June 21, 2017

Rythmik 12" flat pack

We now have a standard flat pack for the Rythmik 300W kit:

This is designed for the 300W Hypex amp version, which has a slightly larger enclosure than F12. The height is increased to gain extra volume.

Rythmik custom curved sub prototype

We're offering this prototype build for sale. Contact us to express interest.

CAD diagrams show the design details which might not be as clear in the photos.

June 17, 2017

JV60 crossover upgrades

It's not unusual for us to receive numerous emails each week asking if we still offer upgraded crossovers for JV60. This is one that we built yesterday:

These are hand made with quality parts and the modifications I used as a JV60 owner. The mods were make or break in my case, resulting in keeping my JV60 speakers for many years. I actually found the sound to be more enjoyable than many high end speakers, priced well above $10k. The sound is smoother and more refined.

Crossover upgrades

We actually offer crossover upgrades for any speaker.  This includes:

  • Hand built crossovers using the same design but upgraded parts
  • Design mods to adjust the sound to your preferences
  • Modified designs to suit new drivers
  • Custom crossovers for custom speakers

June 13, 2017

Emerald Rock Studio

In most cases, our services are engaged after a client has already purchased acoustic treatment. Very often we are called in when there is a specific and objectionable problem they were not able to solve with generic and free advice on the internet. Here we started working with the client before the studio was built and so this meant we could ensure a great result right from the start.

Bass traps

Most bass traps on the market are best described as "low midrange" absorbers. Their effectiveness is typically very limited. Here we built custom bass traps, running floor to ceiling. The traps are 340mm deep and 1000mm wide. One in each corner.
The bass traps are resistive and operate deliberately into the mid and treble regions. The advantage here is that they serve a dual function and actually reduce the amount of midrange absorbers that would otherwise be required. The traps were built as 8 modules, which were then bolted together once delivered onsite. A further advantage of the large depth is that they are more stable. These traps were made with Polymax XHD which we also sell as raw panels for DIYers. 

Vicoustic Wavewood panels are mounted either side of the rear corner bass traps. This space is also a band practise space. It was important to create a neutral sounding room which was not overly dead. Part of creating this balance was mixing diffusion and absorption.

Vicoustic Multifusors are installed on the ceiling. These are very cost-effective panels and we like how easy they are to install. Being a light weight polystyrene panel, they can be installed with self adhesive picture hanging strips. It's an easy DIY install, which avoids the extra cost of a professional install job. 

It was actually this product that first prompted us to become a Vicoustic dealer - it was clear that many of our clients needed an easy to install low cost diffusor.

SVS SB1000 subwoofer set up under the mixing desk. We consider this sub to be a value leader. It's a capable sub with very good performance for the price of a raw driver and amp. Many studios install a cheapie sub and most of them are simply not worth using. The temptation is often there to buy a sub in the $500 - 700 price range. These can only be considered "junk subs." It's a very good idea to spend just a little more for a sub that is far superior. We provided the sub along with calibration. We tested every feasible sub location, finally opting for the most practical placement with the best performance. Here a nearfield location worked best.

Very often the placement of the monitors and their relationship with their surrounds can create issues. A very accurate monitor is easily undermined with poor setup and a hit and miss approach. We worked through various options with placement to determine the optimal setup.

Products and services included here:

  • Consultation on design and layout of the space prior to construction
  • Acoustic treatment design
  • Custom acoustic treatment
  • SVS sub
  • Sub integration 
  • Audio calibration

June 4, 2017

Point source mini - realising a compact point source speaker

This is a speaker we've wanted to create for some time. Perhaps our most versatile ever. We wanted to create a compact point source speaker. It would cater to some unique situations:

  • nearfield monitors
  • a small room where a deeply involving sound stage is desired
  • valve and lower powered amplifiers
  • a centre channel speaker that can be placed on its side
  • a surround speaker with equal horizontal and vertical dispersion to serve more than one row of seats
  • a premium Atmos ceiling surround speaker (which doesn't measure so badly the response plot has to be hidden)

These are quite diverse situations but all of them benefit greatly from a point source speaker. We decided to commence working on this project and the first step was finding the right driver.

One promising driver was the Eminence Beta8CX. The parameters were quite useful and initially it seemed quite appealing that any compression driver with a thread could be tested. We're quite fussy on which compression driver we use as they are very often make or break with HE designs. Price was also an attractive feature. We know that people don't tend to spend big on surround speakers, so this was a key issue.

The Eminence driver has useful sensitivity and works well in a reasonably compact enclosure. However, when we tested various compression drivers, we noticed a serious problem.

There is a broad 15 dB valley from 4 - 11k. We tried various compression drivers but all exhibited a similar problem. Even with the benefit of a DSP active crossover, the sonic result was poor. One of our requirements was the ability to use a passive crossover, where we don't have the option to simply add EQ to a valley this large.

A further challenge with coaxial drivers is that they tend to be expensive. Money does not necessarily buy you exceptional performance. The reality is the coaxial drivers are difficult to get right.

Here is an example of one of the better units:

This woofer is mounted in a different enclosure so it's not directly comparable in all respects, however, the far superior response in the treble region is clear. Despite being one of the best, we can still see some obvious problems. Numerous dips in the woofer response above 1k where we are likely to want to cross to the tweeter. A peak just above 4k which is very audible. We can also see that the compression driver has very limited bottom end response.

The Game changer

Here we have a driver that changes the game. Without this driver, this project would not get off the ground.

In contrast to the cheaper stamped steel frame of the Eminence, we have a very solid cast frame. There is no dust cap here. An accordion cloth surround ensures very long life and very control of the cone edges.

The compression driver is integral to the design. Shown above is the back of the phase plug and you may also notice the copper shorting ring. This arrangement provides much better alignment of the acoustic centres.

Here we can see the best of both previous drivers. The woofer has a well behaved response, free from the problemmatic dips and breakup of the pro coax. We also have a very nicely extended top end without a falling response that needs to be corrected - this makes for a simpler crossover. Overall, a much more usable driver. Our first trial with a very crude crossover revealed a musical result - this is a very good sign.

Rythmik Audio Subs in Australia

As our long time blog readers will know, we've held Rythmik subs in high esteem for a long time. We first experience them back in 2006 and it was clear from the first moment they were fired up that these are articulate subs. The very clean and dry bass sound was clear even before they had been calibrated correctly. We are now Australian dealers for Rythmik subs. We offer their full range of kits and we also custom build finished subs, adding Australian-made enclosures to Rythmik kits. 


Rythmik kits include the driver and servo enabled amplifier. Both are integral to the design and sold together only.

We also offer flat packs, which are CNC machined to fit together and make for an easier build. These start at $399. Our standard designs are modestly sized 12" and 15" sealed subs, however, we can also create custom flat packs to suit any project. 

We can offer:
  • sealed
  • ported
  • open baffle
  • horns

Custom made subs in Australia 

We manufacture subs in Australia based on the Rythmik kits. 

This is one of our 15" subs (sealed). Neo magnets are concealed within the enclosure - they serve to attach the grille without unsightly old clips.

Featured here is a custom sub with dual 12" drivers, serving to reduce vibration. The client wanted a perspex cover instead of a conventional grille. Designed to match the existing entertainment cabinet in solid teak.

June 2, 2017

Active keyboard monitors

A client approached us to help upgrade their music system. This application was unique because the system would be connected to a digital keyboard. It could be argued that they wanted to create a live music experience at home, literally. Initially the interest was surrounding an accurate custom sub. However, when we heard about the monitors they would be using, the conversation changed. They were intending to purchase some monitors we had worked with before. We do come across quite a range of studio monitors in our consulting work. We proposed an alternative custom monitor and the result is seen here.


First we start with an Air Motion tweeter. Well regarded by many for their transparency and air. Of course, a tweeter with "air" in it's name must have air! And it must have motion, or it won't tweet very well. Bad attempts at humour aside, these are tweeters we don't normally use. One of the reasons is that many of them don't suit our designs. Another is that the response is often not as smooth as we'd like. However, in this case, we are using an active crossover which can overcome this aspect. Here we offered a choice between a silk dome and an air motion - they chose the latter.

For the midwoofer, we were looking for a smooth response with an extended top end. One particular driver that stood out is the Vifa NE180W-04 6.5" midwoofer. In this regard, this driver is exceptionally smooth out to around 14k with the exception of one peak around 5k. A curious thing about this particular driver is the very different response shown for the 8 ohm version. Differences are common here but usually they are quite subtle.

Also important here is the ability to achieve reasonable bass extension in a sealed enclosure - adequate to cross to a sub. Often our goals would suggest a 4" or 5" mid but the bass requirements suggested a larger woofer.

We also liked the open basket design, which is ideal in terms of avoiding any coloration.

Low diffraction design

Given the intended use as a nearfield monitor, we considered that baffle edge diffraction on axis is actually more important than usual. We can easily see diffraction effects in our testing and crossover development, but in a typical real world situation, much of what we see becomes swamped by the room effects. In a nearfield situation, what we measure in our testing is closer to what the listener experiences. Room effects are more subtle.

In order to minimise diffraction, we did two things. Firstly, we carefully placed each driver with offsets optimised to tame the impact of diffraction on frequency response. Secondly, the baffle edges are rounded, which is especially important when using a small tweeter without any loading from a waveguide. 

Here you can see the impact of the roundovers on a 1" tweeter that is mounted in the middle of the box. This is the extreme case, as this is the worst possible position for a tweeter.

Again we've removed the round overs and shown the impact of tweeter position only. We've now moved the tweeter into its final position. 

Here we can see that now adding the round over further improves the smoothness (red). 

Now with the woofer, we compare the impact of the roundovers with the woofer (below). As you can see, the roundover has less effect than with the tweeter.

 We have little choice with placement of the woofer but some adjustment is still beneficial.

The black line shows how the final position compares to the middle of the box. There is not a great deal of difference but if we did have a crossover near 2k, we might be facing a challenge. 

Now we've added the impact of the roundover and we can now see that it benefits us more than when placed in the centre. The dip around 2k is reduced, although the effect is subtle.


The enclosure we used here is a braced 32mm MDF with separate sealed chamber for the tweeter and DSP amplifier. The walls are internally lined with 15mm rubber sheets. The result is when knocked, it's like knocking on a concrete column. The cabinet is internally filled with acoustic material.

Here we can see the raw farfield frequency response. In this measurement, the drivers are simply mounted in the enclosure and then tested with no DSP filters in place. We did test with a cap on the tweeter, so its low end roll off has been modified. 

We see a gentle hump around 1k which is also seen in the datasheet. The woofer peak at 4.3k is related to the driver itself and is also seen in the data sheet. The smaller ripples in the woofer response are +/- 1 dB excluding the general trend.

The tweeter exhibits a rising response. This may be behind many of the subjective comments about these tweeters when this isn't corrected. In comparing it to other tweeters, we did notice what sounded like greater deal but also a thin sounding bottom end. This measurement explains what we heard. 


Here we used a MiniDSP ICE amplifier with two channels for each speaker. The DSP crossover allows for very precise control.

One of the things we like about DSP active crossovers is the precision with which we can control the response. Although passive crossovers can be quite sophisticated, we find there are limits to what we can achieve, at times with a difficult compromise between response shaping and part count. With a DSP crossover, we typically have more filters than any design is likely to need. 

Here we have now achieved a response of +/- 2 dB.

We also evaluated various settings to adjust the tweeter level. In this case, we found that a near flat treble response produced the best results and the most balanced sound. 

One the crossover design work was complete, the original character of the tweeter changed significantly. The exaggerated top end detail and thin sound was replaced with a very balanced sound. Still, there was no question that its detail was very appealing.

June 1, 2017

Are you waiting for a reply?

We receive daily inquiries through our web form, both on the blog and our main website. We normally aim to reply to all messages the same day, if not the following.

In some instances, we find out that our reply has not been received.

If you don't receive a reply within 48 hours, please let us know.

Just today we received an email notifying us that this is the third attempt to contact us. In this case, we had replied to all of three messages.

Aside from our web form, we can also be contacted through our facebook page, which can avoid problems sometimes encountered with spam filtering.

When contacting us, consider including your mobile number which provides a secondary option to check our reply is received.

May 25, 2017

Celestion Ditton 66 mod

Celestion Ditton 66 is a speaker that many enthusiasts have refurbished. 

A client came to us with a modified version. All the original drivers had been replaced with new drivers that its owner hoped would work well.  

As you can see, the front baffle has been modified with chamfered edges, which is a good idea, especially with a 3/4" tweeter which is highly sensitive to baffle edge diffraction. A Hiquphone 3/4" dome replaces the original along with a Morel midrange dome. Bass is handled by an Acoustic Elegance TD12X and is augmented by a Scan Speak passive radiator. 

Testing the original crossover with new drivers

Our first step was to test the existing crossover with the new baffle and drivers. As expected, we found a significant mismatch. 

Above: Gated farfield response of the new drivers with the original crossover. Green: Mid dome Blue: Tweeter Black: Tweeter and mid network.

Here we can see a number of issues, all of them quite common when changes are made without a crossover redesign.

1. The dome has a broad hump in the low end of its passband, which effectively shelves down the treble at 1.4k by 3 dB.
2. The top end of the dome has a hump centred around 5k - this is critical because the intended crossover is here. 
3. The treble response falls with rising frequency, resulting in a loss of perceived top end detail.
4. Mismatch between tweeter and mid levels.
5. The high and lowpass slopes overlap so that when combined, there is a broad hump from 4 - 14k in the treble response.

In short, we have a mess! 

Moving on to the woofer, we can see that the existing crossover is asking a great deal of the dome mid. The red plot shows the farfield response with the nearfield shown above. 

Choosing a crossover strategy

There are a number of ways we can move forward with a project like this.

1. Fully passive - we could have simply redesigned the crossover. Many people like this option because it allows flexibility to use any amplifier. The downside here is that this requires many large and expensive components. Low grade caps and cored inductors are common to keep the cost down. However, with very high end Acoustic Elegance woofers, we would consider it a bad idea to bottleneck them in this way. 

2. Fully active - this is a very popular option amongst DIYers. For this speaker it would have meant 6 amp channels (3 stereo amps). This option is most attractive where it allows drivers to work together which might have a difficult relationship in a passive design. 

With this speaker, we have drivers that can easily work together in a passive design. However, we felt the best option overall was a hybrid approach.

3. Hybrid crossover - passive tweeter/mid crossover actively bi-amped - here the client was able to use the two amps he already had. We designed a new passive which is simpler than the original. It contains a high pass for the tweeter and a lowpass for the mid. This new and much simpler network made it feasible to use higher end compnents whilst sticking to a modest budget. 

The new passive network

This is the new tweeter/mid passive network:

We were able to make it simpler by omitting the midrange high pass network - this would be handled by the MiniDSP active crossover. A further advantage we like about this approach is that we can shape the response further without adding more passive components. 

The response shown here includes DSP filters which provide further response shaping to the mids in particular. The response is +/- 1.5 dB.

Augmenting the bass response

An active implementation for the bass network has advantages that are well known. We avoid throwing money at big expensive passive parts and we also avoid wasting a great deal of amp power. Instead, we can use some of the headroom gained to augment the bottom end response. 

The final response is shown here:

Above 200 Hz the response is +/- 1.5 dB


In some speakers we find that a better subjective balance is achieved with a response that varies from flat on axis. This proved not to be the case here. This speaker sounds best with a flat treble response. However, the advantage of DSP implementations is that this can be easily changed. It's a simple matter of creating a different profile in which the bass and treble level can be modified.

Enclosure fill and the crossover

Did you know that the enclosure fill and the crossover have a relationship with each other? This proved to be true with this speaker. We found the amount of fill in the original to be inadequate. We wanted to raise the crossover point as we knew it would benefit the dome and the woofer would allow it. The problem was that enclosure resonances were interfering with the top end response of the woofer. If it were a sealed enclosure, we could simply fill the whole box. However, to preserve the operation of the passive radiator, the amount of lining is limited. The very large passive bass network also limited the amount of lining that could be used. Removing it meant we could use more lining, resulting in a smoother top end response.

How does it sound?

When it all came together, we noticed a well balanced sound. Smooth yet detailed top end with a nice integration throughout the entire range. The bass is clean, controlled and full bodied. Soon after our client had spent some time with them, we received a call. Usually this means there is a problem to solve - happy customers tend to enjoy listening to the music rather than call back to tell us about it. In this case the news was good. A happy customer describing the sound in very similar terms to those I've used. Even his wife commented on the improvement, noting that a particular track now sounds better than ever.

March 7, 2017

Melbourne room acoustic workshop

Would you like to know how your room performs acoustically? Would you like to know how to measure your room and more importantly, how to understand what the results mean?

We're offering the chance to learn about room acoustics in the room that matters most - yours. We're offering this with a twist. In a typical room analysis session, we work one on one. To keep it affordable, we limit the time and cut to the chase, moving to the interpretation and what to do about it. You don't get the chance to learn how to take the measurements and how to interpret them.

Hosts wanted

The best place to start is as a host. As a host you will learn about your room and come away with clear direction specific to your room, system and aspirations. Since all participants pay to enter, you pay less and you're getting more time. It also promises to be an enjoyable social event in the tradition of the Aussie audio GTG (get together) BBQ.

You need:
  • an audio system that you enjoy with either music, movies or both
  • enough space for 5 participants to attend
  • availability from 10 am - 5 pm


Participants wanted

As a participant you get to learn about room acoustics in a system and room that is different to your own. If you've already used our room analysis service, then you may like to learn more about how it's done, as this involves content we don't normally cover. The best way to learn and retain what you've learnt is with a hands on approach. Every system and room is different.

If you would like to attend, either as a host or participant, register your expression of interest via our contact form.

February 24, 2017

PSE ultra passive crossover

Introducing the Ultra crossover:


One of our PSE horn customers requested an ultra high end version of the passive crossover. These parts are in cost-no-object territory and they are among the best available. Where possible we used Mundorf Supreme Silver Gold and Oil caps. All cable runs are beneath the board, which serves not only to avoid visual clutter but also to assist with holding the caps in place. All caps are secured with adhesive rather than cable ties. Inductors are Mundorf foil types.