Had a 5.1 surround for years..is it 5.1 ?

Had an amp for years, before getting a sub, but the sub has a option on it, volume, crossover frequency, and phasing, and also high level input and output.

I've got the setup about right on watching DVD's, but it don't work at all watching normal TV, where the surround works?

So what is wrong with the setup?

It's volume is set at 10 max, the crossover frequency, and phasing, is random? What should the crossover frequency be? and why phase it out 180 degrees? Surely it should be in use on normal telly? not just DVD's? Surround works on TV, but not sub?

As far as I know normal TV isnt broadcast in 5.1

surround sound is extrapolated from the stereo signal, obviously L&R is obvious, the centre channel plays anything that appears in the left AND right channel, the sub also does this, after applying a low pass filter.

The rear channels use a combination of phase shift and filters to decide what goes behind you, but only in mono.
dolby digital encodes a seperate rear track inside the normal stereo track, that the dolby receiver sees and gives stereo rear speakers.

most TVs etc use the first, the stereo perception in front of you fools your mind into beleiving the rear is also in stereo.

http://www.jyi.org/features/ft.php?id=435 this is quite a good artical on it, and how to create a basic surround system just by clever wiring.

When watching DVDs you are using a dolby digital soundtrack where each channel is individually encoded.

When watching TV you are only receiving stereo (unless its a Sky HD channel for example) and the amp will use prologic decoding to generate the rear sound and center speaker sound. It will not normally generate any sound for the sub.
On some amps you can set the front speakers to small (therefore indicating they cannot produce much bass) and the amp will redirect this sound to the sub. This is also handy when playing music as it will do the same but without the prologic decoding. This feature may not be on the amp you have however.

TV IS received in 5.0, but not 5.1? Why? So back to my origional question, surround sound by TV transmission IS received, but no bass, ie the .1, why? or is my setup wrong? Do they transmit 5.1, or just 5.0 ?

What is the crossover frequency/phasing meant to be?

I put a DVD on, obviously the .1 is working, but not when watching TV, but when watching TV, surround works, minus the .1.

The cut off and 180 phase confuse me. Is the .1 transmitted, and my subwoofer set wrong? Or do they not transmit that information? As they do surround?

How do you know the tv is received in 5.0?
Does it say so on the screen somewhere or are you just basing that on the fact that sound comes out of 5 speakers?

When playing a DVD the sound is in dolby digital 5.1.
When watching a HD TV picture if available the sound is normally transmitted in dolby digital 5.1.

If your system receives dolby digital 5.1 it will play it back including the .1 for the sub.
If it receives stereo a prologic decoder will be used to turn that into simulated 5.0 surround (no sub)

This is a little bit "sucking eggs" for you I'm sure, but bear with it...

TV sound used to be simple; everything was mono, so no surround sound or anything.

In the 80's TV companies started broadcasting stereo. They used the NICAM system so older mono-only sets weren't affected, but TV's with the NICAM decoders could get stereo. At that point it became possible to include some surround information. That surround information was encoded as Dolby Surround.

Dolby Surround is a way of including surround information that doesn't interfere with stereo-only receiving devices, so an ordinary NICAM Stereo TV ignores the Dolby Surround, but a TV with Dolby Pro-Logic can decode the information and give a centre channel and mono rear effects in addition to the stereo L & R signals.

The important thing about Dolby Surround is that the centre and rear channel information is new information embedded in the stereo L&R signals. i.e. it's not "made up" from the plain stereo channels.

Pro-Logic decoders can take stereo and fudge some surround effects, but that isn't the same thing as decoding the hidden centre and surround info embedded in a Dolby Surround encoded transmission.

So, to recap in the old analogue TV transmissions we had Mono, Stereo, and Stereo with Dolby Surround encoding (Stereo DS).

Freeview, Freesat and Satellite and the HDTV versions of those add another layer of complexity.

Stereo and Stereo DS became the de facto standard. They all broadcast with a full range audio frequency to the L & R channels. There is no separate bass track as you'd get with Dolby Digital or DTS. How your amp handles bass though is something different.

If you have a speaker kit with little satellite speakers and a sub, then your amp should be set up with the satellites on Small and a sub present. In this set-up all the bass information is directed to the sub. It doesn't matter if its DD or DTS 5.1 playing, or Stereo from a CD, or the sound from your TV.... the sub makes the bass noises and the satellites do the higher frequencies. If this isn't happening in your system then you need to check the amp settings.

If the amp has a crossover setting then I recommend setting it to 80hertz. Gain (volume) around 12o'clock position and phase depends on room acoustics. Try 0 then 180. Your own prefference really to which sounds better. If amp has no crossover setting for sub then set dial to around 80hertz, anything below this setting gets played by sub & anything higher uses 5speakers.

gblades said:

How do you know the tv is received in 5.0?
Does it say so on the screen somewhere or are you just basing that on the fact that sound comes out of 5 speakers?

When playing a DVD the sound is in dolby digital 5.1.
When watching a HD TV picture if available the sound is normally transmitted in dolby digital 5.1.

If your system receives dolby digital 5.1 it will play it back including the .1 for the sub.
If it receives stereo a prologic decoder will be used to turn that into simulated 5.0 surround (no sub)

Click to expand...

My ears tell me that I receive 5.0 sound, due to the fact that speech comes from the centre speaker, left and right sounds are provided by the front speakers, and anything other goes via the rear speakers. However, nothing on normal TV uses the subwoofer. The DVD players do, but not TV.

In fact many films, shown on TV, have the trailer at the end that say encoded in DTS, NOT pro Logic 2, to me DTS sounds better, as my amp receives that also. But TV transmission doesn't rebroadcast in DTS, or Prologic, just stereo+2..??

So digital TV doesn't bother to transmit the correct format? Possibly due to bandwidth restrictions?

I've set my sub up to not induce bottom inducing unnecessary spills. But wondered about the various settings. 180 degrees out of phase, many kilohertz cut out phasing, and the volume.

If a film is advertised as DTS/Pro Logic, on TV, then surely they are selling the public short?

The film trailer may say the sound has been encoded using DTS but thats just information how the film was made. Normal TV will be stereo only apart from some HD channels which may broadcast some programs in dolby digital 5.1
So for normal stereo programs then your amp will convert it using prologic to 5.0.
If you want to hear the 5.1 programs which are broadcast on HD channels you will need the amp connected to the tv properly. How this is done will depend on what is receiving and decoding the tv signal, how its connected to the tv, and what digital outputs are supported on the tv.