JP's Flashlight Method Revisited

[Victor]

The use of the flashlight technique for toe-in optimisation is well documented but has anyone ever used it to establish whether the rake angle is matched? (As viewed from the listening position)
Indeed, is the panel construction accurate enough to allow this?

I did a quick test on mine and although the rake angles look identical, the flashlight image is offset by 2" or so in the Z axis. Distance of the bass cabinet to listening position measured to within 1mm (but I'm always suspicious when things appear this good )

 

[tsv_1]

The use of the flashlight technique for toe-in optimisation is well documented but has anyone ever used it to establish whether the rake angle is matched? (As viewed from the listening position)
Indeed, is the panel construction accurate enough to allow this?

I did a quick test on mine and although the rake angles look identical, the flashlight image is offset by 2" or so in the Z axis. Distance of the bass cabinet to listening position measured to within 1mm (but I'm always suspicious when things appear this good )

Interesting situation. In my case, both the veritcal and horizontal axes matched-up fine (after some toe-in adjustment) - rake for both speakers was plumbed to 90 degrees relative to the floor.

 

[Victor]

Thanks TSV for your kind feedback.
Here's an old thread along similar lines, populated by some well known "old-timers" (Apart from Joey "the Kid" who is forever young.... ).

http://www.martinloganowners.com/fo...New-quot-Speaker-Alignment-method-to-consider

Having just read some example specs, Laser measuring devices don't look as useful as claimed. The small print says accurate to 2mm over any distance up 25-30m (usually).
I may be wrong but this also translates as "accurate to within 2mm at a distance of 1 or 2m" (!). Near field listeners beware???

My wife is out this evening so this presents an ideal opportunity to play around...

 

[tsv_1]

I just fired up my torch (as I think you folks like to call flashlights ) I'm shining it directly forward, perfectly parallel to the floor and about chest high as I'm sitting directly between the speakers, about 9 feet back. Now here's the trick, in order to completely eliminate any question of head movement or flashlight axis change when shinging on one speaker versus the other... I've selected a flashlight with reasonable beam width (i.e. not a laser)... so that with it shining directly forward, the beam actually reflects back from both speakers simultaneously. I'm not sure this gives me ideal feedback with regard's to being close to "one third in to the curvilinear panel", but it does give me an exact indication of relative rake angle between the two speakers. In my case, any difference is undetectable by eye.

I hope I'm explaining myself clearly here.

Cheers.