Crossover frequency

Discussion in 'AV Receivers & Amplifiers' started by mechmohr, Jun 12, 2008.

  1. mechmohr

    mechmohr
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    Hey dudes,

    Could u please explain me wats the significance of crossover frequency ?

    Thanks
     
  2. mjcairney

    mjcairney
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    If, for example, you set a crossover frequency of 80hz, then all frequencies below that are sent to the subwoofer (which is designed to handle the low frequency signals), whilst ones above it are sent to the speakers.

    Hope that helps.

    Cheers,

    Martin.
     
  3. swanny78

    swanny78
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    You should check the crossover or frequency range of your speakers and sub so you know what to set it too....I would recommend a 20h roll off too so it intergrates better..ie if your speakers minimum frequency is 80hz set the crossover to 100hz so you have a 20hz overlap before the cross over.
     
  4. mechmohr

    mechmohr
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    Hey mj and swanny...thanks for ur reply...the speaker manual read as " Bass response lower limit 120 Hz" and in my reciever the crossover frequency settings are 40,60,80,120,150,200 and 250Hz...So is it ok to set 150Hz as per my speaker spec of 120 Hz..

    also, i want to know what will happen if i set crossover frequency in rec. below 120hz, say, 80Hz like dat...If i do like that will it affect my sound output..Pls clarify.
     
  5. mjcairney

    mjcairney
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    Yes, set your crossover to 150hz, that'll be fine.

    As to your other thoughts re trying it lower than that, go ahead and give it a try and see if there's much difference and which you like better - you'll not do any harm.

    Cheers,

    Martin.
     
  6. Mr Incredible

    Mr Incredible
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    And to add to that, the crossover is not a brick wall. In so much as all frequencies above the crossover get sent to the speakers, and all the frequencies below the crossover get sent to the subwoofer, the crossover is a filter which rolls off the lower frequencies below the crossover and which also then get sent to the speakers, and rolls off the frequencies higher than the crossover and which also then get sent to the sub.

    At 150Hz crossover, the sub will be getting a "mono" signal which may have originated for the centre or effects channel and which now means the ear will be able to locate those sounds as coming from the sub: very disconcerting if the director intended an effect to be anchored to the screen via the centre channel only for it to appear behind you or wherever your sub is.

    Because most AV receivers adopt the same or very similar frequency roll-offs above and below the crossover point (-24db per octave for a low pass filter and -12db per octave for a high pass filter), there is a rule of thumb which suggests the crossover point should be an octave above the low frequency response (-3db) of the main speakers. Read Octave as a doubling of the frequency.
     
  7. mechmohr

    mechmohr
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    Hey experts,

    My speaker manual says 120Hz crossover freq....whereas my audessy setup says crossover freq as 60Hz....Which one to be selected....I am confused...:confused:
     
  8. Mr Incredible

    Mr Incredible
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    What speakers do you have?
     
  9. mechmohr

    mechmohr
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    I have Boston MS8000s home theatre speakers - all are bookshelf type(Micro 80xII) - 8ohms impedance and 100w output.
     
  10. Mr Incredible

    Mr Incredible
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    I'd stick with the recommendation in the speaker/sub manual.

    How are you wired:-
    (1)
    [​IMG]

    or
    (2)
    [​IMG]

    or
    (3)
    [​IMG]

    or (4)

    [​IMG]
     
  11. spooney

    spooney
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    Audessey takes the lowest possible depending on your speakers respones during the measurement.
    I took 80Hz because this is the THX recommendation and my speaker set fits perfectly into this.

    If your speaker manual says 120 Hz then this is the right setting.
     
  12. mechmohr

    mechmohr
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    Hi bob,

    I used the setting type 4 of your picture....and i personally feel that after setting up audessy the sound hears amazing...I can hear even minute sounds from all the speakers...but my only disappointment is it has reduced SW sound level to -5db...but apart from that others are quite great.....

    I have seen only type 4 and 3 in my spk manual....and i would very much like to know the difference b/w all these types and how it will affect? If u can then tell me bob...
     
  13. Mr Incredible

    Mr Incredible
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    TBH 1,2 and 3 will not give nay difference to the final result. I believe the "options" are for convenient wiring to suit a room / sub position in relation to the speakers. I had thought if you had wired up 1,2 or 3 it may have resulted in the low Audessey crossover as the sub would have been working at the same time as the main when the sweep happened. As it is, you've used the line-in which is the more "traditional" way of hooking up a sub. Nothing to stop you upping the output on the sub a little if you wanted! Whatever an auto set up does, let your ears be the final QA tester!
     
    Last edited: Jun 16, 2008
  14. BruceA

    BruceA
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    Audessey measures the lowest frequency at which the speaker can make a reasonably loud sound (in my view at least) - - that is a little dodgy as the lowest sound your speaker can make may not be all that clean. Generally I would suggest manually going up a half or full octave from that low limit found by audessey (1.5x to 2x frequency) the 2x option in this case gets you to 120Hz your speaker manufacturer thought of. So try that.

    I would not go higher for luck at this level . . firstly many subs are not at their best above about 150Hz and it certainly gets easier to 'locate' a sub producing frequencies around 200Hz (The crossover is not a dead-stop . .. the output just reduces fairly quickly above that).

    Equally therefore saying "Lets use the THX crossover of 80Hz anyway is a bad idea if your speakers are not going down to 60Hz or below . . It certainly won't make it a THX system!) Take a look at THX speakers . .they are never 10cm cubes :)

    Finally assuming you are not calibrating or planning on playing your system at maximum (loudest cinema/pop concert) levels then an increase of sub gain of around 3-4 dB over 'flat' is scientifically required to compensate for the ear's insensitivity at low frequencies. Many home cinema fans having bought a big sub will add 1 or 2 more dB because it sounds good. HOWEVER It should be noted that this is a wonderul approach if you have a few thousand quid of response testing and equalising gear and actually have a flat subwoofer response. If not you probably have at least one almighty peak in the the low frequency output from room size and at least one dip. The peak in particular may fool Audessey into reducing the gain to try get it in line (depends on the room, pink noise response etc etc.) Best advice if not spending the 1000's (just yet ;-) is to let audessy do it's thing, then readjust the sub level manually listening to music with a good bass track . . then turn it up a little until (hopefully) your movie explosions make you duck!
     
  15. mechmohr

    mechmohr
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    Hi everyone,

    I got a new problem, Whenever heavy bass is being output i hear mild cracking noise from all of my speakers. I hav assigned 120Hz as crossover frequency and set crossover frequency to bypass in my subwoofer as said in speaker manual but still i hav this problem Got any solution...pls
     
  16. dUnKle

    dUnKle
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    so for my old (but trusty) b&w 603s2s what should I use
     
  17. Mr Incredible

    Mr Incredible
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    I'd say 80Hz Dunkle.
     
  18. dUnKle

    dUnKle
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    so 100 for the sub crossover ?
     
  19. Mr Incredible

    Mr Incredible
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    No, crossover should be set to off, bypass of at its max. The amp is doing all the management, not the sub.
     
  20. dUnKle

    dUnKle
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    K cheers
     

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