Bert Doppenberg's 
Date of "Visit":
30 August 1999

7 February 2000

the system

Unison 845's

Oris 150 Reference


e-mail to:
Bert Doppenberg

Bert's web page:

I started with the hobby about twenty years ago due the lack of good sounding systems for a reasonable budget. I still believe that for a given budget, the performance of most systems suck! This is the main reason why I developed my own system which gives me most pleasure each day. The problem of most systems (no matter how much they cost!) is the lack of the capability to reproduce the emotion and the right atmosphere at the time of the recording. The main reason for this is the used complexity of electronics and the crossovers needed in multi-way systems.

The more electronics and the more drivers in loudspeakers (with there crossovers), the less spherical stage, less emotion, less detail, etc.

Therefore I use wide-band drivers (no crossovers!) and SE-tube amplifiers for the most critical part and a huge sub horn (the whole width below the red front horns) to enjoy the deepest frequencies without distortion and the lack of control.

I am lucky to have enough space around my house and build my own studio (8.5 x 4.1 m.) to separate audio from the family. WAF is no issue here and also the only way to listen to music at any time I like!

I listen to all kinds of music. Live recordings give me most pleasure! 20% classical, 35% Jazz and 45% rock or pop music (no hard rock anymore, I am getting too old for that!). The CD's I am using for evaluation purposes are the followings:

  • Jazz - (Verve 837933-2) Shirley Horn "Close Enough For You"
  • Jazz - (Windham Hill Records WD-0124) Tuck Andress "Reckless Precision"
  • Choir - (Proprius PRCD 7762) "Cantate Domino"
  • Classic - (Reference Recordings RR-70CD) Stravinsky Minnesota Orchestra "Firebird Suite"
  • Percussion - (BIS CD-232) The Kraumata Percussion Ensemble
  • Pop - (Columbia UCD 2-537 double CD) Pink Floyd "The Wall"
  • Pop - (Antilles 533 799-2) Mari Boine "Callin" live
  • Organ - (Dorian DOR-90117) Modest Mussorgsky "Pictures At An Exhibition"

System's Components
Turntable: None ( I am much to lazy )
CD Transport: Philips CDM12 (highly modified)
D/A Converter: Audio Synthesis DAX-2 (HDCD)
Line Preamp: Array Obsydian, passive remote controlled
Power Amp: Unison Research Smart 845 (highly modified), Rotel RB-990BX (for the subs)
Speakers: Oris 150 Reference (the Oris 150 front horn with horn loaded sub)
Interconnects: Deskadel silver 
Speaker Cables:  Deskadel silver 
Accessories: Comfortable chair

Bert's comments about his System:

AA: "Bert, how would you describe your system's sound?"
BD: "The system doesn't sound at all. It only reproduces the signal in the right proportions, size and depth. The very quick, detailed, precise and dynamic sound gives one the feeling of being present at the performance, first row!"
AA: "Do you think there is room for improvement?"
BD: "No, I am fully satisfied with the system."
AA: "Have you got plans for upgrading?"
BD: "With a new standard in the Digital reproduction and recording (higher resolution), yes."

Array Quartz

AudioFanatics WE300B


Bert and Adnan inside the bass horns

Re-Visit Notes (7 February 2000)

I was not planning to upgrade my system. This doesn't mean that I do not open my eyes and ears for nice additional tweaks, just for fun. My system was built out of all kind of different brands and looks, the passive pre-amplifier is very good looking, but the Rotel amplifier not (sounded very controlled though!). I saved some money and wanted to have the Array Quartz SS amplifier for the looks but the sound should be okay (my main demand) and lend one for audition. It turned out that this amplifier had even more control over my sub then the Rotel. So far, the amp never left!

Another upgrade was the main power filter incl. cables. I was looking for one a long time but they all didn't work properly, loosing dynamics and sounding dull. After removing those filters the live feeling was back again! The last try with the Kemp Elektroniks filter (spelled right!) was another story, the opposite! It turned out that it sounded if I had more dynamics with the filter connected.

If this isn't enough, the third upgrade (for the time being) is a new amplifier for the Oris 150 front horns. I have a very beautiful 300B SE amp in consignment using Western Electrics 300B tubes and all kind of other audiophile sounding parts. This big amp (75Kg) makes the sound even more complete which is hard to describe in words...

If you are in Holland, just call or e-mail me for an appointment to judge using your own ears!

All items are the same except for:
power amps:
  • deJongSystems Audiofanatics WE300B for the Oris 150 reference horns.
  • Array "Quartz S" 120Mhz Solid State amplifier for the horn loaded sub 
Accesories: Kemp Elektroniks Mains Power filter


Adnan Arduman comments:
Last week I was in Holland and accepted the kind invitation of Bert. It is an hour drive from Amsterdam, and a very pleasant one if the weather is good!

Bert is so lucky to have a totally private house of his own, entirely dedicated to his system. The bass horns happen to be the integral part of the room occupying nearly one third of it. In order to make you feel the size and depth of these bass horns Bert and I occupied each of the channels. See the bottom picture taken by my wife (Bert: left channel, me: right channel).

We listened to different CD's of Bert ranging from classical orchestra to rock. I was positively impressed by the sound in general. There was no compression at any volume, bass slam was stunning and the high frequencies were very detailed and present. 

At one point I suggested to elevate the speaker cables from the floor (on the bottom picture you can see two PVC pipes placed vertically near the right speaker, they were just placed for this experience). We both could hear the increased transparency and inner detail as if one layer of veil is lifted. A very worthwhile tweak, totally free of charge and which definitely works. It is now up to Bert to find a permanent solution to implement this tweak to his system.

It was great to meet Bert and spend two enjoyable hours full of music and Hi-Fi. Absolutely recommended!