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Here are some real world measurements made at the 2007 NYC sub shoot out. The distortion numbers and characteristics should help us understand the difference between tapped horn distortion and conventional front loaded horn distortion.

The first distortion graph is the Danley TH-115. This is a tapped horn that uses a single high excursion 15” woofer. Testing was done at 100Wrms input. You’ll notice that distortion is in the 7% to 13.5% range for most of the frequency. However, most people, including myself, would describe Danley bass as being very clean and low. Danley bass tends to sound like it needs to be turned up because the perception is that it lacks the upper harmonic distortion that our brain interprets as loudness. This is one reason why some people prefer direct radiating Scoop horns. Scoops can “sound” louder because of their high distortion in the mid-bass/kick drum range.

The second graph is the EM Acoustic MSE-118 subwoofer horn. This is a more conventional front loaded subwoofer horn that uses a single 18” woofer. It has a sealed and tuned rear chamber to help control cone motion and the low frequency tuning. The testing setup was the same as the TH-115. The thing you’ll notice is the distortion stays below 4% through most of the frequency range. As expected, as you near the flare cutoff of the horn, distortion increases very quickly. Even the TH-115 is not immune (See above graph for TH-115) to this.

More discussion to come on these graphs and what they mean.

Rgs, John

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