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Multi-Way Conventional loudspeakers with crossovers

BEGINNER!!  Need help understanding Crossover/Impedance/Wattage
BEGINNER!!  Need help understanding Crossover/Impedance/Wattage
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Old 21st January 2018, 06:15 PM   #21
Fast Eddie D is offline Fast Eddie D  United States
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Join Date: May 2010
Location: Skokie Il
About every three weeks, we get a new thread with the exact same misguided questions.

I do not blame the people who join and ask the questions. I blame the hucksters that market audio equipment. They have succeeded with totally bamboozling the public on topics like power, watts, frequency response, etc. Never mind what engineers have to say on the topic!

Quote:
Originally Posted by Gnobuddy View Post
Wattage (power) is usually measured with a sine wave test signal, at one single frequency. The amount of power delivered to the speakers is determined by the amplifier and speaker. An ideal crossover has no losses, and will have no effect on power delivered to the speaker - as long as the sine wave is within the frequency range that the crossover lets through itself.

Real crossovers have some small amount of power loss, because of the resistance of the inductor. So they will slightly lower the amount of power delivered to the speaker.

Things are different if you are talking about music, rather than a sine test tone. If music is played through the speaker, then the crossover divides up some frequencies to send to the woofer, and some to send to the tweeter. If you measure average power, usually most of the power ends up going to the woofer, and very little to the tweeter. But there may be very short bursts of higher power levels to the tweeter.

Since most of the power goes to the woofer, you can think of the system as still having only 40W of power handling capability.

I should add that the "40 W" number may be optimistic - some manufacturers inflate their power ratings to make the advertisement look more tempting. I have seen "25 W" speakers that would burn up or fall apart if you fed them even 10 watts.


15W and 40W are not the actual power delivered to the speaker - they are only a manufacturers specification for the maximum amount of power that speaker can handle without damage.

The actual amount of power delivered depends on the amplifier (how many volts is it putting out?), and speaker impedance. That may be only 0.1 watt, or it may be 1 watt, or it may be 10 watts, or anything in between.

An analogy: if your car has a 15 gallon gas tank, that doesn't mean you have 15 gallons of gas in it. You may only have 5!


Forget all about that 55W, it is confusing the heck out of you.

The power you need is whatever is enough to play music at the loudness you want.

The speaker power handling needs to be able to cope with this. Hopefully, you are satisfied with the volume level before you get to 40 watts.


A small amount of power is wasted in the resistance of the coils in the crossover network. This power heats up the coils, and also creates a magnetic field in the iron core (you can see the core in the Amazon.com photos you linked to.)

The 150W rating of the crossover means that the coil will survive the amount of heat, and magnetic field, that will be created if you pump 150 watts of music through that crossover, from amplifier to speaker.


First, I'm going to give you the super-simplified version: the crossover has no effect on impedance. If you have two 8 ohm speakers, your combined (crossover + woofer + tweeter) is still an 8 ohm system.

In reality, the question you asked is a big can of worms to open. The crossover network you bought from Amazon will work perfectly if loudspeakers were resistors, but they are not. Real speakers have big peaks and dips in their own impedance at different frequencies, and this "confuses" the crossover network, which ends up presenting even bigger peaks and dips in impedance to the amplifier. Real tweeters and woofers also have very different characteristics from each other (dispersion at the crossover frequency, sensitivity, time response), and a good crossover network has to take all that into account.

Real crossover networks in good loudspeaker systems are far more complex than the ones you can buy from Amazon or Parts Express. Designing them is part engineering, and part art. It is a very complicated thing to do correctly, and needs a lot of knowledge, a lot of expensive equipment, and an even more expensive anechoic chamber in which to do the measurements. Because of this, the vast majority of DIY loudspeakers don't get crossovers right.

But the wonderful thing about loudspeakers is that, however bad the crossover, enclosure, or drivers, some sort of sound will come out of them. This is enough to make many DIY speaker builders happy!

-Gnobuddy
Should be stickied!
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Old 21st January 2018, 06:48 PM   #22
Fast Eddie D is offline Fast Eddie D  United States
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Join Date: May 2010
Location: Skokie Il
Quote:
Originally Posted by Gnobuddy View Post
There are a few weird Bose car audio systems that use very low speaker impedances (around 1 or 2 ohms) in order to deliver more power with the same 12V supply rail, but that is an oddball that, thankfully, was not followed by anyone else in the automotive audio industry.

-Gnobuddy
Actually, oddball speaker impedances are the norm in consumer oriented integrated devices. This includes mobile applications.

My Subaru had a powered "subwoofer" under the seat. The "subwoofer" driver was rated 1.6 ohms, stamped right on the frame. The amplifier was a cheap and dirty digital amplifier.

Another Subaru had a 6.5" "subwoofer" mounted in the rear deck. It disintegrated (big surprise) and I was charged with fixing it. As far as I could tell it was a 1 ohm subwoofer. I ordered a cheap dual voice coil "2+2 ohm" subwoofer and wired the voice coils in parallel. It blew the original subwoofer away and only cost around $20.

My buddy's Navigator had a 1.6 ohm subwoofer that was blown. We put a box in the back with two 4 ohm subs wired in parallel. The cheapo OEM digital amplifier does a nice job of driving them.

Integrated home systems (cheapo tabletop stereos) often have 3 ohm speakers.

This stuff is not designed to be mixed and matched any more. You buy it, use it until something goes wrong, then you buy another cheap and crappy system. That's the market now.
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Old 21st January 2018, 08:04 PM   #23
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by Fast Eddie D View Post
This stuff is not designed to be mixed and matched any more. You buy it, use it until something goes wrong, then you buy another cheap and crappy system. That's the market now.
Unfortunately, I think you are dead on the money.

And I thought 6-ohm speakers ("Our CrappMaxPlus speakers will work with all 4 and 8 ohm systems!") were bad enough!

-Gnobuddy
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Old 21st January 2018, 08:14 PM   #24
Fast Eddie D is offline Fast Eddie D  United States
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Join Date: May 2010
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Quote:
Originally Posted by Gnobuddy View Post
Unfortunately, I think you are dead on the money.

And I thought 6-ohm speakers ("Our CrappMaxPlus speakers will work with all 4 and 8 ohm systems!") were bad enough!

-Gnobuddy
I have a rant about "4-8 ohm" speakers somewhere in the forum. "4-8- ohm" = 4 ohm. "6 ohm" = 3-4 ohm. I've done the measurements.

Some popular speakers make great demands from amplifiers to only produce modest performance. These popular speakers sound thin and weak unless driven by an amplifier with generous current reserve. That's what makes them "high end" .
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Old 22nd January 2018, 07:46 PM   #25
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by Old'n'Cranky View Post
<snip>
...'wattage'...
<snip>
...'amperage'...
<snip>
...butchered words...
<snip>
I was thinking about Old'n'Cranky's comments, and I wonder if this is partly a disconnect between old imperial units, and more contemporary metric units.

In American and British English, it seems to be common to use "acre" as a unit of land area, and "acreage" to describe a piece of land. In the same way, distance is measured in miles, and people speak of the "gas mileage" their car gets.

We also have feet and footage ("...a property with 150 feet of waterfront footage..."). "Yardage" is quite commonly used too, and is listed in several online dictionaries I checked.

A number of online dictionaries also list "poundage" as a description of weight, and of course, "tonnage" has been used for centuries to describe the freight carrying ability of ships, and more recently, trains and trucks.

You can count on Imperial units being inconsistent, so it's no surprise that nobody uses "inchage" or "fathomage" or "yearage".

In the world of metric units, on the other hand, you never hear of "millimetreage" or "meterage" or "grammage" or "kilogramage".

But all my life, I have heard "voltage" and "wattage" being used by educated people - in countries still using imperial units. Maybe that's a hangover from their being used to adding "age" to various imperial units?

Just a thought.

And I close with an example of how to use the best word in this entire thread: "How much milkerage do you get from your cow?"

-Gnobuddy
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Old 23rd January 2018, 09:49 AM   #26
AllenB is online now AllenB  Australia
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Join Date: Oct 2008
Rather than imperial, I'd say there is a relation to industries. The words are jargon, and where they are used there is a disconnect from the normal usage. The automotive industry uses 'condensor', legitimate but archaic. The same disconnect sometimes applies to amateurs
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Old 23rd January 2018, 07:45 PM   #27
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by AllenB View Post
The automotive industry uses 'condensor', legitimate but archaic.
...and they use "condensor" to mean different things: it's used to mean the capacitor in an old-fashioned ignition system, and also used to describe the little radiator that cools off the high-pressure refrigerant coming from the compressor in the air-conditioning subsystem, turning it back into liquid.

Quote:
Originally Posted by AllenB View Post
The same disconnect sometimes applies to amateurs
I'm technically an amateur at most things I do. Quite possibly a disconnected one as well.

-Gnobuddy
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Old 27th March 2018, 07:27 AM   #28
MBA is offline MBA  Czech Republic
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Quote:
Originally Posted by Gnobuddy View Post
...In the world of metric units, on the other hand, you never hear of "millimetreage" or "meterage" or "grammage" or "kilogramage".
Grammage is actually commonly used in food industry or retail in continental Europe, the same for meterage ;-)

Last edited by MBA; 27th March 2018 at 07:40 AM.
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Old 28th March 2018, 05:33 PM   #29
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by MBA View Post
Grammage is actually commonly used in food industry or retail in continental Europe, the same for meterage ;-)
You have got to be kidding me!

-Gnobuddy
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Old 28th November 2019, 02:31 PM   #30
Allan M is online now Allan M
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Join Date: Nov 2019
Quote:
Originally Posted by Gnobuddy View Post
I should add that the "40 W" number may be optimistic - some manufacturers inflate their power ratings to make the advertisement look more tempting. I have seen "25 W" speakers that would burn up or fall apart if you fed them even 10 watts.

15W and 40W are not the actual power delivered to the speaker - they are only a manufacturers specification for the maximum amount of power that speaker can handle without damage.
The speaker power rating figure is the maximum continuous power rating (i.e. for a 1 kHz sine-wave input) of the amplifier they can handle music and speech signals from at maximum level before clipping. E.g. 100 W rated speakers can't handle 100 W continuous power, they can handle music and speech signals at maximum level before clipping from an amplifier rated for 100 W continuous power. Music and speech have much lower average power than a continuous sine-wave of the same peak level, since the peaks are far less frequent. The continuous power the speakers can handle will be far less than 100 W.

Quote:
Forget all about that 55W, it is confusing the heck out of you.

The power you need is whatever is enough to play music at the loudness you want.

The speaker power handling needs to be able to cope with this. Hopefully, you are satisfied with the volume level before you get to 40 watts.
Still, the maximum sound level the speakers are capable of producing, the less they will distort the sound at lower levels. The sound quality will still be improved even if they are not used near the maximum level they can handle without burning out.

Quote:
In reality, the question you asked is a big can of worms to open. The crossover network you bought from Amazon will work perfectly if loudspeakers were resistors, but they are not. Real speakers have big peaks and dips in their own impedance at different frequencies, and this "confuses" the crossover network, which ends up presenting even bigger peaks and dips in impedance to the amplifier. Real tweeters and woofers also have very different characteristics from each other (dispersion at the crossover frequency, sensitivity, time response), and a good crossover network has to take all that into account.

Real crossover networks in good loudspeaker systems are far more complex than the ones you can buy from Amazon or Parts Express. Designing them is part engineering, and part art. It is a very complicated thing to do correctly, and needs a lot of knowledge, a lot of expensive equipment, and an even more expensive anechoic chamber in which to do the measurements. Because of this, the vast majority of DIY loudspeakers don't get crossovers right.
What kind of complexity is required, aside from compensation for speaker response dips and peaks and the speaker impedance variations at different frequencies, speaker efficiency differences (which basic, ready-made crossovers don't have)?
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