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RS180-4 /optimal cabinet size - is bigger better?

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  • RS180-4 /optimal cabinet size - is bigger better?

    I want to replace the monkey coffin bass bin in a old 3 way design. (the original woofer is a morel 8" ~1.5cuft ) Since its very old build it has to be a moderately priced and complexity; plus its mainly for learning and sentimental purposes.

    These are my basic design parameters:
    The XO point is about 800 - 1000 (I am keeping the dome mid + ribbon tweeter)
    Cabinet can be up to 1.4 cuft (9"W)
    listening level will be moderate (low 90's max)

    I played around in WINISD with various RS and usher drivers, but the RS180-4 is catching my eye for under $50. http://www.parts-express.com/pe/show...number=295-374

    The model looks like it gives the deepest response in a 1.7 cuft box. In fact it models pretty amazingly flat to below 40. I can manage 1.4 cuft and that rolls it off only very slightly.

    Is this too big a cabinet? I've seen builds like the Statement Monitors that I believe use about .85 cuft tuned to 34hz. I've even heard a pair and they sounded very fine, but the model show a gentle rolloff starting at 60.

    The RS180 are modeling much better than the RS225's - does that sound right or have I done something wrong?

    Is bigger better?
    BEER: Proof that God loves us and wants us to be happy

    I've measured many things I cannot hear; and heard things I cannot measure...

  • #2
    Re: RS180-4 /optimal cabinet size - is bigger better?

    Originally posted by jeff_free69 View Post
    I want to replace the monkey coffin bass bin in a old 3 way design. (the original woofer is a morel 8" ~1.5cuft ) Since its very old build it has to be a moderately priced and complexity; plus its mainly for learning and sentimental purposes.

    These are my basic design parameters:
    The XO point is about 800 - 1000 (I am keeping the dome mid + ribbon tweeter)
    Cabinet can be up to 1.4 cuft (9"W)
    listening level will be moderate (low 90's max)

    I played around in WINISD with various RS and usher drivers, but the RS180-4 is catching my eye for under $50. http://www.parts-express.com/pe/show...number=295-374

    The model looks like it gives the deepest response in a 1.7 cuft box. In fact it models pretty amazingly flat to below 40. I can manage 1.4 cuft and that rolls it off only very slightly.

    Is this too big a cabinet? I've seen builds like the Statement Monitors that I believe use about .85 cuft tuned to 34hz. I've even heard a pair and they sounded very fine, but the model show a gentle rolloff starting at 60.

    The RS180 are modeling much better than the RS225's - does that sound right or have I done something wrong?

    Is bigger better?
    I don't know. The RS225-4 looks real good to me based on the posted specs.

    1.4 cubic feet tuned to 35Hz gives an F3 of 35Hz. That's your woofer. It can easily be pushed to 1000Hz, and it will have significantly more peak output capacity before the onset of distortion.
    R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
    Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

    95% of Climate Models Agree: The Observations Must be Wrong
    "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

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    • #3
      Re: RS180-4 /optimal cabinet size - is bigger better?

      There's not a lot of difference in the 8" & 7" as far as ultimate low reach is concerned. But the 8" will do it a lot easier, with more headroom for power handling, a bit higher sensitivity, and will definitely move more air. If you have the baffle room go with the RS-225.
      Lou's Speaker Site [speakers.lonesaguaro.com]
      "Different" is objective, "better" is subjective. Taste is not a provable fact.
      Where are you John Galt? I may not be worthy, but I'm ready.

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      • #4
        Re: RS180-4 /optimal cabinet size - is bigger better?

        You could also try modeling the Fountek FW168's as a driver under $50.00. I was modeling with 2 in 1.4 cubic feet and liked the way they looked. Also check what the excursion looks like in Unibox or another box modeler just to be sure you're not driving the model past X max.

        For the crossover do you know the efficiency of the driver you're replacing? Changing the driver may require you to change the mid and tweeter padding in the crossover.

        Take it easy
        Jay
        "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

        Breakfast Stout - HiVi RT2 II/Aurasound NS6
        Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
        Ruination 2.5 way - Vifa DX25/Fountek FW168
        Levitation TM
        - Vifa BC25SG15/Fountek FW168

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        • #5
          Re: RS180-4 /optimal cabinet size - is bigger better?

          Originally posted by Brewski View Post
          You could also try modeling the Fountek FW168's as a driver under $50.00. I was modeling with 2 in 1.4 cubic feet and liked the way they looked. Also check what the excursion looks like in Unibox or another box modeler just to be sure you're not driving the model past X max.

          For the crossover do you know the efficiency of the driver you're replacing? Changing the driver may require you to change the mid and tweeter padding in the crossover.

          Take it easy
          Jay
          Thanks I'll look at the Fountek too..

          The old Morel MW 266 is rated at 89db. I'm prepared, as part of the learning experience, to adjust the Mid / Tweets if needed. They are already padded down pretty much. A friend designed the XO long ago and the labels have fallen off some of the components, but now at least I have a cap & inductor meter.
          BEER: Proof that God loves us and wants us to be happy

          I've measured many things I cannot hear; and heard things I cannot measure...

          Comment


          • #6
            Re: RS180-4 /optimal cabinet size - is bigger better?

            I used the RS180-4 in my cenTiLana design, which is a mass-loaded TL. The gross internal volume of the cabinet was ~1.25 cubic feet. The cabinet's internal dimensions were 7.5"W x 9.5"D x 30"H, and within it was a single-fold TL 60" long. The modeled F3 was right at 32 Hz. Pete Schumacher did the crossover design, BTW. This was a 3-way: midrange RS52 dome and tweeter Vifa XT19. I'll attach some modeling graphs and cabinet drawing.
            Paul

            Couldn't attach the graphs because they were too large. If you're interested, send me an email and I'll send them to you.
            Attached Files

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            • #7
              Re: Here's the cenTiLana response graph...

              Originally posted by Paul K. View Post
              I used the RS180-4 in my cenTiLana design, which is a mass-loaded TL. The gross internal volume of the cabinet was ~1.25 cubic feet. The cabinet's internal dimensions were 7.5"W x 9.5"D x 30"H, and within it was a single-fold TL 60" long. The modeled F3 was right at 32 Hz. Pete Schumacher did the crossover design, BTW. This was a 3-way: midrange RS52 dome and tweeter Vifa XT19. I'll attach some modeling graphs and cabinet drawing.
              Paul
              Now I can attach the system response graph!
              Attached Files

              Comment


              • #8
                Re: RS180-4 /optimal cabinet size - is bigger better?

                Originally posted by LouC View Post
                There's not a lot of difference in the 8" & 7" as far as ultimate low reach is concerned. But the 8" will do it a lot easier, with more headroom for power handling, a bit higher sensitivity, and will definitely move more air. If you have the baffle room go with the RS-225.
                Yeah, in the same size cabinet, you'll get about the same F3, but the RS225 will get you like 10 dB more power handling!!
                Isn't it about time we started answering rhetorical questions?

                Paul Carmody's DIY Audio Projects
                Twitter: @undefinition1

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                • #9
                  Re: RS180-4 /optimal cabinet size - is bigger better?

                  Well, the RS180-4 is out of stock - until DECEMBER! So much for that temptation; I was intrigued by its very low, very flat graphs.

                  The RS180-8 is available, but that didn't model quite as well for some reason.

                  So the RS220-4 looks like a good (and more conservative) contender.

                  I also checked out the Fountek. It could be a fine sounding mid/bass, but it has less power and Xmax and extension.
                  BEER: Proof that God loves us and wants us to be happy

                  I've measured many things I cannot hear; and heard things I cannot measure...

                  Comment


                  • #10
                    Re: RS180-4 /optimal cabinet size - is bigger better?

                    Originally posted by jeff_free69 View Post
                    Well, the RS180-4 is out of stock - until DECEMBER! So much for that temptation; I was intrigued by its very low, very flat graphs.

                    The RS180-8 is available, but that didn't model quite as well for some reason.

                    So the RS220-4 looks like a good (and more conservative) contender.

                    I also checked out the Fountek. It could be a fine sounding mid/bass, but it has less power and Xmax and extension.
                    You won't regret using the RS225-4. Those 8" woofers are among the best you can buy for the range to 1000Hz. And you'll certainly get quite a bit more output than you would with the RS180.
                    R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
                    Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

                    95% of Climate Models Agree: The Observations Must be Wrong
                    "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                    Comment

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