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Old 13th August 2004, 10:01 PM   #1
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Default Woofer cut off frequency

Want to cut off the low end of a woofer above a sub in the same cabinet. This Peerless driver extends down to about 35Hz left to its own devices and the sub can reach up to 75 Hz. Seems a bad idea to let them crossover this much. Anyone seen formulas for 4 0r 5 way passive crossovers?
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Old 14th August 2004, 06:52 PM   #2
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you can go to this site for crossover part values:

http://www.lalena.com/audio/calculator/xover/

Once you've calculated the parts values required for a crossover in the frequency range that you're talking about and see how much those components are going to cost you you'll realize why no one does it this way: the cost of a dedicated sub amp will be less.
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Old 14th August 2004, 06:59 PM   #3
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Plus, interaction in 5 way passive crossovers can never be modeled, and takes a lot of optimising...
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Old 14th August 2004, 09:27 PM   #4
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That's the issue, there is a dedicated sub. The woofer above it drops down to 35Hz or so crossing into the subs range of 18-75. Maybe I just cut off the subs top end at 35 since it has a variable crossover and volume control?
Thanks for the lalena tip, been there, no 4 way crossover formulas.
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Old 14th August 2004, 11:28 PM   #5
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Ideally, you should cross over low enough so that the woofer (non-sub) is just starting to play notes that can't be localized (i.e. under 70-80Hz, it's not quite exact) so that the sub doesn't sound out of place, but as high as possible because the sub - most likely - can play the same notes under 80Hz or so with less distortion than the woofer can.
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Old 15th August 2004, 12:48 AM   #6
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Quote:
Thanks for the lalena tip, been there, no 4 way crossover formulas.
You don't need it. Use a two-way, with the other sections paralleled onto the woofer.
I don't understand why you'd have a sub amp driving both the sub driver and woofer, though. Normally the sub amp would only be pushing the sub driver (s) and the woofer would be driven by the main L/R amp.

Or do you have the sub amp dedicated to the sub driver and you just need a high pass on the main L/R amp? That would be best handled by an in-line HP filter, between the pre and the amp with separates or in the tape loop with an integrated receiver. A 5.1 or 7.1 receiver/tuner would have the high pass function built in.
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Old 15th August 2004, 12:55 AM   #7
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Quote:
Seems a bad idea to let them crossover this much. Anyone seen formulas for 4 0r 5 way passive crossovers?
Yeah, but the cost and insertion losses in this BW make them an expensive and poor choice performance wise. Nowadays you can buy a superior performing electronic solution for less than the cost of the components, plus you will probably have to wind your own inductors. Anyway, if you want to work it all out for yourself, here's up to 4th order: http://www.mhsoft.nl/spk_calc.asp#crossover

GM
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Old 15th August 2004, 02:56 AM   #8
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Sorry to confuse everyone. This is one large cabinet; tweeters, mid-range, woofer, subwoofer. Subwoofer is driven by a separate electronic crossover up to 75Hz by way of a Leach double barreled 310W amp.(Big transformer and huge caps) Each cabinet has a subwoofer closely aligned spacially with the other drivers.
The other drivers are also driven by a separate Leach double barrel.
Before everyone jumps on the dual sub idea, I already know about the
non directional frequency, etcetera. I have been using two subs in the old system for some years now and find it quite pleasing. Thing is, they're getting to be 10+ years old and want something new.
I want the sound from the cabinet to be one thing, not a boomer box bounced off the back wall or whatever folks do with their subs. Personal preference. Also found lots of movies have different sub info on the left and right channels.
Going to run this beast thru a modified Lexicon THX surround box.

So is there a simple way to cut off the woofers low end so's it doesn't mess with the subs frequency range of 18-75Hz? The Peerless woofer that can cause the problem will drop down to 35Hz without some low end control on that driver.
Many thanks for your suggestions and help.
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Old 15th August 2004, 03:21 AM   #9
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Sure. Just put an electronic high pass before the input of the main L-R amps. You could also achieve the same thing by modifying the amps feedback but it's probably easier for you to do it the 1st way.
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Old 15th August 2004, 03:21 AM   #10
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GM, thanks for the link. Am I missing something on the site? Can find only 2 way networks, but lots of other goodies that will be most helpful.
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