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.

December 23, 2012

S3 prototype construction - part 3

This is what happens when it falls on the floor! A "not happy Jan" moment! Turns out it was a lesson worth learning. This was put together with PVA glue and screws - I later removed the screws. The impact of a fall from the bench had it all fall apart immediately. The glue had set, but clearly there was not enough strength to stay together. 

For now I'll build just one and test.

Brackets were made to attach the mouth flare.

Attaching the mouth flare. Brackets hold each piece in place. Previously I assembled these with the mouth face down, but this method lines up the pieces at the knee much better.

Now assembled:

I used polyurethane glue for the mouth flare. It's a bit of a pest to work with and takes longer to set, but has four times the strength and expands to fill any voids. As such, it's much better at fitting together panels that aren't perfect. It takes much longer to achieve perfect and on a prototype, I certainly don't think it's worth the extra time.

The ooze on the glue is a good sign - it means no voids. I used construction adhesive on S2 and it wasn't reliable enough.

Remember, this is a prototype! It can be dressed up later if desired, but speed is the important thing. It's all about testing the design and moving on to the final version ASAP!

In seeing all this, you may start to realise that building a point source horn is quite difficult! Even for an experienced wood worker.

Coming up:
  1. Work on ports
  2. Throat profile needs to be filed out
  3. Smoothing the horn profile overall
  4. Trimming the mouth
  5. Driver mounting
  6. Stand
  7. Testing and evaluation!

December 20, 2012

ESL Electrostatic kits coming

Today I picked up an ESL Electrostatic panel from Involve Audio, with a view to building a kit around it.

Kit will include a CNC machined baffle and there will be a woofer module sold separately.

December 15, 2012

S3 prototype - part 2

More progress on the prototype. 

Brackets the hold on the second flare.

Lots of brackets:

My expert assistant (aka dad) drilling:

This one has been a team effort, with four involved this time.  

Plugs for the ports:

The ports didn't come out quite right. They were machined by CNC but I made a mistake with their location, a mistake related to rushing! So I've had to mark out the corrected port locations.



Mouth flare termination:

 Drilling new ports - not exactly a job for the average power drill! The table needs to be large and a drill press probably wouldn't do this, because they would all be too small. The shop smith is ideal here.

S3 prototype in progress ...

Construction began today on the S3 point source horn prototype. The aim is to test the design prior to progressing further. 

Parts were CNC machined, but without any angled edges - these were done manually.

CNC parts:

Mounting plate turned on the lathe:

Edges needed to be angled on the buzzer, and sometimes needed some tweaking with the plane. This won't be required in the kit, but this kind of thing can be required when not relying on CNC for all machining.

Mouth panels:

This prototype is pretty "quick 'n dirty" but the final versionw will of course be very well sorted.

November 15, 2012

Bathurst room treatement video - measurements

Here are the measurements that go with the video demonstration at Bathurst of acoustic treatment.

Frequency response:

Untreated: red
Treated: grey

You can see the bass range is similar, but in the midrange we see more differences due to the treatment.

Unsmoothed version:

Untreated: red
Treated: grey

Below 200 Hz (smoothed)

Untreated: red
Treated: grey

 Perhaps the most interesting result is the reverb time:

Untreated: red
Treated: grey

In the untreatd room, the reverb is quite high, with an average above 0.7s and this drops off at higher frequencies. In the treated room, the reverb time is more flat, and averages around 0.32 s. 

By 100 Hz, both rooms are similar in reverb as the treatment is midrange focused. 



90L sealed 18" woofer flat pack - assembly

Suggested construction sequence for 90L woofer flat packs.

Much quicker and easier to assemble!

You can see here how the trench has been machined around the edge so that the pieces can slot in easily. The corners are at 45 degrees to allow the box to go into the corner on an angle, as a base for horns. The terminals are on the back flat section.

I prefer to use PVA glue generally, as it sets fairly quick. Expanding poly glue is stronger, but greater care is needed and it takes longer to set. The extra strength isn't required and I tend to use it where I need its gap filling properties. 
Front baffle sits on top of the base, side sits on the trench. A small clamp holding the side to the front baffle is suggested.

Now add a vertical brace.

The first horizontal brace slots into the groove of the side panel. The CNC flat pack is designed to minimise the need for a lot of large clamps. (Yep, a shameless plug right there!)

For this step, you may want to use one of these:

 You can buy 30 of them in varying sizes for $10, they are dirt cheap and very handy.You can use a pair on the right edge of the front baffle, to secure the second horizontal brace. You can use them to secure the vertical also from sideways movement. Place one either side of it on each horizontal brace.

Right side piece

Angled side.

Back end is best added last of all sides.

Top panel.

And finally the outer baffle.