Combined efficiency for 4 woofers connected in 2s2p

[rhapsodee]

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.

[nightanole]

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...

[kenpeter]

Make it more complicated: 9 speakers arranged 3s3p?
Staying with baseline 90db/1W per individual speaker.

99.5424250943932487459005580651023db / 1W ?

figuring: 90 + ( 10 * LogBase10 ( nospeakers ) )

[rhapsodee]

Thanks for the info!

[kenpeter]

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.

[rhapsodee]

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.

[weltersys]

Originally Posted by rhapsodee

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.

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.

[bjorno]

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/...c/room060d.xls

b

[kenpeter]

Originally Posted by rhapsodee

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.

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.

[GSP]

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.