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Mandolin box/baffle (re)design
Mandolin box/baffle (re)design
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Old 3rd June 2020, 12:03 PM   #1
its bh is offline its bh
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Default Mandolin box/baffle (re)design

Hi all

After spending way too long looking at speaker designs, reading posts and looking at builds, I'm soon to start building a pair of Jeff Bagby Mandolin's. In the process of reviewing the builds, I came across a handful of low diffraction cabinet designs which I think are much better looking than a big box - namely the SB Ara.

I'm not looking at producing a slanted baffled, as I don't wish to look at the remodelling the XO to account for time delay etc. Afterall, part of the reason I went with a proprietary and proven design was to avoid XO design, however the side/top angles on the baffle I think look great in the Ara. If anyone has modified the front baffle of the Mandolin design in a similar way to the Aras, it'd be great to hear your comments.

I've read Zaphs comments on the importance of reproducing his designs exactly, given his XO's are designed and account for the exact driver placement and baffle. Given this, would it be unwise to modify the Mandolin baffle in such a way as I've suggested?

Thanks very much in advance
Cheers
Brenton

Link to SB Ara - ARA – Sbacoustics
Link to Mandolin Box design on Meniscus website - https://meniscusaudio.com/wp-content...-2-Cabinet.pdf
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Old 4th June 2020, 03:42 PM   #2
LineSource is offline LineSource  United States
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Top Tweeter Bevels for Narrow Cabinets

"Mandolin Cabinet material: Front Baffle is 1", the rest 3/4" MDF"

You will probably get the most crossover-accurate sound, plus good reduction of edge diffraction distortion by increasing the front baffle thickness to 1.5" - 2" and cutting an "Avalon Style" Truncated Pyramid to the top section around the tweeter. You will need to route out the THICK baffle behind the midbass to support easy air flow.


Good Example = Spirit Wind by Jeff Bagby
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File Type: jpg Top Bevels.jpg (90.3 KB, 153 views)
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Old 5th June 2020, 10:24 AM   #3
its bh is offline its bh
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Quote:
Originally Posted by LineSource View Post
Top Tweeter Bevels for Narrow Cabinets

"Mandolin Cabinet material: Front Baffle is 1", the rest 3/4" MDF"

You will probably get the most crossover-accurate sound, plus good reduction of edge diffraction distortion by increasing the front baffle thickness to 1.5" - 2" and cutting an "Avalon Style" Truncated Pyramid to the top section around the tweeter. You will need to route out the THICK baffle behind the midbass to support easy air flow.


Good Example = Spirit Wind by Jeff Bagby
Thanks LineSource. Greatly appreciated.

Given the low clearance of the tweeter to the top of the baffle, to achieve the desired angle, I assume I'd need to move the drivers down. So long as I keep the internal volume and the distance separating the drivers consistent with the original design, I should be ok. That sound right?

Thanks again
Cheers
Brenton
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Old 5th June 2020, 03:04 PM   #4
DickHertz is offline DickHertz  United States
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If you start moving drivers around on the baffle you'll cause issues with the crossover. They might be audible, they might not. Jeff Bagby wrote a baffle diffraction simulator the would help you model the effects of driver location and edge diffraction.

Loudspeaker Design Software
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Old 5th June 2020, 05:50 PM   #5
classicalfan is offline classicalfan  United States
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I guess that you just have to decide whether you want the speaker to be better looking or better sounding. It would be an easy decision for me to make, but it's your speaker.
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Old 5th June 2020, 06:56 PM   #6
giralfino is offline giralfino  Italy
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Quote:
Given the low clearance of the tweeter to the top of the baffle, to achieve the desired angle, I assume I'd need to move the drivers down. So long as I keep the internal volume and the distance separating the drivers consistent with the original design, I should be ok. That sound right?
In a word, no. You want to keep the original width and height and also the driver distances from the top. Chamfering or rounding over the edges doesn't do harm, and can provide a slightly better diffraction control without changing the way the crossover was designed. If you move the drivers on the baffle, or change baffle dimensions, you need to simulate the effect and decide if it good or bad.

Ralf
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Old 6th June 2020, 12:02 AM   #7
LineSource is offline LineSource  United States
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Attached. Simulations of small box with sharp edges vs. beveled edges illustrating edge diffraction distortion.

The measured in-room SPL will be smoother with the beveled baffle than with the original high-diffraction square edges. To cut the top downward bevel to mimic the Spirit Wind front baffle you will need to mount both the tweeter and midbass about 0.75" lower than the original baffle... a small change.
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File Type: jpg SharpEdges.jpg (136.9 KB, 82 views)
File Type: jpg Bevels.JPG (228.5 KB, 78 views)
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Old 6th June 2020, 12:17 AM   #8
LineSource is offline LineSource  United States
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"Round ... Round ... Get-a-Round.... I Get a-Round" if you trust the Beach Boys and lust for speakers with Sexy Curves .... you may want to ask Santa for a 1.5" quarter round router bit, or go to a cabinet shop with a 3" quarter round shaper.

Europe DIY-speakers are starting to use Big Rounds(attached)...
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File Type: jpg EuropeRounds.jpg (74.6 KB, 77 views)
File Type: jpg USA Rounds.jpg (154.3 KB, 76 views)
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Old 6th June 2020, 10:53 PM   #9
its bh is offline its bh
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Thanks very much all. LineSource, as always, your willingness to provide sims is greatly appreciated.

Ultimately, this thread was to investigate whether it was possible to modify the baffle shape and design with the view of improving diffraction and sound quality, not to look at improving aesthetics while ignoring it’s potential detriment sound. Given my novice experience, I will likely run with the original box design and roundover the edges.

Depending on wood and time, I may play with the box sim and construct a second box with an angled baffle and listen to the changes.
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Old 6th June 2020, 11:21 PM   #10
classicalfan is offline classicalfan  United States
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It seems from your original post that aesthetics was the only reason for modifying the design. Here is what you wrote:

'I'm not looking at producing a slanted baffled, as I don't wish to look at the remodelling the XO to account for time delay etc. Afterall, part of the reason I went with a proprietary and proven design was to avoid XO design, however the side/top angles on the baffle I think look great in the Ara. If anyone has modified the front baffle of the Mandolin design in a similar way to the Aras, it'd be great to hear your comments."

Not much said about improving diffraction and sound quality in that statement, which is the reason I submitted my post suggesting that you should simply make a decision between the two directions - sound quality or aesthetics.

Last edited by classicalfan; 6th June 2020 at 11:26 PM.
 

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