[Badd99]

Hello!

I am finishing my music room build / nx-otica & pair of triple servo subs. I was able to just get some custom fit 1" thick granite slabs (19"*21") that will fit perfectly under the nx otica and subs with 1" on all sides. Best thing is I got these cut, finshed, and edged for free. Nice granite too!

I have never played with slabs under the speskers and since it was free I got them done. My dedicated music room is carpeted with thick 8lb memory foam pad which is on a concrete floor. Not sure if it would be best to:

1- granite on carpet and speaker / sub on slab
2- some isolation feet/spikes under slab and spesker/sub right on slab
3-granite slab on the carpet and speskers spikes or isolation feet on the speskers/subs sitting on the slab?

Thanks for anyone's experience / tips / thoughts!

[toocool4]

Since you have all the kit, experiment and go with what sounds best to your ears.

[Elizabeth]

For years I used 2" thick concrete 30" round patio slabs up on Tip toe spikes under my Infinity RSII speakers. I used the slabs for over 15 years.
Now my Magnepan 20.7 are up on Bloodwood 1.5" square by various lengths.
Whatever you use it is (usually) good to get the base of the ground.

[E-Zee]

My experiences have been similar as that posted above.  Put your slab on feet.  It's a lot easier for the weight of the slab to fully compress 1sq cm of carpet under spikes than it is to flatten 1 Sq foot, by laying it flat. (929 times easier, using those hypothetical measurements. As slab gets bigger, the comparative stability improvement from using spikes actually increases)

The easy test is to lay out your slab and put an adequate portion of your weight stepping on an outside 1/3 of the slab. If it rocks than it's not stable.  I'd have a hard time imagining the circumstance where the slab on spikes is not more stable than slab laying flat on carpet.

[FullRangeMan]

In my experience:
= enclosures direct on the floor will increase the bass.

= Spikes will benefit midrange/treble.

= In the 1990s Hifi Choice UK concluded that granite/stones as speaker platform increases the sub bass under 60Hz, which they did not recommended.

[JCarney]

Hi Badd99,
I use granite under my Dali grands, with three eighths inch stainless steel ball bearings blu-tacked into the spike holes so I could place them. I have a basement in my home. If you have a suspended floor, like with a basement like mine, the granite helps to reduce the bass effects in the floor, which tightens up the bass making it less muddy or boomy. A concrete slab floor will not have the same problems as a suspended floor, so the granite will not provide the same level of benefit as the suspended floor. If you use the granite on a concrete floor, be sure to get them off the concrete with something in the corners and center.

Hope this helps,
JCarney

[mojo_65]

I share my experience... I have a nice room with wooden parquet on a suspended floor, elastic I would define it, therefore I need to decouple to isolate as much as possible the speakers' enclosure to ha a better performance.
When I was using the big 2 ways Electro Voice with 15" woofers I used a slab of serena stone with the same size of the enclosure, on felt so to avoid damages to the wood but then I used isolation feets between the slab and the enclosure. Maybe I'll post a picture later.

The stone slab simulates a concrete non elastic floor and the additional feets decouple the speakers from the "floor". The improvement was consistent and the whole frequency range benefitted from such a solution. Highly recommended for wooden floors in old houses (or renovated farms, like in my case  ). IMHO obviously 
Alessandro

[Badd99]

Thanks everyone... Seems best to spoke the granite and the speakers to the granite but I'm afraid it might raise the speaker too much. Regarding the subs, seems that's definitely the best way to go.

This will all be on a concrete basement floor, but I don't think further removing vibrations to the room is going to be a bad thing.

[Cheytak.408]

I live in a home with pier and joist floors.  The floor joists are 2x8 @ 16"OC with piers every 8'.  The floor build-up is 2x6 T&G fir decking, 3/4" particle board and then 3/4" red oak flooring.  It was still too flexible, so some (many) years ago I went into the crawl space and insulated the floor to eliminate cavity resonances.  I then glued and screwed 3/4" plywood under the front third of my room (20' x 14'4" x 8').  This stiffened the floor immensely.

My speakers sit on vibram pads with marble slabs with 3/8" hard felt 4" x 4" squares under the corners of the speaker cabinets.

Low frequencies are deep, full and tight with a great handoff to the lower mids.

The elaborate steps I took to get the floor in shape were well worth it.  Before, LF were a a bit bloated with sketchy pitch and transient definition.  Now, Christian McBride is in the room, front and center.  Color my happy

If I were to do this today, I would hire a contractor to spray foam between the joists and another to add the ply under deck.  I'm way older and much wiser.

[richidoo]

That's a great idea! Thanks for sharing that Cheytak

[toocool4]

I have used granite, concrete and wood, they all sound different and work to a certain degree.
I have now settled on using Symposium Svelte Shelf + Symposium Roller Roller blocks under my speakers. Counter intuitive even though it allows movement, I get sharper defined notes and bass is deeper.

What you see in the image below is IsoAcoustics carpet shoes / Symposium Roller Roller blocks / Symposium Svelte Shelf and the speakers sitting on top of that stack.

[Cheytak.408]

That's a great idea! Thanks for sharing that Cheytak

Thanks.  I've learned a lot of things the hard way, but I've learned more through the experiences and advice from others.  That is one of the great things about being in a community of like minded lunatics.