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Speaker Sensitivity Question...

I was doing the calculation for desired output of a speaker at a distance and the total watts that would be required to get you there. The 1 watt at 1 meter to efficiency to the speakers in db one.

The calculation adjust for the distance of your listening position as a variable.

But what about when you crossover the speakers to a dedicated subwoofer? Isn't the lower frequencies where the majority of you amp wattage gets used up?

So it would stand to reason if you eliminate the lower frequencies from your speaker (from crossing them over to a dedicated sub) that would "free up" those watts and your speakers would not need as many watts to play a desired level.

Is there a calculation for this adjustment?
Am I wrong in assuming this?

Thank you,
Bill
baranowski

Showing 1 response by almarg

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almarg
9,670 posts
 
For most music most of the time, a considerable majority of the power that is required will be required at frequencies greater than the crossover frequency that is likely to be used with a powered sub, e.g., 40 or 50 or 60 Hz or thereabouts. (I'm assuming you are referring to a powered sub). As a rough approximation, I believe that 300 Hz is a frequency at which equal amounts of power will often be required at higher and lower frequencies. So in typical circumstances I wouldn't count on a significant reduction of the amplifier power requirement as a result of using a powered sub, crossed over or not.

Also, if the crossover function is being performed "after" the power amplifier, as would be the case if it is performed by the sub itself (with the power amp being connected to the sub, and a high pass filtered output of the sub being connected to the main speakers), the power amp will still have to output a voltage range corresponding to the full frequency range of the signal. So if you were to go to a lower powered amp based on the expectation that it would not have to supply as much power as the full range signal would otherwise require, you still might find yourself clipping the amp if its voltage swing capability is less than what a higher powered amp might be capable of.

ZD makes good points as well. Regards,
-- Al
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