PureAudioProject - Trio15 Lowther DX3 with "Leonidas" crossover review
by Maarten van Druten   UPDATED!


UPDATE 16-5-2016
I had a very interesting second listening session at Leon's studio, to read about it, see the end of this article


My loudspeakers are over 20 years old now, they served me very well but now it's time for something new.
So currently I have started my quest to find new loudspeakers.
In the loudspeaker world, the choice is enormous, transmission line, line array, dipole, bipole, full-range wide banders, or magnetostatic loudspeakers?
I have listened to many different loudspeakers during my life, but there was never one loudspeaker that really made me smile...

They all had concessions at some point, one speaker had a very nice projection and sound-stage but was lacking deep bass, the other was sounding very nice but has a sweet spot that was so narrow that if you moved your head only a few centimeters the sound stage collapsed

On the X-Fi high-end show 2016 I heard the active “daudio W1” dipole loudspeaker, which is made in the Netherlands.
The sound of this loudspeaker really made me smile!
This loudspeaker has an “Mundorf” dipole
air motion tweeter hanging in the air with wires, and this tweeter was sounding very, very good.
The music was transparent, it's was everywhere, even if you turned your head all around it was if there was a big cloud of music was hanging in the room, the bass was also very good, with lots of definition, deep but certainly not muddy.
The only disadvantage was it's price for 17.500 euro a pair, this speaker was too expensive for my budget.
One of the audio developers of "daudio" told me that they were working on a smaller passive version of this speaker in the 5.000 euro range.
That sounded as music in my ears, but then I have to wait...
I'm not sure if I want to wait so long because the release date of this speaker is still unknown...

PureAudioProject: "Leonidas crossover"

Then I noticed a article on the Internet about the “PureAudioProject” (= PAP).
They designed a modular open baffle design loudspeaker, that is very affordable.
According the few reviews on the Internet their sound was something special, and they sounded much better than commercial high end loudspeakers costing even four times more.
And they won many “Best of Show” awards.
They have multiple models, two caught my interest the Trio TB15 Voxativ with Leonidas crossover and the smaller Trio 10 with an Mundorf air motion tweeter.

I became very interested in this concept, and I wanted to listen to this special loudspeaker.
After some searching on the Internet, luck was smiling to me, because one of the crossover designers of the PureAudioProject loudspeakers was living close to my neighborhood!

So I contacted him, I introduced myself and asked if it was possible to listen to this
Pure Audio Project loudspeakers.
Leon Huijgen responded quickly and invited me to his design studio!
I was very excited, and I can not remember when the last time that I got excited to listen to loudspeakers

Leon was already waiting for me at the door when I arrived, I introduced myself, and Leon was very friendly and showed me around in his studio where he designs and test his loudspeakers and crossovers.
Leon Huijgen is an loudspeaker designer that designs loudspeakers not from a technical starting point but from experience, and just to practical listening.

This practical approach comes also back in his crossover designs.
For the PureAudioProject has Leon designed a very interesting crossover that is adjustable.
It can be easily adjusted to some ones preferences or to the room or both.

The Leonidas crossover


The designer himself "Leon Huijgen"with his creation the "Leonidas crossover"

If you are interested in a more technical information about "
Fletcher & Munson curves"
Leon sent me this document about "X-overing an Open Baffle loudspeaker" that he was willen to share with us.
Link click here: "About X-overing an Open Baffle loudspeaker" (PDF)

Note: this document is NOT about the "Leonidas crossover", but an variation of it.

Lowther DX3

When I entered his listening room two Pure Audio Project Trio 15's were already warming up.
I was very excited to listen to them, because I have never heard them before.
Leon explained that he used the “Lowther DX3” widebander loudspeaker unit in this TB 15 setup.

The Lowther DX3 widebander in the PureAudioProject Trio 15

The Lowther DX3 from the back, and of the OB-A15neo woofers!

Of course the “Leonidas Crossover” was also present in this setup
For this listening session Leon used a Marantz SACD player SA15 mk2 and a
Jungson JA-88D Class A Integrated Amplifier.
We played many different music numbers from a compilation CD
How does the PureAudioProject Trio 15 sound?
First of all, after reading reviews of others I was a little afraid that the bass would be absent.
This was absolutely not the case, bass was certainly there, and it was fast, tight, and well balanced.

The sounds was very transparent en the projection into the room was very good.
One thing became clear to me right away, the quality level of this loudspeaker was
very high, this speaker delivers everything without any trouble, at this price point
this loudspeaker is a “steal” (in Dutch we say “geheim tip”) a insider secret, explaining
that this loudspeaker preforms at an remarkable high level

Another very important thing I learned that day was, that every speakers needs a minimum power level to work optimal.

The PureAudioProject Trio15 can also play very loud.
Before listening to this dipole loudspeaker I was used to a “boxed” loudspeaker were the sound comes only from one side, but by this dipole concept the sound comes from everywhere!
Because of this the music sounds much more realistic, “more live” and also it sounds like if the music is played much louder than normal

Then Leon played Pink Floyd at a very high level
The music sounded amazing, without any trace of distortion!

Every instrument was very detailed and available without any sharpness
Leon's preferred setup was a little bit different than my preferred setting
I personally like the music to be played a little quieter.

I also found that the mid tones were a little too dominant
But this is about personal taste.
And this exactly were the amazing Leonidas crossover comes into place!
With this adjustable crossover the decibel settings of each loudspeaker can be adjusted in absolute phase to the preferred level!

So Leon told me, for example that he could adjust the both PAP A15 NEO woofers with + 6dB so that the full range Lowther DX3 still could play on it's preferred level, and that total sound balance would more to my personal taste.

And this is terrific news, a speaker system that is adjustable to someone own preferred taste is a very big welcome in the world of High-End.
No more concessions but tailor made musical presentations just how it should be.
The modular PureAudioProject Trio 15 project is an very adjustable system, were not only the loudspeaker units can be easily replaced or changed, thanks to Leonidas crossover now also fine tuning is possible in absolute phase!

Unfortunately Leon didn't had a Voxativ speaker unit available for testing, because I was also very interested how this unit would sound with his crossover.
After listening to the PureAudioProject Trio15, we listened to an TB 10 with two Morrel 10 inch woofers and a Fostex widebander.

Leon's own version of the PureAudioProject Trio 10 with Fostex widebander loudspeaker

close-up from the front and back


After listening to the Trio 15 with the Lowther DX3 this was not an improvement
especially the Fostex was no mach for the Lowther DX3.
In comparison the Fostex sounded flat, clean, even a little bit lifeless...

Then Leon had a nice title surprise for me!
He placed two little MDF two-way tranmissionline loudspeakers on the stands...and he played the same CD again.

I was impressed, seldom I had listened to such a musical, well balanced loudspeaker, these little speakers sounded very, very good.
Seldom I had listened to such a musical, balanced nice loudspeaker
After Leon told me that this little speaker cost only 199 euro's (materials).
I was totally amazed! He explained me that this was just a workshop speaker for students to build it them self.

Unbelievable, this speaker sounded much better (more musical, and better balanced) than many so called high-end speakers I have heard in the shops.
Leon quality to use his own ears for his speaker designs rather than just following theoretical rules really showed off here
For example the crossover in this little speaker contains only one resistor, this makes the sound so very pure and well balanced sounding.

After listening to this amazing little gem, we installed the Pureaudio Project TB15 with the Lowther DX3 again

Trio 15 listening session 2:

Remarkable was also the wideness of the projecting of the music from the Lowter DX3
Normally a widebander has the effect to give the music al little narrow projecting, but not this Lowter DX3, it had a better defined and also a wider sound stage.
Sometimes I could hear a strong “S” sound by some recordings but I cannot explain what was the reason of this, I only have listened this loudspeaker once.

I was very happy after this amazing demonstration of Leon Huijgen's creations
The PureAudioProject loudspeaker are really sounding amazing, and thanks to Leon's “Leonidas crossover” the optimum result can be achieved.
Everybody has a different taste, the is no good or wrong, it's not a fight who is better.
It is all about fine-tuning the music, so you will find what sounds for you the best.

With this unique Leonidas crossover you are definitely on the right track!


UPDATE 16-5-2016

Leon sended my an email that he discovered the reason why the midtones were a bit dominant by the first listening session.
He explained me that the XO he was using was also used in the Trio 10 setup.
Only Leon forgot to adjust the components back for use in the Trio 15.
Therefore the midtones were 3 dB to loud, and that was what I was hearing that day.

So problem solved, and luckily my ears are still working :-)
Leon invited me for a second listening session, because he had something special for me.

Of course I was more than happy to visited him, when I entered his studio, I saw a glimpse of a new speaker he had build.



Leon had build in only two weeks time a scaled down version of a loudspeaker that looked a little bit like the Voxativ - Ampeggio Due.
Leon told me that this speaker was a one experiment only, just to test his finding.

Of course I wanted to listen to this small loudspeaker.
The sound was very good, remarkable was the deep bass, especially for a loudspeaker this slim.
This speaker could also hang on the wall.
The units used in this speaker were just old one's Leon had laying around.
Later newer better units are going to be used

The sound-scape was also wide, but I was missing something. it looked like the loudspeaker was missing some top end.

Then Leon came with surprise.
He placed something small on the speaker and connected it to the current setup

Then we started listening again...
Unbelievable, now the sound-scape was much better, better defined
Now not only the balance of the music was better, also the bass seemed to go deeper.

What was it what Leon had done?


Leon had made a small wooden board with a dome tweeter in the middle
A small wooden diffuser was placed at an angle above it.
For the XO only one capacitor was used.
So that the tweeter comes in at 10.000 Hz

Because the tweeter was pointed upwards, a very comfortable diffuse cloud of sound
was created.

Because of the reflection a delay should be present, but the fact was that in reality
this "delay" was almost inaudible

How is it possible that only one small tweeter could have so much effect on the total presentation?
Not only the definition was better also the bass was sounding much deeper
Leon told me that this was a common effect, when a super-tweeter was added to the system.

I asked if it was possible to add this tweeter to the PureAudioProject Trio 15
Leon laughed? are you sure?
I asked him why we laughed, He said this tweeter costs only 0,50 cents! .....
First we listened to the PureAudioProject Trio 15 without the super-tweeter,
And then Leon installed this tweeter on top of the PureAudioProject Trio 15

I was amazed, also here the same dramatic impact was clearly audible
The definition became clearer, the sound-scape opened, and the presentation of the total music became better balanced.
Also the bass seemed to improve by this amazing 0,50 cent tweeter.

After this listening session I was truly convinced that the PureAudioProject Trio 15 will be my new loudspeaker system.
I have ordered the Voxactiv Trio 15 by PureAudioProject.
After my holiday I was do an extended review about my new loudspeakers on this site.

I want to thank Leon for inviting me and for sharing his experiments with me.
This "super-tweeter" was a very impressive one, I'm sure this experiment will be continued in the near future.
Leon has allready made some newer prototypes, and he has send me the following photos, he called them: "Leonidas 3D 2I" (= 3 dimensional image improvers)


They look very promissing, I will write more about them soon!

Audio Dandy

P.S: Many thanks to Leon Huijgen for this hospitality and for this very impressive, and interesting listening session.

For more info about the "PureAudioProject":



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