Series VS Parallel Advantages/disadvantages.

[bjm362]

What I am looking at, asking about is are there any advantages and or disadvantages I am unaware of in a series circuit versus a parallel circuit. I am not trying to compare different impedance loads per se, but different methods of achieving the same load.

Examples

1) Two 16 ohm drivers in parallel to achieve an 8 ohm load.

This circuit is frequently used by manufactures as each driver only sees half the current, therefore increasing reliability.

2) Two 4 ohm drivers in series to achieve a 8 ohm load.

This circuit is frequently used by pros and DY'ers as the amp sees the same impedance load and both drivers see the full current. It is more efficient, but both drivers must be capable of handling the full power.

 

 

Is there any other advantages I am missing?

 

[onelife]

Power is the product of Voltage times Current and Voltage is the product of Resistance (Impedance) times Current.

 

100 Watts into 4 Ohms is 5 Amps of current while 100 Watts into 16 Ohms is only 2.5 Amps.

 

Whether the two 8 Ohm speakers are wired in series or parallel, they will each receive the same ammount of Current (as long as the impedance of the amplifier and speakers are properly matched)

 

 

http://www.aikenamps.com/index.php/ohm-s-law

[bjm362]

I appreciate your response, however neither of the circuits you mentioned are the circuits I am trying to discuss. I am not looking at how to use two 8 ohm drivers. I am looking at different methods of achieving an 8 ohm load and their individual advantages/disadvantages.

Again:

1) 2 x 16 ohm drivers in parallel is 8 ohms

2) 2 x 4 ohm drivers in series is 8 ohm

 

In both examples, the amp sees the same load and produces the same power. There is a difference in how the power is distributed. I hope this is a little clearer. I am very aware that amps do not have to work as hard to produce the same power when the impedance load is lower....that is until the load becomes lower than they are stable.

 

[onelife]

I understand what you are getting at now.

 

Although it is ultimately excessive Current that would burn out the voice coil, speakers are rated for the Power handling capacity (which is directly related). The Power rating for a speaker will take into account the Impedance.

 

Whether you achieve 8 Ohms with two 4 Ohm or two 16 Ohm drivers, the power will be evenly distributed between the two although the current in the series circuit vs the parallel will be different as you stated in the OP.

 

The Voltage across each driver will also be different in the series vs parallel configuration - full Voltage in parallel but only half in series.

 

I don't see any advantage to one configuration over the other but you have certainly provided some food for thought.

 

[bjm362]

I understand what you are getting at now.

 

Although it is ultimately excessive Current that would burn out the voice coil, speakers are rated for the Power handling capacity (which is directly related). The Power rating for a speaker will take into account the Impedance.

 

Whether you achieve 8 Ohms with two 4 Ohm or two 16 Ohm drivers, the power will be evenly distributed between the two although the current in the series circuit vs the parallel will be different as you stated in the OP.

 

The Voltage across each driver will also be different in the series vs parallel configuration - full Voltage in parallel but only half in series.

 

I don't see any advantage to one configuration over the other but you have certainly provided some food for thought.

 

I am glad you now have the premise of the question. It is nice to have created some food for thought too.

I am already aware of some advantages and disadvantages of both circuits as well as why a lot of people do not realize them. I was hoping we might get a response to the part about are there any other advantages/ disadvantages besides the ones I listed.

If going back over the ones I do know about helps you, I can feel pretty good about that too.

 

Both circuits having equal resistance.

1) In the parallel circuit each driver sees half the load providing less strain on each driver, so it has the advantage of being more reliable.

2) In the series circuit both drivers voice coils have the full current of the circuit pass through them. Both drivers then are driven more efficiently. However this does create some increased potential for easily exceeding the power handling of the driver.

The reason most people never realize this is thy normally compare two driver setups with different impedance loads.

BTW, I really like your signature and think it is relevant to this thread. This is an example of looking at a bigger picture........

IE: "having new eyes"!

 

 

[isaac42]

As far as the amplifier is concerned, the circuits are essentially the same. As noted above, power and current are not the same thing. In a series, circuit, the drivers see the same current, but not the same voltage. Power is voltage times current, so the drivers split the power by virtue of splitting the voltage. In the parallel configuration, the drivers see the same voltage, but split the current. As before, each driver sees only half the power. So, in either case, each driver dissipates half the power.

 

However, there are still differences to take into account. In the parallel circuit, if one driver fails, the other will still function. Output will go down, but only by 3dB. In the series circuit, if one driver fails, there will be no output, as there will be no current path. Another factor is that no two drivers are exactly identical. In the parallel circuit, the discrepancies are minimized, and the drivers share the load better. That's why I, at least, prefer the parallel configuration over the series.

[WRGKMC]

The short answer is, so long as the speakers total wattage and impedance is correct for the amp, you shouldn't hear any differences.

 

If you have a choice when buying speakers, I'd stick with running higher ohm speakers in Parallel. If one speaker blows in parallel, the amp will still see a load from the remaining speaker. When they are in series, one blows and you have a completely open circuit.

 

 

[onelife]

good point - a definite advantage to running parallel

[bjm362]

As far as the amplifier is concerned, the circuits are essentially the same. As noted above, power and current are not the same thing. In a series, circuit, the drivers see the same current, but not the same voltage. Power is voltage times current, so the drivers split the power by virtue of splitting the voltage. In the parallel configuration, the drivers see the same voltage, but split the current. As before, each driver sees only half the power. So, in either case, each driver dissipates half the power.

 

However, there are still differences to take into account. In the parallel circuit, if one driver fails, the other will still function. Output will go down, but only by 3dB. In the series circuit, if one driver fails, there will be no output, as there will be no current path. Another factor is that no two drivers are exactly identical. In the parallel circuit, the discrepancies are minimized, and the drivers share the load better. That's why I, at least, prefer the parallel configuration over the series.

 

I do appreciate EVERYONE'S response. You have reminded me of one disadvantage of the series circuit I had forgotten to consider. If one driver interrupts the circuit, then the circuit ceases to function (Infinite resistance).

 

However I would like to further discuss an observed phenomena that defies electronic theory as expressed here. Hopefully some will recall that Sir Isaac Newton said "If the phenomena does not fit the theory, then the theory is flawed". This part of how he came to be sure that the retrograde motion of Venus and Mars proved the Earth circled the Sun.

 

Back to circuits for a moment. (BTW, even if what I am proposing ultimately proves to be incorrect, I will still appreciate all participation. Also I intend to show WHY I am not just accepting this without argument.) First of all life's experience has taught me that AC and DC circuits disperse energy slightly differently. There is a point where a DC circuit can at least appear to defy the law of conservation.

 

Remembering that an amplifier is a DC device that by modulating in some ways acts like an AC device...but is still DC.

In a DC circuit wire runs limit distance substantially as the current must travel the entire distance of the circuit. In an AC circuit the current travels the distance of one electron.

The difference then between the parallel circuit and the series circuit is the parallel circuit does not see the entire current,but each added device reduces the impedance increasing the power. Series circuits the entire current passes through each device. Also each device increases the impedance, reducing the power

 

Most comparisons between these circuits involve equal impedance devices, resulting in the parallel circuit far out performing the series circuit..

The Series circuit in this configuration has been observed in my life's experience as a child with light bulbs to put out MANY more lumens than the parallel circuit of equal resistance. The parallel circuit of LOWER impedance puts out more lumens than the series circuit of higher impedance(4 ohms vs 16 ohms), but that IS NOT the case with equal impedance circuits.

 

All other parameters being relatively equal except the impedance of the devices being combined the series circuit will out perform the parallel circuit with the same load.

 

I am taking into account that my observations that support this theory are from memory...both with lightbulbs and with a couple of pairs of different impedance 8 inch speakers many many years ago. I realize that I am human and my memory can be flawed. I do intend to test this again soon

 

I have some examples to express, to show my reasoning but have had too many interruptions for a moment. I will add another reply with examples a little later for those that would like to continue exploring this.

 

 

[onelife]

You must also take into consideration loading - what happens to the sound of an electric guitar with high impedance pickups when it is connected to a low impedance load.

 

The guitar pickup generates an electric current. The voltage produced by that current depends on and is directly related to the impedance of the load. If the impedance is too low the resultant voltage will be low. Since impedance is frequency dependant the resulting sound will lack clarity and will sound weak and dull.

 

Since power is the product of voltage time current and a lower impedance can lower the voltage (for a given ammount of current), lowering the impedance does not always result in more power. Matching impedance will provide the best results.

[bjm362]

Despite the difficulties and expenses of doing real world testing of this, after doing a little bit of discussion I feel like it is possible to explore this well enough to set up some reasonable test models.

 

Using a single channel of an amp that is stable down to 2 ohms, here are the power outputs at different impedance values expressed in watts.

@ 16ohms ??? watts (spec not given, but should be somewhere around 250 to 260 watts) I think we should just use 255 W for the moment.

@ 8 ohms 440 watts

@ 4 ohms 860 watts

@ 2 ohms 1600 watts

 

If we say our power supply and electronics are perfect (does not happen in the real world) the math is simpler. Our values are the 250,500, 1000 and 2000.

 

In our theoretical test model we are going to also include two drivers having an efficiency drop due to mass increase as well as two drivers coupled well having an output increase from the coupling. They essentially offset each other anyway and it makes this a little easier.

One of the difficulties in doing a real world test is not many (if any) drivers have essentially the same model available in 4 ohm, 8 ohm and 16 ohm versions.

It may be easiest to consider excursion as our PE (Power Expressed). Manufacturers power ratings are thermal to the voice coil, most drivers barely approach the manufacturers power rating as the voice coils will normally take a bit more heat than the available xmax.

 

Real world excursion would be a bit different too, due to several factors. Any experts that are so inclined to deal with all the math involved are welcome to do so.

We also need to consider Volume displaced.

I am going to use for a basis a a driver that I actually have two different versions of essentially the same model. Identical VD, identical Xmax but in 4 ohm and 8 ohm versions. We will theorize a 16 ohm version with essentially the other specs the same.

This driver is rated at 350 watts C and 700 P respectively but with an xmax of 7mm we know those values are advertised. At about 375 watts it should be right at xmax headed for xlimit (permanent damage)

Again making our math simpler we can use 1 mm per 100 watts ( then it really would handle 700watts!) LOL!

 

So we now have the following in our theoretical model expressed in excursion.

single 16 ohm--- 2.5 mm

single 8 ohm--- 5.0 mm

single 4 ohm--- 10mm ( and a blown driver)

single 2 ohm --- not available... but if it were we would have smoke coming from the voice coil anyway.

 

Pairing 2 drivers in parallel we have.

2 16 ohm in P 500w /2 drivers, 2.5 mm each

2 8 ohm in P 1000w / 2 D, 5mm each

Anything lower than this still getting blown.

 

Pairing drivers in series we have the amp producing half the power compared to a single driver of the same impedance, but the drivers each see the entire quantity of power produced.

2 16 ohm in S is 32 ohms, or a 125 watt circuit for 1.25 mm each.

2 8 ohm in S is 16 ohms, or a 250 watt circuit for 2.5 mm each

2 4 ohm in S is 8ohms, or 500 watt circuit for 5.0 mm each

 

If you do the math there are points and ways where they are equal, and points and ways they are not.

 

A single driver of the ones I have have a surface area of 552 square Cm and an xmax of 7mm. VD is then 3864cc at 7mm, or 552 cc per mm of xmax.

 

So we then consider the following 8 ohm circuits.

Single 8 ohm @ 5.mm = 2760 cc VD and should not exceed Xmax.

2x 16 ohms in P 2x2.5mm = 2760cc VD, is even more reliable and will play slightly lower than a single driver.

2x 4 ohms in S is 2x5mm =5520cc VD, (Twice the volume) is within reasonable reliability potential and plays as low as the two drivers in parallel.

 

If the requirement is for an 8 ohm box, in truth 2 4ohm drivers in series rules in the lower frequency. If 4 ohms per box is acceptable then 2 8 ohm drivers in parallel rules.

 

 

 

[isaac42]

You have an erroneous assumption. "Pairing drivers in series we have the amp producing half the power compared to a single driver of the same impedance, but the drivers each see the entire quantity of power produced." The drivers in series see all of the current, but, as discussed above, they see only half of the voltage and therefore only half of the power.

 

Therefore:

2 16 ohm in S is 32 ohms, or a 125 watt circuit for 0.625 mm each.

2 8 ohm in S is 16 ohms, or a 250 watt circuit for 1.25 mm each

2 4 ohm in S is 8ohms, or 500 watt circuit for 2.5 mm each

 

The performance is exactly the same.

[bjm362]

You must also take into consideration loading - what happens to the sound of an electric guitar with high impedance pickups when it is connected to a low impedance load.

 

The guitar pickup generates an electric current. The voltage produced by that current depends on and is directly related to the impedance of the load. If the impedance is too low the resultant voltage will be low. Since impedance is frequency dependant the resulting sound will lack clarity and will sound weak and dull.

 

Since power is the product of voltage time current and a lower impedance can lower the voltage (for a given ammount of current), lowering the impedance does not always result in more power. Matching impedance will provide the best results.

 

I am about to leave this one alone, but I had overlooked this reply. You make a good point and a good read onelife!

 

I should have been clearer on the amp I am using and the reasons I am overthinking this.

The type of is PA. The channel I quoted specs on before altering them to simplify the math was actually one of 4. It is Behringer NU4 6000.

The reason for all this extra effort in thought on this has to do with several factors. I am old and have a bad back. My limited budget will not allow me to purchase what I would like in PA gear. I am looking to build something very special for PA cabinets, but I need all of the decisions to good ones. I also cannot afford to get it wrong. Building is still an expensive proposition....

I need my next cabinets to be capable from large clubs to smaller outdoor festivals. I also need to be able to upscale simply adding cabinets. I need them to stack or fly well. I need them to couple well. I need them to play low enough that on smaller gigs they can be used with out subs. Those are a lot of parameters to fill on a tight budget.

I am actually looking at drivers for the LF section only in this example, I am trying to get as close as I can to a SMOOTH 110db 1w/meter. ....without adding too much weight! Hah! Talk about shooting for the stars!!!

I am about to call it a night.

I do have one more thing to address first.

 

You have an erroneous assumption. "Pairing drivers in series we have the amp producing half the power compared to a single driver of the same impedance, but the drivers each see the entire quantity of power produced." The drivers in series see all of the current, but, as discussed above, they see only half of the voltage and therefore only half of the power.

 

Therefore:

2 16 ohm in S is 32 ohms, or a 125 watt circuit for 0.625 mm each.

2 8 ohm in S is 16 ohms, or a 250 watt circuit for 1.25 mm each

2 4 ohm in S is 8ohms, or 500 watt circuit for 2.5 mm each

 

The performance is exactly the same.

 

You are still comparing a single 8 ohm driver to two 8 ohm drivers in series. 8 ohm load versus 16 ohms

I am comparing two 16 ohm drivers in parallel versus two 4 ohm drivers in series.

Or you are dropping power twice for the resistance, I am not sure which.

 

Amplifier is pushing voltage, current is decided by the resistance.

 

 

[1001gear]

In a series configuration, does the first driver bear the brunt of any errant voltage/current?

[isaac42]

You are still comparing a single 8 ohm driver to two 8 ohm drivers in series. 8 ohm load versus 16 ohms

I am comparing two 16 ohm drivers in parallel versus two 4 ohm drivers in series.

Or you are dropping power twice for the resistance, I am not sure which.

 

Amplifier is pushing voltage, current is decided by the resistance.

No, I am not. I am making the same comparisons you are. Two 4 ohm drivers in series each see all of the current but only half the voltage and therefore half the power. If the amplifier is putting out 500 watts, each driver will see 250 watts. Changing the driver impedance changes the amount of power the amp puts out, but doesn't change the fact that the drivers share the power.

 

Here are the corrected power excursions, based on your assumptions:

 

single 16 ohm--- 2.5 mm

single 8 ohm--- 5.0 mm

single 4 ohm--- 10mm ( and a blown driver)

 

Pairing 2 drivers in parallel we have.

2 16 ohm in P 500w /2 drivers, 2.5 mm each

2 8 ohm in P 1000w / 2 D, 5mm each

 

Pairing drivers in series we have the amp producing half the power compared to a single driver of the same impedance, but the drivers each see half the power produced.

2 16 ohm in S is 32 ohms, or a 125 watt circuit for 0.625 mm each.

2 8 ohm in S is 16 ohms, or a 250 watt circuit for 1.25 mm each

2 4 ohm in S is 8ohms, or 500 watt circuit for 2.5 mm each

 

[bjm362]

In a series configuration' date=' does the first driver bear the brunt of any errant voltage/current?[/quote']

 

Unfortunately yes. Oddly enough even with alternating current the power distribution is such that there is a "first driver". Those that remember when houses were still wired in series should remember that you would know what lightbulb would blow if there was a surge during a storm . Also unfortunately the other disadvantage of series then comes into play. I believe onelife and Isaac42 both pointed out that in a series circuit when one component fails, the other components stop working too.

[bjm362]

Isaac42, I first want to be clear that I am in NO WAY disrespecting you. However it does appear to me you are accounting for a single drop twice.

I do not want this to get out of hand, as long as we can continue to respect each other I would like to continue this discussion further to try and clear this up.

 

Fortunately, we are calculating power through a circuit and don't have to account for a speakers efficiency (or lack of). A simple application of Ohm's Law may clear this up.

I am calculating this bearing in mind that I can end up with an example that supports my statement, OR one that supports yours.

Ohms law

I=V/R

Using 60 volts applied to our 8ohm circuit #1 ( our two 16 ohm drivers in parallel) we do not get our simplified math virtual 500 watts of power, we get a real world 450 watts. Since the manufacturer rates this amp at 440 into 8 0hms I might add they are claiming it to be very efficient!

 

7.5 amps=60V/8Ohms or 450watts

 

Our 8 ohm circuit #2 (two 4 ohm drivers in series) is Still an 8 ohm circuit. Our 60v amplifier still produces 7.5 amps or 450watts. Neither the voltage nor the current has changed. I believe we can agree on that.

In this regard we have both come to the same conclusion of this part of performance is the same.

 

There is however a difference between the circuits. The parallel circuit allows for a current drop at multiple places. It is then safer and more reliable. That is why manufacturers use it and part of why your house is wired the way it is.

The series circuit does not have that same safety/ reliability feature. The entire circuit sees the entire current. This phenomena is over looked because when you add equal components in a series circuit you have a current drop.

 

That would mean a single 4 ohm driver would produce the following...

 

15A=60V/4Ohms (900Watts) Add a 8ohm component in series and we get

7.5A=60V/8Ohms (450Watts) Add another pair in series and you get

3.75A=60V/32Ohms (225watts) etc...

 

The amplifier produces the voltage, the components provide the resistance, Ohm's law allows us to calculate what current that produces.

[1001gear]

 

Unfortunately yes. Oddly enough even with alternating current the power distribution is such that there is a "first driver". Those that remember when houses were still wired in series should remember that you would know what lightbulb would blow if there was a surge during a storm . Also unfortunately the other disadvantage of series then comes into play. I believe onelife and Isaac42 both pointed out that in a series circuit when one component fails, the other components stop working too.

 

Continuing this dilemma, doesn't that now become component protection?

[isaac42]

Why are you changing the parameters of the discussion? In doing so, you needlessly complicate things.

 

Nevertheless, using your new assumptions, the conclusions remain the same. Assuming a voltage source amplifier producing 60 watts, the results are as follows.

 

Single driver.

16 ohms - 225 watts, 3.75 amps

8 ohms - 450 watts, 7.5 amps

4 ohms - 900 watts, 15 amps

 

Parallel drivers; each driver sees full voltage, half current

2x16 ohms - 225 watts per driver, 3.75 amps

2x8 ohms - 450 watts per driver, 7.5 amps

2x4 ohms - 900 watts per driver, 15 amps

 

Series drivers,each driver sees full current, half voltage

2x16 ohms - 56.25 watts per driver, 1.875 amps

2x8 ohms - 112.5 watts per driver, 3.75 amps

2x4 ohms - 225 watts per driver, 7.5 amps

 

Note that the 8 ohm circuits all consume the same power and current: 450 watts and 7.5 amps. The single 8 ohm driver sees the full power and current, the parallel, 16 ohm drivers see half the power and half the current and the series 4 ohm drivers see all the current yet only half the power, because they see only half the voltage.

[isaac42]

Unfortunately yes. Oddly enough even with alternating current the power distribution is such that there is a "first driver". Those that remember when houses were still wired in series should remember that you would know what lightbulb would blow if there was a surge during a storm . Also unfortunately the other disadvantage of series then comes into play. I believe onelife and Isaac42 both pointed out that in a series circuit when one component fails' date=' the other components stop working too.[/quote']

No, there is no "first driver." In a series circuit, the current flows through both drivers equally or not at all.

[1001gear]

No, there is no "first driver." In a series circuit, the current flows through both drivers equally or not at all.

 

Then given drivers of equal properties, if one gives, all should give?

[isaac42]

Then given drivers of equal properties' date=' if one gives, all should give?[/quote']

Theoretically, yes. Of course, in the real world, things are never equal.

[bjm362]

I thank you for your patience isaac42. The way you expressed it this time jarred what was not registering in my memory. It has after all been 40 years since I read the difference between parallel and series circuits.

 

Parallel drivers; each driver sees full voltage, half current

Series drivers,each driver sees full current, half voltage

For some reason I was remembering that as "In the parallel circuit each driver sees the full power."

Hopefully that explains why every time I looked at your calculations I thought you were dropping power twice.

 

Why are you changing the parameters of the discussion? In doing so, you needlessly complicate things.

 

Sorry about that. When I decided to calculate voltage I got a little curious what voltage my NU4-6000 produces per channel (440watts @ 8ohms) or 59.33V per channel. In another forum commercial forum the Guru that owns had implied that the NU4-6000 was not any good (while unaware that I owned one) because it was not 60v per channel. I still think 59.33v is pretty close from a 4 channel amp. If I really need more than that I have two pairs that can be bridged to produce 109.54v each.

 

Processing all of this has really been good for me in deciding best power distribution plan and what I want to build.

 

Unfortunately, I still am not going to be able to accomplish what I want to without horn loading the LF section too.

[isaac42]

Glad we're finally on the same page!

[WRGKMC]

You're unfortunately mixing up allot of different stuff here and because you're missing some key factors your assumptions just aren't going to hold true.

 

First off, you are using specs from a voltage controlled power amp like a PA head which automatically change wattage as you change the load. Not all amps work this way and very few instrument amps.

@ 8 ohms 440 watts

@ 4 ohms 860 watts

@ 2 ohms 1600 watts

 

These are usually specs for voltage controlled power amplifiers used for Pro PA and some Hi Fi stuff. Guitar amps have a fixed wattage. The key item with Tube amps is the load must match the output secondary transformer winding to get maximum fidelity and wattage with the lowest distortion. Some transformers will allow a wider load range but the wattage doesn't increase, instead the signal may distort at a lower wattage. If the load is too great you simply fry your tubes because the current isn't being consumed like it should. .

 

Transistor amps allow a wider load range in many cases depending on the design. Most put out a maximum wattage with the recommended load and decrease as the load goes up.

 

I haven't got a clue why you posted everything else. If you are working with PA Gear then some of that is important but for most guitar or bass amps its irrelative.

 

The total wattage in series or parallel is the same.