Quote:
Originally Posted by Charles
I have a question and if it is inappropriate, I apologize. I agree that 130 Hz is an extremely high crossover frequency. This being true, why does Magico crossover its monstrous 15" woofers to the midbass 12" woofers at 120 Hz? Why wouldn't the crossover frequency be much lower? How can a 15" woofer accurately reproduce frequencies in the 120 Hz range, even if the crossover slope is 24 dB per octave?
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130hz is not an EXTREMELY high x-over fq. The 15" size could very well be a 18" or 12" woofer in another design and isn't close to being a monstrous driver in todays or yesterdays woofers. Remember the white polymer cone driver in the Hartley Reference? A 70's design, it was 24 inches in diameter with a mass of only 58 grams. They used them in the double stacked QUAD electrostatic speaker system by Mark Levinson.
It's a common myth that size determines "Woofer Speed", which is false. Read this white paper on the subject written by of the worlds best speaker designers Dan Wiggins:
https://adireaudio.com/wp-content/up...an-Wiggins.pdf
Dan designed all of Apple/Mac speakers, Sonos, and many high end drivers for the best of high-end audio companies.
You can have a short throw, low mass, large cone driver with low inductance like most PA woofers which as I mentioned before that can operate up in the 2-3K hz range with great fidelity. All the great cherished 1940's RCA theater systems still collected by serious audiophiles for their totally realistic bass, mid-bass, and midrange, again crossed over to a multi-cell horn at 2K hz.
Or you can have a high inductance, high mass, long throw design which makes it harder to push the cone and come back quickly to a stop, thus destroying the SQ in the mid-bass area, which is solved by keeping it from reproducing anything above, say...60hz which usually the reason for a x-over point below 80hz. It's all about INDUCTANCE ( think of a very powerful magnet to tightly control the cone of the driver that determines how clean/fast/tight...etc it is.) When JL came out with their W7 subwoofer which is the original Fathom. This type of design they used only one word in their advertisements which was "TIGHT". at a car stereo event that I attended years ago they put the W7 driver in a Volkswagen Beetle for their demo car but the company across the aisle from them would demo their woofer which was much more accurate and Tighter sounding , then they would get done with their demo and tell people to go across and sit in the VW Beetle and then come back and let them know what they thought, and everybody came back and as one guy commented "man that is one boomy subwoofer"
High INDUCTANCE designs act in the same manner of worn-out Springs on a 57 Lincoln Continental as you compress and want the spring to come back and immediately stop, but it doesn't , it goes up and down and up and down till it finally slows down and returns to the original position. The exact same thing happens with speakers of a very small magnet/ high inductance design that cannot control the driver, so the driver doesn't stop moving by the time another signal is put in causing very large amounts of distortion and boom. Sizes of drivers are relevant. Just like the TOTL Legacy Valor, 86K dollar speakers that uses a 14" Midwoofer, 14" Bass, and (2) 12" subwoofers.
So the answer to your question as to how can a 15in woofer accurately reproduce frequencies up to 120-130hz is in the above article. Drop the names Subs,Woofers,Mid-bass and look at only how accurate the driver is in that specific range, no matter what name you call it. All the hundreds of speakers through the years that have used a driver of this size crossed over WAY farther up have done so because they used accurate drivers with very fast transient response. These are designs that don't get "muddy/boomy" when used above 80hz or so. Gold Sound years ago designed their High Fidelity speakers using a quick and accurate JBL/very low inductance figure woofer (usually 15 inches) and they would run them up to 400 Hertz and then it would be crossed over to the mid-range driver which would always run from 400 Hertz to 2,500 Hertz so that there would be no Crossovers in the critical vocal and mid-range area.
We are interested in this discussion. I'm sure Ivan appreciates you asking for his specific input.