Subwoofer Options With No Spare Preout

I only have one preout on my preamp, and I’d like to add a pair of subs to my system. I’m curious peoples thoughts on the best method. I have a few options in mind that I’d like feedback on but if I’m missing an option let me know.  First option I’m considering is a pair or Rel’s which would be pretty straightforward to setup. I’ve also thought about getting a separate crossover with both high and low pass filters. I know in theory this is likely the best solution. I won’t be working with a large budget so something like a Sublime Acoustic K231 is probably the best I could manage. The likes of JL audio, Bryston, and Marchand are bit out of budget.  This would allow me to use any subs I’d like, possibly even some DIY passives. The last option I’m considering is simply splitting the one preout and running one channel to each sub. I know it’s not ideal but I do have considerable excess gain in my setup even though my pre only has 9db. I never get past 10 o’clock but generally at high volume I’m around 9 o’clock. 

My system right now consists of Audio Mirror Reflection monoblocks, a Canary C630 pre, Totem Arros, and a Bluesound Node.  The room is 9ft by 11ft with 8 foot ceilings. I’m still uncertain if my next purchase will be subs or a new digital front end. Both will happen before to long because I need more bass and I know the Node is holding back my system considerably.  Anyways any thoughts or opinions are much appreciated. 


Hi OP:

The cap provides a first order high pass filter. You want to use a cap which provides the same impedance as your amp’s input impedance. So if the amp is 47k your cap should also be 47k at the crossover point, which I recommend no lower than 80 Hz. With those low efficiency speakers this will greatly reduce distortion and make your amp play much louder.

I believe this just happens to be 0.047 uF for you. I recommend Jupiter copper foils.

This simplifies subwoofer integration, and will double the apparent size of your amps. Also, most people report greatly improved soundstage and reduced distortion this way.

PS - There is a myth audiophiles have that they should buy a subwoofer only for 1 octave.  Every single time I've convinced those audiophiles to try the alternative they never go back, not just for the bass but for the overall improvement in detail, soundstage, and dynamic range.

Pass on the RELs as they do not have sufficient controls to integrate properly. IMO REL now markets bling as opposed to decades back when they were excellent.

Required controls are continuously variable XO frequency, variable XO slopes, continuous phase and polarity inversion. Without these controls only physical movement of the sub enables proper integration. Martin-Logan X series have the requisite controls.

It’s simple to build a HP xover for the mains which enables proper integration. Rolling the bottom octave out of the mains effectively increases main amplifier power.

Subs have significant output into the mids and are localizable. Therefore they must be coherent with the mains. The easiest way to achieve this is to have them in the same area as the mains.

See ieLogical SubterraneanHomesickBlues for more information on sub integration

I know nothing but in a 9x11 room where will the 2 subs' waves go?  Seems  challenging

That website is a rambling mix of useful information and total BS I’m afraid.


Subs have significant output into the mids

BS. Not if properly configured. Most use a 4th order low pass filter and usually don’t go any higher than ~ 120 to 150 Hz.

and are localizable.

If you mean you can hear where they are there are only two reasons I know of only two reasons for this:

  1. External vibration/rattling
  2. Too high a crossover point.

In my system not only can you not localize the sub but you can’t even really tell it’s working until it is off.

Therefore they must be coherent with the mains.

No, eliminating localization and making sure your stereo output presents one coherent presentation are not exactly the same thing.

The easiest way to achieve this is to have them in the same area as the mains.

A - Not true and B - I wish it was that easy.

I appreciate all the feedback this far. I do really like the idea of high passing my little Totems. This way I could set the crossover point higher. I love the Arros but obviously lacking on the lower end, probably even above 80hz. The Rels I still can’t let go of as an option because they are so well liked and reviewed.  Im guessing either way I could get good results. Figuring out which is best seems tough to do short of trying both though.  

anybody have any thoughts on the Sublime Acoustics crossover?  I like that it would eliminate the rca splitter. Also, I like that’s it’s affordable to try different crossover frequencies to see which I prefer. I worry I may need some sort of DSP though to get control of all the extra bass produced. Something like a mini dsp would be perfect but I just can’t believe it would t degrade the sound considerably. Thinking maybe a streamer that has some eq along with the Sublime crossover may be the ticket. My Auralic in my other system does have if I remember right a 5 band eq, and you can choose the frequency point which is nice. I feel this could at least get rid of any large peaks. 

Again thanks for everybody feedback!