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very high power crossover
Hi folks,
I would like to know how to construct a 2-way, 12-db passive crossover that is capable of handling up to 2000 watts, and does well at retaining the quality of sound at that level. Any advice or links would be greatly appreciated. thanks, Sean |
#2
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very high power crossover
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#3
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very high power crossover
I know a fellow who used to design output filters for 500,000 watt pulse
modulation AM transmitters. He wound his inductors from copper tubes with water pumped through for cooling. That might work... What a great concept, though probably over the edge for what I'm trying for. Seriously, this sounds like the perfect application for an active X-over prior to the power amps. The only problem I have with the active crossover configuration is the inevitable noise that gets introduced. I have gone to great effort to make my system purely digital, from the lossless WMA compressed music on my computer, to the Midiman Audiophile 2496 sound card, to the Midiman external D to A converter, to the pair of bridged Crown XS900 amplifiers (one for each channel). It would be a shame to introduce powered analog components for the sake of splitting the signal. I don't think most people have ever truly heard a pure digital setup and I'll tell you, it's phenomenal. So, I'm willing to accept some loss of power in order to keep the crossover passive, but my main concern is overdesigning the components to be able to ramp up into the 2000 watts range. To be specific: 1) Do the typical crossover calculations for determining component ratings apply at this level of power? 2) Is there a way to parallelize/serialize a bunch of smaller components together such that the power load can distributed, but they still combine in effort to perform the goal of splitting the signal? 3) If #2 is possible, then could someone please show me how to determine the power capacity of whatever frankenstein crossover I can mangle together? thanks again, Sean |
#4
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very high power crossover
Hi Sean,
The only problem I have with the active crossover configuration is the inevitable noise that gets introduced. I have gone to great effort to make my system purely digital... There are digital crossovers available; for example, Behringer makes them. If you are really interested in an all-digital system (preamp, crossovers, amps, speaker correction, room correction, surround), take a look at Tact Audio components (that's what I use). The active crossover would be a much better solution than "developing" your own passive crossover, and the digital crossover provides the flexibility that you will need to dial-in the correct slopes and crossover points. Regards, Tip "Sean" wrote in message news:RHUrc.13371$JC5.1256243@attbi_s54... I know a fellow who used to design output filters for 500,000 watt pulse modulation AM transmitters. He wound his inductors from copper tubes with water pumped through for cooling. That might work... What a great concept, though probably over the edge for what I'm trying for. Seriously, this sounds like the perfect application for an active X-over prior to the power amps. The only problem I have with the active crossover configuration is the inevitable noise that gets introduced. I have gone to great effort to make my system purely digital, from the lossless WMA compressed music on my computer, to the Midiman Audiophile 2496 sound card, to the Midiman external D to A converter, to the pair of bridged Crown XS900 amplifiers (one for each channel). It would be a shame to introduce powered analog components for the sake of splitting the signal. I don't think most people have ever truly heard a pure digital setup and I'll tell you, it's phenomenal. So, I'm willing to accept some loss of power in order to keep the crossover passive, but my main concern is overdesigning the components to be able to ramp up into the 2000 watts range. To be specific: 1) Do the typical crossover calculations for determining component ratings apply at this level of power? 2) Is there a way to parallelize/serialize a bunch of smaller components together such that the power load can distributed, but they still combine in effort to perform the goal of splitting the signal? 3) If #2 is possible, then could someone please show me how to determine the power capacity of whatever frankenstein crossover I can mangle together? thanks again, Sean |
#6
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very high power crossover
Sean,
I assume that you do not currently have a particular loudspeaker in mind for this application since most loudspeakers come with passive crossovers to begin with. Your loudspeaker and listening room parameters will have more to do with crossover power disipation than amplifier power output (i.e., if the loudspeaker driver fails first, it doesn't really how much power the crossover can dissipate). Sean wrote: 1) Do the typical crossover calculations for determining component ratings apply at this level of power? Yes - but at the associate current levels, crossover layout is very important to avoid current induced voltage effects. 2) Is there a way to parallelize/serialize a bunch of smaller components together such that the power load can distributed, but they still combine in effort to perform the goal of splitting the signal? Yes 3) If #2 is possible, then could someone please show me how to determine the power capacity of whatever frankenstein crossover I can mangle together? Resistors can be paralleled for increased power handling - i.e., 2 equal value 10-watt power resistor in parallel can handle 20-watts. Capacitors can be paralleled to increase power handling, but pay attention to capacitor maximum voltage rating (higher is better) and dissipation factor (lower is better). Inductors can be paralleled to increase power handling, but pay attention to DC resistance (lower is better) and saturation power levels (higher is better). Standard formulas for parallel connection resistors/capacitors/inductors apply when paralleling components. When paralleling non-equal component values, you will also need to pay attention to individual component power dissipation requirements to avoid stressing a sinlge component (e.g., a 1 Ohm and 10 Ohm resistor in parallel will have the power largely being dissipated in the smaller value resistor, defeating the purpose of paralleling components). As to what it will actually need to dissipate, that depends not only on the particular crossover design employed, but also on the load and the intended use, not the amplifier's output capability - Loudspeaker driver sensitivity? Higher sensitivity means less crossover stress Type of music will be played (rock, jazz, classical)? Higher peak to average level means less crossover stress Maximum desired sound pressure level at the listening position? Higher maximum level means more crossover stress Distance from loudspeaker to listening position? Closer means less crossover stress. Without having detailed driver specs and measurement tools, a do-it yourself passive crossover with off-the-shelf drivers may actually turn out significantly less than optimal. Truth be told, I can't tell from your posts what it is you are ultimately trying to achieve with this approach, nor can I figure out why you'd want to do this if you don't already know the answers to your original questions. Best regards, Terry thanks again, Sean |
#7
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very high power crossover
Hello Terry
I assume that you do not currently have a particular loudspeaker in mind for this application since most loudspeakers come with passive crossovers to begin with. I'm building a pair of dual-12 cabinets. The 12" Oz Audio Elite's each handle 500 Watts RMS so it is my intention to drive each cabinet with peaks of over 2000 watts, which I should be able to accomplish with a bridged Crown XS900. Your loudspeaker and listening room parameters will have more to do with crossover power disipation than amplifier power output (i.e., if These speakers will hopefully perform for a medium size dance floor, as well as outside. It's not for any DJ'ing purpose though, more for my own gluttony to have speakers that are just ridiculously powerful. All genre's of music must play satisfactorily though I find the techno genre to be the most challenging for the faithful reproduction of bass, and this is my goal, to have thunderous bass. 1) Do the typical crossover calculations for determining component ratings apply at this level of power? Yes - but at the associate current levels, crossover layout is very important to avoid current induced voltage effects. Noted Standard formulas for parallel connection resistors/capacitors/inductors apply when paralleling components. This is where my electrical theory is a little weak (I'm on a need to know basis). On your advice, I intend to use equal-value components in parallel but I'm not exactly sure how they would combine in effect. For example, if I have two 10-watt, 50-ohm resistors in parallel, is this the same as a single 20-watt 50-ohm resistor? Or does the resistance change for a parallel setup? How about for capacitance and inductance? As to what it will actually need to dissipate, that depends not only on the particular crossover design employed, but also on the load and the intended use, not the amplifier's output capability - I can see the speakers being driven at high loads with the subs taking a pounding. I wouldn't know where to guesstimate the average load that the crossover would bear. Is there a working ratio that makes sense? (e.g. design the crossover to handle 50% of amplifier's maximum output?) thanks for you help, Sean |
#8
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very high power crossover
Sean wrote:
This is where my electrical theory is a little weak (I'm on a need to know basis). On your advice, I intend to use equal-value components in parallel but I'm not exactly sure how they would combine in effect. For example, if I have two 10-watt, 50-ohm resistors in parallel, is this the same as a single 20-watt 50-ohm resistor? Or does the resistance change for a parallel setup? How about for capacitance and inductance? The resistance (R) changes in proportion to the number (n) of resistors used: R/n. For n=1, it's just the resistance of the one resistor (Req=R/1=R). Two 50 Ohm, 10 Watt resistors in parallel combine to form an equivalent 25 Ohm, 20 Watt resistor (Req=R/n=50/2). n equal value inductors (L) in parallel combine the same way as resistors (Leq=L/n). n equal value capacitors (C) in parallel combine as Ceq=n x C. For instance, three 10 microFarad capacitors combine to form an equivalent single capacitor of 30 microFarads (Ceq = 10 + 10 + 10 = 3 x 10 = 30). You can do a multil-term Goggle search on the terms: parallel resistor capacitor inductor formula to find the general equations for non-equal component values. I can see the speakers being driven at high loads with the subs taking a pounding. I wouldn't know where to guesstimate the average load that the crossover would bear. Is there a working ratio that makes sense? (e.g. design the crossover to handle 50% of amplifier's maximum output?) Depends on how you arrange the loudspeaker drivers (parallel, series, or independently driven) and what kind of crossover configuration you plan to use (LC, dual RL or RC, driver impedance correction, driver resonance correction, etc.). In general, those components in series with the drivers will see all of the current into the drivers, and those in parallel with the drivers will see all of the voltage into the drivers. For components in series with the driver (in general), the higher its resistance to the current flow, the greater the power dissipation in those components. For inductors and capacitors, this resistance should be low - say on the order of 0.2 to 0.5 Ohms worst case in the audio band (inductors in parallel also decrease the equivalent DCR, which is a good thing; similarly, parallel capacitors reduce the equivalent internal resistance). Put 20 Amps through 0.2 to 0.5 Ohms, that's equivalent to 80 to 200 Watts dissipation (i x i / r, double if you include a safety margin). For components parallel to the driver (again in general), it's the voltage across the component and its equivalent resistance that determines power dissipation (v x v / r). For the equivalent load presented by your drivers, you can calculate the worst case current and voltage that your amp can deliver. For example, for an amplifier with a 900 Watt, 8 Ohm rating, that's 85 Volts max voltage. Let's say the driver load is 4 Ohms, then the maximum current through the driver is 30 Amps. That's an equivalent peak output power of 3600 Watts and an average output power of 1800 Watts (assuing both the amp ad the wall outpet can deliver these levels). With bridged amplifiers, the voltage swing available doubles (85 becomes 170 Volts), but current is limited to what a single channel can deliver (probably still on the order of 30 Amps), and the output noise and distortion doubles. Best regards, Terry |
#9
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very high power crossover
"Tip" wrote in message ...
There are digital crossovers available; for example, Behringer makes them. If you are really interested in an all-digital system (preamp, crossovers, amps, speaker correction, room correction, surround), take a look at Tact Audio components (that's what I use). The Three things steer me away from this approach, 1) I would need two more amplifiers and of course the digital crossover ($$$) 2) I have little faith in today's standard of what 'digital' means. I have gone through a plethora of purportedly 'digital' devices, only to have them spew volumes of noise into my signal. No sir, it's been a precarious path to get where I am and I'm most reluctant to further add any form of electronic signal processing. 3) I cannot see the advantage of active digital over passive crossovers, assuming of course that I would never have reason to dynamically adjust the frequency separation characteristics, which I do not anticipate needing. You won't convince me that I cannot acceptably digitally equalize my original signal (in the computer before it even gets to the sound card) to compensate for any passive crossover, speaker, or acoustical aberrations. I sincerely appreciate the post though, thanks, Sean |
#10
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very high power crossover
Sean wrote:
I'm building a pair of dual-12 cabinets. The 12" Oz Audio Elite's each handle 500 Watts RMS so it is my intention to drive each cabinet with peaks of over 2000 watts, which I should be able to accomplish with a bridged Crown XS900. Are you familiar with Meridian products ? They make active speakers which have a digital input, then digital crossovers, and then separate DACs and amplifiers for each driver. http://www.meridian-audio.com/ If you read their white paper: http://www.meridian-audio.com/w_pape...eakers_prt.pdf (ok, it has a bit too much propaganda and too little information to be a true white paper): you might get some useful ideas for your project. In particular they explain their reasoning for having line-level crossovers and separate amplifiers for each driver. * With such a setup you wouldn't have any worry about power dissipation on the crossover. * Although I suspect their calculations in which they shown that you need much less total power with separate amplifiers don't really apply to RMS power, only to peak power. The white papers at harman might also be useful: http://www.harman.com/wp/index.jsp?articleId=122 Standard formulas for parallel connection resistors/capacitors/inductors apply when paralleling components. This is where my electrical theory is a little weak (I'm on a need to know basis). There are probably on the web introductory texts on electricity and electronics which explian the basics (see below). On your advice, I intend to use equal-value components in parallel but I'm not exactly sure how they would combine in effect. For example, if I have two 10-watt, 50-ohm resistors in parallel, is this the same as a single 20-watt 50-ohm resistor? No, it would be equivalent to a 20-watt 25-ohm resistor. But if you used four 10-watt, 50-ohm resistors in serie-parallel, you would get a 40-watt 50-ohm resistor. Or does the resistance change for a parallel setup? Yes. The resistance of two resistors in parallel obeys the equation: 1 / R = 1 / R1 + 1 / R2 In the case that both resistors are equal (R1 = R2) this gives: R = R1 / 2 In series the resistance is simply added, so: R = R1 + R2 How about for capacitance It is reversed: in parallel it sums, in series it divides. See for instance: http://www.tpub.com/neets/book2/3e.htm http://www.allaboutcircuits.com/vol_1/chpt_13/4.html and inductance? Same as resistance: http://www.aikenamps.com/AddingComponents.htm http://www.allaboutcircuits.com/vol_1/chpt_15/4.html -- http://www.mat.uc.pt/~rps/ ..pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC) Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94 |
#11
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very high power crossover
explain their reasoning for having line-level crossovers and separate
amplifiers for each driver. * With such a setup you wouldn't have any worry about power dissipation on the crossover. I understand why you suggest this route but you have to agree that any addition of powered components at any point along a signal's journey will invariably add noise. My ultimate goal is to minimize the number of these noise-generators. If the price for that is crossover dissipation, then I'll just have to drive more power. It is reversed: in parallel it sums, in series it divides. See for instance: http://www.tpub.com/neets/book2/3e.htm http://www.allaboutcircuits.com/vol_1/chpt_13/4.html and inductance? Same as resistance: http://www.aikenamps.com/AddingComponents.htm http://www.allaboutcircuits.com/vol_1/chpt_15/4.html Thanks for the links! Between you and Terry, I think I'm about ready to build the monster speakers of my dreams! thanks, Sean |
#12
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very high power crossover
In article mJ1tc.115688$536.21522461@attbi_s03,
Sean wrote: explain their reasoning for having line-level crossovers and separate amplifiers for each driver. * With such a setup you wouldn't have any worry about power dissipation on the crossover. I understand why you suggest this route but you have to agree that any addition of powered components at any point along a signal's journey will invariably add noise. In any sort of reasonable implementation the noise is irrelevant. The noise floor of my 3-way active cross-over with 13 op-amps the tweeter signal path is no higher than my solid state power amplifers' with the inputs shorted - completely inaudible a bit past a foot from the tweeter (listening position is 8' away). -- a href="http://www.poohsticks.org/drew/"Home Page/a Life is a terminal sexually transmitted disease. |
#13
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very high power crossover
Sent this a few days ago but never appeared.
"Sean" wrote in message news:O6arc.85510$536.14252301@attbi_s03... Hi folks, I would like to know how to construct a 2-way, 12-db passive crossover that is capable of handling up to 2000 watts, and does well at retaining the quality of sound at that level. Any advice or links would be greatly appreciated. I've designed crossovers for 1,000 W systems but, as Isaac says, much higher than that and you really should go active. With a 1,000 W crossover, the broad guidelines would be: Air-core coils only 400 -600 V polyprop caps Thick and wide tracks on the PCB Feet under the PCB to space it away from the cabinet Polyswitch HF unit protection Silicon sealant glue under the components (and tiewrapped) The critical problem is cooling the resistors. I used 50 W copper-clad types on heat sinks off the PCB, with plastic spacers under the heatsinks so that they did not touch the cabinet. It should not be too difficult to build a 2,000 W crossover on these principles. You can always double up on the caps, use 100 W resistors and hardwire the components. I'd be tempted to mount the heatsinks on the outside of the cabinets, too. Better go active, though. Stephen |
#14
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very high power crossover
Sean wrote:
explain their reasoning for having line-level crossovers and separate amplifiers for each driver. * With such a setup you wouldn't have any worry about power dissipation on the crossover. I understand why you suggest this route but you have to agree that any addition of powered components at any point along a signal's journey will invariably add noise. My ultimate goal is to minimize the number of these noise-generators. If the price for that is crossover dissipation, then I'll just have to drive more power. Sean I think you overestimate the audibility of the added noise. When just normal TL074 opamps with 15nV/Hz^-2 are taken a 4th order L-R highpass would have around 8uVrms noise, which is around 100dB below 1Vrms maximum level and less than the noise floor on a CD. The power amp will probably have almost 10 times that amount. :-( To use coils and caps in this power range will cost and weight a lot, especially for low xover frequencies. You also have to compensate the loudspeaker pole frequency if this approach should work. It is also quite difficult to design passive filters and requires a specialized software, where as simple active filters are a piece of cake. good luck -- ciao Ban Bordighera, Italy |
#15
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very high power crossover
Hi Sean,
There are digital crossovers available... Three things steer me away from this approach, 1) I would need two more amplifiers and of course the digital crossover ($$$) Yes, that is a hindrence! However, the two additional amps do not need to be nearly as powerful if used for the tweeters. And high-quality crossover components that can handle the high power you are talking about aren't particularly cheap either, although an order of magnitude cheaper than the amps. 2) I have little faith in today's standard of what 'digital' means. I have gone through a plethora of purportedly 'digital' devices, only to have them spew volumes of noise into my signal... In the Tact system, the digital output of the transport (PCM) goes directly to the digital preamp/crossover, which processes the data in the digital domain (24 bits) and outputs the data to the digital amps (PCM). The digital amps process the data in the digital domain, directly converting PCM to PWM without an analog conversion in between. The digtial signal is finally converted to analog by a filter just before the output terminals. The system is dead quiet. The volume is controlled by changing the output of the power supply in the power amps so that all 24 bits of data are always sent between the preamp and power amps. There is no distortion added to the signal by the digital processing, which cannot be said of analog domain processing. 3) I cannot see the advantage of active digital over passive crossovers, assuming of course that I would never have reason to dynamically adjust the frequency separation characteristics, which I do not anticipate needing. You won't convince me that I cannot acceptably digitally equalize my original signal (in the computer before it even gets to the sound card) to compensate for any passive crossover, speaker, or acoustical aberrations. That's because you are just learning about crossovers at this point. I don't want to discourage you from the educational experience of designing your own passive analog crossovers, but it is much simpler doing it in the digital domain where you don't have to deal with the negative side effects (e.g., phase shift). The ability to easily change the parameters of the crossover will be needed to fine-tune the crossover design. I doubt that you can compensate for side effects like phase shift using digital EQ in your computer, unless you have some kind of time-domain based digital EQ software. Changing the parameters of the passive crossover means buying more parts, and the parts probably have a tolerance of 10% which will make it harder to get the exact values you want. Good luck and keep us posted on your progress! Regards, Tip |
#16
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very high power crossover
Terry,
Thank you very much for your time and explanations, I really appreciate it. My speakers are going to be phenomenal. Sean |
#17
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very high power crossover
Sean,
de nada ... best of luck in your quest (but, along the way, I would recommend highly that you try to avoid permanent hearing damage Terry Sean wrote: Terry, Thank you very much for your time and explanations, I really appreciate it. My speakers are going to be phenomenal. Sean |
#18
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very high power crossover
I've designed crossovers for 1,000 W systems but, as Isaac says, much higher
than that and you really should go active. This is why I love the newsgroups With a 1,000 W crossover, the broad guidelines would be: Air-core coils only 400 -600 V polyprop caps Thick and wide tracks on the PCB Feet under the PCB to space it away from the cabinet Polyswitch HF unit protection Silicon sealant glue under the components (and tiewrapped) Excellent, thanks for sharing this. I have a couple related questions if you don't mind: 1) Was it a two-way or three-way? 2) Where were your frequency splits (1600 Hz?)? 3) Was it a 6 dB or 12dB rolloff (or more)? 4) How much power did you design into each frequency split? 5) What gauge wire did you use hardwire the components. I'd be tempted to mount the heatsinks on the outside of the cabinets, too. I think the execution of an exterior heatsink design would prove challenging. I'm more inclined to mount the heatsink interiorly but in the near vicinity of the port's airflow. Better go active, though. I have considered this many times, especially in light of multiple postings pushing me this direction, however, I still maintain that adding another noise-producing amplifier (even if the crossover is digital) to my setup will demote it (albeit, perhaps only psychologically) away from my 'dream' noiseless system that I have been pursuing forever. There was a post earlier that describes the noise floor as being irrelevant from eight feet away...well, my goal is to not hear a thing from less than a foot away. Why? For the same reason we do not all drive Honda's, because my system is better! Perfectionism is a crippling disease. |
#19
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very high power crossover
"Sean" wrote in message Excellent, thanks
for sharing this. I have a couple related questions if you don't mind: 1) Was it a two-way or three-way? Two-ways with 12s and 15s and 1 inch compression drivers, 3-way with 2-inch compression drivers and bullet HF. These were usually coupled to a sub-bass cabinet crossed over actively. 2) Where were your frequency splits (1600 Hz?)? Various - it depends on the compression driver and horn, but 1600 Hz is a good point to cross over from a 12 inch, although not every 1" compression driver is happy with that. I used the big RCF 1" (don't think they make it any more) and crossed it over at 1k5, which was fine. 3) Was it a 6 dB or 12dB rolloff (or more)? I've always favoured 24 dB Linkwitz-Reilly. You really need at least 18 dB to protect the HF unit. 4) How much power did you design into each frequency split? At 1500 to 2000 Hz crossover frequency you should reckon that the HF will take about 20 - 25 percent of the total power. 5) What gauge wire did you use I used 1.5 mm for the LF and .8 mm for the HF. hardwire the components. I'd be tempted to mount the heatsinks on the outside of the cabinets, too. I think the execution of an exterior heatsink design would prove challenging. I'm more inclined to mount the heatsink interiorly but in the near vicinity of the port's airflow. You should be OK with that. Just don't skimp on the heatsinks. Stephen |
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