notch filter on ms 309i

Discussion in 'Subwoofers' started by micks_address, Sep 19, 2007.

  1. micks_address

    micks_address
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    Hi Folk,

    i have searched through the threads but still confused.. i got my spl last week - the radishack analogue one.. i have the test tone cd that came with the sub.. i know i need to play all tracks and record the tones with the spl.. for this - what db range should i set the spl at?

    step 5.5 says to set the filter to the track with most over empasised level... what does this mean?

    next step is to set the cuf off control - reduce this level to be consistent with adjacent readings..

    sorry if this has been covered before but would like to do the job properly after investing in the spl.. thanks in advance for help

    Cheers,
    Mick
     
  2. Member 96948

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    They're suggesting the single most useless way of working the notch filter.

    Go to Home Theater Shack and download the 1/6th octave test tones (burn them to a CD) and download the .xls spreadsheet that matches your SPL meter.

    Using this you will be able to see exactly where your biggest peak is and exactly what effect the filter is having. It's the only sensible way.

    Russell
     
  3. micks_address

    micks_address
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    Hi Russ,

    thanks for the help - is there an idiots guide somewhere to doing this?

    Cheers,
    mick
     
  4. Member 96948

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    I am an idiot and I can guide you.:D

    Basically at it's simplest, you set your speakers to small and the amp to stereo (not direct or pure direct). Set the SPL meter to 'C' weighting, 'Slow' and the 80dB range. Put it where your head would be.

    Pick one of the higher test tones (>60Hz) and turn the amp up until it registers about 80db on the meter. Then, starting from the lowest tone, write down whatever level the meter shows for each tone. Depending on peaks and troughs, you may need to turn the meter down to the 70dB range or up to the 90dB range to keep the needle on the scale.

    If you haven't got MS Excel, Post the results here and one of us can put them into the graph for you. You will then have a frequency response for you room and the forum in general can start arguing about it.

    BTW, this same method should be used for fine tuning positioning, phase and crossovers long before we start messing with the notch filter, but we can help there too.:)

    Russell
     
  5. hoppaz

    hoppaz
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    Mick I have the same sub and initially used an spl meter to set the level to good effect. However what I did find that certain dvds / music cds seemed a bit more bass heavy than others so I had to adjust the output level in these instances. In the end I just play it by ear but I did do a lot of playing around with the notch filter and found that for me it had very little effect. Are you not happy with the performace of the sub when not using the notch filter?

    Hoppaz
     
  6. micks_address

    micks_address
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    no i find the sub great.. just feel like i should be using the extra functionality when its there :)

    i do find it can be a bit boomy at times (if thats the right word) with bass heavy music...

     
  7. Member 96948

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    If it's not making a difference it's because you can't use blindly and hope to happen across the right combination of frequency, cut/boost and Q. You have to see what you are doing, because tiny increments can miss the frequency you want to effect.

    SVS subs have a very similar function, but they correctly call it a single band of parametric equalisation. To show how effective that single band is, I posted this.

    Russell
     
  8. hoppaz

    hoppaz
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    Point taken Russ but where does all of this stand if say I play one dvd or cd which sounds boomy and then play another which doesnt (and I have come across quite a big difference)? Does playing with the output level affect the results shown in the graph if I were to set up the notch filter using my spl and REW software?

    I do at the moment prefer just turning the output level slightly up and down in this case to get a nice level of bass.
     
  9. Member 96948

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    Some DVDs and CDs are just less/more bassy than others. This is in line with your personal taste, or it's not - only you can decide what is too much or not enough and turn the sub up/down to suit. I do it all the time.

    However, some CD/DVDs just have a lot more energy down at the region where the room's peak is. Every time a note or tone with enough energy reaches it, you get your 'boom'. You can take this right out using the notch filter. That peak on the graphs in the link is not the sub - it's the room, but you have to tune the sub to reduce the peak.

    What you will find is that the peak will dominate the subs sound, causing certain notes to stick out like a sore thumb and thus, dictating how loud you turn the sub up. Tune the peak out and the sub can be turned up to compensate, plus it will sound deeper AND tighter as a result.

    REW is the perfect tool for doing this. It really is worth the effort. Do some sweeps, post the graph here and we can all argue about which peak is the one to tame.:thumbsup:

    Russell
     
  10. micks_address

    micks_address
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    Russ - to use REW do i need to connect the spl to my pc via sound card? or is it possible to get accuracy measuring manually and inputing the results?
     
  11. Member 96948

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    REW uses the SPL as the microphone. REW actually generates it's own test tone sweep so it need to be connected to a spare stereo input on the amp and to the SPL at the same time.

    It's my understanding that these need to be line in/out sockets and not headphone/microphone sockets.

    I don't use REW so hopefully an 'expert', or Nimby, will drop in with better detailed advice than I can offer. But for starters, I'd drop in at the REW/BFD FAQ on Home Theater Shack. It's written and supported by the bloke who wrote REW. It's very good.

    Russell
     
  12. hoppaz

    hoppaz
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    it sounds quite a complicated process. Is there another way to do it (get the graphs other than using REW)?

    Also how does your Monolith intergrate with your RB-985?

    I am debating about going for one of those or an SVS sub in order to complete my system (I consider the 309 the weakest link in my system at the moment).
     
  13. mattkhan

    mattkhan
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    you can take the reading manually and enter it into the spreadsheet downloadable at hometheatershack. This is quite a painstaking process and somewhat less accurate then using REW. There is a learning curve to REW but it is essentially simple and once you have the hang of it then you can tweak to your hearts content instead of laboriously taking readings yourself.

    All you need is a computer with a linein on the soundcard, an SPL meter and you're away.

    Cheers
    Matt
     
  14. hoppaz

    hoppaz
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    I have a laptop with line in and an spl meter. So (through very basic research) I beleive I burn some tracks to a cd and play these and record the results??? My SPL is an analogue one does that make any difference??
     
  15. Badger0-0

    Badger0-0
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    Analogue ones are actually preferred for some reason.
    Anyway, the standard one to use is the Radioshack, because there are correction files to compensate for it's inaccuracy.
    Whatever, you need one with a line out connection, to plug into the line in of your lappy.
     

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