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BLH for CNC?
BLH for CNC?
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Old 23rd February 2019, 03:46 AM   #1
Roo2 is offline Roo2  Australia
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Default BLH for CNC?

Hello,
I'm lucky enough to be booked in to an induction to learn how to use the CNC router at my local library. I'm going to sign up for the laser cutter and 3D printer inductions too. A nice local government initiative to stimulate creative industries.
Anyway.. I was thinking it'd be fun to make a pair of back loaded horns down the track. A bit like the attached photos might be a nice project. The acrylic sides are a very interesting concept..Possibly an acoustic compromise?
Any suggested designs / driver recommendations please? I'm aware this is a really open question
I have an engineering/fabrication background, can drive Autodesk Fusion 360 reasonably well to develop the designs. I am a bit time poor so would prefer to head down the path of some proven designs without getting into too much theory.
I'd be happy to spend $100-150 per driver. Maybe a bit more if theres significant benefit.
Slender floor standing enclosures preferred but maybe something on a stand would be fine. WAF is important so nothing too big..
I want to use a single full range driver, no crossover, no tweeter (might consider a high pass if necessary).
I have a Yamaha streaming pre-amp going into an Aleph J class A amp ~20W. I listen to a wide range of music. I like a bit of bass and realise I might need to supplement with a sub down the track. So maybe a 4" or 5" driver unless there's some larger options that still do the highs well?
My listening environment is likely sub optimal. Rectangular room about 4m x 8m. High 3m ceilings. Timber floors and walls, lots of windows.
Not looking for the pinnacle of audiophile quality. Just a nice project that will likely sound and look pretty good.
Cheers,
Andrew
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File Type: jpeg BLH2.jpeg (14.7 KB, 107 views)
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Old 23rd February 2019, 01:46 PM   #2
chris661 is offline chris661  United Kingdom
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The problem with the smooth internals is that there's not much of a filter between the back of the cone and the outside world, so you'll get a lot of midrange mush coming out. Designs with a lot of angles and sharp bends will form a better low-pass filter, so you've got (useful) LF coming out.

With regards to known designs, how about this:

- Frugel Horn Mk3, with Alpair 7s
- Acrylic side panels if you like
- 3D print a diffraction reducing device that'll sit around the driver and provide a low-diffraction edge instead of the 3x sharp edges that are usually nearby

It incorporates a well-known design, adds some techie tweaks that'd make it look/sound a little better. Reasonably small form-factor, and decent performance.

Chris
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Old 23rd February 2019, 09:26 PM   #3
Roo2 is offline Roo2  Australia
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Thanks Chris. I started reading the frugal horn mk3 thread last night. Looks like a good option. Thanks also for the feedback on the smooth internals.
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Old 24th February 2019, 01:47 AM   #4
CraigSu is offline CraigSu  United States
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Quote:
Originally Posted by chris661 View Post
- 3D print a diffraction reducing device that'll sit around the driver and provide a low-diffraction edge instead of the 3x sharp edges that are usually nearby
Have anything in mind, Chris? Maybe a supraBaffle of some kind?
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Old 24th February 2019, 04:08 AM   #5
Roo2 is offline Roo2  Australia
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Do you think the diffraction reducing device could be CNC milled from thick plywood to get that “relief map” appearance?
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Old 24th February 2019, 10:13 AM   #6
chris661 is offline chris661  United Kingdom
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Quote:
Originally Posted by Roo2 View Post
Do you think the diffraction reducing device could be CNC milled from thick plywood to get that “relief map” appearance?
Yeah, probably.

Quote:
Originally Posted by CraigSu View Post
Have anything in mind, Chris? Maybe a supraBaffle of some kind?
I was thinking of something that'd be the same width as the original baffle, but surface-mount the driver to the baffle.
Add a really shallow waveguide that curves round at the edges to meet parallel with the side/top walls. Taper it smooth to the surface of the baffle below the driver.

It's the sort of thing where I'd start with 18-25mm ply, cut the driver hole, and then work on it with a sander until I got something good.

Remember, big roundovers are your friend.

Have a look at the Wharfedale D320 for an idea - it looks to me like the baffle is added on, and would reduce diffraction a lot compared to just flush mounting some drivers to a baffle with square edges.

Chris
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