Get "The Skinny" on Designing Omnidirectional Loudspeakers

Get "The Skinny" on Designing Omnidirectional Loudspeakers

Okay, I admit it's the skinniest video ever made! But you try to get these speakers in a frame with Axiom's Andrew Welker, who designed the Omnidirectional LFR1100s together with Ian Colquhoun. Watch the video (filmed in Axiom's anechoic chamber) or read the transcript below to find out what challenges are faced when you are designing loudspeakers with drivers on the front and rear panels of the speaker.

Andrew: Omnidrectional speakers are probably one of the more challenging types of designs that a loudspeaker designer can undertake. Part of the reason is that you have to deal with a lot of factors in terms of how the speaker interacts with the room, and how the different parts of the speaker interact with one another.

One good question that I often get is "Why omnidirectional in the first place? What's wrong with a conventional forward-radiating speaker?" And the answer is nothing. Axiom builds a lot of very successful models, including the award-winning M80, that are forward-radiating speakers. [Forward radiating speakers] perform extremely well, they image extremely well, and they can be totally neutral if properly designed.

What omnidirectional does is it just opens up the sense of space and proportions of instruments and singers and things that are going on in the musical stage. It also - for me, one of the most important aspects, and one of the most enjoyable - is the fact that omnidirectional speakers seem to have a sound that emanates from nowhere and everywhere at the same time. So the speakers essentially disappear. When that's done properly it really allows you to think for a second that you're now taking part in a live musical experience, rather than listening to a reproduction, and that's extremely compelling.

Sound radiates from the front and back of the LFR1100s


The issue with omnidirectional speakers as I mentioned is that they're tricky in terms of the interactions. One of the basic interactions which we can measure in a space like inside an anechoic chamber that we're in right now, is how the front and the rear drive units interact with one another. There's some issues with cancellation between those drive units and interaction between them, without even bringing the room and reflections into the equation. The only way that we've been able to overcome that is through the use of a circuit that incorporates a DSP or Digital Signal Processor. This allows us to tailor everything that's going on with the front drive units and the rear drive units independent of one another. That allows us to overcome any issues of negative interaction between the parts. This allows you to get a much more neutral tonal balance than a lot of omnidirectional and bipolar-type speakers that are on the market.

The other question I get very often is "What happens when you put this sort of speaker in different rooms? What happens if I place it fairly close to the room boundaries or the back wall."  Admittedly things will change depending on where the speaker is positioned, but that holds true for any loudspeaker. If you've ever moved your speakers around and played with positioning, you know that it impacts the sound. This sort of loudspeaker is no different.

One of the things we've been able to address is the rear wall positioning. Again, that's through the use of the DSP. If your speaker has to be placed fairly close to the back wall, we're able to compensate so that you still get the spacious full effect of the LFR speaker even though it's not maybe ideally positioned out in the room a couple of feet from the rear wall.

So those are a couple of areas that we've managed to address that really propel the performance of the LFR beyond any of our other products.

Read more about Axiom's Research and Andrew Welker.

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