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| Comparing components verses comparing systems [message #64206 is a reply to message #64204] |
Wed, 06 October 2010 18:16   |
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Wayne Parham
Messages: 18787
Registered: January 2001
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Illuminati (33rd Degree) |
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The thing is, you have to do some work to optimize a loudspeaker system properly, and you can't really compare the horns until you do. On the other hand, you can make some measurements of the horns by themselves for comparison. This will allow you to make some educated guesses about how each will do when put into a system.
Generally, if the horns are about the same length, width and height, you can expect to have about the same issues when implementing them. There are a lot of other things that are important, of course, including flare rate and profile. But disregarding certain directivity details and other quality metrics for a moment, the basic dimensions have to be somewhat similar to even get close to an apples-to-apples comparison.
The center-to-center distance between the tweeter horn and the next adjacent subsystem (midrange or midwoofer) is largely set by its height. This is a big part of what determines the size of the forward lobe, the distance between vertical nulls. The length of the horn creates a fixed delay, and it's other properties cause it to be partially reactive, especially down low, where crossover usually happens. So these have affect the phase, in part setting the position of the forward lobe and ultimately driving the crossover design which has to take this into consideration. It's not just a matter of splitting out the lows to protect the driver, but it must also provide mass-rolloff compensation and phase manipulation to position the forward lobe.
The bottom line is it is impossible to fully compare the loudspeakers that may be made from two horns without doing some designs and tests. You can compare the horns, but that's not the whole story. If they're similar enough, you can make soem assumptions that will probably hold true. But you won't really know until you've successfully built with them.
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| Re: Comparing components verses comparing systems [message #64215 is a reply to message #64211] |
Thu, 07 October 2010 09:09 |
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Wayne Parham
Messages: 18787
Registered: January 2001
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Illuminati (33rd Degree) |
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When swapping horns, if their size is similar (HxWxD) and their directivity characteristics are similar, then they are at least in the same ballpark. There may be some specific details that require attention, and some crossover changes may be required. But the basic crossover topology should probably be the same.
Generally, you have two common directivity contours, constant directivity being one and collapsing directivity being the other.
Exponential and tractrix horns have collapsing directivity and so those can be considered similar to each other when designing the crossover. Mass rolloff is somewhat equalized with acoustic equalization, at least on-axis.
Conical, radial, oblate and prolate spheroidal and the various proprietary constant directivity designs like Mantarays and BiRadials all provide similar response over a wide arc. There is no acoustic equalization from collapsing directivity so mass rolloff has to be compensated with equalization in the crossover. This is the topology of my crossover designs, having an R1/R2/C1 network for top-octave compensation.
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