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#1
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4 speakers from a power amp instead of 2 (question)
Hello,
Is there a common technique for hooking up more than the standard two speakers to a power amp? If you had a powerful amp, you could run four speakers. But I'm not sure if you use a simple Y cable, or if you need a signal conditioning device of some sort to do it properly. It makes me wonder how a live concert can take a stereo feed off of a mixing console, and then send it to multiple power amps and multiple speakers. There must be some sort of standard process to make the signals rout properly without drop-off and hiss. |
#2
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4 speakers from a power amp instead of 2 (question)
You can connect as many speakers as you like to an amplifier output. You
simply have to be sure that the combined impedance is not lower than what the amplifier is rated to drive. |
#3
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4 speakers from a power amp instead of 2 (question)
"genericaudioperson" wrote from Gooooooooooogle Groups ...
Is there a common technique for hooking up more than the standard two speakers to a power amp? Is two speakers "the standard"? The standard for what, exactly? Can you run more than (x) speakers from a power amp? Yes, you can run as many as the amplifier will safely drive. Is there a "common technique" for connecting multiple speakers? No. It depends on exactly what the specific amplifier and speakers are. If you had a powerful amp, you could run four speakers. If you had a powerful (enough) amp you could run 500 speakers (or substitue whatever number you wish.) But I'm not sure if you use a simple Y cable, No, it is not done with cable adapters. It is more sophisticated than that. If you have a specific configuration in mind, you could explicitly reveal what it is. Otherwise you are asking a hypothetical question for which there are thousands of possiible answers, most of them likely meaningless or even confusing to you. or if you need a signal conditioning device of some sort to do it properly. Signal conditioning devices have nothing to do with driving multiple speakers from an amplifier(s). It makes me wonder how a live concert can take a stereo feed off of a mixing console, and then send it to multiple power amps and multiple speakers. There must be some sort of standard process to make the signals rout properly There is usually more (and sometimes less) than "a stereo feed". Larger venues typically don't bother with "stereo" because most of the audience would hear only one side and miss the other. The outputs from the mixing console are sometimes just fed in parallel to multiple amplifiers (which have high-impedance, "bridging" inputs). Or sometimes using distribution amplifers and/or frequency crossovers, etc. And in larger venues, using equipment which compensates for time alignment betweeen multiple sets of speakers, etc. etc. without drop-off and hiss. Dunno what you mean by "drop-off"? As for hiss, typical professional equipment has enough dynamic range to run signals well above the levels where you would hear hiss. Besides, even with no audience in them, large venues have enough residual noise to mask most hiss unless you have you ear within a few inches of the speaker. (and you wouldn't want it there for long when they send any kind of signal through it.) |
#4
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4 speakers from a power amp instead of 2 (question)
On Sat, 29 Nov 2008 15:18:15 -0800, "Richard Crowley"
wrote: his usual screed of contempt to an inexpert question Richard, are you the Grinch? |
#5
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4 speakers from a power amp instead of 2 (question)
"Laurence Payne" wrote...
"Richard Crowley" wrote: his usual screed of contempt to an inexpert question Richard, are you the Grinch? Perhaps we should set up news:alt.flame.richard for you so the rest of us can discuss audio topics here. |
#6
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4 speakers from a power amp instead of 2 (question)
This is interesting. So when you add speakers, the impedance drops.
And then you have to do some sort of math to figure it out. It's intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). It must be a splitter cable. If the amp only has two outputs, and you are trying to run 4 enclosures, then you need to mult the signal with a Y-cable or something like that. That sounds like something that is not on the cable wall at Guitar Center, which means I don't know how to use it :-). Maybe it's behind the counter in the voodoo area. |
#7
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4 speakers from a power amp instead of 2 (question)
On Sat, 29 Nov 2008 17:09:24 -0800 (PST), genericaudioperson
wrote: This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. Impedances add up the same way as resistances; parallel two impedances, and the result is the product over the sum, just like resistors. But maybe a better way for you to think about the issue is to think in terms of current. Each speaker cabinet will need to draw some current from the amplifier. The current drawn by both cabinets is a simple sum, just like you'd expect. It's interesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). It's actually a large amount of current that you're needing to avoid, because the amplifier will balk at trying to supply it. The reason that there isn't a simple, single answer to your question isn't that it's complicated or that you're not smart enough to understand it - it's that the numbers aren't available. Speakers are a complicated load and amplifiers are a complicated source. There are rules of thumb and sometimes actual experience of a particular setup, but God dwells in the details, and she's not telling, often as not. All the best fortune, Chris Hornbeck |
#8
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4 speakers from a power amp instead of 2 (question)
genericaudioperson wrote:
This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. It's intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). It is interesting and a source of confusion because a lower impedance presents a larger load. So, an amplifier "spec" that reads "minimum load: 4 ohms" is somewhat ambiguous! It must be a splitter cable. If the amp only has two outputs, and you are trying to run 4 enclosures, then you need to mult the signal with a Y-cable or something like that. That sounds like something that is not on the cable wall at Guitar Center, which means I don't know how to use it :-). Maybe it's behind the counter in the voodoo area. There are many ways to go about distributing amplifier outputs to speakers. One is, as you say, a slitter ( "wye" or, more commonly 'Y') cable. This implies the use of 1/4" phone jacks which, although popular, are poorly suited for amplifer to speaker applications. A step up is banana plugs (http://en.wikipedia.org/wiki/Banana_plug) and and binding posts (http://en.wikipedia.org/wiki/5_way_binding_post). Some banana plugs are stackable and make connecting multiple speakers in parallel as simple as plugging one connector into the back of others. Pro sound systems often use custom built rack panels with connectors that allow convenient and versatile patching and connecting speakers to the amplifiers mounted in the rack(s). The Speakon connector (http://en.wikipedia.org/wiki/Speakon) is superior in many ways and is popular with the pros. -- ================================================== ====================== Michael Kesti | "And like, one and one don't make | two, one and one make one." mrkesti at hotmail dot com | - The Who, Bargain |
#9
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4 speakers from a power amp instead of 2 (question)
On Nov 29, 10:50*pm, "Michael R. Kesti"
wrote: genericaudioperson wrote: This is interesting. *So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. *It's intersesting that there is a low amount of impedance you are trying to avoid. *Usually "overload" means a large number (for us mortals who don't know what we're doing). It is interesting and a source of confusion because a lower impedance presents a larger load. *So, an amplifier "spec" that reads "minimum load: 4 ohms" is somewhat ambiguous! It must be a splitter cable. *If the amp only has two outputs, and you are trying to run 4 enclosures, then you need to mult the signal with a Y-cable or something like that. *That sounds like something that is not on the cable wall at Guitar Center, which means I don't know how to use it :-). *Maybe it's behind the counter in the voodoo area. There are many ways to go about distributing amplifier outputs to speakers. One is, as you say, a slitter ( "wye" or, more commonly 'Y') cable. *This implies the use of 1/4" phone jacks which, although popular, are poorly suited for amplifer to speaker applications. A step up is banana plugs (http://en.wikipedia.org/wiki/Banana_plug) and and binding posts (http://en.wikipedia.org/wiki/5_way_binding_post). Some banana plugs are stackable and make connecting multiple speakers in parallel as simple as plugging one connector into the back of others. Pro sound systems often use custom built rack panels with connectors that allow convenient and versatile patching and connecting speakers to the amplifiers mounted in the rack(s). *The Speakon connector (http://en.wikipedia.org/wiki/Speakon) is superior in many ways and is popular with the pros. so the op's questions is still valid.. the standard methods I know of connect the speakers in paralel... but if you have too many speakers ___what is the industry standard way of dealing with this? I know you may want to use a series parallel connection but I have never seen a breakout box or other standard device that you can buy at GC for connecting a group of speakers in a series parallel arrangment, is there a way or is that just not done? the other alternative is to use multiple amplifers which I suppose is the standard solution.. Mark |
#10
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4 speakers from a power amp instead of 2 (question)
genericaudioperson wrote:
This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. This is basic electricity, something that anyone going beyond a plug-and-play system should understand. intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). The lower the impedance, the closer you get to a short circuit. Does that help you to understand what's going on here? It must be a splitter cable. If the amp only has two outputs, and you are trying to run 4 enclosures, then you need to mult the signal with a Y-cable or something like that. The reason why it's not a common off-the-shelf item is because hooking up multiple plug-and-play speakers isn't something that's done very often - simply because it's often not a good idea to do that. If you exceed the power rating of the amplifier, usually you'll know it before you do any damage because you'll hear distortion at a lower volume than you expect. But if you keep operating it that way, you WILL damage the amplifier, the speakers, or both. You MUST know what you're doing in this business if you want to keep your equipment working. Some speakers are built with two connectors, making it easy to connect a second speaker in the chain, but the people who make the speakers don't know what amplifier you're connecting them to, so just because you CAN hook them up doesn't guarantee that they'll work. You should also understand what you're asking when you ask a "will this work?" question on a forum. In order to give a reasonably good answer, someone must know the characteristics of the amplifier and speakers that you're planning to use. Just posting model numbers means that we need to research the equipment, do some calculations, and make a (not guaranteed) recommendation. That's a system engineering job, and people make good money doing that work. So do your homework before you jump in. Chances are you can figure things out yourself. You'll get more cooperation and more complete information if you start with all the details you can pull together. -- If you e-mail me and it bounces, use your secret decoder ring and reach me he double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers ) |
#11
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4 speakers from a power amp instead of 2 (question)
Mark wrote:
but if you have too many speakers ___what is the industry standard way of dealing with this? I know you may want to use a series parallel connection but I have never seen a breakout box or other standard device that you can buy at GC for connecting a group of speakers in a series parallel arrangment, is there a way or is that just not done? The "industry standard" way of dealing with a large number of speakers, for instance the speakers installed in the ceiling of a factory or department store, is to use what's known as a constant voltage distribution system. You'll occasionally see references to a 70.7 volt output on an amplifier. The way this works is that each speaker has a transformer with it that determines how much POWER that speaker get. It works like your house wiring. You can plug in a lamp, a computer, a toaster, as many things as you want, until you blow the fuse, and everything gets the same power and enough current to do the work. As far as an off-the-shelf series/parallel breakout, nope. There are too many possible combinations of speakers and desired impedance load to the amplifier that a store couldn't possibly stock all of them. These arrangements are all custom-wired, and often the speakers are chosen as part of the design. -- If you e-mail me and it bounces, use your secret decoder ring and reach me he double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers ) |
#12
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4 speakers from a power amp instead of 2 (question)
"Mark" wrote from Gooooooooooogle Groups...
so the op's questions is still valid.. the standard methods I know of connect the speakers in paralel... but if you have too many speakers ___what is the industry standard way of dealing with this? 1. Constant-voltage system ("70-volt" et.al.) 2. Series-parallel connections (to maintain total impedance) 3. Multiple amplifiers. 4. likely others also I know you may want to use a series parallel connection but I have never seen a breakout box or other standard device that you can buy at GC for connecting a group of speakers in a series parallel arrangment, is there a way or is that just not done? There is a great deal more to sound reinforcment systems than what is available at your local guitar shop. We don't even know whether the OP is asking about portable or installed systems? I once maintained an amphitheatre in a med school where they had special transducers at each seat for the students' stethoscopes. The lecturer had recordings of normal and abnormal heart (and other) sounds which he used to familiarize the future physicians with what "normal" is supposed to sound like, etc. These 350 transducers were such high impedance that even when all connected in parallel, they represented 20 ohms combined impedance. I also designed and installed a seat-back system in a church which uses 3x5 speakers on 18-inch spacing, essentially one speaker per person, to avoid hanging a big bin from the ceiling to cover the (octagonal) seating area. The system is used exclusively for speech reinforcement as all the music is acoustic (starting with the tracker pipe organ and concert grand piano). Photo at http://www.rcrowley.com/Rieger/SSDAReiger2.htm You can barely see the continuous grille at the top of the pew-back . I should post some closer photos of the detail. The speakers in each row are all wired in series, and the rows are wired in parallel. I recruited the choir members to help install all the speakers, and trained 4-5 of them how to solder properly. It worked out quite well. Only one screwdriver through a cone, and very few cold solder joints upon final inspection (by me). The speakers are divided into 4 sections, each driven by an amplifier channel in order to implement time-delay correction. The total impedance turned out to be something between 8 and 16 for each section, so they were easily driven by conventional amplifiers. The 550-seat auditorium is easily driven (for speech reinforcement) by ~300W total amplifier power which idles along at a fraction of that power. The new auditorium just celebrated its 25-year anniversary and the system still works quite well. The potential gain before feedback is amazing. :-) |
#13
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4 speakers from a power amp instead of 2 (question)
Mike Rivers wrote:
genericaudioperson wrote: This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. This is basic electricity, something that anyone going beyond a plug-and-play system should understand. intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). The lower the impedance, the closer you get to a short circuit. Does that help you to understand what's going on here? alternate explanation The lower the impedance, the more current. The more current into a constant load, the more heat*. The more heat, the higher the probability of failure.... *it's called IR heating - current and resistance.... snip -- Les Cargill |
#14
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4 speakers from a power amp instead of 2 (question)
On Nov 30, 9:30*am, "Richard Crowley" wrote:
"Mark" *wrote from Gooooooooooogle Groups... so the op's questions is still valid.. the standard methods I know of connect the speakers in paralel... but if you have too many speakers ___what is the industry standard way of dealing with this? 1. Constant-voltage system ("70-volt" et.al.) 2. Series-parallel connections (to maintain total impedance) 3. Multiple amplifiers. 4. likely others also OK I know about 70 volt system for that kind of lower power PA... I was thinking (and I should have said) in a PA FOH application where there are a large number of speakers in an array at the FOH. How do most people manage this.... with custom cables to create a series parallel connection to the amp or just use a large number of amps as well or what? In other words, when I go to a venue and see maybe 24 speakers at FOH and a rack of maybe 6 amps, I would guess there are 2 speakers in parallel per side 6x4 = 24... but usually it doesn't work out that simple, sometimes i see maybe 10 speakers on each side up on cranes, are these wired together somehow or how is it done? Mark |
#15
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4 speakers from a power amp instead of 2 (question)
"Mark" wrote...
OK I know about 70 volt system for that kind of lower power PA... I was thinking (and I should have said) in a PA FOH application where there are a large number of speakers in an array at the FOH. How do most people manage this.... with custom cables to create a series parallel connection to the amp or just use a large number of amps as well or what? In other words, when I go to a venue and see maybe 24 speakers at FOH and a rack of maybe 6 amps, I would guess there are 2 speakers in parallel per side 6x4 = 24... but usually it doesn't work out that simple, sometimes i see maybe 10 speakers on each side up on cranes, are these wired together somehow or how is it done? Typically, there is a large rack of amplifiers that go with each of those speaker stacks. In the rack along with the amplifiers is likely also some sort of active or passive (line-level) signal distribution and/or electronic (line-level) crossovers which route lows, mids, highs, etc. to separate amplifier and speaker sections. |
#16
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4 speakers from a power amp instead of 2 (question)
Typically, there is a large rack of amplifiers that go with each of those speaker stacks. In the rack along with the amplifiers is likely also some sort of active or passive (line-level) signal distribution and/or electronic (line-level) crossovers which route lows, mids, highs, etc. to separate amplifier and speaker sections. ok so far so good... then only two or maybe three speakers are connected togther in parallel to each amp output using standard speakon cables etc? Mark |
#17
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4 speakers from a power amp instead of 2 (question)
"Mark" wrote ...
Richard wrote... Typically, there is a large rack of amplifiers that go with each of those speaker stacks. In the rack along with the amplifiers is likely also some sort of active or passive (line-level) signal distribution and/or electronic (line-level) crossovers which route lows, mids, highs, etc. to separate amplifier and speaker sections. ok so far so good... then only two or maybe three speakers are connected togther in parallel to each amp output Yes one or two cabinets connected to each amplifier output channel, etc. This is done as much for redundancy (failure survival) as for other reasons. using standard speakon cables etc? For big racks of amplifiers and big stacks of speaker cabinets, they more likely use pre-assembled cable harnesses which use larger multi- pin connectors rather than one-at-a-time Speakons, etc. Not only are multi-pin connectors faster to deploy (and strike), but they also reduce accidental mis-connection. Any kind of (pre-engineered) series/ parallel speaker wiring is likely built into the (custom) cable harnesses. |
#18
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4 speakers from a power amp instead of 2 (question)
"genericaudioperson" wrote
in message Hello, Is there a common technique for hooking up more than the standard two speakers to a power amp? If you had a powerful amp, you could run four speakers. But I'm not sure if you use a simple Y cable, or if you need a signal conditioning device of some sort to do it properly. If you have 4 identical speakers, you can hook them up in series-parallel, and they will load the amp like just one speaker, but have 4 times the power handling capacity. |
#19
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4 speakers from a power amp instead of 2 (question)
genericaudioperson wrote:
Is there a common technique for hooking up more than the standard two speakers to a power amp? If you had a powerful amp, you could run four speakers. But I'm not sure if you use a simple Y cable, or if you need a signal conditioning device of some sort to do it properly. This is discussed in the Yamaha Sound Reinforcement Handbook. You can run as many parallel speakers off of an amp as you want, so long as the total impedance the amplifier sees is higher than it's minimum rated load impedance. So if the amp says "4 ohm load or higher" you can put two 8 ohm speakers per channel, but not three. It makes me wonder how a live concert can take a stereo feed off of a mixing console, and then send it to multiple power amps and multiple speakers. There must be some sort of standard process to make the signals rout properly without drop-off and hiss. In the case of the line level signals it's much easier, since the output impedance is very low and the input impedance is very high. You can Y with impunity for the most part. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#20
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4 speakers from a power amp instead of 2 (question)
genericaudioperson wrote:
This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. It's intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). Go right now and buy the Yamaha Sound Reinforcement Handbook. It will answer most of these elementary electrical questions. There is also a discussion of amp loading in the FAQ for this group. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#21
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4 speakers from a power amp instead of 2 (question)
Mark wrote:
OK I know about 70 volt system for that kind of lower power PA... I once ran a 5KW 70 volt system. And it used to be very common for 70V systems to be used in theatres to deal with the long runs between the amps in the projection booth and the speakers behind the screen. I was thinking (and I should have said) in a PA FOH application where there are a large number of speakers in an array at the FOH. In most of those applications, the speakers are being individually processed....each driver has an amplifier connected to it and a DSP module devoted to that amplifier. All the DSP modules are fed from the console and there is usually some sort of workstation that allows the operator to adjust DSP parameters. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#22
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4 speakers from a power amp instead of 2 (question)
Arny Krueger wrote:
"genericaudioperson" wrote in message Hello, Is there a common technique for hooking up more than the standard two speakers to a power amp? If you had a powerful amp, you could run four speakers. But I'm not sure if you use a simple Y cable, or if you need a signal conditioning device of some sort to do it properly. If you have 4 identical speakers, you can hook them up in series-parallel, and they will load the amp like just one speaker, but have 4 times the power handling capacity. And twice the distortion and some amount approaching twice the frequency response abnormalities. Remember when you do this, each driver is in series with a nonlinear load. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#23
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4 speakers from a power amp instead of 2 (question)
"Scott Dorsey" wrote in message
Arny Krueger wrote: "genericaudioperson" wrote in message Hello, Is there a common technique for hooking up more than the standard two speakers to a power amp? If you had a powerful amp, you could run four speakers. But I'm not sure if you use a simple Y cable, or if you need a signal conditioning device of some sort to do it properly. If you have 4 identical speakers, you can hook them up in series-parallel, and they will load the amp like just one speaker, but have 4 times the power handling capacity. And twice the distortion and some amount approaching twice the frequency response abnormalities. Not at all. In theory and in practice, the effective source impedance for either speaker calculates and measures out to be about half the output impedance of the source. Remember when you do this, each driver is in series with a nonlinear load. But, its the identical same nonlinear load. That's one reason why I specified "4 identical speakers". If they are signficantly different, then many of the bad things you suggest may happen. |
#24
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4 speakers from a power amp instead of 2 (question)
genericaudioperson wrote:
This is interesting. So when you add speakers, the impedance drops. And then you have to do some sort of math to figure it out. It's intersesting that there is a low amount of impedance you are trying to avoid. Usually "overload" means a large number (for us mortals who don't know what we're doing). It must be a splitter cable. If the amp only has two outputs, and you are trying to run 4 enclosures, then you need to mult the signal with a Y-cable or something like that. That sounds like something that is not on the cable wall at Guitar Center, which means I don't know how to use it :-). Maybe it's behind the counter in the voodoo area. If you run a splitter cable, basically, the impedance becomes half. That is only practical if the amp is able to handle the increased current required by the lowered impedance. That is, roughly, double the current. Some amps will handle that happily, but many will not. If I didn't know for certain that the amp was safe with the lower impedance, I wouldn't try to operate it with the four speakers. There are many other variables involved and much of the discussion here has involved them, but this is the general situation. -Raf -- Misifus- Rafael Seibert Photos: http://www.flickr.com/photos/rafiii home: http://www.rafandsioux.com |
#25
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4 speakers from a power amp instead of 2 (question)
Not at all. In theory and in practice, the effective source impedance for either *speaker calculates and measures out to be about *half the output impedance of the source. Really? I could see this might be true if the speaker coils were like the windings of a center tapped transformner, but I don't think they are, they are not magnetically or acousticaly closely coupled to each other and the winding resistance is high compared to the self coupling of each coil... I don't think the source Z that each speaker sees could be any lower than the source Z of the amp output ...and is probably higher... For the sake of discussion, lets assume the source Z of the amp is 0 Ohms. I think each speaker sees a source Z just equal to it's own source Z for 2 speakers in series. Or for 4 speakers in series parallel, each speaker sees a source Z equal to 1/3 of its own? (assumming identical speakers) But yes each speaker sees exactly 1/2 the VOLTAGE at the amp output.. this IS an interestig question... Mark |
#26
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4 speakers from a power amp instead of 2 (question)
On Mon, 1 Dec 2008 20:03:19 -0800 (PST), Mark
wrote: But yes each speaker sees exactly 1/2 the VOLTAGE at the amp output.. "Exactly" is the key to the puzzle... Much thanks, as always, Chris Hornbeck |
#27
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4 speakers from a power amp instead of 2 (question)
"Mark" wrote in message
Not at all. In theory and in practice, the effective source impedance for either speaker calculates and measures out to be about half the output impedance of the source. Really? I could see this might be true if the speaker coils were like the windings of a center tapped transformer, but I don't think they are, they are not magnetically or acoustically closely coupled to each other and the winding resistance is high compared to the self coupling of each coil... It's not necessary that they be coupled. Just do the math with resistors. I don't think the source Z that each speaker sees could be any lower than the source Z of the amp output ...and is probably higher... Just do tht math. For the sake of discussion, lets assume the source Z of the amp is 0 Ohms. I think each speaker sees a source Z just equal to it's own source Z for 2 speakers in series. Or for 4 speakers in series parallel, each speaker sees a source Z equal to 1/3 of its own? (assumming identical speakers) You are just waving your hands, and using a weird example of an amp with zero output impedance. But yes each speaker sees exactly 1/2 the VOLTAGE at the amp output.. Follow that thought. this IS an interestig question... Seemed intuitively clear to me. An amplifier driving two identical speakers in series, is like two amps in series, each putting out half the voltage with half the source impedance, both in series driving the same 2 speakers in series. Now, rearrange things so that one speaker and one amp are connected together in each of two independent systems. It's all the same. |
#28
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4 speakers from a power amp instead of 2 (question)
For the sake of discussion, lets assume the source Z of the amp is 0 Ohms. *I think each speaker sees a source Z just equal to it's own source Z for 2 speakers in series. Or for 4 speakers in series parallel, each speaker sees a source Z equal to 1/3 of its own? (assumming identical speakers) You are just waving your hands, and using a weird example of an amp with zero output impedance. It's not necessary that they be coupled. Just do the math with resistors. OK lets do the math... for a simple case of resistors... assume two identical speakers in series, each speaker = 8 Ohms. and assume the speakers behave as resistors and assume the amp output Z = 1 Ohm assume all Z's are simply R In this most simple case the math says each speaker sees a source Z of the other speaker in series with the amp 8+1 = 9 Ohms... I think your point was each speaker would see 1/2 Ohm, I don't see that? Yes, I see each speaker sees 1/2 the voltage, that is obvious and will always be true even if the speaker Z varies as a function of frequency or even if it is non-linear woth amplitude, as long as the two speakers are identical. But I don't see the effective source Z being 1/2. Mark |
#29
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4 speakers from a power amp instead of 2 (question)
On Tue, 2 Dec 2008 06:45:26 -0800 (PST), Mark
wrote: OK lets do the math... for a simple case of resistors... assume two identical speakers in series, each speaker = 8 Ohms. and assume the speakers behave as resistors and assume the amp output Z = 1 Ohm assume all Z's are simply R In this most simple case the math says each speaker sees a source Z of the other speaker in series with the amp 8+1 = 9 Ohms... I think your point was each speaker would see 1/2 Ohm, I don't see that? Yes, I see each speaker sees 1/2 the voltage, that is obvious and will always be true even if the speaker Z varies as a function of frequency or even if it is non-linear woth amplitude, as long as the two speakers are identical. But I don't see the effective source Z being 1/2. Whoa!, when did we change from four speakers per channel to two? Somewhere upstream, fersure. For four identical speakers in series-parallel, the load to the amplifier is the same as that of one of the speakers, and each speaker gets 1/2 the voltage and 1/2 the current from the amplifier, so sees the same source impedance as a single speaker. Somewhere the discussion slipped from four speakers to two, leading to this confusion. Much thanks, as always, Chris Hornbeck |
#30
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4 speakers from a power amp instead of 2 (question)
On Dec 3, 12:21*am, Chris Hornbeck
wrote: On Tue, 2 Dec 2008 06:45:26 -0800 (PST), Mark wrote: OK lets do the math... for a simple case of resistors... assume two identical speakers in series, each speaker = 8 Ohms. and assume the speakers behave as resistors and assume the amp output Z * = 1 Ohm assume all Z's are simply R In this most simple case the math says each speaker sees a source Z of the other speaker in series with the amp 8+1 = 9 Ohms... I think your point was each speaker would see 1/2 Ohm, I don't see that? Yes, I see each speaker sees 1/2 the voltage, that is obvious and will always be true even if the speaker Z varies as a function of frequency or even if it is non-linear woth amplitude, *as long as the two speakers are identical. But I don't see the effective source Z being 1/2. Whoa!, when did we change from four speakers per channel to two? Somewhere upstream, fersure. For four identical speakers in series-parallel, the load to the amplifier is the same as that of one of the speakers, and each speaker gets 1/2 the voltage and 1/2 the current from the amplifier, so sees the same source impedance as a single speaker. Somewhere the discussion slipped from four speakers to two, leading to this confusion. Much thanks, as always, Chris Hornbeck- Hide quoted text - Chris, the question is not about what load the AMP sees, you are correct what you said about what load the amp sees but that is not in question, the question I am discussing is not what load that the amp sees but rather what does each speaker see as a source Z driving it...this is what determines the damping factor for the speaker.. in the case of one speaker, the speaker obvisously sees the output Z of the amp. The question at hand is what does each speaker see as a driving Z when two speakers are connected in series.. and it is not a simple question as it first appears..... Arny, I think you are right..for the special case of two identical speakers, the back EMF generated by each speaker is identical so you cannot use the simple method of treating the speakers as seperate independent loads. These are DEPENDENT sources. If you use the simple method of indepenedent sources, you get the simple wrong answer of 8+1 = 9 Ohms for the example case above. But I now think this is wrong and you are right. To calculate the right answer you have to consider that the two EMFs are not independent but identical so the back EMFs are identical and you cannot analyze this in the simple way like resistors but rather have to consider that you have DEPENDENT EMF sources. Using symmetry as you suggested, I agree you are correct, each speaker sees a source Z of 1/2 the amp source Z or 1/2 Ohm in this example, a big difference! Note this is true only for the special case of INDENTICAL speakers so that the back EMF is identical and you have DEPENDENT sources. If you connect two different speakers in series then they are no longer exactly DEPENDENT sources and the problem gets much more complicated. My orignal answer of 9 Ohms is correct for totally independent sources like resistors. thanks for the interesting discussion Mark |
#31
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4 speakers from a power amp instead of 2 (question)
This long and currently pointless (or at least meandering) thread began when
someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts of time answering questions that are covered in library books. There has got to be a better way to direct people to the information they need. I rarely ask broad questions, limiting myself to something specific that I couldn't readily find the answer for. I consider it my own responsibility to educate myself, and not to abuse other peoples' generosity. |
#32
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4 speakers from a power amp instead of 2 (question)
William Sommerwerck wrote:
This long and currently pointless (or at least meandering) thread began when someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts of time answering questions that are covered in library books. There has got to be a better way to direct people to the information they need. That IS what the FAQ is for, isn't it? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#33
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4 speakers from a power amp instead of 2 (question)
On Dec 3, 9:31*am, "William Sommerwerck"
wrote: This long and currently pointless (or at least meandering) thread began when someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts of time answering questions that are covered in library books. There has got to be a better way to direct people to the information they need. I rarely ask broad questions, limiting myself to something specific that I couldn't readily find the answer for. I consider it my own responsibility to educate myself, and not to abuse other peoples' generosity. yes the original question from the OP was basic... the secondary question re the impact series/parallel connection has on speaker damping factor is not basic and is not covered in any book I have seen... if you find this long and pointless, please feel free to not participate... thanks Mark |
#34
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4 speakers from a power amp instead of 2 (question)
In article , Mark wrote:
On Dec 3, 9:31=A0am, "William Sommerwerck" wrote: This long and currently pointless (or at least meandering) thread began w= hen someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts = of time answering questions that are covered in library books. There has got= to be a better way to direct people to the information they need. I rarely ask broad questions, limiting myself to something specific that = I couldn't readily find the answer for. I consider it my own responsibility= to educate myself, and not to abuse other peoples' generosity. yes the original question from the OP was basic... the secondary question re the impact series/parallel connection has on speaker damping factor is not basic and is not covered in any book I have seen... if you find this long and pointless, please feel free to not participate... This is long, as I may quote....sorry...I'm leaving part 2 out. Damping: Loudspeakers In Series Dick Pierce Professional Audio Development 1 INTRODUCTION An entire mythology surrounds the notion of damping in loudspeakers. We have separately treated the oft-cited and nearly useless "damping factor" specification in a separate article. Here, we discuss much of the myth surrounding the behavior of loudspeakers connected in series and the seemingly intuitive effect on damping tat results. Of late, this topic is relevant or several reasons. First, we have seen a gain in use of multiple-woofer systems, exemplified by the popular, so-called "D'Appolito" configuration (often the woofers are connected in parallel, but there are applications where a series connection could be appropriate as well). Second, we have observed an unfortunate trend in consumer electronics, especially in home theater receivers. More and more, these receivers have skimped on power supply and/or output stage design and are quite unable to drive the lower impedances oft found in today's speakers. The question often arises whether speakers can be hooked in series, thus raising the impedance. The answer often given to both of these scenarios is "Oh, no, you can't do that. The damping of each speaker will be severely reduced because of the series impedance of the other speaker! As you might have guessed, we're going to show why this is wrong. We'll do this by taking an analytical approach, and test our analysis by actually measuring actual systems. 2 WHAT IS DAMPING? The term "damping" is has a very specific and unambiguous definition: technically, it is a measure of how quickly energy is removed from a resonant system. This definition stands despite attempt to co-opt the term for otherwise imprecise and often incorrect uses(1). It is a measure of how quickly a resonant or oscillatory system is brought under control by removing energy that would otherwise keep the resonance going. Energy is stored in reactive elements. These include masses and compliances (or springs) in the mechanical world, and inductances and capacitances in the electrical world. Mechanically, energy of a mass is the kinetic energy due to the motion of a mass. The kinetic energy of a moving mass equal to the mass times the velocity squared. In a spring or compliance, the energy is stored as potential energy in the compression or extension. The potential energy is equal to the spring constant times the compression or extension squared). Electrically, kinetic energy is in the magnetic field around an inductor created by the current flowing through the inductor. The energy is equal to the inductance times the current squared. In a capacitor, it's the potential energy in the electric field caused by the impressed voltage on the plates of a capacitor, equal to the capacitance times the voltage squared. Energy is removed through loss mechanism, such as frictional losses in the mechanical domain or ohmic losses in the electrical. These losses convert energy to heat, and once that happens, the energy is no longer available. In loudspeakers, there is a direct measure of the ratio of energy stored to energy lost, and that is the so-called "Q" factor. And we find that in most loudspeakers, there are two predominant loss mechanisms, each with there own Q measurement. The due to mechanical losses is designated as Qm, while that for electrical losses is designated as Qe(2). We can calculate these factors knowing the energy storage and losses mechanisms involved The mechanical Qm results from the energy storage in the moving mass of the cone and the frictional losses in the suspension. It is calculated thus: Mm Qm = 2 pi F ---- Rm where is the F resonant frequency of the system in Hertz, Mm is the mechanical mass of the system and Rm is the frictional loss in the system. Increase the mass, and more energy is stored in the system. Increase the friction, and more energy is dissipated from the system The electrical Qe of the system results, again, from the energy stored in the moving mass, but now dissipated by the electrical resistance in the system. It is calculated as: Mm Qe = 2 pi F ------- Re 2 2 B l Here, B represents the magnetic flux density in the voice coil gap, l is the length of wire in the magnetic field, and Re represents the DC resistance of the voice coil. We can also speak, of course, of the total Q, or Qt, of the system due to the combined mechanical and electrical damping, and it's calculated by the familiar formula: Qm * Qe Qt = --------- Qm + Qe The lower the Q, the more damped the system is. The higher the Q, the less damped. 3 THE INTUITIVE PREMISE Here's the claim: putting speakers in series is a bad idea because the series resistance of one speaker destroys the damping of the other. Why, even the equation for electrical Qe above says so: having two voice coils in series doubles the voice coil resistance (assuming the voice coils are the same, for simplicity). So it must logically follow that adding two speakers in series must severely destroy the damping, and the equation above shows that it should double. It makes intuitive sense. It even seems to appeal to technical authority. But will it stand up to analytical and empirical scrutiny? Is this, perchance, another widely held belief that might not be so? 4 ANALYSIS We'll consider the case where we are connecting two of the same thing in series, be it two identical woofers in an enclosure or two identical speakers in series. We're using identical woofers or systems to make the analysis simpler(3). Let's first look at the effects of two speakers in connected together in the mechanical domain. It might seem obvious, but since no electrical effects are considered in the mechanical domain, it makes no difference on the mechanical damping or Qm whether two speakers or two woofers are connected in series or parallel. Indeed, it doesn't even make any difference if they aren't connected at all electrically. In the mechanical case, we have doubled the moving mass Mm to 2*Mm to (we have twice as many cones, after all), but we have also double the amount of frictional Rm loss from to 2*Rm as well (twice as many surrounds and spiders, too). Plugging these changes into the equation for mechnaical damping, we find: 2 Mm Qm = 2 pi F ------ 2 Rm We can simplify: in the equation 2/2 is equal to 1, and we thus end up with: Mm Qm = 2 pi F ---- Rm This equation, describing the effect on Qm of connecting two speakers in series, is precisely the same equation for the case of a single speaker by itself. Now, let's look at the electrical damping or Qe. Here, we have, indeed, doubled the resistance Re to 2*Re (the voice coils are hooked in series), but we have also doubled the moving mass from Mm to 2*Mn as well and we've also double the length of the voice coil wire from l to 2*l sitting in the magnetic field as well. Now, let's plug all those factors of two into the equation for electrical Q: 2 Mm Qe = 2 pi F ---------- 2 Re 2 2 B (2l) The next step expands and combines terms: 2 Mm Qe = 2 pi F --------- 2 Re 2 2 B 4 l In another step, let's accumulate all these new factors (2 from the doubling of mass, 2 from the doubling of the voice coil resistance, and 4 from the square of the doubling of the length of the wire) together for the numerator and the denominator: 4 Mm Qe = 2 pi F - ------- Re 4 2 2 B l And, since the fraction 4/4 is equal to 1, we can reduce this equation to: Mm Qe = 2 pi F ------- Re 2 2 B l Again, this result, showing the Qe electrical of two speakers connected in series, is identical to the case of just a single speaker. Thus the analysis clearly shows that the damping is not severely compromised by connecting two systems or drivers in parallel, because the measures of damping, Qm and Qe, remains the same for both the mechanical and electrical domains, and thus the total also remains the same. Q.E.D. 5 EMPIRICAL SUPPORT The intuitive premise makes one clear prediction: the damping is seriously compromised by placing two speakers in series. This must be manifested by a substantial increase in the Q factors of the speaker. Specifically, the premise predicts that the electrical Q factor should be much greater. How much greater is not clear, because the premise is woefully short of analytical precision. But let's say that we should see at least a doubling of the electrical Q. And since the electrical damping predominates in most speakers, the total Q should be similarly affected. On the other hand, our analysis above predicts that the Q factors should remain essentially unchanged. Such an unambiguous difference makes this discussion an ideal candidate for falsification by experiment(4). For the first experiment, I selected two woofers, a pair of Seas PR17RC 6 1/2" woofer-midrange drivers. I measured the relevant parameters, the DC resistance, resonance and the mechanical, electrical and total damping of each separately, and then with the two connected in-phase in series to see the effect on damping of such a series connection. The actual results are shown in Table 1: Measurement Prediction Parameter A B A+B Analytical Intuitive ------------------------------------------------------------ Resonance F 71.20 69.03 70.1 DC resistance Re 5.72 5.70 11.42 Damping Mechanical Qm 1.29 1.33 1.32 Electrical Qe 0.88 0.92 0.91 ~0.90 1.80 Total Qt 0.52 0.54 0.55 ~0.53 1.06 ----------------------------------------------------------- Table 1: Driver Measurements The data would seem to strongly support the analytical method's predictions, and refute those of the intuitive model. That's fine for single speakers, and this result has been validated in numerous home-built systems using multiple drivers in series. It might be a different question, though, for complete speaker systems, often the situation found in some installations. So, I went to my storage room and grabbed a pair of rather ordinary bookshelf speakers, some ancient ones made by the old H. H. Scott company. I could well have used any two speakers, but there were handy and fully functional. I measured the resonant frequency, the DC resistance of the voice coil, and the relevant Q factors for each speaker alone, and the two in series. Along with these numbers, I also present the predictions made by the two competing theories, the "intuitive" premise, and the "analytical" theory described above. The results are shown in Table 2. Measurement Prediction Parameter A B A+B Analytical Intuitive ------------------------------------------------------------ Resonance F 110.5 113.7 112.6 DC resistance Re 6.86 6.87 13.90 Damping Mechanical Qm 2.77 3.06 3.15 Electrical Qe 1.02 1.09 1.14 ~1.06 2.28 Total Qt 0.75 0.80 0.83 ~0.80 1.6 ------------------------------------------------------------ Table 2: Speaker System Measurements It would seem that the empirical data strongly supports our analytical model, and strongly refutes the intuitive premise. Q.E.D. 1 FREQUENCY RESPONSE ERRORS One problem with two speakers in series is that the frequency dependent impedance variations of one will upset the frequency response of the other, and vice versa. As it turns out, this is not the case as well. Consider how the attenuation arises. Take the case of two resistances in series, R1 and R2. Given an impressed voltage of Vs, we can calculate the voltage across . The current through the entire circuit, will, by Ohm's law, be: Vs I = --------- R1 + R2 Given that current, again, by Ohm's law, the voltage across R2 will be: Vr2 = I R2 And, combining these two equations and simplifying, we find that: R2 Vr2 = Vs ------- R1 + R2 Now, in the case where R1 = R2, this reduces to simply: 1 Vr2 = --- Vs 2 Now, this can be generalized for impedances. If the impedances are the same, we can say that: Z2 Vz2 = Vs --------- Z1 + Z2 Z1 and Z2 represent the complex, frequency dependent impedances of our loudspeakers. If Z1 = Z2, which would be the case if our two speakers are the same (and this includes the frequency-dependent impedance variations as well), then our equation reduces to the fact that the voltage across each speaker would be: 1 Vz = --- Vs 2 Notice the complete absence of any frequency-dependent terms in this final equation: with two identical speakers in series, the voltage across each is simply 1/2 that of the voltage the amplifier is producing across the total, and is independent of frequency. There are, thus, no frequency-dependent variations in frequency as a result of putting two identical speakers in series. Q.E.D. ----------------------- Footnotes (1) One often encounters hi-fi accessories, for example, that utilize "mass damping" to control resonances. That adding a mass will change a resonant system is hardly in dispute, that it "damps" a resonance is altogether a different and quite incorrect claim. (2) There are other loss mechanisms, most notable the acoustical losses. However, for direct radiator loudspeakers, these loss mechanisms are quit insignificant, most often representing less than 1% of the total losses. Not coincidentally, this number is not too dissimilar form the acoustical efficiency of such speakers as well, because in order to produce sound, real work has to be done, and it is the work done into these acoustical "losses" that actually is the produced sound. Eliminate the acoustical loss, say by taking away the radiation load by putting the speaker in a vacuum, and you've eliminated the sound. Not an entirely useful exercise for something like a loud "speaker." (3) While the case of non-identical drivers or systems is more complicated, the general principles apply, though there are confounding factors such as frequency-dependent attenuation resulting from different frequency-dependent impedances. (4) "Falsification" is a vital part of the scientific method. A theory must be falsifiable, that is, it must make a prediction that, by experiment or observation, can be clearly shown to be right or wrong. In the case we have here, either one theory, the other theory, or neither theory will be supported by the experimental data. No data can support both. If a theory makes a prediction that can't be tested, it's no good as a theory. You might have a theory: "I can levitate myself while no one is looking." It's impossible for anyone else to construct a test, because they can never look at you doing what you claim, thus the "theory" has no value scientifically. ----------------------- Copyright (c) 2000-2001 by Dick Pierce. Permission given for one-time no-charge electronic distribution with subsequent followups. All other rights reserved. -- | Dick Pierce | | Professional Audio Development | | 1-781/826-4953 Voice and FAX | | | |
#35
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4 speakers from a power amp instead of 2 (question)
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#36
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4 speakers from a power amp instead of 2 (question)
"Scott Dorsey" wrote ...
William Sommerwerck wrote: This long and currently pointless (or at least meandering) thread began when someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts of time answering questions that are covered in library books. There has got to be a better way to direct people to the information they need. That IS what the FAQ is for, isn't it? If only it were posted online in a reliable place. www.recaudiopro.net has been offline for what, several years now? |
#37
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4 speakers from a power amp instead of 2 (question)
In article , "Richard Crowley" wrote:
"Scott Dorsey" wrote ... William Sommerwerck wrote: This long and currently pointless (or at least meandering) thread began when someone largely ignorant of the most-basic electronics theory asked a question he probably had no real interest in the answer for. I see this over and over. People trying to be helpful spend huge amounts of time answering questions that are covered in library books. There has got to be a better way to direct people to the information they need. That IS what the FAQ is for, isn't it? If only it were posted online in a reliable place. www.recaudiopro.net has been offline for what, several years now? Should be here just fine..... http://www.faqs.org/faqs/AudioFAQ/ |
#38
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4 speakers from a power amp instead of 2 (question)
1 INTRODUCTION I got that from Google. greg- thanks that was a good paper but it did not include the effect of the amplifer output Z which Arny correctly pointed out will be reduced to 1/2 for speakers in series. Not an important factor these days.. Mark |
#40
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4 speakers from a power amp instead of 2 (question)
On Wed, 3 Dec 2008 06:20:58 -0800 (PST), Mark
wrote: For four identical speakers in series-parallel, the load to the amplifier is the same as that of one of the speakers, and each speaker gets 1/2 the voltage and 1/2 the current from the amplifier, so sees the same source impedance as a single speaker. the question is not about what load the AMP sees, you are correct what you said about what load the amp sees but that is not in question, the question I am discussing is not what load that the amp sees but rather what does each speaker see as a source Z driving it...this is what determines the damping factor for the speaker.. in the case of one speaker, the speaker obviously sees the output Z of the amp. The question at hand is what does each speaker see as a driving Z when two speakers are connected in series.. and it is not a simple question as it first appears..... It's certainly interesting, and Don's analysis assuming perfect similarity is great. Duh, the guy's solid. But I think that the key to the puzzle is contained in the identity of the series-parallel quad load and a single speaker load. The amplifier cannot distinguish between the quad and the single. It operates exactly the same with either load at any particular electrical output level. But also, each of the drivers in the quad gets 1/2 of the voltage and 1/2 of the current from the amplifier. No single (identical! by definition) driver can deviate from its 1/2 and 1/2 allotment (because identical by definition), so the quad of drivers behaves electrically exactly like a single driver. (*Noting that real drivers couple acoustically, usually pretty weakly, but still...) So, at the interface between amplifier and speaker, there's no difference between single or identical quad. And, no individual driver of the quad can (by definition) behave differently than a single... Long way around the topic, but, as you've said, it's an interesting 'un. Much thanks, as always, Chris Hornbeck |
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