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  • Basic crossover help

    A question with hopefully an easy answer. I've built plenty of speaker projects, most were from here on PE. Assembled crossovers of course, never understood the electronics... so now I've got some mini TB full-range drivers that I'd like to use in a little project, and it says that they recommended "the use of a 2nd order (-12 dB/octave) 150 Hz high pass filter" and I don't know how to make one, and there's no off-the shelf option here on PE. Would anyone here be able to help me with a parts list and schematic for this??
    TIA,
    JRD

  • #2
    Maybe a dumb question, but are you planning on playing them pretty loud (near-ish full power) and you're okay with them sounding noticeably thin?
    Or
    Would you prefer them to sound more full (at least similar to some of the nicer portable bluetooth speakers you can buy) and you're fine with listening with them nearby or at fairly low volume?

    The 150hz high-pass is mostly important if you need to crank them up pretty loud without making them distort too badly (or possibly break if they're beefy enough to break themselves).

    Sharing the speaker model/name can help get more accurate help for the crossover point, even things like 8ohm version or 4ohm version can make a pretty big difference for what parts you'll use.
    Either way, a crossover/HighPass that low-down will end up using some pretty large-value and expensive parts...just a headsup.
    Roughly guessing, something like a 120uF cap and a 3mH inductor-to-ground might work for some 4ohm speakers...though I think the official LR 2ndOrder HP for a 4ohm speaker is drastically different, like 120uF and 8.5mH or something.

    For example:
    Click image for larger version

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    But maybe not this, exactly...depends on the speaker model.
    My first 2way build

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    • #3
      Originally posted by LOUT View Post
      ...Sharing the speaker model/name can help ...
      What he said

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      • #4
        Maybe it is time to do a little basics learning. On the WEB, there are loss of basic AC/DC basic electronics classes. It is actually very easy. Then with a little background, you can delve into the various simulation tools and understand what they are talking about. Not at all trying to be harsh, but this hobby is engineering based.

        You can get a free tool like PSD-Lite and look at the various topologies, scroll the values around and see what it does to the response.

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        • #5
          Thank you guys. My mistake, thought I had included that info... They are the mini 4 ohm TB's, Model: T1-1925S Part # 264-944 Loud isn't really necessary, just max fidelity for what they can do. These will be used to recreate certain sounds for use in canine rehab applications.

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          • #6
            Originally posted by randogdavis View Post
            Thank you guys. My mistake, thought I had included that info... They are the mini 4 ohm TB's, Model: T1-1925S Part # 264-944 Loud isn't really necessary, just max fidelity for what they can do. These will be used to recreate certain sounds for use in canine rehab applications.
            That helps. How do you plan to power the speakers? You may be better off with a LLPXO (line level passive crossover). That is, you create the HP filter on the input to the power amp using small, low power XO components rather than at the power stage between the amp and the drivers.

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            • #7
              [QUOTE=Millstonemike;n1457170]

              Yes I thought about that, but for the set-up I need (small), I'm not sure I could do that, unless there's some stand-alone unit that would allow me to condition the line level signal first before it hits the amps. I'm going to primarily be running sound from my iPhone to something like this (Part # 320-361 ) that will then send the Bluetooth signal out to 2 small BT amps. So I don't know where in that signal path I could adjust the line-level output before it reaches those amps. I'm not using equipment that has onboard x-over adjustments, so (I'm guessing) it would need to be a (small) stand-alone unit, and I don't know if that's even a thing.

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              • #8
                For $9 per speaker, you could use a 125uF npe cap in-line w/the module and a #269-2144 (7.5mH) coil wired in parallel with (across) it.
                If THAT is co$t prohibitive, just the 125uF cap in series will only be $2/ea, but they'll only give you "1st order" protection.

                Either way will raise the module's lower end (-6dB point) up to around 400Hz. The phone company considers the "human voice" range to be 300 to 3000Hz.

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                • #9
                  [QUOTE=randogdavis;n1457172]
                  Originally posted by Millstonemike View Post

                  Yes I thought about that, but for the set-up I need (small), I'm not sure I could do that, unless there's some stand-alone unit that would allow me to condition the line level signal first before it hits the amps. I'm going to primarily be running sound from my iPhone to something like this (Part # 320-361 ) that will then send the Bluetooth signal out to 2 small BT amps. So I don't know where in that signal path I could adjust the line-level output before it reaches those amps. I'm not using equipment that has onboard x-over adjustments, so (I'm guessing) it would need to be a (small) stand-alone unit, and I don't know if that's even a thing.
                  If you already know the amp you'll use, we can calculate a 1st order HP based on it's input impedance. For example, the popular TI TDA3116 chip set to 20 dB gain has an input impedance of 30K ohms. A .033 uf cap(s) in series with it's input(s) will give you a 1st HP with an Fc of 161 Hz. You can model that effect on the woofer's excursion in WinISD. After setting up your woofer model, input power in the projects "Signal" tab. Then look at the excursion graph. Next, input the a 1st order HP @ 161 Hz in the filter "tab". Then look at it's effect on excursion, transfer function, etc.

                  You can change the filter Fc in WinISD to minimize the effect on the transfer function low end while maintaining excursion within limiots. And rmember, there's very little content below 40 Hz in most music.

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                  • #10
                    Originally posted by randogdavis View Post
                    Yes I thought about that, but for the set-up I need (small), I'm not sure I could do that, unless there's some stand-alone unit that would allow me to condition the line level signal first before it hits the amps. I'm going to primarily be running sound from my iPhone to something like this (Part # 320-361 ) that will then send the Bluetooth signal out to 2 small BT amps. So I don't know where in that signal path I could adjust the line-level output before it reaches those amps. I'm not using equipment that has onboard x-over adjustments, so (I'm guessing) it would need to be a (small) stand-alone unit, and I don't know if that's even a thing.
                    If you're using bluetooth amps, then I don't think that device you linked should be necessary...you'd just link the phone's bluetooth right to the bluetooth amp/s, which would make an inline HighPass filter difficult like you mention.
                    BUT
                    If you'll be using non-bluetooth amps and that linked device will be wired to the amps so it can recieve the phone's bluetooth signal, then you'd just add the tiny capacitor inline with the aux wire between the device and the amps....Like Millstonemike mentioned.




                    Originally posted by randogdavis View Post
                    These will be used to recreate certain sounds for use in canine rehab applications.
                    A couple possible alternatives:
                    Check if the sounds you'll be recreating even have low frequencies like rumbles or bass notes (if unsure, maybe try listening to them on a full-range system or with a subwoofer).
                    Might not even be an issue at all if you're lucky.

                    If you or someone you can talk to is in charge of organizing the sounds onto a playable source/player, it might be worth trying to EQ the sound clips themselves...turning down their bass so you won't need anything physical inline to do it for you.

                    These will only work if the same clips will keep being used, since any new clips added for use later would need to be tested or EQ'ed.
                    So a physical capacitor would allow easier changing of the sound clips in the future if that might be part of this.
                    My first 2way build

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                    • #11
                      Yes thank you. I'm exploring the option of using an app on my phone to apply a high pass, then re-save the file, and then play the modified file. I may have found an app that will work for this, going to experiment with that next, so thank you. Then I just need to find out if I can use my phone to talk to both BT amps at the same time or not. If so, that would cut the expense and complexity of the system down quite a bit.

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                      • #12
                        I don't think the phone itself will let you connect to multiple bluetooth devices at once, but some bluetooth amps/speakers will connect to eachother for Left/Right channels, while others can continuously daisychain to eachother....but those are features of the bluetooth-amp, so you'll need to keep an eye out for that feature when choosing.
                        My first 2way build

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                        • #13
                          Good to know. I'll see if PE carries any mini amps like that which have those features. I did get the phone app to work, so I can pre-filter all audio now so that the signal leaving my phone won't be an issue (no low end below 150).

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