My Oris Project

There are many us who thanks to Bert and his inventiveness enjoy this fantastic design. I don’t want to repeat what others have said and what a wonderful musical experience these speakers provide. Even I am convinced that this is really the most detailed system I have ever heard. What I want to do is to describe my arduous way to my own sound.

It all started with Lowther and my being their dealer for the Czech Republic. Back then I was looking for sensitive speakers for my favourite tube amplifier. It was my favourite because it sounded wonderful in the mid-range, but it wasn’t able to supply my amp-hungry speakers of a well-known brand I won’t name with deep vibes. Sensitive Lowthers supplied the sound I had been looking for but at the same time it revealed other shortcomings of my set-up. With these speakers you can clearly hear the differences in the quality of connected components, which clearly speaks in disfavour of semiconductors. This eliminated one direction and pointed the way which was more demanding, but also more beautiful because of that.

Helund horn + Bel CantoOver time I tried different designs of backloaded Lowther horns and the Swedish Hedlund horn also had its turn. In my opinion it is one of the most successful DIY backloaded horns ever designed. With regard to the bottom cut-off frequency it has a horn of reasonable length which doesn’t overload the driver and it can still easily move the volume of air without loosing its dynamic. But it requires the use of at least the Lowther DX3 or stronger.

Time to try the Oris

Oris 150 + K hornI was really looking forward to that. First, I built an Oris150 AER/PM4A. It played together with a K-horn which had a hand-made 15’ bass driver with a strong Alnico magnet. In the beginning I had to get used to it. The Orises were a bit imposing, but it was the first time I used a separate bass with a wide-band system. I didn’t have any experience with it, all my sources were only from the web and I wanted the best solution. Problems occurred with phasing at the crossover frequency and the Orises were immediately moved to the only place where they were useful, that is the closest to the K-horns, or better to say straight atop them but, unfortunately, also into the corners of the room. Why unfortunately? While the K-horns use their design and the corners of the room to maximize their bass, the Orises and the corners don’t seem to be a good match. The Oris is too good a design to be in just one specific place. In the corner the Oris doesn’t play well, it can’t be set and adjusted, and on top of that, due to the length of the horn of the K-horn, there is a serious problem with phasing. In other words, the Oris and K-horn aren’t a good match.

Oris 200 + OnkenIt was time for the Oken and Vifa, by the way also a very successful bass design. I tried comparing it with all sorts of classic commercial subwoofers and it always came out a winner. With these two, the phasing is almost perfect and unless you mess up the placement in the room, it is nearly ideal. Although the axis of the Vifa driver is forward of the driver in the Oris, the bass filter of the Vifa compensates the time delay – theoretically. The result is very good and the system is easy to adjust and has minimal requirements on the room.

On the other hand, that bass was not satisfactory. It clearly lagged behind the Oris and couldn’t match its detailed sound. I really didn’t like the diaphragm with rubber surround, which negatively affected the resulting sound characteristics. I expect bass to be well defined and to have acoustic pressure such as musical instruments with a large baffle area have.

So it had to be a bass horn which could stand anywhere in the room, one that was shorter and opened up faster. The choice was Klipsch again, this time it was the La Scala. Yes, that was a true bass. Even though the phasing isn’t ideal, it integrates well with the Oris, it is fast and it doesn’t “bat around.” By adding “ears” the bass went down a few Hz and became more monumental.

Then I noticed one thing. With each improvement the differences in the quality of recordings became more pronounced and digital sound started to “thin out.” I could also more clearly hear any problems caused by the rest of the equipment.Acousta 115 + Lowther EX4

Note that I haven’t mentioned the differences in sound of Lowther and AER drivers yet. I can feel sparks flying between these two manufacturers. Not long ago I built an amplifier with a 300B for one customer. His wish was to use the best components on the market if possible. The amplifier was simple and didn’t have overabundance of power. I tested it with my Acousta 115 driven by a Lowther DX4. The first sounds just took my breath away. Great control, speed and dynamic with a completely charismatic sound of the Lowthers made me listen again and again to those beautiful old Acoustas, which I like best despite their imperfect retro design.

From experience I know that people who from whatever reason don’t like Lowthers and then listen to AERs shake their head in disbelieve and stare at this masterpiece driver whose fluid performance, clarity of tones and frequency range are unbelievable. On the other hand those who have listened to Lowthers at home for a while would never trade their darlings for AERs, supposedly they would loose something – and I know what it is and I perfectly understand. I even think I figured it out. The charismatic performance of Lowthers helps (in a positive way) to mask the imperfections caused by the source of the signal whether it is because of the low resolution signal technology on part of the hardware or severe errors made during the recording on part of the software. That goes for both CDs and almost all new vinyls.

Now I’ll try to describe my complete apparatus:

I don’t use a CD player. I play the digital format from an IBM notebook; DIY USB/SPDIF DAC – DIY TDA1541, 6C45P, anode choke, 5Y3, ASC; RIAA – DIY 2x ECC88, 6C45P, anode choke, 5Y3, ASC, Black Gate; Amp. – DIY 6C45P, anode choke, 842, 5U4GB, Black Gate; Bas Amp. – OTL A class. 6N6P, parallel 6C33C, cathode choke; Oris150/MD3, 1,5mm silver hard core; La Scala/AK15, 2,5mm silver hard core.

  Oris 150 SE - Horn Studio Oris 150 SE - Horn Studio  

The Oris 150: The back part is rubber-coated, that increased its weight and lowered the resonant frequency, some damping material was added and finally the entire back part was covered in leather. It makes quite a bit of difference when you tap on this modified horn and on the original one. The 1.5 mm silver hard core cables are soldered directly to the MD3 terminal and then lead straight to the amplifier.

The design of the La Scala is all made from birch plywood and the mouth of the pressure chamber is tapered gradually. Adding “ears” to the original design lowered the bottom cut-off frequency, but most importantly it became more monumental. The 2.5 mm hard core silver cables are soldered directly to the terminals of a hand-made 15’ bass driver with a strong Alnico magnet.

Horn Studio

The system of Oris + La Scala plays wonderfully in my studio (bass resonators in the corners, vibrating panels on the walls), but from experience I know that in rooms which are not a least bit bass-dampened (at exhibitions) this horn bass doesn’t sound good. The reverberation at low frequencies goes up and down, left and right and completely overwhelms the other frequencies. For this reason I have a different system on hand. It is an Onken BD-Design with a special custom-made 10’ bass driver with a diaphragm with paper surround. A bass driver like this has a wonderful, tight bass without a rubber aftertaste.OTL SE 6C33C

All connected apparatus use tube SE, including the bass amplifier, which is unique in its OTL SE 6C33C tube design.

I hope nobody got bored.

Jan Dvorak

Please don’t write to me. I don’t speak English and I have to have everything translated. Thanks.

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