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Floor bounce and some terrible ignorance in the audiophool world

Flint

"Do you know who I am?"
Superstar
#1
I’ve read a few articles, forum posts, and social media posts mentioning Dr. Floyd Toole’s claim that controlling floor bounce in a home audio environment isn’t necessary, Why? Because, according to Dr. Toole, ground reflections are the single most common reflection on the planet, something humans evolved to deal with, recognize, and/or unconsciously compensate for when we are listening to all sounds. After all, throughout all human history we have been standing or sitting on the ground and ground reflections are always present in everything which we hear. Since we instinctively deal with ground reflections without awareness, and since it is 100% completely natural and always present, there is no reason to attempt to address floor reflections in a room designed specifically for critical audio reproduction.

Everything Dr. Floyd claims about floor reflections and human nature is true, except the conclusion that always ends this discussion is not true.

Yes, our brains expect to hear ambient reflections from around our bodies and when it is missing it sorta freaks us out and can really ruin a listening experience. Tests where listeners are put in a huge anechoic chamber and played direct recordings of instruments or even listen to a live performer in the chamber resulted in the listeners freaking out, even getting a tad nauseous and experiencing headaches. We NEED ambience because anytime our brains are processing sound, the primary subconscious mental energy is focused on interpreting location information for what we are hearing – where is the primary sound? where am I in relation to the sound? if I need to run from or attack the sound where do I move? If the sound is absent of location cues, such as echo and reverb, our brains instinctively go into panic mode because all of those natural processes are not capable of understanding anything about the location of the sound or the space in which the sound and the listener are located. You may be able to judge the direction of the sound source, but it is harder to understand the distance or whether it is near a surface, if I you are near a surface, or any other of a million aspects of the environment our brains are processing all the time.

So, yes, reflections and reverb are absolutely 100% essential to enjoying reproduced sound.

These facts are why too much absorption in a home listening room can actually make listening to audio uncomfortable, especially after a prolonged period of listening. They are why the now famous LEDE (Live End Dead End) listen room acoustical designs were a simple and reproduceable methods for dealing with room acoustics. They are impetus for my common advice to absorb sound for early reflections and bass trapping only and all other room treatments should be reflective, such as angled reflectors and diffusors are better than adding more absorption.

So, what about Dr. Floyd Toole’s comments about floor reflections?

Well, while it is true some ambient reflective acoustic energy in a room is critical, saying floor reflections should never be treated is insane. AND… and this is important, to some extent Dr. Toole himself addresses floor reflections in his own listening room. He mentions in his book that he puts either a shag wool rug on the floor between his speakers and his listening position OR he moved a large fabric covered ottoman to a location which block, absorb, or break up floor reflections. People show some recent photos of his home listening room and claim they show proof of his commitment to use absolutely no treatment on the floor between his speakers and his listening position. However, in discussions about his room, he says the photos he’s allowed to be released are of his room set up for entertaining, not for listening. He says he is “fortunate” to have furniture which can be easily moved in the space and when listening he moves the sofa or a smaller dedicated listening chair closer to the speakers AND either moved the ottoman in front of his sofa or tosses the large, thick sheep wool rug on the floor in front of the chair. He IS addressing floor reflections in his room! However, he is not going to extreme lengths to eliminate them.

I remember on the old S&V forum where I took a ton of shit from members of other “expert” forums for recommending wood floors for listening rooms over traditional synthetic carpet. If anyone remembers my advice, it wasn’t to have a bare hard floor between the speakers and the seating. Instead, I was saying a room with a wood floor AND strategically placed heavy and thick natural fiber rugs between the seating and speakers is more ideal than carpet. Why? Because carpet has a very specific and narrow set of absorption characteristics which “tunes” the room to have a dead zone in the frequency response of the ambient sound while being extremely live and ambient at other frequencies which the carpet does nothing to control. I was still recommending some floor reflection control where it is most important – early reflections.


Continued...
 

Flint

"Do you know who I am?"
Superstar
#2
…...continuation


So, speaking of ambience being necessary – yes, it is absolutely necessary to our ability to truly enjoy audio and getting completely lost in the sound as if we are not in our own homes. However, if one doesn’t get carried away with deadening the room, there should be plenty of ambience in the room to contribute to the realism of the experience.

Also (and this is super important) musicians, studio engineers, and producers also know how important ambience is. They may or may not understand all the psycho-physio-acoustic reasons why it is critical, but they know what sounds pleasing and what they need to do when making recordings. They always ensure they have appropriate ambience in the recordings either by capturing the proper amount of ambience in the recording environment, or they add ambience in the form of echo, chorus, reverb, and such to the recording and parts in the recording to make it pleasing sounding. Surround sound engineers add ambience to their soundtracks so the experience you see on the screen sound the way the image suggests it should.

In the 1970s serious producers and artists were isolating instruments more and more, deadening the recording spaces, and placing microphones very close to the instruments to isolate them from the room ambience. This allowed them to completely control the mix, placing each instrument and sound perfectly in the virtual sound field they were creating in the studio mixing room, but then they would add after-effects such as reverb, echo, and such to individual tracks or to the complete mix to get the best possible balance. Sometimes they added far too little ambience, and those recordings tend to sound sorta dead, in your face, and strange compared to other recordings of the era which had enough ambience added.

So, with the music and soundtracks you are listening to arriving to you with ambience ALREADY INCLUDED in the audio, having a room which might be too absent of ambience is not as much of a problem. For instance, if the audio was too dead, listening with headphones (which is 100% absent of ambience for the listener) would sound terrible – though probably enticing initially for being so novel and unexpected. Also, modern recordings tend to take advantage of the natural ambience of the room the performer is recording within, so there will be floor bounce ambience already in the feed from the microphones which are not extremely close to the instrument(s).

To the reason I decided to write this tirade – should we completely ignore dealing with the floor reflection of speakers in a real-world listening space? Yes, probably we should, but it should not be the first priority when treating a room AND we probably shouldn’t attempt to completely eliminate it altogether.

That said, floor bounce can introduce very audible problems in what we hear which have NOTHING to do with ambience. A full-range floor bounce (such you’d get off a hard, smooth, solid concrete floor) will be a simple echo which, based on the length of delay after the initial sound from the speaker, will created a huge null at one frequency with smaller nulls at the mathematical multiples of that frequency. It will also create modes at the intervals between the nulls. In essence, there will be a comb-filter effect in the amplitude frequency response of what you hear. Since timber plays a very crucial role in how we perceive quality and accuracy (hence frequency response charts are generally the first thing we learn about an audio product even from very good companies), maintaining the timber of the speakers unaltered by reflections is VERY important.

After the impact on frequency response comes the “smearing” of the waveform in the midrange and treble when reflections arrive within 15-20mS of the original source sound. That distortion is less obvious than frequency response, but it makes all the difference between very pleasing sound and sound that makes you completely forget you aren’t listening to real musicians in your room.

So….

Floor reflections, also known as “the floor bounce,” should not be ignored if you want a great sounding audio system.

To my dismay, this issue has become so confused I’ve seen people promoting the enhancing of the floor bounce based on claims about Dr. Toole’s statements on the issue. I’ve seen the wrong conclusions being repeated online far too often. I’ve also seen people going out of their way to get the strongest floor bounce as possible. I’ve seen photos of listening rooms with wood or tile floors where a rug is placed under the seating but the area in front of the seating left bare. I’ve seen less costly installations where the user placed bare wood, like plywood or MDF, on top of their carpet between their speakers and the listening position. I’ve read claims that the impact on frequency response was vastly outweighed by the “added realism and naturalness” of having the floor bounce which necessary because we live with floor bounce in everything we do. This is flawed, and it is foolish, and it is another example of people getting everything completely wrong rather than relying on the proven truths which have become so commonplace that no one discusses them anymore.

This strange characteristic of human nature to adopt, reinforce, and promote completely backwards thinking because if everyone else is doing it they must be victims of marketing, lies, and stupidity and in fact this contradictory nonsense must be true. It is what drives the popularity of conspiracy theories AND the tribalism we all seem to get behind. I do it too! But I try my best to be open-minded and trust science, experience, and agreement in these principles across a variety of academic, professional, and artistic disciplines.
 
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