Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - Page 34 - diyAudio
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Old 8th July 2014, 02:20 PM   #331
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Quote:
Originally Posted by xrk971 View Post
How do you display the 3d model and HR sim tilted on same screen like that?

Click the image to open in full size.
That does look cool!
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Old 8th July 2014, 03:17 PM   #332
tb46 is offline tb46  United States
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Hi TundraLTD,

Very cool drawing in Post #327. :-) Well done!

Regards,
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Old 9th July 2014, 12:14 AM   #333
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Quote:
Originally Posted by xrk971 View Post
Tundra,
Great looking 3d model there!
How do you display the 3d model and HR sim tilted on same screen like that?

Thanks! The model view is a 2d export from sketchup, the HR was a screen capture. I opened the model pic in photoshop and added the screen capture with the HR sim as a new layer, cropped it and then used the transform-skew tool to give it a 3d look
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Old 10th January 2015, 11:37 AM   #334
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Thank you everyone for a very nice design. Once again a lot of careful work has gone into this to yied a wonderful design.


I have a question. In post 308 (pg 31). thejessman shows a picture of his nice build. The build includes bracing between most internal parts. If bracing was used throughout, should the width of the cabinet be increased by the thickness of the bracing?


Thanksshows a picture of his nice build. The build includes bracing between most internal parts. If bracing was used throughout, should the width of the cabinet be increased by the thickness of the bracing?


Thanks
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Old 10th January 2015, 03:31 PM   #335
tb46 is offline tb46  United States
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Hi rocksteady40,

Post #334: "...In post 308 (pg 31). thejessman shows a picture of his nice build. The build includes bracing between most internal parts. If bracing was used throughout, should the width of the cabinet be increased by the thickness of the bracing?"

Short answer: Yes, but not necessary, especially if you use big cutouts in the braces.

I have simulated quite a few of these cabinets, and the thickness of one layer of bracing does not change the simulations very much. I recommend you fire up Hornresp, and give it a try (see the compilation of design elements by NWCgrad in Post #270/273). In this enclosure I squeezed the cross-sectional areas to what I consider the minimum necessary, so don't use 1.5" bracing. :-)

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Old 10th January 2015, 08:07 PM   #336
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"I recommend you fire up Hornresp, and give it a try..." Doh, I knew that. Thanks Oliver for your wise suggestion and help with with build.

Bob
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Old 24th June 2015, 10:53 AM   #337
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Dear audio mates,

I'm really attracted by this design!
OD-MT-TL let me imagine a transmission line with limitate dimensions, where I can put my Infinity Ref. 1260w.

The purpose is to make a sub for music listening.

I never used Hornresp but now I perceive its power. Having such an instrument for free is amazing, in the hope to obtain a good correlation with measured data. I enjoyed a lot in using it, in these days, especially the "Speaker wizard". But I'm a novice on that and I don't try to add stuffing nor implement electronic filters.

I attach a result I can suppose good. It does not reach an astonishing extension in low frequencies, but features limitate GD, low overall volume (77 liters), and a not too narrow (178 cm2) exit port.

Regarding the folding, I never do that, but bjorno suggestions let me think about it.
I imagine a folded enclosure (like post #273) with a inner depth of 35 cm (to include the speaker). We should have:

S1 = S2 = 580 cm2. So 580/33 (35 - 2cm bracing) = 17.5 cm for the first segment, long 65 cm, going from the back to the middle of the speaker.
S3 = 178 cm2. So 178/33 = 5.4 cm Hence the second segment starts from the middle of the speaker (width 17.5 cm) and extends for 67 cm to reach 5.4 cm.
The third (last) segment is a constant height (5.4 cm) with a leght of 76 cm.

This port, although not too narrow, may have a final flare to improve the result.



I hope some more experienced members can comment, correct, suggest some improvements.

Kind Regards

Fabrizio
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File Type: txt INF1260w.txt (949 Bytes, 14 views)
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Old 25th June 2015, 05:40 AM   #338
GM is offline GM  United States
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Greets!

Your sim is somewhat different than the OD-MT-TL and can be simplified to a simple one fold TQWT plus ideally should be tuned to Fs or a little lower, making it a little larger with output to 20 Hz where it will need a hi-pass to protect it for some music, movie LFE:

GM
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File Type: txt Inf1260W_TQWT.txt (950 Bytes, 15 views)
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Old 26th June 2015, 04:02 PM   #339
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GM, thank You very much for Your suggestions!

What do You mean with "Your sim is somewhat different than the OD-MT-TL" ?

I think Your simpler shape has a comparable construction complexity, isn't it?

I agree that this will require a good "rumble filter"

I also agree that the enclosure should enhance the emission at low frequencies, possibly lower than Fs. Mine do not.
Your simulation is immediately more efficient in that!

Anyway 106 litres of Volume brings some unwanted issues:

1) worst impulse response and group delay (Is there some method to fight that?)

2) quite big enclosure

Music listening, differently from film watching, possibly requires fast impulse response (a lot of audiophiles prefer a sealed enclosure, although with EQ correction).

My simulation features also a great defect in the "acoustical impedance" (peak over 500 ohm) while Yours is under 300. I don't well understand what does it means. Does the the speaker suffer more loading when acoustical impedence is high?

I attach an "intermediate volume" simulation where I limitate the volume to around 90 litres and where acustical impedance is now under control. There is deliberately a peak around 30Hz that should be smoothed with filling...

What do You think?

Regards,

Fab
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File Type: txt INF1260W_L.txt (948 Bytes, 3 views)
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