The concrete speaker project

Two industrial design students from Belgium, doing a Heavy project.

[concretespeaker]

Hey. Mads again, now logget in so that you can answer if still interested. If you are still working with this, then maybe we could exchange experiences?

Working on, Kinda… Doing lots of stuff and we’ve got to a difficult part in the creation process, being firmware. Will it ever be done? I seriously don’t know, I’m still a student and also helping on another big project, my friend is finishing his master thesis so when there is time we work on it but last semester it hasn’t been that much. If you want, I can post some pictures of the harware though, Works as far as i’ve been able to test it. On the acoustic part, we're still in the design phase simulating the aciustics. But exchange thoughts, sure why not. 

[concretespeaker]

Concrete

You might think; “Why do they use concrete as construction for the housing of speakers?” Well there are some good reasons for that when you want to combine the best sound possible with nearly unlimited possibilities of form.

The sound produced by a loudspeaker builds on the quality of its main elements, the driver and the housing. As modern drivers operate linearly a good loudspeaker enclosure should not oscillate (vibrate). Wooden and plastic enclosures have their own resonant frequency. They are able to reinforce specific frequency through vibration at certain points of frequency bands. The result is a distorted sound by means of basically, an inadequate housing.

We believe that choosing concrete is the right choice. Its strength and stiffness make the cabinet highly resistant to oscillation (vibration) and coloration (distortion of sound). The high mass and density of concrete contribute to high damping qualities. The strength of the housing even improves with age as the curing of concrete continues over time.

Producing the speakers out of a single mould (single body) using a homogenous construction design ensures a thoroughly rigid cabinet (joints are build in points of weakness). The inside is coated with sound-damping material to prevent any reflections in the monolithic structure.

On the other hand, concrete is pourable into almost any form. This aesthetical freedom makes concrete forms, by its very own nature, the ideal foundation for our sound system.

[concretespeaker]

This, Ladies and gentleman is the main PCB. This is the place where the music gets made, the beating heart you could say although I'd rather let the subwoofer take care of the beats.

As you can see, this thing is waaay into nerd territory. Yet we as designers made this ourselves. This is all to do with flexibility, by making this ridiculously complex thing we can fit a lot of functionality in a small place.

Ok, non-nerds, grab onto your hats Nerds, Let's get technical.

This PCB contains:

2 stereo digital amplifiers for the mid- and high channels (2x40W + 2x12W)

1 mono amplifier for the subwoofer (1x80W)

a DSP from analog devices with lots of sample rate converters.

BIG inductors

EVEN BIGGER capacitors

tiny capacitors and resistors too, over 300 combined

a Raspberry Pi gpio connector

Two fresh cat scratches.

a DAC from burr-brown

a ADC from burr-brown

30mw high-fidelity hp amp (the only analog amplifier in the system)

a USB i²s dac

Since the actual brains of this thing is a Raspberry Pi, anything the Raspberry Pi can play can be played on the system. Also, the only analog parts of the system are the adc, dac and headphone aplifier. all other audio connections are either i²s or texas instrument's purepath pwm. this creates near-perfect audio replication from input to amplification. The crossover, audio routing,volume, loudness & EQ is done in the DSP. The advantage of using digital filters (in the dsp) over analog ones is that you get the ideal filter scenario without expensive and big components. You can call it cheating but nearly all high grade audio equipment manufacturers use these techniques.

The main goal of this amplifier is to sound good. we hope that this will be the case. Got any questions? we'll answer them them on our ask page!

[concretespeaker]

The project

As the name suggests, this is a project dedicated to making concrete speakers. But aside from that, there is a whole lot more to this project than its surface.

We are designing and building these with the folowing ideas in mind:

Rock-solid sound: great speakers must produce great sound

Throw anything at it: This thing will handle anything from pillows to kittens. Also, it will connect to almost anything.

Simple on the outside, not so simple inside: User controls will be natural, sound processing will be all-digital.

The purpose of this blog is to showcase our progress through this huge project. And by doing so keeping a record of how the project has done so far.

[concretespeaker]

First renders of the design thus far