I recently got a master’s degree in acoustical design, and now one of the main questions I got from my friends who are into listening to music and/or have a home theater is, “what’s better, one large or two small subwoofers?”.
They also asked me if should they upgrade from single to dual subs and what’s the right call here. But not all of them are looking to pressurize a space with bone-crushing bass fully. Actually, most of them just want to watch a movie here and there and listen to music in a dedicated theater space.
When talking about this subject, we must also remember that not everyone is looking to max every output parameter.
While two subwoofers are generally better than one because they smooth out the bass in the room with careful placement (fewer room modes – smoother frequency response), they can also decrease bass quality if the placement is not done carefully.
This is a complicated topic that will take more than a few sentences to explain.
1 vs. 2 Subwoofers – What’s Better?
If you’re looking for a sub for a medium to large-sized room, this is how you’ll decide if you need 1 or 2 subs, the easy way:
- Are you only concerned about the main listening position?
- Do you have enough flexibility to place the sub in the optimal spot for the MLP (main listening position)?
- If the answer to both is yes, then get the one bigger sub.
- If the answer to either is no, then two smaller will be safer.
If 1 or 2 are no, but you can eventually save up to get a second big sub, it will be up to you if you want to take the chance of not having the best placement/sound while you wait to get a second.
There are many people that:
- spend too much on subs.
- get subs that are eyesores and take up too much space in the room and
- listen at levels, particularly on the low end that is way too loud.
As Tom Vodhanel, the founder of Power Sound Audio said in one interview, people need to realize that the potential benefits with multiple subs are just that: potential.
The advantage of dual subs is usually seen as more even coverage. But a lot depends on room dimensions and where the sitting positions are. To get the full benefits of multiple subs, you need to have flexibility in placement. Some people think it’s going to be exponentially better with two subwoofers, but that’s often not the case.
You also have to factor in the cost and the room size, as it depends on what subwoofers are available at the given price points;
Two small subs or one large for the same money
Sometimes two subwoofers for a certain price do not have the same max SPL as a single sub for that money. And in a very big room, that might matter, particularly if there is only one listening position where it’s doable to get placement for a sound response.
Talking about budget, this also greatly depends on the quality of the subs. A $500 sub is different from a dual $250 subs. It typically represents the line where folks start talking about a “real” sub that drills down like a cheaper one simply can’t due to physics.
Ten $100 subs won’t give you output down below 16 Hz. There’s a distinction between a boom you can hear vs. sounds sufficiently low that you can just feel it.
Meanwhile, a one $1000 sub is a very distinct creature where output and extension will be “enough,” and it should have no issue pressurizing a normal-sized room. Getting a second sub like that will probably be the less efficient way to buy smoother output.
You’re not going to be purchasing more output with a second sub because $1000 of a one-subwoofer in a regular-sized room is going to be a considerable amount of output as it is. If you purchase a second, you’ll first turn down the volume.
Dual 8″ subwoofers have about the same surface area as single 12″ (~100 vs. ~113 sq. in.), so they likely can shift about the same quantity of air. But which is better in practice?
On the one hand, two subwoofers in different places should help with room modes, and lighter cones are usually more responsive and punchy. On the other hand, two subwoofers mean two amplifiers and two cabinets, so for the same outlay, less money is going on the actual speaker, and well, isn’t larger automatically better?
I had an identical dilemma in 2020. Couldn’t decide whether to buy PB-4000 or 2x PB-2000, though it was not the same cost – the PB-4000 was even more costly than the two, but I got some fair deals.
I purchased 1x PB-4000 for three reasons:
- I could adjust the volume from my couch. This was an essential factor for me from the beginning – I have a little kid and change the volume frequently as I like a lot of basses but can’t do it when the child is asleep.
- Dual subwoofers require time to set up properly. Misconfigured will sound worse than just one, and I don’t have much time to mess with settings and calibration.
- The PB-4000 is (evidently) better in any measure.
Here’s the link to Amazon for PB-4000 if you’d like to check it out, it’s pretty awesome.
When is it better to get a single, and when dual subs?
Having a second sub will just give you a 6 dB gain in output. That’s actually nothing special at all.
If your primary speakers have a 3 dB difference from one frequency to another, then humans will typically not notice it and think it’s “flat.”
You can make the output difference just by turning the knob slightly. You’re really hearing the effects of having smoother frequency responses across the room. That’s why people go dual.
In theory, given the correct parameters, you can get a better result with a single subwoofer and adequate bass trapping. Bass trapping with a single sub would give you a flatter response than two subs in an untreated room.
But if you have a somewhat larger room…
I’m claiming that one of the best upgrades you can have for your system is dual subwoofers. Two subs make the bass so much more impactful and sufficing. It just feels and sounds so much smoother.
Does wattage impact the loudness and clearness of a sub? When buying, do we just look for the highest-rated sub in terms of wattage in our budget? How many watts make a good subwoofer? Find out in the linked article.
Benefits of adding a second subwoofer
- Dual is more valuable if you have multiple listening positions. 2+ subwoofers help to even the bass throughout the room. Two subs will always offer a more even, lower distortion response over one. By more even, I mean the response will be more similar in more seating positions all over the listening space.
- Added overhead reduces the load on a single subwoofer.
- With solid placement (i.e., not having both upfront), you can get a better bass response for the entire room/seats.
Not so long ago I built a 5.1 sound system for my friend’s entertainment room. He got two SVS-PB1000s (link to Amazon, they’re fantastic).
He told me that he turned one sub off while messing around one day.
It was a discernible difference in sound and feeling all over the room. Still sounded great, but it was different. So he listened for half an hour or so and then turned his second sub back on. He thanked me and told me that it made him realize having two subs is night and day.
If you don’t have acoustic treatments in your space, these Auralex isolation platforms are great for tightening the bass up.
Tradeoffs using multiple cheaper subs vs. one more expensive one
There is an advantage to using multiple subs – eliminating room modes. Room modes are gaps in bass coverage induced by the shape of the room and the way low-frequency sound waves propagate.
Using multiple subwoofers lets you position them such that any modes in the listening positions are negated.
Yet, there can be tradeoffs when it comes to utilizing multiple cheaper woofers vs. one more expensive sub, and that is frequency extension, all-around volume, and sonic accuracy.
Frequency extension: A bigger driver, in general, will go lower than dual smaller drivers and will do so with more power.
Overall volume: Dual subs, placed close to the same spot, will boost volume by around 6 dB. On opposite walls, you’re looking at roughly 3 dB. A more powerful amplifier backs a more costly sub with a larger and more efficient driver and may accumulate as much as 10 dB by itself.
Sonic accuracy: A more pricey subwoofer, made out of thicker, better-braced material, with a more powerful amp to deliver headroom for dynamic volume changes (explosions, cannon fire, etc.), can be more precise, distort less, and sound better than dual (or more) smaller subs.
In the end, the choice comes down to a couple of considerations. How large is the space? Larger spaces may need multiple subs. How poor are the room modes? And, can you get better performance out of an upgrade than out of adding a woofer? If you can get more than 6 dB and more than 3 Hz lower, it’s likely worth the upgrade.
One sub or two subs, proper placement is still the most important part
Multiple subwoofers, *when placed correctly*, can decrease the seat-to-seat variance of bass response, so you see it suggested in some circles.
This Harman study supports the trend, which conducted simulations of subwoofer placement to balance some axial room modes. The study found that dual subs can provide nearly as low variance as four subwoofers, but it depends on the subwoofer positions.
It’s simple to put multiple subwoofers along the same wall and be left with identical axial room mode activation.
Just to add, the idea that smaller (or multiple) subs sound “faster” is a delusion. It’s normally the inductance of the driver (and how much power you can provide it) – not the weight.
Rythmik utilizes servo feedback to control cone activity further. That generally enhances impulse response, which most folks mean by “fast.”
Bigger subs are a more efficient solution to reducing excursion and intermodulation distortion (IMD).
Multiple subs can acoustically pair for a doubling of output – but solely when they are located within ~1/4 wavelength of each other.
To minimize conflict, though, they need to be far enough separated that you no longer get accurate summation. Instead of a perfect 6dB, you might get closer to 3dB or 4dB. That extra 3-4dB gain does help decrease distortion vs. a single subwoofer.