Setting delays on an amp

Discussion in 'AV Receivers & Amplifiers' started by nunew33, Jul 4, 2002.

  1. nunew33

    nunew33
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    I read in a magazine that ideally sound in a multichannel format should reach a listeners ears simultaniously and delays to speakers should be set accordingly so in a set up where Front speakers are 2m in front and rear in line with listener but 1m either side of them, then you set a delay parameter that delays the rears to allow for the difference between the distance to thefronts and the distance to the rears.

    using this that means no delays would be the case where the rears are the same distance from the listener as the fronts

    The equation provided was that 1millisecond for each 30cm so in the above example rear delay should be approx 3mS.

    I have a marantz where I put in speaker distances and assume that entering 1m for each of the rears and 2m for the fronts effectively does this (ie puts a delay on the rears of 3mS)


    I want to add a rear centre but the speaker will be immediately above my head.

    So if I set the amp so that distance to speakers is:
    Front L/R:2m
    Rear L/R :1m
    Rear Centre:0m

    Then delays will be

    Front L/R:0
    Rear L/R :3ms
    Rear Centre:6ms

    But my understanding is that the Rear centre is to enhance rear panning and provide greater flyover effects. WOuld it not make it better to delay the sound on the rear centre so that it reaches the ear slightly after Rear L/R as if the speaker were further back so that flyovers sound further back and panning sounds like the speakers are in arc around the listener rather than a straight line.

    So a possible set up would be:
    Front L/R:2.3m
    Rear L/R :1.3m
    Rear Centre:0m

    Then delays will be
    Front L/R:0
    Rear L/R :3ms
    Rear Centre:7ms (effectively 1ms after rear L/R)

    I am at the hypothetical stage as I have yet to buy a speaker but wont take the plunge until I know what parameters I have to play with (dont want to spend £200 and find that because the speaker is above my head the sound is effectively fired forward and the enhanced panning from F to B and L to R isnt audible because of the speakers proximity).

    Just wondering if my logic is flawed or not?
     
  2. Electric Mayhem

    Electric Mayhem
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    Does your Marantz not give you the option for delay times for the rear centre then?? Just let the amp take care of it if it does.

    To get the best effect, the rear centre should be at least a few feet behind you. The channel delays will compensate to some extent but it would be better to have the speaker further behind you.
     
  3. nunew33

    nunew33
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    The marantz expects distance to speakers and works out the delays. I am assuming how it works based on what I have read (and laid bare that assumption in the first emails for people to validate or shoot me down in flames).

    I cant put the speaker anywhere else as the seating arrangement is against a wall so the speaker will have to either go above the listeners head or potentially behind the sofa but pointing up.

    I was just seeing if applying the logic in my first email would make the speaker sound further back than waht it is, but thinking about it if it sounds further back than it is by playing with the delays is simply going to make it out of kilter with the rest of the system, for example if an effect pans from rear left to rear right acrooss the rear centre, if the rear centre is delayed toomuch the effect will take toolong to get from rear left to rear centre and the rearcentre will still be playing the effect when the effect has reached the right channel. God, its confusing! I think I have just blown my own theory apart but would be interested if someone who has EX or ES matrix would try delaying the rear centre and seeing if this enhances or detracts from the effects.
     
  4. nunew33

    nunew33
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    In fact would a better approach be to lower the volume of the rear centre so that the timing is right but the lower volume gives a sense of distance?
     
  5. Electric Mayhem

    Electric Mayhem
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    I´ll give it a go for you and let you know. Might not be till the weekend though.
     
  6. Electric Mayhem

    Electric Mayhem
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    I´ve actually got mine set a few db lower than the readings I got for the test tones as it was too loud and overpowered the surround stage. My surround backs are around 1m behind me with the delays set to 1m.
     
  7. Electric Mayhem

    Electric Mayhem
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    Ok. Played around with the delay times last night. Basically, entering in a large distance has the effect of making the speaker seem nearer. It works back to front. Setting the speaker at 0m gave the impression it was set further back slightly. But the differences are not huge. You´ll probably get better results playing with the volume levels.

    All I did was change the delay distances, I didnt bother recalibrating the sound level, this may have more effect if you did the both together.

    cheers
     
  8. nunew33

    nunew33
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    Ive thought about this some more and although by the sounds of it I can play with delays and volumes to give the impression of greater distance what I am still going to have a problem with is that the source of teh sound will be directly above my head rather than behind it (so any changes will have the effect of making the speaker seem higher than it is rather than further back!) and no jigory pokery is going to get round that short of knocking a hole in the chimney breast especially for an enclosed speaker (which I would think would be going to far). Therefore I think I will simply live with 5.1 and miss out on the rear centre.


    Thanks for messing around to let me know what parameters I have to play with if I ever go for a seating configuraion that allows for a distance between the back of the seat and the wall.
     
  9. nunew33

    nunew33
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    One last thought on the subject. Attached is my room map.

    Would I get the centre rear effect by placing a pair of speakers in the alcoves or would the sound be too dispersed especially with the chimney stack in the way? Hmm maybe I could place them so that the fronts are flush with the front of the stack, but I will get aesthetic objections from my wife!


    On the amp there is one set of binding posts for rear centre. What would happen if I took a pair of cheap 8ohm bookshelves (Kenwood rears from about 1996!!)and wired them both to a single binding post in order to test the above paragraph.
     

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  10. Electric Mayhem

    Electric Mayhem
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    Hi

    Here´s a link about wiring the two speakers to one output.

    http://www.avforums.com/forums/showthread.php?s=&threadid=35072&highlight=series+parallel

    Putting the speakers in the alcoves may work but it depends where your rear left & right surround speakers are. The surround backs should really be inside the other surrounds and not to the outside of them (if that makes sense!).

    As you are dealing with a mono signal, using two speakers will give the impression that the sound is coming from between the two i.e the centre of the chimney stack. The other thing to consider is the alcoves might cause some weird acoustic effects on the sound and have it bouncing around all over the place but you wont know unless you try it.
     
  11. nunew33

    nunew33
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    The map is updated to show where I sit and where the rears are at the moment at least I thought I did. Doesnt seem to work. hang on ill attach it to a follow on messge
     
  12. nunew33

    nunew33
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    Bloomin computers, should be attached to this
     

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  13. Electric Mayhem

    Electric Mayhem
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    I can see it now:)

    The only thing I can suggest really, is to try it to see what effect you get. You´ve either got to try them in the alcoves which hopefully will work and you wont get any nasty side effects or, you´ll have to have them on the chimney stack, drawbacks to that is they are right above your head and you wont get a good effect as there´s no depth and also the missus´ might get the hump because you´ve ruined the decor!!

    Short of rearranging the room but thats taking it a bit too far!!
     
  14. nunew33

    nunew33
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    Thanks for your help Jase. That link was very useful. I will have a play with my cheap and nasties this weekend
     
  15. Lowrider

    Lowrider
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    I think that back speakers that close to surrounds will only smear the sound, nothing else...
     
  16. nunew33

    nunew33
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    Have decided that the solution will be to use some form of custom install speakers such as KEF Ci series. I can easily dig 3.5 inches into chimney breast. That way I get a single speaker dead centre, get the aesthetics that suit the wife (who gets a redecorated room once I have embedded cabling in walls).

    I am assuming that: considering the lack of ES/EX software available, the fact that it is an effects channel not a primary sound souce that I can get away without worrying too much about speaker matching, and that something like the KEF should work with Mission 7. (its not the kind of thing you can demo easily). Also for centre rear would a dipole (KEF Ci130DS) be better than a normal speaker configuration (keF CI130qs)
     
  17. Electric Mayhem

    Electric Mayhem
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    Hi

    I would try a normal direct radiating speaker rather than a single dipole (two dipoles, different story though!).

    There´s actually quite a few EX/ES films, worth doing a search on here as there have been lists posted.:)
     
  18. nunew33

    nunew33
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    Thanks.

    So Ci130QS or Ci160FS it is then a snip at £80.

    One of these is 6ohm does it matter that all the missions are 8ohm. I dont understand the impact or science of speaker loadings.

    And are my assumptions about the speaker matching ok, ie for the amount of use it will get, a reasonable quality speaker will suffice?
     
  19. Electric Mayhem

    Electric Mayhem
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    You should be ok with a 6 ohm speaker load, 4 ohm might cause a problem but it depends on the amp.

    Its not going to be an exact tonal match but it depends how sensitive your hearing is! Might stand out a mile that its different or might not. You´ll notice most when the sound pans from side to side, not so much when there´s spot effects behind you.

    My surround backs are´nt an exact match and there´s a tonal change, I´m quite fussy but had to compromise and go for smaller speakers, hence the difference.
     
  20. nunew33

    nunew33
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    Sorry if its a bit of a newbie questions, but what is teh problem caused by low impedence speakers? How would I know there was a problem?
     
  21. Electric Mayhem

    Electric Mayhem
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    Have a look here:

    http://www.audiovideo101.com/dictionary/ohm.asp

    Basically a 4ohm speaker draws more current and needs more power from the amplifier (which some lesser amps/receivers can´t keep up with).
     
  22. nunew33

    nunew33
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    Youve been a lot more helpful than the store I bought the amp from.

    Thanks for all your input Jase.
     
  23. Electric Mayhem

    Electric Mayhem
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    No problem:)
     

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