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  • XO/Filter confirmation

    After talking to PE "tech" support, which is a real experience in the narcissistic macabre', I am more confused than ever.

    Have a real simple situation. Working with what we have on hand.

    Have 1 4 ohm woofer PE #290-208
    1 4 ohm tweeter PE #264-1026

    Must have 8 ohms at the the output. They are wired in series now.

    Want a simple or better XO design if possible , or if cant since they need to be in series, confirmation that a 8-10 ohm poly cap between the - of the woof and + of the tweet will simply filter the tweet to ~4-5k mhz.

  • #2
    Re: XO/Filter confirmation

    your biggest problem will be your sensitivity issue, woofer = 80db, tweeter =93 db, series won't work.
    Last edited by craigk; 02-15-2014, 09:58 AM.
    craigk

    " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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    • #3
      Re: XO/Filter confirmation

      XOs don't work that way.

      Why not tell us what you're up to? NOT stereo? Just looking to build a single 2-way in a box? What's it being driven with? What will be its ultimate use? Have you listened to the ND90 by itself? Adding a tweeter into THIS mix may be way more trouble/expense than it's worth.

      There's basically no way to make this work and end up with a DCR near 6 ohms, except maybe just running a 15w 3-4 ohm resistor in series with the ND90-4.

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      • #4
        Re: XO/Filter confirmation

        Chris is right. But he never explained why that won't work. In a series circuit like you are trying to use there is only one path for electricity to follow. So the cap will block lower frequency signals from the whole chain (including the woofer). The order of parts in a series circuit doesn't matter. It is like the amp "sees" one big load, instead of three separate items.

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        • #5
          Re: XO/Filter confirmation

          I concur. No tweeter, and if you cold return the items, get a single 8 ohm nd90 and give us the box dimensions and we can whip up a contour filter or baffle step compensation circuit for you.

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          • #6
            Re: XO/Filter confirmation

            It could be done with adding a second 4 ohm nd90 as well, but it won't play twice as loud as one since it would be in series, unless you had enough power to give it double the watts you were going to give the single nd90.

            Typically we don't use 2 four ohm drivers to reach eight ohms, unless they are identical drivers. We just use filters to add infinite impedance to what frequencies we don't want the driver playing. Eight ohms in parallel with infinity is still eight ohms.

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            • #7
              Re: XO/Filter confirmation

              Originally posted by kknight View Post
              After talking to PE "tech" support, which is a real experience in the narcissistic macabre', I am more confused than ever.
              You can't wire a woofer and tweeter in series. If you need an 8 ohm load you need to start with an 8 ohm woofer and an 8 ohm tweeter.
              confirmation that a 8-10 ohm poly cap between the - of the woof and + of the tweet will simply filter the tweet to ~4-5k mhz.
              That's not how a crossover works. This explains:
              http://www.bcae1.com/xoorder.htm
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                Re: XO/Filter confirmation

                Dont where you guys are coming up with a ND90 driver. We have no such driver in question.

                We are working with what we have on hand.

                1 Goldwood GS-S650 4ohm woofer #290-308
                1 Vifa BC25SG15-04 4 ohm tweeter #264-1026

                They are wired in series now, raw. No XO (obviously) or filter caps. They DO WORK in series for 8 ohms at the output since they are in series.

                Thanks duanebro for confirming you cant add a cap to to limit the tweeter wired in series to 4-5k.

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                • #9
                  Re: XO/Filter confirmation

                  You have people hear with a high degree of knowledge and experience who are willing to help you design an above average speaker. Sarcasm and arrogance will probably prevent you from sound advice and valuable help.

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                  • #10
                    Re: XO/Filter confirmation

                    [QUOTE=kknight;1971743]Dont where you guys are coming up with a ND90 driver. We have no such driver in question.

                    We are working with what we have on hand.

                    1 Goldwood GS-S650 4ohm woofer #290-308
                    1 Vifa BC25SG15-04 4 ohm tweeter #264-1026

                    They are wired in series now, raw. No XO (obviously) or filter caps. They DO WORK in series for 8 ohms at the output since they are in series.

                    Thanks duanebro for confirming you cant add a cap to to limit the tweeter wired in series to 4-5k.[/QUOTE

                    take a look at your first post, #290-208, not the 308 that you changes it to. since you know so much, figure it out yourself. I will not waste any more time posting.
                    craigk

                    " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

                    Comment


                    • #11
                      Re: XO/Filter confirmation

                      Yeah, #290-208 is what you told us you had, initially. Anyway . . .

                      XOs don't work that way.

                      Why not tell us what you're up to? NOT stereo? Just looking to build a single 2-way in a box? What's it being driven with? What will be its ultimate use?

                      There's basically no way to make this work and end up with a DCR near 6 ohms, except maybe just running an 80w 3-4 ohm resistor pack in series with the Goldwood, and you won't have any output above 4kHz.

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                      • #12
                        Re: XO/Filter confirmation

                        What you aporently are looking at is the 2 drivers adding up to 8 ohms and if you measure it with an ohm meter you will get something close to that in resistance. What we are talking about here is the impedance which varies with frequency. In that case you will have 4 ohm loads at the amp at the low end (where the tweeter is not playing) and the top end (where the woofer has essentially dropped off). A cap at the tweeter will protect it but as the signal is ac it will effect the woofer as well. Without adding series resistance you will not get the 8 ohm load you are after. And putting a resistor in line with a woofer is generally not a good idea as it will be wasting power and heating up.
                        https://www.facebook.com/Mosaic-Audi...7373763888294/

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                        • #13
                          Re: XO/Filter confirmation

                          Originally posted by isaeagle4031 View Post
                          What you aporently are looking at is the 2 drivers adding up to 8 ohms and if you measure it with an ohm meter you will get something close to that in resistance. What we are talking about here is the impedance which varies with frequency. In that case you will have 4 ohm loads at the amp at the low end (where the tweeter is not playing) and the top end (where the woofer has essentially dropped off). A cap at the tweeter will protect it but as the signal is ac it will effect the woofer as well. Without adding series resistance you will not get the 8 ohm load you are after. And putting a resistor in line with a woofer is generally not a good idea as it will be wasting power and heating up.
                          Not quite...

                          If you put a woofer and tweeter in series without an appropriate series crossover, you should still measure ~6+ ohms DC, and the impedance across the frequency spectrum will always be at least that high. At low frequencies, the tweeter will be a pure resistance, so your impedance will be the DCR of the tweeter plus the impedance of the woofer. The problem with this is that up to half the power you put into the speaker at low frequencies will be wasted as heat in the tweeter voice-coil. Since the tweeter has such small wire for a voice coil, it will most likely burn up at moderate power levels.

                          At high frequencies, the woofer's inductance will act like a series inductor with the tweeter (and itself) and roll-off the high frequencies. Putting a capacitor in series with both drivers will high-pass both the woofer and the tweeter.

                          As everyone else has mentioned, a woofer and tweeter in series without crossover is not a good idea. You could use a series crossover, but a 4 ohm tweeter and 4 ohm woofer in series with an appropriate series crossover will result in a 4 ohm overall speaker. In an ideal series crossover, the components in parallel with the tweeter will pass the low frequencies to the woofer with zero impedance and the components in parallel with the woofer will pass the high frequencies to the tweeter with zero impedance. This means the system will remain "4 ohms" across the entire audio spectrum.

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                          • #14
                            Re: XO/Filter confirmation

                            Originally posted by isaeagle4031 View Post
                            What you aporently are looking at is the 2 drivers adding up to 8 ohms and if you measure it with an ohm meter you will get something close to that in resistance. What we are talking about here is the impedance which varies with frequency. In that case you will have 4 ohm loads at the amp at the low end (where the tweeter is not playing) and the top end (where the woofer has essentially dropped off). A cap at the tweeter will protect it but as the signal is ac it will effect the woofer as well. Without adding series resistance you will not get the 8 ohm load you are after. And putting a resistor in line with a woofer is generally not a good idea as it will be wasting power and heating up.
                            No Chuck, his tweeter is playing in the low end. It's receiving all of the bass energy too. Poor little tweeter, probably never knew what hit it.
                            Click here for Jeff Bagby's Loudspeaker Design Software

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                            • #15
                              Re: XO/Filter confirmation

                              Originally posted by kknight View Post
                              Dont where you guys are coming up with a ND90 driver. We have no such driver in question.

                              We are working with what we have on hand.

                              1 Goldwood GS-S650 4ohm woofer #290-308
                              1 Vifa BC25SG15-04 4 ohm tweeter #264-1026

                              They are wired in series now, raw. No XO (obviously) or filter caps. They DO WORK in series for 8 ohms at the output since they are in series.

                              Thanks duanebro for confirming you cant add a cap to to limit the tweeter wired in series to 4-5k.
                              Hmmmm.... I'd like to help, but from reading the thread I don't think you're very open to that. I would suggest that plan funeral services for your tweeter though, it will be gone very soon if it keep it wired in series with your woofer.
                              Click here for Jeff Bagby's Loudspeaker Design Software

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