Electro-Acoustic Design Guide Part1

brad saylor
Oct 16, 2023
5 min read

Updated: Nov 7, 2023

Six Key Questions

Introduction

In this blog series, my goal is to introduce the multi-disciplinary processes involved in realizing a new product design.

The plan is for five installments:

Part 1: Intro and Six Key Questions
Part 2: Determining Bulk Parameters
Part 3: Designing for Performance
Part 4: System Modeling
Part 5: Preparing for Production

When we are done you will understand the steps, skills, and resources entailed so you can plan for and start your own project.

The main audience is considered to be those involved in engineering management and product planning. The information provided will be technical in nature, especially from part 2 onwards. That being said, there will be useful information for the audio and electronics enthusiast alike.

My own perspective is that of an engineer with two decades of experience in the field. I’ve designed systems meant for just about every market segment, from portable to high end. I know what it takes to start well, execute consistently, and finish with a successful product.

With that out of the way … let's get started!

Getting what you want requires knowing what you want. An active speaker project lives on several important axes. Identifying these degrees of freedom and where you sit on each is the right place to start. I have identified seven here to get you started:

#1 Who's Driving? Pick ONE (two if you must…)

Cost
Schedule
Industrial Design
User Interface
Novel Features
Performance
Reliability

Above is a list of commonly encountered priorities for a speaker project. To be sure, you'll need to hit the mark on each, but there can only be one king so priortization is essential.

Engineering, like most of life, is about tradeoffs; and a sure way to failure is to rank everything as 'most important.' Here are some notes on each:

Cost

Let's be honest - this one wins more often than we admit. Strictly speaking, you have no product if you don't have a case for profitability. If your budget is especially tight, you can skip prioritizing the items on the rest of the list.

Schedule

Business opportunities come at a certain time and place. No opening lasts forever. If your window to have a final product is exceptionally narrow, this must be your first priority.

Performance

Admittedly my favorite. If your brand depends on it and your customers demand it (lucky you!), then give them something to be proud of.

Industrial Design

Is your widget a speaker with style, or a lifestyle/fashion/status-symbol that happens to play music? No judgement here (well … maybe a little), but, if the latter prevails, let's call it what it is from the beginning and nail the ID.

User Interface

Often overlooked and frequently has the #1 impact on your customer. Simplicity is harder and more expensive than it sounds. Software development/maintenance and responsive UX design take time and investment.

Novel Features

A longer feature list on the product page is a meaningful differentiator. Wi-Fi, Bluetooth, the latest CoDec support, big tech service integration, AI … the list goes on. The more you add, the more complex and expensive it will be to establish a well-behaved ecosystem. If you've hit critical mass with features, this should be the focus.

Reliability

Does your customer demand stone-cold dependability? Sometimes 'fiddly' is conflated with 'advanced,' but other times frustration is not an option. Outdoor and commercial installations are examples here. If you need to build a tank, it will take time, money, and a lot of testing. Allocate accordingly.

#2 What is Your Price Point?

Different market segments command markedly different pricing and margin schemes. A competitive analysis will show where your product sits in the pricing landscape. A BOM plus manufacturing costs combined with predicted sales volume allows you to compare the bottom line between product conecpts.

#3 How Big Can it Be?

Get in touch with your customer's opinion on size vs. performance. The expectations will vary by market segment. Once you know your limits, commit every available cubic millimeter to acoustic volume - it's the cheapest performance boost.

Determine dimensional hard stops at the outset, e.g. a sound bar must fit under the television. Combine this with the overall fidelity requirements, and you now have a good idea of the engineering challenge ahead.

There are a few ways to buy yourself out of a small box. Explore a bigger amplifier with larger heat sinks and driver coils. Or a novel DSP where current trends use psycho-acoustic principles to squeeze more perceived bass out of smaller form factors. Keep in mind, however, that physics subversion is often impossible and always expensive.

#4 How Loud Will it Play?

A personal audio product would have much tamer requirements than a concert stack. Determine your required sensitivity (dBSPL @ 1W) and needed amplifier power.

A 'louder' system is the easiest way to differentiate a product. Customers consistently equate louder to better. So unless your niche is ultimate audio-philery, you cannot afford to be significantly quieter than the competition.

To get there, you'll need to match box size, woofer size, and amp power to the requirement. If the application permits, DSP can be leveraged to boost average loudness via signal compression. This approach can be as sophisticated as you like but requires a deft hand to avoid nasty and very audible artifacts.

#5 How High is Your Fi?

Fidelity implies a clear rendition of all information presented to the speaker. Technically this can be demonstrated by a flat and extended frequency response. Premium systems usually tout this quality.

A flat response, however, may not be required or desired for all scenarios. Perhaps your product deals in low bit-rate audio where chasing flat would be a waste. Perhaps your product has a distinct timbre which resonates with consumers. Remember all the hype around the 'vinyl sound' … a.k.a. 2nd order harmonic distortion?

Fidelity has a context. The best advice is to know your customer's listening habits. Find a way to offer an engaging experience in the most likely use cases. Your choice of listening material during the tuning process is critical and may not reflect your all-time favorite tunes but should reflect the variety of genres your users enjoy. After all, keep in mind that a terrible performance with one audio format or genre may outweigh your success everywhere else.

Your competition probably makes outlandish performance claims. Don't sweat the hype. Your target buyer isn't dumb, but they may be ill-informed. That's where you come in. Bring some targeted information to the equation. State your advantages simply with strong and hopefully truthful supporting evidence.

All this is to say that fidelity is a three step process. Determine what is required to meet minimum performance goals and get that down pat. Then supplement the design with differentiators that show your unique value proposition. Lastly be prepared to back this all up with engineering rigor.

#6 How Robust is it?

If your product fails sooner than expected, you've lost a customer. Understanding the use case is key. One system may need to resist water and debris ingress while another needs to function for long periods of time with zero maintenance.

A deck speaker exposed to rain, wind, and dust may place a higher priority on longevity than pure fidelity. A commercial sales display may receive little attention on-site making ultimate reliability the priority.

A truly robust design requires forethought. From specialized materials, to sealing geometries, to conformal coatings; things can get complicated and expensive. Know the performance you need and how to test for success.

Conclusion

Answering these questions is a great place to start. Beyond the obvious benefits to budget and schedule planning, you will also begin to see conflicting requirements. These need to be resolved at an early stage in the process for a viable concept.

Conversely, you may find synergies to improve your original ideas. With a realistic and self-consistent outline of your core product, you are now ready to proceed with an improved chance of success.

About Your Guide

Hi I’m Brad!

With nearly twenty years of experience designing, testing, and measuring electro-acoustic products, I bring a unique systems perspective to the consumer electronics development process. I’ve worn many hats throughout my career, developing competencies which span from ideation to mass production.

If you need assistance with your product, I’m hear to help. Reach out at brad@saylorsound.com or my contact page.