Question

Best way to connect Amp to passive pass-through subwoofer?

  • 29 August 2020
  • 6 replies
  • 1012 views

I just setup 2x Dali Motif LCR speakers with a Sonos Amp. The Dali speakers are nice and precise, but they have almost no low-frequency capability. I dug up an old Jamo passive subwoofer that has stereo input with normal speaker connectors (eg it has 4 connector). It is designed to pass the sound to two satellite speakers ( i guess it has some frequency filter internally), so it also has 4 output speaker terminals.

Obviously I cannot connect it as a normal active sub, but I can connect it as a normal stereo speaker set.

So basically I have 4 speaker cables, and I am wondering if its best to connect all 4 to the speaker terminals on the Amp, or if I should connect only the subwoofer, and then connect the Dali speakers to the subwoofer.


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6 replies

Userlevel 4
Badge +12

Hi @ziphnor, thank you for reaching out.

To answer your question, the speaker terminals are meant for the Stereo wired speakers and not a 3rd-party Sub.

The bass sound will be routed to the Sub RCA port on the Sonos Amp unless a Sonos Sub was bonded to it.

You can try connecting the Jamo Subwoofer the way you’re thinking; however, it would be unlikely that it will work.

You can refer to this article Setting up your Sonos Amp for the impedance rating.

You can also contact our Sales team for in-depth recommendations for your setup.

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The bass sound will be routed to the Sub RCA port on the Sonos Amp unless a Sonos Sub was bonded to it.

 

Not true, if nothing is inserted into the Sub out port on the amp.

I suppose both wiring schemes can be tried, to see which one works/sounds best - easy enough to do.

Userlevel 4
Badge +6

To answer your question, the speaker terminals are meant for the Stereo wired speakers and not a 3rd-party Sub. The bass sound will be routed to the Sub RCA port on the Sonos Amp unless a Sonos Sub was bonded to it. You can try connecting the Jamo Subwoofer the way you’re thinking; however, it would be unlikely that it will work.

Ignorant.  Completely wrong, every single sentence.

To maintain the 8-ohm average loads, wire the Amp wires to the input of the sub, and the output of the sub to the Dali speakers.  In other words, just follow the (large, friendly) wiring diagram on the back/bottom of the Jamo sub!  The Motif LCR’s have a (claimed) frequency range of 78 - 25,000 Hz, so the fixed crossover inside the passive sub should work just fine. 

You didn’t say which old model Jamo, e.g. an old SW3 or an SW25 -- those models did not have any crossover frequency controls, so they sort-of-relied on same-brand speakers to create an even frequency response.  You should be just fine, except that the Jamo sub is probably a bit tame, with small-ish drivers, and also it’s more likely to fail -- even though passive -- than the Motifs.  You’ll hear it pretty obviously if its cones have detached.  The Motif LCR’s are very nice wall-mounts, and the Jamo is easy to hide.  You should have a great-looking, and decent-sounding, installation there!

 

To maintain the 8-ohm average loads

A question that may be irrelevant to the specific outcome:

Since the Sub, like the speakers, is passive, the amp will have to drive three speakers. Logically therefore, regardless of how they are wired, the load on the amp should be the same - it has to drive three speakers anyway. 

Unless - one way does not result in bass frequencies being fed to the main speaker pair and to that extent they draw lower power from the amp. This can be achieved if there is a cross over filter in the Sub - but can passive Subs have one with no power fed into them, or does a fixed crossover need no mains power? If not, the main speakers will draw the same power as before and the Sub will be additional load.

As I said, this may not be relevant because the Amp has enough power to cope with extra load of the Sub.

I would repeat what I said therefore - use the wiring scheme that sounds best.

Userlevel 4
Badge +6

@Kumar , the answer to your embedded question is “Yes, passive subs *can* have a crossover with no power fed to them -- it’s just like the crossover you might find ahead of the lowest driver of a regular multi-driver floorstanding loudspeaker.  Jamo passives definitely do have a crossover inside.  Because it’s of unknown crossover frequency, slope, quality and age, that militates for your answer, “try both and see”.  But the Jamo subs (8 ohm nominal) actually have two smallish speaker drivers inside them (which is how they are so thin) plus their circuit board, and the Motif’s (6 ohm nominal) also have two drivers for mid-bass plus the tweeter and their own built-in crossover too.  So there’s gonna be a whole mess of complex load going on, which militates for my answer, “follow the wiring diagram on the Jamo sub”.  Sure, the Sonos Class-D can almost certainly drive the sub & satellites in parallel.  But since Jamo (in theory) engineered whatever series-parallel circuit results, I’d use their connections.  Also using their crossover, one might get lucky preventing both sub and satellites playing the same frequencies at different distances, phase cancellation, bla bla bla. All taken together, thus why I suggested wiring as diagrammed on the sub.

 @ziphnor , if you try it both ways, be sure to post your results on this thread! It’s so sad when people get their answers and then don’t post follow-up for others to benefit...

With so many variables at play including the one that also has a bearing on the final pudding - where the speakers are placed with respect to each other and to the room, and room acoustics themselves - trying both schemes to see what sounds best is an idea reinforced. After all the proof of the pudding is in how it sounds.

And yes, feedback would be useful for others in future.