Electronic Design
Soundbar Design From Start To Finish: Setting Design Specifications

Soundbar Design From Start To Finish: Setting Design Specifications



1 of Enlarge image



The future of consumer home audio has shifted. The priority has moved from having speakers and wires all over the living room to a single, intelligent product capable of emulating the audio experience of other multi-speaker installations. This is normally referred to as a speakerbar or its aftermarket term, a soundbar.

This article will help you get started in designing your own soundbar/active speaker dock by discussing the necessary requirements in putting together the spec list. Future articles will discuss the subsequent steps, including converting a marketing specification into a block diagram, converting the block diagram into a list of devices, suggestions for layout, and software architectures.

Set The Specification

The flat-panel television, which only started at around two or three inches thick, has rapidly become thinner and thinner. The fact that televisions are now mere millimeters thick is the deciding factor causing many manufacturers to push the amplifiers and speakers out to a soundbar (Fig. 1).

Let’s jump in feet first. Here’s a specification straight off the plate of a marketing team at a company I recently visited:

  • USB, S/PDIF, and 3x stereo analog inputs
  • Stereo analog inputs should support two voltage root mean square (VRMS) inputs
  • S/PDIF sources should be coax
  • Stereo output (two at 20 W each)
  • Analog subwoofer output
  • Wireless subwoofer option
  • Infrared (IR) remote control that supports the NEC or RC5 protocol
  • Audio processing features need to include speaker equalization (EQ), volume, dynamic range control, and SRS WOW HD

The inspiration for these sorts of projects often happens instantly, leaving the designer to record it on whatever’s closest. The picture in Figure 2 may or may not be the actual first draft of the specs. I’ll let you be the judge of that.

The Physical Constraints

The total product will be 36 inches wide, with the processing board located in the center and the speakers located at the extremes of the enclosure. The enclosure can be a maximum of 3 inches deep. Physical switches need to be placed across the top of the product, allowing users to control power, volume, and effects.

LED feedback displaying volume status, effects status, and other factors should be placed on the bottom right of the enclosure. This board should also have an IR receiver on it to ensure that users can always contact the system from the comfort of their couch.

It’s crucial in today’s home audio market that we provide a remote control of some kind, as well as basic control functionality on the product itself. Those of us with animals or kids know all too well how poor product design can wreak havoc on user accessibility: when the remote control goes missing, or when the batteries are removed in favor of the latest toys the children are playing with. For our example, we’ll use a standard IR remote control with a handful of buttons, running through a processor that generates IR codes in the NEC or RC5 protocol. If users lose the remote, they can rely on the buttons on the product itself.

Set Cost Targets

Let’s pretend that the idiots over in marketing live up to their reputation (note: I’m in systems and marketing!) and tout a list of requirements for the product and an end price, but have no idea if the engineering team can actually make the product to meet the price.

If you’re told, “The soundbar should resale for $99.99,” this actually means the item needs to sell for $79.99. Let’s break that down in terms of a real-world cost of build. From that $79.99 selling price, we need to take away:

  • Retailer profit margin (probably around 15% to 20%)
  • Distributor profit margin (about another 15% to 20%)
  • Profit that you need to make on the product (about 15% to 20%)
  • Cost of shipping the product to market (e.g., $8 for a product shipped from the west coast to the east coast in the United States)
  • Cost of assembly and test
  • Cost of materials (printed circuit board or PCB, components, plastics, speakers, and packaging)

“Front of building (FOB) cost” is the cost to build, test, and get the product on a shipping pallet outside of your factory. In the real world, it’s very realistic to divide the street price by four to get to the FOB cost. So with a street resale target of $79.99, that gives us a maximum FOB cost of $20.

What Are Your Competitors Doing?

As part of developing your solution and getting to the right price point, one of the tricks in your armory should be to look at, study, and have a healthy respect for your competition. In short, buy their boxes, conduct your own teardowns, make an effort to “cost” their product, and understand if you could build it at that price to make the resale (and your profit) targets. Not only will you learn quite a bit about their strategy, it will also prompt you to ask yourself some other questions. For instance:

  • If your competitor releases a product at a lower price, do you have enough profit in your design to lower your price and match it?
  • Is there anything in your architecture (such as the selection of the DSP) that would make it difficult to move to a newer, lower-cost platform (e.g., legacy code on an old platform that doesn’t have the price roadmap a newer platform may have)?

While copying their product would be highly unethical, and downright rude, learning from their cost-cutting practices can ensure you remain competitive. Studying the weak points of their design can also give you hints on what to improve in your own design, as well as ammo to use with the sales guys at Best Buy.

Design For Cost

So you’ve got your specification, you have your target bill of material costs, and you’ve opened the competitors’ boxes to have a look at what you’re up against. What now? What additional work can you do to reduce your risk and time-to-market, improve profitability, and generally make your life easier?

First, talk to your suppliers. Chances are, they have applications support people who are more than willing to do some legwork for you in finding the right part for your solution. Many will also have the skills to filter out many of the incompatibilities that you may not spot immediately (e.g., device A cannot run on the same power rail as device B).

Partnering with a solutions provider can also benefit you as you’ll have much more support when things aren’t working. When device A doesn’t work with device B, there is much more accountability to solve the problem when you’re partnering with a single provider, rather than one supplier blaming the other supplier for making shoddy products.

Where possible, look for commodity (i.e., second source) products. From a purchaser’s point of view, using multiple sources makes it easier to purchase products. However, if a silicon vendor offers you a product that differentiates you from the competition, take it if it reduces your cost or time-to-market risk. In the consumer market, we’re all looking for ways to differentiate ourselves from competitors. Working with your suppliers really can help you do this. It’s a win-win for both parties.

Finally, designing for cost also includes getting the best value from your R&D team.

  • In finance terms, that means getting as many products out of one development as possible.
  • In product manager speak, it means “multiple stock keeping units” or SKUs.
  • For the rest of the world, it means multiple end products that share one design and one PCB with either firmware changes or various stuffing options.
  • (Stuffing options are typically found on PC motherboards and have a lot of space with components that aren’t placed.)

In a soundbar, this could be something like a fully featured system with USB, S/PDIF, and analog inputs sharing the same PCB as the product that only has analog inputs. That allows you to save on the electronics and have two products released at the same time, at different price points. Lovely!

Introducing: The Value Soundbar/Active Dock

Now, we’re ready to start our design process. In future articles, I’ll show you how we took the specification above and turned it into a real reference design that you can copy and take to production. Each of the steps of development will be covered, and all of our logic will be shared. Hopefully, you’ll agree with most of it!

As each segment goes deeper, you’re welcome to provide feedback, ask questions, and offer suggestions through our E2E forum at E2E.ti.com (search: Value Soundbar).

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