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Help me firgure this out?

Discussion in 'Home Cinema Speakers' started by petrolhead, Nov 8, 2002.

  1. petrolhead

    petrolhead
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    Been thinking of upgrading (upgradeitis!!)

    As I spend my time looking at threads in this forum I got to thinking.

    There are a number of contributors who have a wealth of knowledge and experience, so I am hoping that they will read this and tell me different or that I am on the right lines.

    back to basics (For me) :)

    Sound can be broken into 4 categories:
    Trebble
    Middle
    Bass
    Sub Bass

    (At any point feel free to but in :))

    The trebble handles the highs - Over 5Khtz
    Middle handles the mid tones - possibly 200 HTZ - ??
    Bass handles lower tones - possibly 50 - 200 HTZ
    The sub handles the lower frequency, ie ones who can hear and feel - possible up to 50HTZ

    So when buying a sub, surley it should do just that.

    The reason for all this waffle is that my sub (Rel Strata III) sound best when cut off at 50HTZ

    My LCR speakers finish at 80HTZ leaving a gap. This is because they are small.

    My centre speaker will never sound the same as my L&R as its a different size and shape and this seems to be the norm with a lots of manufacturers.

    So, when looking for a setup I should first make sure the LCR spears are exactly the same ie drivers, shape and volume

    The speakers should be capable of going down to a minimum of 40HTZ giving a 10HTZ overlap.

    I havn't started concidering the rear speakers yet.

    Have I lost the plot or is some of what I say making sence?

    Thank you
     
  2. Jase

    Jase
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    I think a lot depends on the actual kit you´re using and how its set up. My speakers go down to 80hz, crossover of the amp is set to Fixed THX (80hz) and the sub handles everything below this.

    I can´t tell (soundwise) where the mains stop and the sub takes over, neither can I localize where the sub bass is coming from.

    Others suggest that a lower crossover point would be better (50hz) so that the bass from the sub isn´t localized. In some cases that may be true but seems to vary from sub to sub and people to people (depending on how sensitive their hearing is!).

    I see where you´re coming from though!:)
     
  3. EvilMudge

    EvilMudge
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    Pianos are typically tuned so that middle C is 264Hz. Therefore the midrange is (musically at least) 132Hz - 528Hz. The treble therefore should start at 528Hz and go up to the limits of human hearing - which averages at about 20Hz-20Khz.
    The first octave down from 132-61Hz is therefore the upper bass, and represents the lowest frequencys which humans can localise.
    Mid Bass would then be 61-30Hz and the sub-bass or infra-sonic region would be 30-15Hz.
    This should allow you to work out where your speakers response drops.
    Hope this helps.
     
  4. micb3rd

    micb3rd
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    FACT:

    Above 20,000Hz = ultrasonic.

    About 20 Hz to about 20,000 Hz = human hearing.

    Below 20Hz = Infrasonic.


    Now In My opinion......

    Mid range is 500hz - 130hz

    Mid bass is 130hz - 80hz

    Bass 80-20.
     
  5. Reiner

    Reiner
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    Have I lost the plot or is some of what I say making sence?

    Sound reasonable. In a perfect homecinema all your speakers (including rears) are of exactly the same type and thus will have a 100% tonal match. As well in a perfect world they would cover the entire frequency range from 20Hz to 20kHz - but the home cinema world is not perfect and speakers to handle this would probably be huge and/or cost a fortune.
    As well sometimes it's not possible to match all speakers, let it be due to financial constraints or placing.

    That said you need to compromise somewhere and a sub will help to fill in the low end.
    In your current setup I would just increase the frequency of your subwoofer to close the gap, else replacing your fronts (and perhaps center) seems the only option.
     
  6. Ian J

    Ian J
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    Are you sure that your Strata sounds best when cut off at 50Hz. I have a Storm Mark 1 and that is quite happy cutting off at 80Hz which is just about where I would like it to.

    A frequency sweep shows a fairly flat response from 150Hz down to 35Hz
     
  7. petrolhead

    petrolhead
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    To my ears it does Ian but then I am probable deaf :)

    BTW Why do a lot of people suggest using the cutoff at 80hz?

    Does not make sence to me. If your mains go down to 40-45hz then you would be better having the cut off at 45-50hz :confused:
     
  8. Ian J

    Ian J
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    The 80Hz figure is that recommended by THX. I have forgotten why though.

    Many manufacturers do quote optimistic figures and although some speakers will go down to 45Hz, probably at minus quite a few decibels.

    The 80Hz figure is quite useful in that you can set all speakers to small with the sub handling everything below that. The drawback is that some people claim to be able to hear where the bass is coming from at that frequency.

    I use M&K fronts and have noticed that M&K don't make any speaker that officially go below 80Hz which means that they can claim a flat response in their advertising.

    Try using the frequency sweep on Optimode (or whatever it's called) to test your response.
     
  9. petrolhead

    petrolhead
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    What do you mean?
    How will I measure the frequency?

    Or am I now being realy thick
     
  10. Jase

    Jase
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    On dvds with the THX Optimizer there is a frequency sweep (think its 200hz down to 20hz, though that might be the AVIA set up disc!) which lets you hear how far down your sub extends. Obviously some subs are still going strong when the sweep finishes.
     
  11. petrolhead

    petrolhead
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    Ah yes i remember. I think the THX one is on the T2 DVD
     
  12. Ian J

    Ian J
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    Play that with trusty SPL meter in hand and the sub and speakers are integrated properly when the SPL reading is the same throughout the range (or as near as possible)
     

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