What?Really rather good concrete-lined 3-way floor-standing loudspeakers
Why?The sound of music (but not the film of the same name...)
How?You know the feeling. You're listening to one of your favourite pieces of music. It's inspiring, uplifting, a tidal-wave of emotion that leaves you feeling drained. Or at least that's how you remember it, but your current hi-fi system is delivering only a shadow of the music's promise. Your equipment distracts you with colouration, tinny treble, uneven bass and poor imaging.
So, what do you do? You could look to your playback source - but modern CD players are unlikely to have any severe output quirks (especially Arcam ones). You could invest in a bigger and better amplifier, and indeed that's what most wisdom tends to suggest, that the amplifier is the key arbiter of audio fidelity. However, once examined, it becomes apparent that even the cheapest transistor amplifier is unlikely to be distorting your audio particularly much. By far the biggest gains come from concentrating on the speakers. Now, I'm not saying the amplifier is not important - it is, very much so. I am saying that the average pair of hi-fi speakers harbour far more acoustic gremlins than the average amplifier. Why is this?
Mainly, the answer is cost. That, and the inherent physics of moving suitably large amounts of air backwards and forwards very quickly in a controlled manner. As the physics aren't going to change any time soon, most manufacturers concentrate on cost. Interestingly, it's not the cost of exotic drivers that makes up the bulk of a loudspeaker's purchase price; a very large fraction of it is packaging and distribution costs. After all, they're big, heavy things, speakers. Or at least they were. There seems to be a trend towards smaller and smaller units, which I'm fairly sure is being driven more by cost than by absolute audio quality.
Now, I'm all in favour of clever design and packaging, if it improves the end product. It's just that of all the speakers available at the time I started thinking about this product (some time in 2000), none seemed to be emphasising audio quality above all else - everything took pains to explain the clever tricks used to get the best bass response out of a limited enclosure size. So, deliberately turning my back on received industry wisdom, I set out to design a simple, high-quality, three way loudspeaker.
One of the other design goals for this project was a speaker with very flat bass response; not just getting the bass down "as low as it will go", but doing so in a controlled manner, with no peaks or troughs in the response curve apart from a gentle rolloff below 20Hz. This led me to consider a sealed-box design (as opposed to ported), to eliminate any chance of a slow, booming bass. The sealed box has a number of advantages (phase alignment, perfect damping and gentle rolloff at the low end), coupled with one big disadvantage: a sealed box has to be significantly larger for a given f3 (3dB attentuation from the normal frequency response curve, thus "cut-off" frequency) when compared with a ported design.
This did not bother me.
The speakers, as designed, have an internal volume of around 80 litres, which is enough that the damping factor of the air in the box perfectly matches the Dynaudio bass drivers' requirements for low frequency response. There is only a 3 decibel attenuation at 20Hz, and a fairly smooth roll-off below that point. Of course, low, powerful bass would be useless without the rest of the frequency range, so care was taken that response should be as flat as possible all the way up to 25kHz (just for good measure - I'm pretty sure I can't hear anything that high-pitched!).
For the midrange, I chose a Scan-Speak 13M8636 Kevlar unit, which due to the lightness of the cone has very good transient response. Whilst its frequency range is not exceptionally wide, in a 3-way system this poses no problems. Past 2 kHz, a Dynaudio Revelator D-9200 soft-dome tweeter takes care of the treble. This is an exceptionally fine tweeter, capable of exquisite subtlety, and works superbly in this setup.
Having decided on such expensive drivers (none of the above are bargain-basement parts...), it was even more imperative that the boxes themselves should not distort or interfere with the sound. I was particularly concerned about the cabinets adding colouration to the music, which often occurs when the cabinet resonates during playback. To eliminate any resonances, several steps were taken:
- First of all, every driver was mounted to the baffle using neoprene gaskets. This ensured a good air-tight fit, but also (in conjunction with a complicated floating bolt arrangement) decoupled the drivers from the surface. This reduces the acoustic efficiency of the whole system, but also reduces distorted acoustic radiation quite significantly.
- The cabinets themselves were designed to offer a huge acoustic impedance mismatch to any sound being reflected around inside the chambers. The best way to do this was to make the cabinet walls as massive as possible, therefore the 18mm MDF panels were reinforced throughout by a 12mm layer of concrete, in addition to a large steel plate in the base.
- Every interior cabinet surface was covered with a polymer damping solution to reduce standing waves and unwanted reflections back at the driver
Having assembled all of the above, it made no sense to skimp on the electrical side of things, so the units are wired throughout with heavy guage silver-plated oxygen-free copper wire, coupled to independent heavy-duty XLR connectors. This allows for active amplification in future, though presently they are "only" bi-amped.
To finish them off, the speakers were veneered with black walnut, and French polished to a reasonable shine.
Sadly, I have no independent review of their qualities, but to my ear, they are easily the best speaker I've heard for under six thousand pounds. They have a couple of quirks, largely related to the crossovers - which are still mounted in a shoebox. Given the time, I will be perfecting a three-way active crossover based around an Analog Devices TigerSHARC DSP, which should eliminate even these small foibles. I'm not sure anybody else will notice, though - most just sit there dribbling at the stunningly beautiful music rolling over them...