Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - Page 2 - diyAudio
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Old 15th July 2012, 05:16 PM   #11
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by NWCgrad View Post
Bjorno, I am not sure what the information actually means. From the schematic diagram it appears the enclosure consists of 4 segments:

Segment 1: 50.479 liters
Driver Diaphram/Throat Chamber: 0.913 L
Segment 2: 55.712 L
Segment 4: 10.799 L

How do I calculate the enclosure from this infomation. From the schematic for the MAL-X I could somewhat see where the shape comes from, but with this design I am completely lost.

I was able to download hornresp on my new laptop, entered your values and played around for awhile - but I am way over my head.
Its nice to know the volumes but pretty useless when calculating the practical CSA:s:
Start with S1(the closed end) and divide with 31.4 cm= driver frame width + a very small baffle clearance, i.e. 513/31.4= ~16.34 cm
As long as the CSA is 513cm^2 the depth width would be ~16.34 cm...

Then divide S3=S4 with 31.4===> depth width =~5.38 cm
Now fold the enclosure while preserving the sum of L12+L23+L34+L45...

Its DIY Your Job! and is best done with a paper and pen + hours(weeks for some DIY:rs ) ,if it takes.

b
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Old 15th July 2012, 07:31 PM   #12
tb46 is offline tb46  United States
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Hi Y'all,

Sitting here w/ minor chemical burns on three fingers (stupid, stupid, stupid), and can't really do anything usefull, so here is rough try at it:

Regards,
Attached Files
File Type: pdf LAB12_OD_ML_TL_by_bjorno.pdf (20.0 KB, 532 views)
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Old 15th July 2012, 08:18 PM   #13
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by tb46 View Post
Hi Y'all,

Sitting here w/ minor chemical burns on three fingers (stupid, stupid, stupid), and can't really do anything usefull, so here is rough try at it:

Regards,

Hi Oliver,

Thats a very nice folding tb46 is an and when it comes to fold quarter-wave boxes!

b

Ps: I will try another day to run this box in MJK to find out the optimal stuffing...and post to this thread,of course.

Last edited by bjorno; 15th July 2012 at 08:21 PM.
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Old 15th July 2012, 09:04 PM   #14
tb46 is offline tb46  United States
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Hi bjorno,

Yes, the stuffing will be the key.

Regards,
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Old 16th July 2012, 07:42 AM   #15
NWCgrad is offline NWCgrad  United States
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Quote:
Originally Posted by tb46 View Post
Hi Y'all,

Sitting here w/ minor chemical burns on three fingers (stupid, stupid, stupid), and can't really do anything usefull, so here is rough try at it:

Regards,
I feel your pain on the chemical burns...in organic chemistry class I set my hand in a puddle of concentrated phenol - the skin was sagging 3" on the side of my hand when I first felt the burn (still have the scar today, 20+ years later).

Thank you for the folding of the design, now that I see it I can make sence of the data presented by Bjorno. Very nice compact enclosure, looks relatively simple to build.

To my untrained eye, it looks a lot like a slot-ported enclosure, how does the performace differ (I am sure that it does)? If you raise the driver does it change performance (not that I want to, I am just curious)?

I like the looks of this build!!!

Last edited by NWCgrad; 16th July 2012 at 07:53 AM.
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Old 16th July 2012, 07:46 AM   #16
NWCgrad is offline NWCgrad  United States
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Quote:
Originally Posted by bjorno View Post

I will try another day to run this box in MJK to find out the optimal stuffing...and post to this thread,of course.
Thanks Bjorno, does the stuffing go in S1 between the driver and S5?
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Old 16th July 2012, 03:35 PM   #17
tb46 is offline tb46  United States
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Hi NWCgrad,

Post #15: "... it looks a lot like a slot-ported enclosure, how does the performace differ (I am sure that it does)? If you raise the driver does it change performance..."

I think the slot is high enough @ 2.119" to give you a very similar performance to the model; but, with any folded port with a wide aspect ratio it might take a little experimenting. One way to change this would be to run a center divider (e.g.: a 2x4) down the middle of the slot/duct and raise the duct height to make up for the lost cross-sectional area.

If you raise the driver you shorten L12 and lengthen L23, this will change the performance from the model. You could raise the driver, reroute the L12 path (straight up to the top of the enclosure, then back, then down) and the L23 path (lower the horizontal divider, and shorten the vertical divider to make up for the length gained by raising the driver), and arrive at the model dimensions; the "room for amp" would now be in the middle of the back of the enclosure (I think) :-).

This is thought as a starting point, you can add corner reflectors, braces, cleats, widen the box, add midrange and tweeter in the front.....

Regards,
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Last edited by tb46; 16th July 2012 at 03:38 PM.
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Old 16th July 2012, 04:20 PM   #18
NWCgrad is offline NWCgrad  United States
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Oliver,

I believe I will leave it alone, it is almost identical in height to my mains. It would look good to cluster all four units across the front wall, when combined with my MAL-X T-TQWP I should have the low end covered

Thanks again for your assistance.

Steve
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Old 16th July 2012, 04:32 PM   #19
bjorno is offline bjorno  Sweden
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Hi,

A quick drawn picture made from Olivers .pdf solving a couple of possible upcoming problems... but not yet revealed in a simulation, I still work on this...


b
Attached Images
File Type: gif SPL-version.GIF (11.2 KB, 1075 views)
File Type: gif Slot_slot-port.GIF (18.0 KB, 917 views)

Last edited by bjorno; 16th July 2012 at 04:36 PM.
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Old 17th July 2012, 12:38 AM   #20
NWCgrad is offline NWCgrad  United States
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Bjorno,

I like the larger opening, it looks like what Oliver was suggesting. I assume this change would not negatively impact the sound, just increase the abiility to play at high SPL.

Looks really good! Thanks again.

Steve
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