Hi,
I was wondering how do i calculate the new efficiency for 4 identical drivers connected in 2s2p, if each of the drivers are 8ohm 90db/watt?
What about 16 drivers in 2s2p clusters of 2s2p still maintaining 8 ohm overall?
Is there a systematic way to calculate the new efficiency?
Thanks.
I was wondering how do i calculate the new efficiency for 4 identical drivers connected in 2s2p, if each of the drivers are 8ohm 90db/watt?
What about 16 drivers in 2s2p clusters of 2s2p still maintaining 8 ohm overall?
Is there a systematic way to calculate the new efficiency?
Thanks.
3db more efficiency each time you double the cone area. The load doesnt matter. so 4 speakers will put out 6 db more using the same amount of watts. 8 speakers would be 9db, 16 speakers would be 12db...
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Make it more complicated: 9 speakers arranged 3s3p?
Staying with baseline 90db/1W per individual speaker.
99.5424250943932487459005580651023db / 1W ?
figuring: 90 + ( 10 * LogBase10 ( nospeakers ) )
Staying with baseline 90db/1W per individual speaker.
99.5424250943932487459005580651023db / 1W ?
figuring: 90 + ( 10 * LogBase10 ( nospeakers ) )
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And stringing an array is further complicated that each driver's impedance
is affected by neighbors, reflections from the floor, and lack of neighbor.
Putting them all in parallel makes all the cones move (expressed in voltage)
equally regardless cone backpressure (expressed in current). But you can't
realistically wire all 16 in parallel or the impedance becomes too low. Any
wired in series have to be of equal impedance and cone load, else the lesser
loaded cones will move further (and drop unequal voltage) w. series current.
Since its probably 4x4 sitting on the floor, you got 6 speakers that will see 8
neighbors or reflections. 8 speakers that see 6 neighbors or reflections, and 2
speakers at the top corners that see only 3 neighbors. How you wire that?
I'm thinking 16 small individual amplifiers might be the more practical answer...
Assuming horizontal symmetry you aren't too near a wall, maybe 8 would do.
is affected by neighbors, reflections from the floor, and lack of neighbor.
Putting them all in parallel makes all the cones move (expressed in voltage)
equally regardless cone backpressure (expressed in current). But you can't
realistically wire all 16 in parallel or the impedance becomes too low. Any
wired in series have to be of equal impedance and cone load, else the lesser
loaded cones will move further (and drop unequal voltage) w. series current.
Since its probably 4x4 sitting on the floor, you got 6 speakers that will see 8
neighbors or reflections. 8 speakers that see 6 neighbors or reflections, and 2
speakers at the top corners that see only 3 neighbors. How you wire that?
I'm thinking 16 small individual amplifiers might be the more practical answer...
Assuming horizontal symmetry you aren't too near a wall, maybe 8 would do.
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Kenpeter,
I did think about the boundary effects, i will probably have mine in a 2x2, should be less than the theoretical 6dB gain.
In my case, the lower 2 drivers will 'see' the floor more than the others, but i'm not sure if that has enough impact to affect the electrical loading parameters.
I did think about the boundary effects, i will probably have mine in a 2x2, should be less than the theoretical 6dB gain.
In my case, the lower 2 drivers will 'see' the floor more than the others, but i'm not sure if that has enough impact to affect the electrical loading parameters.
As long as the drivers are located within 1/4 wavelength of each other, the four drivers will gain 6 db over one.
The Fs will lower slightly.
As an example, a single EVX-150 has a Fs of 35 Hz, two in close proximity 34 Hz, and four drops it to 32.5 Hz.
rhapsodee,
To add LF boundary impact on multiple driver speakers:
Use this calculator that handles 2 drivers at a time: See Room Response Calculator v0.6d link here below but it's easy to estimate/calculate the boundary gain for any numbers of drivers by using this graph: See the picture:
http://www.rsu.edu.ru/~foboss/hi-fi/acoustic/room060d.xls
b🙂
To add LF boundary impact on multiple driver speakers: Use this calculator that handles 2 drivers at a time: See Room Response Calculator v0.6d link here below but it's easy to estimate/calculate the boundary gain for any numbers of drivers by using this graph: See the picture:
http://www.rsu.edu.ru/~foboss/hi-fi/acoustic/room060d.xls
b🙂
Attachments
For 2x2 I'm suggesting:
Wire your floor speakers in one horizontal series string.
Wire top speakers in the other horizontal series string.
Parallel these two strings vertically back to 8 ohms...
Top and bottom strings are NOT same impedance or current.
But wired in parallel, all cones should move the same due to
equal voltage on every speaker. Theoretically, maybe, if...
Paradox that electric pressure (electromotive force) equates
to mechanical movement, and electrical movement (current)
equates to mechanical pressure. Somehow roles get swapped.
Magnetism, go figure...
I suppose its equally valid for all cones to see equal current
and pressure at different voltages and velocitys. But lighter
loaded cones might then exceed xmax earlier than the rest.
And that would limit the entire array.
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I have now some test boxes with the same problem 🙂 Also 4 mid-bass'es wired two in series and those paralleled. All seemed well, but when i run signal generator, there is one frequency when one "string" with two drivers stands still, and others to works normal. I believe there becomes some sort of resonance between them in particular freq. Thats why i rejected this type design.
rhapsodee,
Use this calculator that handles 2 drivers at a time: See Room Response Calculator v0.6d link here below but it's easy to estimate/calculate the boundary gain for any numbers of drivers by using this graph: See the picture:
http://www.rsu.edu.ru/~foboss/hi-fi/acoustic/room060d.xls
b🙂
An interesting observation is that the 0 line is equal to true free-field.
There is a fundamental violation of Kirckoff's Law (conservation of energy) going on here. If you have 1 watt into 1 speaker and the output is 90 db (1 watt/1 meter), what do you suppose one watt into 4 drivers will do?
The answer has everything to do with each driver dissipating 1/4 watt. That's a 6db reduction of power on each driver compared to the single driver. So the efficiency remains exactly the same, although due to the increased surface area greater LF extension is possible.
Now, if you are to use the word *sensitivity*, then all bets are off. Sensitivity differs from Efficiency in that it is measured in volts (2.83V/1 meter) not watts. If you have a transistor amp and the resulting load is a different impedance, this can have a pronounced effect on the result.
Actually it's both that increases at least if we talk about dynamic drivers. Efficiency is total sound power output per watt expressed in percentage and sensitivity is decibels per watt.
Example: we have 2 equal drivers, each having a sensitivity of 90dB/2.83V/m and they're both 8 ohm.
Now if we put them in parallel with a 2.83V input we measure a 6dB increase. Why is that? +3dB from they now receiving 2W of electrical power so 1W each and +3dB from doubling the magnet power.
If we then put them in series with a 2.83V input we then measure no SPL increase. Why is that? -3dB from they now only get 1/2W, ie. 1/4W each and +3dB from doubling the magnet power.
If we then put 4 in series parallel with a 2.83V input we then measure +6dB increase because it's no change in electrical power as each driver get 1/4W but +6dB from quardrupling the magnet power.
There's no violation of Kirckoff's Law going on because you forget that dynamic drivers are active elements with some kind stored energy, usually magnetic energy, of their own which slowly decreases over time and with use. Which is why a 30 year drivers have typically -3dB sensitivity from when they were new. This halving time of the stored energy can be faster or slower depending on use and physical location as it will decrease more nearer Earth's magnetic poles.
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One cone is rarely better than 2% efficient.
Room for many decibels of parallel coupling
improvement before we get no more free lunch.
Efficiency comes from better impedance match
to a smaller arc of air in the room. Each cone can
punch at the air a bit better, cause less undriven
space for air to escape out out the way.
Room for many decibels of parallel coupling
improvement before we get no more free lunch.
Efficiency comes from better impedance match
to a smaller arc of air in the room. Each cone can
punch at the air a bit better, cause less undriven
space for air to escape out out the way.
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The efficiency will remain the same whether you have 1 speaker or a thousand that are identical. The efficiency is defined as the conversion of electrical power into sound energy, ie how many watts of sound power out for how many watts of electrical power in.
However, the voltage sensitivity of the aggregate of an array can change depending on the way they are wired together. 2s2p will have the same impedance and the same sensitivity as a single driver. Speakers in parallel will have a lower combined impedance, draw more power and will be more sensitive. Speakers in series will divide the input voltage among them and be less sensitive. Arrays that are the perfect square of an integer 2s2p, 3s3p, 4s4p etc. will have the same sensitivity as an individual driver because the sereis and parallel combinations exactly offset each other. But of course they will have power handling capacity of the aggretage and will radiate from a larger surface area of cones. For a given sound output level, each speaker will do less work.
This is another way of expressing my point, Saturnus' earlier remarks missed the fact that Efficiency and Sensitivity are two different measurements, one based on power (thus requiring that that total power be distributed amongst the drivers) and the other based on voltage.
This has a lot to do with the interface between the amp and speaker. For example if you have tubes, the idea that there will be a 3 db addition of power by cutting the impedance in half does not work. So its important to keep that in mind: this concept only works with transistors!
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