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Will my sub amp run out of juice? (EQ - SVS)

Discussion in 'Archived Threads 2001-2004' started by ColinM, Feb 18, 2002.

  1. ColinM

    ColinM Cinematographer

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    I am running a 20-39CS off of an NHT SA-2, 165w into 4 Ohms. My response is -3.5db at 20Hz, and +3db at 40. Below 20 it drops like a rock, otherwise it's +/- 1.5db for the rest of the bass spectrum, so there won't be any REALLY big tweaks.

    Considering the boost I'll give at 20, does anyone think I'll clip the amp? I am not a ref-level type, maybe once or twice a month I'll demo for a friend, otherwise I keep the volume -20db. I do want it flat to 20Hz, since that's why the sub's there in the first place.

    I'll probably use something like the ART-351, since my problems are right at the band freq's, and I find these (and others) all over at good prices.

    Let me know if you need more info, and thanks in advance for any replies!

    - CM
     
  2. Ned

    Ned Supporting Actor

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    Your 165w amp will have the headroom of an 82w amp if you bump up 20hz by 3db. I add about 3db at 20 and 25hz with my ART351 and my Samson s700 often flashes the 3rd output light (-40db/-20db/Clip). Eq'ing subs up is definitely for those with bigger amps only.
     
  3. Rick Radford

    Rick Radford Supporting Actor

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    >Eq'ing subs up is definitely for those with bigger amps only.<
    Er, umm, methinks you mean if you BOOST! But if you do only cuts, no problem!
    But perhaps my inexperience is showing. I wonder how many EQ'ers boost and cut.. vs cut only?
    I do both, and have yet to see the red clip light on my S700... (remember, I said, "yet.") [​IMG]
     
  4. ColinM

    ColinM Cinematographer

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    FWIW, I'll be cutting that 3db @ 40Hz, so factor that.

    I don't have a clip indicator on my amp, wish I did.

    Thanks so far, but I'd like to hear some more....
     
  5. Dustin B

    Dustin B Producer

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    You don't gain any headroom buy cutting a peak. You do lose headroom by boosting a null however.

    The basic rule is every 3dB increase in output requires a doubling of input power. So like Ned said, 165W amp will behave like it has the headroom of an 82watt amp with a sub and room that was actually flat to 20hz.
     
  6. ColinM

    ColinM Cinematographer

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    Still sounds like I'd be fine with the 165w.

    Awhile ago Tom/Ron (I won't hold them to this) estimated the sensitivity of the 20-39 to be 98db.

    Since I don't push the envelope, even at 85w I'm good up to 118db or so.

    More than enough. Good deal. Thanks!

    But correct me if I'm wrong.......
     
  7. Dustin B

    Dustin B Producer

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    I think a 98dB/W/m sensitivity is a little optimistic and I really don't think a single 20-39CS can hit 118dB at 20hz no matter how much power you apply to it. For my justifcation for this statment see this review of dual SVS CS-Ultras:
    http://www.hometheaterhifi.com/volum...s-12-2001.html
    Here is a quote about the room conditions the measurements where taken in:
     
  8. ColinM

    ColinM Cinematographer

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    I guess that's kinda my point. I'm not saying I hit 118, by the way. I don't even try. On paper, that's where it comes out. And not limited to 20Hz output, either. I'm not trying to be overly analytical about this.

    Like I said, I watch movies at -20dBfs. Do you think I go to 118db? Nope. Wifey'd have my head. Looks like I can EQ in 3db at 20 to flatten it out and not melt the amp.

    2500 ft3, 10 feet from the corner-loaded sub in a 'live' room.

    Thanks for the answers, guys. This thread can die.
     
  9. Dustin B

    Dustin B Producer

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    Ok, I misunderstood you then. That being the case, try it. If things don't start to sound funny during heavy bass sequences in movies, you're a happy camper.
     
  10. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Just a quick note:

    I was asked about the CS *sensitivity*...I explained I had no idea but you could always back extrapolate from the Nousaine data.

    TN hit 114.9dB/31hz/2m/7500 room using the old fidek.

    This would be about 124dB/1m/2100 cu-ft room.

    TN commented that the FIDEK was never pushed near clipping so he thought our PC(with 180-190w)would perform about the same.

    So just saying he used about 240w for this example...

    240=124

    120=121

    60=118

    30=115

    15=112

    7.5=109

    3.75=106

    2=103

    1=100

    So in a average room,corner loaded...I figured it around 98-100dB 1w/1m at 31hz I guess.

    TV
     
  11. ColinM

    ColinM Cinematographer

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    TYVM, TV
    [​IMG]
     

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