Granite slabs under speakers?

I think that to realize benefits of granite slabs under audio gear the granite slabs themselves need adjustable spikes set through the carpet and leveled on the subfloor. Then the speakers have to be perfectly leveled atop the granite.

In your case Bob, did you simply place granite slabs atop the carpet? I wouldn't expect benefits that way as the speakers are not truly decoupled. When I look at pics of your speakers they don't seem to have especially long spikes. One thing that helped my Totem speakers was to buy aftermarket spikes, sharp and long, that easily punctured both my carpet and padding thereby setting them securely on the subfloor and decoupling them. Longer spikes also make leveling adjustments easier in carpet pile.

Let me say, some speakers don't need spikes and sit flatly. Case in point my Monitor Audio PL200s. I have these on thick 2" granite and on carpet, well clear of back and side walls...

And I defy anyone who points out they're not optimised this way! The granite keeps the bass in tow. Try a Massive Attack try.

Put some granite plates too under my speakers as the wood floor was showing lots of vibrations when playing music. Under the granite I put some rubber plates (the one that are meant to be fitted under washing machines).

I think whether granite slabs work for you is pretty hit and miss. Works for some rooms and some speakers but not for others.

The mechanical coupling of speakers to the room is a complex interaction and many "quick fixes" have been proposed, from Sorbathane (and it's clones like Herbie's Fat Gliders/Dots), to spikes made of esoteric materials (e.g. bronze) to granite chopping boards.  Each of these, like most "quick fixes" don't work in most circumstances, but do work in a few.

However there are a few things that can be said (in each case the term speaker includes any stand system in use).

Sorbathane behaves as a mechanical filter with different properties dependant on frequency and the direction of the vibration.
- For low frequencies it transmits vibration in the direction of the compression [vertical], but behaves compliantly for vibration across the direction of compression [horizontal].  At higher frequencies it primarily absorbs vibration and at even higher frequencies it once more transmits vibration.  This results in a low Q mechanical tuned circuit with variable frequency response. What it does for any particular speakers is anybodies guess!

Putting spikes into a soft wood floor gives some compliance at low frequencies for vibration across the direction of compression [horizontal], and a to a lesser degree in the direction of compression [vertical].

Putting spikes onto a hard floor gives very good mechanical coupling in the direction of the spikes and good mechanical coupling across the direction of the spikes.
- This is the most predictable interface.

Standing a speaker on a compliant carpet, not surprisingly introduces compliance into the interface.
- This results in a low Q mechanical tuned circuit, again what it does for any particular speakers is anybodies guess and will depend on the properties of the carpet!)

Standing the speakers on a granite slab which in turn stands on carpet lowers the frequency of the tuned circuit as compared to standing the speaker directly on the carpet.
- The heavier the granite slab, the greater the lowering of the tuning frequency.  If the mass slab is similar to the speaker or greater than the speaker, it also reduces the amplitude of the vibration transmitted.

When I used speakers on carpet. I found Titanium black marble slabs effective. Polished on top and left unfinished underneath.  If struck they left quite a high pitched resonant ding.    When the speakers were used without them under they didn't sound as well defined in the Bass and images less inclined to leave the box.  Although this could have been a result of using Nordost Pulsar points instead of spikes on the speaker as well.

When I got a pair of Focal floorstanders ( 4 foot tall ) Profil 77 in my vintage system useing Bryston amps .Sitting on a carpeted concrete floor I found there was movement in the cabinets.I wasn't to bothered as they are so easy on the ear and an easy efficient load to drive.It was talking to a fellow HiFi enthusiast and he gave me some 15 mm triangular blocks made out of a plastic resin material.

Fitting 4 under each speaker totally eliminated any cabinet rocking and was a brilliant tweak as the bass really tightened up and imaging was better.

My friend has gone the other way with his Focals in his SET valve system he has his speakers on Townsend air filled stands.The speaker rocks when touched but it decouples the speaker from the floor.Just a different approach to support - sounds great to my ears.

On the subject of Townsend "Seismic Isolation" platforms: the fella I bought my DBLs from used Mana speaker platforms. They seemed a simple enough construction so I measured & photographed them. A couple of months ago I got round to welding a pair up out of angle-iron. Following advice from someone who's very knowledgeable about such things, I made the top platform out of  a bonded sandwich of 12mm marine ply with a 3mm aluminium sheet filling. So there are spikes on captive nuts into the floor, spikes supporting the platform, & the speaker spikes. The speakers are now quite mobile, you can rock them back & forth. Now this seems to fly in the face of what one would consider best for speaker mounting, but surprisingly the result has been excellent, the sound being very focussed and precise. Bass is deeper and better controlled.

I've tried various things under my speakers over the years. Granite slabs muddled the sound, as did placing the speakers directly on the floor (oak planks resting on compressed flint & mud). Fraim chips seemed the best option I tried, and following advice (and help in moving the DBLs) from Darke Bear these worked even better upside-down.

There's an interesting video on the Townsend website regarding the decoupling of speakers from the floor and, even allowing for the commercial sales pitch, makes some valid points. 

It’s a bit like the SL2s, which sit on a leaf spring and can rock back and forth. It’s all part of the design of course, and is tuned to make the speakers oscillate in the right way. 

To make a decoupled design work well you either have to

1   Design it like that (the SL2 approach)
or
2   be very lucky and get all of: The tuned frequency, the storage modulus and the loss modulus just right (the after market approach).

Yes I've tried it, but I've never managed to get it to work quite right with speakers that weren't designed to work that way in the first place.

I've always adopted the empirical approach. Try stuff, spend lots of listening time to ensure it's genuinely better, rather than just different.

I might take joerand's advice and invest in some longer spikes, the Dynaudio's spikes have now gone right through the carpet, underlay and have anchored into the floorboards below but because of the relatively short spikes the bottom of the speaker is now resting directly on the carpet. They still sound better than when the granite was underneath though.

Bob the Builder posted:

I have a carpeted suspended wooden floor .....

Any chance of stiffening it?

I use an old pair of HNE granite stands - work really well for me

I have used mini surface plates,or layout tables under my Dynaudio's,on top of carpeted floor with great results.They measure 18x24 inches x 3 inches thick,and weigh 150 pounds each,yet only cost me 100 dollars each,Canadian funds.Another time I screwed flat head wood screws through the carpet into the wood floor below.Then the spikes from my speaker stands sat in the head of the screws,which was flush with the carpet,this also works very well.

tonym posted:

I've always adopted the empirical approach. Try stuff, spend lots of listening time to ensure it's genuinely better, rather than just different.

Wise words Tony,

Interesting your comments with regard to the Townsend seismic air isolation stands and your DBL 's.

I must admit when I first saw them under my mates Utopias and he explained the thinking about the Townsend approach to isolation it seemed to go against all the light and rigid thinking of the past.But like you I was really impressed with what the Townsend's did to his Focals.Definatly better bass definition.His Utopias are'nt as heavy as your DBL's but still 65 kg  each.

Always interesting difearant manufacturers approach to design in our hobby

When I had my SL2 I used them on Mana stands (floating wood floor). Made them quicker but sharper, which I liked. Sold the SL2 ten years ago but still have the Mana stands somewhere...

With Titans I have used several combinations, Silent Mounts, Sonority Stands, direct on the floor, all above in combination....still haven't made up my mind, it all sounds fantastic but in different ways...

//Jonas

Got the kitchen countertops done recently - went from stone to quartz. That improved the acoustics of the room. Also, used remnants from this project for use under the speakers. I'm hearing bass I've never heard before.

I have been using made to measure granite slabs under my S400's for quite a while now.  I find them convenient for positioning them on my thick carpet (over floating wood floor) and giving them a solid, level platform.  The carpet is too thick for the spikes and when I tried to sink cross head screws screws in place I couldn't locate the heavy S400's easily so gave up.  Everything sounds great with a tight defined bass. 

MangoMonkey posted:

Got the kitchen countertops done recently - went from stone to quartz. That improved the acoustics of the room. Also, used remnants from this project for use under the speakers. I'm hearing bass I've never heard before.

Damn!  Just put in stone.  Always a step behind!

Nick

Oiled oak for a warmer sound

I'm listening to Folk Singer - Muddy Waters (Analogue Productions remaster) and I can hear the sound of his fingers running across the frets so life like. I don't know if it's the speaker's without the granite slabs or not but can't remember it being so clear before.

begs the question why manufacturers don't do more in this field

audio1946 posted:

begs the question why manufacturers don't do more in this field

Because it depends on the mechanical characteristics of the floor on which the speakers stand; and of that the speaker manufacturer has no control.

There have been some attempts at partially decoupled speakers, for instance the SL2.
Some (like that) have worked (but with high development costs); others have been less successful, but still very costly to develop.

Even in the case of the SL2 some parameters for the operating environment needed to be specified for them to work well; viz, the necessity for them to be place very close to a solid wall.  This is needed not only for bass reinforcement but also to present a high mass against which the compliant coupling can operate.

After trading up to a 300 with it's better separation etc I decided to put the granite back under the speakers and lasted one side of an lp it totally killed the sound.  

These humble Dynaudio's just keep growing and growing with the 300.  I managed to connect my sub back up by running some old speaker wire from the back of one speaker (thanks HH) .  If I set the crossover point right down at 50 the lowest possible on my sub and the volume of the sub to almost nothing it just fills out the bottom end of the X32's nicely.