2 Channel Subwoofer connection

Hello, I am seeking advice for a Subwoofer connection.  My system consist of a Rotel RCD 1570, Jolida JD 202 Integrated Tube Amplifier and a pair of Bowers & Wilkins 705. This set up is just for music listening.
I like how much detail I get from the music with these 705, the only problems is that my loft is an open space with high ceilings, therefore, the bass is not very strong. I thought I could add a Subwoofer. The issue is that my integrated amplifier doesn't provide a Subwoofer out. The only option will be to run speaker wire from the integrated into the Subwoofer's speaker level inputs, then connect the 705s to the subwoofer's out (As pictured in the diagram)


However, as I've never attempted this connection, I am concerned this could degrade the audio signal, would the sound quality be affected due all these extra wiring and having the signal go through the subwoofer and then to the 705 monitors?
I've looked into the Bowers & Wilkins ASW750  but this doesn't come with sub's level inputs. I am considering the ASW300 instead. Any advice will be much appreciated.


Hi mamifero,
Looking at a picture of your amps back I see you only have speaker level outs, that certainly limits your options. I think for the best sound you should keep your speakers connected directly to the amp.

I don't know your budget but using say an REL subwoofer with good speaker level inputs and running  separate speaker cables to the sub you would probably achieve your best overall sound quality.

Good luck,
Joseph, To add proper bass to your system you need a REL subwoofer, This sub will connect right off the main amps output taps (just like your main spkrs) You dont need a Sub out! You just need the proper subwoofer. The REL uses a special cable called a SPKON connection. its very easy to setup and the great benefit of this connection is that it recieves the same signal as your main spkrs which allows it to blend much better. REL makes subs of all different price points. Find the one that fits your budget, you will love it!

Matt M
especially with a tube amplifier the preferred way to connect a subwoofer is through high level inputs-  connection to amplifier's speaker terminals in parallel with the main speakers.  it helps with the integration and can sound more seamless.  
I love my JL Audio D110 which has these connections as well as a continuous phase angle adjustment,  another key control for seamless integration.  
Hi Matt,

Thank you so much for your advice. That's exactly the type of connection I was aiming for-as that's my only option- because I don't have a sub out on my amplifier.
However, my main concern was if I will be degrading the sound quality by running the signal through the subwoofer vs the current set up (amplifier connected directly to the speakers).
By the way, I currently have them bi-wired. Would you recommend bi-wiring from the amplifier to the sub and bi-wiring from the sub to the monitors as well?

Thanks for your time.

as I mentioned in my earlier response you should keep your main speakers connected  to your amp as you have them, then run a second set of speaker wires to the REL subwoofer. You will get the best sound reproduction keeping your main speakers connected directly then add the sub, you will need to spend some time setting up the sub, crossover frequency and level matching.

Some time and patience will have you very happy with the great bass added to your existing system.


This is why Im recommending the REL it has ONE cable with a spkon connection for the SUB side and three bannana plugs for the amp side( 2 positive 1 negative). You leave the speaker wires in place as you have them already, no need to change that. IN THIS WAY, the amp dosen’t see the SUB. So this has no effect on your amps output. Yes this is the most sonically appealing way to connect the REL. Your not giving up any sonics! In fact, set up properly it will make your mains work less and they become free to play more musically and everything is improved.

Matt M
High ceilings - large space =  weak sound  Surely you could try a sub, but make sure you can return it if it doesn't work out
+1 avanti 1960
The JL Audio D110 is an oustanding sub. I use one with my Harbeth monitors and it works better than other subs that I have used.  Crutchfield has a return policy if it doesn't work out for you!
My recommendation would be Vandersteen 2w/q sub(s) with the proper crossover. It would free up the Jolida from reproducing the lower frequencies, and they integrate seemlessly.
The Rythmik subs also provide speaker level connections to a power amp, just like the REL.
Thank you all for the useful advice. I will certainly look into the RELs and the other brands.

A couple of questions though. By keeping the main speakers connected to the amp and then running a second set of wires from the output taps to the sub, there won't be need to adjust the phase adjustment knob correct? 
As it sounds like they will be in sync for what I understand.
Finally, regarding bi-wiring. Currently my main speaker monitors are bi-wired to the amp, should I bi wire to the sub as well?

Here's an alternative option if you can use two subs and your main speakers allow both spade and banana connections.  In my winter system, I use a pair of Gallo TR1D subs.  The subs have a speaker level input.  I run my main speakers full range with the speaker cables terminated with spades which leaves the banana sockets at the speaker unused.  Therefore, I can send the signal to the subs with a short banana terminated cable of the same type as the main speaker cable to each sub directly from the main speaker.  This way I don't place the cross-over of the sub inline with the main speaker.

The cross-over adjustments on the subs still function as regards to the subwoofer outputs but do not limit the signal to the main speakers.

My main speakers are first order and the Gallo subs are sealed.  The subs are placed close to the main speakers and integration is fairly simple.   

I also dislike REL subs FWIW.

With the recommended set ups I would just need a passive sub. However, most subs are active. Does it make any difference to buy an active sub and use it as passive? Would the active sub be on all the time, thus generating unwanted interference, even though it will be used as an active woofer?
With my setup you definitely need active (powered) subs.  The Gallo subs I use automatically go to standby when no signal is present.  They are switchable for full on, full off, or signal switched on/off.
Any subwoofer with high level inputs will work fine.  Just leave your B&Ws wired directly as they are and run two speaker wires to your subwoofer, connecting from the same taps your B&Ws use to the left and right high level inputs on the sub.  I would not wire a passive sub this way as the amp will see the additional load.  Wiring an active sub this way is perfectly OK as the amp sees no additional load.
Thanks for clarifying Danaroo, this is very helpful.
Interesting hook-up method!  I guess what you're doing is trading off the benefit to your system amplifier not having to reproduce deep bass to the main speakers in favor of eliminating any signal degradation to the main speakers by avoiding a crossover network in the signal path.  Seems reasonable to me, especially if you have a robust amp or very efficient main speakers.

I use crossovers with my set-up but they are of a very high quality as Vandersteen prefers that set-up.

One more thought...You must have to be careful that the quality and nature of the bass from the main speakers mates up well with your subs.

As usual, system set-up and careful component matching are key.

Hooking up any sub using the amps taps to run a second set of wires to the sub using a HIGH level input is connecting the sub in the least favorable way for sound and integration.
Sorry Matt.  I'm not following your post. Probably my fault as I am not good at reading between the lines. Can you explain the above post in a bit more detail?  I'm wanting to understand your point.  Thanks!
+1 hifiman5
Yes mattmiller please explain your logic
Subs that use 4 (2 neg and 2 pos) wires from the amp to receive the signal is an old outdated way of running a sub, how can you say the active sub dosent see the 2 additional wires connected to it..it does, and it has to deal with it. I call this smoke and mirrors and subs hooked up in this way never integrate and your always adjusting knobs with every song. The REL’s dont connect this way they only send 3 wires (2 positive 1 neg) this way the amp really dosent see the sub because its running at 100,00 ohms! You set the REL and once its dialed in thats it, you dont fiddle with volume and crossover points ever! The REL is just there doing its job, and its very musical, anyone that thinks subs are for adding non directional bass has never heard a REL.

And NO i'm not a REL rep, I always hated Subs because of lousy connections and bad integration...until I found a REL Britania B2 10" in natural cherry. with upgraded (signalcable.com) spkon connection.

Matt M
Talk to Richard Vandersteen. He can explain to you that a sub can work superbly in the way you say it can't. Yes, I have listened to a Rel Gibraltar 3 at length and the Vandy 2Wq will do everything the Rel does and more.
+1 mr_m   I have two Vandersteen 2wq subwoofers.  Using RV's top quality crossover that you set relative to the input impedance of the system amplifier, helps the subs to integrate seamlessly with the main speakers.  I have Vandy Treo CTs which are a full range speaker in their own right.  The subwoofers free the system amp of having to power the deepest bass as each sub. has a 300 watt amp. and the speaker cable hookup of the subs to the system amp allows the subs to see the amplifier output so that the sub sound integrates perfectly or nearly so, to the main speakers.

I have experimented with the integration notion by using the subs then disconnecting them and trying to identify the point at which the sub kicks in by ear.  I just can't find it.  The key to this kind of seamless sonic integration is to adjust the "Q" and level of the subs.  Once you get it right, you free the main speakers and power amp from providing deep bass, improving the dynamic ebb and flow of the music throughout the full frequency range of the music.  If you can establish proper speaker and sub. placement in your room, the speakers and subs just disappear.  It's all about the music now, no the gear reproducing it!

As far as REL goes, I have no experience with them but have read many many positive references to them on A'Gon and elsewhere.

Happy Listening!
Regarding three-wire vs. four-wire connection of a sub to the outputs of an amplifier:

In most stereo amplifiers (as opposed to monoblocks) the negative output terminals of the two channels are connected directly to the amp's circuit ground, and are therefore connected directly to each other within the amp. Exceptions to that are mainly amps whose outputs are balanced or bridged, since in those cases the negative output terminals have full-amplitude signals on them, as opposed to both terminals being connected to the amp's circuit ground.  Certain older class D designs that have substantial DC offsets on both their + and - output terminals are also exceptions.

When the three-wire cable that is used to connect the high level input of a REL sub is connected to the output of most stereo amps, one wire goes to the positive output terminal of one amp channel, another wire goes to the positive output terminal of the other amp channel, and the remaining wire (the ground wire, which is colored black) goes to the negative output terminal of either channel. The reason that works well is, as I said above, that with the exceptions I noted the two negative output terminals of the amp are connected directly together within the amp.

So if the high-level inputs of a single sub are connected to the outputs of most stereo amps a four-wire connection amounts to having a three-wire connection plus an additional connection to the amp's circuit ground in parallel with the ground wire of a three-wire connection. The load presented to the amp by the sub is the same in either case, and will be negligible assuming the sub is active (i.e., that it has a built-in amplifier).

Special considerations come into play if the outputs of the amp are balanced or bridged, or if monoblocks are being used, or in the case of certain older class D designs as I mentioned above.  In those cases, depending on the designs of the amp(s) and the sub, and on whether one sub or two is being used, specific connection approaches are necessary to avoid the possibilities of hum problems or even amplifier damage.  These issues are discussed in the manuals for most REL subs, and need to be considered regardless of whether the connection is via four wires or three.

-- Al
Subs that use 4 (2 neg and 2 pos) wires from the amp to receive the signal is an old outdated way of running a sub, how can you say the active sub dosent see the 2 additional wires connected to it..it does,

The subwoofer plate amp sees a signal from the speaker terminals of the main amp, but the subwoofer driver load is seen only by the plate amp itself, not the main system amp.  If I understand the OP's situation, he can connect any active sub with high level (speaker level) inputs to the speaker terminals of his Jolida 202 and the Jolida will still recognize ONLY the load from his B&W 705s.
If I understand the OP's situation, he can connect any active sub with high level (speaker level) inputs to the speaker terminals of his Jolida 202 and the Jolida will still recognize ONLY the load from his B&W 705s.
I agree.

The one qualification I would add to that is the slight possibility that electrical noise picked up by or introduced into the sub cable could conceivably have audible effects on the signals provided to the main speakers as a result of entering the feedback loop of the integrated amp. (The 202 is described as using "less than 9 db" of negative feedback). That kind of effect, by the way, might be one of the reasons people report finding sonic differences among different sub cables.

To the extent that might be a possibility, four wires could very possibly be better than three, depending on the specific cable designs.

-- Al

Thanks to you, Al, and hifman5. I knew a  lot of these things both of you mentioned, but just couldn't put it into words;)
+1 almarg!  Very easy to follow explanation.  I appreciate the clarity.
I use 2 RELs with home assembled Canare cables and Neutric Speakon plugs…used in mono by joining the wires in appropriately large AQ silver spades (main speakers are on bananas). I had to lift the ground on the larger REL (Q150e) but this rig is utterly noiseless. Also, somebody noted you don't have to reset the levels, but I've found bass level disparities among various recordings sometimes requires adjustment of the REL levels here and there, and I put an easy access chicken head knob on each one for that purpose.