Effects of concrete as base for subs, speakers and potentially equipment

Sometimes more weight on the top is the right answer.  Reduces back and forth rocking caused as a response to the woofer motion.  5-10 lbs on satellites can really tighten things up.

Thanks @erik_squires i have loaded weight on top, but the hollow under the floor is pretty significant. I have it on a wooden platform now and that helped a lot. 
 

This is as much as playing with form as it is function. I won’t keep anything that makes it worse- I would however like to avoid any pitfalls. I don’t want to get anything made up for me that is immediately wasted. If it works I am considering some much larger blocks for the electronics. 

I use these concrete step stones for a base under my speaker stands. I painted them black to match the color of the stands. The results are outstanding!!

Bare concrete is porous and can result in “flabby” bass response. Expoxy coated concrete works much better. I’ve used both with 3 way floor standers. Good shelves/footers also help tighten up the bass. Jeff

Thanks @yogiboy ​​@yoby 

If your friend is good with shapes, insets, etc. you have a few interesting options:

• Concrete Mixture - Check with your friend whether he thinks that adding polystyrene balls (sometimes added for a lower unit weight) would help with damping and maybe reduce any ringing.  You can also consider adding a color conditioning admixture to achieve a certain look.
• Mass Loading - You have the option of adding threaded embeds (or through-holes) so you could rigidly attach your speakers directly to the concrete bases, which would be a form of mass-loading similar to the effect of using Sound Anchor bases.
• Stability - If the speakers were attached to the bases, not only would the added weight and lower center of gravity improve stability but you could further improve stability by extending the bases out beyond the speaker's footprint.
• System Damping - With the speakers attached to the bases as described above you could then use decoupling type footers beneath the concrete base for optimum performance on a suspended wooden floor.  Individual springs or Townshend pods would be an interesting choice and if your friend could make insets in the bottom you could have the effect with only a small portion of the spring being visible.  Another option that I like is to use platinum silicone elastic footers, which basically operate as (elastomer) springs but are much easier to set up.  I have these under my 150 pound subs and these under my 180 pound monitors and stands.  They come in a range of sizes and support capacities so you can use them for virtually any size speaker or component.
• Base Only - The easiest (and least interesting) option would be to simply set the bases on your floor and set the speakers on the bases using the speaker footers of your choice.  You may want to use one of Herbie's options (like Giant Fat Dots) between the bases and the floor or interestingly you could use a sheet of something like Owens Corning Acoustic Board between the concrete mass and the floor.  It comes in one or two-inch thicknesses.  BTW, I believe the well-regarded AV RoomService EVP damping supports may be made from Owens Corning 703 (for the medium) and 705 (for the hard), either of which could also be considered beneath your concrete bases (you could cut the boards the same size as the bases and paint the edges of the yellow fiberglass material as desired), or you could simply buy some EVPs.
• Equipment rack or slabs.  No reason not to use concrete bases under equipment or use concrete somehow as an equipment rack.  I would probably decouple components from the concrete using one of the methods described above.

Good luck - post some pictures.

After the excellent suggestions of

Concrete or any other material that resonates very little is a good choice.  If you can tap on it and hear little in return, it's probably a good choice.  Concrete is a great option, but as with anything, there are different grades/ mixtures.  Higherfi Audio once has a pair of speakers that used the same sound dampening materials and technology used in nuclear submarines.  I can't remember the brand, but it was a one of a kind that sold for upwards of 1 million dollars!  Serious stuff there!  

@mpoll1 Wrote:

Effects of concrete as base for subs, speakers and potentially equipment

I chose concrete blocks and lead to raise and decouple the speakers from the wood floor. Concrete is a great energy sink and lead adds damping. I am very pleased with the results. Each speaker has four 35 pound solid concrete blocks and 30 pounds of lead. The speaker sits on a 170 pound energy sink. See my systems page left speaker. Wanted to hear how it sounds, before I did both. 😎

Mike

See below JBL Project K2-S9500 speaker introduced in 1989 was design with a concrete energy sink for it's base.

https://www.audioheritage.org/html/profiles/jbl/k2.htm

I added thick beam in my cellar, placed vertically from floor to roof, hammering it into place so it should take the weight off my record player and system. One of the best investments I ever made. I can jump up and down before my record player, no skips.

@OP If you have wooden floorboards, one problem with putting concrete slabs under speakers is that it can be difficult to get the slab to be stable. Personally, I favour making platforms of thick ply and screwing those into the floor. That provides a stable bass and stiffens the floor.

Heavy masses under electronics can be hit and miss. Resonance control requires the mass to be damped. Mass by itself will resonate by at low frequency and will continue to ring if it is not damped.

This is why i use some tuned mass damping  with two sets of springs under and above  differently compressed ...

Heavy masses under electronics can be hit and miss. Resonance control requires the mass to be damped. Mass by itself will resonate by at low frequency and will continue to ring if it is not damped.

Interesting stuff..👍

This is why I love this site. I will go ahead and get something made up. @mitch2 i will be playing around with some of those suggestions. 
 

@ditusa what is the order of lead and concrete? What is on the floor and what are the speakers on top of?

thanks everyone!

@mpoll1 Wrote:

@ditusa what is the order of lead and concrete? What is on the floor and what are the speakers on top of?

The first block, on which I glued cork and felt to the bottom, sits on the oak hard wood floor. On top of that block sits 15 pounds of lead, then the second block sits on top of the lead. I then put Equipment Vibration Protectors in between the speaker and the top block to decouple the speaker from the blocks and floor. I used construction roll lead flashing 8’’ wide and weighs 60 pounds. The speakers rest on top of the Equipment Vibration Protectors with no fastener and are very stable (the speakers weigh 250 pounds). The blocks and lead were purchased at Lowe’s, see below: The Equipment Vibration Protectors were purchased from AV RoomService, LTD. See below:

Mike

Thanks Mike. @ditusa 

The best idea is to stabilize the wooden floor from below, if you are able to do that, e g with a beam in the basement like I described above. If not possible, you can try weight springs etc, but it will all be placed on an unstable floor.

I limited my earlier response to your question about using custom concrete slabs and did not address the floor. The wider the slabs, the greater the improvement by spreading the load over a larger area, but @o_holter is correct that gains can be made by reinforcing a suspended wood floor from below.

The easiest way to improve that situation would be to stiffen the floor by attaching a simple, adjustable jack-post column beneath the floor joist nearest to the two speaker locations and possibly also near your equipment rack, as @o_holter did near his turntable. However, not everybody has the ability to feasibly add support columns in their lower level, depending on the usage of the room below where your system is located. Some folks have reported an improvement by adding cross bracing between the floor joists in the vicinity of the speaker positions, with or without the support columns. If you do add cross bracing, be careful not to affect the integrity of the floor joists by cutting or drilling into them (consult a builder if you need advice).

In general, structural members are stiffer near the ends where they are supported so the closer your speakers and electronics are positioned to a bearing wall, the less of an issue you should have.

I am going to base this on our vibration control at my workplace.  We measured vibration in all frequencies.

You buy a speaker and put it on the floor.  Doesn't matter if it's wood or concrete although wood can flex more.  As the speaker plays it essentially bounces around throwing its sound waves out of phase.  

I think concrete is fine because of the mass ratio vs the speaker, but spikes into the concrete still allow the speaker to vibrate and move.  Another piece of concrete on top of the floor then bounces.

A floor that isn't level also causes phasing issues.

Try a set of $30 springs first. Audiocrast and Nobsound make them, 4 per speaker.  Herbies makes some special silicone also. Either of these examples dampen the items and greatly reduces movement.  Springs are self leveling.  My floor was not level. You can go on up the price scale real soon.  If you try these low cost solutions first and decide if you want to buy something more pricy, or stick with them.

I went to the countertop place and got scrap granite and marble to use under my speakers.  I thought it helped.