Introduction - DIY-loudspeakers.com

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THE DESIGN FRAMEWORK

A design procedure must include several steps, obey to several rules but have only one orientation, one main principle. Discussion fora have presented multiple opinions on what is the best acoustical behaviour of a high fidelity speaker system. Almost always these opinions have nothing in common and contradict each other. We can talk for hours repeating the various speaker design 'movements' of the last decades. Our approach is compatible to all these and in that sense unique.

One principle is engaged to our design protocol : A designer and the associated process must only be able to predict and control the objective acoustical properties of a high fidelity speaker so that they reach design targets defined a-priori.

In simple words our philosophy is not to force this site's users, members or plain visitors to accept the superiority of our design targets. These acoustical targets are almost always a matter of personal taste. For many amateurs and engineers it can be the result of experience.

-So what is our design philosophy or principle as stated above ?

A design procedure must only give us the ability to control the speaker's behaviour in an absolute way that will always make the latter reach our initial design targets. In this site we will only give examples of such targets, not question their origin, integrity or consistency.

-Are there any rules that must be discussed before going on ?

Yes there are:

A HiFi speaker has a BOM (bill of materials) and an associated cost.This cost must always be kept in the designer's mind because it outlines the speaker's 'category'.
Musical content expected to be fed to a HiFi speaker may or may not influence our design targets. Sometimes a prior knowledge of the sort of music that a speaker will have to handle most of the time, will simplify our design targets a lot.
The properties of the listening environment in which a HiFi speaker is expected to operate are critical for our design targets. Every speaker system radiates sound waves to space directions in a different way. Its directivity pattern decides whether the speaker emits significant part of sound energy towards the floor or ceiling to be reflected. If this part of sound energy is relatively small the listener will perceive a relatively higher sound clarity.
Speaker systems designed for entirely different listening spaces can hardly be compared to each other. A slim and tall floor-standing speaker bearing four 4-inch woofers can produce an adequate and balanced bass in a very small teenager room. Its equivalent, a 30-liters speaker with an 8-inch woofer, mounted on a stand, would be unsuitable for the same room. However the power handling capacity of the first scenario might dissapoint us.

A speaker system does not create music out of nothing. It needs to be connected to a power amplifier. As power levels increase in the listening space the acoustical result is influenced by space reflectivity, amplifier quality and loudspeaker driver distortion.

A very 'live' (reflective) listening space can add so much sound harshness to the ..dark side of our speaker system that can send all our efforts to the recycle-bin instantly.
Loudspeaker driver distortion is usually an issue for woofers (rarely for tweeters or midranges driven by proper crossover filters). To my knowledge low-cost drivers can not handle high levels of electric power properly.
A power amplifier is not a simple electric device. It is technically designed to drive 8 Ohm resistors, not speakers. It has been clearly proved that the complex nature of the impedance of a speaker acting as a load to the output stages of a power amplifier, drives them ..crazy. High power levels need quality power amps. Yet we can take certain measures within our design procedure to smooth this complex nature for the impedance of our speaker system. This complex impedance compensation scheme adds extra components and cost to our design.

-Which are the steps of the design procedure for a high fidelity speaker system?

Not all steps can be presented at once. There must be over one hundred of them so the reader will lose track of the overall idea. At the beginning we need to define a framework. Each part of this design framework will group a family of steps.