Thomas' story of his loudspeaker system:
My inspiration to build a loudspeaker system this way, was by a member called AH on a German Hi-Fi Forum,
who talked about the importance of dissipation, diffuse field, HRTF and so on ( I heard about this things
for the first time ).
So my target for my 3rd DIY loudspeaker was a uniform directivity and because it is so easy to get a linear
on-axis frequency response with a digital crossovers
I decided to aim for a cardioid dissipation in the mid to reach a uniform directivity from about 300 Hz to 10kHz.
(below 300 Hz the ear can not very good differentiate between direct and indirect sound, about 10kHz happens
nothing important in music for me. In my opinion, it's important to reach a constant sound level curve on the
listening position without to do major changes in the linear free field curve. My target was a difference between
free-field measurement and listening position measurements, with the same EQ, from about +/- 2 db.
There is a German Firma called MEG Geithain which build loudspeaker systems like MEG RL 901K , RL 800 k with
strong considerations about even dissipation. These loudspeakers are often used in German broadcasting facilities.
The RL 800K uses an interesting principle to reach cardioid dissipation by using the rear sound of the mid speaker
with a mechanic delay element to get the cardioid dissipation.
After a long time of considerations and research in the internet, I decided to build this principle with 2 PA
midrange drivers from PHL and the DCN 28 (the only digital crossover I know of with 8 output channels).
This setup makes it possible to influence all parameter like frequency response, delay, x-over points on the
2 mid speaker to reach the dissipation I want.
Another good reason for choosing DCN28 is the very convenient delayed 4 trigger outputs that control my
2 power amplifiers RMB1066.
Thomas showing and explaning me (Robert) how the system works
Click the above picture for larger and more detailed image
Plot of the directivity pattern of the mid-range
Frequency response at both listening position and free field
Total System mk.I:
Now my complete setup for listening music consists of only
NAS server -> Squeezebox Touch -> DCN 28 -> Power Amplifiers -> Loudspeakers.
With a Logitech Harmony remote I can start listen music by just 1 click (very high WAF).
The SqueezeBox Touch wakes up the NAS server and the DCN 28 triggers the Rotel RMB1066 Power Amplifiers