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  • 3-Way builds, Impedance Matching Help

    I am wanting to build some 3-ways with the new Dayton RSS Paper cone... I would like to use the 7" 8Ω , the 4" 8Ω, and a Dayton Silk Dome 4Ω tweeter. Is this at all possible? I don't see that Dayton makes a RSS 8Ω tweeter, so I am trying to get some help with this. I have built subwoofers, and am currently building some now that I have a post about... But that said - I have never built a 3-way speaker. I'm a guitar and amp tech - so I understand a lot of the concepts, etc... but I don't have much experience with Crossovers. I have Xover Pro, so any advice (if my preferred drivers will work) on how to go about it would be greatly appreciated. Thanks so much for sharing your knowledge!
    Different Is Not Bad; It Is Quite The Same

  • #2
    Re: 3-Way builds, Impedance Matching Help

    Absolutely possible. with those drivers though a 2way is easily doable. I'm sure there are already a few people on here that are working on 2way designs with the 180p and rs28s. Not that a 3way couldn't or shouldn't be done, just that there may not he much benefit from it.

    Xover pro tends to want to throw a lot more parts at the xover than necessary.
    https://www.facebook.com/Mosaic-Audi...7373763888294/

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    • #3
      Re: 3-Way builds, Impedance Matching Help

      So, what program would do well at helping me design a crossover for a 2 way system other than Xover? Also, by 2-way, are you meaning to run the 7" and the 4" drivers in Parallel to create a 4Ω load for the crossover to see? Or are you meaning, cut out the 4" driver? I would really like to use all 3, if not unreasonable. I just think it would be nice to run a 3 driver setup, and I suppose I could do an MTM or 2 7" driver setup instead. I realize there are countless possibilities. I would just like to use these new Dayton Paper cone drivers in a project for a "reasonably" full range pair. Thanks so much!
      Different Is Not Bad; It Is Quite The Same

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      • #4
        Re: 3-Way builds, Impedance Matching Help

        "SpeakerBuilding 201" is a great book to start with.

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        • #5
          Re: 3-Way builds, Impedance Matching Help

          Very do-able. Use the Dayton RS28, the impedance will be raised when you pad it down to match the sensitivity. It is a very nice tweeter. You could make it a two as mentioned above, or use the 8" for the lows and the 4, 5, 6, or 7" for the mid.

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          • #6
            Re: 3-Way builds, Impedance Matching Help

            That brings up an interesting question for me to consider - why exactly would certain drivers be chosen in a 3 way design? In other words, in my hopeful idea of a 3 way with RSS 7", 4", and Tweeter... what is the thing or deciding factor between using say an 8", 5", and T, as opposed to 7", 5", T, or even 7", 4", T? What specs should I be looking for as far as frequency goes - how much overlap of the stock drivers' frequency capabilities ssfrom one drive to the next in a 3 way design? Also, should I be worried at all (if I chose to) intermixing the new Paper Drivers, with the RSS Aluminum Drivers" I realize that the RSS Paper drivers are very new, but what are the assumed differences between the paper formulation RSS, and the aluminum RSS?

            I know, I know, so many questions... but, this is the best way to learn - from others' experience. I have a neurological condition that does not allow me to comprehend the reading of books and the like. Shorter things like emails, forums, etc... I can take in if I read it a few times. Thus, I apologize on leaning on you guys for some advice, assistance, and guidance. But know that I always appreciate your input and feedback. Thanks!
            Different Is Not Bad; It Is Quite The Same

            Comment


            • #7
              Re: 3-Way builds, Impedance Matching Help

              About impedance

              First rule to remember is impedance is not "a number", it's a complex value that depends on frequency. That's why there's an impedance chart. The value chosen as the representative impedance (like 4 or 8 ohms) has to do with the typical profile of the driver as seen by an amp. At DC, the resistance will often be lower (example: 3.something ohms for a 4 ohm driver, and 6.something for an 8 ohm driver), and at the high end of the driver's useful frequency range, the impedance will rise towards infinity.

              The take-away here is that it's hopeless to try and match more than one driver's impedance because the system impedance won't be a straight line no matter what you do. You want the final curve to be above a certain lower threshold -- lower impedance comes closer to being a dead short, which is not friendly to your amp. Exactly how low you can go depends on how stout the output stage is on your amp. Typically, less than 3 ohms is dangerous. On an amp that wants an 8 ohm speaker, you want to stay above 6.

              The crossover components themselves will affect system impedance too. Whatever tool you use to model the drivers and crossover together, should also provide a calculated impedance chart to make sure the components are reacting well together. You'll often be padding down the relatively sensitive response of your higher frequency components (e.g. tweeter), which involves adding resistance or impedance to them, so having a 4-ohm tweeter is not really a big deal. It will probably no longer be a 4-ohm load when all is said and done.

              About driver materials

              Paper cones are known to behave a little better in general. Aluminum is great, but an aluminum woofer will likely have issues with cone breakup, where parts of the cone begin moving in a non-linear fashion, at the higher end of its range. The most common workaround is to cross over to the tweeter well below this point. How far below? The lower the better.

              You pick drivers for the strengths in the frequency bands you'll want them in. Nobody cares if an aluminum woofer has cone breakup issues at 6kHz, because that's usually at least an octave or so above the crossover point, and it'll be attenuated by 12-24dB by then anyway. The better designers will go ahead and notch out the really ugly regions with more exotic filters for good measure.

              If you build a three way where the woofer and tweeter could overlap well enough on their own, then adding a midrange with smooth response to either side of its passband is all the better. Every driver is well within its comfort zone and that makes crossover design easy. Many successful designs are not working with such ideal constraints, and may have to coax a driver to stretch its boundaries a bit, or to mask inherent flaws. With enough skill and practice, you can often turn coal into diamonds. To start out though, it's better to hunt for frequency response graphs that look like a highway in Texas -- flat as far as the eye can see.

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              • #8
                Re: 3-Way builds, Impedance Matching Help

                The speaker building bible sticky is a great place to start learning the basics.

                Comment


                • #9
                  Re: 3-Way builds, Impedance Matching Help

                  Originally posted by Buildsafire View Post
                  So, what program would do well at helping me design a crossover for a 2 way system other than Xover?
                  If at all possible, use Jeff Bagby’s Passive Crossover Designer. PCD uses actual acoustic measurement data along with actual electrical impedance data as the starting point. Then you add various crossover filters and PCD will show you very closely how it all will interact. (Both acoustically and electrically) No textbook crossover design even comes close to this level of optimization.


                  Originally posted by Buildsafire View Post
                  Also, by 2-way, are you meaning to run the 7" and the 4" drivers in Parallel to create a 4Ω load for the crossover to see? Or are you meaning, cut out the 4" driver?
                  “Two-way” design generally implies using a Woofer/Tweeter combo. Depending on the woofer’s diameter, you might crossover somewhere between 2,000Hz and 3500Hz.
                  Your phrasing above is a little off. It’s ok though, you’re new to this hobby. Maybe a short tutorial…

                  Here’s the quick summary:
                  The crossover filters will allow you to run all three 8 Ohm drivers in parallel, but because they are EACH only reproducing a PORTION of the audio range, the impedance remains at 8 ohms. Amazing huh? The technical explanation is much longer and dives into something called reactance (both capacitive and inductive reactance) but I’ll stop so that I don’t confuse you.
                  As a side-note, mixing and matching 8 Ohm drivers with 4 ohm drivers is fine as long as you are careful to not let the impedance (Z) go too low. It puts more stress on your amp when the Z is below 4 ohms. As you learn more, you’ll realize there are Z phase angles to consider also, but that stuff is way beyond what you need right now.


                  Originally posted by Buildsafire View Post
                  I would really like to use all 3, if not unreasonable. I just think it would be nice to run a 3 driver setup, and I suppose I could do an MTM or 2 7" driver setup instead. I realize there are countless possibilities. I would just like to use these new Dayton Paper cone drivers in a project for a "reasonably" full range pair. Thanks so much!
                  You will be very impressed with the results if you take the time to design and build them right. We’ll guide you the best that we can, but try to surf around this site and learn as much as you can from other designs too.
                  ~Marty

                  Baby Eidolons
                  Sapphos
                  Cables (Post #54)
                  Other speakers (Post #21)
                  Design Thoughts (Posts: 6,10,13,33,35)
                  Boundary Augmentation
                  Dispersion/Interference

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                  • #10
                    Re: 3-Way builds, Impedance Matching Help

                    Originally posted by Buildsafire View Post
                    That brings up an interesting question for me to consider - why exactly would certain drivers be chosen in a 3 way design? In other words, in my hopeful idea of a 3 way with RSS 7", 4", and Tweeter... what is the thing or deciding factor between using say an 8", 5", and T, as opposed to 7", 5", T, or even 7", 4", T?
                    Hmmmm, it’s tough to answer that. You’re diving into the more advanced topics without a solid grasp of some fundamentals. I’m impressed that you’re asking this type of question so early in your speaker building career. LOL.

                    3-ways are a bit harder to get right for beginners, especially the filters. Knowing how to manipulate the frequency and phase response of each driver such that they all “play nicely” is no easy task. If you have your mind set on a 3-way, I say go for it. We’ll give you some hints along the way.

                    Woofer size is usually determined by how big of a box you can deal with. Of course this is an over simplification, but basically… bigger woofer means bigger box, and deeper bass. I’ve built speakers that were taller than my wife, but they didn’t last long in our family room. (Just too darn big) So compromises are often made. For example: Two 8” woofers instead of two 12”. Or a bookshelf design instead of a tower design.

                    By now you probably realize that the speaker’s box volume is a key design aspect. You just can’t stick any old woofer in any old box. You need to optimize the volume of air inside the box if you want to get decent, clean bass.

                    Sometimes I run the box calculations in reverse. Instead of picking a woofer and then designing the “perfect” volume of air for its box… I might start with a rough idea of how big I want this speaker to be, then calculate the volume of air I have available… then I pick a woofer that will work perfectly in that volume of air.

                    As for midrange driver choices, the off axis responses will vary with larger or smaller diameter drivers. The term is often referred to as “beaming.” Think of a flashlight beaming its light out in a narrow cone. This tends to occur with speakers as the wavelength being reproduced starts to approach the diameter of the driver producing it. So running an 8” woofer up to 5,000Hz might not be the best idea. You’d be better off putting those frequencies on a 4” midrange or a 1” tweeter.

                    Attempting to acoustically integrate multiple drivers, (each physically separated by a few inches) can be a lot harder than it might seem. Keep the acoustic centers as close as possible to minimize constructive/destructive interference that results from path length differences. Remember, at the XO frequency BOTH drivers are producing sound. That leads to some complicated in phase/out of phase canceling depending on the geometry of the two sources.

                    If you decide to go 3-way, be sure to have a separate cavity for the midrange driver. The woofer will generate significant pressure inside the box and your midrange driver will more than likely be damaged unless it is isolated from this pressure.


                    Originally posted by Buildsafire View Post
                    should I be worried at all (if I chose to) intermixing the new Paper Drivers, with the RSS Aluminum Drivers"
                    You might get several different answers to this question. My opinion is that it’s fine as long as you address the cone breakup issues that are often seen with metal cones. (A simple notch filter is all that it takes. No big deal.)

                    Keep asking questions and have fun!
                    ~Marty

                    Baby Eidolons
                    Sapphos
                    Cables (Post #54)
                    Other speakers (Post #21)
                    Design Thoughts (Posts: 6,10,13,33,35)
                    Boundary Augmentation
                    Dispersion/Interference

                    Comment


                    • #11
                      Re: 3-Way builds, Impedance Matching Help

                      While it’s neat to use some new drivers in a build, it’s usually most satisfying to build a speaker for a specific use or need. What do you need? Where is it going, how big? What’s the budget? Are you ready to buy some measurement gear? There are some great completed designs that sound better than anything I’ve ever built, but I like the building, testing, retesting, rebuilding, tweaking, sharing, do better next time part...
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #12
                        Re: 3-Way builds, Impedance Matching Help

                        Originally posted by Buildsafire View Post
                        That brings up an interesting question for me to consider - why exactly would certain drivers be chosen in a 3 way design? In other words, in my hopeful idea of a 3 way with RSS 7", 4", and Tweeter... what is the thing or deciding factor between using say an 8", 5", and T, as opposed to 7", 5", T, or even 7", 4", T? What specs should I be looking for as far as frequency goes - how much overlap of the stock drivers' frequency capabilities ssfrom one drive to the next in a 3 way design? Also, should I be worried at all (if I chose to) intermixing the new Paper Drivers, with the RSS Aluminum Drivers" I realize that the RSS Paper drivers are very new, but what are the assumed differences between the paper formulation RSS, and the aluminum RSS?

                        I know, I know, so many questions... but, this is the best way to learn - from others' experience. I have a neurological condition that does not allow me to comprehend the reading of books and the like. Shorter things like emails, forums, etc... I can take in if I read it a few times. Thus, I apologize on leaning on you guys for some advice, assistance, and guidance. But know that I always appreciate your input and feedback. Thanks!
                        Picking drivers is a means to an end. Unless you want a big box, you have to decide what size box is too big. Then, if there is no sub to cover the lowest octaves, you have to decide how deep you want to be able to play. Then look at the handfull of woofers that can meet your requirements, and are within your budget, and see if they also can be stretched to meet the tweeter at 1.5k or so. If not, a 2" to 6" mid can be added. I like 5.25" mids, but smaller have some advantages depending on the tweeter.

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                        • #13
                          Re: 3-Way builds, Impedance Matching Help

                          Go to "Resource Index" at the top, right, of this TT page. Open the "Woofer Selection Guide" and start browsing. If you don't think you can build a vented box, look in the right hand columns for "Closed Box F3" (how low it will go), and "Closed Box Volume". 3 cubic feet is pretty dang big. 2 cu.ft. is smaller, but still not small. 1 cf is moderate size. Once you get down to 1/2 cf (or smaller), they're pretty small.

                          Many drivers (with a Qts value in the 0.30s, .40s, or even 0.50s) can be used in both closed AND vented boxes. If you can live with about double the box volume, and can install a port tube, you can gain almost an extra octave of bottom end extension.

                          Instead of just looking at columns of numbers, go to www.linearteam.org and get the FREE WinISD (start with the "beta" - non-"Pro" version). Only 3 parameters are required to design a box: Qts, Fs, and Vas. You can get these out of the data in the WSG.

                          Most guys learn box design 1st, and advance to crossover design later. If you don't have lots of time to learn, and lots of ca$h to blow on trial-and-error, and if you want something that sounds "decent" for your 1st build, find a "proven design" you can live with. A good, cheap, starter 2-way can be had using the 275-070 "Silkie" tweeter and the 295-305 6-1/2" "Classic" woofer. Good down to almost 40Hz in maybe 0.5 cf. This is the basis for PE's "BR-1" kit.

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                          • #14
                            Re: 3-Way builds, Impedance Matching Help

                            Lots of good advice above, look at the links to the right on this: https://sites.google.com/site/undefinition/
                            What size/volume/shape box are you looking for? The crossover will be different for bookshelf, on wall, or freestanding speakers. What is your budget?

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                            • #15
                              Re: 3-Way builds, Impedance Matching Help

                              Chris R. brought up a good point. Designing a box is pretty easy, so building subwoofers is a good introductory project. Building crossovers for 2/3-way speakers is quite a bit more complicated. The modeling capability is amazing these days, but there's still some trial-and-error involved due to real-world issues that aren't always compensated in the model, limited accuracy with measurement gear or technique, or human error along the way. For that reason, when you design a crossover and order the specific parts, you'll amost always find there's something that could be better... which requires another round of ordering parts and waiting for them to arrive. My last design took a few iterations of this, so it got drawn out over a month or so, and cost way more than the finished product would suggest. Although, I'm building up a collection of spare parts so I can avoid the round-trips next time. That's great if you're the type that will eventually do it all again, but if you're just going to build one and stop (haha! good luck), it might be better to go with an existing design.

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