Help connecting a passive sub to a amplified sub


Novice Member
Excuse the audio noobness.
I have a cheap 5.1 in a box package and the Yamaha HTR 2070 receiver has a passive sub connected (NS-SWP40) which has + and - wires on it only:
When i upgrade to a new receiver with Atmos (looking at Denon X3700H) it will require an active sub connected via RCA.

I have an old pc powered sub (Microlab M 800):

I want to use this one so i don't need to buy an amp or powered sub and also want to connect my passive sub to this as it's beefier so they work together. I also heard that having 2 subs is better for bass distribution if set in opposite corners...

1: how do i connect my passive to this one so they both work? The active has out for L and R. Do i plug my passive to one of them or do i need an adapter?

2: if the active has outs for LR tweeters, will it pass the lows to the passive or just highs as it was built?

3: for the new AVR will i choose 5.1.x or 5.2.x?

I can test this now as my AVR has a preamp sub RCA connection also available and if it works it will remain the same for the new AVR.

4: All current 5 speakers are rated at 70-25.000 Hz but the receiver came with a 120hz crossover preset. Should i go lower to around 90 on the setting?



Well-known Member
There are probably many more people better placed to answer this than me, but I don't think that what you're trying to do is possible in this situation.

The main issue is that the output terminals on your powered sub will only pass out high frequencies - as far as the sub's concerned, the only thing that's going to be connected to those is the satellite speakers that it shipped with, which will definitely be high freq.


Well-known Member
My initial thoughts are that either sub would "be a waste" of the x3700. What are the five speakers?


The X3700 needs to have a powered subwoofer present. It is not designed to pass the .1 LFE signal other than by a single RCA connection to a powered sub.


Distinguished Member
Connecting a passiove sub isn't realistacally an option because the AV receiver's bass management will not be be useable or applivable unless you've an active sub connected to the AV receiver's subwoofer pre outs.

You'd also not be able to output left and right channels amalgamated into a single mono channel to the sub because there's no terminals on the AV receiver that would facilitate this, not unless the passive sub has integral left and right speaker terminal inpus? Even if the sub had these, you'd still not be able filter what is being sent to the passive front speakers.

Basically, you cannot do as you want and you cannot use a passive sub, not without using a monoblock power amp connected to the sub pre outs with which to drive the passive sub with.


Novice Member
The other speakers are:

I have changed the front L and front R with 2 old Universum stereo big speakers:

I intend to keep the Yamaha 2 small front satellites for the eventual 2 Atmos height channels in the future (5.1.2 and maybe buy another pair for 5.1.4).
I am very satisfied with the sound coming from all these as my small room is banging at even -30 db. I just got this receiver along with the 5.1 speakers as a package and then i decided i want an Atmos receiver and did not return the whole pack as the speakers are great for me and i don't want to throw a min of 1000 dollars for bigger speakers. Will just replace the AVR and it appears i will also buy a monoblock power amp(any suggestions? And will this affect bass management on the new avr?) for the passive sub at that time.

Right now, as the current receiver also powers the passive sub, i have added the old powered sub to the avr's sub pre-out and both work in unison and i have bass from the 2 front corners of the room.

I have decided on the Denon 3700 as it would be more than enough for me and want to wait until Black friday but i heard about a multi channel bug on it and maybe i will need it to connect it to my pc, will this affect the lossy multi channel pcm?


Novice Member
Basically, you cannot do as you want and you cannot use a passive sub, not without using a monoblock power amp connected to the sub pre outs with which to drive the passive sub with.
I found this little mono amp for 50 dollars that seems to do exactly that:
Douk Audio G4 Subwoofer/Full-Frequency Mono Channel Digital Power Amplifier 100W

1. I would connect the avr sub preout to this one's input via a sigle RCA cable and then connect the passive sub's + and - wires to it's outs and i'm set?
2. Also there seems i would not be able to use a trigger cable with it, so the little amp will always be on?

3. Ideally i would want a small amp to also power 2 extra channels in case i want full 7.1.4 in the future as the denon 3700 only powers 9 channels(5.1.4), but the ones i found only have a R and F RCA input so no sub input powering the passive sub with it unless i change those 2 amped speakers to large and screwing the bass management as i understand.
Here is the amp with LF ins to LF and sub outs:

Amazon product

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