Have questions about going the DIY sub route

Discussion in 'Archived Threads 2001-2004' started by BrianF, Nov 17, 2002.

  1. BrianF

    BrianF Stunt Coordinator

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    I was originally looking to buy an SVS PC+ 20-39 as recommended by Tom @ SVS. I am looking to save money and get performance rivaling an SVS or better of course. [​IMG] I have access to a box that houses a 15" and two ports. Internal size without taking into account the sub or ports is 4.29 ft^3. My room is roughly 1760 ft^3 with an opening to the rest of the house half down from the TV. I've been looking at the Tempest or Dayton DVC 15's to go into the box.
    My questions are...Can I get the performance I'm looking for from a box this size? How will these subs our similar perform for music and HT compared to an SVS? Any other suggestions for the driver besides the two I stated? I also see that a lot of people are using 250 watt plate amps. I will be needing an amp (not a plate amp) and is 250 watts enough power to get the concrete cracking performance or should I look for more power? Should I get a rumble or subsonic filter?
    I was also thinking of setting the box up to be downfiring. Is there a performance gain using a downfiring configuration? Does a baseplate increase performance? Oh and would a tune around 18Hz work well?
    Sorry for all the questions. [​IMG] Any help would be appreciated. Thanks.
    Brian
     
  2. BrianF

    BrianF Stunt Coordinator

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    I just saw this driver. How about the Lambda PB15? Would that work well in this setup? It does cost more than the other two I named. Would there be much of a performance gain if any?
     
  3. BrianF

    BrianF Stunt Coordinator

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    BUMP
     
  4. Craig Woodhall

    Craig Woodhall Supporting Actor

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    Brian,

    i don't have time to answer all your questions today, will respond tomorrow.. I don't know what your funds are like but you said you need an amp (not plate amp).. There is a guy selling a Fidek (SVS uses them) in the For Sale forum for $180 shipped and it is 200w/channel.. That 400 watts to a Tempest/Dayton will one up the SVS in the proper box..

    Craig
     
  5. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    I can take the questions in the last paragraph. No performance hit for down fireing, but not all drivers like to be horizontal. The tempest is fine. I'm not sure, but I think the lambda needs to be vertical. Bass plate does little if anything (some would disagree). 18 Hz is a fine choice for tuning.
     
  6. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    "Internal size without taking into account the sub or ports is 4.29 ft^3."

    4.29 ft^3 is about right for a sealed Tempest or DVC. You could probably seal it off pretty easy. But I think it'd be kinda tough to get a good vented alignment with only that much volume. Especially if the net volume after ports and driver is less than 4.29ft^3. Do you know the dimensions of the ports?
     
  7. BrianF

    BrianF Stunt Coordinator

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    Well the current ports are only 3" but I was looking at covering one hole and enlarging the other for a 6" port size. Doing some research on here I found that using 1 pound of stuffing per cubic foot in a vented box will give you about a 30% increase in volume. I was going to go that route but if I make it vented would I tune the port like the box is 5.5 ft^3 (approx. size with stuffing) or tune it like it is 4.29ft^3?

    I did end up ordering a DVC because Kyle at acoustic-visions said that it would work a little better than the Tempest in a smaller box. Is it better to power each voice coil with it's own amp channel or run them together off the bridged power from the amp?
     
  8. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    The stuffing "trick" is used mostly in sealed subs. So I'm not sure about the porting. It seems like you should use the effective volume. I'd want some way to experiment with different port lengths so I could measure the tuning for myself.

    If you run the amp bridged and the coils in series it is virtually identical to running one channel per coil. If you run the amp bridged and coils in parallel its 4 times as much load on the amp and potentially 4 times as much power output - if your amp can take it. Be sure the amp can push 2 ohms per channel/4 ohms bridged before trying this.
     
  9. BrianF

    BrianF Stunt Coordinator

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    Update:

    Well I ended up using the box I had and made it downfiring with a DVC 15" (VC's in parallel). I tuned the box with 3" ports to ~17-18 Hz and used ~ 64oz of polyfill. I originally was going to use a power amp but ended up taking the plate amp off my Infinity Entra sub. The amp is rated at 150W RMS/500W Peak at I believe 20-125 Hz. I like the auto on/off of the plate amps, although I wish it had a clip indicator on it.

    First off it's amazing what the 150 watt amp will do. It's plenty of power. The sub seems to blend very well with the main speakers. You really don't even know that it's there until you turn the sub off. I had to get used to it at first, I think because I'm used to below $500 commercial subs. The sound is pretty tight, not boomy and it does go low.

    I've been listening to it for a few weeks now. I can definitely recommend the DVC to anyone looking at DIY subs. My receiver is calibrated to 75 db with receiver volume at -15. I watched Minority Report and LOTR the other day. Nice! Minority Report has a very active LFE channel. I swear everything that happens in that movie uses LFE. LOTR is of course great. I haven't really done much measurements with my SPL meter but the beginning scene in LOTR with the big energy wave (after the ring gets cutoff and that dies) hit 120 dB at ~1 m.

    I'm going to build another one sometime but for now this will do. Maybe see how a sealed one will perform. Thanks for the advice guys. And for anyone thinking about going the DIY sub route. DO IT!!!
     
  10. Sean Carter

    Sean Carter Stunt Coordinator

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    If I were you, I would look into the Stryke AV12, or AV15. I have an AV15 on preorder right now.
     

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