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  • #16
    hears a couple noob questions that i have and rpb has brought them up ... my math gives me 3-6 db by paralleling the woofers but i'm losing 3-6 due to BSC ? what is the frequency are we targeting when we are talking about BSC ?

    in my thinking with this build and according P E's spec's is that i'm at 89db with the woofers and 90 with the mids and tweet . i thought that was a good starting spot .
    Paper Towers
    RS180P/28F surrounds
    Boombox

    Comment


    • #17
      BSC occurs gradually from 1k and is leveled off around 2-300 or so.

      In this application I think a full 6db is a bit much, 3 is probably more reasonable. Seems like what you have will be workable, but I believe the low end of the mid response will be subject to some baffle losses as well depending on where you cross. I also like to have a few extra db of sensitivity in the mid to work with for shaping and voicing if necessary, knowing it is easier to lower the level than stretch to meet with just enough.

      Edit: I just looked at the response graph of the rs125p and have no idea where they justify a 90db rating. The majority of its response is 86 at most..

      Edit Edit: I see rpb just pointed this out
      Projects:

      transcenD: http://techtalk.parts-express.com/fo...5035-transcend
      Summits: http://techtalk.parts-express.com/sh...75-The-Summits
      References: http://techtalk.parts-express.com/sh...-My-References
      Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

      Comment


      • #18
        Originally posted by filmslayer View Post
        i understand what your saying , but how did you get 86db ? the RS125P-4 are listed at 90db ...

        I'm looking at the omnimic response. It looks to be roughly 86dB in the 500hz to 1000hz range. For the woofers, I would go by the spl at 200hz. I don't know if omnimic, or the PE graph is 2.83 volts, but I assume so. The only part of the response higher than 86dB is the breakup, and that part of the range that will be rolled off. That leaves the mid output at 86dB in the range of interest, unless the x-over boosts it a little which sometimes can be done.

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        • #19
          Originally posted by filmslayer View Post


          front of speaker will be about 30" off wall and the TV will be sitting on top of it .

          How big is the tv screen? I've seen a 46" screen have a big effect on tonal balance. I made one once quite a few years back, and voiced it sitting out in the room on a 24" stand. It sounded the way I wanted. When I sat it on top of a 46" rear projection tv, and it sounded totally different. There was no gap between the baffle and screen. If you have a 5 or 6 inch gap, the effect might not be as dramatic. I'm not sure.

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          • #20
            i believe all PE's are now at 2.83 ... i know thats what the 125's show . i have a 42" flat screen . 2" gap at best ...
            Paper Towers
            RS180P/28F surrounds
            Boombox

            Comment


            • #21
              I made a sim with the woofers in series. This sim would be as if the drivers were mounted on a large wall. This was just give you an idea of the sensitivity issue, or lack of an issue. In your setup, some bass will roll off. The mid and tweeter in this sim can be padded down as needed. to match that roll off. I guessed some offsets.

              I tried woofers in parallel, but couldn't keep the impedance up.
              Attached Files
              Last edited by rpb; 03-27-2017, 09:27 PM.

              Comment


              • #22
                thanks rpb . i really need to study PCD so i can read them . its why i love Xsim . your sim has me concerned with the 3ohm dip at mid tweet cross . you seriesed 8ohm 180's ? i can get a couple more db by seriesing 4ohm's , i've already played with that sim . let me see if i saved it , not hars to change if i didn't ... i would need to buy woofers either way if the concept works out .
                Paper Towers
                RS180P/28F surrounds
                Boombox

                Comment


                • #23
                  seriesing the 4ohms really shows me what you're talking about ! i guess i need to rethink this . such a nice looking speaker with only 12 components .....

                  Paper Towers
                  RS180P/28F surrounds
                  Boombox

                  Comment


                  • #24
                    after a couple days thinking about this i've decided to move forward . i figure if it does not work out as a CC i'll stand it up vertically and test as a L/R main . also i've decided to make the baffle detachable so any work done on a box can be re-used if necessary . this will be the prototype XO ...

                    Paper Towers
                    RS180P/28F surrounds
                    Boombox

                    Comment


                    • #25
                      made saw dust today . back panel is braced in two spots behind the mtm box . the longer two braces are dry fit , need baffle cut to make sure the woofers fit and then more bracing will be added . i really wish i had some woodworking skills ....

                      Paper Towers
                      RS180P/28F surrounds
                      Boombox

                      Comment


                      • #26
                        Wow, that thing is huge! Looks like a good start. Is the baffle convexly curved or is that just the pic making it look like that? Be kinda cool if it was curved.
                        Projects:

                        transcenD: http://techtalk.parts-express.com/fo...5035-transcend
                        Summits: http://techtalk.parts-express.com/sh...75-The-Summits
                        References: http://techtalk.parts-express.com/sh...-My-References
                        Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

                        Comment


                        • #27
                          i haven't cut the baffle yet as i am gonna use 3/4 stuff for that . there is a small curve (warped scrap) but the pic makes it look worse than it is . OD is 36 x 10 x 11 , compared to my towers and the CC i am using now it is a lil smallish ...
                          Paper Towers
                          RS180P/28F surrounds
                          Boombox

                          Comment


                          • #28
                            small set back this morning , was getting my router out and dropped it snapping the 1/8" ply i was using for a circle jig ... uhg . searching now for something else to use ...

                            got most of my components ready and started to put the circuits together last night ...




                            Paper Towers
                            RS180P/28F surrounds
                            Boombox

                            Comment


                            • #29
                              a few more things . the 3/4" stuff turned out to be 1" and rather rough and weathered so i cut a baffle from the 1/2" stuff . my broken jig has the holes up to 5" (2.5 centered) so i can recess and cut the mtm . using 1/2" stuff does not give me enough to recess the woofers anyway so all i need to come up with is a way to cut the through holes . i got everything ready only to discover my drill is at work (sigh) . but everything has been measured 3 times and marked ready to go . i also got the XO twisted together ...
                              Paper Towers
                              RS180P/28F surrounds
                              Boombox

                              Comment


                              • #30



                                Paper Towers
                                RS180P/28F surrounds
                                Boombox

                                Comment

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