The Triton MTM Grows Legs--A MLTL Design - Page 2 - diyAudio
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Old 22nd December 2012, 12:28 AM   #11
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Jeff, Paul, and Planet10:

Thanks for your comments Jeff and let me say that your original design gave me and other builders a good starting foundation. The Tritons really have an out of box sound that I associate with well designed and great imaging speakers.

Paul, you are likely correct that my 2006 worksheet doesn't have the functionality of later ones. I have more recent licenses with Martin so I'll check my status on that aspect. I'm thinking I need to migrate to one of my Win 7 PCs anyway so this is an opportunity for me to go to a faster, better computer for future work.

Yes, Dave the stuffing is only in the upper third of the box. I've had success with previous MLTLs with this damping scheme so that is my starting point. Do you have experience that would mandate additional damping below the drivers? If necessitated, additional damping would easy enough to add.

By bridge brace I mean two short dowels (attached on the back of the front baffle) that extend from each side to the edge of the tweeter cutout. A longer (the same width as the baffle) dowel would be glued on top of these two shorter pieces and extend over and clear the rear of the tweeter. Thus the baffle would be strengthen and have better support between the two woofers. In the bookshelf Triton MTM build threads others have essentially used dowels between the rear panel and the front panel in this same area. Now my cabinet as constructed is very solid but I'm sure that bracing improvements can always be achieved. The tradeoff is whether more extensive bracing is necessary given the cross-sectional area of this box. I'm open to any suggestions that you may have.

Jim
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Old 22nd December 2012, 05:42 AM   #12
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Quote:
Originally Posted by Jim Griffin View Post

... the stuffing is only in the upper third of the box

... bridge brace
Thanx.

Drawing attached.

dave
Attached Files
File Type: pdf Triton-MTM-MLTL.pdf (66.7 KB, 696 views)
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Old 22nd December 2012, 09:41 AM   #13
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Dave,

Exceptional drawing! Much better than my Visio doodling. Thanks for the work.

Jim
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Old 22nd December 2012, 01:30 PM   #14
pkitt is offline pkitt  United States
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It's probably just apples to apples as for as performance is concerned, but I've found usually really good success stuffing the first (top) half of an ML-TL but at a lower density of 0.75 lb/ft3, which probably nets out to the same total amount of stuffing by weight compared to what you did (do). Now there's a secondary reason I like to use a density of 0.75 lb/ft3. Meniscus Audio sells this stuffing in batting form: Bonded Dacron. It is 1" thick and has an inherent density of 0.75 lb/ft3 (a 12" x 12" piece, which is 144 in3 in volume, weighs 1 ounce), which means no matter what shape you cut it into, it will have that density. So, you can cut it into rectangles that match the internal width and depth of the cabinet and stack up however many layers (inches) you need without having to weigh it or fluff it up.
Paul

Quote:
Originally Posted by Jim Griffin View Post
Jeff, Paul, and Planet10:

Thanks for your comments Jeff and let me say that your original design gave me and other builders a good starting foundation. The Tritons really have an out of box sound that I associate with well designed and great imaging speakers.

Paul, you are likely correct that my 2006 worksheet doesn't have the functionality of later ones. I have more recent licenses with Martin so I'll check my status on that aspect. I'm thinking I need to migrate to one of my Win 7 PCs anyway so this is an opportunity for me to go to a faster, better computer for future work.

Yes, Dave the stuffing is only in the upper third of the box. I've had success with previous MLTLs with this damping scheme so that is my starting point. Do you have experience that would mandate additional damping below the drivers? If necessitated, additional damping would easy enough to add.

By bridge brace I mean two short dowels (attached on the back of the front baffle) that extend from each side to the edge of the tweeter cutout. A longer (the same width as the baffle) dowel would be glued on top of these two shorter pieces and extend over and clear the rear of the tweeter. Thus the baffle would be strengthen and have better support between the two woofers. In the bookshelf Triton MTM build threads others have essentially used dowels between the rear panel and the front panel in this same area. Now my cabinet as constructed is very solid but I'm sure that bracing improvements can always be achieved. The tradeoff is whether more extensive bracing is necessary given the cross-sectional area of this box. I'm open to any suggestions that you may have.

Jim
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Old 22nd December 2012, 01:48 PM   #15
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Paul,

I looked at the frequency response for various stuffing densities from 0.25 to 1.0 lb/ft3. Not a lot of difference--perhaps a 1 dB flatter response--between 0.75 and 1.0 lb/ft3 levels. The 0.75 lb/ft3batting pieces would be handy to place into a cabinet. While teasing Acousta Stuf doesn't consume that much time, the exactness of the packing density can vary between users.

Jim

Last edited by Jim Griffin; 22nd December 2012 at 01:49 PM. Reason: correction
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Old 22nd December 2012, 02:39 PM   #16
pkitt is offline pkitt  United States
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I agree. It's so extremely convenient to use the Dacron batting from Meniscus because of being able to cut it into convenient shapes for easy installation, not having to weigh it and achieving a much more consistent density.
Paul

Quote:
Originally Posted by Jim Griffin View Post
Paul,

I looked at the frequency response for various stuffing densities from 0.25 to 1.0 lb/ft3. Not a lot of difference--perhaps a 1 dB flatter response--between 0.75 and 1.0 lb/ft3 levels. The 0.75 lb/ft3batting pieces would be handy to place into a cabinet. While teasing Acousta Stuf doesn't consume that much time, the exactness of the packing density can vary between users.

Jim
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Old 22nd December 2012, 05:06 PM   #17
DDF is offline DDF  Canada
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Jim

The Bdc signature of the original Triton won't be preserved with baffle extending to the ground but you may not find it problematic in listening

May even be a good balance against the standard floor reflection upper bass suckout
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Old 22nd December 2012, 08:07 PM   #18
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Yes, I'm aware that extending the baffle to the ground but I've not found it to be a significant issue in previous efforts of converting bookshelf speakers to small floor standers. In the limit the bookshelf design is a good first order step toward a successful floor standing speaker design if you maintain the baffle width.

Usually, there are other room effects and such which muddy the acoustical response. In fact the response curve for this MLTL has a slight download slope (a dB or so) toward the lower frequency end of the band which will likely be beneficial to balance against additional room gain and baffle extension.
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Old 22nd December 2012, 09:32 PM   #19
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Default System Responses

I have attached a few key plots from the Martin King worksheets for this design. I'm working to get a rescaled impedance curve.

As with all Martin King worksheet plots the red curve is the system response curve while the blue plot is the infinite baffle equivalent.
Attached Files
File Type: pdf TritonMLTLSystemResponses.pdf (125.7 KB, 241 views)

Last edited by Jim Griffin; 22nd December 2012 at 10:00 PM. Reason: addition
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Old 22nd December 2012, 09:57 PM   #20
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Attached are some plots of the frequency response curves when the port tube length is changed to 4.5", 6.0", 7.5", to 9" lengths from the top plot to the bottom. To me the 6.0" seems to be the optimum solution as the performance is adequate with a relative flat frequency response curve. Both the 7.5" and 9" lengths would require curving or folding inside the box or extending outside the box. For these respective lengths the F3 points 40Hz, 37 Hz, 35 Hz, and 33Hz as the tube is extended.

As with all Martin King plots, the red curve is the system response curve while the blue plot is the infinite baffle equivalent.
Attached Files
File Type: pdf TritonMLTLPortTubeLengthStudy.pdf (139.5 KB, 211 views)
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