Passive crossover power usage

It really depends. Get a hold of XSim crossover simulator or other such device.

The big power wasters isn’t the frequency filters but the equalizer and amplitude leveling resistors.

Look at it this way. Almost all multi-way speaker systems use drivers with drivers that don’t exactly have the same sensitivity to the amp signal. That is, for the same signal a tweeter may be at 96 dB but the woofer at 88 dB.

The only way to equalize these is to "pad" the tweeter level down so it’s at the same relative output given the same amp input. That’s where the power wasting is mostly concentrated, but Zobel, notch filters, baffle step, impedance compensation, etc. can also waste power as heat. This is also why you see such large cement resistors in crossovers. 5W resistors are typical, while 25W resistors are also possible. That’s all wasted heat.  BTW, resistors are not the only place where power waste can occur, but they are the most obvious.

This is one area where active crossovers are undeniably better. Amplitude matching in the signal domain takes microwatts.

Thanks @erik_squires .  That's why I ripped the crossovers out of my speakers and use a Marchand 3-way electronic crossover and four amps to run my speakers. Two mono blocks for the woofers and two stereo amps for the mids and highs.

A lot more control and after I got over the tendency to catalog crossover level settings by "album" it is very nice.

Regards,

barts

  That's why I ripped the crossovers out of my speakers and use a Marchand 3-way electronic crossover and four amps to run my speakers.

So you knew the answer already and I wasted my time?

There is some power dissipated in the crossover and it depends on what level you are running your amp.  I'm a flea watt guy and there i almost no heat generated. But I built my new crossovers with 10 to 30 watt resistors so they won't blow if someone hooks a zillion watt amp up to them.  Remember for 10dB increase in volume, you need 10x the power.  So if a teenager has a party you could blow the crossover...there are actually stories on the internet about this.

I don't like electronic crossovers.  I hate processing the signal any more than I have to.  Many readers have no such feelings. They use equalizers, ss preamp, ss amps, etc and the signal goes throught a million components before it gets to the speaker....so to each his own.

Jerry

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.

@erik_squires 

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.

Regards,

barts

@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. 

@carlsbad2 

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.

Regards,

barts

Barts:

IMHO, the best, simplifying solution right now for active speaker making is to use a plate amp with built in DSP. These are available from Madisound, Parts Express and miniDSP.

They come with 2 or 3 output channels. The benefits are mulitple, including not having to have 3 amps and an explosion of cables coming in and out of them, but also better frequency response tailoring than you get in an analog crossover.

I am currently working on a 3-way center channel and the features of a Hypex 3-way amp/crossover is really outstanding.

@jaytor

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.

That’s not a negative!! 🤣 The DCR (DC resistance) of an inductor can be effectively used as part of a circuit, especially a baffle-step compensation. Your average inductor has fabulous power dissipation capabilities (100W or more) so it’s a really good design choice when given a chance of using a low DCR coil and a big R or high DCR coil and no R I’ll take the latter.

So, don’t go willy-nilly reducing the DCR in a crossover unless you have measured what you are doing. In the even-ordered filter stages you would have to compensate for any missing R to ground with an additional R value.

This is where a crossover simulator like XSim or other can really help, as you can evaluate changing DCR in the frequency and impedance domain at the same time.  Small changes in even ordered filter stages can have big implications in the minimum impedance.

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.

Well, it's true but usually in the home we don't care very much.  We run 10W or less most of the time. :D

It's in pro applications where power is at a premium where this becomes a big deal.

Awesome answers from Erik.  Learned alot as I usually do from your posts.  Thank you and I hope you don’t leave the forum out of frustration like the other guy (name starts with an “s”) 

Thanks @yodogyodog  - I have survived George Hifi, Miller, Kenjit and the swarm, so I think I can live through the bottiness.