PURIFI finally did a fully purified passive speaker design! The SPK 16 prototype is here - with a PTT tweeter

[fluid]

Another issue I’m receiving feedback on is the roundness of the edges. Probably material costs to sand down till that level, and the rigidity of the edges. Most of the services I reach out to only allow for 15mm for the edge. I presume that would affect the sound significantly?

The way Purifi has drawn it is to have butt joints and the roundover split between the panels, but that needs each panel to be milled in a different way, which is no problem for CNC but not for basic cabinet construction techniques.

The way it is drawn in the image you showed is to make a square edged box and then run a roundover bit over the box after it is glued together. Doing it like that will reduce the strength of the corner and limit the size of the roundover that can be used.

 

[Kaladin]

Have you any pics?

I finished gluing on the front baffles and grabbed a pic. No sanding or anything yet other than the glue interfaces.

 

[Salt]

I would skip all roundings at side and rear walls, because they have no effect, as well even around the woofer.

 

[Luvchampagne]

How long have you been waiting for the drivers if I may ask?

2 weeks. Got them on sale.

 

[Philhifi]

I ordered and received the SPK16 kit, but I wanted to build something a bit different.

I went for an active build with:
• miniDSP SHD as DSP crossover, room correction (Dirac Live) and DAC
• 4 channels of Buckeye Purifi 1ET6525SA Eigentakt amplification (2× 2-channel)

Between the woofer amp channel and the midbass driver I’ll place a 1 mH air-core inductor.

The midbass cabinet is built with stacked lamination in American walnut: 18 mm walls, 26 mm baffle, 38 mm horizontal roundovers, ~8.5 L gross internal volume. Reckhorn ABX (alubutyl) for CLD, 2 cm Basotect (5 cm on the rear wall), plus sheep wool behind the brace. I’ll omit the passive radiators (for sale) and keep it sealed.

I failed to place the threaded inserts properly in the end grain for the woofer, so I had to model and order a custom CNC aluminium ring with threads.

On top of the midbass cabinet sits a custom CNC-machined PMMA plate that follows the footprint and roundovers of the cabinet and holds the tweeter. The rear of the tweeter is closed off by a sandblasted aluminium half-sphere.

This is my first speaker build.

 

[Salt]

What's Your intention for this modification?, and how does it look in measurements?

 

[Philhifi]

What's Your intention for this modification?, and how does it look in measurements?

I had a certain design idea that I wanted to follow rather than going with a standard box. Measurements to come.

 

[Soundproof]

I ordered and received the SPK16 kit, but I wanted to build something a bit different.

I went for an active build with:
• miniDSP SHD as DSP crossover, room correction (Dirac Live) and DAC
• 4 channels of Buckeye Purifi 1ET6525SA Eigentakt amplification (2× 2-channel)

Between the woofer amp channel and the midbass driver I’ll place a 1 mH air-core inductor.

The midbass cabinet is built with stacked lamination in American walnut: 18 mm walls, 26 mm baffle, 38 mm horizontal roundovers, ~8.5 L gross internal volume. Reckhorn ABX (alubutyl) for CLD, 2 cm Basotect (5 cm on the rear wall), plus sheep wool behind the brace. I’ll omit the passive radiators (for sale) and keep it sealed.

I failed to place the threaded inserts properly in the end grain for the woofer, so I had to model and order a custom CNC aluminium ring with threads.

On top of the midbass cabinet sits a custom CNC-machined PMMA plate that follows the footprint and roundovers of the cabinet and holds the tweeter. The rear of the tweeter is closed off by a sandblasted aluminium half-sphere.

This is my first speaker build.

Wow!

What an aesthetic delight!

Class!

 

[IamJF]

On top of the midbass cabinet sits a custom CNC-machined PMMA plate that follows the footprint and roundovers of the cabinet and holds the tweeter. The rear of the tweeter is closed off by a sandblasted aluminium half-sphere.

Such set on tweeter baffles are not as good as a widely rounded cabinet - would be interesting how big the influence is in reality. (off axis measurements horizontal and vertical)
But looks great!

The crossover design of the original one is very good - I would try to measure and match that with an active design before going on and try improvements.

 

[Matt_Holland]

Between the woofer amp channel and the midbass driver I’ll place a 1 mH air-core inductor.

What’s the reason for this?
I know there’s a series notch filter recommended for these woofers.

 

[Philhifi]

What’s the reason for this?
I know there’s a series notch filter recommended for these woofers.

From what I have read, most of the benefit can be had by using just an inductor to reduce the hysterisis of the alu cone midbass. Lars Risbo futher commented on that in the facebook forum saying that it should be at least 1mH.