I don't understand the difference between the two. Some manufacturers say their crossover topology is 1st order, but it actually is electrical 1st order but not acoustic. What's the difference? Does the electrical crossover not have a 6db slope? How does relate to phase?
Thanks for any help that can shed light on this.
Thanks for any help that can shed light on this.
We hear the response like you can measure with a microphone. Drivers don't have a flat response, so that gets added to the filter... For this reason the filter response is not heard by itself so it doesn't count when talking theoretically about how it should sound.
Alexnova, your question is most likely about the difference between electrical and acoustic response. In fact an acoustic crossover is something different again, such as putting a tissue in front of the speaker to cut the highs. This can be seen used on different levels.
Alexnova, your question is most likely about the difference between electrical and acoustic response. In fact an acoustic crossover is something different again, such as putting a tissue in front of the speaker to cut the highs. This can be seen used on different levels.
Not an expert by any means but this is my simple understanding but happy to be corrected.
We hear acoustic slopes and this is what is measured at the microphone.
Speaker drivers have natural roll off of sound (sound gets quieter) at their extremes e.g. Woofers roll off at higher frequencies (and low), tweeters do the opposite and roll off (or roll on maybe) at lower frequencies, and mid drivers do low and high roll off. This roll off has a slope that decays at a certain db/octave.
The electrical components in a crossover also induce roll off of the driver frequency output and again are classified by order 1st, 2nd etc. depending on the component arrangement (lots of info if you google).
Therefore, the crossovers components adds an electrical slope to the natural roll off slope giving an overall acoustic slope I.e. crossover electrical plus driver natural equals acoustic.
Typically the slopes are described by 1st, 2nd etc order which correspond to for 6dB/octave increments in slope I,e. 1st order is 6dB/octave, 2nd order is 12dB/octave etc.
So you may have a driver that naturally rolls off at 6dB/octave, add a 1st order electrical low pass crossover and the Sum is a 2nd order acoustic slope.
Not sure if this helps but my 2p worth.
We hear acoustic slopes and this is what is measured at the microphone.
Speaker drivers have natural roll off of sound (sound gets quieter) at their extremes e.g. Woofers roll off at higher frequencies (and low), tweeters do the opposite and roll off (or roll on maybe) at lower frequencies, and mid drivers do low and high roll off. This roll off has a slope that decays at a certain db/octave.
The electrical components in a crossover also induce roll off of the driver frequency output and again are classified by order 1st, 2nd etc. depending on the component arrangement (lots of info if you google).
Therefore, the crossovers components adds an electrical slope to the natural roll off slope giving an overall acoustic slope I.e. crossover electrical plus driver natural equals acoustic.
Typically the slopes are described by 1st, 2nd etc order which correspond to for 6dB/octave increments in slope I,e. 1st order is 6dB/octave, 2nd order is 12dB/octave etc.
So you may have a driver that naturally rolls off at 6dB/octave, add a 1st order electrical low pass crossover and the Sum is a 2nd order acoustic slope.
Not sure if this helps but my 2p worth.
An electrical crossover uses active or passive filters to restrict the frequencies reproduced by each driver in the system to its intended range.
An acoustic one, on the other hand, relies on the natural roll-off of driver responses (due to voice coil inductance, cabinet cutoff, cone mass etc.) to reproduce the appropriate frequencies from each driver in the system.
All the best.
Mostly the answers above are correct. You can think of the the electrical crossover as the "input" to the speaker, and the acoustic crossover the "output" from the speaker. The input signal combines with the responses of the drivers themselves to produce the output. When the crossover point is near the driver's own resonance where its rolloff occurs at the low end of the passband, the drivers' rolloff should be taken into account when designing the crossover for the loudspeaker. This is because the driver's phase response will be changing just like if it was another (second or third order order) highpass filter stage.
As AllenB stated ... drivers have a natural, acoustic, roll off. When an electrical filter network is applied (as a crossover target) it interacts with the drivers natural acoustic roll off. The interaction yields a new acoustic roll off for the driver, hopefully at the target frequency.
The shape of the slopes are manipulated by the components of the electrical network you use.
I've noticed that the farther you are away from the drivers acoustic roll off, the electrical network doesn't interact as much with the natural acoustic response of the driver. In other words, the electrical network takes full control of the drivers acoustic response.
The shape of the slopes are manipulated by the components of the electrical network you use.
I've noticed that the farther you are away from the drivers acoustic roll off, the electrical network doesn't interact as much with the natural acoustic response of the driver. In other words, the electrical network takes full control of the drivers acoustic response.
I always looked at the acoustical crossover as the sum of the drivers natural roll off plus the electrical roll off caused by the crossover network. With a horn it would be the roll off caused by the LF cutoff.
Rob 🙂
Rob 🙂
the electric filter is the theoretical result if that filter was applied to an "ideal" speaker with perfectly flat frequency response and perfectly flat resistance at all frequencies. The acoustic filter is the actual rolloff of the driver.
It's easier to understand if you look at an electric filter when it's applied to something other than a speaker. If you calculate the cap & inductor values required for a 2nd order filter in an amplifier circuit where you'd apply the filter on the input side of a transistor, then the calculated values will give you exactly what you expect because the input of that transistor is a consistent resistance across all frequencies, and the frequency response of that transistor is completely flat.
But, a speaker is much more complex because it's got it's own frequency response that's anything but flat, and it also has a resistance that changes with frequency, which will impact how that filter interacts with it. Let's look at the same 2nd order electrical filter mentioned in the amplifier example, but now we calculate it to work with an "8" ohm woofer. That "8" ohm woofer actually has a resistance that rises with frequency, and it's also got it's own rolloff as frequencies increase. The combined acoustic rolloff will be the result of the driver's natural rolloff, and the non-ideal rolloff created by the interraction of the selected components with the driver's own fairly complex electrical properties. This is why "ideal" crossovers almost never work the way you'd expect, and it's important to model any potential filters in some sort of crossover design software. I like Jeff Bagby's Passive Crossover Designer because it's highly accurate, it's fairly easy to work with, and it's free.
It's easier to understand if you look at an electric filter when it's applied to something other than a speaker. If you calculate the cap & inductor values required for a 2nd order filter in an amplifier circuit where you'd apply the filter on the input side of a transistor, then the calculated values will give you exactly what you expect because the input of that transistor is a consistent resistance across all frequencies, and the frequency response of that transistor is completely flat.
But, a speaker is much more complex because it's got it's own frequency response that's anything but flat, and it also has a resistance that changes with frequency, which will impact how that filter interacts with it. Let's look at the same 2nd order electrical filter mentioned in the amplifier example, but now we calculate it to work with an "8" ohm woofer. That "8" ohm woofer actually has a resistance that rises with frequency, and it's also got it's own rolloff as frequencies increase. The combined acoustic rolloff will be the result of the driver's natural rolloff, and the non-ideal rolloff created by the interraction of the selected components with the driver's own fairly complex electrical properties. This is why "ideal" crossovers almost never work the way you'd expect, and it's important to model any potential filters in some sort of crossover design software. I like Jeff Bagby's Passive Crossover Designer because it's highly accurate, it's fairly easy to work with, and it's free.