Passive crossover power usage

The last thread about crossovers (good and bad or as is and rebuilt with better components) got me thinking about the power required in watts to run it. Actually heat dissipated by the crossover itself.  Seems to me it must be minimal if some of you guys a running systems with crossovers and are using 2-5 watt flea power amps on efficient speakers.  Any ideas?  Thanks.


High-sensitivity loudspeakers in general have relatively simple (few parts) crossovers. Low-sensitivity designs are often of low sensitivity because the crossover uses resistors to reduce the sensitivity of one driver (usually the tweeter) to match the output of a higher-sensitivity driver, thereby sacrificing overall loudspeaker sensitivity in the pursuit of flat frequency response. Such designs therefore require more power to reach a given SPL, some power dissipated as heat by the resistors in the x/o.

But there are some low-sensitivity loudspeakers---planar-magnetics in particular---which have very simple crossovers. The Eminent Technology LFT-8b, for instance, has simple 1st-order high-pass and low-pass filters (requiring only a few parts to implement), yet is a very low 84dB in sensitivity. Maggies too have relatively simple crossovers, yet require gobs of current. So it is not necessarily the crossover which is "eating" power.

Oops: should read "to match the output of a lower-sensitivity driver", not a higher-sensitivity one.


I'm sorry you feel as though I wasted your time.  No, I didn't know the answer at all.

Earlier that same day I was at a buddies house and we were discussing the possibility of me purchasing different speakers.  The reason being I'll be seventy soon and would like to simplify my system. No one in my family wants it or even has the space for it.  A common problem I understand.  

My buddy is of the opinion that anything I do would not be satisfactory compared to what I have now (which I'm very satisfied with).  He then went on a tirade about crossovers and how much power they suck up.  Asked me why would I want to go back to that.

So, I was simply asking the forum if anyone knew, that is all.



@erik_squires  pretty much covered it. The other parts that can dissipate power are inductors, particularly those wound with very thin wire like you often see in less expensive (and some pricier) speakers. 


I agree with your point concerning "less processing is better".  The reason I went with an electronic crossover is the control I get from the ability to alter the input level to each set of speakers in the box.

I would say the biggest benefit of that is the mids and highs have no idea what the woofer is doing and they don't care.  So, everybody plays nice. 

You're right to each their own.