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Advice on a hifi setup needed - acoustic problem

Discussion in 'Hi-Fi Stereo Systems & Separates' started by stefmcd, Nov 7, 2004.

  1. stefmcd

    stefmcd
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    OK I've set up a hifi in 2 canteen rooms.

    Rooms are rectangular and measure approx 17m by 6m.

    I've placed two speakers in each room at diagonally opposite corners.

    The source is a PC feeding into a mixer feeding into a Yamaha amp and then onto TDL nucleus speakers. The amp has an A and B speaker selector which are both selected to power the four speakers.

    The speaker cable is 79 strand and some of the cables are over 25 m in length.

    The top of thespeakers are positioned about 10 cm from the ceiling (in the corner) and are tilted downwards - raised at rear by a block of wood about 3 cm high. They are on an MDF platform.

    Basically the sound is very bass heavy. I've had to move the bass knob on the amp to the quarter to position and the treble to the quarter past - plus move the bass frequencies down on the mixer's equaliser and the treble frequencies up.

    The amp's volume control is in the 12 oclock position.

    I'm still not happy with the sound.

    It does not help that there is no mono option on the amp which would at least ensure each speaker is creating identical sound.

    Thes are the specs of the amp and speakers -

    http://www.richersounds.co.uk/index...tl.php&p=201818

    http://www.richersounds.co.uk/index...tl.php&p=201554

    I suspect I shall have to buy another amp and another 2 pairs of speakers - I know this will not cure the bass issue but may allow a volume reduction as there will be increased 'coverage'. Anyway I'd like peoples opinions.

    :)
    Any ideas?
     
  2. SKA.face

    SKA.face
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    I can see a few problems here,firstly I'm trying to picture a canteen,and hope i'm visioning it correctly,as lots of hard surfaces and reflections,not nice,a major cause of room boom for one,it would need curtains,thick ones at that,and soft objects that can absorb and break up soundwaves.

    Next,lets look at speaker positioning,firstly move the speakers out of the corners,they are acting as a horn,bring the speakers well away from the corners,then closer together,about 2m apart.


    Your turning the treble amp,because you can't hear the treble,so bring the speakers down of the wall,it's not spiderman so bring him down to more or less ear height,oh look theres the missing treble.


    Next,lose two speakers the amp is struggling to drive all four at once,plus causing major confusion to sound,the amp won't like it,so use only two,with shorter cable runs,the cable is ok at the moment.

    Take these primary steps and sound will improve,the room has the biggest effect on sound,yours is a nice size,just cold and hard surfaced.
     
  3. stefmcd

    stefmcd
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    Thanks for reply -

    I think curtains would certainly help.

    Speaker height is not flexible for security/safety reasons - public area full of kids. I think moving from corner would be a good idea. Does selecting both speaker sets A and B on the amp effectively half the power levels to each set? I was assured when I purchased that this was not the case but..........well I had doubts.

    Cable length is not flexible either as the amp is located in another room with a dj setup. I've had to run the cables through loft space.

    Fiddling with the mixer's equaliser has improved the sound somewhat but I think your curtain and speaker position ideas would go further - thanks.

    :)
     
  4. ancientgeek

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    When you place a speaker against a hard surface, it reflects the sound just like a mirror, so you get a mirror image "virtual speaker" adding its sound to the original. The high frequencies may add or cancel at different frequencies, but the low frequencies all add. So you get a bass boost (to almost double) by placing the speaker against a wall. Placing it in a corner almost quadruples the bass. Placing it also near a hard ceiling doubles it again to a theoretical 8-fold bass boost compared to a speaker away from the walls, floor and ceiling.

    Also, I think you will do much better with the speakers both at the same end of the room. At opposite ends, the time delay difference between the speakers for sound to arrive at the listener will do horrible things to the sound quality for anyone not in the middle of the room.

    Since you have two sets of speakers, you can use your A/B switch to compare the sound for different positions rather easily.

    I would suggest one on each long wall, not too near the ceiling, perhaps 1.5m away from the end wall.

    If you can hang them from the ceiling, then perhaps 1m in from the side walls too.
     
  5. ancientgeek

    ancientgeek
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