I found a vintage speaker pair has quite weird specification. They’re ADS L1590 speakers. Their specification shows they have woofer-to-midrange crossover point at 350Hz. However, the midrange used is merely 2-inch dome!
So, I don’t think this is the -3dB point of the dome midrange. Instead, it might be an actual crossing point between woofer and midrange, I don’t believe there are any 2-inch domes could handle that low frequency. Is my assumption correct?
If so, the next question is about the roll-off. The crossover schematic also shows the filters are second-order configuration on every section. The question is if the second-order high-pass filter was applied to that 2-inch mid-dome at -3dB point of its natural roll-off, the acoustically combined response of the mid-dome (high-pass section of the mid-dome) should be 24dB/octave instead of 12dB/octave (first 12dB from the filter and another 12dB from driver’s natural roll-off). Is my second assumption correct?
So, I don’t think this is the -3dB point of the dome midrange. Instead, it might be an actual crossing point between woofer and midrange, I don’t believe there are any 2-inch domes could handle that low frequency. Is my assumption correct?
If so, the next question is about the roll-off. The crossover schematic also shows the filters are second-order configuration on every section. The question is if the second-order high-pass filter was applied to that 2-inch mid-dome at -3dB point of its natural roll-off, the acoustically combined response of the mid-dome (high-pass section of the mid-dome) should be 24dB/octave instead of 12dB/octave (first 12dB from the filter and another 12dB from driver’s natural roll-off). Is my second assumption correct?
Why not 350 Hz crossing on the 2" mid? It just depends on how much SPL one hope from this. A 12 dB/octave high-pass filter on the dome probably results in a acoustically 24 dB/octave roll-off, because there is the natural roll-off of the dome as you wrote.
Hmm, this ADS L1590 seems is a Braun LS200. I read about it, and saw some measurements in an old German hifi magazine, this speaker performed well.
Edit: here is the test.
http://www.titanstory.de/downloads/VULKAN_III_Test.pdf
Edit: here is the test.
http://www.titanstory.de/downloads/VULKAN_III_Test.pdf
Being produced in the early 70s I assume that the Scandinavians did a very thorough investigation on this exceptional dome.