Frequency Response: let’s make it clear (part 1)

Frequency Response: let’s make it clear (part 1)

Following our previous article “Power, Sound Pressure Level, Let’s make it clear”, we’ll now discuss a topic that is mainly related to sound quality but also has many more down to Earth implications. As we said before, we would like our Partybag customers to be well aware and to receive correct information about our products, so we’d like to provide some basic explaination. If you are audio professionals you probably know it all already, but for all the others here we’ll try to talk in simple terms about a property of sound systems that is often “abused” for marketing purposes.

(Yes we do marketing as well, but let’s agree that there are many different ways)

It’s a complex topic so we’ll need two chapters, but don’t be scared, here’s the first.

This “Frequency” thing:

Everybody knows about the colors of the rainbow, those ranging from red to violet. What you see with your eyes is a combination of those colors, appearing in different proportions and mixed in many ways every moment in front of you. In a similar way, when you hear a sound, it’s formed by a sum of many components: as it happens with light, the different mix of those components will define what you will actually perceive.

Both for light and sound these components are waves, in the first case electromagnetic and in the latter mechanical. It’s like sea waves, but with air instead of water, and everything is happening in 3D with the air itself compressing and expanding periodically all around us. This can happen more or less quickly, or better said at different frequencies. Just like the sea surface shape is determined by short, fast ripples overlapping longer, slower waves, the sound we are constantly immersed in is formed by many waves at different frequencies. These frequencies the air around us vibrates to are a bit like the “colors of sound”, at least approximately.

How do we distinguish these frequencies then?

Unfortunately in popular culture there are no words as commonly established as “yellow”, and for sounds we often speak in vague terms about “low”, “medium”, “mid-high” frequencies and so on. The best way to describe the audible frequency range is to brutally use the standard unit: the Hertz. One Hertz (1Hz) means “once per second”.

The human ear can generally perceive frequencies between 20Hz, so the air compressing and expanding 20 times per seconds, and 20000Hz, or “20KHz” (from 1 KiloHertz = 1000 Hertz). However if you are exposed to noise during your workday, if you have a solid clubbing reputation as many good Partybag customers do, or simply if you are above 30 years old, it’s very unlikely you can still hear something above 16000Hz. Too bad. Evolution made us humans expecially sensible to our own voice of course, so the frequencies we hear the best are those typical of human voice, ranging about from 300Hz to 3500Hz this side of Barry White and Janis Joplin.

That’s great but… so?

So the problem we face as sound system manufacturers is a bit like we had to build a screen such as the one you are reading from. The screen manufacturer needs to show you all the colours and with some fidelity, so that a good photo on screen will show the colours as similar as possible to the real life subject in it. Well we have to do about the same! To be fair there are two main problems we face:

  • Building a speaker that is able to play all the frequencies a human being can perceive, or as many as possible.
  • Do that in a balanced way so that some frequencies are not too louder than others, just like in a screen you don’t want for example the blue to be much brighter than the red. If we don’t do that, what you record with a microphone will sound different when played.

In doing so we have to take in account two important differences between light and sound:

  • Sound waves are mechanical, so we need to actually move air and there is no way out from this.
  • The frequency range a human being can hear is very, very large compared to what happens for light (where colors correspond to different frequencies as well but in a different world, the one of electromagnetic radiation). From 20Hz to 20000Hz there is an entire universe, and the techniques used to create and handle the different vibration frequencies can change a lot.

After this much needed introduction, in the next chapter we will explain how you can understand the capability of a sound system when it comes to reproducing the various frequencies that form sounds in a complete and balanced way.

Power, Sound Pressure Level, let’s make it clear

Power, Sound Pressure Level, let’s make it clear

Still in 2019 there is quite some confusion around about all that concerns measuring a speaker output in general. Concepts like “power”, “sound pressure level” and similar are very often abused for marketing purposes, and we at Partybag don’t want to do that. We would much like our customers to be informed in an honest way about what they are doing.

We know many of our customers are professionals, but not necessarily in the audio field. The most common case is simply someone who needs a speaker to do whatever he/she likes or needs, and has a right to understand what to expect. So let’s try to explain this in simple terms without becoming too technical. All in all, if you are an audio professional you already know this, so move along! 🙂

Now: how loud is a speaker? There are two ways you can figure that out.

  1. Search for the Sound Pressure Level (SPL) in the specifications. That’s the measure, taken with an instrument called a Sound Level Meter, generally at 1m distance straight in front of the speaker, that is most closely related to what your ear perceives as “loud”, and that’s what we like to report in our technical specifications. Compare that with other speakers you know, compare that with a table like this one, get your own idea.
  2. Try it. Try. It. Seriously, there is no better way. In the end it’s you who will use it to do your own thing, it’s not a matter of show-off between different datasheets. And while you are at it, you can get also an idea of the sound quality, that is entirely another story, and in the end figure out if it’s ok for you. So go to one of our shops, come visit us in Reggio Emilia, ask a friend who owns it, that will always be the very best way no matter what.

What about power then? Power is that thing power companies charge you for at the end of the month, and that’s not even so true because they actually charge for energy provided (at least that’s how it works in Italy). Power is an electrical measure, not an acoustical one. A speaker does precisely the job of transforming electrical energy into sound pressure, and it can do that in so many different ways that the “power” figure barely tells you anything about what you are expected to hear. It depends on so many constructive details of the speaker that it’s basically pointless to talk about that unless it’s about power consumption, and by the way in a battery powered speaker you don’t want this to be high, right?

Also, people use tricks and in many cases you read about “peak” power, that doesn’t mean “the power I experience when I listen to techno at maximum volume” but a power that can be substained for a very very short time meaning a few seconds or way less, there is not even a standard. Are you listening to music for a few seconds? We really doubt that, that’s why we use good batteries. The power that makes more sense (but still you could just not care about) is RMS Power. Without too many technical details, it’s an average power that can be substained, and the number is normally a half or even a third or a quarter of the “peak power”. Again, there is not a fixed standard definition for peak power. And yes, music can also include short peaks or bursts, and peak power is also needed, but that’s definitely not the reason you read peak power around, or even just “power” unspecified. It’s just a cheap way to say “hey look I have more power!”.

But wait: isn’t, for example, a 200W speaker louder than a 100W speaker?

As we said before: it depends on how the speaker is designed, on the components, on many factors. But suppose you take two otherwise identical speakers and feed one with 100W and the other with 200W, what will the difference be? The answer is: just 3dB of Sound Pressure Level that means: audible, but just a little. Not so impressive, to be fair. In exchange for what? A much higher stress on the batteries, so either a reduced range or the need for larger batteries, more weight, more waste of space and so on.

Power is basically the last and easy resource you can use to gain some extra Sound Pressure when nothing else works. That’s why at Partybag we don’t take part in the pointless race of showing off a higher power figure, but we focus on efficiency and on the best possible tradeoff between sound pressure, battery duration, light weight and comfort.

In the end don’t mind power, mind SPL. Or even better, test our Partybags yourself! We have nothing to hide.

P.S. there are also other important parameters such as frequency response, directivity… but that’s for another day. Let’s start from the basics and enjoy the next weekend, with Partybag hopefully!

Partybag Staff