Subwoofer designs

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  • David R.
    Member
    • Apr 2003
    • 90

    Subwoofer designs

    Im trying to decide between a couple subwoofers & designs. The system is for 75% home theater and 25% music.

    The options are:
    1st: 135L Ported Shiva, tuned to 18hz (4"X16" port) w/ AVA250 amp.
    2nd: 175L Ported Tempest, tuned to 20hz w/ either AVA250 or DT300.
    3rd: 125L Sealed Tempest, w/ either AVA250 or DT300
    4th, SVS PCi 20-39. Yeah i know its not DIY but with the Canadian buck its sure a option .

    I still have to check to see if the 2nd option will fit LOL. For options 1 and 2 i was thinking of a Sono-tube design. The room is approx 1300cubic ft, fairly small.

    Opinions? Questions?
    thanks
  • Hank
    Super Senior Member
    • Jul 2002
    • 1345

    #2
    I built the 175 liter vented Tempest tuned to 17.5 Hz at Dan Wiggins' suggestion and used a 250-wattt plate amp. It never fails to drop jaws with movie excerpt demos, but sound good at lower level for music. Sorry, I don't have graphs to show.

    Comment

    • David R.
      Member
      • Apr 2003
      • 90

      #3
      Originally posted by Hank
      but sound good at lower level for music. Sorry, I don't have graphs to show.
      Hey hank, thanks for the response. Maybe im tired (been out in the sun all day today) but could you expand/clarify this comment a little better? Are you saying it doesn't sound good for music, or it does? I guess at 175L's you could block the port and have a sweet sounding sub for music . I get a Qtc of .64 for a sealed 175L tempest .

      I talked to chris at adire on friday and he suggested to tune it to 20hz.. But im thinking 17.5hz would work better.. The response ends up very close to the shiva design, its actually 2db louder at 20hz (i think? LOL).

      Are you using 1 or 2 ports in your design? if 1 i assume 4"? if 2 i guess 3"

      Comment

      • Hank
        Super Senior Member
        • Jul 2002
        • 1345

        #4
        The 175 L tuned to 17.5 Hz was a direct recommendation from Dan Wiggins and it works, and yes it works for music at well as HT. Most people need a combo, unlike the Grand Poobahs' music-only speaker designs on this forum (BTW, that's NOT a criticism ), so a dual-duty sub, which some may call a *compromise* does not sound bad on either HT or music. Go for it - it's very inexpensive, and the time eventually comes to quit reading, pondering, wondering, etc and just go make some glorious sawdust!

        Comment

        • David R.
          Member
          • Apr 2003
          • 90

          #5
          Hank does the 175L's include the driver and port displacement?

          Time to find some 18" sono-tube i think .

          Comment

          • Hank
            Super Senior Member
            • Jul 2002
            • 1345

            #6
            David, rule of thumb is volume is NET volume. A design's volume is the *free space* volume. You will add to the volume:
            1. Driver displacement
            2. Port tube displacement (cylinder volume formula)
            3. Volume of all braces you add to your design
            Add the total of 1, 2 & 3 to design volume and that's your gross volume.

            Comment

            • Andrew Pratt
              Moderator Emeritus
              • Aug 2000
              • 16507

              #7
              I'd build either the ported or sealed Tempest myself. The ported will go lower while the sealed won't bottom out in those extreme LFE peaks. If you're not listening to movies that loud (which I don't think you are) the ported would be my vote. If you want to feel what they're like drop me a line and I'll fire up mine for you one day after work




              Comment

              • David R.
                Member
                • Apr 2003
                • 90

                #8
                Well finding the sonotube wont be a problem.

                Still going back and forth between the shiva and tempest lol.. Half the time i say just do it! the other half i think do i need a 15" sub? the shiva should be big enough.. lol It is a small room, ~1200 cubic ft.

                Comment

                • Andrew Pratt
                  Moderator Emeritus
                  • Aug 2000
                  • 16507

                  #9
                  David given the price difference between the shiva and the tempest its hard to make a case for the shiva IMO....remember there's no replacement for displacement...a tempest ideling along will sound much cleaner then a shiva pushed to keep up.




                  Comment

                  • David R.
                    Member
                    • Apr 2003
                    • 90

                    #10
                    Originally posted by Hank
                    Go for it
                    Well its done, I ordered a Tempest and a DT300... Muwhahahhaaha..

                    So, hmmm, I wonder what else i have to do to get like a Adire t-shirt or something? HA

                    Comment

                    • David R.
                      Member
                      • Apr 2003
                      • 90

                      #11
                      Got the sonotube. As they say on Monster Garage, FREE BE!

                      Comment

                      • David R.
                        Member
                        • Apr 2003
                        • 90

                        #12
                        Hank, How long did you make your port? and what size? In Dan Wiggins design he says 1: 4"IDX13"L port. But when i do the math i get a 14.5"L port.

                        thanks

                        Comment

                        • Andrew Pratt
                          Moderator Emeritus
                          • Aug 2000
                          • 16507

                          #13
                          David a single 4" port is not enough for a tempest...even if is a flared 4" port IMO.




                          Comment

                          • Hank
                            Super Senior Member
                            • Jul 2002
                            • 1345

                            #14
                            David, I dug out my thread printouts and here is Dan's advice:

                            "For good "tight" sound, a Q of 0.577 is often used. It's maximally flat in terms of phase rotation (group delay). But, for HT, you wnat pretty low Fc (down around 20 Hz or so). So, how's this:
                            175L per Tempest
                            64 ounces of stuffing
                            Tune to 17.5 Hz (4"ID by 13"L vent; note that our 4" flared vent kit would work well here - yes, that's a shameless plug...)
                            You'll have a response that:
                            Has an F3 anechoic of 22 Hz with the typical LFE crossover.
                            Is power limited to 500W above 15 Hz (for linear operation).
                            Mimics a 3rd order Q=0.577 Fc=20 Hz filter to +/- 0.25 dB down to 13 Hz.
                            Should provide a typical in-room F3 around 17 Hz.
                            Is capable of more than 110 dB SPL from 16 Hz and up, anechoic.
                            Is capable of more than 118 dB SPL from 17 Hz and up, in a typical room."

                            I estimated Dan used 15% internal volume increase caused by the 64 oz of polyfill stuffing - that gives an Lv of 13.05" So, I used an overall length of 14" on the dual-flare port tube. No "chuffing", no port noise and it continues to drop jaws.

                            Comment

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