Sub- down or front firing???

Discussion in 'Home Theater Projects' started by AndrewLevine, Jun 21, 2006.

  1. AndrewLevine

    AndrewLevine Stunt Coordinator

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    I found online some replacement parts for Klipsch's "SUB-12." I was thinking of picking up their 12" driver and matching amp for about $200 and building my own sealed enclosure. (I'd run to my local Best Buy and quickly measure their display Klipsch sub so I can get idea of proper enclosure size).

    I plan to use this sub for 90% music

    My Question: Should I make my sub front or downward firing? The real Klipsch sub is downward.

    Is there any advantage to one design over the other?

    [edit] Also, I just learned that the box is ported. If i make it sealed would that take away from musical sound quality, and if so, is it difficult to make a good port?

    Any input both welcomed and appreciated,
    Andrew Levine
     
  2. Brent_S

    Brent_S Second Unit

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    Down vs. front firing is usually just a matter of aesthetic taste.

    If the Klipsch sub is ported, then the driver is most likely optimized for that alignment. Putting it in a sealed cabinet, especially without knowing the proper size (need T/S parameters), would most likely yield disappointing results.

    Why not do something like the GR-Research SW12/PR12 combo: http://www.gr-research.com/drivers/sub_pr.htm Pair it with either a SA-240 or Bash 300 watt amp from Parts Express. $260-$280 in parts, but almost assuredly a superior solution to buying "replacement parts" and trying to reverse engineer the Klipsch without having full access to its cabinet design or T/S parameters.

    Another popular budget DIY solution is a Part Express Quattro 15" in 3 ft^3 sealed mated with the SA240 amp. $200 in parts with the Q15 on sale right now. Google should find you many a happy builder here, PE's boards, and at avsforum.

    Even if you had the blue prints for the Klipsch cabinet, I'd bet on a DIY solution using $200ish for driver/amp to be a superior solution. Assuming you have the tools and woodwoorking skills.

    There are many other driver and alignment options to consider as well, but we need to know more. What kind of SPL output do you need? How big a room? What type of music? What mains are you matching this sub to? Do you have a firm budget or is it flexible? Physical size constraints?

    -Brent
     
  3. AndrewLevine

    AndrewLevine Stunt Coordinator

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    Thanks Brent,
    Let me give you some more info to make things easier.

    =My current set up consists of a H/K AVR235 paired with a pair of Athena AS-F2.2's (supposed to go down to 35hz, but not enough bass for me)
    =My room is maybe 14' by 20' however it will go from dorm room to bed room which all vary in size.
    =I listen to all types of music, but mostly classic rock (I LOVE to FEEL the bass drum)
    =I listen to music pretty loud, general -10 dB (I guess 10 be low reference?)
    =Size is not much of a concern, tho a 15" driver enclosure seems a bit large
    =I'd like to keep the project around $250, hopefully not much more unless it would yield amazing results.

    I was looking at partsexpress drivers and like the idea of the dayton 12" high fidelity. It wants 400 watts rms, yet it said that people also purchased a 240 watt plate amp with it. That falls right in my budget, and I'd like a good quality, clear sound, but is this underpowered??? Would a larger driver (15" Quattro) sound better than a more pricey 12"?

    Basically, with SQ in mind and a budget of a total of $250, what would YOU buy?

    Thanks a lot,
    Andrew Levine
     
  4. Robert_J

    Robert_J Lead Actor

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    The 400w RMS rating means that it will handle a 400w countinuous sine wave. Has nothing to do with "what it wants". The amount of power to feed it depends on the alignment you choose and your listening habits.

    Pairing it with a 240w amp is not underpowering it. The difference between 240w and 400w is less than 3db. In the proper enclosure, that would be a great sub. The HF is one of the best SQ subs on the market now. Anything that sounds better would stretch your budget well past $250.

    -Robert
     
  5. Brent_S

    Brent_S Second Unit

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    Saying 10 below reference is only meaningful if what you're listening to was mastered to the same reference level and your volume control is calibrated accurately enough that -10 means something.

    Much more valuable would be using an SPL meter to record your average SPL readings at your listening position. For instance, using the THX trailer on "The Incredibles" DVD, my comfortable listening level peaks around 95db on the meter, but probably averages much lower. Even when I'm showing off, I barely break 100db...that's as loud as a lawn mower measured from 3'.

    Anyway, the 12HF is certainly a very nice driver. I've got one sitting in my office waiting for me to build it a cabinet. As Robert said, 400 watts is just the thermal rating for the voice coil before melting. The actual power handling is based on a given frequency in a given alignment. The biggest problem I see is with your budget...the 12HF and SA240 are $260 before shipping, plus you still need to build the cabinet, binding posts, port tubes, screws, etc. Do you have the skills and access to the necessary tools to build a cabinet?

    But, to quickly compare options using 240 watts of input in WinISD.
    RSHF12 in 4 ft^3 tuned to 20hz:
    106db @ 20hz, 108db @ 30hz, 109db @ 40hz
    RSHF12 in 2.25 ft^3 sealed:
    97db @ 20hz, 103db @ 30hz, 106db @ 40hz...excursion limited to less than 240 watts below 24hz.

    Q15 in 3 ft^3 sealed:
    98.6db @ 20hz, 105.8db @ 30hz, 109.5db @ 40hz...excursion limited below 30hz
    Q15 in 6 ft^3 tuned to 20hz:
    108db @ 20hz, 111db @ 30hz, 112db @ 40hz

    Room gain will usually add a few DBs to those numbers.

    Remember, the cabinet volume noted is net air space visible to the driver...meaning the internal volume of the cabinet minus driver, bracing, port tubes, amp, etc.

    A sealed cabinet is easier to build. A ported cabinet's tuning depends on the volume of air in relationship to the port size & length, so it's less forgiving of design to reality differences.

    For most music, good response into the mid 30hz range is sufficient. The lowest note on a Fender 4-string bass is 42hz, if I recall correctly. Most kick drums are in the 60hz range.

    Given your stated requirements, I think the Q15 would be the way to go, especially since it sounds like this is your first project. The RS12 is a better driver, but frankly, I don't think you'll be able to hear the difference in a dorm environment and the 12HF ported enclosure is going to be 25+% larger than the sealed Q15 for essentially the same output from 30hz up, not to mention the extra complication with the build.

    -wbs
     

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