More Than One Subwoofer is Better? Let's try it and Find Out

Multi-sub. Does it work?
In this video I show a fairly rough test I ran using the 4 infinite baffle subs that are located in the front wall of my listening room. I also have a smaller sub that I can move around and I put that in 6 different locations to see the results.
Just from measuring the 4 fixed subs I can easily see that the frequency response improved. It was flatter without any of the dips the individual subs had on their own.
Adding in the mobile sub gave a solid boost in the low end, even though the output from that sub is a lot lower than the fixed subs.
So yes, the multiple subwoofer concept is a winner, in that it greatly improves the measured frequency response at the listening position.
However, I did not see a significant difference in the reverb time from one setup to the next. One of the claims for the multi-sub setup is that it can "fix" room modes, but I see no evidence of that. Granted, I didn't run through every possible position for the mobile sub and my fixed subs can't be moved at all. Also, my room is fairly well treated to deal with low frequency reverb and maybe the effect would be more obvious in an untreated room.
I'm inclined to think that if you can effectively nullify a room mode by careful positioning of an additional sub, it's going to be a very tricky task. You'd DEFINITELY need to run measurements to check whether you are actually producing an improvement, and that would take a lot of time.
And after all that, would the improvement be significant? Like I said, I saw NO real difference in the reverb time with each test, but I DID see a significant response improvement.
The 6 locations for the mobile sub were side left, side right, middle of the room, back corner left, back corner right and middle of the back wall. I'm pretty sure the best response was with the sub on the right side, with middle of the back wall a very close second. Since the middle of the back wall is the most suitable, that's where a new subwoofer will go (yes! future build!).
My room is 14' x 14' with an 7' ceiling. The dominant room modes are at around 38Hz and 70Hz. I've done extensive work to acoustically treat the room to reduce the reverb time and I have a few videos on this channel showing what I did, so please check those out.

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[IBuildIt]

Multi-sub. Does it work?
In this video I show a fairly rough test I ran using the 4 infinite baffle subs that are located in the front wall of my listening room. I also have a smaller sub that I can move around and I put that in 6 different locations to see the results.
Just from measuring the 4 fixed subs I can easily see that the frequency response improved. It was flatter without any of the dips the individual subs had on their own.
Adding in the mobile sub gave a solid boost in the low end, even though the output from that sub is a lot lower than the fixed subs.
So yes, the multiple subwoofer concept is a winner, in that it greatly improves the measured frequency response at the listening position.
However, I did not see a significant difference in the reverb time from one setup to the next. One of the claims for the multi-sub setup is that it can "fix" room modes, but I see no evidence of that. Granted, I didn't run through every possible position for the mobile sub and my fixed subs can't be moved at all. Also, my room is fairly well treated to deal with low frequency reverb and maybe the effect would be more obvious in an untreated room.
I'm inclined to think that if you can effectively nullify a room mode by careful positioning of an additional sub, it's going to be a very tricky task. You'd DEFINITELY need to run measurements to check whether you are actually producing an improvement, and that would take a lot of time.
And after all that, would the improvement be significant? Like I said, I saw NO real difference in the reverb time with each test, but I DID see a significant response improvement.
The 6 locations for the mobile sub were side left, side right, middle of the room, back corner left, back corner right and middle of the back wall. I'm pretty sure the best response was with the sub on the right side, with middle of the back wall a very close second. Since the middle of the back wall is the most suitable, that's where a new subwoofer will go (yes! future build!).
My room is 14' x 14' with an 7' ceiling. The dominant room modes are at around 38Hz and 70Hz. I've done extensive work to acoustically treat the room to reduce the reverb time and I have a few videos on this channel showing what I did, so please check those out.

[michaeltablet]

Thank you! I'm a musician who has been recording, mixing and playing live for over 40 years and I am learning so much from your channel!

[sudd]

testing and experience is important and fun.
my room is limited so i took a chance and went from onw 15" subwoofer to two 10" subwoofers. i lost some max output since they got places at the middle of the sidewalls. but it sounded much better and took up less space for me. i got full dsp so the frequency response was matched and time aligned.
i find that my solution was more flexible and i can recommend it to more people, its basically having shallow mount subwoofers and more of them. my 10" subwoofers cabinets are only 6" deep.

[rjsprojects]

As a person with no real high end audio listening spaces, options I don't know why I find these videos so fascinating.

[acreguy]

I added a second sub and applied some time alignment. I then re-measured with REW and found a huge improvement. One thing that is seldom mentioned is "signal source." After my measurements, I found Netflix to be either really good or just horrible. DVDs and CDs are far more reliable. Streamed content is compressed and totally unreliable. Another bull's eye John! Great videos.

[harbirnain]

I was using two subs 23 years ago when the standard audio magazine mantra was that since human hearing couldn't localise sound below 80Hz, stereo subwoofers were unnecessary. I however found one sub completely unsatisfactory, being quite localisable and with uneven performance. I conjectured that it was because of higher harmonics and room response, which was evened out by using two subs. 23 years later it's now common for magazines to recommend two subs. I continue to use the same subs I've had for 23 years. I would go without a sub entirely than use just one. I'll probably go for four the next time I buy or build subwoofers.

[jimatyeo]

Of course there is the old trick of putting your sub in the listening location and then walk around and hear where it sounds the best and put your sub in that spot. It really works. Plus I have to say again John's 4 way open baffle speakers are one of the most unique and incredible looking speakers out there I have seen. If they sound 1/4th as good as they look, that would be audio heaven. If you haven't watched the build video's they are a must, even if you don't work with wood or a huge audio geek.

[oplkfdhgk]

i have heard that the reason people recommend multiple subs is because it makes the sound more consistent across the room so there isn't like huge dips in bass on some spots while other spots have huge increase in bass.

[SimplestUsername]

The primary trade-off with a stereo multi sub configuration that I'm familiar with is a general dB increase down the on-axis line and Comb Filtering when off-axis.

[Nightjar]

I got a second sub awhile ago and yes through measurements with REW and subjective listening it makes a big difference.
Also what you aren’t showing here is, multiple measurements from different seating areas.
There will be an even bigger improvement there as well.
Multiple subs also even out the bass all throughout the room.

I would take just a of eq at around 77hz and lower it around -3db for a bit clearer bass.

Still looks awesome

Great videos !

[KillerSneak]

Yes it works, as you will have less null spots (from the sanding waves from the 2nd / 3rd / 4th / 5th order - bounces.) so you’re moving more molecules in the room and are cancelling out the null spots (if you set them up right btw).

[FishersShop]

That's interesting. I'm not sure if this is accurate or not, but I was told years ago that since subs output such a low frequency that they are pretty much omni-directional so it doesn't make a significant difference where you have it in the room (depending on the room size and shape, of course). Seeing the measurements was really cool

[Bloozestringer]

To hear this concept implemented well listen to Duke LeJune’s Swarm setup (Kinesis Audio).

[rockett]

more is better in most cases due to acoustic coupling effect . it will increase the pressure so it will increase the volume. bad things can happen like cancelation and standing waves but most times that can be fixed by placement of the speakers

[Audio_Simon]

John, I'm always very impressed by your video quality, especially filming in the workshop. I wonder if you have made, or would make, a video showing us how you film and work at the same time?

[johannjohann]

2 subs sure adds to the cost, and complexity. Funny how most people buy the eqpt. but never do much acoustically in their primary listening room. But stereo subs sounds pretty good too.

[johannjohann]

what a nice stereo setup. thumbs up! cool video

[GregsGarage]

Interesting graphs... I've found that a little EQ bump and 53 and 60 tends to add a little "chest" to the music. Your graphs show a dip in those areas. I suspect that results in a bit more rumble in the low end. With the distance the low freqs take to develop, I would always err for multiple drivers to allow for more coverage across the width of the room... I could be wrong tho! Thanks for sharing all the detail. It's been fun to follow along.

[datdudeinred]

Wish you'd make a full video on your ob's.

[wattspeakers]

Interesting! About a year ago, I had switched my home theater from three x 8" subs to one x 12" sub, (front firing 1/4 into the room facing listener and phase matched), and the single sub crushes the 3 smaller ones, so an opposite effect, out performing the three together by a wide margin. That's not to say anyone is right or wrong, they use multiple subs in theaters and pro sound all the time... I think it may be very application specific.