Higher frequencies still audible on my sub

Discussion in 'Archived Threads 2001-2004' started by jeff lam, Feb 11, 2002.

  1. jeff lam

    jeff lam Screenwriter

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    OK, heres the story.

    I received my tempest last week and will build a sonotube for it soon. However, I just sold my old sub and did not have anything to run the low end. So I decided to build a "temporary" sealed box for my tempest until I can get the sonotube project going(hey, I at least need something for bass). The design was 2 ft^3(yeah I know, my F3 is like 35 Hz) but I didn't want a huge box in my living room. Anyway, I was doing some testing with it last night with my stryke disc and noticed the tempest is still audible up to 800Hz(quiet though), and audible at the driver @ 1KHz. This is at my "Loud"(-30 on my receiver) listening level, still well below reference though(-16 on my receiver). Has anyone else noticed this with their tempest? I have a Yamaha receiver doing the crossover. All speakers are small and sub is on SWFR. I didn't have this problem with my previous sub(def tech prosub200TL) due to it having a 24db/octave slope. Does this mean I need an external x-over to get a sharper slope cascaded with my receiver's x-over?

    Overall, I'm pretty impressed with the sub so far. Even with the small sealed box, I get louder readings down low than I did with my def tech sub.
     
  2. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    Also, you might want to measure the output at 800Hz and compare that to say 80-100Hz. It should be quite a bit lower.

    Brian
     
  3. jeff lam

    jeff lam Screenwriter

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    Well, it is quite a bit lower. I actually did the test using the highest frequency that I could still hear from my listening position. It just happened to be the 8xx Hz tone(forget exactly what it was). I just thought that any crossover that has been set at 90Hz(I think its 12dB/octave) would be inaudible at around 300 Hz or so. I guess if you think about it it's correct. Figure at 90dB at 90Hz, 180Hz would be 78dB, 360Hz would be 66dB, 720Hz would be 54dB, 1440Hz would be 42dB. Isn't this correct? So how loud in dB does something have to be for a normal human ear to hear it?
     
  4. CarlDais

    CarlDais Stunt Coordinator

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    I have owned many Yamaha Processors. And the 90 HZ and it's shallower slope has been an annoyance. Many Rec'vrs have similar X-over problems. My soluiton over the years has been to utilize electronic external X-0vers. As an aside, this issue of x-overs....Lo-pass & Hi-pass is often times the source of poor room sound. Too many listeners complain of a poor sounding demo, or a certain sub sounding boomy...mushy....slow..... Often times it's not necessarily the fault of the Brand of sub or speaker. It is that paticular set-up's x-over & the speaker positions in that paticular room.
     
  5. Jack Gilvey

    Jack Gilvey Producer

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  6. Mark Krawiec

    Mark Krawiec Agent

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    actually, the threshold of hearing is 0 db around 1-5khz.
    threshold graph
    so, yea you need a fairly steep rolloff.
    interestingly, as you get older, well...
    actually, this curve is very interesting.
    a while back, when i started lurking these forums i thought most of you guys were nuts trying to get to 110-120db+.
    after looking at the curve-you can see that you can't even hear/feel 20hz under 60-70 db. the ear is that much less sensitive at 20hz.
    ...i don't think my wife will be sympathetic to another subwoofer project, however the genesis for another sub, i fear, has begun.
    first i gotta work on my mains though.
     

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