How a horn amplifies sound (hint: Impedance matching)----make money online

you've probably seen speakers that have

this flared horn shape before maybe at

an outdoor venue or a concert venue or

even an antique piece of audio equipment

like this phonograph at first you might

think that the horn just serves to

direct sound toward listeners which is

true it does that but it also makes the

sound louder and at first you know that

doesn't seem to make sense obviously the

horn doesn't take any power so how can

it actually make the sound louder how

can i amplify sound so in today's video

I want to talk about how this actually

works and how you can use this concept

to better understand electronics first

let's verify my claim that the horn

actually does increase the sound output

coming out of this speaker so I'm going

to use a handheld sound meter here that

reads off in decibels and I'm going to

turn on this amplifier here and just run

some static through the speaker so we'll

turn the static on and just holding the

meter in air we've got about 70 to 71

decibels so now we'll put the horn on

and it's reading about 72 or 73 let's

try the test again with a 1 kilohertz

sine wave and this time I'll hold the

sound meter definitely off axis so that

you can see that the horn is not just

directing sound toward the meter

so we're at about 83 decibels

you

as you heard in the demos the alignment

of this horn on the speaker body makes a

significant difference in the character

of the sound and the volume remember

that a 10 decibel change in sound

pressure level is equal to a perceived

loudness difference of twice as much so

my neighbors can attest that a three

decibel change is pretty significant so

let's take a look in here and see how

this thing is built the speaker has a

magnet and a very rigid dome built out

of a special plastic here and the dome

is connected to a coil that's in the

magnetic field and the dome is suspended

by a fairly rigid piece of plastic so

you can move up and down but it takes a

fair amount of force to do so when the

speaker is running the electrical

current that we put through that coil

causes the dome to move up and down and

it moves quickly enough so that the air

in front of it is compressed and that

compressed region of air expands outward

eventually hitting the camera's

microphone being digitized and sent

through the internet to your speakers

which move and create a pressure wave

which expands out and hits your eardrums

and that's how you're perceiving the

sound so if I suddenly wanted to make

this louder for you what I could do is

make the dome move further so that the

pressure wave created by this would be

much higher in intensity the problem is

that this tiny little cone here is not

in contact with very much air so the

only way that I can make this louder is

by moving the cone further basically

putting more power into it even though

that's not the best thing if we have

this cone much larger than it would be

in contact with much more air and it

wouldn't take as much linear travel to

create that same pressure wave and

that's exactly what this horn is doing

here it's allowing us to take a small

surface a small connection with the air

and making it a much larger connection

the front of this horn let me show you

another demo that will make this clearer

this stick is cantilevered off the edge

of a table and it's connection with the

air around it is not very good so if I

bring my fist down the stick just

bounces away because it isn't really

connected to anything very solidly

however if I put a newspaper across the

stick and make sure that the newspaper

is fairly flat when I hit it with my

fists now the stick actually

because the connection that it has with

the air around it is now much better the

newspaper provided this matching between

the stick and the air that caused so

much energy to be transferred into the

stick that it actually broke you can

think of the dome in this tweeter is

sort of like my fist where it has a lot

of force but the air doesn't put up very

much impedance and so there isn't really

anything to push against the horn

provides this coupling between the very

strong tweeter dome and the very weak

sort of air in other words the speaker

dome is a low impedance device meaning

that it's very strong but it doesn't

supply that strength over a very big

area whereas the air is very high

impedance meaning it doesn't take very

much force to push it but that force

must be distributed over a large area to

have a good effect this concept of

impedance matching shows up in

electronics quite a lot and instead of

thinking about it in terms of force and

area we think about it in terms of amps

and volts and so low impedance device

has high current and low voltage and a

high impedance device has high voltage

and low current but ultimately if your

impedances are matched you have good

power transfer however if you have an

impedance mismatch just like with this

speaker going directly into air you're

going to lose power because the systems

are not well matched to each other and I

think it's helpful to think of them in

physical terms just like with this

speaker system or the stick off the edge

of the bench the shape of the horn

actually affects how it will do its

impedance matching job as well so a very

common profile to have is an exponential

curve and this provides a good impedance

match for many different frequencies

however one downside is that the pattern

of sound that comes out of the horn is

not as even as it could be so there are

other designs that take that into

account another thing you might be

wondering is why this is rectangular it

sure seems like round or square would be

much more sense it would make much more

sense for doing this the answer is just

practicality so since the shape of the

horn does affect where the sound is

directed in most you know clubs and

concert venues everyone's ears are about

the same level vertically off the ground

but people are standing in a fairly wide

horizontal pattern around the speaker

so really just this shape is just set up

to fill that area with sound it doesn't

help to send sound into the ceiling or

into the sky because it will either get

lost or be reflected and not sound as

good another thing you might be

wondering is why not just make the dome

bigger if we have to go through all this

impedance matching trouble with the horn

why not just make this whole thing

larger so that it already has better

coupling with the air kind of like this

speaker here and the answer is that it's

very difficult to make a dome rigid

enough and lightweight enough that we

can move it quickly enough and get high

frequency response and also have good

coupling with the air so having this

whole horn tweeter system is actually a

better overall system in terms of

efficiency than trying to make a very

rigid large tweeter you also might be

wondering why horn tweeters don't show

up at home audio so for example with

this bookshelf speaker there's no horn

up in here this is just a plain old dome

tweeter and the answer is that for home

audio typically the sound pressure

levels aren't high enough to make this

efficiency gain from the horn worthwhile

so if this small dome tweeter is you

know 50% as efficient as a horn tweeter

nobody really cares because you aren't

running enough watts through this to

really matter but if you're running a

concert venue or a club you're basically

very conscious of how many decibels you

get per dollar and you want that number

to be very high so if a speaker can be

much louder effectively much louder just

by putting a plastic horn on it then

that makes a lot of economic sense this

is also a horn speaker that has an

interesting twist to it if we take it

apart you can see that down at the

bottom there that amber yellow colored

piece of plastic is the same as the horn

tweeter we were looking at previous

that's the dome of the tweeter right

there and it's got a horn that comes up

this far and then this piece is just a

hollow plastic cup so it has a folded

audio path so the audio comes out of

this horn hits the inside of this cup

bounces back down to the bottom and then

comes out the front Bell here and the

reason for this is that we still want to

have that good impedance matching from

the tiny little dome that's at the

bottom of the speaker there

and you know the amount of air that's at

the front of this but in order to do

that with an exponential curve it would

take too too much fluid in your space

basically this whole horn would have to

be very long so we compromised a little

bit on the audio quality you'll know

that these things don't sound that great

but we've basically wrapped that

exponential horn up folded it up so that

we can have that all working in a

compact package originally I planned to

show the current and voltage going into

this speaker on the oscilloscope and

then put the horn on an off it and show

that the power transfer was better

through the whole system in other words

the power factor would change meaning

that more total energy was transferred

from the electronics through the speaker

into the air and we can measure that by

looking at the phase of current and

voltage on the scope unfortunately this

didn't work the amount of power that's

lost into the the friction losses of the

suspension in the speaker and the

resistive losses of the coil in here are

so much higher than the amount of energy

that's actually transferred into the air

that the the difference on the scope is

just not even perceptible and I looked

very hard for it the other problem is

that since we're working with fairly

small quantities the speaker has to be

producing an awful lot of noise to make

this measurement happen and so before my

neighbors called the cops on me I didn't

want to continue with you know hundred

decibel experiments here trying to look

for this tiny difference in phase or

whatever so anyway if you try that on

your own I'd be curious if you get it to

work out but I wasn't able to make it

okay I'll probably do another video on

impedance matching focusing a little bit

more on the electronics but I hope this

was a good introduction for you ok see

you next time bye money earning websites, get money online, online earning tips, online earning without investment, earn money online without investment for students, earn money by clicking ads, earn money online without investment, online earn money website, online jobs to earn money, best online income site, top 10 online money earning sites, easy income online, easy online earning, earn money online from home, make money online legit, earn money online free fast and easy, online earning websites list,