Piano World Home Page Forums Our Most Popular Forums Piano Forum Upright Pianos and Walls - Principles of Acoustics?

The PW forums have a selection of discussions of how best to position an upright piano against a wall, with various contributors recommending experimenting with different distances, and even different angles, in order to obtain the 'best' sound.

However, as what counts as the 'best' sound will vary from person to person, and as the nature of the room in which the piano is placed will play a large part in generating that sound, I wonder if anybody could say something about the acoustic effects of varying the position of the upright position vis-a-vis the wall it will be back up against, all other things being equal. In other words, are there any general principles or rules, grounded in knowledge of acoustic properties and processes, that can be used to inform the placement of an upright piano in order to achieve certain desired effects or prevent undesired ones?

For example, if one wants to minimise reverberation, is the most logical thing to place the upright as tight against the wall as possible? Or perhaps as far from the wall as possible (e.g. in the centre of the room)? [I am ignoring matters of visual aesthetics here.] If one wants to dampen the bass, is there a principle or formula to assist this (e.g. placing the bass end close to a corner, or vice versa)?

I would appreciate any advice or knowledge anyone might have on this topic.

P.

As a guess I would say that putting it against a wall but slightly away from will project the sound into the room as well as boosting reverb, which will be more prevalent in a room with a wood floor-carpeting and other furnishings dampen reverbed sound waves. But if the room is large and wood floored then placing the piano in the centre of the room will give a good natural reverb.
I've never had a piano but I know that if you place loudspeakers in a corner you will get a bass boost to the extent that the sound can become muddy. I would assume a similar situation with an upright piano as the back of the piano is like one large resonator. I think they are normally placed against a wall but away from so as to deflect the sound back to the player while giving decent reverb.

Many thanks Larry.

I guess one of the questions I have concerns the relationship between the wall and the soundboard, and whether (or in what circumstances) the wall functions as a reflector and/or an absorber, and how best to utilise this to achieve desired results. I imagine that in some circumstances it will do more of one than the other, and I know that even such small matters as the wall covering (e.g. the paint) can have significant effects, but I just don't know how distance varies this effect by setting up reinforcing or cancelling waves, and perhaps even only for certain regions of the frequency spectrum. I've posted a more concise version of the question over on the tech forum in the hope that one of those with intimate knowledge of these things might have something to say.

Thanks again,

P.

I live in a bi-level condo. My living room is about 11' x 15', and extends to the dining room through the kitchen. When I first purchased my piano, I placed my piano on the wall against the stairs. This was because I thought that this would minimize piano sound transmitted to adjacent units.

This turned out to be a disaster. Since the space behind the stairs wall was hollow, the tone quality of my piano was terrible. Sound waves created from the piano shook the thin wall, creating unpleasing sounds only to be described as drywall rubbing against another drywall.

I also heard echos bouncing from opposite side of the wall, which made the whole piano sound pretty awful.

I then relocated my piano against the dividing wall, and purchased some sound absorbing panels. I put three small 1x2 panels right behind the piano soundboard, and placed the 2x4 are placed left and right of the piano. Same size panels are placed on the opposite wall as well.

This set up eliminated the echos and vibration I heard from the walls. But, it created whole another problem where I heard rattle coming from piano on certain notes. Additionally, piano sound was very muted since, three small sound panels absorbed most of the high pitch sounds.

Not satisfied with the result, I removed the three small panels behind the soundpanel. My piano sounded much brighter but the rattle continued. I put small felts on every contact point imaginable and lubricated the joints and tightened every screws I could see. Despite of this, the rattles continued.

Finally, I put the small sound panels below the big panels, and hung a large painting in the middle in between the panels. Believe or not, this set up worked. I have no idea how it happened not I can explain scientifically.

The final results are shown here:




The point of whole story, I don't think there is a way to predict how your piano will sound in your environment. There are so many variables go into it. Only thing I can say for certain, the sound panels greatly reduced the echos in my living room. I can only say through my experience. Please contact me if you have any questions.

Many thanks taeykwak.

I had been contemplating using some panels as well, but as the main problem appeared to be the reverberation from the tenor downwards, I held back. At the moment I have the piano as flush to a solid brick wall as possible, and this has reduced the reverberant mush of the lower half of the piano range. Still, looking at this pictures, I am puzzled how the two large panels to the left and right function, given their positioning in relation to the soundboard. How did you come up with such a plan, and how is it that they work?

Thanks and best wishes,

P.

As a sweeping generalization you can probably start with an assumption that ANY full range sound source placed between parallel hard surfaced walls will create enough problems to be worth attention.
The distance between parallel walls is going to be some multiple of the wavelength of a note SOMEWHERE in the piano's range.
Hollow walls, e.g. wood studs with sheet rock, are likely to be worse than brick, stone, or so called cinder block.
A low cost material for experimenting is rigid foam insulation, if it works and if you are handy enough adding a fabric covering and frame is simple enough.

Large areas of glass, e.g. patio sliding doors can be REALLY problematic.
HEAVY drapes or ...try a different room ?

Have you considered installing a couple corner bass traps? Corner bass traps, typically made of mineral fibre like Rockwool, are an effective way of dealing with excessive reverb in the low frequency area.

Keep the piano a 5-12 " away from the wall. Much of the tone is generated from the back of the piano. So squishing it up too close to the wall will allow the sheet rock to absorb a lot of the sound.

Thanks for this suggestion. Where, in relation to the piano, would suggest placing it? Directly behind it, between wall and soundboard? Or like in the above photos over and to the side of the piano?

P.

I have looked at some online, but am unclear how they work or are supposed to be used. For example, why is it a corner bass trap? What's the connection between corners and bass frequencies? [I'm pretty clueless on this, as you can see. ] And if I have two large bookcases going in to the corners, would they not mitigate matters?

Again, any suggestions, clarifications, are very welcome.

P.

I have pulled it out a little (maybe 2 or 3 inches) and will give it a run at this distance for a week or so. I gained increased clarity in the bass with the piano almost flush with the wall, and I want to maintain that as best I can.

Hi PN 040, My 2¢ ... being a reflective surface, the corner wall presents another source of interference between what you hear directly, and what you hear from all other sources (reflections from floor, ceiling and the other wall forming the corner). If the difference in path length taken by these sounds is an integer multiple of the wavelength of sound you are producing on the piano, then you get resonance. If not, the interference can be destructive instead.

For e.g. at about 10 feet difference, expect a bump in response about an octave and a half below middle C; at 5 feet, it would be an octave higher , etc. That's because (at 20°C) a sound wave with 10 foot wavelength would be vibrating at 100 Hz and that's around the 2nd A below mid C.

I think that's the theory. If any of it actually corresponds wth what you hear, I'd be amazed :-)

HTH

I'm not an expert on this, but in my layman understanding it's like this:

1, Low frequencies are not very directional. The waves go there and back in the room, you can imagine a pool of water and a big wave on it. In every round it makes through the room, it loses only a small part of its energy.

2, We want the wave to lose more energy in every round. To achieve that, we put a material that can transform the energy of air movement, into a place, where the air moves a lot.

3, the air doesn't move much near the corners - it has nowhere to go. That's the place where the pressure has maximum amplitude. That means, that at the distance lambda/4 from the corner, the air movement will be at it's maximum - excelent place to place the mineral fibre. For example, for 150Hz the lambda/4 is at ~20".

4, the mineral fibre material has a lot of very small cavities - the air will try to pass through them and will lose energy while doing that, because the cavities are very small.

Result: The corner bass trap (I mean the type that has a triange layout when seen from above, with two sides touching the walls) must be large enough to have mineral fibre near enough to the lambda/4 distance from the corner - that's their disadvantage. Other than that, they are very effective at reducing the low frequency reverb of the room.

There are many various designs and instructions on the internet - like this. One note though - it's wise to put the mineral fibre into plastic bags (plastic bags don't interfere with low frequency sound waves) to avoid danger of breathing in small fibre particles.

Regarding the bookcases in the corners - it can improve things, my guess would be not by much.

I'd suggest trying relocating the piano, even a small amount, changing the angle from the wall by a few degrees.

I was amazed several years ago with my 132cm Yamaha upright which seemed to have very little bass response when I moved house. It was placed in the corner, with the RH side about a foot from the side wall. I wasn't happy with it, but, just thought it was the acoustics of the (much smaller than I was used to) room.

A year later, when I had a change of furniture, I had to move it 90 degrees to the other side of the same corner - the bass response improved astonishingly. It was about 18" from the corner. Both times it was about 2-2½ inches from a wall. That prompted me to experiment - and found that the bass response improved further by moving the left end another couple of inches from the wall.

In your case, you want the opposite - so you may want to try the opposite. Maybe pushing the left end close to the wall and the other end further away may have the opposite effect? And, if you've got the option to move it, it could be worth trying.

A thick woollen carpet underneath, extending out at least a couple of feet to the side and beyond the stool in front can have a great sound absorbing effect.

Glass - windows and doors are the enemy of sound unless you want to increase reverberation. I tend to practise with my curtains and blinds closed - or my glass doors open, as I prefer the sound that way. Locating a piano away from glass if possible is a good move.

Alan

I have just moved an upright into a larger Edwardian house with a wooden floor and below the floor is a 3 foot space. The piano feet (no castors on this) sit exactly on the joist lines . There is a gap behind of about 4 inches .( Wider /thicker skirting boards hiding pipes ). The ceiling /wall moldings are a large foot radius curve all round. There are two solid brick pillars about 2 foot wide leading on to a bay window.and some light curtains . The opposite end has a fireplace with a log burner . The walls were covered with thick insulating paper 4mm thick . One question I should ask is whether thick insulating paper has a positive acoustic effect .
I described all that as I have never heard a piano sound so good before. No echoes , just very pure tones .The top octave was never the best but otherwise a startling improvement over the smaller room it came from .
On another similar topic I suggested the wall behind the upright could be compared to the lid of a Grand piano . So moving the piano into an angled position would release the full sound. I presume the full sound is what most players would prefer .I was surprised at all the efforts to suffocate all the vibrations before finding the best sound possible .
Even though the low keys and strings are at the left end of a piano the bridge line , where vibrations activate the soundboard , will be much further to the right if the strings cross over each other . Acoustics experts do not advise placing pianos in corners so we need to listen to them .
If you are made of money you could build a room as described above to get the best sounds .(See " How to make your Piano Room sound Grand .")

All I know is having a carpet placed in the room
improved the sound.The piano is tall and has
a very powerful sound.
While moving the piano it ended up in the middle of the
room, it sounded wonderful.At the moment it is
about 6 inches from the wall and also sounds fine.
Before we got the carpet the sound would reverberate
around the room and I could not hear the piano as
clearly as I now do.
I think the main problem was the hardwood floors
and the wall plus corner.
I do not know about the affect the insulating paper
would have on the sound but being so thick it should
modify the sound in some way.

The insulating paper is made with tough fibres . I had to drill a hole once and the fibres wrapped themselves around the bit and I had to try a different way .. Imagine that .Wallpaper so tough you can`t drill a hole in it . A sharp knife cut was needed .If you compare knocking on a hard plaster wall and then with this paper covering the sound is totally changed .Some energy is absorbed . If I designed an upright piano I would look at maybe opening some of the solid front to let the sound out .Just raising the small lid on top is not much .
How is an upright organised? Cross over the strings to make a longer string and a bigger sound then botlle it up inside a heavy wooden box .

Some uprights have open areas in upper panel or just below the
keyboard by the lower panel.Some have wider lids with a stick to
hold it up.
The YUS5 have an open area by the large music desk.

Another idea. You might also ask your piano technician about ideas on upright piano placement. My tech was quite helpful for getting the most pleasant sound out of my piano and where in the room my piano was safe from ultra violet sunlight, heating and cooling vents etc.
Also another piano friend built a small strong platform made of hardwood planks to hold their Steinway model O and keep it off the travertine tile floor. The hardwood platform really warmed the sound and because he built it himself the cost was minimal. I’m considering asking him to build us one for our piano sometime. It may take some experimentation and trial and error to get it right but in a sense that’s what makes acoustic pianos so wonderful. Best of Luck and please post pictures when you arrive at your solution.