Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - Page 4 - diyAudio
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Old 2nd August 2012, 02:48 PM   #31
tb46 is offline tb46  United States
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Hi NWCgrad,

I hope bjorno will find the time to dig into the port design, it looks like a sophisticated piece of engineering. It will be interesting to see what he comes up with :-).

Regards,
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Old 19th August 2012, 06:15 AM   #32
NWCgrad is offline NWCgrad  United States
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Quote:
Originally Posted by tb46 View Post
Hi NWCgrad,

I hope bjorno will find the time to dig into the port design, it looks like a sophisticated piece of engineering. It will be interesting to see what he comes up with :-).

Regards,
Bjorno seems to be on vacation from the board. Looks like this may be the final design.

Do you see any improvements that should be made?

Does raising the driver cause any issues?

Can I mix the two hieght designs (2 of each design)?

Again, I offer my profound thanks to you and bjorno for all the assistance you provided. Your help was above and beyond anything I expected or deserved!!!!

Last edited by NWCgrad; 19th August 2012 at 06:18 AM. Reason: spelling
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Old 19th August 2012, 03:27 PM   #33
tb46 is offline tb46  United States
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Hi NWCgrad,

Post #32: "...Do you see any improvements that should be made?

Does raising the driver cause any issues?

Can I mix the two hieght designs (2 of each design)?..."

Besides the port issue, I think this one is ready to build.

Raising the driver should not matter much in the below 100Hz range. Jus make sure that you maintain the internal length and areas.

Mixing should be fine.

Hope we'll hear from bjorno on the port details (the one in the past drawings should work though).

Regards,
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Old 20th August 2012, 12:52 AM   #34
NWCgrad is offline NWCgrad  United States
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Thanks again for the assistance. I currently own two of the LAB-12 drivers, see attachments. I have them in two 16" x 16" x 16" "sealed" enclosure, the sealed is in quotes because the boxes were made for $25 in Phnom Penh and are not even close to airtight. I keep filling cracks with wood filler, but the boxes keep cracking.

While the wood is very interesting to look at, they do not properly cure the material. Thus, over time the boxes crack (this is why I will not be buying any wood products here to bring back to the US next summer). It is to expensive to ship plywood over here for a better build.

Best,
Steve
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Old 21st August 2012, 02:22 PM   #35
tb46 is offline tb46  United States
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Hi NWCgrad,

That looks like an interesting wood grain. How about another layer on top of the existing layers to seal and strengthen it? Did you use any internal bracing?

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Old 21st August 2012, 03:10 PM   #36
NWCgrad is offline NWCgrad  United States
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Oliver, I don't have any woodworking tools while stationed overseas. As soon as I get back home to the states I will start building two of the enclosures from this thread.

The wood over here is very interesting, to bad they do not let it properly cure before it is used . I will bring back the boxes to chop up for some project, probably not audio related. The boxes are not braced, but they are stuffed with polyfill.

The 4 Pi main speakers (JBL 2226 and B&C DE250 drivers) are very well braced, and have an internal oak scaffolding to support the MDF during military moves. Size was adjusted to account for extra materials, they are ridiculously heavy but sound great. I have oak veneer for them but did not have time to complete before the move to Cambodia.

Last edited by NWCgrad; 21st August 2012 at 03:14 PM.
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Old 31st August 2012, 01:38 AM   #37
NWCgrad is offline NWCgrad  United States
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Originally Posted by bjorno View Post
Hi,

Here is the first of MJK simulations from which i decided to try improving the port system...more to come (i.e. Olivers .pdf:s)..but it may take days...or a week until I have time to post more.

b
Bjorno, first off I greatly appreciate all of your assistance!!!! I modifed Oliver's PDF but did not change any of the internal volumes. Have you had the time to look into improving the port system? I completely understand you are very busy and am not trying to be a pain. I will be building this design next summer regardless, because as it stands now it is far better than what I could design. You - and Oliver - are great assets to the community.
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Old 31st August 2012, 02:37 AM   #38
NWCgrad is offline NWCgrad  United States
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oliver,

I looked at my modification today to calculate a cut sheet. I did not record the dimensions, I am going to scrap my changes and go with your revision B (the one you recommended). I assume I can lay these on their side, 4 across the front stage would minimize interference with the wall mounted projection screen (the bottom of the screen would be blocked by the taller of the two versions). Is my assumption correct?

Thanks, Steve
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Old 31st August 2012, 03:13 AM   #39
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Originally Posted by NWCgrad View Post
The wood over here is very interesting, to bad they do not let it properly cure before it is used
Perhaps one layer of fiberglass and woven mat on each internal panel might be enough to seal up the box for good, and the slight reduction in volume should make very little audible difference. If you do this, make sure to lay a strip across each edge, for additional security against splitting at the edges.
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Old 7th September 2012, 05:11 AM   #40
NWCgrad is offline NWCgrad  United States
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Originally Posted by Brian Steele View Post
Perhaps one layer of fiberglass and woven mat on each internal panel might be enough to seal up the box for good, and the slight reduction in volume should make very little audible difference. If you do this, make sure to lay a strip across each edge, for additional security against splitting at the edges.
That would definately seal the cabinets, but the box size is not optimal fro the driver. Will bring the boxes back to the US and use them for something else, not sure what at theis point.
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