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.
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.
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.
Thanks for the lalena tip, been there, no 4 way crossover formulas.
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.
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.
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
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.
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.
Sure, use a line level HP filter between the preamp and the main's amp. 2nd order should be sufficient since the roll off of the woofer increases the effective roll off slope: http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
GM
GM
Interesting concept. My old system is similar to what I'm trying to design now in that there is a subwoofer below the woofers in each cabinet. Somewhere in my old docs is the formula for cutting off the woofers low end with a simple cap across the plus and minus leads at the end of the crossover or directly to the driver. Can't find it. If I tear apart the old cabinet, I could interpolate how to do this again with a different driver. Wife factor prevents this simple solution to a not very complicated problem. Did I mention simple?
Perhaps this is the correct answer.
The simplest kind of crossover is a high pass filter put in series with a driver to block the bass. A capacitor has more reactance to low frequencies than to highs, so a single capacitor reduces the signal to the driver at a rate of 6 dB per octave below the crossover frequency. The crossover frequency is defined as the frequency where the response is down 3 dB. This occurs at the frequency where the impedance of the capacitor equals the impedance of the driver.
The formula for the capacitance in a high pass filter is:
C = 1/(2Pi fXc)
where C is the needed capacitance, f is the desired crossover frequency, and Xc is the capacitive reactance at the the crossover frequency.
If you want a microfarads answer:
C = 159000/(fRt)
f= crossover frequency and Rt = impedance.
C = 159000/ ( (75)(5.5) )
C = 385 Microfarads
Put in series with the plus terminal of the driver after all other crossover components.(5.5 ohms is the measured impedance of my Peerless driver)
Paraphrased from the 1987 version of The Loud Speaker Design Cookbook. Mr. Dickason. Also David Weems.
Comments? Works or not?
The simplest kind of crossover is a high pass filter put in series with a driver to block the bass. A capacitor has more reactance to low frequencies than to highs, so a single capacitor reduces the signal to the driver at a rate of 6 dB per octave below the crossover frequency. The crossover frequency is defined as the frequency where the response is down 3 dB. This occurs at the frequency where the impedance of the capacitor equals the impedance of the driver.
The formula for the capacitance in a high pass filter is:
C = 1/(2Pi fXc)
where C is the needed capacitance, f is the desired crossover frequency, and Xc is the capacitive reactance at the the crossover frequency.
If you want a microfarads answer:
C = 159000/(fRt)
f= crossover frequency and Rt = impedance.
C = 159000/ ( (75)(5.5) )
C = 385 Microfarads
Put in series with the plus terminal of the driver after all other crossover components.(5.5 ohms is the measured impedance of my Peerless driver)
Paraphrased from the 1987 version of The Loud Speaker Design Cookbook. Mr. Dickason. Also David Weems.
Comments? Works or not?
unfortunately its not that easy, the resonance of your peerless woofer means that the impedance isnt 5.5 ohms for the frequency range you're interested in filtering. say the resonance peak is 50 ohms, then the capacitive reactance is pretty small compared with that. rod elliot has an article that deals with the same thing in tweeters. basically you get a peak in the frequency response at resonance because the capacitor isnt effective. have a look at http://sound.westhost.com/lr-passive.htm
go with the line level stuff that GM and Bill suggested. if you feel that 6db is enough you could simply resize the capacitor at the input to the leach amp that drives the peerless etc (i assume it does have a capacitor at the input). same calculations as you've already done, but using the input impedance of the amp.
cheers
go with the line level stuff that GM and Bill suggested. if you feel that 6db is enough you could simply resize the capacitor at the input to the leach amp that drives the peerless etc (i assume it does have a capacitor at the input). same calculations as you've already done, but using the input impedance of the amp.
cheers
Hey goobz,
So yu'all agree the best, simple solution is to take the Leach amp out of the rack, futz around with the amp input capacitance to cut off everything below 75Hz that the amp feeds to these speakers.
The woman in the house gave me that look. You know, the one that says "Should I be calling the doctor?"
On a more practical issue, I opened up the the woofer section of the current cabinet and got to the 125uF cap that is in series with the woofer after the 12dB Butterworth crossover. The purpose of this cap is the same as my present question. I recall testing this system extensively before building the final version. (8 test boxes before final)
That testing revealed the old woofer did not play any frequency above 80Hz. Close enough for me.
Why has this solution worked so successfully for 10+ years? On 4 different amps that have driven the speakers?
I have 2 double barrel Leach amps and 5 other 125 W Leach amps in the current system. One of the 5 is being retired because of this new design. Maybe I just make an electronic crossover for this one problem woofer and drive it with a separate amp. Or maybe I just use the practical old method that has worked so successfully for the past 10 years.
Anyhoo, many thanks for all the suggestions and input. Will test out your suggestions and my old method against each other and report back later. Plan to fully document this system with pics and lots of graphs.
Cheers
So yu'all agree the best, simple solution is to take the Leach amp out of the rack, futz around with the amp input capacitance to cut off everything below 75Hz that the amp feeds to these speakers.
The woman in the house gave me that look. You know, the one that says "Should I be calling the doctor?"
On a more practical issue, I opened up the the woofer section of the current cabinet and got to the 125uF cap that is in series with the woofer after the 12dB Butterworth crossover. The purpose of this cap is the same as my present question. I recall testing this system extensively before building the final version. (8 test boxes before final)
That testing revealed the old woofer did not play any frequency above 80Hz. Close enough for me.
Why has this solution worked so successfully for 10+ years? On 4 different amps that have driven the speakers?
I have 2 double barrel Leach amps and 5 other 125 W Leach amps in the current system. One of the 5 is being retired because of this new design. Maybe I just make an electronic crossover for this one problem woofer and drive it with a separate amp. Or maybe I just use the practical old method that has worked so successfully for the past 10 years.
Anyhoo, many thanks for all the suggestions and input. Will test out your suggestions and my old method against each other and report back later. Plan to fully document this system with pics and lots of graphs.
Cheers
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