Zach and I finished a second iteration of the cardboard table-speakers! This time we outfitted the panels on the standing desk with a total of 4 transducers and one “subwoofer” transducer. The amplifier was also connected to a bluetooth receiver, making the sound system wireless!
The sound quality was much better and louder with four transducers! The hack was recently featured on Zach’s Kickstarter site. Although the funding period is over, you can still order and check out his site or store!
I read on the physics of speakers (Science of Sound – Rossing Moore & Wheeler) and found that the reason the table-speakers work better than expected is because it works more like the body of an instrument. Sound is all about moving air particles – the more air you move, the more sound you get. Speakers are designed so that they move air efficiently and equally across all frequencies. The larger the cone that moves the speakers…the more expensive.
What the transducers essentially do is turn the surface it is attached to into a speaker cone. However, the sound will be affected by the frequency response of the surface (cardboard in this case). Although you sacrifice sound quality, the gain in “amount of surface area moving air” is much greater. Think of it like a body of an instrument – a cello is able to fill a concert hall without amplification because the entire cello body is vibrating. A set of computer speakers would not measure up because the “amount of surface area vibrating air” is significantly smaller. But as long as the speaker “sound pretty good”, the novelty of cardboard speakers outweighs the discerning audiophile argument that the frequency response is uneven. Moreover, the increased number of “vibrating panels” means the table-speakers can be a stand-alone sound system!
Moreover, creating a “closed surface” is also key to making good sound speakers. There are different kinds of cabinets that aim to improve frequency response of a particular speaker cone. Simply having a vibrating cone in mid air without a cabinet or “baffle” creates a short circuit where the air simply moves “back” to low pressure behind the speaker cone. Thus, having a “cabinet” structure is really important. The speaker-tables have this cabinet structure “built in” by the fact they are radiating sound outwards and have a hollow interior. I wonder if there is a to design the interiors to better mimic speaker cabinets.
This iteration of the table-speaker brings us closer to the vision of an integrated performance surface. Now that the “output” has been figured out, I’ve turned my attention to figuring out the input. I was really inspired by Jie Qi’s research at the MIT Media Lab in paper electronics and am really excited about having the controls integrated on the surface of the cardboard.
I experimented with a a quick prototype using the makey makey and copper tape. It worked, but I think there should be a more elegant solution in which the copper tape circuit itself forms artwork on the table. The circuits can also be printed using conductive ink and made wireless as demonstrated by Dr. Kate Stone’s research. The cardboard could also be activated with piezo sensors and react to touch as demonstrated by Akito Van Troyer’s creations at the Opera of the Future lab.