Please help me choose the best frequency response curve of my subwoofers

Discussion in 'Speakers' started by MuneebM, Feb 3, 2005.

  1. MuneebM

    MuneebM Supporting Actor

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    I currently have 2 subwoofers in my home theater basement: a 2500 cubic ft. room with padded carpet over concrete floors. My primary sub is an HSU STF-2 located in the front left corner of the room, and my secondary sub is a modified Dayton with an STF-2 driver located in the rear right of the room. I determined these locations to be the most ideal after trying different spots and plotting my 1/6th octave frequency response.

    Now, I'm pretty happy with the almost flat frequency response I'm getting out of these two subs, especially considering how difficult it is to do that with two very different subwoofers. However, I now have 2 different frequency response curves and I can't decide which one is best. The first one is when I set my AVR's (Yamaha RX-V2400) subwoofer distance to 2.0 ft, and the second one is when the same parameter is set to 10.0 ft, which is the distance determined by the Yamaha's YPAO auto calibration system.

    Here's the first curve, with SWFR distance set to 2.0 ft:
    [​IMG]

    and here's the second curve, with SWFR distance set to 10.0 ft:
    [​IMG]

    So, which one would you all choose? They both look nearly flat to me, with a few minor dips and peaks, which frankly I won't be able to do anything about short of buying a BFD. These two curves are currently my only options, so please try to work your suggestions around those.

    Thanks in advance.

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  2. Wayne A. Pflughaupt

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    There both pretty good, but I think the second one edges out the first. Be that is it may, I think I'd go with the one that sounds best, since they're so close.

    Regards,
    Wayne A. Pflughaupt
     
  3. Mike^S

    Mike^S Stunt Coordinator

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    Ya, the second one looks better to me as well. If you are using a Radioshack meter did you add in the correction values?
     
  4. MuneebM

    MuneebM Supporting Actor

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    Thanks guys, I think I'll go with the second one as it seems flatter to me as well.

    I did in fact use the Rat Shack SPL meter and I used the 1/6th octave spreadsheet available online that automatically adjusts the values with the corrections when it plots the chart.

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  5. Kevin C Brown

    Kevin C Brown Producer

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    All you're doing by adjusting the sub distance, is essentially adjusting for phase between the sub and mains. You also might try 6 ft and 14 ft, just to bracket the "best" setting of 10 ft. I do agree, the 2nd one looks smoother. Pretty good without a BFD! [​IMG]

    And if you want to be really rigorous, you could average all the points, and take the delta to the average of each point, and average those. (Kind of like an r-squared.) Basically, looking for error around the average. You'd want the tightest distribution of points around the average, or lowest error.
     
  6. Ryan Tsang

    Ryan Tsang Second Unit

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    another vote for curve #2. Ummm.....curves.....
     
  7. MuneebM

    MuneebM Supporting Actor

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    Thanks for the replies guys. I did another experiment over the weekend, I reduced the crossover on my Yamaha RX-V2400 to 60Hz and managed to get the following, even flatter, frequency response curve:
    [​IMG]

    I really like the way it sounds and even "feels" now, but the sad part about all this is that I will be getting rid of my mutated Dayton STF-2 later this week. My primary sub, the HSU STF-2 will be taking its place as the secondary rear sub. I am getting an HSU STF-3 to take the place of the HSU STF-2 as the primary front sub [​IMG] Although I'm excited to be upgrading subwoofers, I just hope the the HSU STF-3 primary front sub + HSU STF-2 secondary rear sub combination yields as flat, if not flatter, frequency response than what I've managed with my current (weaker) subs. I expect it will, but will have to re-measure this weekend. So, be on the lookout for another curve from me [​IMG]

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  8. Kevin C Brown

    Kevin C Brown Producer

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    I find it interesting that you, Mary (in another thread), and myself all get flatter freq response with 60 Hz crossovers instead of 80 Hz. (Or, whatever you were using.) Just interesting is all! [​IMG]
     
  9. MuneebM

    MuneebM Supporting Actor

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    Yes it is interesting. I was always using an 80Hz crossover because it's the so-called THX "recommendation". I never even tried anything else nor did I ever do the frequency response plot with any other crossover, until I read the following article and until another member over at AVS hinted that my mains seemed to be out of phase with my subs in the crossover region. I then experimented with 60Hz since my mains are pretty large speakers and I got the flatter curve [​IMG]

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