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A Complete Overview of Speaker System Terms YOU should know!

When shopping for tech, you can often find yourself confronted with abbreviations and acronyms that confound, confuse and generally go unexplained in product descriptions or adverts. These "technical" terms may be glossed over by marketing and even customers, but they are actually vital deciding factors in which tech you pick up once you understand them!

Find out about the specifications of speakers like SNR, THD and RMS! (If you don't know what any of those mean, perfect! You will be an expert soon...)

Speaker Specifications and Metrics

First of all, lets identify what really matters when it comes to speakers. Most of us will be familiar with Decibels, a measure of volume, and that can be an important factor for many users. However, it is far from the only way of measuring speaker power and efficiency.

The terms we will cover are:

  • RMS (Root Mean Square) which concerns the average power of a speaker
  • THD (Total Harmonic Distortion) which concerns the audio range of a speaker
  • SNR (Signal Noise Ratio) which determines the quality and clarity of a speaker
  • Ohms (Impedance) which changes the efficiency of power use of a speaker

What is RMS For Bluetooth Speakers?

Our first term, RMS, stands for "Root Mean Square". While this sound like something straight out of a maths exam paper, the tangible effect this metric has on a speaker is much easier to grasp. The RMS value is displayed in Watts, and so we can tell it's going to be based around power in some way.

While a speaker might be rated for 30W, the RMS value will be much lower (For example, 5W for a portable speaker). So how can one speaker have two different Wattage values?

The higher wattage is the "peak" capacity for the speaker, the absolute maximum the parts can accept and output without breaking. However, this is not the average situation for a speaker. Most of the time, the speaker won't be overworking itself like that!

Therefore, the RMS wattage value steps in as a sort of "average" power use. The speaker might theoretically be able to handle 30W, but realistically it will be more likely to actually make use of only 5W it needs. That smaller wattage is the RMS.

Why Does RMS Matter for Speakers?

As RMS is directly related to the power supply and use of the speaker, different RMS values can drastically change the efficiency of a sound system. While you may not notice the difference in audio quality and in-the-moment playback, you may still want to consider RMS if you require long hours of high-power use or if you want to scrape a few pennies off of a high maintenance sound system.

An August WS350 Speaker

What is THD for Bluetooth Speakers?

Our second term, THD. stands for "Total Harmonic Distortion", which immediately sounds a bit more applicable than "Root Mean Square" from before! THD is a measure of speaker range and quality. A low THD means that a speaker is more accurately able to represent an original piece of music or audio. This is be due to the physical construction of the speakers and the electronics inside.

Imagine the circuit board of the speakers and all their components as a city. You want to hear the concert playing in the town square. However, the audience, the workers who funded the concert and even the taxi's that got the band members to the stage for the show itself are all causing their own noise. All the parts are working to bring the show to the town, but all the components are also able to disrupt it!

Despite a speaker being made to deliver audio, the components inside can inherently also disrupt that same audio. This is a basic explanation of how components cause THD purely by existing and carrying electricity.

Why Does THD Matter for Speakers?

It is quite clear from the analogy above that the concert would be much more enjoyable without the background noises, even if the sources of that noise are pre-requisites to the show! THD is therefore vital in determining how accurately a song or radio show or podcast is reproduced in the speaker.

A high THD can result in lost frequencies and lower audio range as components fight for the right to be part of the waveform. This can leave music sounding flat at best, or garbled at worst!

What is SNR for Bluetooth Speakers?

Our third term, SNR, stands for "Signal / Noise Ratio" and is a relatively self-explanatory term. Your speaker is trying to recreate the audio of a signal (Either from a radio antenna, Bluetooth reception or just MP3 file on a USB stick) and has many electronic and physical components working to that goal.

Therefore, similar to with THD, the components themselves are part of the problem as well as the solution! SNR is the ratio of recreated audio signal (The bit you want to hear) and "noise" created outside the signal (The bits you don't want to hear). The noise is mostly unavoidable, but can be successfully "drowned out" by the actual audio. The SNR determines this.

For example, an SNR of 50dB means the music is 50dB louder than the background signal. This means the signal might still be easily heard underneath.

Why Does SNR Matter for Speakers?

SNR is vital. A cheap set of USB speakers might create good quality audio, but if there is a constant buzz of signal underneath that audio then it nullifies the quality instantly. I use USB speakers as a prudent example, as the construction of USB-only speakers (rather than 3.5mm or optical ones) lends itself to low SNR.

An August MB420 Radio Speaker

What are Ohms for Bluetooth Speakers?

Our final term, Ohms, are common enough in other areas of tech. Ohms are taught as a measurement of "resistance" and "resistors" can be added to a circuit to direct and redirect the flow of electricity.

For speakers, though, the term is "Impedance". The idea is very similar. If a speaker has a low Impedance then the flow of electricity, and in this case audio signal, are able to pass more efficiently through the system. If a speaker has high impedance then the audio can pass at a much lower rate.

Imagine a motorway of traffic. A 2-lane motorway is impeding the flow of traffic by restricting the total amount of cars travelling at a time to two lanes. A 4-lane motorway has double the capacity for cars, and is not impeding their speed by creating a backlog.

For the two-lane motorway to process the same number of cars as the four-lane motorway, the cars would need to move twice as fast (and use more fuel to do so).

A Graphic of two motorways as described above. More red cars reach the end of the road at the same time with 4 lanes.

This is how impedance works for speakers. In order for a speaker with high impedance to perform how a low-impedance speaker does it would need much more power (like the cars needed more fuel on the 2-lane motorway in our analogy).

Why Do Ohms Matter for Speakers?

Impedance affects energy efficiency and, in cases where power cannot be properly supplied, audio loss. For the most part impedance won't affect your day-to-day use of a speaker, but for larger projects and power-management you may want to pay attention to the impedance of the speaker and keep it below 4 Ohms.

Wrapping Up

There's been a lot of abbreviations and a lot of analogies, but now we understand how SNR, THD, RMS and Impedance can affect your speakers. In some cases it might be an issue of power supply and efficiency, but some metrics actually effect the audio output directly and can cause otherwise good-sounding speakers to suddenly sound awful!

Our WS350 speaker features THD of under 0.5% for perfect audio recreation, and boasts an SNR of a minimum of 75dB! The WS350 connects via app to play in any room in the house in unison with other Wifi speakers.

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