Acoustics in cabinet for keyboard

Posted by: apokkalyps

Acoustics in cabinet for keyboard - 10/15/13 02:18 PM

Greetings! I am happy to find and this is my first post!

I am doing some research and I was hoping to pick your brains about a project I am planning. Although this involves an electric keyboard, I think it is better suited for the Piano Technician forum, as it is more a question of accoustics in a piano cabinet for which "piano people" would likely be more knowledgeable than "keyboard people". I hope no one minds me putting it here.

I have a Motif ES8 for which I am planning a piano-shaped cabinet to have built by a woodworking-savvy friend of mine.
I have scanned my rudimentary initial sketch here:

My default for building furniture without any acoustic implications would be to use 5/8s inch birch all around, with a stain. However, one of the great things about a real piano is you can feel the vibration of the whole instrument in your fingers when you press the keys, unlike a keyboard which unfortunately tends to be a bit lifeless in that respect. This is especially true for a studio keyboard with external speakers not attached to it's frame. I know there is no way to recreate the feel of a piano with a keyboard, not 100% and likely not even 50% or 30%. But I'm planning this cabinet and I think it would be interesting (if at all possible) to construct it in such a way that it might absorb vibration (from speakers) to provide a warmer sound and "feel" and vibrate the keys to whatever degree possible.

On the inside of the cabinet, behind the kickboard, I will have a pair of powered speakers, likely Rokit 8s. I am familiar with concepts like resonance, and I know that the acoustics of a piano is a very complex science and art, but the idea is that just as strings can vibrate a soundboard, (at least to a lesser extent) speakers outputting more or less the same frequencies could do the same(?). I'm wondering if you have thoughts about cabinet construction that might help simulate the resonating vibration of a piano. I was thinking in terms of things like a particular type of (not super rare) wood or thickness for the back "soundboard" or kickboard other than 5/8ths? Or maybe even fitting a soundboard off of an old parted-out upright piano?

Or if this seems like it wouldn't be worth the time and effort for the meager results it would yeild, I'd be interested in that opinion too. Thanks!
Posted by: MacMacMac

Re: Acoustics in cabinet for keyboard - 10/15/13 02:29 PM

I don't think you'll get good sound from your proposed configuration. There won't be much coupling from the speakers to the soundboard, and virtually none to the keyboard.

Also, the sound piped up through the cabinet and out through the front will be muffled by its travel along that path, though you might be able to EQ that somewhat.

I think it would be better to have speakers located in the place you've labelled "open front face", and maybe additional front-facing drivers in the kickboard. This could produce better sound (though it does nothing for your wish to have tactile response in the keybed).
Posted by: Jon Page

Re: Acoustics in cabinet for keyboard - 10/15/13 08:23 PM

Why build one? You could use a console which is destined for the landfill. I'm taking one there this weekend. The case looks good but the hammers are exploded and the bridges are cracked. Not worth fixing.

I'm sure you could find something in your area.
Posted by: Olek

Re: Acoustics in cabinet for keyboard - 10/16/13 12:48 AM

Originally Posted By: Jon Page
Why build one? You could use a console which is destined for the landfill. I'm taking one there this weekend. The case looks good but the hammers are exploded and the bridges are cracked. Not worth fixing.

I'm sure you could find something in your area.

That seems as the best idea.

You may also want a keyboard that provide enough inertia. I suppose many do today, trying to reproduce th feel of the action with masses turning on an axe.

Good idea to enhance your playing perceptions, let us know ow how it turns.

A "wooden frame" piano would do it better possibly, even if that sound terribly anachronistic and horrible. I have seen one mounted and was not as bad experience acoustically than expected. (a friend did that so I was generous!)

Correction, he used the actual action and mounted sensors under the keys... The acoustical part of the piano was out of order. No strings only soundboard.
Posted by: David Jenson

Re: Acoustics in cabinet for keyboard - 10/16/13 09:24 AM

I'd be inclined to use the Rokit 8s out in the open air where they were designed to function. These are recording studio near-field monitors. A lot of engineering went into the design of these speakers, and I'm afraid putting them in a cabinet would prove to be a big disappointment.
Posted by: SMHaley

Re: Acoustics in cabinet for keyboard - 10/16/13 03:35 PM

I concur with re-purposing an old gutted upright case. Why reinvent the wheel? Some consideration, if choosing that route, will need to be given to the height of the keybed against the height of the keyboard to keep playing height of the keys within standard dimensions.

In regards to loudspeakers I would give good thought to how it will be used. As many know a good percentage of sound from an acoustic vertical comes from the rear. If this application has it up against a wall most of the time speakers at the rear may be much less critical. I would use high quality open frame speakers mounted to the front of the upper case and each channel bi-amped (separate highs and lows). If projection from the rear is desired also units mounted to the old sound board my work reasonably well. A case with front tone openings, which many older uprights may have, would be preferable. I would not consider speakers below on the kick panel. It was never ideal for electronic organs and even less so for digital pianos.
Posted by: apokkalyps

Re: Acoustics in cabinet for keyboard - 10/16/13 07:10 PM

Thanks for your replies. I definitely considered re-purposing an old piano for this, in fact it was my first plan, but I decided against it because my ES8 is a few inches wider than your average piano, and also a piano junky (for lack of a better word) enough to be used for something like this would likely be pretty old and worn. If I'm putting the effort in, I'd rather something new with nice light stained wood to complement the matte silver of the ES8. Something my girlfriend would be happy to have in the living room wink

For the record: I already built one "stand" for it for back when I was in college, which was the perfect width (just a couple mm to spare on either side), and dealt with the height of the keys, which SMHaley is right is a tricky issue, but some of those things are solved already. The problem with the one I built though is it has a second shelf for synthesizers and stuff I don't use anymore and it's big, green and ugly ( Functionally that top shelf also gets in the way.

Anyway, if I make something new it can be exactly to my specs with no extra weight and look fancy and new.

As far as the speakers in the bottom, I see no one is too happy with that idea. I had thought to put the speakers in the bottom for two reasons:
1. To keep them out of sight, but more importantly:
2. As you can see in my green "stand" the speakers were where MacMacMac suggested to put them, but I always kinda wished they weren't so "direct" in my face. So I wanted to put them in the bottom to make the sound a little more dispersed and indirect. As well as hopefully vibrating the cabinet (and thus keys) some.

I fully intended to have an EQ mounted to the bottom of the "top panel" specifically for raising the highs/tuning the sound that comes up through the top. I expected some would be absorbed into the body of the cabinet to give it some rumble, losing some of that mechanical energy into the the body was the idea. Don't get me wrong, I don't mean to be stubborn and ignore the consensus. Do you think that even with a good EQ I wouldn't be able to tweak it enough to make that configuration sound good?

(other things: it will be pushed against a wall, and doesn't need to be concert-hall loud, rokit 8's might be overkill anyway)
Posted by: ando

Re: Acoustics in cabinet for keyboard - 10/16/13 08:57 PM

Sounds like you've given it a reasonable amount of thought, but don't bother with the Rokit speakers. These are near-field monitors: and will sound very poor due to being very directional speakers. I think you will want to mount speakers directly to such a case and install an amplifier in the case and work with an array of speakers from bass to mids to tweeters and some crossover networks. If you want the keyboard to vibrate, you could even incorporate a transducer under the keyboard. But all this depends on your level of expertise to get it done. Best of luck with it!
Posted by: Olek

Re: Acoustics in cabinet for keyboard - 10/17/13 04:17 AM

no speakers mounted on the soundboard in my opinion, if it was easy to do.

You may obtain alot of parasitic noises.

That said the experiment must be interesting, the "cello stand" made with an old piano must be enjoyeable by the player.
Posted by: guyl

Re: Acoustics in cabinet for keyboard - 12/16/13 10:09 PM

I have just finished building a compact grand shaped cabinet for my Yamaha P-155. As the initial poster mentioned, I was also looking for the vibration feel that provides that tactile feedback that is so much like a real piano. My solution was to use a 5.1 sound system normally used with a PC. I used this system that I picked up as a used item:

The 4 small speakers are mounted on edge (horizontally) at the front of the cabinet where the fallboard usually is, and the amplifier/subwoofer is set on its side on the bass area of the "soundboard" in the back, facing forward. The volume control/center speaker is mounted facing upwards just behind the music rack. Other similar systems could be used. It works great! The subwoofer really moves a lot of air and gives that reassuring vibration when you play bass notes.

Cell phones pics, but gives you the idea:

Posted by: TimR

Re: Acoustics in cabinet for keyboard - 12/17/13 11:04 AM

That is a work of art. Very nice.

Too bad it has only one pedal. My ancient Yamaha P500 has 3. But it doesn't look as nice as yours.
Posted by: guyl

Re: Acoustics in cabinet for keyboard - 12/17/13 12:56 PM

There is an optional 3 pedal unit available for the P-155, but as for most people, I don't need them. The next project: a matching bench!
Posted by: TimR

Re: Acoustics in cabinet for keyboard - 12/17/13 01:36 PM

Most people don't need 3 pedals on an acoustic piano either, but it looks wrong without them, and you've done so much to make this one look good.

At least set your one lonely pedal in a fake triplet pedal row! Obviously your construction skills are up to making a couple more lookalike pedals.
Posted by: guyl

Re: Acoustics in cabinet for keyboard - 12/17/13 02:32 PM

Funny that you mention that ("it looks wrong") because in designing and building this thing, I was going for the most classic, authentic look of a generic, black grand piano. Examples of that are the top shelf being recessed to the inside top level of the rim instead of overlapping it like an upright, and the added wooden strip on the lid to simulate the look of the front part of a lid that flips over backward. Same with the case cutouts at the ends of the keyboard being level and square tipped instead of the more common slanted cutouts often seen on digital grands. Yamaha's grand shaped Clavinovas all have those "quirks", which annoyed me. Same with the vertical fallboard panel meeting at a right angle with the keys. The P-155's flat and narrow control panel made this easy to do. But I didn't really think about the pedals all that much, probably because I could not see an inexpensive and compact way of getting it to look like there were 3 pedals. I used some wood panels that I already had for some parts and was able to keep the cost of the project at around $200. Most of that was for the bendable plywood used to make the rim, the oak veneers, and the finishing materials. Also, I wanted to leave the underside as uncluttered as possible because I sometimes like to add other things under there, such as a footpedal volume control and a H&K Rotosphere effect pedal (this is quite large) for a Hammond organ module that I will sometimes be using with this piano. The previous stand that I was using always made these accessories annoying to fit underneath. I finished it last Saturday (Dec 14th) and it is installed at the church where I play it. I used it last Sunday for the first time. The P-155 itself has been in use for a year and a half already. Well, if I ever come across an inexpensive 3 pedal unit that I could somehow integrate to it, I might do it ;-)

As for the amplifier (the original subject of this thread) I had originally thought about using one of those home theater sound bars as a way to get a long, thin line of speakers. But I could not find one inexpensive enough that could be easily used. These usually have to have a remote control to turn them on and off (you can't just leave them "on") and have wireless subwoofers, two annoyances and potential sources of trouble that I wanted to avoid. Finding a compact enough subwoofer was also difficult. That Dell sound system only cost me some $60 and fit the bill rather well. It puts out 100 watts and sounds wonderful. What remains to be done is design and build a small circuit that will power on the amplifier automatically when I turn on the piano. The P-155 has a port for a USB key and since it is a USB master device, it supplies +5 volts to the port for the key. I will be making a small circuit with an optoisolator and a relay which will detect this +5 volts as a signal to power on a relay and turn on the amplifier.

All part of the fun of doing these projects!
Posted by: SMHaley

Re: Acoustics in cabinet for keyboard - 12/17/13 03:27 PM

Perhaps a thread more suited to the DP area?