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#1
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Please help: Jerry-rigging a highpass filter
The speaker setup in my car is weird because I don't have a lot of money to
dump into it yet. I have two tweeters with crossovers on the dash operating off of the deck's amp, and a 12'' subwoofer tube in the trunk with its own amp and crossover. There are no midrange speakers, but I still have the rear speaker wires to work with running from the deck. I tried alpine and polk 3-way 6-1/2'' speakers back there, and they sound horrible when the deck is cranked because the low-end breaks apart. I want to block bass to those speakers without having to buy a crossover. Perhaps there is a way to rig a capacitor to these speakers to block the low end of the signal? Can someone tell me a simple way to block bass with radio shack parts? I want to try two different ranges: blocking everything below 300Hz and below 400Hz. Whichever sounds better I will use. Any help will be appreciated. |
#2
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My guess is that the problem is not the speakers, but the amp in the
headunit running out of juice and clipping. However, as far as an x-over goes, you need to know that one capacitor will only be a 6db/octave crossover, which means that with a 300hz x-over point, it will only be down 6db, and then 150 will be down 12, and 75 will be down 18. I'd suggest something like a 2nd order, or third order crossover. A second order has a capacitor and inductor and has a 12db/octave slope, and a third order has a 18db/octave slope (with three x-over components). Then a 4th order has a 24db/octave slope. This is all immaterial though. For a 400hz x-over point, you are looking at 100uF (this is assuming a 4 ohm nominal load, which is another thing to think about, the impediance of a speaker changes depending on the frequency). For 300hz it's 133uF. I'd suggest getting a good audio quality capacitor from www.partsexpress.com . The dayton 5% tolerance x-over caps are pretty good. If you go with a more than first octave arrangement, you have to start worrying about alignments, etc. Probably not worth it, but here is a calculator to do it with http://www.lalena.com/audio/calculator/xover/ .. Note too that a passive crossover introduces a phase shift, especially with a second order. Note though, that these may block the speaker, but your headunit will still be producing the power to go to them, but it will be absorbed by the capacitor and reproduced as heat (well, in a way, the impediance will rise, so less current will be produced, but that is another discussion), so that won't stop your headunit from distorting. Hope that this helps. Bill wrote: The speaker setup in my car is weird because I don't have a lot of money to dump into it yet. I have two tweeters with crossovers on the dash operating off of the deck's amp, and a 12'' subwoofer tube in the trunk with its own amp and crossover. There are no midrange speakers, but I still have the rear speaker wires to work with running from the deck. I tried alpine and polk 3-way 6-1/2'' speakers back there, and they sound horrible when the deck is cranked because the low-end breaks apart. I want to block bass to those speakers without having to buy a crossover. Perhaps there is a way to rig a capacitor to these speakers to block the low end of the signal? Can someone tell me a simple way to block bass with radio shack parts? I want to try two different ranges: blocking everything below 300Hz and below 400Hz. Whichever sounds better I will use. Any help will be appreciated. |
#3
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Bill wrote:
The speaker setup in my car is weird because I don't have a lot of money to dump into it yet. I have two tweeters with crossovers on the dash operating off of the deck's amp, and a 12'' subwoofer tube in the trunk with its own amp and crossover. There are no midrange speakers, but I still have the rear speaker wires to work with running from the deck. I tried alpine and polk 3-way 6-1/2'' speakers back there, and they sound horrible when the deck is cranked because the low-end breaks apart. I want to block bass to those speakers without having to buy a crossover. Perhaps there is a way to rig a capacitor to these speakers to block the low end of the signal? Can someone tell me a simple way to block bass with radio shack parts? I want to try two different ranges: blocking everything below 300Hz and below 400Hz. Whichever sounds better I will use. Any help will be appreciated. what you need are non-polar capacitors. There is a formula for determining the capacitance here -- http://www.teamrocs.com/technical/pages/twoway.htm Now this shows a two-way setup, but the tweeter section applies to you, only you will be using bigger capacitors to get lower frequencies. -- Dan Snooks |
#4
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In article ,
"Daniel Snooks" wrote: Bill wrote: The speaker setup in my car is weird because I don't have a lot of money to dump into it yet. I have two tweeters with crossovers on the dash operating off of the deck's amp, and a 12'' subwoofer tube in the trunk with its own amp and crossover. There are no midrange speakers, but I still have the rear speaker wires to work with running from the deck. I tried alpine and polk 3-way 6-1/2'' speakers back there, and they sound horrible when the deck is cranked because the low-end breaks apart. I want to block bass to those speakers without having to buy a crossover. Perhaps there is a way to rig a capacitor to these speakers to block the low end of the signal? Can someone tell me a simple way to block bass with radio shack parts? I want to try two different ranges: blocking everything below 300Hz and below 400Hz. Whichever sounds better I will use. Any help will be appreciated. what you need are non-polar capacitors. There is a formula for determining the capacitance here -- http://www.teamrocs.com/technical/pages/twoway.htm Now this shows a two-way setup, but the tweeter section applies to you, only you will be using bigger capacitors to get lower frequencies. Two polarized capacitors of double the capacitance back to back is equivalent and much easier to find in large values. The voltage of each capacitor must be at least as high as the rail voltage of the amp. Simulating a 110 microfarad, 50V, non-polaraized capacitor: + - - + ----|(-------)|----- 220 220 50V 50V |
#5
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Hi Bill. Unfortunately you won't find the *non-polarized * capacitors you need at Radio Shack anymore (probably). I think you might be able to order them from Radio Shack Unlimited, however (special order service). I sometimes build my own 2 & 3 way crossovers and always had to special order them. Also you can try a surplus store called All Electronics (www.allelectronics.com) or maybe Crutchfield as well, although the prices are much higher for those for sale at Crutchfield or a car stereo shop. Good luck. -- MartyMcLeod ------------------------------------------------------------------------ MartyMcLeod's Profile: http://www.caraudioforum.com/vbb3/me...p?userid=34271 View this thread: http://www.caraudioforum.com/vbb3/sh...d.php?t=216619 CarAudioForum.com - Usenet Gateway w/over one million posts online! |
#6
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On Fri, 29 Apr 2005 13:10:43 -0400, Bill wrote:
The speaker setup in my car is weird because I don't have a lot of money to dump into it yet. I have two tweeters with crossovers on the dash operating off of the deck's amp, and a 12'' subwoofer tube in the trunk with its own amp and crossover. There are no midrange speakers, but I still have the rear speaker wires to work with running from the deck. I tried alpine and polk 3-way 6-1/2'' speakers back there, and they sound horrible when the deck is cranked because the low-end breaks apart. I want to block bass to those speakers without having to buy a crossover. Perhaps there is a way to rig a capacitor to these speakers to block the low end of the signal? Can someone tell me a simple way to block bass with radio shack parts? I want to try two different ranges: blocking everything below 300Hz and below 400Hz. Whichever sounds better I will use. Any help will be appreciated. I had the exact same problem, went to an electronics store ready to spend big bucks but they had cheap ($1.5) 68microF/100V NP capacitors and got 12 cheap ones. I used 3 per speaker (important: wire the capacitors in PARALLEL to get 3X68). The difficult part was mounting them so they wouldn't rattle inside the door. Use tape or whatever else you want but be carefull because their cases are not very tough and you can dent them easily (wires and pliers are NO). I am now able to crank up the bass on the HU, the speakers don't sound horrible (guitars have a plenty of body) and my sub in the trunk plays all the bass. If you use 2 caps per speaker you will find noticable bass-reduction at the speaker and I didn't like that. With caps so cheap experiment. -- Leon |
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