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[Lee Buckalew]

So you have 1,000,000/(10x12)=8333Hz.  So basically below 8.3KHz the horn will start to lose control and it will be wider.

Ivan,
Do you mean it will be taller rather than it will be wider?
10 degrees would be a common vertical while 90 degrees or greater would be a more common width for line arrays.

Lee

[Ivan Beaver]

Ivan,
Do you mean it will be taller rather than it will be wider?
10 degrees would be a common vertical while 90 degrees or greater would be a more common width for line arrays.

Lee

Yes.  Most horns are the wrong size.  Typically they need to be taller than wider.
EV was the first company (that I remember) to start offering this proper ratio-back in the 80s

Many people thought they were being stupid and thought they were "wrong"-because everything they knew was opposite.

But yet THEY were ones who were wrong.

The reason for the proper size relationship is to avoid "pattern flip" in which the pattern is actually 90* off for what you think that it "should be".

Of course the ratio of the horizontal to vertical affects how severe the pattern flip is.  The greater the ratio, the worse the effects of pattern flip.  The closer the patterns are, the lower the effect of pattern flip.

I believe Renkus Heinz was the first to start publicizing this effect back around the turn of the century.

YES-size matters, and often not in the way people have been "taught".

[Ivan Beaver]

There is a downside.  You can't array these speakers in a typical fashion and achieve anything pleasant.

Lee

Totally agreed.

But that does not keep people (and even some manufacturers) from doing so and stating/showing in their brochures how to do it.

You will have some serious interactions in various parts of the patterns as they overlap.

[Lee Buckalew]

Yes.  Most horns are the wrong size.  Typically they need to be taller than wider.
EV was the first company (that I remember) to start offering this proper ratio-back in the 80s

Many people thought they were being stupid and thought they were "wrong"-because everything they knew was opposite.

But yet THEY were ones who were wrong.

The reason for the proper size relationship is to avoid "pattern flip" in which the pattern is actually 90* off for what you think that it "should be".

Of course the ratio of the horizontal to vertical affects how severe the pattern flip is.  The greater the ratio, the worse the effects of pattern flip.  The closer the patterns are, the lower the effect of pattern flip.

I believe Renkus Heinz was the first to start publicizing this effect back around the turn of the century.

YES-size matters, and often not in the way people have been "taught".

This did not answer my question.

Are you saying that the dimension of horn height and the dispersion angle for vertical dispersion are used in a formula that determines the lowest frequency of control for the horns dispersion width? 

I am asking because you referenced the height and the vertical dispersion angle and then used the word "wider" which I would take to mean increase the horizontal angle.

Also, is this true for all waveguides or is this formula for CD horns?

Lee

[Ivan Beaver]

This did not answer my question.

Are you saying that the dimension of horn height and the dispersion angle for vertical dispersion are used in a formula that determines the lowest frequency of control for the horns dispersion width? 

I am asking because you referenced the height and the vertical dispersion angle and then used the word "wider" which I would take to mean increase the horizontal angle.

Also, is this true for all waveguides or is this formula for CD horns?

Lee

Yeah-maybe I wasn't clear.  I was giving 2 examples.

Basically each part of the horn (horizontal and vertical) are figured out separately. 

The thing that causes pattern flip is when one side (vertical or horizontal) starts to lose pattern control before the other.

In the perfect world, they should both lose it at the same time so the pattern expands the same in all directions the same.

The formula is Don Keeles from many years back.

It is basically the mouth exit size.

But there is a "wrinkle" (isn't there always?).

In many horns the last part of the horn is wider than the actual rated pattern.

This is done to "ease" the horn transition and help reduce edge reflections.

So the "effective size" of the horn is not the actual outside edge, but somewhere between where the horn used for pattern control ends and the actual final exit of the horn.

And the number that is derived from the formula is a "basic" number.

As with most things audio, it does not start and stop there-but that number is in the "grey area" or area of transistion, but it does give a good idea.

The problem with the different types of horns is that some horns have VERY different patterns at different freq.

The old exponential horns would get REAL beamy higher in freq, and at that freq the actual coverage pattern was not even close to the rated pattern (that the horn had at lower freq).  But there was more gain up high because of that.

The formula "assumes" that the horn will have the same coverage pattern for all freq, until the horn starts to lose control.

And while it does not apply to every horn, it can be a really good "rule of thumb" or starting point to figure out approx where the horn will have pattern control down to.

Of course the ACTUAL best thing is to measure the horn and look at the polar patterns.  THAT is reality.

But I highly doubt (I could be wrong) that any horn would have pattern control any lower than the number indicates.

[lindsay Dean]

Great explanation Ivan,
Lee , what I meant by "spray bottle" is the pattern control for most horn frequencies are out of control except a limited amount of the bandwidth.

[Lee Buckalew]

Great explanation Ivan,
Lee , what I meant by "spray bottle" is the pattern control for most horn frequencies are out of control except a limited amount of the bandwidth.

Yes, most speakers, even with well designed horns, do not exhibit full frequency range control of directivity.

For CDD the pattern control extends much lower than most would think but you must keep in mind that CDD is a front loaded LF with a horn/waveguide fitted HF.  The CDD driver is unique and patented so. 
Of course the pattern and the degree of control vary by model/size. 

The new XE series stage monitors, which have an additional unique waveguide added that is a fixed part of the cabinet extending out over the LF driver, exhibit pattern control down to about 500Hz. 

Lee

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