# My first speaker project, CNC project!



## CraigRobbo (Feb 14, 2010)

Hey guys.

So I got a CNC machine a few months back, I have been making little parts here and there and decided to make a speaker project.

These are going to be just small bookshelf speakers for the hobby room so will be space savers.

The drive units are generic OEM units so won't be anything spectacular these speakers will mostly be about the look!

Okay so here goes: CAD drawings:


















I decided the wood veneer was not what I wanted, I think the black and silver looks much cleaner:












and here is were I am upto so far:





























Thanks for looking!

Craig


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## Wardsweb (Apr 2, 2010)

Way cool! I would love to have a CNC machine. The possibilities are endless. Congrats and have fun. I know you will.


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## fusseli (May 1, 2007)

Awesome styling, they really look great. I was going to ask about the top woofer and tweet being spaced fairly far apart and what crossover freq they'll be running at, but since this build is for looks I'm not sure it matters too much :T


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## CraigRobbo (Feb 14, 2010)

The speakers are relatively small only 12inches in height, The bass driver should be around 100hz and the tweeter/ mids will be about 3khz.

Thanks for the complements.

Craig


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## Moonfly (Aug 1, 2008)

Looks interesting, where do you get the design from. It looks a good project for a first attempt into speaker building.


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## CraigRobbo (Feb 14, 2010)

Moonfly said:


> Looks interesting, where do you get the design from. It looks a good project for a first attempt into speaker building.


The design was my own, I had 6 x 3inch drive units knocking about and decided to design a cabinet for them, I did take inspiration from other speakers and collaborated some of my favorite features together.


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## Moonfly (Aug 1, 2008)

Cool stuff. So are you going to have the fourth bass driver in the side of the cab too?


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## CraigRobbo (Feb 14, 2010)

Moonfly said:


> Cool stuff. So are you going to have the fourth bass driver in the side of the cab too?


Yeah, The drive unit for the bass I took out of another box, I enlarged by 0.5 of a liter and a slightly longer port just to extend the frequency slightly (but not so much to harm the driver, I hope)

I was thinking about buying on of these DIY amp kits you can get on eBay, they are a 2.1 amp and hook the subs up to the .1 channel.

I know it won't sound spectacular but for the hobby room it should be sufficient since its usually just back ground music.


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## Moonfly (Aug 1, 2008)

Sounds interesting. Obviously the rear woofer section would need to be completely sealed to isolate if from the forward section. I know 3 drivers can be a headache to wire up, so I'm interested to see how that works out. I suspect the woofer will probably struggle to keep up with the main drivers, but that shouldnt be an issue really if your not going to be playing these that loud.


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## CraigRobbo (Feb 14, 2010)

Moonfly said:


> Sounds interesting. Obviously the rear woofer section would need to be completely sealed to isolate if from the forward section. I know 3 drivers can be a headache to wire up, so I'm interested to see how that works out. I suspect the woofer will probably struggle to keep up with the main drivers, but that shouldnt be an issue really if your not going to be playing these that loud.


HI mate, Yeah they are sealed, In the cross section picture you can see the partitioning wall.

I plan to use a series of Caps, Coils & resistors to balance out the volume and control the frequency between the bass driver and mid range.


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## Moonfly (Aug 1, 2008)

What about wiring up those 3 drivers, are you going to wire them in series?


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## CraigRobbo (Feb 14, 2010)

They are wired in parallel at the moment


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## Jstslamd (Nov 30, 2010)

How big of a cnc router do you have and where did you get something like that. I've always been interested in them.


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## CraigRobbo (Feb 14, 2010)

Jstslamd said:


> How big of a cnc router do you have and where did you get something like that. I've always been interested in them.



It can machine 300mm x 400mm so it's not massive, just a small desktop machine really. I could make bigger speakers in prices then glue, fill and sand together.

I imported machine at a cost just under 2k


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## Moonfly (Aug 1, 2008)

CraigRobbo said:


> They are wired in parallel at the moment


What sort of load does that give you? I'd guess at something like a 3 ohm final load maybe.


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## CraigRobbo (Feb 14, 2010)

;'ll he honest, I have no idea how to work out ohms, I just presumed to wire everything in parallel, is series better!


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## Moonfly (Aug 1, 2008)

In theory parallel is the best way, but it really depends on the final load you want for the amplifier. Each driver should have an ohm rating on it. I guessed at 8 ohm drivers, and 3 in parallel would give you about a 2-3 ohm load if my maths is any good.


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## Jstslamd (Nov 30, 2010)

Just off the fly its may be better to run this as a two way or a two and a half way and run the woofers in pairs.


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## Moonfly (Aug 1, 2008)

Jstslamd said:


> Just off the fly its may be better to run this as a two way or a two and a half way and run the woofers in pairs.


And if he did that but with 2 mid drivers in each cab instead of 3, he'd have a two spare mid drivers from which a matching centre could be thrown together.


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## fusseli (May 1, 2007)

Shoot, Robbo. Your thread here has gotten me to thinking... and ya, I will have a CNC machine someday 

If you need help putting together a crossover, please ask! From the sounds of it that's where this project could use some improvement. We can all see that the cabs will be good to go.


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## Moonfly (Aug 1, 2008)

Ive just thought, if he ran with two mids instead of three, he's going to alter the cabinet volume each speaker sees, and have quite an impact on its sound. Removing one of the mids may not be possible because of that.


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## Jstslamd (Nov 30, 2010)

He could alter the internal bracing and close off the bottom front mid woofer chamber and open it to the rear woofer. Then block off a portion of the original woofer chamber to correct the air space required for the woofer.

Hopefully that made sense. It's early and I was dealing with a hurricane yesterday and this morning.


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## BD55 (Oct 18, 2011)

CraigRobbo said:


> It can machine 300mm x 400mm so it's not massive, just a small desktop machine really. I could make bigger speakers in prices then glue, fill and sand together.
> 
> I imported machine at a cost just under 2k


Now _that_ is the ultimate DIY tool; I am extremely jealous! What are you modeling in? I've used SolidWorks, Catia, and NX, but I think NX is my favorite for its power, and SolidWorks for its intuitiveness. 

This will be a fun build to watch, keep up the nice work! :T


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## Moonfly (Aug 1, 2008)

Jstslamd said:


> He could alter the internal bracing and close off the bottom front mid woofer chamber and open it to the rear woofer. Then block off a portion of the original woofer chamber to correct the air space required for the woofer.
> 
> Hopefully that made sense. It's early and I was dealing with a hurricane yesterday and this morning.


Ive seen some of this in the news, hope you guys are all OK, some people really didnt fare to well, and my heart goes out to those guys. Pretty heavy storm!


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## Jstslamd (Nov 30, 2010)

Where I'm at we didn't get it too bad. Lots of power loss and trees down. Some spots were flooded. All of the jersey shores from cape may(furthest shore south) to long beach island (central nj) got pounded. Tons of flooding and tidal surge floods. Many houses lost and all of the places we would vacation to we're wiped out. We shall band together and rebuild but I appreciate your concerns and thank you for your well wishes.


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## Zeitgeist (Apr 4, 2009)

Looks like the beginnings of a nice build. I'm pretty much envious of any speaker build that involves CNC work!


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## fbov (Aug 28, 2008)

CraigRobbo said:


> The speakers are relatively small only 12inches in height, The bass driver should be around 100hz and the tweeter/ mids will be about 3khz....





CraigRobbo said:


> ...I plan to use a series of Caps, Coils & resistors to balance out the volume and control the frequency between the bass driver and mid range.





CraigRobbo said:


> They are wired in parallel at the moment


Some thoughts...

3x 8 ohm drivers in parallel are 8/3 = 2.66 Ohms. Bad idea on any amp not designed for a 2 Ohm load. 

Make it a 2.5-way, with a single mid and the other two as the .5 drivers (rolled off early) and use high-DCR coils to bring up the impedence and this might work. 

Look for an electronic cross to the bass driver, since it needs its own amp if it's ever going to keep up with the triple. Also be aware that Chinese amp power specs. are far more than optimistic... don't expect more than 10W in most cases. 

If you'd like a rational way to figure out the right "caps coils and resistors," you're in for a long learning curve. You can start here:
https://sites.google.com/site/undefinition/diy-gettingstarted

Have fun,
Frank


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