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Speakers conection ; series or parallel?

I have in mind to build a 2x12" speaker cab. What I want to know is if conecting the speakers in series gives me a different sound than conecting them in parallel. I know it chanches the impedance but I really don't know how or if it has any effect on the sound. Thanks.

jj
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Re: Speakers conection ; series or parallel?

8/14/2001 12:20 AM

Mark Tozer (1158) wrote:

Hi Juan,

Theoretically (in a perfect world ) the sound should be no different as each speaker will still have the same amount of drive (power) applied to it. However as you say the connection method will affect the boxes impedance.

As long as you switch your amp to the selected box's impedance you shouldn't notice any difference in sound quality or level.

Of course this is all theoretical so experiment with different wiring of speaker combinations BUT do your box impedance calcs and remember to set your amp accordingly.

Best of luck,
Mark.



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Re: Speakers conection ; series or parallel?

8/14/2001 3:50 PM

Rick Payman (10046) wrote:

Actually, for a given amplifier output voltage, in theory you should get 4 times the power output using a parallel connection than you would with a series one.

Basic electric formulas :-
V = Amplifier Output Voltage
I = Output Current
R = Speaker resistance (actually impedance)
P = Power

V = I * R
P = V * I = (V * V) / R


For a parallel connection, the power in each speaker is ( V * V ) / R, giving a total power output of ( 2 * V * V )/ R

For a series connection, only half of the amplifier voltage appears across each speaker, giving a total power of
( 2 * (V /2) * (V/2) ) / R, or ( V * V )/ (2 * R) i.e. 1/4 of that in the parallel case.

A simpler way of looking at it is that the load impedance is four times lower in the parallel case than in the series case; that's four times the current for a given output voltage.

This all assumes a perfect amplifier (zero output impedance) - a real amplifier would give less than a 4 to 1 power ratio output.
Also note that you can never get more output than the total power rating of the amplifier.

I think - Rick.





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Re: Speakers conection ; series or parallel?

8/14/2001 4:06 PM

Chris Frechette (1416) wrote:

It can't be four times.two identical resistors wired in parallel will drop in half.so output will double in a perfect amp.





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Re: Speakers conection ; series or parallel?

8/14/2001 4:25 PM

Rick Payman (10046) wrote:

The power is proportional to the square of the voltage, so half the voltage = quarter of the power.





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Re: Speakers conection ; series or parallel?

8/14/2001 4:35 PM

Rick Payman (10046) wrote:

Sorry, I think I misunderstood your point.
You appear to be comparing the case of a single loudspeaker, with that of two wired in parallel, in which case the output will double as you state.
However, for two speakers wired in series, the output will halve compared to the single case.
Still gives a difference of 4/1 between parallel/series configurations.





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Re: Speakers conection ; series or parallel?

8/14/2001 4:49 PM

Chris Frechette (1416) wrote:

Depends.. if it is a stereo amp or mono amp.

generally speaking a 2 x 12 cabinet would have a single input so parallel will give you twice the current,twice the cone area so it would give you 6 db in a perfect world but in reality it would give you 3 db.in a series configuration you get twice the cone area but twice the resistance so you get no gain...I dont understand the 4/1 ratio.
basic ohms law is e=ir.e= voltage,i=amperage,r= resistance.the voltage doesn't change only the current changes in respect to the resistance.so if an amp puts out 2 volts the current into 8 ohms would be .25 amps.into 4 ohms the current would be .5 amps.





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Re: Speakers conection ; series or parallel?

8/14/2001 4:59 PM

Chris Frechette (1416) wrote:

BY the way I'm not saying that you're wrong ..it just doesn't make any sense to me.





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Re: Speakers conection ; series or parallel?

8/14/2001 5:06 PM

Rick Payman (10046) wrote:

When you apply a given voltage across a single resistor, and then across two identical resistors in series, the current will halve as you state.
However, the voltage across each resistor will also halve - a simple potential divider - the two halves adding up to the whole (as it were).
So, each resistor has not only half of the current, but also half of the voltage, or 1/4 of the power (times the two resistors == half power).





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Re: Speakers conection ; series or parallel?

8/14/2001 5:14 PM

Chris Frechette (1416) wrote:

Ok i get it you are referring to each individual speaker not the system as a whole.you're right but i would be careful with it because people who are not experinced with this type of thing would get confused fast.I work for a Diy speaker company as a tech and people want to know how the system is going to behave .The individual performance only matters in relation to power handling.





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Re: Speakers conection ; series or parallel?

8/14/2001 5:32 PM

Rick Payman (10046) wrote:

Well, I'm not actually experienced with this type of thing! I was just applying Ohm's Law like yourself.
And I was only calculating the speaker Input power. You probably know more about how this relates to sound pressure levels (dBSPL) and acoustic power (dBPWL), which is another matter entirely.
Rick.



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Re: Speakers conection ; series or parallel?

8/16/2001 12:04 AM

Mark Tozer (1158) wrote:

Hi Juan,

I made a couple of assumptions in the above post:-

1. that you're using a valve amp with selective output impedance tappings and

2. you understand how to set and match those tappings to suit the total impedance of your box.

I think this explains it pretty simply.

If you have an amp head capable of delivering 100W into its rated load (can be 4, 8, or 16 ohms)
it should deliver that power into that load.

How that load is derived within the box (be it series, parrallel or a combination of both types of connections is of no consequence.

A solid state amp is a different kettle of fish.
they normally don't use an output transformer and don't have impedance select. A S/S amp is a lot more forgiving in the load presented to it.

If it is rated at 8 ohms output (nominal) and you run a 4 ohm box from it the amp will try and run four times the power to that box at full power.
Not good for the amp although some will handle it.
Some have current limiting in the o/p stages and will shut down. Some will just cook themselves.

If you run a lower impedance box from a valve amp you run a very real risk of overheating the o/p trannie or cooking your o/p stage of the amp as it will also try to 'put out more power'.

These are only my thoughts and observations so I may be wrong.

Mark.






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Re: Speakers conection ; series or parallel?

8/17/2001 11:05 PM

Juan Jos Elas (535) wrote:

Hi, Mark
Your assumptions were rigth. I'm using a valve amp, I can choose beetwen 4 or 8 ohms, and I know how to wire the speakers to get the impedance I need. I just wanted to know, from someone's experience, if it would produce any change in the final sound.

Thanks for your reply.

jj

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