ACTEM -  Audio development
About us
I and my team of partners work together with you to meet or exceed your demands.
I know, that repeat business is the best business for both buyer and seller.
This has been my business model since 1980.

My name is Ole Lund Christensen, and I was born in Copenhagen on the
12th of April 1953.
I grew up in a family of science and engineering. My mother had a
M.Sc. degree in Chemistry and she worked as a researcher at Denmark´s
Technical University.
My father had a M.Sc. degree in mechanics, and he worked for the
Danish Government analyzing work accidents. He developed large
computer programmes to find the common cause of the accidents.

In 1972 I began studying engineering at Denmark’s Technical University.
A few years later I also found time to be a founder of Audiophil, a
Danish Hi-Fi importing company, together with Bo Christensen. (He
later founded Primare and BOW technology)
Raymond Cooke, the founder of KEF loudspeakers, visited us, and he
appointed Audiophil as the new KEF distributor for the Danish Market.

The company grew rapidly, and this dual work prolonged my study by a
few years. First I spent 3 years on doing the fundamentals of a
M.Sc.E.E, but because of my keen interest in loudspeakers, I changed
to a more relevant new multi education.

So I graduated as B.Sc.E.E engineer, but with mechanics, production
technology, electronics and acoustics courses mixed.
My graduation paper in 1980 was on horn loudspeaker design.

I then sold Audiophil to Per Lundgreen. See
I founded a Pro-audio import company together with Peter Olsen and
Susanne Kampmann. This company grew until it employed 14 persons and
did 2 million EURO pr year of sales of Pro-audio equipment in Denmark.

In 1982 we began manufacturing a Pro-audio power amplifier, called SLT 250.
It was using 28 MOSFETs and produced 2x250W or 1×1000 W in 8 Ohm.
It became the standard in most danish recording studios and PA companies.

In 1985-1987 I designed and supervised the turnkey construction of the
PUK Recording Studio. See
for photos and a
list of the artists.

“Studio Sound” magazine wrote, “It has focused the recording world’s
attention on the most unlikely site for a innovative recording

George Michaels “Faith” album was made at PUK, and it became the USA
no 1 for the whole year in 1987. Elton John’s best selling single
“Sacrifice” was also made at PUK. Many other artists like Depeche Mode
have since chosen PUK Recording Studio.
A major part of the PUK control room was a 10.000 W active 4 way
loudspeaker system and a unique room acoustic design. It was developed
together with Poul Ladegaard from Brüel&Kjær. See

Another major part of the PUK design was superior sound insulation
between the different rooms and extremely low noise and sound levels
in both the recording rooms and and the monitoring rooms.
This was done by floating the rooms on separate foundations, with
“Rockwool” insulation plates going down several meters into the earth
between the foundations.
3 layers off special very thick laminated glass in two independent
frames ensured that the sound from the 10.000W loudspeaker system did
not transfer into the recording rooms.

Denmark’s Radio did visit PUK, and they thereafter asked Poul
Ladegaard and me to analyse and suggest improvements to DRs main
control room.
DR decided to purchase a special loudspeaker from us, as rebuilding
the acoustics would have been too costly.

I have since built many of these rooms.
They integrate the loudspeakers with a room using my special acoustic
design. Together they making a sound so life like, that Professor
Robert E. Greene in “the absolute sound” magazine issue 124 called it
“Exploring the boundaries of the possible”.

In 1990 I began manufacturing Hi-Fi Amplifiers based on our
professional power amplifiers. They were called SiriuS, and they
became highly recommended in local magazines.

In 1995 I developed the SiriuS D 200, the world first Single MOSFET
200 W power amplifier. All other 200W analog transistor power
amplifiers had to use 4 or more output devices in parallel for the
positive signal path, and 4 others for the negative signal path, all
to share the power load. Even with careful selecting and matching,
they will not be identical, so the sound is a compromised mixture of
many different sounds.
The SiriuS D 200 used only one device in the positive signal path, and
only one device in the negative signal path of a push-pull power
amplifier. By virtue of not needing the parallel operation of the
devices, it offered a pure and unique sound, as well as a simpler
manufacturing process.

Some years later I got an interesting offer from a NY law company.
Their client wanted to buy the SiriuS trademark. So today the Sirius
trademark belongs to
the SiriuS satellite radio company in USA. See

I found a nice new name for my amplifiers in Websters. It was the word
“GamuT”, which originally meant “The entire range of musical notes” in
middle age Latin.

The GamuT D 200 Single MOSFET power amplifier received many awards
world wide, among them are:
Golden Ear award 2000 in “the absolute sound”, USA.
Editors Choice Best Buy 2003 in “the absolute sound”, USA.
Editors Choice award “Hi-Fi Choice”, England, twice.
Editors Choice award “Hi-Fi & Records”, Germany.
Reference in “Revue du Son”, France.

See more in Reviews on
In 2003 I sold GamuT, and I travelled and researched new technology
like the iPod, Blue Ray and 802.11 N (Wireless audio and video) for
CAT Science Park.

Based on the recording studio design experience, I custom build
listening rooms, amplifiers and loudspeakers for rich music lovers
around the world.

In 2007 and 2008 I worked in Kupio, Finland for Amphion loudspeakers.
I developed 18 new loudspeakers and expanded the export sales network.

My designs got very good tests in Hi-Fi magazines:
Amphion Prio 520 became a Best Buy in “Hi-Fi Choice”, England
Amphion Ion L became Best Buy in “Hi-Fi Choice”, England
Amphion Helium 520 became Best Buy in “Hi-Fi Choice”, England
Amphion Argon2 Anniversary became Best Buy in “Hi-Fi Choice”, England
Amphion Argon 3L became Best Buy in “Hi-Fi Choice”, England

The Amphion Prio 520 and the latest Prio 620 also got very good
reviews in “Stereo“ Germany, better than other brands at the price

The results were clear, Amphions exports sales went up by more than 100%.
Due to shared parts, inventory went down by 30%, and inventory turnover doubled.
In January 2009 I broke a bone in my leg on the ice in the Kupio Airport.
My doctor found in my blodtest, that I lacked vitamin D, which is
generated in the skin by sunshine. Vitamin D is vital for bone
So I decided to move south.

I have presented these Audio Engineering Society papers at the AES conventions:
“A Large Monitor Loudspeaker System Suitable for Digital Recording”
Paper Number:   2312    Convention:   79 (October 1985)

“24-Track Hard Disk Compared with 24-Track Tapemachine.”
Paper Number:   3316    Convention:   92 (March 1992)
“A Practical Guide to Acoustical Design of Control Rooms and Placement
of Loudspeakers”
Paper Number:   4252    Convention:   100 (May 1996)

In 2007 I presented this paper at the High End 2008 show in Munich:
“The advantages of using waveguides in Hi-Fi loudspeakers”
This paper got a positive mention in “Stereophile” magazine, written
by Paul Messenger, England most experienced loudspeaker reviewer.

I have spend a lot of my time in India. I was invited 3 times
to give lectures at AES meetings in Mumbai, and I have build one of my
listening rooms with an active loudspeaker system for a client in

Another project was an active loudspeaker system for “Tote on the
Turf” in Mumbai.

Today I and my partners do development work for many famous High End companies

So you can see that I have build some of the most expensive audio
systems in the world.

However I always wanted to create products, which most music lovers can afford.
I began my own Hi-Fi life with Sinclair, Dynaco and Linsley Hood DIY
amplifiers and Peerless and later Lowther horn loudspeaker.

Deveopling new Amphion loudspeakers was the first step, testing wether I could make
Euro 1000 to 2000 priced loudspeakers sound better.

The USD 475 Parasound ZDAC project started life as an USB DAC developed together
with Thomas Holm of HOLM Acoustics ApS.
Please see the excellent reviews elsewhere on this homepage.

Best wishes
Ole Lund Christensen
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