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Multi-Way Conventional loudspeakers with crossovers

Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
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Old 29th February 2016, 07:20 PM   #1
pcgab is offline pcgab  United States
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Location: San Marcos, Texas
Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Default Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build

I decided to build an open baffle speaker for my dad based on a pair of betsys and 4 alpha 15a's.

Inspiration came from:

https://zimmer64.wordpress.com/2015/...ha-15-a-mk-ii/

http://www.diyaudio.com/forums/wild-...etsy-ea15.html

They're made from baltic birch, 12mm and 18mm. Baffles are 12mm and 18mm, and the yet to be made 'supra-baffles' will be 18mm. I plan to slot load them as the build in the inspiration links did.

I made some progress this weekend, here are a few pics.

Baffles:

Click the image to open in full size.

Click the image to open in full size.

Gluing the first baffle together:

Click the image to open in full size.


Rear brace is 12mm in the middle, flanked by 2 18mm pieces on either side:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.


The baffles and rear braces will mount to a base made from 2 pieces of 18mm laminated together. That's the plan for now at least.

I'd like to build a passive xo, but for now I'll use a mini-dsp and a couple chip amps.
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Old 1st March 2016, 02:33 AM   #2
pcgab is offline pcgab  United States
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Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Cleaned up the first baffle and first rear brace a bit today. Marked mounting locations for the alpha's and did a little prelim fitting of the rear brace.

The rear brace isn't trimmed to mate to the baffle yet. I left a good bit of material there so I can true it up nicely one the baffle and base are ready for final fitment.

Click the image to open in full size.


Click the image to open in full size.


Hopefully I'll get some time tomorrow to glue up the second baffle, and start on the rear brace for that one as well.
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Old 1st March 2016, 02:42 AM   #3
guangui is offline guangui  Puerto Rico
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Coming along very nicely!
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Old 4th March 2016, 01:24 PM   #4
pcgab is offline pcgab  United States
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Join Date: Dec 2014
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Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
I got a bit more done yesterday evening, didn't have as much time as I would have liked, but progress is progress!!

Got the chamfers marked and cut for the Betsy driver on the first baffle:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

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Old 4th March 2016, 05:35 PM   #5
adason is offline adason  United States
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looks very good, I would even install a better driver...tb?
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Old 4th March 2016, 05:44 PM   #6
pcgab is offline pcgab  United States
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Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Quote:
Originally Posted by adason View Post
looks very good, I would even install a better driver...tb?
I considered that option, and tbh I may if I make a pair for myself. As I already had the Betsy's, I decided to use them for this project.

Hmm, that gets my mind thinking. I could make a temporary baffle for the betsy's cut-out and try some Fostex, or other <~8" full ranger..
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Old 7th March 2016, 01:55 AM   #7
pcgab is offline pcgab  United States
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Join Date: Dec 2014
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Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Made a bit of progress today:

Click the image to open in full size.


Got the supra-baffles cut, lightly sanded and prepped for glue-up:

Click the image to open in full size.

Click the image to open in full size.

and started glue-up:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

I'm hoping to get enough time over the next few days to get all the supra baffles glued. Once that's done I'll cut and laminate the base and move on to making the last rear brace. One step closer!
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Old 7th March 2016, 07:08 AM   #8
norman bates is offline norman bates  United States
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will this be active dsp ?

with that narrow of a baffle, you may be needing 12db of boost per octave below 500hz.

I can pull up jamo r909 and explain.

Or the Visaton no box.
that basically took a 15" and ran a 40hz low pass crossover on it to get it to go flat up to 300hz or so.

Don't get me wrong, I'd like to try something like this also someday.
And my wife would approve of an open baffle 19" wide x 50" tall (jamo R909).
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Old 7th March 2016, 02:43 PM   #9
pcgab is offline pcgab  United States
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Join Date: Dec 2014
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Wild Burro 'Betsy' and Eminence Alpha 15a - open baffle build
Quote:
Originally Posted by norman bates View Post
will this be active dsp ?

with that narrow of a baffle, you may be needing 12db of boost per octave below 500hz.

I can pull up jamo r909 and explain.

Or the Visaton no box.
that basically took a 15" and ran a 40hz low pass crossover on it to get it to go flat up to 300hz or so.

Don't get me wrong, I'd like to try something like this also someday.
And my wife would approve of an open baffle 19" wide x 50" tall (jamo R909).

I am planning on using DSP, MiniDSP 2x4 to be specific.

I'm sure I'll need some boost here and there. I really like the profile of the slim baffle.
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Old 7th March 2016, 04:28 PM   #10
guangui is offline guangui  Puerto Rico
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Default Sims

Not 100% accurate, but very close. Enclosed you will find simulations for both woofers, as if they were fully open, and as if slotted. I did some basic math, and by using the slot you decrease the woofer effective diameter by 82%. So, for the simulation of your speaker I decreased the woofer diameter by 82% (diameter X 0.18). With the slot the woofer seems to be more controlled, but, IMO, not much of a difference.
Attached Files
File Type: pdf PCGAB_SIM_Parameters.pdf (203.2 KB, 62 views)
File Type: pdf PCGAB_SIM_Parameters_Full.pdf (203.3 KB, 41 views)
File Type: pdf PCGAB_Simulation.pdf (274.8 KB, 59 views)
File Type: pdf PCGAB_Simulation_Full.pdf (274.9 KB, 43 views)
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