Your experience of moving to two subs

Hi all, I have a 2.1 system with the sub sounding best in the center between the loudspeakers. My speakers have substantial, deep, and detailed bass for their size and with the SS amp I’ve chosen. Thus, the sub’s optimal crossover setting is only at about 28hz. I have plenty of bass amplitude going on -- don’t need "more" bass.

I’m wondering about soundstage effects of having two subs on the outsides of my speakers, though. Having my sub in the center does result in some apparent compression of the low frequencies towards the low-center area. The L and R channels from my preamp are combined at my sub. I know some people may disagree and think that the source of frequencies below 60hz can’t be located by human hearing, but my experience tells me differently.

Does anyone have an opinion on the benefits of 2 subs vs only 1 when there’s no need for more bass oompf?


It pressurizes the room more evenly and helps avoid or minimize in-room bass anomalies.  Plus, each sub doesn’t need to work as hard to produce the same bass.  I don’t know anyone here who prefers one sub compared to two, so take that for what it’s worth.  Best of luck. 

The oomph is not the goal for me, either. The goal is evenness, tightness, naturalness. It's like having a room with two vents for heating/cooling rather than one. It is about distribution of waves, in either case.

Guessing about subs is an infinite project. I suggest a umik and REW and some time spent measuring.

If your subs have adjustable phase, like my Rythmiks, that will help a lot. Sometimes subs need to interact in certain ways to create evenness. Adjustable phase makes that much easier. 

@hilde45  Is 100% correct.

"The oomph is not the goal ...... The goal is evenness, tightness, naturalness."

My findings indicate that two subs are better than one and four subs are better than two. 


According to acoustics and psychoacoustics researcher Earl Geddes, the in-room bass smoothness increases in proportion to the number of independent bass sources. So two subs can theoretically be twice as smooth in-room as one sub; four subs can theoretically be twice as smooth as two, and so on. "Independent" in this context means that the subwoofer locations are acoustically completely and significantly dissimilar, and in practice that just about never actually happens; for instance even if both subwoofers are placed asymmetrically with respect to the walls, both of them are probably still on the floor, thus they are both the same distance from the floor and ceiling.

That being said, imo two subs intelligently distributed will make a very much worthwhile improvement in in-room smoothness versus only having one sub. Ime a steep-slope low-pass filter (like 4th order) can be very helpful for rapidly rolling off the top end of any subs which are positioned well away from the main speakers.

And "smoother" bass = "faster" bass, subjectively as well as literally, because it is the in-room bass peaks which take longer to decay into inaudibility and which therefore muddy the bass response.

Improvements in smoothness in the bass region pay disproportionately large dividends. This is because our ears have a heightened sensitivity to changes in SPL in the bass region, which is shown by the way equal-loudness curves bunch up south of 100 Hz. A 5 dB peak in the 40 Hz region can be comparable in perceived loudness to a 10 dB peak at 1 kHz!

The improvement in bass smoothness tends to extend throughout the room, which makes equalization more likely to be an improvement over a large listening area. With just one sub, equalization tends to fix problems in one location at the expense of making things worse elsewhere. So two (or more) subs intelligently distributed have the added benefit of making equalization beneficial across a larger area.

Duke (manufacturer of a four-subwoofer system)

Here is my take in this topic. Their is nothing wrong with one sub in a system if you implement it properly if you have the right resources. Yes dual, quad, etc, no matter how many subs you put in a room is going to improve the smoothness of the response but doing it without the use of tools and listening it not going to solve by itself especially in a room that is untreated. I have a small room where my system is and really might not require a sub but I have it for use of my listening preference, type of music, etc. My sub is set low 50s with the phase inverted. I dont have the sub in the center because I have the component rack in the area. So the sub is off center to the left about 1/4 wavelength of 1/2 of the room node, in this case around 60hz. This is almost 1/3 octave above the sub crossover frequency. The sub is low enough that localization is less noticeable and easier manageable.


REW is the norm for measurement software for this situation. I personal use Rational Acoustics for measurement in the outfield but since I have it available, it makes it easier to see what your response look like. If you are inclined with using measuring software, more power to you. Of course, you ears are the final judgement.

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Does anyone have an opinion on the benefits of 2 subs vs only 1 when there’s no need for more bass oompf?

yes i have had subs for over 25 years, of various brands (hsu velodyne m-l jbl and mostly/many rels) -- the answer to your question is a resounding yes, dual subs help expand the soundstage considerably and integrate better (as each sub has lower output than the single one)

I didn’t think I would get such high quality responses here in a row! Starting with low expectations worked out well 😆 I’ve been very satisfied with the sound I’ve been getting from my Rythmik F12G in the med-large room my system is set up within, so I’ve kept putting other upgrades above getting a second one of them. But it’s helpful to get this feedback.

Thankfully, I’ve never had any difficulty integrating subs by ear using manual phase and crossover adjustments. I do have an SVS SB2000 in a different system, so I think I’ll play with trying to integrate it into my main system temporarily, just to see if I can get a general sense of this wild world of sub-bass "smoothness". I have an extra set of longer subwoofer signal cables to make it work, too.

I’m also now thinking that since my Rythmik is the one with the paper cone (vs aluminum) for faster response, and there must be more distortion involved because of the relative flimsiness of paper, that two subs working less hard would help increase clarity. Honestly, hard to imagine more sub-bass clarity than what I have now, but I’m sure it’s possible.

In our last house, I had 2 subs and it was fantastic. Everything was improved. The only hard part was spending considerable time integrated them both properly with one another and the room.  

Thus, the sub’s optimal crossover setting is only at about 28hz. I have plenty of bass amplitude going on -- don’t need "more" bass.


No, not it isn't. But good luck to you. 

What sounds good to me is what’s optimal in my system.

tis true, as one of the youtube heads say... ’’ all that matters is that you like the sound of your own system’’ or something to that effect

what gets a little more complicated, and perhaps interesting, is when we get the itch to try to IMPROVE our system.... how do we go about doing that?

some ask others for advice, some tinker with their existing gear and room, some try to measure to understand what might be going on as a way to shed light on potential avenues of improvement, and some just go and buy new stuff on a trial and error basis

we all enjoy the process differently, think differently, arrive at conclusions differently on how to improve, what to do next...

... and @hilde45 ... good analogy on the hvac vents in a room... i like it, it works!!!

I moved from one good REL B1 to three total and then four subs (all set 60 or lower) and when set up properly I do enjoy it more, like most.   

If one can 'hear' and localize deep bass I might suggest the overtones or a second order sub crossover getting in the way. I believe something is heard, not the deep stuff though. The four subs I have are not set so loud or set so high as to ever know where they are for me.

The 'air' and additional horsepower are nice additions. Good luck and good idea on trying out the SVS SB-2000 as a test (I have two of those and an SB-3000).


@tony1954 Agreed: a distributed bass array is the way to go. But if you can’t get there then two is better than none. Regardless, as others have stated, you need to put in the time & effort to optimize it. For me, it was one of the most cost-effective, biggest bang for the bucks that I’ve spent in this hobby. Huge, comparatively speaking. (Assuming you have a fairly well treated room too. Which is another big bang for the $$.)

Plus 1. 3 subs in my system, 2 LR front and 1 in back left of MLP. Helps to minimize null points and cut room mode issues. 

What sounds good to me is what’s optimal in my system.

This is true but this also assuming you’ve actually tried the alternative: High passing your mains at least at 60 Hz and letting your subs take the heavy lifting.

I don’t know everything you’ve tried, but I’ve never encountered anyone doing what you are now who didn’t end up being very happy to try again with a higher crossover.

Of course, that all requires measurements. :)


@erik_squires Ah, I see what you mean. I never went that way because I was doubtful of the purity of an active crossover's output and its circuitry. It would be interesting to try though. Does anyone use passive line level high-pass filters for sub integration, and achieve an excellent level of transparency through it?

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@ditusa Looks like I need to get busy reading to understand my options better. Appreciated! I'm also looking at some FAQs on Rythmik's website about integrating a sub and why they normally advise against using the optional speaker level inputs.

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It’s funny.  I had a good sit down with Alon Wolf where I argued that using subwoofers to augment the lowest octaves of bass has advantages over trying to achieve 20Hz and lower bass within one cabinet, not the least of which was room integration and speaker positioning issues.  At that time, about 10 years ago now, he was adamant that subwoofers won’t work because they fail on producing an accurate impulse response and he proceeded to sketch me graphs on a napkin to show me why this was so.  But now that Magico sells their own subwoofer either Magico has solved that equation or have conceded that the advantages of well-implemented subwoofers outweighs a perfect impulse response.  My guess is that Magico customers were asking for subs and Alon is just adding a product to fill this demand, but I’d love to hear his rationalization when he so vehemently argued they couldn’t be implemented accurately.  So it goes. 

@soix I can feel it in my balls that loudspeaker woofer distortion is minimized by passing low frequencies to a subwoofer. That's how I know it's true. Would you like to see the napkin that I've deposited the evidence on?

Heh heh.  I’m with ya man, and maybe that’s why Alon finally saw the light.  If Wilson uses subs with their Alexandrias, well…


The Rythmik Audio website's FAQ section that I've been re-reading since I bought my F12G sub seems excellent to me. One fine example:

( @soix )

"Cone excursion goes up 4x for every octave lower in frequency. So 40hz needs 4x more excursion than at 80hz. And large cone excursion increases distortion and in particular "intermodulation distortion" (higher frequency (small excursion) signal is modulated by low frequency (large excursion)). The correct way to address this is put a high pass filter (HPF) on front speakers in order to reduce the cone excursion. This issue is particularly bad for ported front speakers as you may notice with full range signal, woofer in ported speakers have far more excursion than that in sealed front speakers. With the cone excursion reduced, the distortion from the front speakers is also reduced and the sound becomes more dynamic and coherent."

Rythmik FAQ about Subwoofers

Rhythmik makes awesome subs and I hope the SB2000 (that I also own) can keep up.  My guess is it will and that once you get both subs dialed in you’re gonna reap sizable benefits.  Keep us posted!

I had one sub broken for awhile (I normally run two) and when I had one I had to really mess around with placement, crossover point etc. got the other sub back so back to two and the System just snapped right back into place. Sounded even and right again. All I can figure is only using one was making lumps in the frequency response and sometimes it sounded fine and other not so much.

now 28hz is pretty low and might not benefit as much. I was running 60hz at the time notes above.

@soix Haven’t tried yet, but the Rythmik F12G is so much faster than the SVS SB2000 that it’s really in a different class. Is a different type of technology altogether.

My plan for when I try putting them into play together is to use a copper power cable on the F12G that I know sounds slower and more smeary and an 11awg 7N OCC silver power cable (which I normally use on the F12G) on the SB2000 to attempt to split the difference in apparent rapidity of response. Not sure if the SB2000 will get anywhere close in speed because of the silver, but my testing in the past showed that it was very responsive to changes in power cables. Much more so than the F12G.


@james633 I totally believe your anecdote. I also think I have a fortuitously sized and featured listening room for low frequencies. My experience has been far easier than the average report about using single subs that I've read. Nonetheless, I'm getting more and more interested in dual subs as this discussion progresses.


you might be hearing a longer group delay that could make it sound “slow” I have not seen the SB2000 group delay but I was a bit surprised at how high the group delay was on the SB 16 Ultra (link below). It was over 20ms.  You could argue at that low a frequency it is less important but still about twice what JL does with their subs. The only way to overcome the delay is using an active system to delay the mains. Receivers can do this and same fancy highnesses as well.  Well a mini DSP does to but the output stage is junk.  anyway just a guess and thinking out loud.

my 2 cents: you need money for 2 subs to try to 2 subs. My problem solved.

(I have one sub, purely because I lucked out, I could afford zero)

Never heard of the term group delay before, but maybe that’s it. The Rythmik sub uses a direct servo motor system to control transient response precision. The SVS in comparison sounds like the cone is slower to change direction. If it’s phase alignment that’s being referred to, I can confidently assert that it’s unrelated to my comments. Both the Rythmik and SVS have manual phase adjustments.

Yes group delay matters a lot with subs. group delay and phase are related. The audioholics information is very good.

Many subs are delayed enough they are a full cycle back. The kicker is it can change at different frequencies so you can’t just adjust it out with a simple phase knob. At the lower frequency the cycles are so long (slow) it is less of an issue but still very relevant. It is one of the down side of having all the high tech processing in subs these days. It all takes time even though it is still pretty fast. I personally will not buy a sub unless see the group delay measurement as I feel it is important. In a system where timing can not be corrected (99.9% of 2ch preamps). Think of it as input lag ratings of computer monitors.


@james633 Sounds like why I chose to give up on the parametric EQ section of the amp on my Rythmik sub, soon after buying it. Sounds significantly better and faster to me without applying a specific FR curve.

The argument that convinced me to go with two subwoofers says:

The bass wave is extremely long at the low end of the sub’s output, and the listener cannot tell where it originates.

The sub’s output higher up the spectrum enters the zone where the listener can tell where it originates.

And we want every directional cue we can get for the best soundscape.

Admittedly not much information is ‘lost’ to the listener with only one sub - if any is ’lost’ at all at those frequencies - you’re already down at 28Hz.

It’s a matter of a few percentage points improvement, maybe only 1% or 2%.

For me it was vital improvement.

Bass and drums took on a richer, finer texture, and the soundscape resolved more completely.

But then, my crossover points are in the low thirties and upwards of fifty for Magnepans.


@ditusa The article written by Doug Blackburn exudes confidence and it sounds plausible, but I disagree with a good portion of his assertions due to my experience. "Listen to a subwoofer all by itself for a while. You won’t hear anything vaguely resembling speed coming from that slow, soggy-sounding, plodding subwoofer. It has no detail and no speed whatsoever when heard all by itself."

I’ve done this with different subwoofers and they sound different. The SVS SB2000’s perceived quality of rapidity vs slowness changed significantly when changing its power cable with those of different materials and constructions. I started a discussion thread here about it some time ago.

The way I see it, the audio hobby is really about listening. Some people can detect differences just by listening, so they don’t rely on concepts so much, just like some people who can see clearly at very far distances don’t need corrective lenses. Some people don’t have the ear/brain training/gift/whatever to perceive as acutely, so they rely more on measurementation and abstraction. This is the primary basis for my system building, and the reason I disagree with the author.

I’ll give the other article a read today. I think it’s more up my alley.

I have 2 subs-10" Eminence.  We run these with a Yamaha power amp, commercial.  I have never ran out of power.  I have a Marchand  crossover to make sure the level is right for subs and mains.  The crossover is at 100 Hz.I don't have phase adjustment.  These subs are where they were for 20 years.  I don't know if it would sound better somewhere else.  Recently I removed the crossover and ran the speakers fill range. Not as clear, less bass and transients all were not as good.  Why?  The subs reduce load on main amp and reduce intermodulated distortion.  This causes the mids to be not as clear.  I  have 2 bass traps and 6 first reflection with 3 diffusion panels in rear.  I finally have the system so I can walk around the room and the sound is the same, except no imaging.  I could buy a couple more bass traps, don't cost much.

I've gone from 1 Rel to two Rythmiks and now adding 2 more Rythmiks.

Going from the Rel Storm III (vented) to two Rythmiks F12 (sealed, in heavy DIY box, aluminum cone) was definitely an improvement in every way. My audio setup is in the living room so ergonomics dictate plausible places for the sub/s - which aren't that many. So it's really no surprise that two worked better than one (and 2 servo-driven Rythmiks were cheaper than the Rel to boot).

Later I experimented with stereo vs mono subs (both subs playing the same signal) and didn't hear a "stereo" difference - I was crossing over at 60-70Hz. I used the Rythmik's xo for a while to relieve the main (tube) amp and speakers from reproducing low bass and that was definitely an improvement. I did get a measurement rig to correlate what I heard with what I measured and with what I read in papers/online/books.

Eventually I went with a fully active system and have the signal for the subs sent to a miniDSP 2x4HD and implemented MSO (Multi Sub Optimizer) and believe that was another improvement. With MSO you take measurements of each sub at each listening position you define and the software optimizes (amplitude, delay, PEQ) for the flattest response across the defined listening positions. So I used my two subs to simulate having 2, 3 or 4 subs at the different locations I could live with and ran the optimizations. That showed that 3 subs were better than 2, and 4 were better than 3. This is consistent with Earl Geddes' approach. He has said 3 subs would be enough, provided there is freedom to locate them, which I don't (all need to be on the floor, two visible by the main speakers and two under end tables). So I went ahead and purchased 2 additional F12 kits. I'm building the boxes now.

Still TBD if all this will be worth it, but it has been a fun learning journey 😀

I've just started playing with this in a PC system.  I'm buying small subs off ebay for cheap and now have 4.  2 tiny PSB sub series 100s and 2 Episode 8" Evo subs.  Episode is a custom install brand and has terrible resale value because nobody knows what they are.  I took a small chance for about $150 including shipping and it's definitely better than I'd expect for that price.  They're not blow the doors off HT subs but get you down to the high 30s.  All 4 subs are sealed.  

I dunno... I might not be popular here in this discussion, but oh well here goes:  I went for many years without a sub at all, with my Epi 100s...  never felt the need.  Have one now, though, and do like it, but it wouldn't be the end of the world if I didn't have one at all. 

Maybe it'd be worth the effort if I have time, space, money, and the correct tech and meters and whatnot to balance it all out with two subs, but I'll cross that bridge if I even feel like it when the time comes.  Maybe if I have a bigger room or something, or just if curiosity gets the better of me.  I'm quite satisfied as is, both with my Epi and my Heresy each w one sub in different rooms.

I do like the one dual-side firing sub that I have with my Heresy IV, positioned right between the speakers... and maybe that two-sided firing helps with the "balance" in my room, but I never localize the sub w my ears... it is a complete disappearing act.

@curtdr, Honestly subs are more for movies or just messing with.  They do make a difference with some music but if you mostly listen to music that doesn't have much below 40 hz you don't need them.  If you want good bass the most important thing is to live in a lightly built wood frame house that lets a lot of the bass escape through the walls.  

I have two rel 812s, crossed over at

32 cycles. What I experienced when I added

the second sub was a bigger soundstage

and more clarity in the mid range. All the best.

If you believe you got good bass - work harder. Don't be satisfied. The reward is great!