What's the deal with 2" horn exits?

[DaBender]

One thing I've noticed around here over time is that as we start moving up the food chain on speakers, people talk about larger diameter exits on the horns, usually accompanied by comments on how smooth they are on vocals as a result. Obviously, knowing nothing about speaker construction, it seems like a 2" exit would be as easy as a 1" exit to manufacture, yet, looking at the prices, it's obvious there's something else going on that puts these speakers in another league.

 

Anyone care to enlighten me?

[Dookietwo]

 

One thing I've noticed around here over time is that as we start moving up the food chain on speakers, people talk about larger diameter exits on the horns, usually accompanied by comments on how smooth they are on vocals as a result. Obviously, knowing nothing about speaker construction, it seems like a 2" exit would be as easy as a 1" exit to manufacture, yet, looking at the prices, it's obvious there's something else going on that puts these speakers in another league. Anyone care to enlighten me?

 

 

 

This is "generalized". There are some excellent 1 inch exit horns out there.

Most horns are compression horns by nature. The exit can be as much as 1/2 the size of the voice coil of the horn driver. 1 inch exit horns seem to have around 1.4 to 2 inch voice coils. 2 inch exit around 3 to 4 inch voice coils. Larger coils handle more heat/ie. power and can handle lower freq "in general" than their smaller counter parts.

The main reason for going to a larger throat is to reduce distortion. HF distortion is directly related to pressure per square unit of area, so a bigger throat means less distortion. Athough a larger horn throat does struggle at very high freq.

 

"All in all the best horn is one that does the job in the freq. range you need it to work at."

A 3/4 inch exit horn may not be a good fit in a 2 way speaker mated with a 15 inch driver. But a 2 inch exit may provide the lower crossover point and spl to keep up nicely. A larger horn exit gives less distortion at the same crossover freq. This could be what people are calling smooth.

 

I'm not well versed in horns but those are some basic differences. The horn lens design is as important as is the throat size.

 

http://aa.peavey.com/downloads/pdf/qwp1.pdf as an example.

 

The math in designing a good horn is complex and I haven't looked at the current crop of sims. in years.

 

Dookietwo

[agedhorse]

The tradeoff however (there is no free lunch of course) is that the resonance point of a larger (and heavier) diaphragm is lower and may be more obnoxious as well as more comb filtering and phase cancellation anomolies at the higher frequencies (in large part due to the throat dimensions being a larger multiple of the signal wavelength). Also, it's very difficult to get good extended high frequency response out of a typical 2" exit without the use of DSP. This why it's important for designers to pick the correct part for the job, there are definately applications where 1" exits are far superior to a 2" exit device. Many line arrays are good examples of this.

 

Lower crossover frequencies typically call for a larger device with the tradeoffs acrefully considered.