New IB subwoofer with 4 Atlas 15's

Discussion in 'Home Theater Projects' started by Ryan Schnacke, Nov 7, 2005.

  1. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Last weekend I finally finished my IB subwoofer so I thought I'd share pictures and results.

    Here's the pics

    I used 4 Ascendant Atlas 15 inch woofers and I'm powering it with a single PE 250 watt plate amplifier. This is an amplifier that I already had laying around at the house, so it made sense to give it a try before spending more money. So far it does a fine job, though it does get warm after some especially powerful scenes.

    MikeNg asks:
    "What's the impedance on each of those Atlas'? Can the amp take the ohm load you're giving it? It might be working too hard."

    The Atlas woofers can be wired a number of different ways with their unique DVC configuration. Right now they're wired Hi-Q (gold terminals open) which means they're 4 ohms/woofer. I wired them series/parallel. This gives a single 4 ohm load to the amplifier.

    I did lots of measuring and dialed in the BFD equalizer this weekend. I tried to apply only the minimal amount of EQ to get it flat to +/- 3dB. You can see the results in the last pic. Roll-off on the upper and lower ends is due to filters in the plate amp. I'm now using one extra filter to play with different house curves - presently -8dB @180Hz, BW=90/60.

    It sounds great. I had friends over last night to watch Batman Begins and we were all thoroughly impressed. Certainly more powerful than the SVS 25-31PC that it replaces. I now have more sub headroom than I'll ever need. Sound quality is very good, too. It doesn't seem like its a quantum leap beyond the SVS (as you might be led to believe) but its possible that my ears just aren't good enough or I haven't had enough time to really tell the difference.
     
  2. ThomasW

    ThomasW Cinematographer

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    Your IB's performance is being handicapped by the 20Hz rumble filter on the amp. Remember that one of an IB's strong suits is low bass, something you're currently lacking. So change amps (or defeat the rumble filter) and discover real the potential of your IB.....:wink:
     
  3. MikeGee

    MikeGee Second Unit

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    I'm just learning all this stuff and seeing stuff like that is what got me hooked on this site. That looks awesome. What is to be expected from that compared to say my 5.5cu'f 15" Quatro? Cause my bass gets pretty damn deep. I can't imagine that.
    (just curious what IB actually stands for)
     
  4. ThomasW

    ThomasW Cinematographer

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    Infinite Baffle

    There is no real comparison. IB subs are in a league of their own... = best sound quality, and no sub plays lower (well except Bruce Thigpen's Rotary Sub and actually it's used in an IB)
     
  5. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Hmmm, hadn't really considered that. Maybe I'll take a soldering iron to it sometime. For now its nice just to have it done and it does have a subtle sound quality advantage over the SVS.

    BTW, now that I've calibrated it I'm quite impressed that there's no localization issues. Even with the manifold over in the corner and the XO at 80Hz I don't notice anything until I'm almost under it and with one ear facing the manifold. That's something the SVS couldn't quite manage given similar distances.

    Also there's very little sound leakage into the backyard. I did some experiments with my SVS that indicated that major boundaries reflect the majority of bass. Turns out that it works just as well in the attic. No worries about disturbing the neighbors.
     

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