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Inter.View with Steen Falck Doessing, President and chief designer of SD Acoustics

by Lucio Cadeddu

[Italian version]

LC >
SD Acoustics is a new Hi-End firm, born, if memory serves me well, in 1983. May you tell us something about the idea behind SD Acoustics?
How and why did you decide to start making hi-end loudspeakers?

SD >
In 1983 SD Acoustics was established based on the doctrine that a new and different approach and the employment of advanced research and development would result in superior products.
Drawing on our innovative attitude to design and the experience gained from our work in the professional audio industry, we have developed a range of audiophile loudspeaker systems, each of which has been recognised by the international audio press as representing a significant step towards the perfect transducer.

LC >
I believe that a lot can still be done to improve hi-fi reproduction, especially with respect to loudspeakers design.
Which are, according to you, the most relevant aspects one should consider when designing a loudspeaker?

SD >
We believe that by firstly priorotising accurate transient response and precise soundstage placement we are able to create a perfect acoustic illusion in the domestic environment and secondly by our pioneering use of technologies such as Bi and Tri wiring, gravity cast inert cabinets (in fact 65 % lower Q-factor than MDF) and the use of extremely fast Ribbon transducers we are achieving a greater level of transparancy and correct phase relationship than that of a conventional system.

LC >
With this revival of low-powered tubes amplifiers a new wave of very-high sensibility loudspeakers has invaded the Hi-End market.
Which are the main drawbacks (if any) of this kind of a somewhat radical approach?

SD >
The main drawbacks of very high sensitivity loudspeakers are basically colouration introduced firstly by the need for a very powerful magnetic circuit and low moving mass which inevitably will result in both electrical and acoustical distortion of the phase relationship and secondly a powerfull motor system means overdamping of the fundamental resonance frequency (F0) which means that the driver must be hornloaded in order to produce reasonable levels of low frequency and this again introduces colouration.
In other words it introduces a different set of compromises than that of a lower sensitivity system.

LC >
May you explain us the pros and cons of the dynamic conventional speakers?
You use ribbon tweeters in some of your designs: which are, according to you, the pros of this kind of components?
Given the fact that normally the speakers of this kind have a "faster" response than their conventional counterparts, is it easy to MATCH them with standard dynamic units (woofers, mids...)?

SD >
A conventional transducer will by its nature have significantly higher levels of distortion than a Ribbon system introduced by the higher levels of break up model in the material.
A Ribbon system is by its nature much lower mass and therefore much "faster" and secondly as the motorforce is applied over its entire diaphragm it has a significantly lower level of breakup modes, indeed in a true ribbon this is ZERO whilst in an "isodynamic" Ribbon system such as the one we and most others use it is app. 2-3 % of the level of a conventional speaker.
In order to integrate a Ribbon tweeter to a conventional Bass/Midrange unit, this must be very fast too. Our 6" bass and Bass/Midrange unit has in fact an acceleration which is typically twice that of other similar units.

LC >
I believe that the 50% of the performance of a loudspeaker into a standard listening room depends on a correct placement.
There are several different approaches, we at TNT-Audio have tried to explain two of the most famous ones: the Wilson's method and the Cardas's one.
Which advices would you give to our readers to help them getting the best results from their loudspeakers?

SD >
In my opinion you are underestimating the importance of correct room placement. Each speaker designer has to input the effect of the room into the equation when designing a loudspeaker. In addition each speaker designer has his own personal levels of criteria which he must incorporate into the design.
Also, each and every listening room is different and will affect the sound in a different way. Just as speakers are a set of compromises which when applied in a correct way will recreate an acoustic illusion, the listening room has to part of this calculation in order for the entire system to balance not only in terms of tonal accuracy but also in terms of optimum phase.
SD Acoustics loudspeakers have been designed to perform at there optimum when placed at least 40 cms away from the rear wall and at least 50 cms away from the side walls. An experienced operator should be able to just look at and "feel" the ambience of a listening room and place the speakers in a good starting position from where there placement can be finetuned.
Often even very small differences in placement (I am talking about centimetres) can make all the difference.

LC >
A correct and realistic virtual soundstage is a MUST for a natural and musical reproduction of our favourite music.
The problem is that a realistic soundstage is HARD to get.
Which are the main aspects that influence this kind of performance?
And how can we try to improve soundstaging?

SD >
See the previous answers.

LC >
How much is a good and stiff cabinet relevant for a loudspeaker?
Which is your approach in cabinet designing?

SD >
A good and stiff cabinet is of vital importance to enable the drive units to perform at their optimum. It is better to have a very good cabinet with lesser drive units that to have an average cabinet with very good drive units.
SD Acoustics employs gravity cast PBM cabinets which are not only heavy and therefore provide a very solid fundamental platform for the mounting of the drive units but they also have up to 65% lower colouration (low acoustic Q = less resonances = lower colouration).
We therefore achieve a much better performance from the drive units in terms of transient response, phase relation and colouration which results in much more realistic soundstaging and precise imaging.

LC >
Which are your next projects? What do you think of the current trend of making HT-compatible loudspeakers?

SD >
At the moment we are working on a very High-End system well in excess of the SD1 Evolution. We have not decided when and where to launch this system but I can tell you that it will be a 4 cabinet system (completely separate floor standing bass enclosure and separate standing tall Mid/High enclosures).
The cost is planned to be twice that of the SD1E.

Courtesy Steen Falck Doessing for TNT.

Copyright © 1998 Lucio Cadeddu

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