After long reading and considerations, I decided it would be good to find out if I was able to build a small Synergy horn using CNC and 3D printing. There are many designs floating around, but most of them just do not fit my idea of size and complexity of build. SPL Runt looks like a good candidate for such a project, so I will use it for inspiraton.
The target is crossover to bass at 135 Hz and 120 dB / 1 m at full power. Or as close to this as practically possible. Crossover via DSP, option for passive would be nice. Speakers to be used - most probably BC 8PE21 and DE500 for the prototype. Most probably, other CD will need to be used (e.g. BMS 4550). Prototype will use 18mm MDF, since that is what I have at hand.
Step 1 - 3D model - is done (well, without some details depending on step 2).
Step 2 - Hornresp model to tune the design. Attached. Not sure, if this is good, bad or usable. To me it seems I can reach my target with a bit of EQ.
Step 3 - prepare CAM files - WIP.
Progress with other steps will follow once I get back home next week.
The target is crossover to bass at 135 Hz and 120 dB / 1 m at full power. Or as close to this as practically possible. Crossover via DSP, option for passive would be nice. Speakers to be used - most probably BC 8PE21 and DE500 for the prototype. Most probably, other CD will need to be used (e.g. BMS 4550). Prototype will use 18mm MDF, since that is what I have at hand.
Step 1 - 3D model - is done (well, without some details depending on step 2).
Step 2 - Hornresp model to tune the design. Attached. Not sure, if this is good, bad or usable. To me it seems I can reach my target with a bit of EQ.
Step 3 - prepare CAM files - WIP.
Progress with other steps will follow once I get back home next week.
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Interested in your progress as well. The size of SPL-runt (wider and shorter) is actually very good for a 8' ceiling home theater installation.
The horn parts should fit onto a 600 x 800 mm plywood sheet. No box designed yet🙂
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So after some problems with CAM and also the router itself, all the parts are machined now. The final unit will for sure be in plywood. But even the MDF should fit together well after some sanding. I hope I will have a few minutes tomorrow to glue some of the parts and I will also print the throat adapter.
Once cut, this thing is really tiny🙂 Definitely a good learning step before trying to build a large 2 way box in future.
Once cut, this thing is really tiny🙂 Definitely a good learning step before trying to build a large 2 way box in future.
Primary and secondary flares are being glued together. In dry fitting, there was some slight misalignment due to machining errors, but it seems the result will be usable. I wonder how difficult it will be to glue together🙂 The driver flange is just being printed as well. The last things to sort out are the insert nuts and making a cone plug for the 8PE21s. Pictures will follow later.
Some would call them "machining errors", others would call them "opportunities to practice wood filler skills" ;^)
My wood filler skills certainly need practice🙂
Dry fitting has shown that gluing these together will not be that easy. Any tips or ideas?
Dry fitting has shown that gluing these together will not be that easy. Any tips or ideas?
Screws. Ratchet straps. Bar clamps.
Kreg pocket hole jigs make putting the screws in at the correct angle easy, though you may still need to use wood filler to cover some heads.
Kreg pocket hole jigs make putting the screws in at the correct angle easy, though you may still need to use wood filler to cover some heads.
Since the sides are square, I will mount some scrap pieces to the bottom, align with the top and bottom and use tape ratchet straps to hold all together. And maybe a screw here and there.
It did not work really as expected. Next time, I will route some jigs for gluing everything together. There is still some free space on the board for them. I tried to align as square as possible and hope that gravity "clamp" will be sufficient.
Conical horns are easy they say. Well,my first one is definitely not perfect, but it will work. I need to buy more wood filler🙂
And I will try a different way of gluing next time. I need to figure out how to drill holes at the correct angle for fixing the panels.
And I will try a different way of gluing next time. I need to figure out how to drill holes at the correct angle for fixing the panels.
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You could try packaging tape for difficult to clamp areas like the secondary flare to the main flare.
IIRC, Bwaslo recommended dots of superglue to hold horn pieces in place while the wood glue dries. I used his method and it worked for me.
I think it will look OK when wood filled and painted with a textured paint. Any plans for the round to square transition and mounting plate?
8PE21 seems an odd choice as its a conventional FLH driver with very little xmax, isn't this a limitation in output for the low end?
8PE21 seems an odd choice as its a conventional FLH driver with very little xmax, isn't this a limitation in output for the low end?
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I filed and sanded it a bit and it does not look that bad at all. Now wood filler is drying. The round to square plate is 3D printed. I filed the throat flat and it is almost a perfect fit. Since this is just a prototype, it will be fine.
I chose the 8PE21 since that is what I have now. This box is to be used from ca 140 Hz up and when I use the 2.5 mm Xmax spec from BC, I get very close to 120 dB with full power and over 125 dB above 300 Hz, which is for use with a midbass horn or a Paraflex kick bin. For home and garden parties this should be more than fine.
Once I am happy with this - especially with the crossover, I will build two boxes out of 18 mm plywood including the outer shells. There are many 8" to choose from, I just did not want to buy four new now.
I chose the 8PE21 since that is what I have now. This box is to be used from ca 140 Hz up and when I use the 2.5 mm Xmax spec from BC, I get very close to 120 dB with full power and over 125 dB above 300 Hz, which is for use with a midbass horn or a Paraflex kick bin. For home and garden parties this should be more than fine.
Once I am happy with this - especially with the crossover, I will build two boxes out of 18 mm plywood including the outer shells. There are many 8" to choose from, I just did not want to buy four new now.
You've probably seen/use this already, but in case not, the painter's tape trick for gluing miters together is cool. Masking Tape Clamps | Tricks of the Trade - YouTube
I've found the Kreq jig is way best so far, for holding the secondary flares' 4 corners together.
Drilling holes at the correct angle, to put together the primary cone, continues to be a real challenge. No amount of simple careful eyeballing seems to work worth a dang.
I now use an angle gauge i hold on the horn, set to show the angle i need to keep the drill at. Helps ALOT...but i still miss occasionally 🙁
I've found the Kreq jig is way best so far, for holding the secondary flares' 4 corners together.
Drilling holes at the correct angle, to put together the primary cone, continues to be a real challenge. No amount of simple careful eyeballing seems to work worth a dang.
I now use an angle gauge i hold on the horn, set to show the angle i need to keep the drill at. Helps ALOT...but i still miss occasionally 🙁