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Preparing to build my first speakers and have some questions

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  • Preparing to build my first speakers and have some questions

    Hey gang, I recently picked up some Thiel drivers on ebay (from the out of business auction) and am planning a project with them. I'm not new to audio or fabrication but I AM new to speaker design. I'm designing a 3 way speaker using a Thiel (Scanspeak) 4" mid and am trying to come up with a good starting point for the high pass filter. The specific driver is this guy https://www.madisoundspeakerstore.co...m-drvm-060-01/

    I'm thinking 400Hz (2 octaves above Fs) is the minimum to keep the driver in its comfort zone. If I'm on the right track, this would require a woofer playing up to 400. I'd like as much woofer as possible so a 10" or even 12" would be great. However, I see no designs going from a 4" mid all the way down to a 12" woofer. Why is that? Is a 12" not capable of properly reproducing up to 400Hz or even a bit above? Thanks!

  • #2
    Didn't Thiel use 1st order crossovers in their designs? They got many good reviews in Stereophile.
    http://techtalk.parts-express.com/fo...khanspires-but
    http://techtalk.parts-express.com/fo...pico-neo-build
    http://techtalk.parts-express.com/fo...ensation-build

    Comment


    • #3
      All, or almost all of the speakers designed by Jim Thiel himself before the company was sold used first order crossovers. He believed this was a critical factor in getting the best sound. After the company was sold the new owners may not have continued the policy.

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      • #4
        They did. But they also used their own in house designed drivers. I actually had the pleasure of visiting the factory back in 2006 and meeting Jim. After his death and all the changes they started using almost off the shelf drivers - all the drivers from the auction are based on existing SEAS tweeters and Scanspeak mids and woofers with what appear to be minute tweaks. I'm waiting on the new DATS to confirm T/S params.

        Comment


        • #5
          About 98dB is all you can get out of those (15wRMS thermal rating). F3 near 150Hz in 0.04cf Cb, under 100 in 0.05cf Vb w/a 1"id x 4" long port.
          300Hz seems okay, 400 would be even safer.

          If you bought a box of those, I'd rec. an upper mtm w/about a 3/4" dome in the center, crossed near 4k. A pair of those, paralleled, will yield 6dB more output (104dB).
          W/the mid/top end output-limited, even a 10" woofer is probably overkill (wasted swept-volume).
          An RS225 (or equivalent) should do the job, I'd think.

          Comment


          • #6
            I have not modeled them and I'm sure there is more to it that just looking at freq. response, but both the rs225 and rs270 should work with the rs225 costing about 33% less. The breakup is supposed to be less on the p version. From experience, the 225 is a very good low end driver. I agree with Chirs on the 225, unless you're a bass head, then a wall of subs might not be enough.
            http://techtalk.parts-express.com/fo...khanspires-but
            http://techtalk.parts-express.com/fo...pico-neo-build
            http://techtalk.parts-express.com/fo...ensation-build

            Comment


            • #7
              Originally posted by Chris Roemer View Post
              I'd rec. an upper mtm w/about a 3/4" dome in the center, crossed near 4k. A pair of those, paralleled, will yield 6dB more output (104dB).
              W/the mid/top end output-limited, even a 10" woofer is probably overkill (wasted swept-volume).
              An RS225 (or equivalent) should do the job, I'd think.
              Yup, it's an MTM. I have 2 different sets of tweeters I can use (a Thiel branded SEAS 1" and a Hiquphon 3/4") but haven't decided yet on which it will be. And I'm leaning for a xover point in the 400Hz+ range.


              I'm not sure I understand why a 10" would be overkill though. Could you elaborate?

              Comment


              • #8
                Chris is saying that with a single mid driver, due to its limited volume output and thermal limits, that you would burn the mid driver before the woofer is even opening up to its output potential, hence two midrange drivers wired in parallel will gain 6 db of output, meaning make enough sound to keep up with a 10 inch woofer. Parallel will halve the impedance ie. Two 8 ohm parallel wires become a 4 ohm load but gain a 6 db sensitivy at the same amount of power input. Glenn.

                Comment


                • #9
                  ahh...I got it now. I was thinking the mid's ~87db matches just fine with most woofers' sensitivity. I didn't take into account the power required to get that output. Thanks.

                  Comment


                  • #10
                    Are you familiar with baffle step loss, and compensation for it in your crossover? That, along with the enclosure size and shape will have a major impact on choice and compromise. Do you know how to design crossovers, and do measurements of drivers, as well as measurements of drivers in the enclosure? How you will place speakers with regards to boundaries can impact the amount of baffle step compensation that you may want, based on how low frequency response is affected. Deep waters to jump into. Glenn.

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                    • #11
                      Originally posted by Drummer View Post
                      Are you familiar with baffle step loss, and compensation for it in your crossover? That, along with the enclosure size and shape will have a major impact on choice and compromise. Do you know how to design crossovers, and do measurements of drivers, as well as measurements of drivers in the enclosure? How you will place speakers with regards to boundaries can impact the amount of baffle step compensation that you may want, based on how low frequency response is affected. Deep waters to jump into. Glenn.
                      I am familiar yes - via ton of research in the past 6 months. So I would say I'm mostly well versed on the hypothetical side of things but I've yet to put any of it into practice so I don't have the benefit of real world experience. There is still some "book learning" I need to do and I have a checklist of specifics that I need to do more research on. I literally do 2-3 hours of research a night but there are some things I've just not been able to find satisfying answers on - like the mid to woofer transition. Properly matching power handling and sensitivity across drivers is one of those things I need to do a deep dive on.

                      Comment


                      • #12
                        What tweeter were you thinking?
                        http://techtalk.parts-express.com/fo...khanspires-but
                        http://techtalk.parts-express.com/fo...pico-neo-build
                        http://techtalk.parts-express.com/fo...ensation-build

                        Comment


                        • #13
                          Originally posted by Kornbread View Post
                          What tweeter were you thinking?
                          It will either be the Thiel H1715-06 which is almost a direct clone of the SEAS Prestige 27TBFC/G

                          or a set of Hyquphon OW1.
                          Last edited by GoodMusic; 11-15-2019, 09:42 PM.

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                          • #14
                            That last one is 2.5x as much as the first two!?! Passive or active? If passive, have you attempted to sim up the crossover for any of these drivers using supplied specs?
                            http://techtalk.parts-express.com/fo...khanspires-but
                            http://techtalk.parts-express.com/fo...pico-neo-build
                            http://techtalk.parts-express.com/fo...ensation-build

                            Comment


                            • #15
                              I'm not the posting police, but Parts Express doesn't want links to competitors posted. Maybe copy and paste photos rather than links.

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