I was wondering in reference to folded horns that are 4 feet.
Would length of the horn (4 foot) produce the wavelength somewhere around 200Hz?

If not, how can you measure the horns length to determine the frequency?

Also, if this box was a 4 cubic foot enclosure, what would that be in
horns length? (feet)

Thank you,

Elliot

Risking oversimplification, a horn's performance is determined by its length, its flare shape, its mouth area, its throat area and its radiating diaphhragm, motor and compression. The lowest frequency is determined by its length, which is 1/4 wavelength. The highest frequency is determined by radiator mass and motor strength. Efficiency is determined by motor strength and compression and by its ability to limit directionality and focus the sound with flare size and shape. The shape and ratio of throat to mouth area set the horn's response curve, and small mouths usually result in response curves with ripples unless the horn radiates into fractional space, like from ground planes (2π steradians), wall/ground junctions (π steradians) or room corners (π/2 steradians).

Wayne

I've heard so many debates, ie, some say you can't hear a
20hz - 50hz note inside the car but your neighbors can
hear the bass due to the large wavelength.

Other person will say that good headphones can produce 20hz - 50hz
notes and you can hear it.

Some also say that in order to hear those low frequencies in a movie
theater, one should sit in back.

When we hear low frequencies up close, do we really hear the
actual frequency in question coming from the woofer or
do we hear the actually frequency after the wave has completed
the cycle in which case it has bounced around the room for a bit ?

My personal experience is this. If I hear a car playing low bass
notes from a distance, I don't hear those same low notes if I sit
inside the car, but you do feel the pressure. Are you just
feeling the pressure, but not hearing the actual low frequencies ?

In movie theaters I also hear much lower bass if I sit
in the back vs. sitting in front in which case I hear mostly
tweeters. Same theater I go to and they have the subs up front.

When I put headphones on and listen to a 40hz-50hz tone, I do
hear something like fluttering. Am I really hearing the true 40hz
tone or am I hearing something else ?

But having a chamber large enough for wavelength-scale dimensions is a different matter entirely. The dimensions of the room determine standing wave phenomenon, nulls and peaks. And acoustic devices that require wavelength-scale dimensions like horns and waveguides, one needs larger sizes for deepest bass.

Concerning your other questions:

When you're outside a car, you don't hear the rest of the music so loud - hence the bass become more appearant. When you're in the car, the notes at higher frequencies will tend to mask the bass. So, you feel the bass more than actually hearing it - especially in a listening environment as resonant (& leaky!) as a car.

The 'masking' effect can to a degree explain your theater experience too - higher fequencies tend to loose their power at distance faster than the lower ones. So when you move back from the front/side speakers, the level of bass seems to rise relative to the rest. Furthermore, if you sit close to room bounderies (walls) like way back in the theater certain bass notes will be amplified due to standing wave modes & the higher pressure close to the walls. You can experience exactly the same at home - try turning your hifi up a bit & move about in the room; if you place your head (& thereby ears!) close to a wall, especially the wall opposite the speakers I bet you'll be able to hear the rise in bass level.

OK - the whole question of bass & room behaviour is far more complicated than this, but this answer has become too long already - hope it helped a bit.

Regards, Peter.

My second question was;

If a reflex box is 4 cubic feet, how much feet would that be in a horns point of view? (In terms of feet) Should you just add all the walls together?

Elliot

The volume of a horn is not a direct indicator of its length. It can be very long and narrow, very wide but short or somewhere in between.

Wayne

So I am searching for more insight on the headphone issue, and I found this.........it suggests that we CAN hear low bass from headphones, which doesn't apparently mean that it is producing a 30 foot wave, or at least not with any volume...............? We are hearing the compressions and rarefecations, and not the whole wavelength at once......?

This is an excerpt from a copyrighted article by Doug Blackburn on www.soundstage.com

The entire article is at the link below and was rather interesting. I suggest that you guys may want to read it and see what you think!

"Twenty-five Hertz waves in air are twice as long as 50Hz -- 44 to 48 feet. And 20Hz, the lowest frequency we’re supposed to be able to hear, would clock in around 55 to 59 feet long. Do you need a room with at least one 60-foot dimension in it to hear a real 20Hz in the room? No. Your ears actually pick up sound in a different way, reacting to the compressions and rarefactions that happen in the air as the sound propagates though the room. Twenty Hertz creates 20 compressions and rarefactions per second and your ear will pick that up even if you are listening to headphones that respond to frequencies that low. Otherwise your ear canal would have to be 60 feet long -- we would look rather odd if our heads were 60 feet wide."

The rest of the article, dealing with bass reproduction, is here

http://www.soundstage.com/maxdb/maxdb021999.htm