Balloon Data for a MultiCell Horn

By Pat Brown

Pat Brown provides balloon data for a multicell horn.

Sooner or later all audio people encounter the multicell horn. Multicells have been around since the middle of the last century, and many can be restored to working condition with a driver upgrade.While I have worked with many multicells over the years, I have never seen any measured balloon data, so I decided to measure an Altec 1005 and provide EASE and CLF data to our readers. The reasons include:

• 1. These are still viable devices and are still in use in many venues.
  

  Multicells are actually individual horns

• 2. Their theory of operation is valid for other horns and loudspeaker arrays.
• 3. Many audio newcomers hear about multicells and may want to know more about them.

One of the supposed advantages of multicells is that the cells can be plugged to modify the coverage pattern. This is easy enough to test, so I measured the device both ways (see below).

A few notes about the data:

• 1. The unit I tested has an Eminence driver. Since yours will likely have something different the sensitivity may vary.
• 2. I did not collect electrical impedance data or do a power test for the same reason. Both of these metrics have been excluded from the data files.
• 3. The main use of the data should be for coverage mapping and not SPL predictions

Even with their drawbacks, multicell horns actually work as well as many contemporary loudspeaker

array designs. If they ever make a comeback in the marketplace (a likely event given audio history) you will already have some measured data on what these devices can do. pb

Download the EASE and CLF Data   http://www.etcinc.us/sample_data.htm

An excerpt from The Quadratic Throat Waveguide by John Murray:

Exponential Horns:

Exponential horns are those where the horn length is exponentially related to the horn area. Once in the proper bandpass region for a given size, an exponential horn presents a fairly consistent acoustical load to its driver. This helps both output level and evenness of frequency response, and is what makes horn designers incorporate this particular horn type into many popular compound horn configurations today. However, the exponential flare causes high frequency beaming, and this is the downfall of the exponential horn.

Multicell Horns:

Multicell horns are simply a group of symmetrical, narrow-dispersion, exponential horns assembled into an array. This approach is better than the high-frequency beaming problems of single, large exponential horns in that their high-frequency loss due to beaming is restricted to much smaller seating segments within the arrays coverage area.

However, they exhibited midrange beaming in both the horizontal and vertical directions and are very expensive to fabricate.