Should you toe-in speakers?

When to toe-in speakers 

Hi-Fi speakers don’t radiate sound equally in all directions – at least, not above bass frequencies. At midrange frequencies, where most melodic and vocal elements of music are found, and at high frequencies where cymbals and the fine details reside, speakers radiate more strongly forwards than to the side or rear. This directional effect becomes more pronounced as frequency rises, so at those midrange frequencies the effect is relatively subtle. But at high frequencies, speakers will typically radiate almost no sound backwards. The diagram below shows typical speaker frequency response measured by placing a microphone directly to the front (red curve) and off to the side (green curve). The green curve shows the speaker output falling away as frequency increases. If you have space behind your speakers, you can experience this effect by listening there for a moment. You’ll hear that the high frequencies have all but disappeared and midrange frequencies are less prominent. But what has the directional nature of speaker sound radiation got to do with toe-in? Stay with us and we’ll explain.

When we listen to speakers, we hear not only the sound that reaches our ears directly from the drive units (the woofer and tweeter), but also the sound reflected from the walls in the room. Our ears and brain make sense of these different sounds in the following ways: 

• Firstly, the brain latches on to the direct, un-reflected sounds to build a picture of where they’re coming from. It does this by deducing direction using the difference of sound volume level and arrival times at our two ears. For example, a sound that’s located to your left will arrive at your left ear just before arriving at your right ear. It will also be slightly louder in your left ear because it’s masked from your right ear by your head. Stereo speakers use this ability of your brain to create a stereo image, which effectively tricks your brain into hearing phantom sound sources. 

• The second way our brains make sense of the various arrivals of sound in our ears concerns the reflected sounds that have taken a slightly longer journey via the walls of your listening room – in particular the side walls. The reflected sound influences the overall tonal character – bright, dull, warm, natural, coloured, etc. The brain creates a composite tonal character by combining the qualities of the direct sound and the reflected sound. If a speaker has narrow dispersion or a particularly uneven off-axis frequency response, it can sound coloured. It’s also worth noting that if the reflected sound is strong in comparison to the direct sound, it can dilute the arrival time signals the brain uses to create the image, which can make it less precise. 

It’s within these two areas that the significance of speaker toe-in lies.

Hi-Fi speakers are usually designed to have a flat frequency response on their central forward axis, which means they’ll accurately reproduce the balance between bass, midrange and treble elements of music. When they’re angled – toed-in – towards the hotspot, that’s where the most accurate response is heard. But, because speakers are directional at mid and high frequencies, the sound that arrives at the hotspot via reflection from the side walls will have the speaker’s off-axis, and probably much less flat frequency response embedded in it.

What angle should I toe-in my speakers 

The appropriate toe-in angle to start with is related to how your speakers are positioned in the room. The usual arrangement is to view the listening position as one apex of an equilateral triangle, with the speakers forming the other two apexes. In this arrangement, the distance between the speakers will be the same as the distance from each one to the listening position, and it will result in a 60° total angle at each apex. So, if you want to toe-in to point directly at the listening position, it needs to be angled inwards by 30°. In the majority of speaker arrangements, any more than 30° toe-in is likely to be unnecessary and may well result in compromised performance, but experimenting is the key, as varying the toe-in angle will modify the ratio between direct sound and reflected sound at the listening position. Here’s how what you hear will be affected by adjusting toe-in: 

• Less toe-in – typically results in more prominent reflected sound and so potentially a less focused stereo image at the hotspot. It can also result in a more even tonal quality across a wider range of listening positions, as the reflected sound will be less affected by the speaker's narrower dispersion of mid and high frequencies. 

• More toe-in – typically results in less prominent reflected sound and so potentially tighter stereo image focus at the hotspot. But more toe-in might also mean that listening away from the hotspot is less satisfactory as off-axis and reflected sound will likely dominate. 

If that all sounds a bit over-technical and geeky, there’s a simple principle at its core: more speaker toe-in typically optimises stereo performance at the hotspot, while less toe-in typically results in a more rounded presentation that’s perhaps more suited to shared listening. Try adjusting the toe-in of your speakers and see if you can hear the effect. But what if there was a way of re-casting speaker design so this apparent compromise could be avoided?