In this article, I will be giving a broad overview of the sub-domain of electro-acoustic, what it involves, various systems, and later articles will talk about key aspects of design. In future articles, I will be deconstructing certain key aspects of loudspeaker systems. While there are many applications of electro-acoustics, I hope to provide a good overview and understanding of common electro-acoustic engineering practices. I will not be doing these topics in any particular order. I will only be publishing these articles in the order of importance and when I have time. At the bottom of this article, I will list a number of sources. These sources work in aggregate. That is to say, that these sources provide the best explanation of key concepts and this set of articles aims to relate them.
What is Electro-Acoustics?
Electro-acoustics is at the odd intersection of acoustics, electrical engineering and mechanical engineering. It is the field of engineering that is chiefly concerned with the design and production of speaker systems, microphone systems, their occasional combination and the transducers. It plays a fairly integral role in the development of IoT devices (Internet of Things). I will be deconstructing the design of loudspeakers typical of professional grade playback systems. I will not be going over headphone design or microphone design. I will also not go over crossover design as filter design is an entire study and there is too much to discuss there. The following articles can be expected:
- Loudspeaker System Specifications
- System Testing Methods
- Drivers and Manufacturer Specifications
- Enclosure Designs
Unfortunately, loudspeaker design and electro-acoustics have very few substantial resources. This is partly due to the niche nature of the field. However, there are a few excellent resources that I personally refer to and you will find them cited in all of these articles.
[b1] High Performance Loudspeakers: Optimising High Fidelity Loudspeaker Systems by Martin Colloms – This is simply the best resource. If you read or buy any book on this subject, then this simply is the most important book. I just bought the brand new edition and it is even better than the last.
[b2] Loudspeaker Design Cookbook by Vance Dickason – I have a few objections to this book. It is fairly difficult to find but it is easier to read than Colloms’s book. The problem with this book is that there are many topics that are somewhat out of date or cater more towards PA systems than high-fidelity or small form factor systems. It is not my primary resource but if you can find it, it is worth a read.
[b3] Loudspeaker and Headphone Handbook by John Borwick – This book is almost impossible to find. It is a shame as it is one of the few that actually goes into headphone design in any sufficient detail. This book is actually made by a few authors and sometimes the notation is inconsistent.
[b4] Introduction to Loudspeaker Design: Second Edition by John L. Murphy – This book has some excellent explanations. Some portions are oddly worded but otherwise a great resource and much cheaper than the others.
[s1] http://www.linkwitzlab.com/ – This site is likely to go down soon as Linkwitz has passed away quite recently. He was an absolutely pivotal character in electro-acoustics. If someone manages to keep his site up then we are all lucky as there are many key articles on his website.
[s2] Kirby Meets Audio – This guy does not have enough subscribers. He makes great content. If you are looking for guidance for building a speaker without doing the calculations brought forth by hardcore engineering texts, then I suggest following his direction. Seeing or doing simple projects always puts things into more direct perspective.
[s3] GedLee LLC – Retired Electro-acoustics engineer with great papers and articles on the engineering.
I hope this set of articles will prove most helpful to those of you who are audio enthusiasts or acoustics engineers. Professional-grade loudspeakers are works of care and detail brought to market by teams of engineers. I sometimes feel that electro-acoustics is the only time when we get to create products or projects that have an understandable, tangible meaning to those outside the field of acoustics. It is akin to high performance sports vehicles, mechanical watches or computer modding. Because of that, I would like to leave you with a guiding principle for the next few articles:
Design is not just what it looks like and feels like. Design is how it works. -Steve Jobs
And on that note:
Be good to each other and take it easy…
Will Fehlhaber is an Acoustics Engineer and Audio Programmer from the UK and Bay Area.