First, I see that the 97 db spec is for an input of 2.83 volts, at a distance of 1 meter, and that the speaker’s impedance is 4 ohms. If the speaker’s impedance was 8 ohms, that would correspond to 97 db for 1 watt at 1 meter. However, since 2.83 volts into 4 ohms corresponds to 2 watts, the speaker’s efficiency is 94 db/1 watt/1 meter. Although if the 100 wpc amp you mentioned starting with is solid state, and that rating is for an 8 ohm load, chances are it would be able to provide somewhere between 150 and 200 watts into 4 ohms.
Second, neglecting room reflections the SPL produced by a box-type dynamic speaker such as those will fall off at 6 db per doubling of distance, which equates to 20 times the logarithm (base 10) of the ratio of two distances. So at a listening distance of say 10 feet the SPL produced will be approximately 10 db (actually 9.68 db) less than at 1 meter, neglecting the effects of room reflections.
Third, two speakers will be in use, which will add 3 to 6 db to the maximum SPL produced by one of them. The 6 db figure would apply if the listener is equidistant from the two speakers, and they are both reproducing the same signal.
So for an amp capable of providing 200 watts (23 dbW) into 4 ohms, at a 10 foot distance the maximum SPL (neglecting room effects) would be:
94 + 6 + 23 - 10 = 113 db.
This assumes, btw, that the speakers are not being driven hard enough for a long enough amount of time for "thermal compression" to set in and reduce their efficiency to a significant degree.
If the amp is rated at say 150 watts into 4 ohms, the result would be about 1.25 db less than that, or 111.75 db.
As far as biamping and triamping are concerned, while it is possible to obtain good results using different amps, using identical amps will greatly reduce the chances of poor results, that may result for example from loss of coherence due to differences in their sonic characters. Also, with different amps a means of matching their gains would most likely be necessary.
Finally, regarding the possibility of using amps having significantly different power capabilities, if an electronic crossover is not used "ahead" of the amps chances are you would be limiting the maximum power capability that could be utilized from the highest powered amp to not a great deal more than the power capability of the lowest powered amp. That is because while passive biamping (i.e., biamping without an electronic crossover ahead of the amps) reduces the amount of current and power each amp must supply, all of the amps still have to output voltages corresponding to the full frequency range of the signal, and at equal levels if gains are properly matched. So turning the volume control up high enough to utilize most or all of the power capability of the highest powered amp would most likely cause one or both of the lower powered amps to exceed its maximum output voltage capability, and therefore to be driven into clipping.
Regards,
-- Al
Second, neglecting room reflections the SPL produced by a box-type dynamic speaker such as those will fall off at 6 db per doubling of distance, which equates to 20 times the logarithm (base 10) of the ratio of two distances. So at a listening distance of say 10 feet the SPL produced will be approximately 10 db (actually 9.68 db) less than at 1 meter, neglecting the effects of room reflections.
Third, two speakers will be in use, which will add 3 to 6 db to the maximum SPL produced by one of them. The 6 db figure would apply if the listener is equidistant from the two speakers, and they are both reproducing the same signal.
So for an amp capable of providing 200 watts (23 dbW) into 4 ohms, at a 10 foot distance the maximum SPL (neglecting room effects) would be:
94 + 6 + 23 - 10 = 113 db.
This assumes, btw, that the speakers are not being driven hard enough for a long enough amount of time for "thermal compression" to set in and reduce their efficiency to a significant degree.
If the amp is rated at say 150 watts into 4 ohms, the result would be about 1.25 db less than that, or 111.75 db.
As far as biamping and triamping are concerned, while it is possible to obtain good results using different amps, using identical amps will greatly reduce the chances of poor results, that may result for example from loss of coherence due to differences in their sonic characters. Also, with different amps a means of matching their gains would most likely be necessary.
Finally, regarding the possibility of using amps having significantly different power capabilities, if an electronic crossover is not used "ahead" of the amps chances are you would be limiting the maximum power capability that could be utilized from the highest powered amp to not a great deal more than the power capability of the lowest powered amp. That is because while passive biamping (i.e., biamping without an electronic crossover ahead of the amps) reduces the amount of current and power each amp must supply, all of the amps still have to output voltages corresponding to the full frequency range of the signal, and at equal levels if gains are properly matched. So turning the volume control up high enough to utilize most or all of the power capability of the highest powered amp would most likely cause one or both of the lower powered amps to exceed its maximum output voltage capability, and therefore to be driven into clipping.
Regards,
-- Al