I say "throat", you say "mouth". Mouth is probably the better word.Grant Bunter wrote: Hey Nordo,
I hope we are referring to the same thing, the mouth braces, but I guess it applies to all braces.
Ok, horns pretty much eliminate harmonics, so that's not an issue, and the same can be said about nodes.
Panel vibration however is a problem.
It may not be able to be felt by hand, but if it's there, it robs you of output, around 3dB IIRC.
It should say in your plans that nominal bracing width is 6 to 9".
So for the mouth braces, with a 27" wide panel that should mean exactly 9" from each panel edge should be a line, being the centre for that brace, and the measurement from brace to brace centre to centre would also be exactly 9". Sorry about the imperial measurements, but 9 x 3 = 27 lol, so it's a great example.
9" is 228.6mm, so your bracing space of 318mm is in the order of 75mm to wide. I hope it's not going to display itself as a problem for you.
It makes sense to, and says to in the plans, offset braces where they double up, eg panel 2/5, 5/8.
When I built mine (for other than the mouth braces), I simply drew the line, then offset the brace by the thickness of the material so I could get a screw into either side...
When I was talking about nodes and harmonics, I meant in the panels when they are vibrating.
Panel 6 is well braced (from each side), so probably panel 10 could be my only problem.
If it is a problem, I could run a 75mm high stiffening rib in the middle of panel 10, from front to back (also being fixed to panel 11).
Is there any way of telling if panel movement is a problem?
Being 3dB down isn't a real indicator when I don't know what I'm comparing it against.
BTW, I do intend to test my T39s when completed, using a free program called REW (Room Eq Wizard) and a calibrated Dayton EMM6 mic.
The program is meant for room testing, but should be fine for testing the output of a T39.
Was going to have a look in the forum on the recommended setup for testing. I have fairly open areas near the house where I could get minimal reflections.