A closer look at the BoomSound speakers from HTC. Part one

Based on materials from blog.htc.com

The quality of sound output is far from the first place when we choose a new phone. We are attracted by the properties of the camera, the user interface, the look of the device, and we think about the sound in the second place.

But nowadays smartphones are increasingly replacing TVs and computers for us, and watching videos, playing games and listening to music on them has become a habit. And this means that the manufacturer must provide quality sound, no matter how much the users themselves think about the sound.

For HTC their BoomSound front speakers have been something of a pride since their introduction on the One M7. The current partnership with Dolby has brought 5.1 surround sound to the One M9 and a number of other devices from HTC, from which you can get a theater-like surround sound experience without using headphones or external audio sources, right from your phone. The work that went into before the Boomsound audio system came along is well worth telling. Over to Jude Wang of HTC Community, who will question the BoomSound developers about how these speakers came about.

Speakers HTC BoomSound speakers are valued for offering the best audio experience in the industry. What were the motives behind their developers?

It all started with HTC One M7. Minimizing the size of the case is important for any smartphones, and the ideal option is when all parts of the device take up minimal space. In terms of priorities, speaker size and sound quality are inferior to camera features and screen size, which always come first. But in reality, we use smartphone speakers every day, for example, when we listen to music in the car or play games.

Why are the speakers in a smartphone always placed at the back or sides?

The speakers on the back of the smartphone placed everything in a row, well, or in some cases they hit the ends. The reason is that the front speakers would increase the length of the apparatus and affect the structure of the apparatus and the shape of all internal elements.

Before there were dual front speakers from HTC, no one expected anything other than the earpiece at the top of the phone, because replacing it with a micro speaker would require placing the resonator in an already filled space, plus additional technical complications to accommodate various international loudness standards.

Let's just say it's not so difficult to install speakers at the bottom of the device – in almost all smartphones they do this, because the upper part is already occupied by the main and front cameras, a headphone jack, etc. Putting the speaker on top also means that you are trying to squeeze it into an extremely uncomfortable and already occupied space.

Due to space constraints, we were forced to change the shape of the resonator for the sake of the speakers, but this could result in an unpredictable result for the sound. This is why you rarely see speakers with unusual shapes – they are usually rectangular, circular, or cylindrical – to avoid distorting and degrading effects. This was our problem when creating BoomSound, here the unusual shape of the speakers.

When we first looked at the design, we really wanted to cut corners here and there, but that would have shortened our work area. I had to work with what we have. But what was to be done with the resonator? Could we achieve the correct re-reflection of a sound wave in such a narrow space?


The arrangement of the elements at the bottom was relatively common, but the top promised to be non-standard, as seen in the sketch. We thought about different options, up to punching holes in the front and back or sandwich-like designs. Simply put, we needed to win as much space as possible by any means possible.

We had several ideas, one of which was to change the material, and we started adding filler to the resonator. It is made of high-polymer material, very similar to a sponge. The 'sponge' should reduce the speed of the air that enters the resonator, thus slowing down both the reflection and refraction of sound. The refraction rate is really limited by the resonator, which cannot be greater. However, the sound that gets in has to travel a longer distance, and this mimics a larger resonator, making your ears perceive the sound as louder.

This solution gave a really significant result plus the advantage of better sound insulation. But how that would affect production was another problem. It was necessary to make something of an irregular shape out of the material, covering it with 'breathable' wool on the one side, and with plastic on the other to ensure free air flow, all inside a tiny space of just over 1 mm.

Assembling the speakers became a challenge in phone manufacturing, as the material could easily be damaged or simply spilled on the table like powder. Therefore, clear rules were set for those involved in the assembly, such as the minimum pressure that can be applied to each component, or checks at each stage for damage. It took an incredibly long time.

Squeezing a speaker into an already packed space is a tricky business, which is why most smartphone manufacturers choose not to. However, HTC are not the only ones trying to use dual front speakers – nothing is impossible, it just takes a lot of effort and time.

When the conversation about BoomSound speakers just started, there were many problems, discussions ahead, and everyone understood how much work and costs all this would entail. But in the end, HTC chose to provide the best user experience possible, the investment was worth it, and therefore no compromises were possible.

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