PSB Imagine T3 drivers Speakers

What is Off-Axis Speaker Response and Why Should I Care?


You may have heard of off-axis speaker response when perusing speaker reviews. The reviewer may say a speaker has good or bad off-axis response and may or may not say that is a good thing. Some reviewers seem to care about off-axis response, and others don’t. So, what is off-axis speaker response and why should you care?

Definition of Off-Axis Response

When setting up your front left and right speakers, you’ve seen a lot of diagrams with lots of suggestions. Some look like this:

Dolby Atmos 5.1.4 Atmos-enabled speaker layout
Image courtesy of Dolby.com

Others look like this:

Image courtesy of Denon.com

In one image, they are more or less pointed directly at you. On the other, they are pointed straight forward. Which is correct?

Neither. Or both. It depends.

Every speaker produces sound (wow, we really are taking it back to the beginning, aren’t we?). The lowest bass, as we’ve described before, is omnidirectional. When we are talking about off-axis speaker response, we are really talking about the tweeter. Let’s do an experiment.

Play a test tone out of your speaker (Don’t know how? We walk you through it here.). You could technically do this with any speaker but we suggest either the front left or front right speaker. Now, stand directly in front of the tweeter, about three feet away. Staying three feet from the speaker, move to one side in an arc. Listen closely. At some point, the timbre of the sound will change. It may be quick, or it may take a few steps. But it will happen.

That is off-axis speaker response.

At some point, as you move out of line (off-axis) with the tweeter, the speaker will start to sound different. That is neither a good nor a bad thing. It is just true. It is what you do with this information that is important. In general, however, a “good” off-axis response refers to a speaker sounding the same as on-axis for a wide range (usually up to 30 degrees). Poor off-axis speakers would change their sound quickly as you move off-axis.

What Does Your Speaker’s Off-Axis Response Mean?

In the end, this information will give you an idea of how to angle your speakers. If you read that a speaker has poor off-axis response, you may want to have them pointing more toward you. If they have great off-axis response, you can have the pointed more forward and get the same results as pointed directly at you. But what if you don’t know?

Testing Off-Axis Response at Home

If you have new speakers and don’t know what to expect, do this simple test. First, have the speakers pointed directly at the main seat in your home theater (this should be the one equidistant from the front left and right speakers). This is directly on-axis listening. Listen to a track you know well. Now, reposition the speakers so they are pointed straight forward into the room. This is off-axis listening. Listen to that same track again. Does it sound different? Better? Worse?

If you have a track with side-to-side pans, does the pan seem to go farther to the left and right when the speakers are in one orientation than another? Do the vocals seem like they are coming from the two speakers individually in one orientation and from the middle in another? What we are looking for is the widest soundstage (left to right) we can get with the center image (vocals coming from the middle) rock solid.

If you find that your soundstage is the same in both orientations, and the center image is fine as well, you can place your speakers however you like. But, and this is much more likely, if you find that the center is good when the speakers are pointed at you, but the soundstage is wider when they are pointed out, you have some work to do. Slowly change the speakers’ angle from pointed directly at you to more and more pointed forward. You’ll have to do this iteratively, obviously. This will look like the speakers are firing over your shoulders. Eventually, you’ll find a “sweet spot” where the center image is solid and the soundstage is wide.

The Caveat

When we talk about speakers, we make a couple of assumptions. One is that the on-axis response is designed to be desirable. That the designer assumes that at least some of the listeners would position the speakers directly at them and that the speakers would sound good.

This is not always the case.

There are some speakers on the market that are ONLY designed to be experienced off-axis. The speaker designer never intended them to be pointed directly at your seat. These speakers are tuned so that their response is most pleasant when heard off-axis. Usually, the manufacturer will include setup instructions for these speakers indicating how they should be aimed. Not always. Trust your ears.

What About the Rest of the Speakers in my Home Theater?

When you hear about off-axis speaker response, you rarely hear it outside the context of the main left and right speakers. If you think about the shape of your ears and how the rest of the speakers are positioned, this makes sense. The center is essentially in the place where the sound it makes is supposed to come from. The surrounds and overheads are as well. Plus, your ears are shaped so that they very accurately capture the sound that comes from the front. Not so much from the back and overhead.

The front left and right speakers often have to not only create a wide soundstage, but often a center image. Plus, they are doing it from an orientation where your ears are most sensitive. Improperly placed front speakers can seriously undermine the listening experience.

Conclusion

In the end, it is important to know how your speakers perform when they are off-axis so that you can properly position them in your theater. A speaker with a good off-axis response is desirable because a larger listening area can be established that can all hear the sound as it was intended. While not all speakers are designed with large listening areas in mind, this is usually the case for home theater. Once you have your speakers properly positioned, you can rest easy knowing that everyone on your couch is hearing the same thing you are.


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