how audible is floorbounce?

[morris]

Just like the title says, this question might be simple but I wanted to know what you gentlemen and women think. I did some research online and I find it to be conflicting. Some saying it is audible and some say it is not.
What is your experience on this?

[Sydney]

Re: how audible is floorbounce?

Depends on ( among other things ) the design of the speaker and the proximity and material makeup of the floor or the other reflective surfaces for that matter.
Don Keele ( in one of his CBT papers ) graphically demonstrates the floor bounce effect on a commercial speaker ( REVEL ).
In a related fashion I can hear the effect of a ceiling fan in motions as it modulate the signal bouncing off the ceiling.
( It's the old angle of incidence thang' )

[Tin_Ears]

Re: how audible is floorbounce?

I built a huge spherical sound room lined with a three-feet-thick layer of fluffy cat fur. The cats were already dead.

[Dwight]

Re: how audible is floorbounce?

http://www.enjoythemusic.com/tas/222/editorial.htm

[charlielaub]

Re: how audible is floorbounce?

Why don't you model it and see:

http://audio.claub.net/software/jbabgy/BDBS.html

You can also measure it, but you would need to take the speaker to a parking lot (open space with no nearby boundaries within 50 feet, with a hard surface).

-Charlie

[charlielaub]

Re: how audible is floorbounce?

http://www.enjoythemusic.com/tas/222/editorial.htm

+1

[morris]

Re: how audible is floorbounce?

Why don't you model it and see:

http://audio.claub.net/software/jbabgy/BDBS.html

-Charlie

I actually played with that before I posted. I just wanted to know if it was audible or not inside a room. At least if there were any DBT's done to see whether or not it is audible.

[morris]

Re: how audible is floorbounce?

http://www.enjoythemusic.com/tas/222/editorial.htm

This is a good read. Hmmmm....what to do.

[charlielaub]

Re: how audible is floorbounce?

I actually played with that before I posted. I just wanted to know if it was audible or not inside a room. At least if there were any DBT's done to see whether or not it is audible.

Ah, great! I had a floor bounce issue recently and it was definitely audible. The notch was around 6-9 dB deep.

-Charlie

[dthomas]

Re: how audible is floorbounce?

Depends on high the floor is bouncing :rolleyes:

Seriously if the speaker has a 10db dip due to this then I would say it is going to be audible. Easy way to insure is to design around it.

[Jeff B.]

Re: how audible is floorbounce?

Why don't you model it and see:

http://audio.claub.net/software/jbabgy/BDBS.html

You can also measure it, but you would need to take the speaker to a parking lot (open space with no nearby boundaries within 50 feet, with a hard surface).

-Charlie

I wonder if we are talking about two different things here, as my program won't model what is commonly referred to as "floor bounce" (although one could be created that does). The article linked is discussing it as I have always learned it to be.

"Floor bounce" is a form of comb filtering and is described and diagrammed on page 314 of Everest's "Master Handbook of Acoustics" 3rd edition. It occurs when sound bouncing off the floor arrives at the listeners ears out of phase with the direct arrival creating a null, or usually a big dip in the response.

Despite what the article says, I don't believe it to be especially audible for a couple of reasons. First, although it may show up clearly in an axial impulse response, it is different at every listening height and distance, and as a result the average power response tends to fill it in fairly well. And second, our ears and brains are very used to use listen to sound, especially speach when we are standing, so we are subjected to it all of the time. Because of this we tend to compensate for it very easily.

The best way to avoid it though, if you choose to, in speaker design is to keep woofers close to the floor and be careful of your crossover point to the midrange. It's pretty easy to reduce the bounce effect by doing so.

Jeff B.

[Pallas]

Re: how audible is floorbounce?

You can also measure it, but you would need to take the speaker to a parking lot (open space with no nearby boundaries within 50 feet, with a hard surface).

Alternately, one could compare (listening and measurements) a standard topology with an Allison-style topology (woofer down low, crossover such that the floor bounce for both the mid and woofer are in their respective stop-bands). Wayne Parham's "flanking subs" concept is similar.

A simple spatially averaged sound power measurement will capture the floor bounce differences.

That's one thing I plan on investigating in the next a month or so, because I honestly don't know if it's material. I suspect there will be some measurable advantage to the latter approach, though I have no idea if it'll be audible. It would be cool if others do similar experiments so we could share notes.

[charlielaub]

Re: how audible is floorbounce?

I wonder if we are talking about two different things here, as my program won't model what is commonly referred to as "floor bounce" (although one could be created that does). The article linked is discussing it as I have always learned it to be.
Jeff B.

Jeff,

I thought you were using that three-surface model (I forget who came up with it) and those three surfaces were the floor, one side wall, and the rear wall. Is that not correct?

-Charlie

[morris]

Re: how audible is floorbounce?

Despite what the article says, I don't believe it to be especially audible for a couple of reasons. First, although it may show up clearly in an axial impulse response, it is different at every listening height and distance, and as a result the average power response tends to fill it in fairly well. And second, our ears and brains are very used to use listen to sound, especially speach when we are standing, so we are subjected to it all of the time. Because of this we tend to compensate for it very easily.


Jeff B.

The article sounds convincing to me too. But then, I do not here people say " it was the best sounding bookshelf speakers in the show EXCEPT for the noticeable floor-bounce dip". Which lead me to think that it may not be much of an issue. Still, can someone link me an article of DBT's done to actually study the audibility of floorbounce if there is any?

[Jeff B.]

Re: how audible is floorbounce?

Jeff,

I thought you were using that three-surface model (I forget who came up with it) and those three surfaces were the floor, one side wall, and the rear wall. Is that not correct?

-Charlie

That's correct, I am using three surface boundaries. It's call the Allison Model, after Roy Allison who first developed it. However, this model is different than what is being discussed. The Allison model calculates the power response gain due to boundary reinforcement. There are some dips that develop from this model if the speaker is certain distances from two boundaries, but this is very different from the floor bounce dip. The floor bounce dip is a form of comb filtering on a given axis, it's frequency is determined by the height of the speaker, the height of the listener, the distance on axis between the two, and the triangle these make with the floor. The Allison model does not include the distance to, or height of, the listener, so it can't calculate the floor bounce dip.

Jeff