A question re: dd ex

Discussion in 'AV Receivers' started by chris rick, Feb 22, 2004.

  1. chris rick

    chris rick Second Unit

    Joined:
    Sep 20, 1999
    Messages:
    300
    Likes Received:
    0
    So I used to have dd ex(homebrew) in my house and am thinking about doing it again. A dumb question though...so I hook up the surround pre outs of my dd reciever to my old pro logic reciever and then hook up left right and center speakers on the prologic reciever right? How is it then that people get two surround channels when there is only one connection for a center channel on the dolby prologic reciever? Am I missing something? Thanks!
     
  2. Sean Conklin

    Sean Conklin Screenwriter

    Joined:
    Oct 30, 2000
    Messages:
    1,720
    Likes Received:
    0
    The surround pre-outs are only going to reproduce the existing surround sound, it will not be discreet.

    The 2 surround channels on a pro-logic output are mono.

    The center channel is a mono output as well, maybe you could be just a little more thorough in describing what you mean, because I may have given you useless info.
     
  3. Sean Conklin

    Sean Conklin Screenwriter

    Joined:
    Oct 30, 2000
    Messages:
    1,720
    Likes Received:
    0
    You cannot get DD EX from a pro-logic decoder. You can't get 5 discreet channels. You need a processor capable of seperating the discreet information given by DTS or DD codec.
     
  4. chris rick

    chris rick Second Unit

    Joined:
    Sep 20, 1999
    Messages:
    300
    Likes Received:
    0
    that's not helpful...maybe I'm misunderstanding something.
     
  5. Michael Reuben

    Michael Reuben Studio Mogul

    Joined:
    Feb 12, 1998
    Messages:
    21,763
    Likes Received:
    2
    OK, let's clear this up.

    Chris is talking about a "homebrew" DD EX setup. Typically this involves a receiver that can decode DD 5.1 but doesn't have EX capability. One then takes the two rear pre-amp outputs and runs them through the front section of a separate ProLogic decoder. The theory is that the matrixing used to extract a rear center channel for EX is effectively the same as that used to extract a front center channel for ProLogic.

    Chris, the answer to your original question is that most people using two rear center surrounds aren't using a "homebrew" setup. They're using a receiver that incorporates EX decoding and supports 7 speakers. The recommended setup for DD EX in the home involves two identical rear center speakers being fed the same output.

    M.
     
  6. chris rick

    chris rick Second Unit

    Joined:
    Sep 20, 1999
    Messages:
    300
    Likes Received:
    0
    Thanks Michael your answer was what I was looking for! So I guess I'll hook it up again with one back surround and perhaps upgrade to a 7.1 reciever eventually.
     
  7. ChrisWiggles

    ChrisWiggles Producer

    Joined:
    Aug 19, 2002
    Messages:
    4,791
    Likes Received:
    1
    You can just wire two speakers off the center output of your PL receiver and get the same thing pretty much. I use a 6-channel receiver, and wire two speakers off the back output.

    Some receiver provide separate amps for this that output mono, but one for each of the SB speakers, if you have two. Others have added processing to steer between these two, something that you can't achieve with your homebrew PL decoding.

    Regardless, the reason to use two, even in mono, is because one centered right behind your head can suffer from the reversal affect, where you can confuse that sound as coming from the front instead of behind you. Then adding a little more DSP processing to steer between these was a small step for the higher end receivers/processors.

    Hope that helps!
     
  8. Wes

    Wes Screenwriter

    Joined:
    Sep 30, 1997
    Messages:
    1,190
    Likes Received:
    1
    Location:
    Utah USA
    Real Name:
    Wes Peterson
    Chris, I am currently running a home-brew EX/ES set up in my theater and have been for over 3 years now. Yes just wire the Center Channel of the DPL receiver up to two Surround back (ES/ES) speakers. I have a drawing of this set up on my DIY page on my Theater web site (see my site).

    Wes
     
  9. chris rick

    chris rick Second Unit

    Joined:
    Sep 20, 1999
    Messages:
    300
    Likes Received:
    0
    Ok..I have been using my homebrew set up for a couple of weeks now and I like it a lot...with just one speaker. I understand the concept behing dd ex/dts es, but how does one wire TWO speakers from the ONE center channel output of the dpl reciever for ex/es? I don't understand that....
     
  10. Aaron Gilbert

    Aaron Gilbert Second Unit

    Joined:
    Sep 17, 2003
    Messages:
    319
    Likes Received:
    0
    Chris,

    As was stated before, you just need to connect your two surround speakers to the single center channel output on your pro-logic receiver. You can do this with the speakers in parallel or in series.

    Parallel is prefered as it's simpler and will give you potentially more power available, but be aware that your receiver may not be able to handle an impedance that's now half of a single speaker. If you have 8 ohm nominal speakers, for parallel wiring, your receiver should state it can use 4 ohm speakers. If so, you would connect all (+) terminals together and all (-) terminals together.

    More likely, you will need to do series wiring, which will double the impedance, but negate any chance of your receiver overheating. The power difference may not matter. For series, wire the (+) from the receiver output to the first speaker, then take the (-) from the first speaker and connect it to the (+) of the other second speaker. Then connect the (-) of the second speaker to the (-) of the receiver.

    Aaron Gilbert
     

Share This Page