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  • Need help with finishing speakers

    Here is what I have:

    1. Speaker cabinets with internal volume of 0.118 cu ft. They have cutout for RS100 drivers and port (1.92" diameter). The boxes have the following dimensions: 5.5"W x 11.75"H x 8"D and are built from 1" MDF. The cabs are also lined with 0.5" foam.

    2. Pair of RS100S-8 drivers

    What I would like to get help with, is:

    1. Determining port length

    2. Should I install cap to limit the lows going to the driver?

    3. Should I put polyfill in the cabs?

    Sorry for those probably silly questions for you guys but I am noob when it comes to speaker building. The setup would be used as my computer system. Listening distance about 2 feet. Powered by 2x45W gainclone amplifier based on LM3875 chip that I built myself. Mostly low listening volumes as this setup is going into my office. No subwoofer. I know that the cabs are most likely not a good match for the RS100 drivers but that's what I have. Once I can complete the speakers, they will most likely sound a lot better than my current mono radio anyway.

    Thanks.

  • #2
    Re: Need help with finishing speakers

    ?1 - WinISD thinks 15", so . . . you'll have to neck that port down to 1.25"i.d., and make it 6" long. You're right, those boxes are WAY too small. You should get about a +4dB "lift" around 125Hz, sorta like baffle step compensation. Probably have bass down to 60Hz or so, which they should be able to take 24w down to.

    ?2 - I wouldn't bother.

    ?3 - I wouldn't bother, but I wouldn't bother less than ?2.

    For the next time, 1" thick walls are unnecessary on a box this small. Learn to use a box modelling program like WinISD from www.linearteam.org . It's free, and it's easy.

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    • #3
      Re: Need help with finishing speakers

      Chris, not being snotty or anything, but will the RS100S-8 in that enclosure handle much more than 30 watts anywhere? I'm too lazy to run the numbers...laundry again.

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      • #4
        Re: Need help with finishing speakers

        24 is the valley above tuning. It'll take full power higher, and again around Fb, then hits the bottom line again just under 60Hz IIRC.

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        • #5
          Re: Need help with finishing speakers

          Thanks for your help guys. I can't do any real woodworking so I bought the cabinets. Thank you for replying with some simple math like 1.25"x6" since the rest of the conversations is WAY beyond my knowledge.

          I just have one question. Considering that the depth of the cabinet is 8" and the port is 6" long, that would leave only 1" of space between the end of the port and the back wall. I guess that's OK?

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          • #6
            Re: Need help with finishing speakers

            It'll be OK.

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            • #7
              Re: Need help with finishing speakers

              Going to chime in on this one.
              Reality is that small full rangers like RS-100 run out of x-max in a split second. Modeling is good but a bass guitar solo will send the voice coil former and cone in two opposite direction. Having more output a bit over 100hz will create an impression that (in essence 2" driver) has some output down low. 1" space between the back of the cabinet and the port end is OK but I would make the port shorter too. 3", may be 4".
              Stuff the cabinet with pillow stuffing or similar. The mid-range will fire through the port and by stuffing the cabinet you will make the loudspeaker sound a bit cleaner. It's easy enough to take the stuffing out at a later point if you don't like it.
              I've also used a series notch which was 12mfd/6ohm/.33mh (have to check).
              This http://www.parts-express.com/pe/show...number=310-300 makes a nice addition for a table top system and the FR can be adjusted very quickly.
              PS keep the stuffing away from the end of the port.
              http://www.diy-ny.com/

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              • #8
                Re: Need help with finishing speakers

                Thanks again for the replies. I guess since port tubes are cheap, I can try both solutions and find out which one works better. I also have left over stuffing from my previous project so I can try that as well.

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                • #9
                  Re: Need help with finishing speakers

                  your other option would be to block the port holes and run them sealed.
                  Jeff

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                  • #10
                    Re: Need help with finishing speakers

                    I have plugged in the RS100 parameters and box dimensions into WinISD (please remember that I have no idea what I am doing) and got two curves. Yellow for closed box and blue for vented box (port 1.25"x6"). I do know that they are slightly different but could somebody explain to me why would one be better than the other?

                    WinISD plot

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                    • #11
                      Re: Need help with finishing speakers

                      Well, the best version of WinISD to start with, is called the "beta" version. It's a LOT easier to use.

                      However; the "Pro" version (a.k.a. "alpha") would show you a graph showing the woofers excursion at various power levels. Basically (in YOUR situation) they'd both take about the same amount of power, except, that a vented box can take more power around its tuning freq. - in this case, maybe 60Hz or so. I say, put in the port, and later experiment with plugging the vent if you want.

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                      • #12
                        Re: Need help with finishing speakers

                        Thanks for the explanation. Now, I just need to find a nice port tube and assemble the speakers.

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