Decoupling a Rhodes Piano from the Floor

Hello,

I have a Rhodes 88 that I'd like to play late at night without disturbing people in my house or my neighbours.

Currently whenever I play, you can hear the strike of every key from the room below and even the tone of the chords being played. I assume my next door neighbour will be hearing some of this through his wall too!

I've looked at decoupling the feet from the floor using something like the Jahn IsoFloor & Piano Reductors but not sure this will make a huge difference.

https://www.thomann.de/gb/jahn_isofloor_piano_untersetzer.htm
https://www.thomann.de/gb/jahn_piano_reductor_208553.htm

The house is built from breeze block and timber. The Rhodes room is carpeted and I'd rather not take it up to install soundproofing underneath.  My concern with the caster solution is that they only occupy a small footprint, and the Rhodes weighs around 90kg, so they may not take the weight well, or dampen the sound that much with all the weight. I could spread the load and built a platform using mass loaded vinyl, but it would be large, a hassle to build, and also raise the keybed quite a bit.

One idea I had was to place sorbothane or another damping material between the bed of the keyboard and the flightcase of the Rhodes, which would (in theory) reduce transmission of energy from the keys into the casing, and therefore into the legs and floor below!
As you can see in the photos, the entire keybed lifts out of the case, including the harp which rests on top. The keybed base has a rectangular timber frame and a central support, under which I'd hope to put a suitable material - either in small amounts every 6 inches or so, or as a layer covering the whole underside of the base, depending on cost and what's most effective.

I'd hoping people might chime in with any similar experiences of isolating sound, suggestions why this may or may not work, or options for different materials worth looking at.

Thanks!

A picture of the keybed base

And one of the harp assembly

I would think that putting any material inside the Rhodes body would change the sound of the instrument.

mjrippe said:

I would think that putting any material inside the Rhodes body would change the sound of the instrument.

Click to expand...

My idea was to put the sorbothane/material between what is essentially the piano and the case - it won't be inside the inner workings of the instrument.. the Rhodes also doesn't have a soundboard as a normal piano does, so I doubt it would have any significant effect on the vibrations of the tonebars.

I'd hope the sorbothane would absorb more energy if the weight is distributed evenly as well, rather than across 4 small pieces under the feet.

> you can hear the strike of every key from the room below

So-- mostly a "thud" problem, with overtones of tines?

First thought is: move to the basement!

> carpeted and I'd rather not take it up to install soundproofing underneath

Don't. There is no way you can install enough mass or absorption to reduce low-low frequencies. Think 6+ inches of concrete or 4+ feet of fiberglass fuzz. Probably more. Not gonna fit or sit.

You want a high-cut filter, reducing 20Hz significantly and higher frequency even more. This is, as you know, a mass on a spring. To get the most mass, and avoid high keyboard, put the Rhodes and you on a platform. 3/4" plywood seems suitable. You probably need a 4x6 foot space for the both of you. This also spreads the thud to more floor joists (I'm not sure it helps but it won't hurt).

Then a spring. How soft? A possible goal is to get a 0.4" (10mm) deflection under normal weight (assuming 1 Gravity). This will resonate near 4Hz, pass 10% (20dB) at 16Hz, 1% (40dB) at 50Hz. (This seems to rule-out thin pads; a 0.05"/1mm static deflection passes 15Hz great and 50Hz is just 20dB.)

This mass-spring needs damping because the 4Hz resonance is mighty close to the natural period of many floor structures.

It happens that the wheel springs of a light car may be close to this. However they are awkwardly large, and undamped steel resonates well. Bringing over the car's hydraulic shock dampers might help, though car shocks may not damp micro-movements like a Rhode's hammers.

My thought is large foam rubber such as sold for patio chair cushions, even a foam mattress cut in 4 or 6 pieces. The deflection under a plywood platform, the Rhodes, and you may be near 0.4", can be adjusted with bigger/smaller chunks. The foam is fairly self-damping, by air, so should damp micro-shocks. And all the pieces can be recycled into a shed and patio cushions, or a lounge chair, so not a lost investment if it fails. You could even try for 2" static deflection (less foam area) which moves everything down an octave or 12dB; however you may get sea-sick.

I have used plywood on foam to isolate record players. Even with much less than 0.4" static deflection it helped.

In this image note that frequency is in cycles per minute, not seconds.

Building an inertia base is the best way to do it. That’s what PRR is describing. You can get spring isolators that restrict lateral motion. That way the platform won’t move around too much.

If you have a little air compressor or tire inflator you could use truck air springs. That will be the lightest and most portable way I can think of.

Suspend it from the ceiling?