DIY “High-Resolution add-on tweeter project”

by Maarten van Druten


My new speakers PureAudioProjects Trio 15 Voxativ are very good loudspeakers,
they are a big improvement over my older loudspeakers.
I also bought them because they have a modular design and that they leave room for further
experimenting and tweaking.

The orginal PuraAudioProjects Trio 15 Voxativ
D'Appolito setup: "Woofer-Fullrange-Woofer"

I am very satisfied with the standard setup (were the full range speaker is placed between both woofers)
but personally for me the full range-units are placed a little bit too low this way, making me feel that the musician is performing
while seating, instead of standing.
Therefore I started to look for a possible solution...
Luckily the holes in the aluminum PureAudioProjects Trio 15 frame
have also the possibility to place the loudspeaker-units in a "Woofer-Woofer-Fullrange" order!

So I did placed my PureAudioProjects Trio 15 Voxativ in this "W-W-F" order, and
the character of the music changed a lot.
I heard from others that they didn’t like it, but personally I like it much better.
The total projection is now much bigger, while the advantages of the earlier “D'Appolito” setup
are now gone…. the current "W-W-F" setup sounds more lighter more clear,
and best of all another interesting change is now possible…
Now there is room to place an “add-on tweeter” at the top.

Let me explain further:
Note: this is my personal point of view:
Like all other
full-range loudspeaker unit brands, the lowest mid-bass and the highest
frequencies are not the specialism of this type of loudspeakers.
The specialty of full range loudspeakers are the mid frequencies.

The Voxativ full range unit is an
excellent high-end loudspeaker unit that renders a lot of hyper detail,
and has a very smooth sound character.
The Voxativ unit can perform very nice high frequencies, and there there is no need for a upgrade.
So why I'm borthering myself to change my speaker setup?

On my PureAudioProjects Trio 15 Voxativ with the Leonidas XO there is
a jumper on the cross-over (XO) board
that can be placed in two ways. (“on” or “off”)
on means "filtered", and off means "unfiltered"

The "Leonidas XO" from the PureAudioProjects Trio 15 Voxativ

Close-up of the "high-cut" jumper on the Leonidas XO board.

By turning this jumper on, (see photo above) the Voxativ full-range loudspeaker get’s filtered a little bit so
the highest frequencies are smoothly muted
(1 order).
This makes the sound character of the Voxativ even smoother, and I personally think:
much better.

So I decided to keep the jumper setting “on”.
But every change has an (mostly negative)effect on something else.
The advantage of turning this jumper “on”, is that the Voxativ sounds even more neutral,
more fluid and more appealing for long term listening.
But the disadvantage is that the frequency above 8000 Hz gets muted with a first order XO slope,
so that the highest frequencies (16.000 Hz and more) are now missing.

Still the music sounds very pleasing, and comfortable, but for playback High-Resolution music
I'm missing now a lot.
So my idea was to place an “add-on” tweeter on top of my loudspeaker
But I didn’t want to intervene the current design.



On the "X-Fi show" in the Netherlands, I listened to this speaker of the Dutch company "DAUDIO", called "W1".
The "W1" is a loudspeaker with an active XO, and the sound of this speaker made a big impression on me.
I never heard such open, wide, transparant and full of hyper detail high frequencies.
After listening to this fine loudspeaker for some time, I asked someone of DAUDIO which tweeter they used.
They were very honest about it, and they said it's they used the "Mundorf hifiAMT 25D1.1" tweeter.

DAUDIO W1 loudspeaker from the Netherlands, amazing sounding loudspeaker, with the
AMT 25D1.1 dipole tweeter.

After some investigation, I heard that this was possible to place an additional tweeter to my current
loudspeakers without changing the current XO.
This can be done by placing the + and – wires of the “add-on tweeter” at the beginning
of the PureAudioProjects XO.
The main signal get separated this way, one goes to the Leonidas XO and the other to
the add-on tweeter.
There are no unwanted disturbances this way.
Another design goal I made myself was that the PureAudioProject Trio 15 Voxativ loudspeaker
may not be altered or damaged in any way.
I’m very cautious about my speakers because I like them very much!


An idea was born

One think became clear after this impressive listening session with the DAUDIO W-1,
I wanted also this superb high-quality high-frequency sound in my room!
So the idea was born, to "add" an AMT tweeter to my current loudspeaker system.

Because these Mundorf AMT tweeters are not cheap, (they cost 329 euro a piece) I decided first to test with another tweeter instead, just to make sure that an additional tweeter could enhance my current PureAudioProjects Trio 15 Voxativ loudspeakers.
I had a pair of "Lyric" loudspeakers stored in another room, and I always found that they had very nice sounding tweeters and also their XO is very good designed.
So I opened my old loudspeakers and I took out both tweeters and the XO's
The tweeters are of the brand: “Vifa” H25TG-05 (6 Ohm)

The XO from the Dutch "old" loudspeaker brand "Lyric" the XO is very well designed by engineer: Jan Smet.
Many aircoils, and only the best quality parts were being used.

The first step - making a prototype

So my first idea was to use wood for building the first prototype, but after some consideration I decided
to use a different kind of material for this temporary test setup...
I have choose to use even more easier to handle material named: “foam-board”
because of the following reasons:
- foam-board is flexible in depth, it's two layers of paper with foam in the middle
  so you can place it easily between tight spaces.
  (I used 3mm but it can be squeezed also in an area of 2.5mm)
- foam-board is also very easy to cut, even round shapes.
  Because it’s paper glued on foam, with a scharp knive you can do almost everything.
- It’s also very light and strong, speaker units till 700 grams is no problem for a temporary test setup.

But my Vifa tweeter units had very heavy magnets so I had to make a construction to strengthen
my primary design a bit.
Otherwise the tweeter would fall back.

Also working with foam-board goes very fast, I made these test frames in half an hour.

Foamboard is being used for this temporary test setup, it’s light, strong and doesn’t damage
the PureAudioProjects Trio 15 Voxativ.
I placed the tweeter foam-board panel in the space between the metal frame
and the PureAudioProjects panels.

Foam-board is very easy to work with, within half an hour the tweeter panels
were ready to test.

It's important to make accurate measurements, so the tweeter unit will have a good fit.

Here the original Danish made “Vifa” H25TG-05 (6 Ohm) tweeter is attached with nuts & bolts to the foam-board frame.

The test tweeter setup looks very nice :-) because of the weight of the magnet a
additional "strengthen bar" has to fitted. Otherwise the tweeter would fall backwards…

The foamboard test tweeter panel can be placed easily, there is space at the top, between the Voxativ panel and the aluminium frame.



Listening to music

Finally it was time to listen to these “add-on” tweeters.
I played DSD music files and SACD iso’s over JRiver Mediacenter using DoP (DSD over PCM)
My Audio-Gd Master 7 DAC with Amenero module has been placed in 2X oversampling
and is connected with ACSS cables to the Audio-Gd Master 10 amplifier.

Wow! what an improvement! by placing the Leonidas "high-cut" filter on "ON"
the quality of the Voxativ unit improves a lot, but the down side is that also a lot of information is lost...
By placing an additional tweeter like I did the whole picture has become complete again.

I was lucky because the match of Vifa (original Danish units) with Voxativ seems to be a good one
There was no need to change the tweeter XO, the match was fluently and was perfect.
The music sounds very well, if I should give myself a number, I should say it's 95% now.
So I could live with this setup for a long time, and I'm enjoying my music very much.

But the crystal clear high frequencies of the "DAUDIO W1" with it's hyper details, that level
has not been reached yet...
So before I will buy two Mundorf AMT
25D1.1 tweeters, I have found myself a very comfortable temporary solution.

This project will have a continuation soon, because Leon Huijgen himself is coming to listen to my
current setup!

To be continued...



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