----- Experience in your own room the magical nature of stereo sound -----

 

 

What's new

 

LX - Store

 

BLACKLIST

 

Conversations
with Fitz

 

OPLUG
Forum

 

Basics

The Magic in 2-Channel Sound

Issues in speaker
design

Dipole models

Active filters

Amplifiers etc

Microphone

FAQ's

Loudspeakers

Crossovers

Room acoustics

Stereo Recording and Rendering

Audio production

Conclusions

 

Projects

Your own desig

LXmini

LXmini+2

LXstudio

LX521.4

LX521
reference

ORION
challenge

ORION-3.4

PLUTO-2.1

WATSON-SEL

PLUTO+
subwoofer

THOR
subwoofer

PHOENIX
dipole speaker

Three-Box active
system (1978)

Reference
earphones

Surround
sound

Loudspeaker
& Room

 

Resources

Publications

Sound recordings

Links

Other designs

My current setup

About me

Site map

 

HOME

 

------------------
Digital Photo
Processes

 

------------------
The
Sea Ranch

 

------------------
My Daughter
the Jeweler

 

What's new

 

LX - Store

 

Conversations
with Fitz

 

OPLUG
Forum

 

 

 

| Build-Your-Own | Main Panel | Dipole Woofer | Crossover/EQ | Supplies |
| System Test | Design Models |
Prototypes | Active Filters | Surround | FAQ |

 

Dipole prototypes

 

G - Public Address column loudspeaker 

This PA loudspeaker was my first dipole design. I had to provide intelligible sound to a large audience in an indoor basketball court for a satellite down-link. It was for a six nation Beyond War world peace event with video presentations, speeches and folkloric music. The single speaker column stood 2' from the edge and to the right of the large video projection screen on a makeshift stage. To the right of the column was a podium with microphone for local speeches. I wanted both screen and microphone to be located in the dipole null for reduced acoustic feedback and minimal acoustic interference with the screen. It all worked to great satisfaction.

I had built the column in two sections so I could fit it into my car. For use the sections are stacked, clamped together and screwed to a base plate. So when I later set up the two sections as stereo speakers in my living room, I was surprised by their sound. Something in it reminded me of the Quad ESL 63 and I wondered what might I might hear if I had a properly designed dipole using conventional piston drivers. The rest is history, as they say. The Line source was occasionally used later in Stanford University Chapel to enhance the clarity of voice and guitar in a highly reverberant environment.

The terminal impedance and the driver wiring diagram are shown below. The four innermost drivers of the column cover the full frequency range. The top and bottom four drivers are rolled off at higher frequencies by a 25 uF non-polar capacitor. I seem to remember that I used a 250 W/ch stereo amplifier to power the two column sections. They can handle more power though.

The column needs a significant amount of equalization. The circuit diagram below provides the essential response.  

 

equalizer-s.png (184911 bytes)  Original circuit diagram. It includes additional stuff, which was needed for the satellite down-link program. 

CA17RCX-1s.png (180029 bytes)  SEAS driver data sheet-1

CA17RCX-2s.png (240357 bytes)  SEAS driver data sheet-2. 

If you can no longer find the original drivers, then use something equivalent.

 

Have fun building these PA speakers. You may want to add subwoofers, like Thor, if your application is for dynamic music material.

Surprise yourself and your audience!

 

Line array dipole for a Concert Hall sound system

| Prototypes |

 

 

 

 

What you hear is not the air pressure variation in itself 
but what has drawn your attention
in the streams of superimposed air pressure variations 
at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

___________________________________________________________
Last revised: 02/15/2023   -  © 1999-2019 LINKWITZ LAB, All Rights Reserved