Compression Drivers vs Piezo Horns

[rob1963]

The speakers I've decided to go for contain compression drivers rather than piezo horns, and I was just wondering if someone can explain the difference.

Thanks in advance!

:)

[Vectis]

Google is your friend. Did you go with the Peaveys then Rob?

There are fundamental differences between a tweeter and a compression driver that make them sound different. A tweeter radiates sound more or less directly into the air. There is usually little to control the dispersion of a tweeter other than the front surface of the cabinet in which they are mounted. With careful design tweeters can sound very nice and pretty, but their behavior and polar pattern can be inconsistent. It can also take a lot of power, which eventually translates to size, to make a tweeter loud enough to keep up with larger speakers. Where speakers can be redundant (i.e. more than one speaker can cover a frequency range), the anomalies in tweeter dispersion and frequency response can cause objectionable phase cancellation and comb filtering when multiple devices are used together.

Compression drivers, on the other hand, can have very controllable polar patterns and frequency response characteristics depending upon the type of horn they are coupled to. In addition, the compression driver makes the device much more efficient, so it takes less power to reach a certain SPL. Horns can also be used in multiples due to their controllability. Horns and compression drivers are used in virtually all high power PA applications for these reasons. It's just not practical to use tweeters, especially in the critical 1k to 6k range. Above that tweeters are sometimes used. One issue designers of compression drivers must address is the fact that sound from all parts of the diaphragm must reach the throat of the horn at the same time (in order to be in phase with each other. A device known as a phasing plug, which has a series of different length passages through it is often used to accomplish this, but it's never an exact science. There are side effects to this as well. Some compression drivers develop so much pressure at the throat of the horn that nonlinearities in the compression of the air are introduced. These can cause significant harmonic distortion and is partly responsible for the objectionable sound of some high power horn systems.

While any high power PA application is more surely going to call for horns and compression drivers, studio monitors and stereo speakers tend to rely more on tweeters. They are much less expensive to build and to most people's ears sound better at the typical close listening distances used in near field monitoring. Do not assume, however, that tweeters are "better" than horns. Some of the most expensive and accurate midfield studio monitors in the world use horns and drivers. They are just designed with excruciatingly careful detail.

[rob1963]

Hi Vectis,

Thanks for the info, and yes...I have decided to go with the Peavey pro 15 speakers.

:)

[Vectis]

Good choice. I'm sure you won't be disappointed.

[Tony Scott]

Google is your friend. Did you go with the Peaveys then Rob?

There are fundamental differences between a tweeter and a compression driver that make them sound different. A tweeter radiates sound more or less directly into the air. There is usually little to control the dispersion of a tweeter other than the front surface of the cabinet in which they are mounted. With careful design tweeters can sound very nice and pretty, but their behavior and polar pattern can be inconsistent. It can also take a lot of power, which eventually translates to size, to make a tweeter loud enough to keep up with larger speakers. Where speakers can be redundant (i.e. more than one speaker can cover a frequency range), the anomalies in tweeter dispersion and frequency response can cause objectionable phase cancellation and comb filtering when multiple devices are used together.

Compression drivers, on the other hand, can have very controllable polar patterns and frequency response characteristics depending upon the type of horn they are coupled to. In addition, the compression driver makes the device much more efficient, so it takes less power to reach a certain SPL. Horns can also be used in multiples due to their controllability. Horns and compression drivers are used in virtually all high power PA applications for these reasons. It's just not practical to use tweeters, especially in the critical 1k to 6k range. Above that tweeters are sometimes used. One issue designers of compression drivers must address is the fact that sound from all parts of the diaphragm must reach the throat of the horn at the same time (in order to be in phase with each other. A device known as a phasing plug, which has a series of different length passages through it is often used to accomplish this, but it's never an exact science. There are side effects to this as well. Some compression drivers develop so much pressure at the throat of the horn that nonlinearities in the compression of the air are introduced. These can cause significant harmonic distortion and is partly responsible for the objectionable sound of some high power horn systems.

While any high power PA application is more surely going to call for horns and compression drivers, studio monitors and stereo speakers tend to rely more on tweeters. They are much less expensive to build and to most people's ears sound better at the typical close listening distances used in near field monitoring. Do not assume, however, that tweeters are "better" than horns. Some of the most expensive and accurate midfield studio monitors in the world use horns and drivers. They are just designed with excruciatingly careful detail.

With respect this artical is giving us the difference between a 'Tweeter' and a 'Compression Driver'.

They are not describing a 'Piezo' tweeter here they are discribing a tweeter. A piezo hf driver can be either be mounted on to a horn just like a 'Compression driver' or used as a direct radiator like a 'Tweeter'.

In the same as way you can have a:

12" speaker mounted in a normal relflex cabinet, this would be a direct radiating situation. Like a tweeter.

or

12" speaker loaded on to a horn. The speaker would then act more like a compression driver.

The differences between the two are:

*A piezo works by vibrating at very high frequecies. They are cheap to make but are not nearly as loud or as clean as a compression driver.

*A compression driver works just like a normal speaker in a piston motion but at much higher frequencies than say a 12" speaker. They are more expensive to make but are much cleaner sounding and much more efficient than a piezo. :)

[gillo]

With respect this artical is giving us the difference between a 'Tweeter' and a 'Compression Driver'.

They are not describing a 'Piezo' tweeter here they are discribing a tweeter. A piezo hf driver can be either be mounted on to a horn just like a 'Compression driver' or used as a direct radiator like a 'Tweeter'.

In the same as way you can have a:

12" speaker mounted in a normal relflex cabinet, this would be a direct radiating situation. Like a tweeter.

or

12" speaker loaded on to a horn. The speaker would then act more like a compression driver.

The differences between the two are:

*A piezo works by vibrating at very high frequecies. They are cheap to make but are not nearly as loud or as clean as a compression driver.

*A compression driver works just like a normal speaker in a piston motion but at much higher frequencies than say a 12" speaker. They are more expensive to make but are much cleaner sounding and much more efficient than a piezo. :)

well said;)

[TonyB]

I agree. Piezo horns can sound harsh at higher volumes. When I changed to compression drivers, I noticed a real difference in clarity and wouldn't buy speakers fitted with piezo's now.

[spin mobile disco]

Would say that compression is better in terms of voulme and clarity at very high volume. But at lower volume there is very little difference to my ear. Compression horns are more expensive to repair than piezos and are also more prone to blowing due to large input power than a piezo.

[TonyB]

True piezo's are cheaper but they usually have less protection than a compression driver. Piezo's are usually just wired in parallel with a resister with little protection from excess power but a correctly installed compression driver will be used with a crossover or high pass filter with built in protection against excess power. It is of course dependent on how much care and expense the manufacturer has gone to.

[spin mobile disco]

Usually not much lol

[CRAZY K]

Would say that compression is better in terms of voulme and clarity at very high volume. But at lower volume there is very little difference to my ear. Compression horns are more expensive to repair than piezos and are also more prone to blowing due to large input power than a piezo.

Matt, if your using good makes like Peavey and years ago Goodmans like me I have not had any blow outs with horns other than after about 20 years!!!!!!!!!!!!

I was going to complain to Goodmans but thought hey---ive had me moneys worth about a thousand times!

I have had some smaller maplin type horn drivers and one of those did blow===but even those seem robust---other than fair wear and tear I can only think horns will blow if over powered--thats down to the user not the horn!

CRAZY K

[gillo]

it depends what you wont them for compression drivers are good for us , but many reggae systems use piezos for sizzle in their systems.

[spin mobile disco]

I know quite a few people that have bought second hand speakers in the past , and when there has been a fault most of them have been with blown compression horns. That is what I base my comments on. No doubt caused by over powering by amatuers etc but it does seem to be the most blow thing. But on the same note far less have had problems with piezo's. I have no idea why maybe just one of those things.

[PropellerHeadCase]

Or far less have noticed a problem with the piezos coz they sound somewhat rank to begin with? ;)

[spin mobile disco]

Possibly :)

[TonyB]

Piezo's are pretty robust and can take a caning but they will still pop if fed too much power or if severe clipping is allowed. I have some old twelve inch speakers that have piezo's and they are 9 years old now and still work fine (probably won't now I've said that!) Compression drivers are more sensitive, mine are 30w RMS but as mentioned, as long as you use your kit correctly and look after it, and the speakers have some type of protection built in then they should last.