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Active Crossover Network
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Active Crossover Network
"Bob-Stanton" wrote in message
om Going to an electronic crossover is a good idea if one can't afford a high-end ($2000-$10,000) power amplifier. Not really. An electronic crossover can greatly reduce the distortion of medium priced power amplifiers. As if high price makes an amplifier necessarily more distortion free, or low price means it has to have audible distortion. Just isn't true! With an electronic crossover, medium priced amplifiers can come very close to (or sometimes equal to) the sound quality of high-end amplifiers. The decision to use electronic crossover should be based on points that are irrelevant to amplifier price. For example, the near-universal choice to use electronic crossovers with subwoofers has a lot to do with the costs and inconveniences related to making a passive crossover at say 50 Hz for a 8 ohm speaker that is designed to work with a low source impedance. You can build your own electronic crossover for about $7.00. Below is a schematic of a 2 kHz electronic crossover: From preamp--------------------10K Ohm--------- To low frequency amp | | | 0.01uF | | | Gnd | -----------0.01 uF----- | 10 K Ohm pot --- To high frequency amp | Gnd The above crossover is 6 dB per octave and is designed to work into an amplifier input impedance of 50K Ohms. Potentially problematical given that so many power amps have input impedances of less than 50 K. Since the crossover has only four components, (two capacitors, one resistor, and one pot) it is easy to build. You can build it on a Radio Shack eight phono jack board. Part# 274-370, (cost $2.19). IMO if you are going to do something, do it *right*. This crossover has the advantage over active crossovers, in that it has less distortion. It has less noise, too but in fact noise and distortion from reasonably good, modern electronic crossovers just isn't a problem. Furthermore, we are seeing more and more digital crossovers, and if you drive and load them with digital equipment, they are theoretically free of nonlinear distortion. Here's an example of a good, modern, relatively inexpensive but comprehensive electronic crossover of the digital persuasion: http://www.behringer.com/02_products...X2496&lang=eng The disadvantage is it has only a 6 dB per octave rolloff rate. Only the highest quality (read expensive) drivers can handle 6 dB per octave crossovers. Medium priced tweeters, for example, will distort at higher sound levels. Again price really doesn't have that gosh awfully much to do with it. Once you get past the crappy drivers (which sell for a wide range of prices ranging from low to high) you can find a lot of reasonably-priced drivers with good performance including ability to work with low-slope crossovers. Most drivers require at least a 12 dB per octave rolloff rate. This can be achieved by adding a passive component in series with the woofer and the tweeter. From low side power amplifier------------640 mH---------- | 8 Ohm woofer | Gnd From high side power amplifier ----------10 uF---------- | 8 Ohm tweeter | Gnd The electronic crossover (top) and the passive crossover (above) will combine to give a 12 dB/ octave rolloff to the system. Use the 10K pot to balance the levels of the system. (Pick a tweeter that is 3 dB more efficient than the woofer. For example, a tweeter with 91 dB sensitivity, and a woofer with 88 dB sensitivity.) With the money you save by building your own electronic crossover, you could buy high quality drivers from Madisound. In fact one of the major costs associated with using electronic crossovers is the double or tripled number of power amps, and using dirt-cheap hyper-simple electronic crossovers won't help you with that! Vifa, Audax and Morell all make good drivers, that are not too expensive. Agreed about Vifa and Audax. If you don't like woodworking, you could, go to the Salvation Army Store or a garage sale, and buy some old bookshelf speakers. Rip out the old drivers and put in high quality ones. This can work. You can also often find speaker enclosures as surplus parts. You will need to do some homework to be sure you get the correct drivers/enclosure combination. Other than that, this is a no-fail recipe :-) Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. Here's your chance to invest in measurement and analytical tools! The good news is that they are far less costly today than they were years ago. If you want to have a lower crossover frequency you can increase the size of capacitors and inductor. For example, doubling the size of the capacitors and the inductor (to: 0.02 uF, 0.02 uF, 20 uF and 1280 mH) will drop the crossover frequency down to 1000 Hz. If you want two good small two-way speakers, you will probably save money (not to mention time!) in the end by looking at speakers from manufacturers like Paradigm, NHT, PSB. Boston Acoustics, etc. |
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#3
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Active Crossover Network
"Arny Krueger" wrote in message
As if high price makes an amplifier necessarily more distortion free, or low price means it has to have audible distortion. Just isn't true! Which of the low priced amplifiers is totally transparent? Do you have this information on your website? For example, the near-universal choice to use electronic crossovers with subwoofers has a lot to do with the costs and inconveniences related to making a passive crossover at say 50 Hz for a 8 ohm speaker that is designed to work with a low source impedance. That's right. For a *very* low frequency crossover (60 hz), the component cost is high. However, the cost of components, for a 2kHz crossover, is low. Potentially problematical given that so many power amps have input impedances of less than 50 K. One should check for conventional input impedance (50k to 100K) before buying. Since the crossover has only four components, (two capacitors, one resistor, and one pot) it is easy to build. You can build it on a Radio Shack eight phono jack board. Part# 274-370, (cost $2.19). IMO if you are going to do something, do it *right*. What is wrong with building a crossover on a Radio Shack phono-jack board? This crossover has the advantage over active crossovers, in that it has less distortion. It has less noise, too but in fact noise and distortion from reasonably good, modern electronic crossovers just isn't a problem. Yes, active electonic crossovers have very very low distortion. All I said was, passive electronic crossovers have lower distortion. OK, it doesn't matter, but they do have lower noise and distortion. Here's an example of a good, modern, relatively inexpensive but comprehensive electronic crossover of the digital persuasion: *Very nice*, but not for an $800 budget. Again price really doesn't have that gosh awfully much to do with it. Once you get past the crappy drivers (which sell for a wide range of prices ranging from low to high) you can find a lot of reasonably-priced drivers with good performance including ability to work with low-slope crossovers. Again, price doesn't matter if you *know* which cheap drivers are the good ones. Do you have this information on your website? Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. Going to an electronic crossover *greatly simplifies* the design problem. Here is how to design a speaker system using an electronic crosover: 1) Stick to a two-way system. (If you want three-way system, buy a subwoofer with an integrated amplifier, and make your satellite speakers two-way.) 2) Buy a woofer that is of good quality from Vifa, or Audax or Scan-Speak. Pick drivers that don't require a compensating network to be flat. 3) Pick a woofer that is designed to work into a closed box. (Avoid buying woofers that need to work into ported enclosures.) 4) Note what volume enclosure the manufacture recommends, and buy or build, a *sturdy* enclosure of *that* volume. Fill it lightly with (acoustic) fiberglass. 5) If the tweeter isn't sealed on the back, mount it in a seporate enclosure. 6) Solder a series resistor-capacitor across the driver terminals. ------------------------------ | | R = 8 Ohms | | 8 Ohms driver. (Woofer or Tweeter) C | | | ------------------------------ The value for C depends on the inductance of the driver. For the typical (8 Ohm) woofer, the value of C = 15 uF. For the typical (8 Ohm) tweeter, the value of C = 1 uF Here's your chance to invest in measurement and analytical tools! The good news is that they are far less costly today than they were years ago. I agree. Cooledit for $69 has an excellent little spectrum analyzer. If you want two good small two-way speakers, you will probably save money (not to mention time!) in the end by looking at speakers from manufacturers like Paradigm, NHT, PSB. Boston Acoustics, etc. Are prebuilt speaker system as low cost as similar ones you build yourself? I doubt it. Bob Stanton |
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#4
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Active Crossover Network
"Bob-Stanton" wrote in message
om "Arny Krueger" wrote in message As if high price makes an amplifier necessarily more distortion free, or low price means it has to have audible distortion. Just isn't true! Which of the low priced amplifiers is totally transparent? A couple of points. (1) I didn't say totally transparent, I said "more distortion" and "more distortion free". (2) At this point there is no formal definition of "low-priced" Do you have this information on your website? For example, the near-universal choice to use electronic crossovers with subwoofers has a lot to do with the costs and inconveniences related to making a passive crossover at say 50 Hz for a 8 ohm speaker that is designed to work with a low source impedance. That's right. For a *very* low frequency crossover (60 Hz), the component cost is high. However, the cost of components, for a 2kHz crossover, is low. Right and at that crossover point, electronic crossovers don't generally make much sense, except for systems with more dynamic range than a typical home system. Potentially problematical given that so many power amps have input impedances of less than 50 K. One should check for conventional input impedance (50k to 100K) before buying. One then finds a lot of power amps with input impedances in the 5-20K range. Since the crossover has only four components, (two capacitors, one resistor, and one pot) it is easy to build. You can build it on a Radio Shack eight phono jack board. Part# 274-370, (cost $2.19). IMO if you are going to do something, do it *right*. What is wrong with building a crossover on a Radio Shack phono-jack board? Most the limitations forced on it because its passive. This crossover has the advantage over active crossovers, in that it has less distortion. It has less noise, too but in fact noise and distortion from reasonably good, modern electronic crossovers just isn't a problem. Yes, active electronic crossovers have very very low distortion. All I said was, passive electronic crossovers have lower distortion. OK, it doesn't matter, but they do have lower noise and distortion. The we agree. Here's an example of a good, modern, relatively inexpensive but comprehensive electronic crossover of the digital persuasion: *Very nice*, but not for an $800 budget. Buying twice or three times as many power amps pretty well creams a $800 system budget. Interestingly enough, a $800 system based on better quality parts from the PC monitor or One Box Home Theater market segment would probably end up with an active crossover. Please see my 7/16 post about subwoofers. Again price really doesn't have that gosh awfully much to do with it. Once you get past the crappy drivers (which sell for a wide range of prices ranging from low to high) you can find a lot of reasonably-priced drivers with good performance including ability to work with low-slope crossovers. Again, price doesn't matter if you *know* which cheap drivers are the good ones. Do you have this information on your website? Nope, because my knowledge of the area is not up to the standards for my websites. But I've experimented and looked around enough to have an idea about what can be done. Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. Going to an electronic crossover *greatly simplifies* the design problem. Well, at the cost of the extra amplifiers, which in a $800 total system cost for a system assembled by a consumer, makes things pretty tough. Here is how to design a speaker system using an electronic crossover: 1) Stick to a two-way system. (If you want three-way system, buy a subwoofer with an integrated amplifier, and make your satellite speakers two-way.) Right, and at $800 system cost, it is probably best to stick with passive 2-way speakers. 2) Buy a woofer that is of good quality from Vifa, or Audax or Scan-Speak. Pick drivers that don't require a compensating network to be flat. Again, Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. Most experiences speaker builders agree with this. I admit that I'm working on a high-performance 2-way design, but it exceeds most commercially-available 2-ways a number of ways, mostly relating to frequency response extension and dynamic range. Also, the total system price that goes with it will be far in excess of $800. I 3) Pick a woofer that is designed to work into a closed box. (Avoid buying woofers that need to work into ported enclosures.) ???? 4) Note what volume enclosure the manufacture recommends, and buy or build, a *sturdy* enclosure of *that* volume. Fill it lightly with (acoustic) fiberglass. Most manufacturers of quality woofers provide T/S parameters and leave the design up to the purchaser. 5) If the tweeter isn't sealed on the back, mount it in a seporate enclosure. Nope, just don't buy it. 6) Solder a series resistor-capacitor across the driver terminals. ------------------------------ | | R = 8 Ohms | | 8 Ohms driver. (Woofer or Tweeter) C | | | ------------------------------ The value for C depends on the inductance of the driver. For the typical (8 Ohm) woofer, the value of C = 15 uF. For the typical (8 Ohm) tweeter, the value of C = 1 uF Zoebels are for people who don't get it. Here's your chance to invest in measurement and analytical tools! The good news is that they are far less costly today than they were years ago. I agree. Cooledit for $69 has an excellent little spectrum analyzer. Been there done that and I wouldn't recommend it to even someone I don't like. If you want a superior tool for lots less money, check out http://audio.rightmark.org/ Scroll down the download page to Rightmark AE. Its better than CEP for the purpose, but I could write quite a bit about its strengths and weaknesses. If you want two good small two-way speakers, you will probably save money (not to mention time!) in the end by looking at speakers from manufacturers like Paradigm, NHT, PSB. Boston Acoustics, etc. Are prebuilt speaker system as low cost as similar ones you build yourself? I doubt it. The price/performance and time investment is hard to beat. Again, Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. |
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#5
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Active Crossover Network
"Arny Krueger" wrote in message news:bIKdnRc-
(1) I didn't say totally transparent, I said "more distortion" and "more distortion free". Two amplifiers, driven by an electronic crosover, are even more distortion free yet. :-) (2) At this point there is no formal definition of "low-priced" How about under $200? Buying twice or three times as many power amps pretty well creams a $800 system budget. Interestingly enough, a $800 system based on better quality parts from the PC monitor or One Box Home Theater market segment would probably end up with an active crossover. Please see my 7/16 post about subwoofers. Staying within an $800 budget is not tough. Two, low cost, sterio amplifiers: $400 Passive electronic crossover: $ 20 Two Vifa woofers at $100 each: $200 Two Vifa TG 27 tweeters at $30 each: $ 60 Two old enclosures from a garage sale: $ 20 Total: $ 700 Well, at the cost of the extra amplifiers, which in a $800 total system cost for a system assembled by a consumer, makes things pretty tough. 3) Pick a woofer that is designed to work into a closed box. (Avoid buying woofers that need to work into ported enclosures.) ???? Because making a ported enclosure work right, is more difficult than just sticking a closed box driver, in the proper box. Most manufacturers of quality woofers provide T/S parameters and leave the design up to the purchaser. Manufactures give a "VB ltrs" spec. Isn't that the recommended box volume? Zoebels are for people who don't get it. I'm one who doesn't "get it". Zoebel networks convert the driver terminal impedance to a resistance. That improves the crossover's rolloff characteristics. Zoebel's are simple, cheap, and work darn well. The price/performance and time investment is hard to beat. Investing time, saves money. Bob Stanton |
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#6
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Active Crossover Network
"Bob-Stanton" wrote in message
om "Arny Krueger" wrote in message news:bIKdnRc- (1) I didn't say totally transparent, I said "more distortion" and "more distortion free". Two amplifiers, driven by an electronic crossover, are even more distortion free yet. :-) All you have to do is reduce distortion to the point where it is inaudible. Easy enough to do in the 21st century - without active crossovers. (2) At this point there is no formal definition of "low-priced" How about under $200? In terms of stand-alone power amps that does not leave a lot to select from. Buying twice or three times as many power amps pretty well creams a $800 system budget. Interestingly enough, a $800 system based on better quality parts from the PC monitor or One Box Home Theater market segment would probably end up with an active crossover. Please see my 7/16 post about subwoofers. Staying within an $800 budget is not tough. Two, low cost, stereo amplifiers: $400 Passive electronic crossover: $ 20 Two Vifa woofers at $100 each: $200 Two Vifa TG 27 tweeters at $30 each: $ 60 Two old enclosures from a garage sale: $ 20 Total: $ 700 This isn't a system. Well, at the cost of the extra amplifiers, which in a $800 total system cost for a system assembled by a consumer, makes things pretty tough. 3) Pick a woofer that is designed to work into a closed box. (Avoid buying woofers that need to work into ported enclosures.) ???? Because making a ported enclosure work right, is more difficult than just sticking a closed box driver, in the proper box. IME, no. Either way, the best way is to optimize the driver & box combination using Thiel/small parameters and verify with actual measurements. Most manufacturers of quality woofers provide T/S parameters and leave the design up to the purchaser. Manufactures give a "VB ltrs" spec. Isn't that the recommended box volume? Here's a sample set of data for a Vifa woofer from the manufacturer's web site. http://www.d-s-t.com/vifa/data/tc08sd49-04d.htm Now maybe you can find Vb here, but I sure can't. I can find Vas, but Vas isn't the same as recommended box size. Recommended relationships between Vas, Vb and other parameters are given he http://www.diysubwoofers.org/sld/sealed1.htm Zoebels are for people who don't get it. I'm one who doesn't "get it". Zoebel networks convert the driver terminal impedance to a resistance. That improves the crossover's rolloff characteristics. Zoebel's are simple, cheap, and work darn well. How do they relate to a system with an electronic crossover? The price/performance and time investment is hard to beat. Investing time, saves money. Again, Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. |
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#7
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Active Crossover Network
"Arny Krueger"
All you have to do is reduce distortion to the point where it is inaudible. Easy enough to do in the 21st century - without active crossovers. Still, you haven't give us one example of a low cost amplifier with no audible distortion. Staying within an $800 budget is not tough. Two, low cost, stereo amplifiers: $400 Passive electronic crossover: $ 20 Two Vifa woofers at $100 each: $200 Two Vifa TG 27 tweeters at $30 each: $ 60 Two old enclosures from a garage sale: $ 20 Total: $ 700 This isn't a system. Right, it isn't a system, it's the parts for a system. Add DIY and you have a system. IME, no. Either way, the best way is to optimize the driver & box combination using Thiel/small parameters and verify with actual measurements. Most manufacturers of quality woofers provide T/S parameters and leave the design up to the purchaser. Manufactures give a "VB ltrs" spec. Isn't that the recommended box volume? Here's a sample set of data for a Vifa woofer from the manufacturer's web site. http://www.d-s-t.com/vifa/data/tc08sd49-04d.htm Now maybe you can find Vb here, but I sure can't. I have data sheets for Vifa woofers, that Madisound sent out. Each data sheet *has* a recommended VB(Ltrs) for the woofer. One can go to Google and type: "speaker calculator". It will come up with Websites that offer free T/S box calculators. They are *very* easy to use. Just type in four T/S parameters, and the calculator will come up with the correct volume for the enclosure. I can find Vas, but Vas isn't the same as recommended box size. Recommended relationships between Vas, Vb and other parameters are given he http://www.diysubwoofers.org/sld/sealed1.htm Zoebels are for people who don't get it. I'm one who doesn't "get it". How do they relate to a system with an electronic crossover? Zoebels are not necessary for an electronic crossover system. (One of the *advantages* of electronic crossoves.) BTW *You didn't answer the question.* What do you have against Zoebels? BTW#2 Here's how to calculate the Zoebel, R and C values: Rz = 1.25 * R (the voice coil, dc resistance.) Cz (in uF) = 1000 * L (in mH)/(Rz*Rz) Example Calculation: (The L and R values are from the Vifa P13WH-00-08, 5' woofer) R dc voice coil = 5.7 and L voice coil inductance = 1 mH. Rz = 5.7 * 1.25 = 7.1 Ohms Cz = (1000 * 1) / (7.1 * 7.1)= 19.8 uF Again, Rolling your own loudspeakers and getting good results is far from simple unless you stick to subwoofers. Doing a two-way woofer/tweeter speaker system *right* is actually one of the tougher technical chores around. Again, I have to disagree with you. Yes, it is somewhat difficult to design a two-way speaker system: if you want to have a bass reflex enclosure, if you want to have a complex crossover (such as a 4th order, Linkwitz-Riley), if you want to add equalization networks (to make the response flat to 1 dB), if you want to have a resistive terminal impedance, and if you want to have good polar patterns at all frequencies. But, using a *closed box driver*, and using an *electronic crossover*, greatly simplifies the design. Simplifies it to the point where, a home builder can make a good two-way speaker, fairly easily. Bob Stanton |
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. I think best strategy would be to assemble a
Hybrid Mode
