90L woofer flat pack

This is a flat pack for an 18" woofer - sealed 90L box. It is designed to go into a corner under a horn, but it could be used for other systems as well.

 

CNC machined for easy assembly, with trenches machined so pieces fit together nicely and bracing also slots in. 

The design is similar to my prototype:

The prototype above was built manually. I no longer have time to build things this way, everything now with CNC. 

Shown with a smaller Unity horn.

S3 revised sims

S3 shown in black compared to S2 (simulated response).

You can see that S3 allows a higher crossover point than S2, which is one of the design goals. The response is also smoother, meaning a simplier crossover should be possible.

S3 in progress

I'm currently getting the S3 design ready for a CNC quote, lots of checking to make sure all aspects are correct - quite a meticulous process. For example, I found that I had an incorrect model of the Celestion midrange driver. The area in front of the cone forms part of the acoustic chamber, an important aspect of the design. I've had to model it again to work out the volume precisely and ensure the driver slots right in.

Here is the render of the 3D model:

I could model it with even greater precision than shown, but this is as good as it needs to be.

Unfortunately I also thought I had the throat profile design complete, then found it didn't model as well as I'd like. The process takes a lot of time, due to all the twists and turns, and ideas that in the end don't work!

The goal is to have S3 up and running as a Christmas project. Drivers for the current batch are now on their way and we have a couple of places left.

Bathurst acoustic room treatment comparison (384kbps)

This video is a stereo recording of music playing in two rooms identical in dimensions, but one is treated. Credit goes to Earle Weston for the creation of this video. It was recorded with two Shure mics in the listening position. The video footage corresponds to the audio, so when you see it jump to the other room, that audio also jumps.

Bathurst 2012

It's that time of the year again - Bathurst 2012! I call it the audio event of the year, where a small group get together not far from the race track and play music much too loud, way too late, talk way too much, drink way too much and somewhere along the line find some time to do some nerd stuff ...

Bathurst 2011 >

This year we created a video to compare two identical rooms, one untreated and the other treated. The video will go online and instantly jump from one to the other. We measured the difference in room acoustics and set up the speakers in exactly the same spot. I don't know how well the experience will translate but I have to say the treated room was so much better, I can't imagine anyone would prefer the untreated version.

A couple of snap shots ...

HE2 running on a Weston Acoustics amp and a Marantz CD player:

HE2 running on the first passive crossover, a minimalist design:

 A mini tutorial on measurements with REW:

 The untreated room with two diffusers added to a very large room.

 The treated room, speakers set up in the same position:

The black speaker that looks like a Darth Vader helmet is called the Frank!

S3 progress

Here is a sneak peek at the S3 throat:

In S2, this aspect wasn't modelled very carefully because I built it manually, using a combination of filling with bog and smoothing with a circular file and sand paper. S3 will be sculpted with a CNC router so it has to be right.

The profile is critical in this design.

I have a couple of goals here:

• avoid diffraction
• create the smoothest possible transition from the exit tube (circular cross section) to the horn where the midrange units come into play (rectangular)
• keep the machining cost sane
• retain constant directivity performance

Cheap self watering pots for sale!

Pickup in Melbourne:

 

$10 each or $100 for all 12.

They work exactly the same as any other you would buy from Bunnings, they are just a whole lot bigger! Made from large plastic drums, 600mm diameter, around half a metre high.