Tempest sub setup

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  • David R.
    Member
    • Apr 2003
    • 90

    Tempest sub setup

    Having some problems setting up a tempest sub in my room.

    the design is as follows. 175L tuned to 17.5hz w/ a 4" flared port with the center tube being 8"s long (Final length of 13"s), stuffed with approx 64oz's of polyfill. The enclosure is a 18" sonotube approx 47.5"s high. After sub displacement,amp displacement,bracing the net enclosure size is 176L's. Could the height of the enclosure cause any cancelation from standing waves inside? The stuffing filled most of the enclosure (Loosely).

    Using the Avia disc and the sub level tracks in the subwoofer setup section i set the sub to be approx 3-4db higher then the rest (Radio shack meter). When playing movies like star wars 1 or 2 , U571, etc the subs performance doesn't seem that great. While i can hear the sub playing i can't feel the bass as much as expected. I would of expected to feel the depth charges in U571. Same with the Pod race in star wars 1.

    I took some measurements with the radio shack meter.. These are corrected numbers.
    80hz - 72db
    63hz - 71.5db
    50hz - 71.5db
    40hz - 77db
    31.5hz - 77db
    25hz - 77db
    20hz - 71db
    16hz - 69db

    As you can see im getting a very large 6db jump from 40hz to about 25hz. I tried moving the sub away from the corner i originaly put it in, and also to the other side of the room and the 6db increase remained. I stuffed the port to make the enclosure sealed and found the same 6db increase.

    Im using the Dt300 amp to power it. with the EQ disabled, switches 1-3 off (Down), switches 4-6 on (up). Reciever is the Denon 2802 and the LFE is set to 0 (max).

    Idea's?
  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    #2
    Welcome to the world of concrete floors. I find similar things in my basement with the dual tempests yet the single shiva on the hardwoods upstairs shakes the floor which gives you the impression its louder then it really is.




    Comment

    • PMazz
      Senior Member
      • May 2001
      • 861

      #3
      The 6 dB hump is most likely room gain, and isn't really that bad (for sub freqs).

      With a low tune, you are simply getting accurate bass levels. If you're used to most small commercial offerings (that are tuned/EQ'd for exagerrated boom), you should give yourself some time to get used to what you've got now. If you still don't like it, retune the sub to ~25-30 Hz, or try the amp with the EQ enabled.

      Also, when calibrating with Avia, your speakers must be set to small. Avia makes use of bass management to send signals to the sub, not the LFE channel.

      Pete
      Birth of a Media Center

      Comment

      • David R.
        Member
        • Apr 2003
        • 90

        #4
        Pmazz, would there be any beneft to retuning it to 19-20hz with a 6"dia port??

        Comment

        • PMazz
          Senior Member
          • May 2001
          • 861

          #5
          Not much, that I can see. A 6" port is better for a Tempest, but only at high output.

          Did you try enabling the EQ? That would give you a fair approximation of a higher tune, w/o losing the very low end as much.

          Pete
          Birth of a Media Center

          Comment

          • Andrew Pratt
            Moderator Emeritus
            • Aug 2000
            • 16507

            #6
            David Derek asked to post this reply for you since he's haveing login issues...


            On another matter Andrew. I was trying to post a response to a post by David R. but the computer won't accept my username and password when I try to post. I'm about to head out for softball and will be out of town tomorrow so I was wondering if you could pass this information along to him about his Tempest and DT300. I'll try to troubleshoot my HTguide problems on Thursday. It might be my Mac with IE 5.1.6, who knows.

            Thanks in advance.

            >>>>>post below<<<<<


            By my reading of the DT300 manual, you have no correction and you have the filter frequency (rumble filter I think?) set to 23 Hz, which would start to cutoff bass below that point. There's a post by Dan Wiggins in the Adire forum on Harmonic Discord where he talks a bit about this. You also have the choice of 20 Hz and 18 Hz.

            000111 = 23 Hz
            000011 = 20 Hz
            000001 = 18 Hz

            I think if you use correction, the boost frequency is also the cutoff frequency, but I'm not sure.

            I don't have any specific recommendations, maybe Pete or Andrew can tell you if you should set it lower. I've only just started experimenting with my Tempest/DT300 in a 109L sealed cube (EZSUB21 kit).




            Comment

            • David R.
              Member
              • Apr 2003
              • 90

              #7
              Thanks andrew for passing that on, i assume thats from bob?

              This is funny, I actually just came across this after re-reading the dt300 manual. When you set the amp to no correction you also enable a sub-sonic filter with selectable points as stated above. But if i read the manual correctly (and my measurements) when you use the EQ the sub sonic filter is no longer enabled.

              I guess i will play around with the eq and sub placement.

              Comment

              • Andrew Pratt
                Moderator Emeritus
                • Aug 2000
                • 16507

                #8
                No it was from Derek in Sask.




                Comment

                • DerekO
                  Junior Member
                  • Apr 2003
                  • 3

                  #9
                  Trying again with Netscape 4.8. I'm running an old PowerMac and was using IE 5.1.6, apparently the forum software doesn't like it.

                  Anyhow I was the one that asked Andrew to forward what I was trying to post. I recently received a Tempest and DT300 amp as part of an EZSUB21 kit I bought from Bob at Creative Sound.

                  I got it hooked up over the weekend with my Axiom M60 mains and Denon 2802 and have been trying it out a bit. I haven't had much of a chance to measure beyond the initial calibration with Video Essentials but hope to do some more measuring this weekend, along with experimenting with the different bass boosts. I've seen some posts here and there, Harmonic Discord and Audiocircle, about the DT300 so I thought I'd try to pass on the little I know.

                  Comment

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