Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - Page 3 - diyAudio
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Old 17th July 2012, 03:03 AM   #21
tb46 is offline tb46  United States
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Hi NWCgrad,

I like bjorno's idea too, but it is not what I was suggesting. When I tried to simulate an enclarged opening in Hornresp it ended up giving too much low end boost, and increased the ripple @ 86Hz. Anyway, here are two similar ways of folding the same model; I like Rev.B better, as I'm always a little uncertain about what a short labyrinth (as in Rev.C) will do at very low frequencies. When modelling these I stayed with a constant S5 in the model. I'm looking forward to see what bjorno comes up with.

Regards,

P.S.: These are really just quick sketches.
Attached Files
File Type: pdf LAB12_OD_ML_TL_RevB_RevC_by_bjorno.pdf (40.3 KB, 295 views)
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Old 17th July 2012, 04:49 AM   #22
NWCgrad is offline NWCgrad  United States
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Thanks for the sketches! I really like the way this project is evolving.

I believe when this design in finalized it will be really great. These drivers are fairly inexpensive in the US, and are widely used in the horns so I assume they are very duarable.

I already have two in crappy 16" sealed boxes, actually they are propbably not sealed, they were made in Cambodia for $25 and they have developed multiple cracks I keep filling with wood filler - the boxes will not be making the return trip to the US. Based on the the modeling I may only need two, but I will build four for "head room."
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Old 18th July 2012, 09:58 AM   #23
bjorno is offline bjorno  Sweden
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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
Attached Images
File Type: jpg LAB12_stuffed-un-stuffed_OD-ML-TL.JPG (633.9 KB, 850 views)
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Old 18th July 2012, 03:55 PM   #24
NWCgrad is offline NWCgrad  United States
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Quote:
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

Thanks bjorno! Between you and Olivier I think the LAB-12 build will be pretty nice. I am mostly interested in SQ, but the ability to play at high SPL is nice for the times when you just need it loud.
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Old 21st July 2012, 07:54 AM   #25
NWCgrad is offline NWCgrad  United States
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I ran both this design and the Mal-X T-TQWT design in Hornresp (attached). The Mal-X will have a LPF set at 50 or 60 Hz (maybe a HPF at around 10 Hz), the LAB-12's will have a LPF at 80 or 120 Hz, 120 Hz is recommended by the designer of my main speakers for the the two flanking subs and a HPF at 20 Hz for cone excursion.

Overall, the system models +/- 3 dB from 12 Hz to over 150 Hz, of course real world performance will vary. I do have a miniDSP with 4 channels of parametric eq available if required (the Mal-X may be powered by a Crest Audio Pro-Lite 2.0 DSP [4 Ohm Bridged - 2000 W]).
Attached Images
File Type: jpg MAL-X and LAB-12.jpg (192.1 KB, 741 views)
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Old 24th July 2012, 12:57 AM   #26
NWCgrad is offline NWCgrad  United States
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Quote:
Originally Posted by tb46 View Post
Hi NWCgrad,

I like bjorno's idea too, but it is not what I was suggesting. When I tried to simulate an enclarged opening in Hornresp it ended up giving too much low end boost, and increased the ripple @ 86Hz. Anyway, here are two similar ways of folding the same model; I like Rev.B better, as I'm always a little uncertain about what a short labyrinth (as in Rev.C) will do at very low frequencies. When modelling these I stayed with a constant S5 in the model. I'm looking forward to see what bjorno comes up with.

Regards,

P.S.: These are really just quick sketches.
Bjorno and Oliver,

I modified the diagrams provided by Oliver to raise the driver up from the port system. The attached diagram shows the change. The S12 and S23 distances did not change due to internal adjustments to the enclosure.

Will raising the driver cause any negative impact on sound quality or frequency extension? I would not think so as none of the modeled parameters have changed, but I want to be sure.

Thanks again for your kind assistance.

Steve
Attached Images
File Type: jpg Modified Enclosure based on Oliver's Design.JPG (91.8 KB, 672 views)
Attached Files
File Type: pdf Modified Layout - S12 and S23 held constant.pdf (51.2 KB, 87 views)

Last edited by NWCgrad; 24th July 2012 at 12:59 AM. Reason: Added JPEG of modified layout
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Old 30th July 2012, 07:44 AM   #27
NWCgrad is offline NWCgrad  United States
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I made a 1:10 scale drawing of the design, withe both the original and modified driver placement. I believe I like the original placement better visually.

Any thoughts on whether raising the driver would cause problems?
Attached Images
File Type: jpg LAB-12 and Mal-X - 1_10 scale.jpg (91.4 KB, 642 views)
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Old 30th July 2012, 08:08 AM   #28
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Visually, I like the raised position. As long as the woofer is in the same position as the modeled line, then performance shouldn't change.
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Old 30th July 2012, 10:33 AM   #29
NWCgrad is offline NWCgrad  United States
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Originally Posted by BP1Fanatic View Post
Visually, I like the raised position. As long as the woofer is in the same position as the modeled line, then performance shouldn't change.
The internal particians were modified so the length and volume are unchanged. I keep waffling on which I prefer. No matter which way I end up going, I think they will sound very good. The four should match the Mal-X output.
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Old 2nd August 2012, 12:42 AM   #30
NWCgrad is offline NWCgrad  United States
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Quote:
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,

Thank you for all of your valuable assistance and efforts on this design. Do you see any issues with latest design parameters? I may actually build two enclosures with the mid-mounted drivers and two with the lower mounted drivers to provide variations in response to smooth the overall system response.

Once I see you concurrence, and info on stuffing, I will be set. When I return to the States I will start a build thread on the Bjorno/Oliver Sub System.

I would like to offer again my profound thanks to both of you! What an asset to the DIY community.
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