Bass Response and concrete floors

I was talking to a Dynaudio dealer the other day and asking about the Confidence 5's in comparison to the rest of the Dynaudio line. The 5's are apparently being cancelled with two new models being released in the Confidence line, based on the Evidence technology.

Anyway, he asked what type of flooring the speakers would be on. I said concrete with thick pile carpeting. He said the bass response on a concrete floor, even with carpeting, would be muted, that the Confidence 5's need a floor with give to produce decent bass. He said that the bass would roll off around 50 Hz on a concrete floor.

I've seen so many very positive comments about the 5's, but I suppose that people who are satisfied may well be using them on a main floor built on joists. The dealer indicated that I'd be a lot happier with the 3's on my floor.

Anybody know why this would be? More importantly, is this a common behavior of floor standers on concrete floors? Is it a general "rule" that if you have concrete floors, you'll get better performance from a high quality monitor? Thanks for any info -Kirk

Many speakers couple to the floor and resonate through the floor. Concreate floors don't resonate (or not at a useful frequency). You could consider a pergo floor over your concrete. I did this in my audio room and it worked remarkably well. I put in an oriental (wool) area rug for some sound absorption, but carpet on the concrete (which is what was originally there) sounded very muted.
This sounds very odd! It seems to me like flex in the floor would hinder the pressurization of the air in the room to get proper bass. Have you ever tried to get real bass in a room with a drop celing? It can't be done IMO. I have always had great sound on concrete floors, this is new to me. If the speakers were designed on a floor using wood joists I suppose they voiced the speaker for that? Any other ideas? Sounds like a perverted tone controll to me. Loudness contour anyone?
I have a concrete floor in my listening room and must admit that my bass was not that super until I added subwoofers and now there is no question about bass. I think the downside of wooden floors is that you then have to worry about boomy midbass. I would believe the salesman, though, if he says one model works better with concrete floors.
I laid a 3/4" sub floor over my concrete floor using furing strips every 12" in my audio/video room. A local dealer suggested this to help the bass travel the room for a realistic feel for movies. I used to have my dedicated audio on a first floor of a house, but now prefer the lower level or basement for isolation reasons such as any outside noise or distractions. The effect is good but not as much as I had thought. I agree with Mg123 about boomy mid bass in that I have never had such a great sounding room. I would take a less forgiving boundry any day and feel no matter the cost put into the room there will always be compromises.
Using the floor to radiate bass is certainly one way of getting bass, but it is a LOUSY way to do it. It means you are driving resonance into the floor (or more accurately, driving the floor into resonance), and the frequency response and transient response will be horrible compared to being on a concrete floor. Be thankful, very thankful, that you have a concrete floor, and wish that you had concrete walls as well. In the meantime, buy a really high quality monitor like the C3, a really good set of stands, and a REL Stadium III; this combination will absolutely blow away the C5, not only in bass but in every other aspect as well.
I agree with Karls, Maxgain, Mg123 that room resonance is usually a poor way to get base. Generally, if you buy well tuned and well designed speakers, you are going to try to use diffusers, ect... to reduce the effects of the room. The problem with relying on your room/floor for bass is that you have no way of knowing what frequencies are going to be reinforced and how big the peak(s) will be. Certainly it is not going to have anything to do with the music and everything with the rather arbitrary dimensions and construction of your room/floor. Nearly all rooms add some bass due to standing waves and generally it's something to remove. Get a speaker that performs well into the low 40hzs or if you are a real bass fan get a sub. Relying on room resonance for bass is going to get you a mushy, flabby, poorly defined lower octive of music. In fact, it won't be music so much as a hum punctuated by an arbitrary peak frequency. You don't want your listening room to resemble typical car audio, eh?

Sincerely, I remain
Agree with Clueless, Karls etc.

Having a resonating floor helps you to feel the bass you don't hear. Take your feet off the floor and you will see what I mean. In some rooms you will not hear low bass, but feeling it is a kind of [poor] substitute.

Having said that, a concrete floor will improve what you do hear. As stated, a flexible floor just sucks bass.
Redkiwi-That can't be, nothing in audio sucks!!! lol

The guys are right. Wood floors equal bloated, poorly defined bass. Kinda like using the loudness button. Concrete will seem to yield less bass, but it will be far more accurate and controled. You are lucky to have the concrete. Somebody else said it, but get monitors that will be good to around 40-50Hz and add a sub or subs below that and you'll have the best of both worlds. I've got a concrete floor and use a pair of Titan II subs with Jaguars. My bass measures and sounds flat to under 20Hz. It is so cool and natural. Really beats to the boom effect.
And now for something completely different. In the brochure "31 Secrets to Better Sound" from Anantgarde USA, it says the opposite. They recommend installing a wooden floor over concrete. He describes concrete as "colder less involving sound" vs. wood as "warmer more compelling". He says concrete imparts a "whitish coloration" to the sound.

He's not talking about a bouncy floor, but a well supported wooden floor, nailing down 2x4s on their sides and covering with hardwood or thick subflooring, then carpet. He says "you want to keep the solidity of the concrete surface, only change it's timbre." That seems to make sense. The guys at Michael Green's told me the same thing.

So does that work? I don't know. Hard to conduct that experiment.I have a concrete floor and I think it sounds pretty good, On the other hand I have a wooden ceiling made of 1x6 interlocking bead board. I may try the wooden floor but I'm worried if the basement ever leaks I'll have water trapped under the floor.

It looks like Krell is the only one so far who has actually done it, but I'm confused by the comment "I agree with Mg123 about boomy mid bass in that I have never had such a great sounding room." Do you have boomy mid bass or does the room sound great?
Herman, they are selling you something, and that something is more bass ("warmth"), but you can't have it for free. You are still going to pay for it in loss of transient response and extra resonance. The fact that they want a slightly different kind of floor only means that they want to shift the resonant frequencies to a different spectrum. There is no magic here: wood floors resonate, concrete pads don't. Yes, some resonances are more euphonic than others, but that doesn't change the fact that they are resonances. Still far better to start with a nonresonant room (note that resonance and reverberation are two entirely different things; a room with good reverberation characteristics does not have to have floor/wall/ceiling resonances at all...) and use subs to create real bass. But I'm not surprised that Avantgarde has this approach; their horns resonate like crazy and I'm sure they are used to tuning their speakers for a (more or less) flat response in spite of the response variations the resonances create. But the time domain isn't fooled by this, and neither is the ear.
Perfectly valid point Herman but i'm not sure were talking about the exact same thing.

This is not rocket science or, if it is, it's not all rocket science. Of course covering cement is going to make a difference. If you have raw cement and go to wood covering you will notice a diff and it usually will be perceived as "warmer". If you have carpet and pad over the cement and then to go to wood the diff will be much less. Especially if the rest of your room surfaces are "warm."

Do you play an instrument? Take an acoustic guitar and and play 18" in front of tile, glass, concrete poured walls, plasterboard, your living room sofa and the sound board of another guitar. What do you like? Surprisingly many people like bright resonant sound. That's why we all sing in the shower - but that's another story. Anyway, it's not a perfect example of a room at higher volume but it will give you the general idea.

There is a difference in trying to add a "shade" to the sound created by your system with room treatment (floors or walls) and trying to extend frequency response of your system using the room. The later is almost always disasterious because it cannot be controlled (the frequency response curve would be anything but straight.) I repeat, if you do not want a speaker that rolls off at 50Hz buy a speaker that does not roll off there! Then treat your room in a manner so that it will effect all bass and treble frequencies somewhat equally and too your liking.

I remain,
Herman, I think the issue being referred to is resonant feedback rather than acoustics. I absolutely agree that if you have a concrete floor then you will get a cooler less involving sound if you do not get the equipment and speaker supports right. For example, I have found with a concrete floor that racks sound much better if they are sand-filled, but sound better if empty on a wooden floor. Better still is to decouple the rack from the concrete floor in a similar way to that you have quoted.
I had a pair of PSB Stratus Gold i's which I used both downstairs (concrete slab w/ carpeting) and upstairs (wood floor with carpeting). Bass downstairs seemed much tighter - punchier even. It was strange, too - downstairs (same room dimensions BTW) I could put them closer to back wall (3 feet or so). Upstairs I needed 6 - 7 feet or else they were your neighbor's kid's aftermarket woofer in the back of his Honda hatchback! Go figure.
As an organist I can tell you that the lowest pedal notes seem to have more punch in concrete floored buildings (yes, obviously different instruments in different buildings, but you get the feel for them after a while, and many are by the same builder).
I have used sub's on concrete floors with spikes. My experience is that the bass is tightened up and sounds very good. The floor gets rid of that flabby mid-bass and I know my sub went below 50hz.
Concrete is the BEST floor to have, period! I've lived in seven different houses and the best sounding room by FAR has been my concrete floored room (carpet covered). The inital transients are better, the decay is much more deliniated and the overall sound is way more real sounding. If you add a serious subwoofer to a concrete floored room, look out! You'll be floored (yes, pun intended!) by how well the bass couples to the room.

I think there are way to many audiophiles that are used to feeling the bass through their feet and their asses, and somehow think this represents "better" bass. IMHO they are dead wrong in their advice when they "dis" concrete.
I have to disagree that concrete is the "best floor". To me that's like saying solid state is the best amplifier (that might be true in some context--but not always). First consider that the speakers AND room work together to make up the listening experience. (of course all components matter--but these two are most significant in this context) How the speakers interact with the room is critical. Look at how much care goes into speaker placement--and it's not all about removing the room anomolies, it's also about working with them. For example, electrostatics must have a somewhat relfective wall behind them to create the imaging/soundfield.

The theory that concrete is best because it does not resonate or absorb base makes some sense, but not much. This theory needs to be taken into the context of the rest of the room. Bass losses are going to be much greater through sheetrock walls than from a wood covered (or pergo as I had mentioned) concrete floor. The concrete under the wood is great that it gives a rigid floor. Concrete as the supporting structure is probably always best. The best studios use concrete to support their floors under the speakers. But the whole floor is not concrete--it's wood. These are also rooms that use speakers with incredible bass response, which brings me to my second point. A non-resonating material (or one that resonates outside the useful audio spectrum) is also unforgiving. If you have near perfect responding speakers--then concrete might work. But again, the rest of the room has to be considered (more on that later). The speakers may need some resonance or warm reflection from a wood floor to sound their best. I think the guitar analogy mentioned above is a good one. The concrete in my opinion will be overly bright, but that is of course subjective and some people may actually like that. However, you don't see many symphonies playing on concrete floors do you? But you do have choral works in stone/concrete buildings like Westminster--hmmm??

The room and the speakers (or orchestra or choir) work in harmony. Westminster has highly reflective surfaces and very long delay times. It creates long delay times that decay relatively long (even with a large audience). But the first few decays are relatively high in terms of dB (only with a full audience). The result works very well for choral music--but you wouldn't want to hear a symphony there (neither would the orchestra players). Now examine some of the finest symphony halls. They also have long delay times, but try to attenuate ones beyond about 60ms as much (or realistically so) as possible. They don't want the echoic sound of Westminster--they want you to be able to hear every instrument. Why is this important when we are talking about concrete. It doesn't attenuate, and can create some real problems--but again, it must be taken into context of the rest of the room. It's possible that there is enough other attenuation, and that the relfection off the concrete does not create a "second sound image". Second sound images are reflections that are preceived as separate from the original sound that we hear.

So, in the end, I would not say that it is impossible to get good or even great sound out of a concrete floor, but it's highly unlikely to get the best sound with just a concrete floor that is not treated in any way (carpet, wood, or synthetic flooring--like pergo).
Abstract7: I would agree that bare concrete is suboptimal from an overall acoustics point of view. However, most concrete floors in homes or studios are going to be padded and carpeted, or covered directly with wood flooring without a subfloor (as mine are). Both these coverings work well. What is being disucssed here is the physical resonance of a suspended floor and the severe damage to frequency response and transient response that accompanies that resonance. There isn't a good-sounding studio in the world that has a flimsy, flexible floor. The huge advantage of concrete pads is that they drain the physical vibration of the loudspeaker cabinet into the ground, and prevent it from causing physical resonance of the floor/walls/ceiling. And that is all we're saying here. The reverberation characteristics of the room are a very important issue, but one that is totally separate from the issue of eliminating loudspeaker-driven, structure-borne vibration and resonance.

It is unfortunately little understood that the physical coupling between loudspeaker and floor can transmit MANY times greater sound energy into the structure than you could EVER achieve through airborne sound transmission. And if it isn't drained into the ground, it's going to reradiate from the structure back into the room. IMO, it is the job of the playback system and listening room to give you what is on the recording in as pure and noncolored a fashion as possible, and the only way to do this is to keep the room from literally being a sound source of its own.
Cant say I'm an expert here, but I recently moved, and have my system on concrete floors/walls. I have placed the boxes to my equipment behind my gear (hidden behind a very large tapestry), I have 2 squares of carpet under each main speaker, and finally some homemade sound panels directly behind each main. I am happy with the response from my mains, and think the bass is damn good. I'm sure every room is different, and equipment acts differenly in each room...but hey, if a salesman wants to actually sell you a less expensive piece, I'd say try it...worse case, exchange for the higher end piece.

Also, my speakers are on spikes...After reading a few other responses, I feel this is important to note!!
I have Vandersteen Fives in a room with a concrete floor partially covered with padded carpet) and the bass is exceptional. The sheetrock walls are judiciously treated with Ecco Tunes and RPG panels. Last night I was recalibrating the Vandy Five subwoofers and using the Radio Shack sound meter (and making adjustments for its non-linearity in the lower registers) measured reasonably smooth response down to 25 hz with a respectable reading at 20 hz.