Introduction:
Welcome to our ES25 Final Project Site! We are excited to learn about designing and building a speaker and hope you enjoy the process of our work. We specifically aim to explore speaker casing design with the ultimate goal of finding out how far we can creatively push current speakers from an industrial design point of view. Here we will include weekly updates on our progress, design decisions, and problems that we face along the way.
Project Description:
We plan to build a working speaker, housed in a mechanical structure we design and fabricate ourselves. We will soon include a CAD mockup of what this will look like, which will shape the electrical components we choose to buy. Our speaker is inspired by the boomboxes of the late 1990s and takes geometric inspiration from appliances from the 1950’s. Based on our current vision, our speaker will consist of an acrylic front plate slotted with holes through which the sound is emitted. The back of the housing will be a rounded, thermal formed plastic casing. Within this casing, we will solder circuitry to connect speaker driver to a jack to plug in a phone. Once we get this to work, we will be able to analyze how this given geometry affects the sound from the speaker, and learn about geometries that will optimize the sound.
Motivation:
We chose to explore this specific aspect of speakers because we are both mechanical engineering students interested in product design. In a class combining music and engineering, we knew that we wanted to build something physical, and a speaker seemed like an exciting challenge. While we could have attempted to experiment with the electrical components of the speaker, many of the tutorials and how-tos we found online recommended strongly against doing so since the technology surrounding the electrical components is so complex and would require intense studying. More importantly, this project will allow us to gain real design experience as well as manufacturing skills to bring our design to life. These challenges and opportunities are what drove us to choose this project.
Background Research (how have similar problems been solved by others?):
- Most housings are made of wood (easy to work with or materialistically preferable?)
- Many subcategories of designs: single subwoofer designs, dual subwoofer designs
- For-sale design specifications
- Complicated speaker box online calculators (ex.) that take into account factors like width, height, depth, driver displacement, port displacement, wood thickness, etc.
- First decide frequency range hoping to achieve – (particularly the low frequency extension) will guide some basic dimensions related to the speaker cabinet design.
- Most basic and easy to understand shape is a cube/rectangular prism. Need more sophisticated software to truly understand more complex shapes.
- Well designed speakers need to be designed with a speaker software.
- Basic Designs:
- Sealed enclosure: A box, of whatever shape you wish, that is air tight -easiest enclosure to design and build. Stuffing the box with sound dampening material absorbs stationary waves produced by the back of the speaker and yields better results.
- Infinite baffle: baffle extends in all directions so even the longest sound waves don’t reach the edge of the baffle. The waves created by the back of the speaker never meet the waves created by the front of the speaker = no resonances, no diffraction. Cannot be perfectly implemented in real life. Real world= sealed box large enough so the air inside the box will not alter the compliance of the driver.
- Bass reflex/ported/vented: great balance between sound quality, output/efficiency, design and build difficulty. Port with predefined length and diameter to set the resonant frequency. Resonant frequencies come out the back of the speaker, reverse their phase and come out the port, adding with the waves from the front of the speaker. Alternative: passive radiator.
- Bandpass (of various orders): 4th order bandpass – one side of the speaker is placed in a sealed enclosure, while the other side is placed in a ported enclosure. The woofer plays louder than bass-reflex, but has a narrow frequency response.
- Transmission Line: Labyrinth on the back side of the speaker. Back waves generated by the speaker, travel through this labyrinth, which has a fixed length directly correlated to the wavelength of the resonance frequency of the speaker in free air. When the waves come out, they are in phase with the waves generated by the front of the speaker. Challenge: filling with specific pattern of damping material of different thicknesses and densities so all of the upper frequencies are absorbed.
This sounds fun! You guys discuss speaker software that aids in designing enclosures, etc. Will you try to find software to use to design yours? Or will you employ more of a trial and error method to optimize the geometry of the speaker?
Our approach is definitely more an a trial and error method. As you will see in our design approach post, the outer casing and geometric decisions have been made more for manufacturing considerations, but the filler materials and components and shaping within the housing will definitely be a product of trial, analysis, and retrial to get the best sound.
Hi Cole!
We’re actually letting the aesthetics guide the design of our speaker! One of the main aspects of our speaker we will be analyzing is how good the sound quality is when we select our electrical components for our casing as opposed to the other way around.
Designing a speaker is ‘black magic’ as Rob said and can be very complex 🙂 I am looking forward to what you come up with! One thing would be to analyze the sound and trace it back to design choices you made. As Jim said in class, use music that you know and like, to pipe through the speaker to get a sense of what the speaker is producing.
Thank you! Yes, we plan to analyze the sound and try to emulate other choices we could have made to understand the effects of our final decisions. More specifically, we plan to analyze the sound with different lining and foam choices to see which would have the effect we are looking for.