How does my subwoofer REW graph look?

Discussion in 'Official REW (Room EQ Wizard) Support Forum' started by Bone9, Jan 27, 2019.

  1. Bone9

    Bone9 Member
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    Hi guys just to start can someone confirm I have this setup correctly. I have a digital radioshack spl meter that is connected to the line in on my htpc via a phono to jack cable. Then the htpc is connected via hdmi to my avr. I have downloaded the radioshack calibration file. The sound card hasn't been calibrated, not sure how to do this with my configuration.

    Anyway some opinions on my graphs will be great. These are all the subwoofer only with the speakers disconnected.

    For the first graph what crossover looks best? Notice the difference in the low but then also later in the range it reduces the difference in the peaks etc. Currently got the mains crossed over @ 80Hz but not sure if 60Hz would be best?

    Main Crossover Comparrision.jpg

    This is my sub only with the mains crossed at 60Hz.

    Sub Audyssey On.jpg

    This is a comparison with Audyssey on and off to see the sub eq difference. Do you think I'd benefit from an antimode?

    Sub, Audyssey On & Off.jpg

    Any opinions would be great! Thanks.
     
    #1 Bone9, Jan 27, 2019
    Last edited: Jan 29, 2019
  2. Sonnie

    Sonnie Senior Admin
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    What subwoofer are you using? How many?

    Have you tried some different placements for the sub to see if you can get rid of that hump at 30-35Hz? Maybe even as simple as turning the sub around.
     
  3. Bone9

    Bone9 Member
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    Hi I'm using 1 BK Electronics Monolith Plus front firing. No I haven't tried any other positions yet as I wanted to know if the current graph looks pretty good or not?
     
  4. John Mulcahy

    John Mulcahy REW Author

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    What is playing in the first graph, sub + left + right? Need to look further up into the frequency range to see how the sub and mains are integrating and the overall levels. Should also set the frequency axis to logarithmic it is using linear spacing at the moment.
     
  5. Bone9

    Bone9 Member
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    These were all taken with just the sub only running. I'm currently just interested in the performance of the sub, not integration with the mains atm.

    When I get home I'll change the graphs to logarithmic.
     
  6. John Mulcahy

    John Mulcahy REW Author

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    It doesn't really make sense to try and pick a crossover setting without seeing how sub + mains perform, the combined response will typically be very different to the response of the sub alone.
     
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  7. Bone9

    Bone9 Member
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    I can only have one main running with the sub atm with my current cable configuration. All I'm interested in is the sub performance. The spl meter won't be very accurate with high frequencies.
     
  8. Bone9

    Bone9 Member
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    So I've found a problem. When I first did the test I must of had the door open a bit as I couldn't get near the original graph till I opened the door a tad. When closed (this is how I have it during movies) the lows are terrible! I then fully opened the door and look what happens...

    Door.jpg
     
  9. Bone9

    Bone9 Member
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    Front right speaker with sub and the door open slightly.

    Door open a bit and front right speaker..jpg
     
  10. Matthew J Poes

    Matthew J Poes Staff Writer
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    This is very normal. Opening a door let’s the bass out! Stops the reflection from being as strong. It’s a common “old” acoustics trick used by audiophiles and studio guys. I always have to laugh when I hear about someone talking about this phenomena with some kind of mystical tone. It’s not mystical, the sound doesn’t reflect off the back wall and no longer cancels.

    My guess is that your big peak down low is probably close to 4 times the length of the longest wall of your room. Is that right?

    Is your room fairly small?
     
  11. Bone9

    Bone9 Member
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    The 32Hz peak? Not sure how to compare that to the length of my room? Yes the room is quite small and has a lot of furniture in it atm. I don't have the dimensions to hand but here's a pic...

    2019-01-06 (10).png
     
    #11 Bone9, Jan 29, 2019
    Last edited: Jan 29, 2019
  12. Bone9

    Bone9 Member
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    If I'm right the 32hz wave length is about 2.4 times the length of the room. Roughly as I don't have the exact dimensions with me.
     
  13. Matthew J Poes

    Matthew J Poes Staff Writer
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    Not quite how it works. That would be a HUGE room.

    I’m estimating the mode is caused by a dimension of roughly 8 to 9 feet.

    Once a room becomes large enough to contain the entire wavelength the behavior changes and it begins to look more like densely populated interferences. The modes are closely spaced and the response looks like it has a lot of little ups and downs closely spaced. In small spaces, below about 50-80hz only a handful of modes are operating but they have huge detrimental effects. For example your space is really exciting a mode that coincides with that 8-9 foot dimension.

    I mentioned it might be the longest dimension but in seeing your space that might not be right. It might be the depth of your room. It might simply be the placement of speakers and mic that causes that to show up.
     
  14. Bone9

    Bone9 Member
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    Ah right I see. The room width is 10' 7.5" wide.
     
  15. Matthew J Poes

    Matthew J Poes Staff Writer
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    What’s the depth?
     
  16. Bone9

    Bone9 Member
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    Without measuring (currently at work) I'd say about 15'.
     
  17. Matthew J Poes

    Matthew J Poes Staff Writer
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    Interesting. Well sometimes certain rooms show strong unimodal behavior that doesn’t perfectly align with a specific dimension. Sometimes off by like 10-20% and sometimes it matches a different dimension. That’s just how the speaker/room/listening interaction works.
     

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