Posted by Wayne Parham [ 70.234.159.182 ] on October 25, 2007 at 11:22:15:
In Reply to: Re: 12π basshorn subwoofer - the best yet! posted by Wayne Parham on October 04, 2007 at 18:40:23:
I've measured a handful of basshorns over the years and built a small database of measurements that show distortion at various power levels. This provides an opportunity to compare the 12π basshorn subwoofer with other basshorns.
Below you'll see several response curves of various basshorns. Some have a single driver, others have two. But only one has dual-drivers configured push-pull. This helps isolate the benefits, and to identify them with the push-pull drive. SPL is shown in blue and distortion in violet. Click on a response chart to see a larger view. Pay attention to the distortion curves, which tell the story:
At 100 watts, most have low distortion:
 12π, 100 watts @ 10 meters |  Bassmaxx Deuce, 100 watts @ 10 meters |  Bassmaxx Z5, 100 watts @ 10 meters |
 Fitzmaurice Titan 48, 100 watts @ 10 meters |  Fitzmaurice Tuba 24, 100 watts @ 10 meters |  JTR Growler, 100 watts @ 10 meters |
Still loafing at 200 watts, distortion starts to come up on some but not too bad:
 12π, 200 watts @ 10 meters |  Bassmaxx Deuce, 200 watts @ 10 meters |  Bassmaxx Z5, 200 watts @ 10 meters |
 Fitzmaurice Titan 48, 200 watts @ 10 meters |  Fitzmaurice Tuba 24, 200 watts @ 10 meters |  JTR Growler, 200 watts @ 10 meters |
400 watts is where you really start to see distortion begin to rise. It's not a lot of power, but heat and excursion start to have an effect. Pay attention to the lowest frequencies. Distortion rises from asymetrical cone motion and response shape begins to change slightly from heat.
 12π, 400 watts @ 10 meters |  Bassmaxx Deuce, 400 watts @ 10 meters |  Bassmaxx Z5, 400 watts @ 10 meters |
 Fitzmaurice Titan 48, 400 watts @ 10 meters |  Fitzmaurice Tuba 24, 400 watts @ 10 meters |  JTR Growler, 400 watts @ 10 meters |
Thermal effects are more evident at 800 watts. Distortion is quite noticeable too. The fact that the one push-pull design in this lineup exhibits lower distortion than the others is evidence that cone motion asymmetry is responsible for a great deal of distortion. The push-pull configuration is effective at cancelling this kind of distortion, and horn folds attenuate higher harmonics.
 12π, 800 watts @ 10 meters |  Bassmaxx Deuce, 800 watts @ 10 meters |  Bassmaxx Z5, 800 watts @ 10 meters |
 Fitzmaurice Titan 48, 800 watts @ 10 meters |  Fitzmaurice Tuba 24, 600 watts @ 10 meters |  JTR Growler, 800 watts @ 10 meters |
Thermal effects are clearly evident at 1600 watts. Distortion is much higher too. In fact, most basshorns have distortion louder than the fundamental at low frequencies near horn cutoff at high power levels. Not so with the 12π because of its push-pull drive.
 12π, 1600 watts @ 10 meters |  Bassmaxx Deuce, 1600 watts @ 10 meters |  Bassmaxx Z5, 1200 watts @ 10 meters |
If the cooling plugs aren't properly installed in the 12π, it will not survive a 1600 watt sweep. LABhorns will not survive this test for the same reason, unless cooling plugs are added. With cooling plugs, the thermal effects are minimized, even at this power level.
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