Surround replay systems

Parts List:R1-2-7-8-12-13-18-19-20=47Kohm
R3-4-5-6-21-22-34-35=10Kohm
R9-10-11-14-15-16-17=15Kohm
R=23-24-25-33-36=100ohm
R26-27-28-31-32=100Kohm
R29-30=5.6Kohm
C1-8=47uF 25V
C2-7-9-14-23=47nF 100V
C3-6=1uF 100V
C4-5-10=33pF 100V C11-12-15=10uF 25V
C13=82nF
C16=18pF 100V
C17=100pF mini adjustable capacitor
C18=2.2nF
C19=4.7uF 25V
C20=100nF 100V
C21=10nF
C22=180pF
C24=150nF RV1-RV2=2X10Kohm Log. pot.
RV3-4=10K Log pot.
D1=1N4148
IC1-6=TL072
IC2-3=TL074
IC4=MN3101
IC5=MN3004
JI…..J6=RCA female jack


Surround sound encompasses a range of techniques for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and presents a fixed or forward perspective of the sound field to the listener at this location. There are other non surround based formats. The three-dimensional (3D) sphere of human hearing can be virtually achieved with audio channels that surround the listener. To that end, the multichannel surround sound application encircles the audience with surround channels (left-surround, right-surround, back-surround), as opposed to "screen channels" (center, [front] left, and [front] right), i.e. ca. 360° horizontal plane (2D).

Surround sound is created in several ways. The first and simplest method is using a surround sound recording microphone technique, and/or mixing-in surround sound for playback on an audio system using speakers encircling the listener to play audio from different directions. A second approach is processing the audio with psychoacoustic sound localization methods to simulate a two-dimensional (2-D) sound field with headphones. A third approach, based on Huygens' principle, attempts reconstructing the recorded sound field wave fronts within the listening space; an "audio hologram" form. One form, wave field synthesis (WFS), produces a sound field with an even error field over the entire area. Commercial WFS systems, currently marketed by companies sonic emotion and Iosono, require many loudspeakers and significant computing power.

The Ambisonics form, also based on Huygens' principle, gives an exact sound reconstruction at the central point; less accurate away from center point. There are many free and commercial software available for Ambisonics, which dominates most of the consumer market, especially musicians using electronic and computer music. Moreover, Ambisonics products are the standard in surround sound hardware sold by Meridian Audio, Ltd. In its simplest form, Ambisonics consumes few resources, however this is not true for recent developments, such as Near Field Compensated Higher Order Ambisonics.

Surround replay systems may make use of bass management, the fundamental principle of which is that bass content in the incoming signal, irrespective of channel, should be directed only to loudspeakers capable of handling it, whether the latter are the main system loudspeakers or one or more special low-frequency speakers called subwoofers.

There is a notation difference before and after the bass management system. Before the bass management system there is a Low Frequency Effects (LFE) channel. After the bass management system there is a subwoofer signal. A common misunderstanding is the belief that the LFE channel is the "subwoofer channel". The bass management system may direct bass to one or more subwoofers (if present) from any channel, not just from the LFE channel. Also, if there is no subwoofer speaker present then the bass management system can direct the LFE channel to one or more of the main speakers.