How to calculate amplification of a cone?

gary350 · Oct 21, 2020

Layla said:
I have read on the internet that the horn serves to improve the coupling efficiency between the speaker driver and the air. ... The main advantage of horn loudspeakers is they are more efficient; they can typically produce approximately 10 times (10 dB) more sound power than a cone speaker from a given amplifier output. Higher SPL with less power compression means a more dynamic delivery. Horn mids that work to 300Hz are HUGE. Horns can tend to have a cupped sound when improperly designed. Typically there is greater nonlinearity in the frequency response of a horn compared to a simple cone driver. Those are some of the objective differences. Subjectively, I've heard great horn speakers but I've heard better nonhorn speakers when critical listening at normal volumes is the objective.

There is one other major difference between horns and cone/dome that hasn't been mentioned yet. Horns have a rising on axis (polar) response but maintain a constant power (off-axis) response. Cone/dome has a more constant on-axis response but a falling power response. Cone/dome will sound better on-axis while sitting in the "sweet spot." Horns will sound better in a large or open venue simply because of their better power response.

What is the difference between horn & cone? Is it just the shape?

Both drawing have the same cross sectional area.

If you look at outside concert speakers they are often wooden cabinets with 16 or more square shape wooden horns in the cabinets. Bottom of each horn appears to have a small square speaker.

A horn is really a streamlined speaker it should be much more efficient than a cone.

Nigel Goodwin · Oct 21, 2020

A cone has straight sides, a horn has VERY accurately curved (exponential) sides - nothing like your diagram.

A horn is much more efficient - it's actually an acoustic transformer, and matches the impedance of the speaker to the impedance of the air.

alec_t · Oct 21, 2020

Take a look at this.

shortbus= · Oct 21, 2020

When did the scope of this thread change? In the first post he talked about listening using a cone or horn. Now it seems like it has gone to speakers? Isn't this a first question that goes along with his latest microphone post? The sneaky snoop one?

audioguru · Oct 21, 2020

A cone focuses and concentrates certain frequencies creating an uneven frequency response. The frequencies have nulls and resonant peaks that makes a "horn" sound.

unclejed613 · Oct 21, 2020

you might want to look for acoustic or fluid dynamics sim software... that way you could experiment with various diameters, cross sections and other variables without having to carve up a lot of cardboard...

shortbus= said:
When did the scope of this thread change? In the first post he talked about listening using a cone or horn. Now it seems like it has gone to speakers? Isn't this a first question that goes along with his latest microphone post? The sneaky snoop one?

just like with antenna theory.... the reciprocity theorem

shortbus= · Oct 21, 2020

unclejed613 said:
just like with antenna theory.... the reciprocity theorem

I'm not real sure it works that way. Sound out is different than sound in.

gophert · Oct 21, 2020

shortbus= said:
I'm not real sure it works that way. Sound out is different than sound in.

Exactly, horn speakers efficiently transmit sound directionally by matching the impedence of the air to the speakers voice coil. Much like how a properly designed propeller on a boat matches the power of the engine to the viscosity of the water without cavitation of the water.

a microphone horn (ear) works, as discussed above, like an ocean wave hits a beach (shoaling). Essentially a low amplitude surface wave in deep water moving at high speed approaches a beach with finite depth. The wave slows, the wavelength decreases and the amplitude increases (conservation of energy). Even though the wavelength decreases and velocity decreases, the frequency remains constant.

gary350 · Oct 22, 2020

shortbus= said:
When did the scope of this thread change? In the first post he talked about listening using a cone or horn. Now it seems like it has gone to speakers? Isn't this a first question that goes along with his latest microphone post? The sneaky snoop one?

The mistake I made in the first post was calling my horn a cone. By definition a cone is "ROUND" and tapered like a funnel no matter what diameter is, no matter what the taper angle is, no matter what the length is, no matter if it has closed or open bottom.

I think people are comparing listing devices to speakers.

Reading all the information and links posted people are calling, round shapes, square shapes, rectangle shapes, & other shapes, HORNS. There appears to be no definition what a horn is, except that it is long, longer than wide, 3 to 20 times longer than wide. Exit diameter of a horn determines the low base Hz. Smallest diameter determines the highest Hz. Variation in horn taper determines Hz variations. A very long small diameter section of a horn adds more high frequency. From my stereo days I remember low Hz will travel much farther than high Hz, 1/4 mile away all you hear is base sounds low Hz is lost very quick. Horns with a very long small diameter section adds more high Hz it shoots the high Hz sounds farther away. During WWI & WWII they were listing for low Hz airplane engine sounds 20 miles away.

I am interested in horn receivers not horn transmitters but they probably work identical in reverse. Maybe a long small diameter section horn will also have very good high frequency reception. I could build horns like that but not easy with cardboard. Chip board is flexible but the only chip board I have is empty cereal boxes. We don't eat much cereal it will be 5 years before I have enough chip board to build a large horn. Corrugated material does not bend smooth.

Nigel Goodwin · Oct 22, 2020

gary350 said:
The mistake I made in the first post was calling my horn a cone. By definition a cone is "ROUND" and tapered like a funnel no matter what diameter it is, no matter what the taper angle is, no matter what the length is, no matter if it has closed or open bottom.

I think people are comparing listing devices to speakers.

Reading all the information and links posted people are calling, round shapes, square shapes, rectangle shapes, & other shapes, HORNS. There appears to be no definition what a horn is, except that it is long, longer than wide, 3 to 20 times longer than wide. Exit diameter of a horn determines the low base Hz. Smallest diameter determines the highest Hz. Variation in horn taper determines Hz variations. A very long small diameter section of a horn adds more high frequency. From my stereo days I remember low Hz will travel much farther than high Hz 1/4 mile away all you hear is base sounds low Hz is lost very quick. Horns with a very long small diameter section adds more high Hz it shoots the high Hz sounds farther away. During WWI & WWII they were listing for low Hz airplane engine sounds 20 miles away.

I am interested in horn receivers not horn transmitters but they probably work identical in reverse. Maybe a long small diameter section horn will also have very good high frequency reception. I could build horns like that but not easy with cardboard. Chip board is flexible but the only chip board I have is empty cereal boxes. We don't eat much cereal it will be 5 years before I have enough chip board to build a large horn. Corrugated material does not bend smooth.

As I've repeatedly told you, horns are a specific and highly accurate shape using carefully designed exponential curves - round ones are best (because they are exponential at all angles - but four 'flat' exponential sides work fairly well, and are slightly easier to make (although joining the exponential corners together is still pretty tricky).

Transmitter or receive makes no difference, like any transformer it works either way.

gophert · Oct 22, 2020

Nigel Goodwin said:
Transmitter or receive makes no difference, like any transformer it works either way

I completely disagree. the mode of action is very different.

shortbus= · Oct 22, 2020

gary350 said:
The mistake I made in the first post was calling my horn a cone. By definition a cone is "ROUND" and tapered like a funnel no matter what diameter it is, no matter what the taper angle is, no matter what the length is, no matter if it has closed or open bottom.

I think people are comparing listing devices to speakers.

Reading all the information and links posted people are calling, round shapes, square shapes, rectangle shapes, & other shapes, HORNS. There appears to be no definition what a horn is, except that it is long, longer than wide, 3 to 20 times longer than wide. Exit diameter of a horn determines the low base Hz. Smallest diameter determines the highest Hz. Variation in horn taper determines Hz variations. A very long small diameter section of a horn adds more high frequency. From my stereo days I remember low Hz will travel much farther than high Hz 1/4 mile away all you hear is base sounds low Hz is lost very quick. Horns with a very long small diameter section adds more high Hz it shoots the high Hz sounds farther away. During WWI & WWII they were listing for low Hz airplane engine sounds 20 miles away.

I am interested in horn receivers not horn transmitters but they probably work identical in reverse. Maybe a long small diameter section horn will also have very good high frequency reception. I could build horns like that but not easy with cardboard. Chip board is flexible but the only chip board I have is empty cereal boxes. We don't eat much cereal it will be 5 years before I have enough chip board to build a large horn. Corrugated material does not bend smooth.

That, the only picking up low Hz sound is because a sound wave is not like the elcetrical wave that make the sound FROM a speaker. As the sound/air wave goes down the cone horn what ever you want to call it, the waves get broken up and then the only ones left are the ones that can make it to the small end of the cone, where your listening.

Early on in this thread I said for listening you use a parabolic dish and put the microphone at the center height of the parabola. A parabolic dish redirects the sound waves better and doesn't distort near as much as a cone/horn. That is the same reason all of the distance listening devices on the market use that form. When was the last time you saw anything else being used? Probably back in WW2 like in your original post.

Nigel Goodwin · Oct 22, 2020

gophert said:
I completely disagree. the mode of action is very different.

In what way?, it matches one mechanical impedance to another - so works equally both ways. This is why a PA horn works extremely well as a microphone when used backwards, and is often used in that way for two way PA in factories and workshops.

shortbus= · Oct 22, 2020

Nigel Goodwin said:
often used in that way for two way PA in factories and workshops.

But he is using it outdoors, to spy and eavesdrop on people. Imaging the other sounds birds, cars, etc. He want it to be aim able to pick up one conversation.

atferrari · Oct 22, 2020

I built this one, some years ago. An electret duly amplified (Audioguru's circuit) worked quite well.

When I moved where I live now (an excellent area for testing it), had already become severely hearing impaired so I could not do any valid test.

Too sensitive to wind, bruising and chaffing

atferrari · Oct 22, 2020

Forgot to add that if tomorrow I find the formulas to calculate it, I will post them here.

Nigel Goodwin · Oct 23, 2020

atferrari said:
Forgot to add that if tomorrow I find the formulas to calculate it, I will post them here.

Nice one, bet you had some fun making it

atferrari · Oct 23, 2020

Nigel Goodwin said:
Nice one, bet you had some fun making it

Honestly Nigel, it was simpler than I hoped. To make my hand I built a small one first avoiding corrugated cardboard because something told me that would be not easy to handle.

After cutting the four pieces of solid cardboard (2 mm thick) I started bonding the first two at the mike end, using common vinylic glue. The trick is to use just the necessary for it to bond and dry quickly. I made it in steps of around 10 cm length at a time. Better you make sure you have enough time so nothing will distract you until you complete the first three. In fact I kept the whole thing in my hand, all the time until finished.

Later, if you plan to move in the future, make sure that Liliana (or your local equivalent down there) would not come close to crush it jointly with part of a LED cube

Formulas in the attached Excel. Sorry gary350, they are just to calculate dimensions, not gain. File extension to be brought back to .xlsx

Nigel Goodwin · Oct 23, 2020

atferrari said:
Honestly Nigel, it was simpler than I hoped. To make my hand I built a small one first avoiding corrugated cardboard because something told me that would be not easy to handle.

After cutting the four pieces of solid cardboard (2 mm thick) I started bonding the first two at the mike end, using common vinylic glue. The trick is to use just the necessary for it to bond and dry quickly. I made it in steps of around 10 cm length at a time. Better you make sure you have enough time so nothing will distract you until you complete the first three. In fact I kept the whole thing in my hand, all the time until finished.

Nice one, glad to hear it wasn't as bad it looked

shortbus= · Oct 23, 2020

atferrari said:
Too sensitive to wind, bruising and chaffing

First off very professional looking project. The sensitivity you talk about is why they use parabolas for distance listening. Though some here don't believe.

How to calculate amplification of a cone?

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