Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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RE: either way, I hope you don't nod your head to the music!

Posted by David Aiken (A) on November 23, 2008 at 15:20:35

In Reply to: either way, I hope you don't nod your head to the music! posted by dave c on November 23, 2008 at 12:53:15:

Yes :-)

Or at least extremely close to such precision..

It is hard to measure tweeter to ear distance precisely. Holding a tape measure in contact with the tweeter is not recommended and I don't think my head ends up in exactly the same spot every time but measurements to within a mm or two are quite possible and a lot of that mm or two 'error margin' is going to be related to head movement.

I tend to measure from the baffle plate, and actually use a plumb bob to mark a spot on the floor directly below the baffle of my monitors as a start for the measurement, and measure to a point on a midline bisecting the speakers which is as close to immediately below my head as I can ensure. I might be able to get a bit more accuracy there if I had a second person present to help while I was measuring. My process was probably slightly different from Jim's:

- establish the midline between the speakers and mark a point halfway between the front wall and the wall I use as the 'back' wall, given the bend in the L shape is in that wall. That point is the reference for the speaker plane. I then mark the point directly below where my head is, which is extremely close to the plane of the 'back' wall.

- I've tried several recommendations for speaker placement along the marked speaker plane: quarter room width points, focal points of an ellipse which tangentially contacts all walls, and the 72 degree listening angle. I calculate the distance of the tweeter from the middle of the speaker plane using standard trigonometric formulae or by dividing the width of the room by 4, mark the tweeter position on the speaker plane with the aid of that measurement, and then set the stands up so the speaker is immediately above the marked point and make any minor adjustments by adjusting the stands and also the speaker's position on the stand. Things would certainly be a bit easier with floorstanders where one only has to play with the speaker position, not stand position and speaker on stand position.

Provided the listening chair doesn't get bumped and moved slightly, or my head move slightly,I'd think my locations were accurate to within a mm or two and my head will move more than that during the course of a listening session.

Does it make a difference? I can't speak for those with rectangular rooms but with that kind of precision and acoustic treatment at the first reflection points to absorb the first reflections which are slightly different in strength from left to right due to the asymmetrical shape of the room, my centre image is centred extremely well. Without the acoustic treatment and with the resulting left/right imbalance to the soundfield, the centre image drifts quite a bit to the left. Precision certainly makes a difference in my room and I think it would make a difference in any room. The normal small head movements that occur during listening aren't a problem provided the basic precision is there. A few inches difference in the setup is a much bigger shift than normal head movement and that's certainly more than enough to move my centre image to one side. Symmetrical rooms are probably a little more forgiving than my room.




David Aiken

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