FIR vs IIR vs Passive: The Truth About Crossovers

Added: 2026-05-09

[00:00:00]If you're a speaker builder and you're considering different types of crossovers, whether it's passive or active, this video is for you. I'm going to cover passive crossovers, active analog crossovers. We're going to take a look at digital IIR and linear phase FIR crossovers. And just like I used to think all coffees are the same, they are not the same. There's much better coffee out there. I dove deep into what coffee is, where it comes from, and to the point where now I roast my own coffee.

[00:00:32]Thank you, Dr. Werzbow. Um I enjoy the most amazing coffee every single day.

[00:00:38]And very similarly, I want to show you what FIR linear phase can do for you.

[00:00:44]So, let's dive right in. So, passive filters. Passive crossovers have been done for so many years. It's It's been 100 years, okay? Not much has changed since 1920s, 1930s, when they were invented.

[00:00:58]The good news is that we kind of know exactly what's going on with them. I mean, it's If you've got really good components, you're basically in the ballpark. You know, you could simulate them. You can use software to predict where you're going to be.

[00:01:13]They're very well understood.

[00:01:15]>> [snorts] >> With that said, implementation of them can take months or years. You're going to You're going to try different things, and chances are you're probably going to leave money on the table. Some of the best speakers, and when I say best, I'm talking about some of the most expensive. I shouldn't say best. I should say some of the most expensive speakers out there that cost tens of thousands of dollars, you're mostly paying not only for the parts and the assembly and the components, materials, you're paying for 6 months, a year out of the designer's life to build those crossovers. Sometimes they even sell the upgraded crossovers, okay? And these crossovers are basically somebody in there trying different capacitors, and trying to do the trade-offs and all this and that, and chances are you're still leaving money on the table cuz you can't do passive uh EQ per channel, you can't do passive time delay, you can't do linear phase. You're You're basically just stuck a century ago, okay? And it's it's got its place, and I commend the people that are doing it. Go for it.

[00:02:20]It's good education. Uh I'm not against them. Do your thing.

[00:02:24]But then you're thinking, "Okay, well, what is a What is a better way?"

[00:02:27]You might think, "Okay, then maybe I'll go with analog active systems."

[00:02:32]That might make sense to you. I thought so for a while about 10 years ago. I was like, "Oh, maybe I'll Maybe I'll do that." The problem is it's basically a fool's errand. And I I'm sorry if you make If you're a manufacturer of analog passive, you should look into digital signal processing. It's the frontier. Um it's a fool's errand because basically you Let me first say the good news. The good news is that you can AB faster. You can actually AB um It's It's a little more fun, too, cuz you You can swap in different capacitors and inductors right on the breadboard. It's a little more fun from that perspective. However, the biggest downside is that you can't I mean, you could So, if you have a digital source, you have a digital music, okay, from your streaming service, and you bring in this digital music, you have to bring it into the analog world to have your analog crossover. So, in that conversion, it's not ideal because you have really good dynamic You have to get that right.

[00:03:29]Let me just say. But you do have degradation in that realm. Now, if you have an analog signal coming in, like from a vinyl, and you get it into a digital system, that's fine, or you can make it fine. You can make it good if um you treat it well, and you can bring it in there. However, if you've got a digital signal already, you want to keep it digital. You want to keep it in the digital domain and do all the wonderful things DSP can do and amplify it, get it to analog the very last thing. The very, very last thing you want to get it into analog. So, there's that problem. Also, you can't add delay. It's very hard to add parametric EQ per channel. You could do it, but it adds a whole another level of complexity. Uh time delay, you need like a you need like a coil or these um crates, these bucket chips that it's a whole thing. You you don't want to do it. They're not very precise. So, you get this bloated board with all sorts of noise coming in there.

[00:04:29]Um even if you solve all that, it's still not ideal because if you have digital music coming in, you're kind of you're degrading it just to you might as well just go with with passive and then just do something else.

[00:04:41]But then you're thinking, "Okay, let's go digital. What can we do with digital? Okay, well, digital is could potentially be good, but not all DSPs are made the same. And I can't wait to get into this topic because over the years, we've done so much work, thousands, tens of thousands of hours of different disciplines to come up with a good DSP. Okay? So, when people talk about, "Why don't you just get a 1701 or whatever module for $20 and get some amps onto it?"

[00:05:12]No, okay? I can't wait to talk about it.

[00:05:15]So, let me just keep going. Let's pretend that all DSPs are the same for just this theoretical talk here.

[00:05:21]And let's just say that all DSPs are amazing, everything is solved as far as hardware, firmware, software, acoustics, everything is solved, and you can just control everything from an app. You can just control all the crossovers. Well, what you will get is the ability to do IIR filters. So, IIR is basically what analog filters do, and they mimic them really well, but you can go much steeper slope. And another really good thing about IIR is that you can essentially AB them really quickly.

[00:05:52]So, they load almost instantaneously and our ears can pick up on the differences on different AB comparisons and you'll be able to tell like do you want to cross over at 800 hertz, 1,000, 2,000?

[00:06:05]You can pick up on that really quickly.

[00:06:08]And do measurements real quick and switch real quick. So, there's a big plus to the IIR. You can do parametric EQ per channel. You can do time delay.

[00:06:17]There's a lot of things you can do when you go digital if your signal is digital or you have a really good analog to digital for like vinyl and things you bring it into that world. Everything is theoretical up until you get it to a really nice DAC or you go DAC-less.

[00:06:32]That's also an opportunity. But basically you keep everything digital, you keep theoretical, you keep everything theoretical all the way up until the very last second so you don't pick up noise.

[00:06:42]Noise is a whole thing. So, you keep everything digital.

[00:06:45]You keep everything ideal until you do the the very last to analog conversion.

[00:06:50]But let me get to the the star of the show and that is FIR. With FIR, what happens is you use these taps, okay? So, each channel has so many taps and those taps you can use to kind of look ahead and create a symmetric impulse response.

[00:07:08]This is what IIR impulse response looks like. So, there's the impulse and then there's some ringing. Here you have symmetric ringing before and after. So, basically what that translates to uh first of all, the number one most important thing is that the phase is zero. Nothing changes with the phase.

[00:07:27]So, all frequencies arrive at the same time. All frequencies are passed to the driver at the same time. There's no phase change specifically at those frequencies. And there's a beautiful discussion going on in the um audio community right now, which one actually sounds better and this and that. Well, I'll tell you my opinion, 100% linear phase sounds better, especially if you have a steep slope, you cross them over from mid to high really really really steep slope, and you've got linear phase, your speaker is very good linear basically at that moment, you get such transparency. You get such transparency. So, I'm on the camp of FIR linear phase is the way to go. Um there are people that do like this kind of ringing, but that's fine.

[00:08:20]You can still do FIR with minimum phase.

[00:08:24]You can go to um rephase, create a minimum phase crossover, and bring it in, and you can still have this kind of a sound with minimum phase, and you're you're basically back to here, so you could do that. I prefer, which I think you will too, and you can try these things. The best thing about a DSP is you can try them. Certain speakers will sound better with just linear phase FIR, some will sound better with minimum phase FIR, but you can check and test from A to B to C. You can try different things and hear and measure.

[00:09:03]In my uh studies, in my measurements, in my understanding of everything, linear phase is the way to go, especially if you have like beryllium tweeters, you have really nice tweeters, you have really nice doesn't have to be beryllium, it could be you know, just really nice tweeters to mids, linear phase is really really good as far as what I what I notice is is the guitar, the acoustic guitar, when you pluck it with your fingers, you can hear that pluck, you can hear that dynamic, that the transients are really, really good.

[00:09:39]So, this is where I think linear phase shines absolutely the most. Here's the the part that you have to take into consideration.

[00:09:47]First of all, not all DSPs are made the same. Not all algorithms are made the same. And the most important part, the drivers themselves are not all made the same. If your driver has a ton of issues, if your driver has non-linear activity, if your driver if you measure it and it's got all sorts of phase issues without any crossover, you just run 20 to 20 kHz or whatever sweep and you've got phase phase everywhere. It's like saying you know, you've got a canvas, a beautiful canvas that's got a ton of paint on it all so just smeared all over and you add a line or you subtract a line, no one can tell cuz it's just a mess.

[00:10:27]Now, if you've got a linear driver in the passband where you're working and you've got a clean clear canvas, adding a line or subtracting a line will make a difference, especially at the crossover. Okay? And also the FIR situation, you can bring in different FIR filters from different programs or in certain programs they will already build in these uh Oh gosh, battery's dying. All right, real quick. You can bring in different um algorithms, uh different slopes for your crossover. You can change, you can mess with the phase in a way where you can try to correct the phase using like rephase and things like that. But some of these programs have advanced crossovers, advanced phase correction.

[00:11:18]You can take it to a completely new level. So, if you've got a really nice driver, if you already invested money in a really nice driver and you've got a measurement microphone, you could do amazing things and you will hear a difference.

[00:11:29]Okay?

[00:11:31]I can't wait to get into the weeds of why not all crossovers are made the same.

[00:11:37]But for now, let me just say this.

[00:11:39]Linear phase is where the phase is linear. At the point of crossover, there's no phase change, okay?

[00:11:46]Now, you could use something called the linearizer to take an IIR filter and linearize it using FIR to make it just like this. You could do that.

[00:11:56]But you could also just go straight with FIR and at the moment of the crossover, you can have steep slope, you can have shallow slope, but the phase is going to be linear with FIR. It delays the entire signal and it basically it it gives you no change at the moment of the crossover.

[00:12:18]That basically summarizes this video, but if you want to know the differences between the crossovers, what makes certain crossovers better versus others, if you want to know more about what makes a DSP good or bad and how we built the DSPs and how people implement DSPs, watch this next video. Should be somewhere here. It should be live by now. If it's not, subscribe and it'll be live soon. Thank you for watching.

[00:12:43]There's quite a bit more that I could cover, but this is the main thing. FIR is the future. It is the present. It will change the imaging game for you if you have really good drivers and a good DSP. Okay, talk to you soon.

[00:13:00]Leave your comments. Talk to you soon.

[00:13:01]Bye.