I have a question about a certain type of 'surround'.

Discussion in 'Audio Hardware' started by Rockerbox, Aug 22, 2006.

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  1. Rockerbox

    Rockerbox Forum Resident Thread Starter

    Location:
    London, Kentucky
    Guys, I'm just now beginning to get into the world of surround sound but I don't have a real 5.1 system. I bought a really nice sounding shelf system (don't laugh..it's all I can afford for right now...but it does sound nice).
    I have the two main speakers in front of me on the wall and I have the 'surround speakers' hanging just behind my couch. I am totally dumbfounded how neat this is. It's technically just two channels but, I swear, those surround speakers seem to be picking up sounds that are not coming out of the front speakers and vice versa. Granted this totally goes away once I leave the 'sweet spot' in the middle of my couch. I am playing CD's that I know are just two-channel (late 80s CD's of Pink Floyd "Saucerful of Secrets", Todd Rundgren "A Wizard A True Star", various Dusty Springfields and, right now, "Are You Experienced") and I swear it's like hearing an actual quad mix. Was there actually some experimenting going in the 60s and 70s with surround audio. "Saucerful of Secrets" in particular seems like they actually mixed it for this type of 'surround'.
    I know this is not 5.1 but what kind of 'surround' is this that I have. I'm totally getting into it. I'm having second thoughts about getting a real 5.1 system.
    I would really appreciate it if somebody could educate me a little on this.
    Thanks in advance.
     
  2. Onrd

    Onrd I am not a number

    Are your back speakers out of phase with the front ones? This could create some of the effect you're hearing.
     
  3. Lord Hawthorne

    Lord Hawthorne Currently Untitled

    Location:
    Portland, Oregon
    That's how quad was born, wiring an additional speaker or two out-of-phase.
     
  4. It could be you have the rears turned up too high. Hence the two rears are trying to compete with the two fronts.
     
  5. If you want to experience even more surround-type effects, wire your rear speakers according to the "Hafler principle":

    1) Connect your front speakers normally to your amp.
    2) Connect another speaker wire from the + terminal of your front right speaker to the + terminal of your rear right speaker.
    3) Connect another speaker wire from the + terminal of your front left speaker to the + terminal of your rear left speaker.
    4) Connect another speaker wire from the - terminal of your rear right speaker to the - terminal of your rear left speaker.

    I think I've got that right . . .
     
  6. -=Rudy=-

    -=Rudy=- ♪♫♪♫♫♪♪♫♪♪ Staff

    Location:
    US
    Yes! It's the old Hafler matrix surround trick--basically your rear speakers are connected to the left and right + terminals, but the ground is "floating" and not connected to anything other than the other speaker. I used this for many years--very effective. I actually discovered this on an old Realistic integrated amp--the B speakers had an additional switch next to them that would float the ground and give the matrix effect. :thumbsup:
     
  7. soundQman

    soundQman Idealist of the Musical Apocalypse

    Location:
    Arlington, VA, USA
    Yes, some folks prefer this to using signal processors, etc. on stereo recordings because you can preserve the purity and transparency of the signal better. Works better on some recordings than others. Not much channel separation is achieved this way, though. And you might get a more realistic result if you could insert a time delay of 15-20mS or so between the front and rear. I've looked around for passive time delay circuits but all I can find on the market are multi-function "effects" processors that have that feature also. Problem is, they convert to digital, add the delay in the digital domain, and then convert back to analog for the output. That is bound to degrade the sound. Audio Research made an analog surround processor at one time that used the Hafler matrix combined with a line-level amp and an adjustable analog delay circuit. Unfortunately these are hard to find and quite expensive, as they seem to have some inflated "collector" value.
     
  8. Rockerbox

    Rockerbox Forum Resident Thread Starter

    Location:
    London, Kentucky
     
  9. drh

    drh Talking Machine

    It's nothing to do with speaker placement; it has to do with wiring. Basically, you need to make sure that you consistently connect the + and - terminals of your amp to the + and - terminals of your speakers. In other words, if you connect the left channel + at the amp to the left speaker's + terminal and left channel's - terminal to the left speaker's - terminal, you must do the same for the right channel. (If you hook + on amp to - on speaker or vice versa, that's OK, as long as you are consistent on both sides.) To keep track, your speaker wire should have some kind of marking on one side only--perhaps it has one copper and one silver colored strand, or perhaps the insulation has ribs or dimples on one side and a smooth finish on the other. However it goes, make sure that you connect the dimpled or copper or whatever side of the cable to the amp and speaker terminals consistently, as outlined above.

    Why does it matter? If the speakers are out of phase, one woofer will be pushing air out at the same time that the other is pulling air in, and they partly cancel each other. At least, that's how I learned it back in the jurassic era....
     
  10. soundQman

    soundQman Idealist of the Musical Apocalypse

    Location:
    Arlington, VA, USA
    That's correct for the front speakers. With your "matrix" setup you will want to follow instructions in post # 5 (from Mr. Budapest, my Hafler/Dynaco matrix guy :wave: ) for the rear speakers.
     
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