Firstly, it's worth noting that the tennis ball platform is the most cost-effective way to go if you want to near-elliminate the transmission of kick pad, drum rack/stand 'impact noise' through the floors... particularly if you have your kit set up above another room or flat/apartment. I've looked at and tried a few other options (kid's playmats, gymnasium mats, bubble wrap, packing foam and rubber of varying shapes and densities)... but none have been this simple and effective. All in, I did mine (details below) for less than £40. I'm sure this has been said a thousand times... but whoever thought of using tennis balls for this was genius!
Secondly, for some of you... a tennis ball platform may not solve all your neighbour noise disputes. It will only near-elliminate noise through floors (impact noise)... not through walls (acoustic noise). And while the former is definitely number one for complaints, the latter (which some neighbours will still complain about) can only be solved by sensible kit placement (away from walls) and sound-isolating the room the kit is in (potentially quite expensive).
Thirdly, it is very easy to build an ineffective tennis ball platform. If the boards you use are too thick or stiff... and/or you use too many tennis balls, you'll have nothing to absorb the shockwaves that your impact's generate either directly (the kick pad) or through the rack/stands (the pads). All impacts will just go straight through the riser to the floor. Similarly, if the balls - sandwiched and clamped between the boards - are compressed too tightly, they will be ineffective... as the more you compress a tennis ball, the more solid it becomes. Essentially, the more 'flex' and 'give' the riser has (to a point), the more impact noise it will absorb.
And lastly, the platform will work at it's best if it is, for it's given size, made completely symmetrical and optimised for the kit only. I've noticed that some of the drummers on here have platforms that include them on it as well... and if that works for you, then that's cool... but the potential problem with that is that you'll inevitably need more balls where the player sits (to support the weight)... inbalancing the platform surface... adding more rigidity... and therefore taking away from the isolating properties that you're after. The imbalanced surface board can also potentially act as an 'amplifier' or a 'soundboard' to the impact noise creating increased acoustic noise, requiring possibly unneccessary additional mats/rubber surfaces to dampen it. And providing a less stable surface to play on.
So... with all this research, experimenting... and with the help of my neighbour monitoring the results in the flat below... I have finally got a solution that works. For me. I say 'for me' because this post is in no way attempting to be a 'definitive'. And I know there are lots of you out there who have alternative platforms that work really well too. For all you newbies out there... use the search engine and take a few days to read everything.
I've done some basic 3D CAD stage sketches of my platform with dimensions. See below:-
Ultimately, I went for the 'classic' two board design using 2 x 18mm Medium Density Fibreboard sheets cut to 1700mm x 900mm
(MDF is cheap, easy to cut and has a good balance of strength and flex). I cut the holes using a 38mmØ hole saw.
The image below shows the 'base board'.
I used 13 x Dunlop Fort All Court tennis balls (I got loads of them cheap from a local sports shop, unfortunately, now closed
down. I guess that's why they were so inexpensive). Now... you could use any tennis ball really. They're all fit for this purpose...
and worst case - even in the unlikely event of deflation - it's easy enough to replace them. I would however, recommend using
the same make/type of ball as they can (to my surprise) vary in... er... 'pressure'... for want of a better description...
(Shows how much I know about tennis...!)
Tip:- Don't use juggling balls (too soft) or dog 'throw and fetch' balls (too hard).
The image below shows the 'surface board' laying on the bed of tennis balls. The 'surface board' is identical to the 'base board'.
Mark out and hole cut each board individually. It's the most time-consuming part of constructing this platform... but don't try
to 'cut corners' or time save by attempting to cut both boards together. You'll get alignment issues and you might burn out your drill.
Clear the cut hole piece from the saw after each hole is cut... and allow the hole saw and drill to cool down periodically.
I've added a 20mm gymnasium mat as a layer to minimise acoustic noise. It's firm enough to play on without making a KD-8 for
example, move laterally or pendulum... but absorbant enough to stop the board potentially resonating. It's also acts as a covering
surface for the surface board ball holes. I've also used 6 x cable-ties on the edges (not shown) through the gymnasium mat and
the two boards to hold it all together... which will make it easier to move it as a unit should I need to... and will stop the surface
board potentially rolling off the bed of tennis balls).
The underside of the base board has 8 x 15mm deep heavy duty rubber feet to further 'point isolate' the whole platform and
to prevent potential sag if stood on. It also raises it enough so that you could run cables underneath it if required.
Here, you can see the layers used (from Top to Bottom):-
Protection Racket Drum Mat (folded back) - 20mm Gymnasium Mat - 18mm MDF - Tennis Balls - 18mm MDF - 15mm Rubber feet.
And that's what it all looks like. Well... actually, it's all hidden under the Protection Racket drum mat (essential to stop the
velcro'd pedals and KD-8 sliding). Note, drum throne not on platform. You know when you've made a good tennis ball impact
noise isolating platform... when you hit a pad rim full-on... and you can feel the slight 'after-vibration' of the rack through
your feet... you know the balls are working. Also when your neighbour stops moaning at you... that's a good sign too!