coolhandjjl Posted October 18, 2012 Share Posted October 18, 2012 Can a crossover also attenuate a specific range of frequencies of a driver within the bandpass area its coverage? Quote Link to comment Share on other sites More sharing options...
Guest " " Posted October 18, 2012 Share Posted October 18, 2012 it depends on the design. a series notch filter can level off peaks. a parallel notch filter can compensate for dips. P-trap is an example of a series notch filter. Quote Link to comment Share on other sites More sharing options...
coolhandjjl Posted October 18, 2012 Author Share Posted October 18, 2012 Excellent, thanks. I googled around and found DIYaudiovideo that has some on-line calculators to design a parallel notch filter to take a wide hump down a few dBs. Once I get a design figured out, I have to post it, it's going onto the woofer. I am attempting to drop 3 dB from approx 225Hz ~ 500Hz. The resistor called for in the notch filter calculator is roughly 2.5 ohms, but if I am putting several hundred watts into it, I may need help in figuring out how to gang up the resistors to accommodate the high wattage source. I was looking at Erse 25W wirewound in ceramic body resistors. Quote Link to comment Share on other sites More sharing options...
DavidF Posted October 19, 2012 Share Posted October 19, 2012 Excellent, thanks. I googled around and found DIYaudiovideo that has some on-line calculators to design a parallel notch filter to take a wide hump down a few dBs. Once I get a design figured out, I have to post it, it's going onto the woofer. I am attempting to drop 3 dB from approx 225Hz ~ 500Hz. The resistor called for in the notch filter calculator is roughly 2.5 ohms, but if I am putting several hundred watts into it, I may need help in figuring out how to gang up the resistors to accommodate the high wattage source. I was looking at Erse 25W wirewound in ceramic body resistors. A notch filter is really tough to work with without some means to test results. As always you are dealing with changing values in impedance in the circuit. Quote Link to comment Share on other sites More sharing options...
coolhandjjl Posted October 20, 2012 Author Share Posted October 20, 2012 All I have is a mic, RTA software, and a volt meter, but I don't have any test equipment to analyze complicated things like impedence. I can always proceed with the project w/o the notch filter and see if some simple EQing does the trick. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted October 20, 2012 Share Posted October 20, 2012 Excellent, thanks. I googled around and found DIYaudiovideo that has some on-line calculators to design a parallel notch filter to take a wide hump down a few dBs. Once I get a design figured out, I have to post it, it's going onto the woofer. I am attempting to drop 3 dB from approx 225Hz ~ 500Hz. The resistor called for in the notch filter calculator is roughly 2.5 ohms, but if I am putting several hundred watts into it, I may need help in figuring out how to gang up the resistors to accommodate the high wattage source. I was looking at Erse 25W wirewound in ceramic body resistors. A notch filter is really tough to work with without some means to test results. As always you are dealing with changing values in impedance in the circuit. maube someone else has been there and done it...so post the drivers and associated details Quote Link to comment Share on other sites More sharing options...
djk Posted October 21, 2012 Share Posted October 21, 2012 Start with a 260µF composite value cap (Bennic 250µF electrolytic + Bennic 10µF polypropylene), a 2.5Ω resistor (3x 7.5Ω/15W), and 0.8mH (steel laminate 1.0 mH 15 AWG inductor de-wound to 0.8mH). Madisound is the preferred vendor due to their custom inductor service, the parts for a pair of filters will run about $50 with shipping. Quote Link to comment Share on other sites More sharing options...
coolhandjjl Posted October 21, 2012 Author Share Posted October 21, 2012 Thanks for the suggestions. I forgot about Madison Sound. I'll look them up. I am still a newbie at doing RTA, so those values I posted from my bin may change as I get better at doing proper readings. Still confused about the resistor wattage values. Some places I research tell me to go for the highest wattage the amp puts out (that would be a huge wirewound the size of an ear of corn for around $35) other sources indicate to go with smaller rated ones like the Erse wirewound ceramic ones at 25 watts. My purpose is not really pure hi-fi like the Klipsch, Cornscalas, etc. that folks have in a nice living room with dedicated listener seating, rather more of a hopped up PA that approaches hi-fi quality. Doubtful it will ever be in a room larger than 1000 sq ft. Quote Link to comment Share on other sites More sharing options...
djk Posted October 22, 2012 Share Posted October 22, 2012 "Still confused about the resistor wattage values. Some places I research tell me to go for the highest wattage the amp puts out (that would be a huge wirewound the size of an ear of corn for around $35) other sources indicate to go with smaller rated ones like the Erse wirewound ceramic ones at 25 watts. " I recommended a composite resistor rated at 45W, that should be adequate. 45W at 2.5Ω would be about 4.24A, or over 100W into the loudspeaker. at the center frequency of 350hz, or over 200W above or below 350hz. "go for the highest wattage the amp puts out" Recommended by someone that knows not how to calculate the values. Quote Link to comment Share on other sites More sharing options...
coolhandjjl Posted October 22, 2012 Author Share Posted October 22, 2012 The Madison Sound calulator is pretty neat, I get to see dB drops in assorted neighboring frequencies, and adjust the width appropriatly. So two 25W 4.7ohm wirewounds from Madison wired in parralel would give me a resistor of approx 2.3 ohms with a 50 watt rating? Quote Link to comment Share on other sites More sharing options...
djk Posted October 23, 2012 Share Posted October 23, 2012 I use an L-pad as a variable resistor, adjusting it to get the response I want, then measuring the resistance as adjusted, then selecting a fixed resistor. From terminal 3 to terminal 2 will give you and adjustable resistor from 0Ω~8Ω,. 2 to 1 gives 0Ω~40Ω. Pick the closest standard value that is a bit higher, and them parallel it with a value about 10x higher to trim it down. Quote Link to comment Share on other sites More sharing options...
coolhandjjl Posted October 23, 2012 Author Share Posted October 23, 2012 That's a great idea. Thanks. So if I need to get something like 2.7Ω, I parallel a 3.0Ω and a 30Ω. And if my LC values are reasonably correct, it should work. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.