One way systems are very good for many reasons. But there are in my opinion no drivers that do the job very good. Also I am a real speedfreak, fast transients are very important to me.

I played with Bert Doppenbergs Oris 150 system loaded with Lowther PM2A's before, but had the chance to try some Altec 291-16A compressiondrivers on the Altec 1505B (3*5) and the 803B (2*4) multicellular horns. I really did like the speed, but the sound was not good to me. The sound was a bit horny and harsh. The horny sound probably comes from the square horn mouths, like I had in the first square Oris version of this system. So I decided to try the round Oris 103 horn (The Oris 150 I had before was already much better then the square horn before). Sound was really clean now, but still a bit harsh.

So I designed a correction network for this speaker. It is not really how I like to do things, in principle I think you should not make a mistake and then correct it (like using feedback, etc). However, I think there is simply no loudspeaker that can play as good as this compression driver, so I had to. Again it all is about making the right compromises... I also enlarged the backchamber of the driver to about 0.8 liter. This resulted in a very nice frequency range of 300 Hz to 10 kHz. I think this range is very acceptable, since most of the music is made in this part of the spectrum. I would prefer getting it down to 150Hz, but that simply is not possible with this driver.

Sensitivity of this system is 112 dB. I have found some Altec 288-16K drivers and will try them soon also. I have measured them already and designed a good LCR correction for them also, just waiting for the parts. Even better will be using the 100% aluminium membranes of the 288 in the Alnico magnet of the 291! Unfortunately time is not on my side, but it will play someday!

Because I want to play the whole spectrum, I use a bass driver below and a supertweeter on top to complete the whole thing. The bass drivers is a Altec 515-16GHP driver in an original (type unknow to me) altec horn enclosure. I had to adjust the bassreflex ports to get a controlled bass, as always the damping of the bassports was far to low, resulting in fluffy bass.. Also I did a lot of improvement on the damping of the enclosure. The Altec 515 is one of the best drivers around, is has a big magnet and a very light cone. The GHP (HP=high power) is a very rare and even improved version of this driver. It has a larger magnet and can handle higher power than a normal 515 because of the special shaped poleplates. Sensitivity is 101 dB! Sound is incredible fast and clean!

To add the last octave and also to get the sound loose and fast at the top, I added a Fostex FT66H ringradiator supertweeter. This tweeter is on of the finest made by Fostex (I think). It has a very great and smooth frequency range, and can handle good power with high sensistivoty (100 dB). It is almost impossible to hear the tweeters, but when they play the sound is much more easy and sparkling and also the sweetspot is much bigger. So they are a very good extension of the system. I will try later to let them play from 4kHz orso, maybe that will even improve the system, because the sound of all the speakers has the same disperse characteritics then... More about that later.

It is very important for the sound that all speakers are time aligned and have the same radiation pattern. Music is all about tones and harmonics, it is very hard they all arrive the ear at once and in the same way. This is why the drivers are time algined (that's why the supertweeters are placed at the back of the bassspeakers), and all speakers are frontloaded.

The sound of this system is very great. Dynamics are very great, there is simply no other system (apart from alike systems) that will do the same. I think this speed it has is necessary, because now a string sounds like a string and a piano sounds like a piano. Music is all about transients and this system handles that like no other. Because all drivers play at only maximum of less than 10% (and then I play 110 dBa in my listening room! Oops my ears...) of the capabilities the membranes almost do not move (very lineair!) and there is very much headroom. Voices never break up, they are played very very very easy. Bass is deep and controlled, highs are easy and relaxed.

The system is used active, using my MachMat Kapittel II SE AV302B-SL tube amp for the Altec/Oris combination, with a bandwith limited to 300 Hz - 10 kHz, filtered electrically second order. The bass frequencies (<300 Hz) are filtered actively with the MachMat Rubricator adjustable tube active filter. The supertweeter is filtered active wit the MachMat Superamp