Speaker grilles on or off?

Here’s a puzzling one: when it comes to your speakers, do you leave the grilles on ….or do you take them off? Opinions, opinions….

Let’s ignore for a moment the difference in aesthetics of your speakers with the grills on or off. After all, that is a very personal opinion. Let’s also ignore the fact that speaker grills may have a very practical purpose too. They protect your speakers from little inquisitive fingers and melodiously inclined pets. And then there is dust. Ignore it all.

Fact is that speaker brands usually design their speakers with the option of removing the grilles or leaving them on.  And while you may have a very good reason to leave your speaker grilles on, our burning audiophile question is: does leaving your speaker grilles on effect sound quality? Yes or No?

Diffraction in layman’s terms

To answer that question, we need another basic physics lesson. This week’s topic is ‘diffraction’.  Don’t worry, we’ll keep it very simple.

Imagine this. You’re speaking to an audience. Obviously, you want to speak clearly and makes sure everybody understands what you are saying without distortion, echoing and that kind of stuff. Now imagine you’re doing all that with a hand in front of your mouth.  There is no need to explain that it has a serious effect on how you’re heard. Sound radiates outward in a wave, and placing something in the field of that wave causes ‘diffraction’, interfering with the wave forms, changing the quality of your voice.

What we’re saying is, sound bumps into things on its way to your ears. Bumping sound waves interfere with the original waves. The result is smeared sound, ghost images and echoes.

Bottomline: The fewer things a sound bumps into, the less diffraction will distort the sound.

Diffraction for speaker engineers.

It’ll be no surprise that diffraction is a very important consideration for speaker engineers.

We just said that diffraction happens when sound waves meet an obstacle. When that happens the sound wave is distorted and it changes direction.

What’s important to speaker designers is the knowledge that this diffractions happens differently depending on the frequency of the sound wave. Different frequencies have different wavelengths. If the wavelength is bigger than the size of the obstacle, it acts like the object is not even there. So for woofers, diffraction does not tend to be much of an issue. For higher frequencies, which have a short corresponding wavelength, diffraction can and will happen.

So this is exactly why subwoofer grilles will not affect subwoofer sound at all. But sound waves of shorter wavelengths (tweeters and mids) will be affected by the grille.

(For arguments sake, we will point out that diffraction not only plays a role with the speaker grilles, but also in the enclosure and baffle design of the speaker as well as speaker placement. But that’s a different discussion altogether. )

Different speakers, different designs.

So back to our question of whether speakers sound better with or without the grille.

Now that we have an idea of what will make or break the sound coming from a speaker with the grille on ( the size of the grille), it’s obvious that exactly how that grille is designed will be of utter importance.

More often than not, it’s not so much the fabric that is the issue. That is acoustically transparent and the effect tends to be only very minor. It’s the frame that holds the fabric that matters. Remember how we said that the size of the object that’s in the way of the sound wave determines whether or not diffraction will be an issue. In a similar fashion, will a grille with a thick, protruding frame cause a lot more diffraction than a grille with a slight, minimal frame.

We have taken a few examples of different grille frame designs from Audioholics:

When comparing speaker response with and without the grille on a graph, the presence of the grille is evident on the response measurements done by Audioholics.  How much varies on the frame design. It ranges from ‘barely there’  (First frame) to ‘considerable dips’ (Second frame).

The effect on your ears

Now, measuring response and putting it out in a graph is one thing. What really matters is what your ears make of it.

When you listen to sound coming from your speakers, you don’t sit bang smack in front of your speakers like the microphones that did the response measurements did. It’s interesting to know that diffraction becomes less audible when you sit further away from a speaker than when you sit close to it. That’s because, before it reaches your ears, the sound coming from your speakers also interacts with the room.  In other words, what you hear from a sound system in a domestic environment is far more complex than what a microphone picks up in a reflection-free environment. Therefore in a real environment, the diffraction effects of grilles would be more subtle.

Because of that, diffraction from the speaker grille is very unlikely to be audible unless it is very bad. When it comes to diffraction and sound quality, nearby objects and bad speaker placement (like placing you speakers too close to a wall) are a lot more likely to be a source of diffraction that is actually audible.

So….

Does having your speaker grilles on or off affect sound quality?  The answer to that is a that generally speaking, speakers will sound better without the grilles.  But there is a definite difference between individual speakers. On top of that, it’s unlikely that the difference in sound quality between your speaker with or without grille will be a major one.

So, if protecting your speakers from little Johnny is a concern or if looks are important for your other half, don’t feel bad about having the grille on. You’re unlikely to notice. But for an audiophile listener, the small difference in sound quality may just be important enough.

Source: Audioholics