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Richard C., designing a crossover for a woofer without a zobel is much easier than it used to be....if you can use a software program that allows you to specify the actual impedence of the woofer at the crossover point. For example, most Altec 15" woofers have a rising impedence at their midrange, let's say 30 ohms at the desired 1200hz crossover point. Just input 30 ohms into the program and it will tell you the values for the crossover elements. You will of course have to get a published impendence curve for the specific woofer, or measuere it yourself at the crossover frequency.
Ron
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Ron,
Wouldn't it be better to always design WITH a Zoebel network, if you could? It would present a more constant impedance to the xover, plus the series inductor to the LF driver would be much smaller in size, cost, and DCR if the rising impedance was kept lower.
Yes, I can measure and then plug anything I want into my simulation program. It has shown me how to do it so much faster than trial and error.
I can also measure phase shift between the two drivers to help me determine polarity and "approx" time alignment (at xover). Real time alignment is very difficult to do with passive xovers.
Richard C.
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Richard,
1. A zobel will theoretically impair transient response because the capacitor in the zobel stores and then releases some energy. The electrical storage device in a photographic strobe flash is a capacitor, not a battery!
2. The capacitor also interferes with the amplifier's electrical dampening of the woofer.
3. Lastly, the zobel has an "insertion loss", meaning some of the electrical power is lost before reaching the woofer.
For the above reasons, most modern speaker system manufactures avoid the zobel, and just adjust the crossover elements to the actual impedence of the drivers at the crossover frequency when designing the crossover.
Ron
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Ron,
Then it seems to me if you need a better xover than the original, you might want to consider bi-amping.
I will simulate an xover with and w/out a Zoebel network, and see what I find out.
Richard C.
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Richard,
It that your Model 19 in the picture? If so, try listening with the woofer directly connected to the amplifier. Although the crossover driven woofer may have a flat frequency response on axis, its power response into the room dramatically decreases with increased frequency response, due to its reduced dispersion of higher frequencies. Many direct radiating (non-horn loaded) 15" woofers have the flatest power response curve when driven directly. Yes, I know that there will be a peak in the midrange on axis, but with a Model 19 you are listening to the woofer way off-axis unless it is elevated off the floor. Make sure the horn is driven in the same polarity, amp. positive to the red terminal on the HF driver.
Ron
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P.S. Richard,
The HF driver must still be used with the crossover!!!
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No, that is one of my Model 14's sitting on the floor. I had custom 18" high cabinets built to raise these Model 14's up to where I like them. The center of the woofer is at ~28" and the center of the horn is at 43".
I have my Model 19's sitting on 3 1/2" risers.
I have some studying to do...
Richard C.
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Hi Richard,
Even raising them 3.5" doesn't put you on axis with the center of the woofers. Try running the woofers direct; "It can't hurt, and you might like it, honey" WC Fields.
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Hi Richard,
Even raising them 3.5" doesn't put you on axis with the center of the woofers. Try running the woofers direct; "It can't hurt, and you might like it, honey" WC Fields.
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Ron,
The only way I would want to be on axis with the woofer, is if it was one of Altec's Duplex loudspeakers. Since my Model 19's are not duplex, I would rather be on axis with the horn. I don't think I will be raising a 150 lb speaker any higher than a low riser.
I also don't want to bi-amp very much. I recapped the xover and I am very pleased with how they sound. If I built a clone or had a less desirable speaker, I would try bi-amping.
I have some 9842 monitor clones that I may bi-amp, since they are re-coned with a generic kit, and don't sound right.
Richard C.
