Do Subwoofer Sitting on a Concrete Foundation perform worse?

[rimmi2002]

Hi,

I’ve been reflecting on all the subwoofer setups I’ve done for myself and my family. My experience is purely anecdotal, but across eight different setups I’ve noticed a consistent trend: when subwoofers are not sitting on a concrete slab (for example, when placed on the second floor of a house or on a first floor with a basement below), they tend to deliver a much harder-hitting and cleaner low-frequency (10 to 40-50hz) response. This is true even with relatively small subs that you wouldn’t necessarily expect to perform so strongly in the ultra-low frequencies. I can hear the difference easily and I also have REW measurements that back this up.

For example, I’ve seen small subs on non-concrete floors perform extremely well:

• SVS SB12-NSD in ~5000 cu. ft. hits down to 10 hz with really clean bass ( I was shocked to see this)
• Paradigm Sub15 in ~3000 cu. ft. (hit down to 7hz, best bass I heard, clean and hits you in the chest)
• Monoprice basic 8-inch in ~4000 cu. ft. (couldn't beleive it after it was setup. It sounded better or similar to my 2x FV 18 for low bass)
• Another no-name sub in ~4000 cu. ft. (forgot the detail, but remember thinking this sub sound awesome, and it was a 10" sub from a company I have never heard before)

All of them sounded surprisingly powerful and deep, with REW measurements confirming strong performance below 20 Hz—down to around 7 Hz with the Paradigm and about 10 Hz with the SVS.

In contrast, whenever I’ve placed subwoofers on a concrete slab (common in California homes with single-story designs), the low-end response between roughly 10–40 Hz sounds noticeably underwhelming, even with much larger and more capable subs. For instance, my current setup with two FV18s in a ~4500 cu. ft. space just doesn’t deliver the same kind of low-end impact I would expect. Unfortunately, three of the eight setups with poor bass than expected, I’ve tested have been in my own homes, which have all been single-story, concrete slab grade houses—so I’ve experienced this limitation firsthand.

So my question is:
Am I imagining this and just trying to explain what I think I’m hearing, or is there an actual acoustic/structural reason why subs tend to perform differently in the 10–40 Hz range depending on whether they’re placed on a concrete slab versus a suspended floor? I know the room plays a role, but I couldn't find much difference in some of these room. 2/8 were irregular but 6/8 were standarad rectangular rooms.

 

[kemmler3D]

Well, I would like to see the REW results, would be interesting... but off the top of my head, I can think of two things that might be driving the varied experience:

1) Different rooms are different. Each will have different modes at different places. It might just have happened that you had nulls at the MLP in the concrete slab houses in the bottom octave.

2) Concrete and wood will absorb and re-radiate sound differently. Others have posted anecdotally about bass response being really good in concrete basements, I think. But the upshot is simply that acoustic performance will be different if the absorption spectrum of the room is different. Not predictable whether it will be better or worse simply based on building material.

Or both of the above.

 

[Elkerton]

Our perception of bass is informed by what we feel through the floor as well as what we hear through the ear.

 

[mj30250]

Floating floors will vibrate at their resonant frequencies so in general will transfer much more tactile sensation to and through your seats than concrete will. Depending on your personal preferences and content being played, this could be highly preferred or it could be highly irritating. I have a pair of "small" sealed subs in a living room which sits on a suspended floor over the basement, and during action movies the amount of punch they can throw at you with little effort is impressive. But when my wife puts on HGTV and the entire room shakes when someone closes a door, it's a bit silly

If you are after that extra rumble/punch/etc but are "stuck" with concrete, consider adding more subs, nearfield subs, or transducers under your seating. Some people have also installed floating floors on top of concrete explicitly for this purpose. As already mentioned, the layout of your room relative to your sub positioning will also play a large role.

 

[rimmi2002]

@mj30250 @Elkerton

That makes sense and matches what I’ve been noticing. The tactile sensation is much stronger than I would expect from these subs, and I think having a floor floating on something other than concrete is contributing to that. It feels awesome in TV shows and movies, but not as pronounced in music. Thanks, this really clears things up. To be honest, this is exactly the kind of bass I want—it just sucks that a concrete floor limits it somewhat. I’m sure the room plays a big role too.

By the way, looking at your sig, it looks like you’re running ELX towers with a Horizon center. How are you liking that setup? I’ve been considering the same. Currently, I’m running 3x Sierra 2’s from 2015 (original version).

@kemmler3D

I’ll try to get some measurements posted soon. Just goes to show how much the room impacts bass response.

 

[mj30250]

By the way, looking at your sig, it looks like you’re running ELX towers with a Horizon center. How are you liking that setup? I’ve been considering the same.

I love it. I've had the towers for over three years now and they still impress me every time I listen to them. Like many in this hobby I suffer from upgraditis, but so far the ELXs have kept it in remission, at least as far as that setup is concerned.

 

[JohnnyNG]

Our perception of bass is informed by what we feel through the floor as well as what we hear through the ear.

I think the importance of this is vastly underrated. Real life bass is rarely bereft of feet, chest, etc. tactile sensations to the degree many (most?) home setups are, and concrete floors only make it worse. I'm talking music and not just "dinosaur stomps" and other things audiophiles like to think they're above.

 

[rimmi2002]

@kemmler3D

Here are the REW measurements done at normal listening level for this room. -9dB. Just impressed on me how much room makes a diffrence in bass. Room has a floor underneath it (no concrete anywhere).

Room = ~4000-4500 cu ft. 20' x 22' x 10' (open on one side with ~1500 cu ft Kitchen on side ~10x10x15')

Red = 1x SVS SB12-NSD
Green = Cheap ass ported 8 inch Monoprice sub that came with their original 5.1 monoprice premium speakers that came with enery take clones that monoprice made.

 

[Flaesh]

Here are the REW measurements

Where is the microphone located for these measurements?

 

[rimmi2002]

Where is the microphone located for these measurements?

At MLP about 14 ft away from subwoofer. (subwoofer is in front of the room)

 

[Flaesh]

At MLP about 14 ft away

Interesting. Very little room influence for that distance.

 

[rimmi2002]

yeah beats me too.

This is my little nephew's room, a budding audiophile. He was so excited to show me that his cheap monoprice subwoofer is producing really good bass and I didn't believe him till I visited this week and heard it for myself. Compelled me to do some measurments. Funny the room isn't treated or anything. Just a normal living room open to a nook and kitchen and yet its doing so well.

for me it just goes to show bass is so dependant on the room, but this made me think about all the other setups I have heard and the common thread on where I liked the tactile bass vs not simply came down to concrete slab underneath floor vs. not. Seems like I'm one of those people that really like that tactile bass feeling from the floor and its just missing in my house because of the concrete slab. Gonna explore some actuators now to see if its possible to bring back some of that feeling. I hear crowson actuators are the best...anything else a close second?

 

[Cbdb2]

Floating floors will vibrate at their resonant frequencies so in general will transfer much more tactile sensation to and through your seats than concrete will.

Yes at the resonant freqs but at others no vibration so not flat freq. Its like your sub having resonances, not good.

 

[PGansz]

@kemmler3D

Here are the REW measurements done at normal listening level for this room. -9dB. Just impressed on me how much room makes a diffrence in bass. Room has a floor underneath it (no concrete anywhere).

Room = ~4000-4500 cu ft. 20' x 22' x 10' (open on one side with ~1500 cu ft Kitchen on side ~10x10x15')

Red = 1x SVS SB12-NSD
Green = Cheap ass ported 8 inch Monoprice sub that came with their original 5.1 monoprice premium speakers that came with enery take clones that monoprice made.



View attachment 471430

This is very similar to my cheapo audio engine 8in sub, corner loaded in my living room. Floating red oak, 15x17x9 room with multiple openings. We have no business getting subsonic vibrations in our seats but we sure as heck do. Makes me not want to buy a new house bc the room is so easily excited at low frequencies.

 

[Blew]

I prefer the opposite for music. All floors in my house are suspended floorboards, so bass frequencies resonate through the floorboards and increase decay time which muddies kick drums and bass guitar notes. Not to mention they then carry through to the walls too and resonate through the other rooms of the house, annoying the rest of the family.

So I place each of the subs on a concrete paver, with washing machine vibration pads between the paver and carpet. This adds stable mass under the subs, largely isolating them from the floorboards, which tightens up the bass a lot and gives my family some peace too

 

[Keith_W]

Interesting. Very little room influence for that distance.

Notice how the bass is dropping off like a rock for both subwoofers? I would wager that that floor is acting like a giant bass trap and sucking all the bass out of the room. That "tactile experience" of subwoofers vibrating the floor is actually bass energy energizing the floor instead of pressurizing the listening room. Modes would still form, but the modes are less energetic.

Maybe we need @NTK to make another simulation

 

[NTK]

Maybe we need @NTK to make another simulation

I don't know. May be a bit above my pay grade at the moment. I'd think the difference is in the rigidity of the floor (concrete slab vs wood supported by joists), and to simulate the sound absorption/reflection of a flexible structure is beyond me. Doing this type of analyses is where the submarines guys get their paychecks

 

[SHB]

I have my system in a basement on a giant concrete slab and the bass response is absolutely fantastic.

When you place subwoofers on a concrete slab, you will not get any of the vibrations that you will have by placing a subwoofer on a floor made out of wood. That floor made out of wood will vibrate a lot and color the sound of the base much like a giant acoustic guitar body.

Anytime I have dealt with placing subwoofers on a wooden floor, I have always used.GRAMMA platforms by Auralex & SVS subwoofer feetto absorb any of the bass that would be going into the floor structure.

That all being said, unless the rooms you were listening to the subwoofers in are exactly identical, there’s a lot more going on in the room than just the flooring to determine the sound of the low end. In fact, it’s highly likely that the reason that you didn’t get good base response in different rooms had very little to do with the floor.

 

[Keith_W]

I don't know. May be a bit above my pay grade at the moment. I'd think the difference is in the rigidity of the floor (concrete slab vs wood supported by joists), and to simulate the sound absorption/reflection of a flexible structure is beyond me. Doing this type of analyses is where the submarines guys get their paychecks

When you simulate a listening room, which I have seen you do many times, your walls have perfect reflectivity of 1.0. Would it be possible to change the reflectivity coefficient of one surface, e.g. the floor, to something like 0.5 and simulate the result?

 

[NTK]

When you simulate a listening room, which I have seen you do many times, your walls have perfect reflectivity of 1.0. Would it be possible to change the reflectivity coefficient of one surface, e.g. the floor, to something like 0.5 and simulate the result?

Yes I can. The models support partially reflective walls.