4. SETUP

HOME
UP
1. INTRODUCTION
2. HORNS AND MIDS
3. WOOFERS
4. SETUP
5. SUBWOOFERS
6. RESULTS
7. PARTS
8. SUBWOOFER NOTES
9. ADDENDA


 

 


SETTING UP THE SYSTEM
 

This can be tricky. I used a TEF analyzer and a $40,000 1/24th-octave Brel & Kjr real-time analyzer and intensity probe set of phase-matched microphones (another $14,000). First, I did energy-time measurements to set the delays in the amplifier. This proved to be difficult, since I had to take distance ranging measurements of each driver separately to make sure I was looking at arrival times from the intended measurement object. After I got the delays set, I checked frequency response the best I could in the space available, then resorted to the real-time analyzer. Be aware that the frequency responses you get with these two methods are very different because TEF windows its measurements to try to exclude reflections and examine only direct sound from the source, while real-time analysis includes all returning room energy information along with that from the speaker. I like a balance of both measurement methods, because one lets you fine tune the energy output of the speaker, and the other lets you adjust large trends like the general "too-bright" high end you will likely notice if you try to obtain flat output to 20 kHz from the direct-sound readings of a truly power-flat or "constant-directivity" horn. Such horns produce more high frequency energy in the first place because they distribute the energy over a larger angle, that is to say, if one equalizes such a horn for flat response, then more high frequency energy will be pumped into the listening space than would be the case for other types of horns. Most people are not used to listening to power-flat top-end, and will find it too brassy. Only minimal-miked big-band recordings will sound right with the system adjusted this way. For your playback system head end, I recommend that you use an extremely low-noise preamp with simple Baxendall type "tone controls." The bass and treble turnover frequencies are a matter of taste, but 100 Hz and 10 kHz or 200 Hz and 5 kHz seems to work well to adjust this system to music on recordings. To my ear, parametric equalization is less pleasing and is certainly prone to putting more phase aberrations in more audible frequency ranges than are simple tone controls. One-third octave "graphic" equalizers are completely useless for high fidelity use and one-octave units are even worse-avoid these. They introduce horrendous phase shift problems of their own, and if not properly analyzed with the system they are driving, will virtually always degrade performance.

Begin adjusting with the amp master gains set low, and turn the preamp all the way up. Slowly advance the amp gains until you can achieve proper balance and slightly louder than necessary output. This will ensure that you will have the least possible amplifier hiss from the speakers. Amplifier hiss is a phenomenon that rarely troubles owners of low-efficiency speakers, but these monsters are efficient enough to make the transistor junction noise of poorly designed amplifiers quite audible.

If any of you reading this decide to build this system, it will cost around $10,000 including amps and all. If you get that serious, if you are rich and adventurous and don't care what stereo salesmen think, you are the type of person who would really enjoy this system.

1997 Drew Daniels

 

 

 

BACK NEXT