December 30, 2014

PSE-144 crossover boards


HTS-215 is a horn sub kit with dual 15" drivers. 

It features:
  • ultra low distortion
  • 20 Hz extension with authority
  • extreme high output 
  • minimal box vibration due to the dual opposed driver mounting
The kit design allows for simple construction. For simplicity only some of the panels are shown here. The panels are CNC cut and slot together in a way that avoids the need for screwing panels together and mostly eliminates the need for clamping.

December 7, 2014

HE3 - an elegent valve friendly speaker

Here's a dilemma. How do you create a speakerthat meets all these goals:
  • easy for a valve amplifier to drive (benign impedance load and high sensitivity)
  • a slim and elegant design (tall and slender rather than wide and chunky)
  • pleasing tonal balance with full bass and no emphasised regions to get a high sensitivity rating
  • strong bass extension
Based on the questions I'm often asked, it's much harder than people realise. Often people don't realise the implications of each decision. If you want a slender box that isn't very big, with good bass extension, generally it's going to mean it won't achieve high sensitivity.Something has to give. 


HE3 is my answer. First we start with a conventional dome tweeter with fairly high sensitivity and an exceptional midbass driver - Acoustic Elegance TD6M. Here we achieve 93 dB sensitivity which is quite reasonable. Many speakers claiming higher don't actually deliver it. This is a spec that is often inflated excessively. Even individual drivers rated at 99 dB in reality may only have 93 dB of useful sensitivity.

Now the key in this design is that the bass is active, with a side firing 10" woofer. Here we dispense with high sensitivity and use brute force with a built in amp that also features DSP. The added bonus is that we can use EQ in the room.

Prototype coming soon.

Sonus Faber Cremona Auditor active crossover conversion

 The Sonus Faber Cremona Auditor is a fairly well known speaker using good quality drivers in a beautiful box. A client brought in a pair that he was not happy with, requesting an active crossover design. This is a speaker that measures quite well in terms of dispersion but it's not a speaker that handles higher levels very well. At moderately loud levels it sounds strained, most likely due to the use of a first order crossover with a ring radiator tweeter which is not ideally suited for a situation such as this which places heavy demands.

Raw response with the tweeter response raised for clarity: In reality they overlap each other.

No obvious breakup peaks are evident here.

The raw response of the woofer (green) shows a rise in the region from 700 Hz - 2.5k. This is eliminated with EQ (blue) and then a low pass filter is added.

 The same approach is used with the tweeter, first applying EQ and then a high pass filter.

Summed crossover.

This isn't shown here but I use a shelving filter to adjust the treble balance. This allows for a lot of adjustment later without messing up the crossover. 

This is just a quick snapshot and not the entire battery of measurements that were taken and analysed. 

Even a brief listen reveals an obvious improvement in the sound. The speaker is now entirely free of problems with a forward and strained sound.

December 6, 2014

HS215 - a horn sub with dual 15" drivers

Introducing HS-215. This is a custom job for a client and it's designed to sit behind a couch in place of a shelving unit. Designed as a flat pack where panels lock together such that large clamps can be avoided.

November 26, 2014

Speakers coming up at Red Spade Audio

I recently posted some speaker concepts I'm considering. 

The plan is now to develop all of them!

A: HE3 in slightly modified form with a single 10" active woofer
B: AV8 is already in my range
C: HE2 is already in my range
D + E: coming soon
F: coming soon

Out of the surround speaker options:

The two dipole surrounds are shelved, the third is AV8 already in my range and the one on the right side is currently in progress - it's a Coax 8" driver.

Articles coming up ...

Two article series coming up:

Acoustic measurement

There will soon be a series of articles coming together on the topic of measurement. A particular focus will be on helping people get started.

Active vs passive crossovers

A holistic look at passive vs active considering many aspects that are often forgotten.

Any ideas on articles you'd like to see?

November 24, 2014

PSE-144 - about using other drivers

A question we get asked often from those inquiring about PSE-144 is this:

'Can I use my own drivers?'

Often it's put this way:

'What is the price of PSE-144 if I supply my own drivers?'

This post is my answer to that question that keeps coming up.

About the drivers used

The drivers included in the kit are not available for separate purchase. They are included in the product as they perform better than the alternatives that people are likely to have in mind. They are purchased in large quantities and attract a better price than a single customer could purchase off the shelf. It's more than likely that if you are considering DIY favourites like B&C, BMS, JBL that we have actually tested the driver you are considering or something similar.


CD: CD144-08K

The high frequency compression driver matches a 44mm diaphragm to a 25mm exit. The kapton diaphragm achieves an ideal combination of damping and high frequency extension. This driver is carefully matched to the horn.

The vast majority of compression drivers fail to meet out standards and requirements. Setting aside specific requirements to match our horn, many of them cause listener fatigue and lack treble extension and detail. This speaker is designed to perform well with good quality solid state or valve amplification. There is no requirement to tame the sound with a mellow sounding amplifier.


Midrange: M425-08P

The mounting holes on this driver are machined into the horn baffles. For this reason alone, it's a problem to use other drivers as they are not likely to fit. The horn also has a mounting ring that precisely fits the driver.

The small matter of the crossover

Assuming that you are actually able to find drivers that will fit, an even bigger problem emerges - the crossover. Using your own drivers means that you are paying for a set of parts and developing your own crossover. Most DIY enthusiasts intending to "whip up their own crossover" have no idea about the size of the challenge they are taking on. It's an advanced design challenge and it's unlikely that most who are considering taking it on will actually appreciate all that they need to know in order to do it right. 

When you buy PSE-144, you aren't getting a series of parts. You are getting a well resolved product with years of development behind it. We understand the horn itself is a highly desirable one and many want to take this on as a DIY project but we don't recommend changing the drivers.


"Can you redesign the crossover for my drivers?"

If you have drivers that have the potential to work in this horn, we may consider this on a case by case basis. This would firstly involve a fee to test your drivers to ensure they have a chance of working. If they pass initial testing there would be a design fee to develop a crossover for your specific drivers. You would need to be ready to pay significantly more than the normal price, without promise of better performance.


"Can I buy the horn without the drivers?"

Yes, but you will need more than just the horn shell. PSE-144 includes a custom machined CD mounting plate, without which you will not be able to mount the tweeter. The plate is machined to keep the throat smooth. It also includes fixing points for the custom machined aluminium stand. 

The horn itself is a work of art, nothing like other horn shells available. It has a smooth durable gel coat finish on all sides - including the rear. Where the mids mount to the horn, it is filled with foam that provides mechanical damping. Where the CD plate mounts to the throat, cap screws fix it into metal inserts that have been embedded into the horn. 

The price without drivers is not much less than buying complete.

November 9, 2014

Scan Speak Revelator Tower

This loudspeaker is a custom design that features Scan Speak drivers. The tweeter is loaded into a waveguide which allows a lower crossover point.

October 27, 2014

Which speaker would you prefer for home theatre?

A - A conventional 3 way speaker with dome tweeter and 6" mid - 93 dB sensitivity on the top section,  with a pair of 8" or 10" woofers (active). A fairly slim speaker with plenty of bass extension.

B - 8" passive 2 way with compression driver, 8" waveguide and 93 dB sensitivity. More chunky with just enough extension to mate with a sub (80 Hz). Higher output than A and a more controlled dispersion pattern.

C-10" floorstander with about an extra octave bass extension over B. 94 dB sensitivity.

D - Satellite version of C, similar to B but with more output.

E - Highest output and sensitivity of all options, basically a larger version of D.

F - Second highest output of all options, cheaper than E but more chunky in appearance due to 12" driver and waveguide. Technically better waveguide but more "pro audio" in appearance.

October 23, 2014

High output surround speakers

This is a sketch of some high output surround speaker options I'm considering.

All feature an 8" woofer and onwall mounting.

On the left, a dipole surround with a side dipole array with dome tweeters and 3" mids. Next to it, a higher output version with compression drivers. Then AV8 for comparison and an 8" coax which has a shallower profile.

September 18, 2014

AV8 - home theatre speaker

AV8 is an 8" home theatre speaker with high output and sensitivity in a compact form.

PSE-144 white complete with bass module

PSE-144 white with bass module

Red Spade Audio Reference 18 sub

This is the first sub now available from Red Spade Audio assembled and finished - Reference 18.

Features a high excursion 18" sub driver and a 32mm MDF cabinet. 1 kW amplifier.

Finished in satin black (2 pack) as shown in the photo. Also available in various veneers in satin or high gloss finish as well as high gloss black.

Dimensions: 550 mm W x 600 mm H x 500 mm D.

Includes grille and solid rubber sub feet are provided as standard.

Why bring a sub to the market?

The market is flooded with 12" subs but I am finding that many of my acoustics clients appreciate something more. For many the option to go beyond existing subs on the market leads to multiple subs and it starts to become more expensive. This sub will do the work of around four 12" sealed subs without costing four times the price. I developed this sub as an option for my clients.

August 24, 2014

PSE-144 active DSP crossover - how does it measure

PSE-144 active version measured outdoors.

This is an outdoor gated measurement that has been elevated to around 4m. The mic was placed at a larger than  usual distance to capture baffle effects - this is not a near field measurement. 


July 31, 2014

PSE-144 in black

In the first exclusive run of PSE-144, black as seen here was by far the most popular.

July 1, 2014

Room Analysis case study

This is an example of a room analysis job for one of my PSE-144 customers. This client built two subs of my design - T20, intends to build multiple large 18" bass boxes along with my horn. The goal here was to figure out the best treatment scheme along with a suitable bass arrangement.

You can see there is a lot of brick in this room, which could be a recipe for disaster in the bass, if not for a large window across the left wall and some openings.

For testing here I used an old Wharfedale speaker with a 12" woofer in a sealed box, powered by a DSP amp. EQ is used to get it flat when measured nearfield:

After confirming the extension and smoothness of the test speaker, different listening positions were tested:

Listening positions: Orange: rear left, Pink: rear right, Green: middle front

Here you can see the two seats against the rear wall, with a third position with another chair in front, centred on the couch.

This measurement might lead you to think that the left rear seat is the one to choose. However, in reality much of the bass will play through both main speakers and only one is shown here. Summed mono, the combined bass is expected to even out the response.

Left (grey) and right (black) bass bins shown for the left seat

Now in the right seat, we also see the two bass bins:

Green = right bass bin, pink = left.

Again, when these are combined, we expect the dip will be smoothed out and we will see a fairly flat bass response with a hump around 40 Hz. Both of these seats end up with a similar bass response.

What we see here is that the combined bass response of the two main bass bins is expected to be good. We see no major need for a more complex multi sub arrangement.

Next we moved on to testing sub positions.

The results cover a 50 dB range.

The best overall sub position was the centre of the front wall (black), which is compared to the middle of the ceiling, such as may be used in an infinite baffle sub.

 Black - sub in middle front wall vs ceiling centre (green).

Below 40 Hz, the ceiling position has around 10 dB less output, and significant nulls. The main area of interest for a sub position here is below 60 Hz, as the horn in question is best operated below that point.

Basically, the central mid wall position in this room has the best mix of extension, output and smoothness.

The recommended treatment scheme here includes a little more focus on diffusion due to the dispersion control. There is less off axis energy from the horn. Hence, here I suggest retaining more of that energy in the room with a little more later arriving reflections at a lower level. This will retain some natural ambiance in the room and maintain spaciousness.

May 31, 2014

New measurement system

The new measurement system is almost ready. A galvanized steel pole slots into the ground, into a steel tube with a concrete footing and a cap when not in use. Triangulated ties attach to the fascia board, bolted in place to ensure stability. The main pole is 4m high. A block and tackle is used to lift the speaker from just above ground level. The old system was a back-breaker when it came to getting speakers up onto the turntable stand.

The new system also elevates the speaker higher than the mic stand will allow. A new and more stable mic stand is coming up next, with greater repeatability in position.

Not shown above is the turning mechanism, where a lever that looks like a periscope handle is attached to the bottom of the turntable.

April 18, 2014

PSE-144 up and running

People have been asking for photos of PSE-144 set up in a room, sitting on its bass module. Here it is - sitting on top of a 60L bass box with an 18" Eminence Magnum woofer, with a bass trap behind. The box is 600mm (24" wide) and the horn itself is 900mm wide x 600mm high.

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.