December 28, 2012

S3 prototype complete

The first S3 prototype is now complete.

The ports were shaped and bored out manually, the old fashioned way with a spade bit.

You can see plugged ports and a fair amount of bog:

 The panels were all shifted closer together so that no filling was required around the throat. I started with a very small hole, then filed away with a circular file.

Ports were shaped with a chisel. I know what you are thinking - 'why not the dremel?' This way is faster. There is a particular chisel that is curved and I can shape a port like this in about the time it takes for me to find the dremel!

Drivers added. B&C compression driver inserted first for no particular reason. I've used spade connectors so there is no soldering.

 S3 prototype - throat is shaped nicely and I found it's much quicker to get the shape when material only needs to be filed away - no bog! Time is critical. Why? Because I have a group who are now waiting for the flat pack that follows this prototype.

 There are two stands included - this is so that I can securely sit it in both orientations for measurements. When this thing is two metres up in the air, safety matters!

Measurements currently in progress.


  1. Great. Thanks for the update

  2. Hi Paul,

    I thought from your previous posts that there were going to be 6x closed back mid range drivers per horn, but your pictures only show 4x. How come? Why the change?



  3. I knew someone would ask. The design for this prototype was a bit of a rush and it became clear when I started building that I had not allowed enough room for the mids to fit on the sides. This aspect is quite tricky! So I've just used 4 for now. The initial results are very good. 4 vs 6 drivers - currently reviewing that one.

  4. Paul do you think that the simple tools you have used to create the frustrums and ports will be good enough to get a world class result? My concern is that there will be poor uniformnity between the ports.Perhaps you could modify a spade bit and create a profile that will cut the port opening and frustrum all at once. This has been done in the autoworld to create high performance valve seat profiles with repeatable results.

  5. Please keep in mind that this is a prototype - nothing more. The actual kit that follows won't be made with manual methods - so there won't be chisels involved or even modified spade bits or dremels. The kits will all be consistent and identical. I don't want to give too much away just yet, but manufacturing options are being considered.

  6. Not sure I follow -- what is the goal of this rushed prototype design? If it's not validating the actual design that will be used on the flatpack, and it's not validating the CNC parts fit together as expected, and various manufacturing options are still being many prototypes are you planning?

  7. The goal with this prototype is to test and refine the design. The only variation from an acoustic point of view, is the use of 4 mids. Already it meets the design goals but I'm refining it further. No further prototypes are anticipated, but of course we won't have all of them machined without testing the first one for fit.

  8. Hi Paul. I'm a bit confused about the purpose of this prototype now. In your first reply you mentioned that using four mids was a mistake due to not allowing enough room for six. Then in your most recent reply you say the only variation from an acoustic point of view is the 4 mids. I had assumed that you had changed the horn dimensions between S2 and this prototype. Did you change the horn dimensions? And if not, what was the point of this prototype?

  9. Why would I build another with the same dimensions as S2?

    S3 is a new design, it's actually quite different to S2. I am modifying the second horn to test 6 midrange drivers and I will be testing some variations to refine the design further. With 4 mids I can get the ports closer to the throat, but 6 generally model better.

    The first one with 4 mids actually measures quite well already. Where S2 had mids rolling off at 900 Hz, S3 already extends to 1.3k. I prefer to get them to extend as high as possible without significant compromise in other areas, since this is an extreme design.

    There is only so far you can go with modelling a design. Building a prototype and testing it with some variations helps you to take the design further. I could easily just settle on the first result, but I want to see how far I can refine it. I will be working on that this week then finalise the design and produce the 3D model that will firm up a price for getting these manufactured.

  10. Thanks for the clarification and glad to hear that the preliminary results are promising.


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