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  • Bass Boost or Linkwitz Transform


    My sub presently has a 250W subwoofer amp without BASS BOOST. I could modify it as suggested by PE to get some bass boost. I've also read about a LINKWITZ TRANSFORM.

    1) Is bass boost and Linkwitz transform nearly the same?

    2) How does bass boost differ from Linkwitz transform?

    3) Will a 250w subwoofer amp with either have enough power?

    4) Anyone add additional capacitors to the subwoofer amp.

    5) Anyone use the subwoofer amp as source power for Linkwitz transform?

    Thanks

  • #2
    Re: Bass Boost or Linkwitz Transform


    > My sub presently has a 250W subwoofer amp
    > without BASS BOOST. I could modify it as
    > suggested by PE to get some bass boost. I've
    > also read about a LINKWITZ TRANSFORM.

    > 1) Is bass boost and Linkwitz transform
    > nearly the same?

    I'm not an electrical engineer, so my answer is most likely somewhat wrong, but they can both provide boost. A typical bass boost provides boost at one frequency and will generally also provide a rumble filter of sorts below that frequency. A LT is more of a contour circuit in that it reshapes the response to match a specific alignment so to speak. It is a more elaborate boost that is said to provide better transient response, but I don't know that for certain.

    > 2) How does bass boost differ from Linkwitz
    > transform?

    See #1.

    > 3) Will a 250w subwoofer amp with either
    > have enough power?

    That all depends on how much boost you want to provide and how loud you want to play. Which is also a function of the speaker and cabinet you have.

    > 4) Anyone add additional capacitors to the
    > subwoofer amp.

    > 5) Anyone use the subwoofer amp as source
    > power for Linkwitz transform?

    I think John Kreskovsky does this over at Music and Design.

    > Thanks

    Comment


    • #3
      Re: Bass Boost or Linkwitz Transform


      You can look at the info on Linkwitz transform circuits on the Rythmik Audio website. They sell add-on boards for their amps (which are very similiar to the PE 250 amp). I purchased a LT kit for a 350w amp Rythmik Audio amp I have. The kit provides the board and instructions for soldering connections to the pre-amp board on the amp. I have to determine cap and resister values for the circuit based on my driver and enclosure, solder the components onto the board and connect the board to the pre-amp board. The objective of the LT circuit is to provide a flat response down to 20 hz by boosting the response starting where the natural rolloff occurs based on driver and enclosure parameters. The sub amp has to have sufficient headroom to boost the response between the natural roll-off of the box and the flat response curve.

      Comment


      • #4
        Re: Bass Boost or Linkwitz Transform


        Hi DW - can this amp be setup to run fullrange (rather than with sub) with its transform? - just wondering how its sonics would fare in that mode.

        I've run one system with a Leach tranform that way but box wasn't set ideally for the speaker's Fc and Qtc. Ambiance retrival ability with transform added was welcome and the 18" didn't bottom out with 400W amp.

        Rhythmik also offers offset of Le by shelving - was this in your setup?

        Freddy

        Comment


        • #5
          Re: Bass Boost or Linkwitz Transform *PIC*




          Linkwitz and Marshall Leach's tranforms can "transform" one sealed box response to another by boost and if needed removal of peak around resonance.

          here's response of a Leach box - note boost and a dip

          room effects enter - haha


          Comment


          • #6
            Re: Bass Boost or Linkwitz Transform


            > You can look at the info on Linkwitz
            > transform circuits on the Rythmik Audio
            > website. They sell add-on boards for their
            > amps (which are very similiar to the PE 250
            > amp). I purchased a LT kit for a 350w amp
            > Rythmik Audio amp I have. The kit provides
            > the board and instructions for soldering
            > connections to the pre-amp board on the amp.
            > I have to determine cap and resister values
            > for the circuit based on my driver and
            > enclosure, solder the components onto the
            > board and connect the board to the pre-amp
            > board. The objective of the LT circuit is to
            > provide a flat response down to 20 hz by
            > boosting the response starting where the
            > natural rolloff occurs based on driver and
            > enclosure parameters. The sub amp has to
            > have sufficient headroom to boost the
            > response between the natural roll-off of the
            > box and the flat response curve.

            This is a really good read.
            <A HREF="http://www.rythmikaudio.com/sealed.htm">http://www.rythmikaudio.com/sealed.htm</A>

            Comment


            • #7
              Re: Bass Boost or Linkwitz Transform


              > Linkwitz and Marshall Leach's tranforms can
              > "transform" one sealed box
              > response to another by boost and if needed
              > removal of peak around resonance.

              I am not familiar with a Marshall Leach Tranform, can you point me in the right direction to learn more about it?

              Brian

              Comment


              • #8
                Re: Bass Boost or Linkwitz Transform


                Hi Brian - don't think info is online free:

                1990 reference is probably the one to find - 1981 must cover possibilities

                W. M. Leach, Jr., "A Generalized Active Equalizer for Closed-Box Loudspeaker Systems," Journal of the Audio Engineering Society, vol. 38, no. 3, March 1990.

                "Active Equalization of Closed-Box Loudspeaker Systems", W.M. Leach, Jr., J. Audio Eng. Society, Vol. 29, No. 6, June 1981, pp. 405-407.

                Comment


                • #9
                  Re: Bass Boost or Linkwitz Transform


                  > Rhythmik also offers offset of Le by
                  > shelving - was this in your setup?

                  > Freddy

                  Another new one on me. I looked on Rhythmik's website, but I didn't see anything about this concept. Could you give me a little more information on how this works?

                  Brian

                  Comment


                  • #10
                    Re: Bass Boost or Linkwitz Transform


                    > Hi Brian - don't think info is online free:

                    > 1990 reference is probably the one to find -
                    > 1981 must cover possibilities

                    > W. M. Leach, Jr., "A Generalized Active
                    > Equalizer for Closed-Box Loudspeaker
                    > Systems," Journal of the Audio
                    > Engineering Society, vol. 38, no. 3, March
                    > 1990.

                    Thanks for the information. If you have read it, could you explain the differences between Linkwitz's approach and Leach's or are they essentially identical?

                    I just finished my L & R's so I getting ready to do my sub next, that's why I'm asking so many questions. I don't want to get all done and then find I should have done something different.

                    Brian

                    Brian

                    > "Active Equalization of Closed-Box
                    > Loudspeaker Systems", W.M. Leach, Jr.,
                    > J. Audio Eng. Society, Vol. 29, No. 6, June
                    > 1981, pp. 405-407.

                    Comment


                    • #11
                      Re: Bass Boost or Linkwitz Transform


                      > Another new one on me. I looked on
                      > Rhythmik's website, but I didn't see
                      > anything about this concept. Could you give
                      > me a little more information on how this
                      > works?

                      > Brian

                      - not sure what shelving circuit they use to offset the effects of Le. you might ask

                      Comment


                      • #12
                        Re: Bass Boost or Linkwitz Transform


                        not seen the paper & didn't build this EQ box but from its response curve, Leach appears to serve the same general function as a Linkwitz transform

                        here's Elliots stuff on Linkwitz transforms

                        <A HREF="http://sound.westhost.com/linkwitz-transform.htm">http://sound.westhost.com/linkwitz-transform.htm</A>

                        Comment


                        • #13
                          Re: Bass Boost or Linkwitz Transform


                          > Another new one on me. I looked on
                          > Rhythmik's website, but I didn't see
                          > anything about this concept. Could you give
                          > me a little more information on how this
                          > works?

                          > Brian

                          I really don't know, but guessing, a shelving EQ that lifts the higher end would counteract the rolloff that Le produces?

                          If you use a box simulator that includes the effect of Re and Le, etc.. you can see this. Unibox for example, has a checkbox that will add or not add this effect to the response.

                          Depending on your crossover point, this might not be much to worry about with a sub...

                          Comment

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