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Re: 4 Pi Build Progress [message #81482 is a reply to message #81481] Thu, 23 July 2015 15:39 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18272
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.

Re: 4 Pi Build Progress [message #81483 is a reply to message #81482] Thu, 23 July 2015 15:56 Go to previous messageGo to next message
BobTahoe is currently offline  BobTahoe
Messages: 32
Registered: July 2015
Location: Lake Tahoe , NV
Baron
Thanks for the info that's very helpful. This amps should handle that just fine, it's stable down to 2ohm, and will still push 525watts at 6ohms.

I can't wait to get this build done so I can start geeking out while getting everything dialed in.
Re: 4 Pi Build Progress [message #81484 is a reply to message #81483] Fri, 24 July 2015 11:49 Go to previous messageGo to next message
BobTahoe is currently offline  BobTahoe
Messages: 32
Registered: July 2015
Location: Lake Tahoe , NV
Baron
Gluing and clamping is a slow process, I'm hoping to have the sides and back on all the boxes this weekend, but we'll see.

Since I only have 6 clamps I can only do 1 box at a time here the fist one tops and sides:

index.php?t=getfile&id=1771&private=0

index.php?t=getfile&id=1772&private=0

This morning before work managed to get the back on it fits! It's far from perfect but nothing some bondo cant fix.

index.php?t=getfile&id=1773&private=0
Re: 4 Pi Build Progress [message #81485 is a reply to message #81484] Fri, 24 July 2015 12:39 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18272
Registered: January 2001
Illuminati (33rd Degree)

Moving right along!

Won't be too long now!

Re: 4 Pi Build Progress [message #81488 is a reply to message #81462] Sun, 26 July 2015 00:11 Go to previous messageGo to next message
BobTahoe is currently offline  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?

index.php?t=getfile&id=1774&private=0
Re: 4 Pi Build Progress [message #81489 is a reply to message #81488] Sun, 26 July 2015 08:32 Go to previous messageGo to next message
johnnycamp5 is currently offline  johnnycamp5
Messages: 326
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 Razz .

Regards!
Re: 4 Pi Build Progress [message #81490 is a reply to message #81489] Sun, 26 July 2015 09:43 Go to previous messageGo to next message
BobTahoe is currently offline  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.

Re: 4 Pi Build Progress [message #81491 is a reply to message #81462] Sun, 26 July 2015 20:25 Go to previous messageGo to next message
BobTahoe is currently offline  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:

index.php?t=getfile&id=1775&private=0




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.

index.php?t=getfile&id=1776&private=0




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.
Re: 4 Pi Build Progress [message #81492 is a reply to message #81491] Mon, 27 July 2015 07:11 Go to previous messageGo to next message
johnnycamp5 is currently offline  johnnycamp5
Messages: 326
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.
Re: 4 Pi Build Progress [message #81493 is a reply to message #81492] Mon, 27 July 2015 07:22 Go to previous messageGo to previous message
johnnycamp5 is currently offline  johnnycamp5
Messages: 326
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.

This was my experience.
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