The following is based on a posting of mine DiyAudio.com from March 25^th 2008

I built my first speaker at the age of 16 and i was never fully satisfied with my results since then. Even when i became more skilled, and learned more about acoustics, electronics, mechanics, physiology of the hearing system, human perception in general...

What is the search about ?

My view has changed a lot in the last years. I always anticipated, that minimizing "errors" in a technical way does not lead to good results. We have to consider the qualities on which our perceptive system is based. Today i think that trying to build good systems is to explore our perception of things. It makes me wondering every time, when I listen to a certain system, which gives rather good performance subjectively while performing poor from the measurement point of view. Some systems recognized as being “good” by a wide range of listeners suffer from obvious technical drawbacks like

• patchy amplitude response vs. frequency
• high non linear distortion in a certain frequency range

and so on.

Those imperfect examples are often more instructional, than the exploration of a system, which is "known" to be unobtrusive by the measurement point of view. This is because it points me to what is important and what is not.

I try to offer you my current, very subjective and incomplete list of important an unimportant traits, maybe as a point of further discussion. I am sure that your "lists" will differ, but maybe there is some overlap

• smooth amplitude versus frequency response at a fixed point in the listening room is

NOT VERY IMPORTANT

• smooth amplitude response outside the critical bandwidth ( say broadband telephony 0,2 … 7 Khz bandwidth) at a fixed point in the listening room is even

LESS IMPORTANT

• large bandwidth is

IMPORTANT

• balanced dispersion of energy over the entire frequency range in the listening room as a whole is

IMPORTANT

• controlled directivity which means "no sharp discontinuities in horizontal and vertical radiation angle vs. frequency" is

VERY IMPORTANT

• decay time with pink noise above the critical bandwidth is

NOT VERY IMPORTANT

• decay time with pink noise at very low frequencies is

NOT VERY IMPORTANT

• decay time with pink noise from mid-bass to the presence range is

VERY IMPORTANT

• invariance of all parameters considered important against different power levels - especially against very low power levels – which are needed for the perception of subtle dynamic changes is

VERY IMPORTANT

Every distinct pattern of “misbehaviour” of the reproduction chain like

• a resonance pattern or
• a pattern of sharp directivity changes vs. frequency or
• a distortion pattern occuring at certain levels of power

makes the transducing device easily identifyable to our hearing system and hampers it in its attempt to compensate "minor flaws" (which are allowed).

To cover the important attributes mentioned above, a line array was chosen which radiates from an open baffle as a dipole. This provides adequate directivity in both planes and the absence of cavity or length resonances, which occur necessarily in any enclosure, even when damping varies between box designs.

To keep the array from beaming at mid to high frequencies, the lower drivers are shaded with increasing frequency. In this way the array effectively gets shorter at higher frequencies.

The drivers used provide very good invariance of behaviour at different power levels especially low nonlinear distortion.

The frequency range from 30Hz to 70Hz is covered by a special dipole mono sub, thereby preventing the fullrange drivers from excessive excursion at low frequencies.