April 7, 2014

HE3 form factor

Which bass module would you prefer?

The speaker on top has a familiar form factor, with a dome tweeter and 6.5" midrange driver, but with a twist. It features 93 dB sensitivity, high enough to be driven by most valve amps. The bass module will feature a ported DSP powered 10" woofer, except version B which fits a larger 12" driver. 

A - a simple box where the front is angled to match the front baffle of the speaker on top

B - side walls angle out to fit a 12" woofer

C - both front and back angled out

D - a simple rectangular box

April 6, 2014

PSE-144 dispersion

PSE-144 almost maintains its horizontal pattern control down to 250 Hz, with modest midrange narrowing. At very high frequencies the pattern narrows. Around 5 - 7k one can see that there is a difference in the axial and off axis response from around 15 - 40 degrees. This is very useful data to consider in making choices about what to correct in the crossover and how this speaker should be set up in a room.

The horizontal design beamwidth is 80 degrees.

The directivity waterfall plot shows the same data in a different way. The data is shown with the minimum smoothing the software allows (1/12 octave) and here we can see the effectiveness of the dispersion control employed in this horn. The crossover point is not evident in any way.

PSE-144 launch update

PSE-144 is nearing the launch of the first run, which is now closed. Orders will ship in around four weeks. New orders will begin around May.

Here you can see one of the prototypes being tested:

The prototype is being tested here at a height of 3m into the air. At this height, it does prove a challenge to get the mic high enough. These measurements are used for the crossover and the additional height provides greater resolution due to a longer measurement window.

In these photos you can see one of a number of prototypes made in the process of perfecting the manufacturing process. It's not obvious in these photos, but there are some imperfections that are being corrected, as a very high standard of finish is expected here. These are being made by a very well established Australian fibreglass manufacturer.

PSE-144 has midrange extension to 200 Hz and horizontal pattern control that approaches the Schroeder frequency in domestic listening rooms.Although it's difficult to evaluate a speaker with no bass extension, when listening to a live acoustic recording at the end of a weekend of testing there was an impression of live dynamic realism - a very clear, articulate and uncoloured sound.

Coming soon:

  • There will soon be opportunities to hear this speaker in Melbourne
  • New orders due to begin around May
  • Contact Red Spade Audio regarding pricing, lead time or other questions

April 5, 2014

AV8 directivity sonogram

Here we can't provide the normal 6 dB down line due to sharp diffraction dip that occurs on axis around 2.7k. This quickly disappears off axis and so in this normalised sonogram it does skew the perspective a little. In practical terms, although the audibility is not likely a real issue, listening a few degrees off axis removes the dip.

If more smoothing is used, or a shorter time window with the measured (caused by gating where the speaker is not elevated high outdoors), then this issue becomes spread out over a broader range.

Overall we see good directivity performance with a gradual narrowing trend towards 3k above which the directivity is fairly constant before narrowing at the top end.

PSE-144 testing

Although PSE-144 is light due to fibreglass, it did prove a challenge to test on my turntable given the height of the platform and the depth of the horn. The mouth is placed at the pivot point of the turntable.

PSE-144 is nearing release of the kit version. Shown here is one of a number of fibreglass prototypes being tested.

March 31, 2014

AV8 8" home theatre speaker

 AV8 is a home theatre speaker based on a 1" compression driver, 8" waveguide and 8" midbass driver. Shown here on my measurement turntable where the dispersion performance is tested. The MDF enclosure is rubber lined for vibration damping and it's also sealed with fibreglass resin to resist moisture changes, hence providing a good substrate for the textured paint finish that will be applied. 

AV8 is a 93 dB speaker designed to reach THX reference levels with an ordinary AV receiver. It has an 8 ohm load, 70 Hz extension and a small box. Being an AV speaker, it's anticipated that it will be placed near the wall. This particular pair is designed for a client where it will be placed on a pro audio bracket.

The midwoofer has a clear coating which helps to damp cone breakup. When testing the raw driver with no filters in place, this is audible in comparison to lighter untreated cones. 

This is an alternative driver that was tested, without the treated cone. It has higher sensitivity in the upper midrange, but cone breakup is clearly audible. Although a cheaper driver, the savings are likely lost in a more expensive crossover.

Woofer baffle. Neo magnets are hidden in the baffle for grille attachment of woofers. These are machined manually, not via CNC, since they are machined from the rear of the baffle and this doesn't easily suit the CNC process, where all work is done from the top side. This is done with a drill press manually, then what remains is filled with bog. A straight cut bit is used, since a drill bit would not let the magnet get close enough to the surface without breaking through. 

The baffle above is for the surround (AV8S).

CNC panels laid out:

Rubber sheets line the box for vibration damping. 

Front baffle:

AV8S construction. Damping rubber and some of the lining is attached during assembly, as access is limited after.

Woofer baffle is double thickness.

Keyhole brackets allow the box to be installed to the wall. You can also see a recessed section around the speaker terminal cut out. This allows a speaker wall plate to be located here, so all cabling is hidden, and installation is simple, with no need to offset the speaker from the wall.

Top and back of the surround (AV8S). Dual ports fire up out of sight.

Sometimes you just can't have too many clamps!

The compression driver/waveguide for the surround is angled down 15 degrees. 


AV8S (surround) rear sitting upside down. Here I've used a neo driver to keep the weight down.

AV8 rear:

Dayton Titanic ported sub

The new Dayton Titanic Mk 4 15" sub driver is very appealing. This is a custom sub for a client as part of a home theatre system. In this design, I've used a down firing design to keep things simple in terms of grilles, high driver excursion and little fingers. A key feature of this design is a large slot port with a generous flare at the end.

Good aerodynamics here is the key to ensuring the port does not limit the LFE potential. 

The internals of the port are pre sprayed as there is no chance once fully assembled.

Solid timber feet avoid the weight of this heavy sub bearing down upon the MDF feet. The feet near the port are angled to avoid interference. 

Polyurethane glue is used here for extra strength, along with screws into each solid timber insert.

After complete assembly, the edges were all rounded over with the router and the box is sealed with fibreglass resin to provide a more stable substrate. Often prior to finishing, raw MDF expands and absorbs moisture, resulting in a seam appearing, which then requires more sanding.