Grandma´s_SUB said:
This is only correct when you start with one driver and add a second. The 3dB rise occurs every time the total number of drivers is doubled. Thus if you start out with four drivers, adding one will not increase your sensitivity by 3 dB. you'd have to add four drivers for a new total of eight to get a 3 dB increase over four drivers.
If one driver have a 90dB rating, then
two drivers in paralell will be 96dB at same voltage but drawing 2W instead of 1W. This is a net increase in efficiency of 3dB while voltage sensitivity is +6dB.
Connet 4 drivers in series paralell for an equal impedance as the 1 driver example, then the voltage sensitivity increases 6dB and efficiency also 6dB since the power will be 1w as with one driver.
Four drivers in paralell gives 102dB for the same voltage. 6dB increase in voltage sensitivity (due to 4x magnets and Bl product) and 6dB from the 4x power drawn from the amp.
/Peter
two drivers in paralell will be 96dB at same voltage but drawing 2W instead of 1W. This is a net increase in efficiency of 3dB while voltage sensitivity is +6dB.
Connet 4 drivers in series paralell for an equal impedance as the 1 driver example, then the voltage sensitivity increases 6dB and efficiency also 6dB since the power will be 1w as with one driver.
Four drivers in paralell gives 102dB for the same voltage. 6dB increase in voltage sensitivity (due to 4x magnets and Bl product) and 6dB from the 4x power drawn from the amp.
/Peter
Hi everyone!
Hm, I believe I cannot help too much according to this topic, but as I read your replies realized that you are my man!
)
I'm on to build two speakers that would be driven by a 2x25w amp, and want to use a only 2 speakers per box. Is there a mid and a high speaker needed? How should be designed, I mean both should be 25W speakers connected in series or with other one's with other power? What kind of connecting and what kind, type speakers should be used.
I'm trying to collect information bits from the net and other resources, but the more infos I get, the confused I'm!
Please help me!
Thank you and merry xmas!
With regard, Semir
Hm, I believe I cannot help too much according to this topic, but as I read your replies realized that you are my man!
)I'm on to build two speakers that would be driven by a 2x25w amp, and want to use a only 2 speakers per box. Is there a mid and a high speaker needed? How should be designed, I mean both should be 25W speakers connected in series or with other one's with other power? What kind of connecting and what kind, type speakers should be used.
I'm trying to collect information bits from the net and other resources, but the more infos I get, the confused I'm!
Please help me!
Thank you and merry xmas!
With regard, Semir
Pan,
Sensitivity of 4 drivers = +6 db from increased surface area(doubled twice)
4 drivers wired series parallel for same impedance as single= no gain electrically
Net= +6dB
Sensitivity of 4 drivers wired parallel would yield higher sensitivity based on amplifier's ability to play into the load=+6dB from increased surface area and +6dB electrically from lower impedance*
Net= +12dB with appropriate amp
*Most solid state amplifiers will not actually double current into lower impedance, but are assumed to. No change electrically with tube gear(4 drivers of 16 ohm impedance= 4ohm load with a yield from surface area gain only of 6 dB).
Sensitivity of 4 drivers = +6 db from increased surface area(doubled twice)
4 drivers wired series parallel for same impedance as single= no gain electrically
Net= +6dB
Sensitivity of 4 drivers wired parallel would yield higher sensitivity based on amplifier's ability to play into the load=+6dB from increased surface area and +6dB electrically from lower impedance*
Net= +12dB with appropriate amp
*Most solid state amplifiers will not actually double current into lower impedance, but are assumed to. No change electrically with tube gear(4 drivers of 16 ohm impedance= 4ohm load with a yield from surface area gain only of 6 dB).
Grandma's Sub
Two drivers wired in series gain 3db from a doubling of surface area but lose 3db electrically from the load"s higher impedance
Net=0 gain
Also, adding series resistance will not raise the impedance of the driver. A driver's impedance varies with frequency and is altered by capacitive and inductive reactance over a broad range.
I would be careful with multiple drivers wired in parallel. You can toast the amp. Consult the ownwer's manual or manufacturer.
Tim
Two drivers wired in series gain 3db from a doubling of surface area but lose 3db electrically from the load"s higher impedance
Net=0 gain
Also, adding series resistance will not raise the impedance of the driver. A driver's impedance varies with frequency and is altered by capacitive and inductive reactance over a broad range.
I would be careful with multiple drivers wired in parallel. You can toast the amp. Consult the ownwer's manual or manufacturer.
Tim
Tim,
read my post again, what I say is correct so I don´t know what you try to tell me? Most of what you say is what I have allready said..
Also you do not gain anything from surface area but from the extra magnets and the extras wires in that flux field (Bl product).
"*Most solid state amplifiers will not actually double current into lower impedance, but are assumed to. No change electrically with tube gear(4 drivers of 16 ohm impedance= 4ohm load with a yield from surface area gain only of 6 dB)."
Most good designs do... much **** on the market though. My amps double down to 2ohm from 8ohm. I tried to give the basics to the guys..
/Peter
read my post again, what I say is correct so I don´t know what you try to tell me?
Most of what you say is what I have allready said..Also you do not gain anything from surface area but from the extra magnets and the extras wires in that flux field (Bl product).
"*Most solid state amplifiers will not actually double current into lower impedance, but are assumed to. No change electrically with tube gear(4 drivers of 16 ohm impedance= 4ohm load with a yield from surface area gain only of 6 dB)."
Most good designs do... much **** on the market though. My amps double down to 2ohm from 8ohm. I tried to give the basics to the guys..
/Peter
Grandma´s_SUB said:
Well, yes. First, sensitivity is usually given at a voltage, typically 2,83 volts. This corresponds to 1 watt in a 8 ohm resistor, but since the impedance of a loudspeaker varies with frequency, the voltage convention works better.
So, if we assume that the speakers have a sensitivity of 87 dBSPL@1 m, 2.83 V, the following will happen:
Series connection: Each speaker will see half the voltage, and halving the voltage corresponds to -6 dB. On the other hand we now have two sound sources, and so their pressures add, which gives twice the pressure from each driver, or + 6 dB. The net sensitivity gain is 0 dB. Note, however that the input power is halved, since the impedance seen by the amplifier is half that of one driver (or -3 dB). In other words, the efficiency is doubled (but the sensitivity is the same). Sensitivity: 87 dB
Parallel connection: Each speaker sees the full voltage, so the input signal is the same if only one driver is connected. No level change because of this. But now we have two sound sources, and their pressures add up, and so the sound pressure doubles, or + 6 dB. Net sensitivity gain is + 6 dB. Note, however, that the input power is doubled (+ 3 dB) due to the halved electrical impedance, and so the efficiency gain is still +3 dB (doubled). Sensitivity: 93 dB.
If we go back to your drawing, and assume that the voltage of the amplifier is different in the two connections (series vs parallel) in order to really get a 1 watt power to each speaker, the net result is that the efficiency doubles in both cases. Since the sensitivity is usually defined at 2,83 volts, it makes little sense calulating the sensitivities based on your figure.
HTH
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