Mr. Ray Purchase wonders: Speaker Design – Is there much to it? (Part 7)

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The Result, and Interpretation

Obviously I don't expect to convince you that my speakers are 'high end', but they are! All types of recording sound better than I have heard before (outside, presumably, of the active Backes and Mullers mentioned earlier!), but where the system excels in particular is in playing back uncompressed large scale classical recordings, which are simply astounding.

I think that the key to this is that the system is 'straight' and that every component, low cost though it is, is not being highly stressed. A virtuous circle has been set up:

DSP and measurement-based crossovers are so simple and accurate that there is no temptation to stretch the full audio spectrum over just two drivers.

Using three drivers or more allows the use of a large, unstressed woofer that can move a lot of air, and can go very low; there is no need to stretch the bass response by using a port with its attendant time domain problems and unnaturally-sharp roll off below resonance. The mid range isn't riding on huge bass displacements of the cone with attendant intermodulation effects. The woofer and tweeter don't have to reach out of their comfort zones, which reduces beaming (an unavoidable consequence of the finite diameter of a speaker cone which worsens at higher frequencies), and avoids the necessity of inhabiting the cone breakup regions. Surely, when used within their capabilities, cheaper drivers are going to behave very similarly to their high end brethren.

Direct amplification of each driver, rather than the passive crossover alternative, saves on wasted amp power, reduces stress on the amp and improves cone control. Dividing the amplification duties over three narrow bandwidths further reduces the stress on those amplifiers. Any distortion in one of the three sections does not contaminate the remaining sections. Three modestly-sized amplifiers provide output power equivalent to a massive power amplifier of the sort that would be needed for conventional passive speakers.

The system is so 'eager', and the sound so rich and clear, the bass so deep, that the listener isn't tempted to turn the volume up simply to compensate for a perceived lack of oomph, thereby exacerbating problems. With conventional systems it seems to me, you turn up the volume until the sound becomes too unpleasant, then back off a little. With my speakers it is tempting to turn up the volume to realistic levels simply because you can!

Because the components are not being stressed they don't need to be super-components, and so there is no incentive to economise on the number of drivers etc.

The system sounds good even though the drivers are practically the cheapest available and the enclosures are standard 'monkey coffins'. The interpretation I put on it is that without any one of the most important features (three way, large woofer, sealed box, active amplification, DSP correction) the system would fall down. Given this, or the seemingly-unquestioned industry standard passive solution, we might be tempted to think that any problems must be down to (relatively) spurious factors like the wrong types of wire, low component price, or cabinet resonances, but I think we would be wrong. I think we could make large and arbitrary changes with my system, but as long as we kept to the 'core principles' we could make it work well.

Another factor in this system's favour is that it can be modified for room acoustics and placement within the room. With conventional passive speakers and a reluctance to use DSP, the user is stuck without any option to make subtle adjustments such as baffle step correction.

Continues tomorrow

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