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driving passive Subwoofer

  • 15 September 2020
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I want to power an oudoor subwoofer as well as four outdoor "rock speakers." I have an older Sonos Connect and Sonos Connect Amp.  I also have an amplifier. The equipment I have is listed below. Can you help me figure out how to set this up? Should I get a new AMP? can that power all four rock speakers and the sub as well? Thoughts about how to set this up and whether I should acquire any new equipment.

The equipment I have is: 
this passive subwoofer https://www.osdaudio.com/products/speakers/outdoor/outdoor-subwoofers/in-ground-8-500w-outdoor-underground-burial-rated-subwoofer-gls8-green.html

and these outdoor speakers https://www.amazon.com/gp/product/B002KEKPC2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

this amplifier. https://www.amazon.com/gp/product/B06XDRZD3D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

thoughts about how i can best drive this? 

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Best answer by tracker 15 September 2020, 09:36

Two methods: (1) Use the Connect Amp to drive the 4 main rock speakers, 2 each in parallel to its speaker terminals, and take its subwoofer RCA-connector output to the Rockville amp, solely to drive that buried subwoofer.

But if that isn’t enough volume from the main rocks, or the Connect Amp starts to distort or overheat when you turn it up enough to be heard, then: (2) Use the Connect instead, plus 2 pair of RCA Y-splitters to drive *two* Rockville amps, one for the main rock speakers and the other for the buried subwoofer.  Use the crossover setting on your second Rockville amp to restrict the output to low-frequency.

(The reason not to try to do 4 rock speakers and 1 sub with just one Rockville amp is that, even if you can drive 4 rock speakers off 2 channels because you get 4-ohm impedance with 2x8 ohms in parallel, when you parallel the subwoofer with that, you’re likely to be below the impedance that amp can handle, it’ll overheat and poof.  Besides, even OSD shows a separate amp to drive their subwoofer, and since they make their own landscape speakers, they *could* have added a switch to change the impedance with the combo.  They didn’t.  Lesson to the installer…)

Personal opinion: Unless your garden is small, go straight to method (2).  The Connect Amp’s 55 watts/channel is not going to do much with moderately low-efficiency outdoor speakers, and unless it’s a walled garden, you’ll find that you need to radiate a *lot* of power, just to be heard over street noise and ambient party sounds.  Yes, you could buy a new Sonos Amp instead and *maybe* 125 watts/channel (plus the Rockville to drive the sub) will be enough.  But then what are you going to do with your extra zone player?  The only reason to try the new Amp is if method (2) would be “using up” your old Connect, which was normally slated for use elsewhere.  In that case, better to buy a new Amp with lots of features than to buy a new Port just to replace your “now-missing” Connect.

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Two methods: (1) Use the Connect Amp to drive the 4 main rock speakers, 2 each in parallel to its speaker terminals, and take its subwoofer RCA-connector output to the Rockville amp, solely to drive that buried subwoofer.

But if that isn’t enough volume from the main rocks, or the Connect Amp starts to distort or overheat when you turn it up enough to be heard, then: (2) Use the Connect instead, plus 2 pair of RCA Y-splitters to drive *two* Rockville amps, one for the main rock speakers and the other for the buried subwoofer.  Use the crossover setting on your second Rockville amp to restrict the output to low-frequency.

(The reason not to try to do 4 rock speakers and 1 sub with just one Rockville amp is that, even if you can drive 4 rock speakers off 2 channels because you get 4-ohm impedance with 2x8 ohms in parallel, when you parallel the subwoofer with that, you’re likely to be below the impedance that amp can handle, it’ll overheat and poof.  Besides, even OSD shows a separate amp to drive their subwoofer, and since they make their own landscape speakers, they *could* have added a switch to change the impedance with the combo.  They didn’t.  Lesson to the installer…)

Personal opinion: Unless your garden is small, go straight to method (2).  The Connect Amp’s 55 watts/channel is not going to do much with moderately low-efficiency outdoor speakers, and unless it’s a walled garden, you’ll find that you need to radiate a *lot* of power, just to be heard over street noise and ambient party sounds.  Yes, you could buy a new Sonos Amp instead and *maybe* 125 watts/channel (plus the Rockville to drive the sub) will be enough.  But then what are you going to do with your extra zone player?  The only reason to try the new Amp is if method (2) would be “using up” your old Connect, which was normally slated for use elsewhere.  In that case, better to buy a new Amp with lots of features than to buy a new Port just to replace your “now-missing” Connect.

going to try this, stay tuned!

 

hello! question: for option (2), do i need to get another Rockville amp? in any event, could you possibly explain a bit more how i should run the connections?

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Yes, another Rockville amp, just for the subwoofer.  See the diagram in your OSD subwoofer manual, which shows 2 amps.  I don’t draw pictures, so here it is in words:

Using speaker wire, both rocks + to red output screw-terminal of Rockville amp #1 & both rocks - to black output screw-terminal of Rockville amp #1.  Subwoofer + and - to red & black output screw-terminals of Rockville amp #2.  Sonos Connect Line out RCA jacks Left & Right each go to an RCA Y-splitter, e.g. 2 of these: https://www.amazon.com/dp/B01M1I3OFH/  .  And finally, two sets of male-to-male RCA-plug stereo cables (like the single one you are already using with your Connect, except:), each between one jack on the two splitters and the input terminals (red/white) on each Rockville amp.  Don’t forget to set the dials on the front of the Rockville amp you’re using with the subwoofer, as described in their manual.  (Sorry if it sounds confusing in words, but the basic idea is simple: split the left output and split the right output of the Sonos Connect so you’re sending the same signal to 2 amps.)

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Sorry to follow up on my own post @matomasulo, but it seemed like you might be a novice.  So one additional caveat: Even though the Rockville amps are specified in “Peak” power and not RMS (3000 watts my *ss), it’s still possible for you to burn out your speakers.  Normally this is not an issue, but outdoors you are more likely to be in a situation where you think, “that’s just too quiet” and crank it.  Before doing that at a party, try it when you are nearby the rock speakers and can actually *listen* to them while you slowly turn up the volume.  You will definitely notice a change in the sound quality when they get near their operating limits, and that’s when you should stop turning up the volume, quickly turn it down a notch, then note the level and always stay *below* that.  If it isn’t enough to fill your back yard with sound, you just have to get more speakers and another amp.  If it seems plenty loud to you at some point and you have not yet noticed any noises or harshness to the sound, that’s good -- don’t go farther just to find out, as you might regret it.  Maybe you already know this from your indoor speaker setup, so my apologies if this is like baby-talk.  Good luck!

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