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Has anyone ported a P1

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  • Has anyone ported a P1



    I was curious to know if anyone has tried porting a Rodgers P1 to enhance the bass response. The port size and length calculation is no problem I just wanted to know if it was worthwhile to make the effort. I was going to move my cabinet and flip it so that the cone faces down to a concrete slab and then space it off the floor empirically since I am remodelling my studio this Summer.</P>
    <P mce_keep="true"></P>


    Regards,</P>


    Charles</P>

  • #2
    Re: Has anyone ported a P1



    Never heard of porting one of those. I service a church that had one and it too was directed down to the floor with legs attached to hold it up. There were two 50 pound sacks of concrete laying on top of it. I asked what that was for and was told that the cabinet moved around with loud pedal notes. [:)]</p>

    Geo
    </p>

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    • #3
      Re: Has anyone ported a P1



      Thank you for your reply. Do you recall how far above the floor the face of the speaker was elevated.</P>
      <P mce_keep="true"></P>


      Thanks </P>


      Charles</P>

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      • #4
        Re: Has anyone ported a P1



        From memory I believe it was around a foot.</p>

        Geo
        </p>

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        • #5
          Re: Has anyone ported a P1



          Hi,</p>

          Is the P1 the big box with a 30" (Electro-Voice ?) driver in it?</p>

          What exact enhancement are you looking for? Bass extension (lower frequency response)? Greater volume?</p>

          My guess is that with a driver that big in a box that big, porting it probably won't be of benefit.</p>

          AV
          </p>

          </p>

          Comment


          • #6
            Re: Has anyone ported a P1



            Here are the Thiel-Small Parameters so you can do some estimating on performance in various types of enclosures.</P>
            <UL>
            <LI>Fs = 16 Hz</LI>
            <LI>Qes = .3</LI>
            <LI>Qms = 2.61</LI>
            <LI>Qts = .27</LI>
            <LI>Vas = 210 sq ft</LI>
            <LI>No = 5 percent</LI>
            <LI>Vd = 84.3 sq in</LI>
            <LI>Sd = 562 sq in</LI>
            <LI>Xmax = .15 in</LI>
            <LI>Pe (max) 60 watts</LI>
            <LI>Zmax = 8 ohms</LI>
            <LI>Re = 4 ohms</LI>[/list]


            Note the maximum power is 60 watts; the efficiency is 99 db/1Watt at 1 Meter. (reflective of the very high No efficiency of 5%). Withthe high starting efficiency, and relatively low powerhandling capacity, you're looking at 116.8 dB (calculated) SPLwith 60 watts at 1 meter, not really all that high for 32Hz fundamentals in a very large church. (But probably enough punch for a home). </P>


            As Arie indicates, with a driver in a box as big as the P1, porting isn't likely to improve anything. Rodgers would have ported the enclosure if it would have helped, I'm sure.</P>


            Toodles.</P>

            Comment


            • #7
              Re: Has anyone ported a P1



              Wow you must have some studio to be looking for more punch from that big box unless it's a lot different than my P2.  According to some of the info I rec'd with my 340 it originally had a P1 but it must have been swapped out at some point in time.  I had it stored out in the garage for a while but finally talked my wife into letting me "try" it out inside.  It can certainly deliver a lot of punch in the house for both the 16' and 32' flues.  It's capable of rattling every window even upstairs.  I've fallen in love with the sound of it but I don't think I can convince my wife that it's a keeper even though I did use the phrase "religious experience" to describe the bass.  I had a 740B for a while with a P-16 that did a really nice job too.  It was a ported enclosure but probably 1/4 the size of my P2.  It would have been interesting to A-B test them out but the timing didn't work out.  I'd like to find something much smaller that does the job since I don't think my P2 is here to stay :-(</p>

              So what kind of room do you have for this P1 and what isn't it doing for you the way it's set up?</p>

              I also noted that you have an H1 and I'm so envious.  I've never heard one but just from the visual impact alone I've been keeping my eyes open for one of these.</p>


              </p>


              </p>
              Gary

              Current: Rodgers 340 "Special", Gulbransen Rialto K (Both Versions), Allen Theatre Deluxe, Rodgers Olympic 333, Roland Atelier AT70 (I hope)
              History: Rodgers 321B, Rodgers 740B, Gulbransen Theatrum, Hammond H-133, Thomas Malibu, Heathkit/Thomas Paramount

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              • #8
                Re: Has anyone ported a P1



                I have installed several P1's in a past life, we always tried to find a good solid cement wall or floor to aim it at, the theory was that you had to get the structure to move and wood would only move locally. Shaking cement was the only way to make it travel a distance. Most homes are all wood which makes the bass stay in the general area of the speaker butmillagewill vary according to the tuned sizes of the rooms. Anyway, to port a p1 would free up the cone in the speaker which would lead to failure in short order. The speaker expects to have the nearly air tight cabinet to provide "load" and allow for up to 100w ofbeautiful32' bass. I know that Rodgers spent a good deal of time getting the P1 cabinet the mostefficientispossible. When I installed one in my home I built it in the crawspace using cement blocks to create the chamber but still the effect is very localized as the rest of the house is wood :( but at least it's out of the way.</p>

                </p>

                </p>

                </p>
                Rodgers 205 pipe augmented
                Hammond 2305 w/145 leslie
                Midi on Everything!

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