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  • 3 woofers, how do you wire them?

    I've seen a number of commercial speaker designs with 3 woofers. If these are 12-ohm drivers then they could be wired in parallel at 4 ohms, but what if you have a more typical 4 or 8 ohm driver? Two possible wiring schemes: either have have two in parallel and that pair in series with the third (at left in the drawing) or else two in series and that pair paralleled with the third (at right).

    Would each driver draw equal power? Is it better to add a resister as a "dummy" woofer, and do a series-parallel quad?
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    Last edited by Flint; 12-31-2009, 05:56 PM.

  • #2
    Re: 3 woofers, how do you wire them?

    Series/paralleling woofers essentially distributes the amplifier power to multiple speakers, mechanically creating a "larger" driver for the amplifier to power. So, you gain power handling and SPL, but lose space. Any system with two woofers in series will act essentially the same as one woofer, but with greater power handling (and more surface area, so with enough power, your max SPL rises.) A parallel woofer increases demand from the amplifier, so an instant gain in SPL is achieved, so long as your amp can handle it. Series/parallel combos do pretty much what I just described; while they are most "efficient" when you have four woofers, three will still gain 1w and max SPL. A dummy resistor is not recommended at all. Avoid it at all costs.
    I am trolling you.

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    • #3
      Re: 3 woofers, how do you wire them?

      Couldn't some of those speakers also have cross-over components in one or two of the woofers. Putting an inductor in series with one or two of the three woofers would allow one or two woofer to handle only the lower bass. Assuming there's a tweeter, isn't that what a "2.5" speaker is?

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      • #4
        Re: 3 woofers, how do you wire them?

        Originally posted by learn2turn View Post
        Couldn't some of those speakers also have cross-over components in one or two of the woofers. Putting an inductor in series with one or two of the three woofers would allow one or two woofer to handle only the lower bass. Assuming there's a tweeter, isn't that what a "2.5" speaker is?
        A 2.5 way is a 2-way with both woofers handling the bass duties, but nly one handles the mid/midbass duties. This is to compensate for baffle-step losses.


        As to the OP, I would not series 2 and parallel a third. The normal way to get the load is all in parallel or all in series, or go with a different number, and series/parallel in pairs.

        The other option, is dual-6 ohm DVC woofers. Ran in series/parallel with 3 drivers gives you a net 4 ohm load. I don't know how many are available with this spec-set anymore, but it probably is not many considering the 0.5-ohm stable amps out there for car-audio...
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        • #5
          Re: 3 woofers, how do you wire them?

          Originally posted by learn2turn View Post
          Couldn't some of those speakers also have cross-over components in one or two of the woofers. Putting an inductor in series with one or two of the three woofers would allow one or two woofer to handle only the lower bass. Assuming there's a tweeter, isn't that what a "2.5" speaker is?
          Sure, but let's assume this trio is the bass section of a 3-way tower speaker. The reason to have 3 is to fit available space on the baffle. Two larger woofers would be too wide, and 4 woofers would be too tall. Sometimes 3 is the best fit.

          What I have in mind is three 10's for an OB. I have my doubts about the drawing at the right, because it looks like the top woofer would draw more power than the other two. So maybe it's best to choose a 4-ohm driver and get a 6-ohm total, as shown at the left.

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          • #6
            Re: 3 woofers, how do you wire them?

            Originally posted by JRT
            It is a mistake to consider any of this without including the components of associated passive filters.
            Okay, but in this case the system is active. The woofers are wired directly to the amp.

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            • #7
              Re: 3 woofers, how do you wire them?

              Another thought;
              Make the third driver a DVC "sub", and create a 3.5 way.
              That way the wiring would be the same as 4 woofers, yet keep it only three drivers. Although, this would present more problems, and/or require a more complex cabinet design.

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              • #8
                Re: 3 woofers, how do you wire them?

                this is very simple the first question to be answered is what woofer do you have in mind. if it is 8 ohm wire 3 in parallel getting an equal 2.67 ohm load. then use 3 of these.


                http://www.newark.com/multicomp/mc14...tor/dp/28K6360

                these are 50 watt 5ohm resistors 3 in parallel are a 150 watt 1.67ohm resistor this gives you a 4.33 load to the amp. it will change qts a bit and you will spend some power on heat but the power spent allows deeper bass and is offset by the gain of 3 woofers in parallel. if you want 4 ohm woofers instead of 8ohm I got nothing. by the way here is a good 10 inch driver for your app.

                http://www.mcmelectronics.com/produc...-1555-/55-1555


                these are very musical woofers with high sensitivity 3 in parallel would be close to 100db before you add the resistor network. if you want to use more power then 300 watts per channel you could because you have the resistors. be really loud.

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                • #9
                  Re: 3 woofers, how do you wire them?

                  if you used the 3 woofers i mention in parallel they would be 2.67ohm and .33qts before the network of resistors after the network they would be 4.33 ohm and .52qts. the fs is 30hz and the vas is 348 liters due to 3 of them.


                  they could be in a 400 liter box for a q of .71 this means even if open baffle is not quite right a backless enclosure would be pretty good. they would play to a f3 of 40hz and a f6 of 30hz. truly good for music.

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                  • #10
                    Re: 3 woofers, how do you wire them?

                    Originally posted by Flint View Post
                    I've seen a number of commercial speaker designs with 3 woofers. If these are 12-ohm drivers then they could be wired in parallel at 4 ohms, but what if you have a more typical 4 or 8 ohm driver? Two possible wiring schemes: either have have two in parallel and that pair in series with the third (at left in the drawing) or else two in series and that pair paralleled with the third (at right).

                    Would each driver draw equal power? Is it better to add a resister as a "dummy" woofer, and do a series-parallel quad?
                    I think they do it with 3 dvc 8 ohm woofer. (series each to be 16 ohms, then parallel it would 5.33, equal power to all 3)

                    I'm pretty sure in your configs, 67% power would go to the 2 ohm pair, and 33% to the 4 ohm driver.

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                    • #11
                      Re: 3 woofers, how do you wire them?

                      Originally posted by Flint View Post
                      Okay, but in this case the system is active. The woofers are wired directly to the amp.
                      The goldwood dvc 10" subs, are basically dual 6ohm vcs, series each to get 12, then use 3 paralleled and you get 4 ohms.

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                      • #12
                        Re: 3 woofers, how do you wire them?

                        Originally posted by philiparcario View Post
                        http://www.newark.com/multicomp/mc14...tor/dp/28K6360

                        These are 50 watt 5ohm resistors 3 in parallel are a 150 watt 1.67ohm resistor this gives you a 4.33 load to the amp. it will change qts a bit and you will spend some power on heat but the power spent allows deeper bass and is offset by the gain of 3 woofers in parallel.
                        If the woofers were RS270's, all in parallel at 2.66 ohms, then in series with these resisters, that might work but some power is wasted. Of course some people add resisters to OB designs just to boost the Q, so there may be a benefit there. Higher Q will increase output at Fs, which is about 27 Hz.

                        Or maybe the question should be, can anyone recommend a value-priced amp that will handle a 2.66 ohm load? Maybe a pro amp with XLR inputs...

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                        • #13
                          Re: 3 woofers, how do you wire them?

                          Originally posted by Flint View Post
                          I've seen a number of commercial speaker designs with 3 woofers. If these are 12-ohm drivers then they could be wired in parallel at 4 ohms, but what if you have a more typical 4 or 8 ohm driver?
                          What the designer does is to decide on the desired load impedance and choose the appropriate impedance driver to get it by wiring the drivers either in series or parallel. OEM drivers are not restricted to the usual 4 and 8 ohm choices.
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                          • #14
                            Re: 3 woofers, how do you wire them?

                            In both circuits, one of the speakers will get 4 times the wattage of the other 2.
                            9 out of 10 British housewives can't tell the difference between Whizzo Butter and a dead crab.

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                            • #15
                              Re: 3 woofers, how do you wire them?

                              Originally posted by billfitzmaurice View Post
                              What the designer does is to decide on the desired load impedance and choose the appropriate impedance driver to get it by wiring the drivers either in series or parallel. OEM drivers are not restricted to the usual 4 and 8 ohm choices.
                              Well the AE Lambda series Dipole10 may have the ideal specs. It has dual 8-ohm voice coils. A trio could be wired at 5.33 ohms. The only downsides would be excessive weight (especially with 3) and cost. The SLS 10" woofer would help considerably with that, but it's 8 ohms.

                              As for whether the power distributes evenly with those wiring diagrams, are there any engineers in the house? Maybe this calls for a little empirical testing...

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