MOTM

Is there an easy formula to figure out wavelength (in feet)? I was
reading the spec sheet for some of the cabinets I have and it was
stating 3-6db gains when cabinets are spaced within one half the
wavelength apart. I'm trying to figure out wavelengths for frequencies
120 Hz and lower. Thanks in advance -Nate

Wavelength is inverse to frequency.  So, low frequencies have the longest
wavelengths.  Radio antennas are sized to some multiple of wavelengths.  ANY
two bass cabinets in the same room would be within 1/2 wavelength.  AM
broadcast radio frequencies are in the hundreds of feet.  So, audio would be
MANY times that.
Larry H

----- Original Message -----
From: Nathan Alan Hunsicker <nate@...>
To: MOTM Newsgroup <motm@egroups.com>
Sent: Saturday, January 06, 2001 9:15 PM
Subject: [motm] OT: More of Nate's Stupidity


Is there an easy formula to figure out wavelength (in feet)? I was
reading the spec sheet for some of the cabinets I have and it was
stating 3-6db gains when cabinets are spaced within one half the
wavelength apart. I'm trying to figure out wavelengths for frequencies
120 Hz and lower. Thanks in advance -Nate

> From: Nathan Alan Hunsicker <nate@...>
> Is there an easy formula to figure out wavelength (in feet)? I was
> reading the spec sheet for some of the cabinets I have and it was
> stating 3-6db gains when cabinets are spaced within one half the
> wavelength apart. I'm trying to figure out wavelengths for frequencies
> 120 Hz and lower. Thanks in advance -Nate

if i remember correctly (after hopping around the room in agony trying to
remember this one), the formula is:
v = fw
v is velocity of sound in air at sea level at 20 degrees c in metres per
second (344m/s in this case)
f is frequency in hz
w (or an inverse y which i can't find on my keyboard, pronounced landa) is
wavelength in metres
to swap the formula around, w = v/f
or w = 344/120
so the wavelength at 120Hz is 286cm

does anyone want to back me up on this..?

cheers
paul b

In a message dated 1/6/2001 7:26:25 PM, jlarryh@... writes:

>AM
>broadcast radio frequencies are in the hundreds of feet.  

Yeah, but radio waves travel a bit faster than sound waves (now who's the 
Stooge!).

>So, audio would
>be
>MANY times that.

Just off the top of my head I think the speed of sound (at room temp and near 
sea level) would be about 750 mph. And 750 mph = about 1100 fps (given 
750/3600 = 0.208 mps and 0.208 * 5280 = 1100 fps). So a 1 Hz "tone" would 
have a wavelength of 1100 feet and a 2 Hz "tone" would have length of 550 
feet. So a 20 Hz tone would have a wavelength of about 55 feet and a 30 Hz 
tone (only half way up the first octave of good human hearing) would be about 
36.7 feet. 

Now a "fun" experiment:
Put a 1.1 KHz sine wave through your stereo monitoring system (or stereo for 
that matter) which will have a wavelength of about one foot. It needs to be a 
bit loud (I mean not quiet). Now, slowly walk around the room (or slowly move 
your head around) and you'll hear the peaks and troughs of the sound pressure 
waves.

So Wavelength = velocity of sound (in the given medium)/ frequency

JB

Right you are JB.  I was describing the "electrical signal" wavelength (like
a stupid stooge).
Larry H

BTW, that reminds me of a question a friend of mine (guitar player) asked me
in high school.  I was always the technical guy in the band.  But, this guy
was a real musician and knew the value of a good delay.  He want to know if
he took a lot of wire and rolled it up inside his speaker cabinet if he
could get a delay.  I said, well not much delay or a LOT of wire.  I got a
good chuckle out of that one.

----- Original Message -----
From: <jwbarlow@...>
To: <motm@egroups.com>
Sent: Sunday, January 07, 2001 11:09 AM
Subject: Re: [motm] OT: More of Nate's Stupidity



In a message dated 1/6/2001 7:26:25 PM, jlarryh@... writes:

>AM
>broadcast radio frequencies are in the hundreds of feet.

Yeah, but radio waves travel a bit faster than sound waves (now who's the
Stooge!).

>So, audio would
>be
>MANY times that.

Just off the top of my head I think the speed of sound (at room temp and
near
sea level) would be about 750 mph. And 750 mph = about 1100 fps (given
750/3600 = 0.208 mps and 0.208 * 5280 = 1100 fps). So a 1 Hz "tone" would
have a wavelength of 1100 feet and a 2 Hz "tone" would have length of 550
feet. So a 20 Hz tone would have a wavelength of about 55 feet and a 30 Hz
tone (only half way up the first octave of good human hearing) would be
about
36.7 feet.

Now a "fun" experiment:
Put a 1.1 KHz sine wave through your stereo monitoring system (or stereo for
that matter) which will have a wavelength of about one foot. It needs to be
a
bit loud (I mean not quiet). Now, slowly walk around the room (or slowly
move
your head around) and you'll hear the peaks and troughs of the sound
pressure
waves.

So Wavelength = velocity of sound (in the given medium)/ frequency

JB

In a message dated 1/7/2001 1:03:04 PM, jlarryh@... writes:

>Right you are JB.  I was describing the "electrical signal" wavelength
>(like
>a stupid stooge)

Hey Larry, without setups like that, I'd be like the Maytag repair man around 
here!

John (running to remove several miles of guitar cable from the back of my 
Deluxe) Barlow