more of the stuff! But they are a careful company, from what I can see, and they back up their claims with solid data from testing their products in independent labs. So the fact that they make no such claims suggests about their product doing well as a speaker stand decoupling spring, and the fact that they don't provide the data that you'd need in order to use it for one, suggests that it probably doesn't do what it wasn't designed to do.


- Stuart -

[Ro]

hah! wait untill you see MY DIY speaker stands soon
(note that I didn't wrote a DATE yet, soon can be a year, two or more. gheh)

no, I don't have anything interesting to say indeed...