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Problems with bass response in my room-help please.

Discussion in 'Home Cinema Speakers' started by Family Guy, Aug 9, 2003.

  1. Family Guy

    Family Guy
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    I have come to the conclusion that my living room has no ability to reproduce bass of any kind - except peaks!!
    I had to move my room 90 degrees to get the space required between PJ and screen when I invested in a PJ. On doing this, I seem to have killed all the bass frequencies in the room except those between 54 and 49 hz - which are, in a word, LOUD!!.

    Every other frequency just seems to have dissapeared...:confused: I have changed the sub (twice), moved it around, including back to where it was before, but still nothing!!

    I also moved the sofa at the same time - maybe this is killing the bass frequencies. On the other side of the coin, mid range and treble is very good - sometimes ear splitting (Minority report springs to mind) but I put this down to the Mission 774's which. AFAIK, have a bit of a rep for "tinny" treble.

    Come on then experts - how do we get that bass back? Saw T3 in a THX approved screen last week and I want some....:smashin:
     
  2. Phil Hinton

    Phil Hinton
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    I'm confused, why don't you site the Sub in the place that reproduces the "Thunderous bass" you got when the room was the other way?
     
  3. Family Guy

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    I've tried it Phil - the trouble then is the seating is only about 3 feet from the sub...
     
  4. nfordenfield

    nfordenfield
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    OR try phasing the sub?

    p.s. there is a 7.1 tag and power amps on sale in these forums, looks a excellent bargin to me :)

    Try doing a sweep with a sound pressure metre and see where you loose it, then try putting the sub where you sit then walk around the room where ever (in reason) the thunderous bass returns, is where the sub should be, hope it is not in a doorway or half way up a wall
     
  5. Family Guy

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    Have done the avia sweep and there are pekas and troughs everywhere - an enourmouse peak at 49hz and a trough at just about everywhere else...
     
  6. Phil Hinton

    Phil Hinton
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    Some very good set ups have the sub positioned very close to the seating. infact i tried the Velo 15 1 ft from my seating accross the back of the room and it worked really well, you just have to get the volume right so it blends well.
     
  7. buns

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    If you are getting enormous peaks, put the sub somewhere such that there is a sofa between the sub and the opposite wall..... that should tame them.

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  8. Family Guy

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    Have moved the sub to where there was good bass before - still getting the massive peak between 54 and 49 hz - and the sofa is between the sub and opposite wall. The needle jumps off the scale on the spl between these freq's...
    however, there was more bass on the other freq's (according to avia and my spl meter - but not my ears) Maybe I should get them tested. I've got some polystrene tiles in the shed. I'll put some of these on the wall in the corners and see how we get on.

    Phil, in the meantime, could you give me a couple of minutes to edit the first post and then maybe move it to the speakers and subs section under the title of "is my room to dead?"

    Many Thanks.
     
  9. Phil Hinton

    Phil Hinton
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    Bry,
    Changed as requested, are you in the same house that I saw?

    If so you get the same problems as I do with alcoves trapping waves and decaying slower than they should. There are a number of things to try. The first is the expensive option which will be bass traps in each corner, and certainly behind the sub. This is not cheap with 8 traps costing about £350.
    Next is what i tried and get some thick foam. Place some behind the sub enclosure and then some soft furnisings such as heavy cushions on the floor in the corners.
    Try the sub out of corners, perhaps directly under your centre speaker or to one side, firing straight at the listening position, this will sound as though the sub is too quiet, but infact takes the peaks out of the equasion somewhat. I found this the best option with the CHT15 I had.
     
  10. buns

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    Bry..... you only mention a sofa blocking one line of sight, what about its perpendicular?

    There sounds to be about a 3.5 metre dimension somewhere providing your boom, if you can loacte it, try and block it with another sofa and see what happens.

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  11. Family Guy

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    Thanks for that - yes it is in the same room you saw. I'm putting up some tiles in the corners to try and trap the bass. The sub is sealed with no ports at all - all the air is moved by the cone - I'll see what happens when the tiles are in position.
    (I read about the tiles before on here - I actually think it was UE who suggested it...)
     
  12. Phil Hinton

    Phil Hinton
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    Unless they are heavy foam titles I wouldn't bother as I tried the same to no effect.
    The sub is sealed but you do get problems with sound around the enclosure bouncing from the walls it is next too, just try pulling the sub well away from the wall and you will hear the difference, by putting some heavy duty foam behind there should solve that element of the problem. Have you tried adjusting the phase. Get your son to stand next to the sub and you sit in the listening position, put a bass heavy peice of music on an a-b loop, then get your son to slowly adjust the dial until the bass tightens up and sounds less boomy. The apply some soft furnishings around the room until you get rid off most of the boom.
    Just out of interest how far round do you have the volume dial on the sub?
     
  13. Family Guy

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    The sub is THX certified - pressing a button defeats the cutoff and volume knobs on the sub itself and everything should be done by the processor (or, in my case, reciever:rolleyes: )
    It's obvious that my reciever dosen't cutoff at 80hz with the speakers set to small because, running the avia LFE sweep, everyting from 90hz down is coming from the sub...
    I can defeat the THX processing in the sub by swapping the lead from the amp into the second low level input. This will enable me to adjust the cutoff and volume at the sub end...should I do this you think?
    BTW, when in THX mode, the processor is outputting it's lowest possible volume on the sub channel and it's about 2 or 3 db's higher than the rest of the channels - but as I have the peaks, it's impossible to measure it properly...
     
  14. Phil Hinton

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    Don't use the THX option, by pass this and use the cross over on the sub and set it just below 80hz, then use the volume control to get it level with the speakers, then turn it down a touch.
     
  15. Phil Hinton

    Phil Hinton
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    Remember to unplugg your other speakers as well when taking the sub measurements, if you are not already doing this.
     
  16. Jase

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    Try turning the sub through 90 degree angles, into the room, at a wall, away from you etc. Have you done the "plonk the sub at your listening position and wander round the room until you hear the best bass" trick??
     
  17. avanzato

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    As you've realised you won't get the same bass from the old position of the sub as you've moved where you sit as well.

    I've been running some tests in Cara for my room and putting the sub at the mid point of the shortest wall firing down the length of the room seems to give good results. Perhaps you could try that. What is the size of your room?

    Phil: What are these bass traps where you get 8 for £350 I can only find ones at about £150 each?
     
  18. Family Guy

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    Spent the afternoon playing around with the sub and moving it from place to place (62lb of in a room that's reading 100 degrees F!!! not much fun I can say) and it looks like I'm stuck with the peaks. Measured them on the SPL and with the amp set at ref (75db) these peaks are up at 125db - give or take!!!
    I have turned the sub through 90 degrees as suggested and it seems to have ironed out the nulls - pretty ruler flat until I hit 54 hz then a massive jump to about 125db down to about 45 - 46hz. Looks like I'm gonna have to learn to live with it until I can afford a BFD...which might be early next month...
    Still - thanks for the help guys - really appreciated As I said, got rid of the nulls. I'm off to re-hydrate....:devil: :zonked: :smashin:
     
  19. Phil Hinton

    Phil Hinton
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    Azanzato,

    Auralex bass traps
     
  20. EvilMudge

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    Just had a thought Bri.

    Try putting the sub right at the inside corner of the L shape and turning it through 45 degrees so that the woofer points at the junction of the walls.

    That might calm those resonances a bit.
     
  21. avanzato

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    Just found an article in Sound on sound about bass traps and how to build them. Just for Army Bloke they include the formulae for tuning them to your problem resonant frequency, which is nice :smashin:

    The Auralex traps are £300 at Dolphin music. Looking at the Auralex FAQ the LENRD go as low as 75hz and the Venus 40hz. So they may work in my room but as you say a bit expensive, just experiment with.
     
  22. Phil Hinton

    Phil Hinton
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    Well they are far cheaper on that site than what I have been quoted in the past. Pays to shop around.
     

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