Wayne Parham Messages: 18831 Registered: January 2001
Illuminati (33rd Degree)
Rounding the corners is always OK.
All LAB12 and Pi-12 woofers are advertised as 6Ω devices. When horn loaded, some people say they're 8Ω each. But either way, a single-figure impedance value isn't accurate, and is just an approximation, if even that.
The impedance in free air is between 4-6Ω from 60Hz to 200Hz or so. Below that range and it rises dramatically because of resonance, up to around 100Ω, but then falls again below resonance. At the lowest frequencies it approaches its DC resistance of 4.3Ω Above 200Hz impedance steadily rises, doubling approximately every 1.5 octaves or so.
BobTahoe Messages: 32 Registered: July 2015 Location: Lake Tahoe , NV
Baron
Made some progress today, My first baffle on the left is fairly messed up and will need to be re done, but the other one is pretty spot on according to the plans.
One questions, if I wanted to flush mount the waveguide, how deep and how much wider, from what I can tell it's something like 1/4" wider by 1/4" deep?
johnnycamp5 Messages: 356 Registered: June 2015 Location: NJ
Grand Master
I'm looking to do the same thing in preparation of my waveguides.
I have found that the supposed depth of the waveguide flange is said to be 1/4".
I have also found that the supposed dimensions for the outer flare of the face of the waveguide is said to be 11-5/8" wide x 6-9/16" tall.
Whats wrong with the baffle on the left?
It looks good in the pics .
BobTahoe Messages: 32 Registered: July 2015 Location: Lake Tahoe , NV
Baron
The baffle on the left, has a few issues, it was the first time cutting with a router. I accidently cut the wave guide cut out to 11" not 10.5" and the cut out for the woofer isn't center its off by a 1/2" to the left.
BobTahoe Messages: 32 Registered: July 2015 Location: Lake Tahoe , NV
Baron
Getting close to closing up the cabinets for the 4pis, and started on one of the 3pi subs.
Here's one with bracing just waiting for the baffle and port:
Here's a pic of everything - Off to the left is the top and bottom for a 3Pi sub, then the 3 4pi's. Should have these all glued up this week.
I've decided not to flush mount either the JBL woofer or the wave guide. From what I've it's only for cosmetic reasons.
Going to have to think about how I'm going to finish these soon. Needs to be something other than black, and can't be too shiny since they'll be in front of my projector....but not behind the screen. Also all of this is in the Great room of the house so it will all be visible.
johnnycamp5 Messages: 356 Registered: June 2015 Location: NJ
Grand Master
Coming along nicely.
I installed cherry veneer on mine, since they will be visible, and it was one of the easier things I've done (especially compared to a painted, fine finish).
I had never done it before, so I was nervous.
When I read some of the "how to's" on line, many of them seem to make a mountain out of a mole hill.
Mounting your drivers flush might be a good idea, with helping get back some of the internal air volume you used in all your extra/inside corner bracing.
Also, if you plan to build cloth covers, you will not see the front baffle anyway.
johnnycamp5 Messages: 356 Registered: June 2015 Location: NJ
Grand Master
About your finish being too shiny-
I had the same concerns.
For me, after applying several coats of clear lacquer (gloss), I used "0000" steel wool, and then "Johnsons paste wax".
What a nice "satin" finish it turned out to be. Not too shiny at all.
Don't worry about applying the "gloss" lacquer, it contains no clouding agents (for creating a satin or semi gloss) and mats down just right after the "0000" sell wool.
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