TWEAKS: The cheapest effective one


Paul McGowan writes:

David Pogue, one of my readers, suggested to me “the cheapest tweak” that he’s ever tried and I thought it might be interesting, this fine Sunday morning, to give this tweak a try if you’re looking for something to do.

The tweak concerns extreme toe in of the loudspeakers – toe in that’s so extreme that the speaker’s acoustic meeting point happens 3 feet in front of the listener and when the sound actually hits your listening position everything you hear is on-axis at the wrong ear or off-axis for everything.

I have never tried this but it’s indeed interesting because the on-axis response would occur at the wrong ear for each channel, or if it were extreme enough no ear would get any on axis response at all. I have to think about this, but there may be some interesting things going on here.

For one, most of us setup our systems with just a little bit of toe in, or perhaps none at all. The trick is to get enough on-axis response from the tweeter so that the center image is solid and real in space, yet not so defined that the soundstage width and depth disappear – a tricky balancing act that takes a bit of time to dial in. The problem with this approach has always been that sitting to the left or right of center you loose the sweet spot because you’re nearer one channel than the other.

This new idea is pretty radical and at first blush completely counter intuitive. However, if we look a bit deeper into what we’re doing perhaps we can shed some light onto the situation. The phantom center channel image is a result of left and right speakers pointing at your ears enough so that when a mono signal is played (the center channel is always mono) both ears get an identical signal telling your brain that what you’re hearing is right in front of you – the depth of that phantom image dependent on the amount of “room” reflections included in that signal. If you think about it, this makes sense because the farther back into the room a single mono “person” is, the more room is picked up by the ears – and the further away this mono person appears to you (depth). To complete the mental illusion that the mono center image is further back in the room, the more room and surroundings info has to contain that mono image – which can happen if you reduce the direct info from the tweeter. By making sure both ears get the mono signal equally yet off axis, the ear/brain will give you more depth as the off-axis response has less high frequency information directed at it.

My guess as to why this might work is that it allows you the greatest amount of off-axis sound while maintaining a solid mono center image. Because the center image is mono, the fact that the left ear is getting the mono signal from the right speaker (and vice versa) doesn’t matter. I have read some follow up posts about this technique by Thorsten Loesch of TNT Audio that suggest exactly the opposite of what I just wrote; that in fact the on axis response is greater than with normal toe in – but that notion doesn’t noodle out in my mental picture. There’s a thread over at the Asylum that you can read up on that gives an even different explanation than what I wrote.

In the meantime, should you try this, please let us know what you find! Tweaks that are free, easy to do and take up an enjoyable Sunday listening to music are great things indeed.