Crossover confusion/questions

[Hi Ho]

I was just toying with the idea of building a pair of speakers for my PC and I was playing around with the Passive Crossover Designer. Since I can't find a .frd file for either the woofer or tweeter (Dayton RS100T-8 and Dayton DC28FT-8) I was simply playing with the crossover calculator section.

I chose a crossover frequency of 2,200Hz based on the frequency response of the tweeter and woofer.



I'm confused about the high and lowpass layouts. I was going by the 3rd order Butterworth series calculation (just a random pick) and it shows L1, C1, and L2 in the high pass section but the layout only shows those in the low pass section.

I am a complete noob when it comes to this. Could anyone shed any light on this?

Thanks.

 

[TLS Guy]

I was just toying with the idea of building a pair of speakers for my PC and I was playing around with the Passive Crossover Designer. Since I can't find a .frd file for either the woofer or tweeter (Dayton RS100T-8 and Dayton DC28FT-8) I was simply playing with the crossover calculator section.

I chose a crossover frequency of 2,200Hz based on the frequency response of the tweeter and woofer.



I'm confused about the high and lowpass layouts. I was going by the 3rd order Butterworth series calculation (just a random pick) and it shows L1, C1, and L2 in the high pass section but the layout only shows those in the low pass section.

I am a complete noob when it comes to this. Could anyone shed any light on this?

Thanks.

They are both fourth order high and low pass, with 5 resonant circuits added, Heaven knows why. Looks like a mess and I never saw the like of it.

 

[Hi Ho]

Haha well I figured as much. Any suggestions on good resources for learning how/why crossovers work so maybe I could make some sense of them? I have no idea what I'm looking at when I look at a crossover schematic.

 

[TLS Guy]

Haha well I figured as much. Any suggestions on good resources for learning how/why crossovers work so maybe I could make some sense of them? I have no idea what I'm looking at when I look at a crossover schematic.

A couple of recommendations for you.

Amazon.com: Loudspeaker Design Cookbook (9781882580101): Vance Dickason: Books

Amazon.com: Advanced Speaker Designs for the Hobbyist & Technician (9780790610702): J. B. Hall, Ray Alden: Books

 

[Hi Ho]

Thanks for the suggestions! I will look into those but they seem to be a bit over my head at the moment.

I did find some interesting reads via a simple Google search.

Lenard Audio Institute - Education - Greetings and introduction.

Passive Crossover Network Design

I've been reading through a lot of the content on those sites and I'm starting to understand some of the fundamentals.

An interesting topic is raised regarding active vs. passive crossovers. Active speakers are commonplace in the professional PA world. Why are they virtually unheard of in the home theater/audio world? Doesn't an active crossover/speaker design offer many benefits over a passive design including better efficiency and accuracy? Why don't we see any active home theater speakers? What are your thoughts on using active monitors like the KRK Rokit 5 or 6's in a home theater environment?

I also have a question about the crossovers in my current speakers that you helped me with. If I wanted to bi-amp the speakers would it be possible for me to simply separate the leads that go to the high and low section of the crossover and connect them to two separate amps or is there more to it than that? Also, what is the role of the resistors that shunt both the tweeter and the woofer?

Here is the final schematic:

 

[GranteedEV]

Active speakers are commonplace in the professional PA world. Why are they virtually unheard of in the home theater/audio world?

Because some people think amps make sounds, so they want to use their favorite amp, but that amp costs more than the speaker, so two would be expensive. Including the amps in the speaker will raise costs of course.

Doesn't an active crossover/speaker design offer many benefits over a passive design including better efficiency and accuracy?

The efficiency advantage is mostly negligible.
The accuracy advantage is arguable.

In theory active is better. For a lower crossover frequency, it certainly make sense. But sometimes the theory and the execution don't agree. there's definitely a case to be made that even though it should sound better/different, it doesn't under controlled listening conditions.

Why don't we see any active home theater speakers?

Well.. we actually do.... Seaton, Procella, Linkwitz, Genelec, being a few examples.

If I wanted to bi-amp the speakers would it be possible for me to simply separate the leads that go to the high and low section of the crossover and connect them to two separate amps or is there more to it than that?

That's passive bi-amping. we get that question every other day. Just the other day I addressed it:
http://forums.audioholics.com/forums/883668-post4.html

 

[Hi Ho]

Thank you for your response. I realize that passively bi-amping provides questionable/negligible benefits in the real world but I was simply trying to understand how the crossover network works and if it's as simple as wiring the high and low pass filters to two different amps. I wasn't planning on actually doing it as I am very happy with the performance of my system and don't feel I would benefit from bi-amping.

I know Genelec in a professional monitoring sense. I didn't realize the made speakers for home theater. I have not heard of the other brands.

 

[BoredSysAdmin]

Hi Ho,
I know you built your DIY mains - I assume on existing plans.
So you should know designing a good speaker is somewhat an art...

My 2c - just use existing design, Zath's, Curt's or one many others on PE and you wont go wrong

 

[Swerd]

An interesting topic is raised regarding active vs. passive crossovers. Active speakers are commonplace in the professional PA world. Why are they virtually unheard of in the home theater/audio world? Doesn't an active crossover/speaker design offer many benefits over a passive design including better efficiency and accuracy? Why don't we see any active home theater speakers?

As mentioned above, although there are a few speakers with active crossovers, most manufacturers are, for the present, sticking with the standard layout of speakers with passive speaker-level crossovers, and receivers (or amps) designed to drive speakers with one amplification channel. I think the real reason they don't adapt the pro layout is their fear that too many owners would burn out their woofers and tweeters. Users already seem to have enough trouble understanding how to set up their subwoofers. Automated smart software systems for general crossovers, similar to today's bass management software, may be available in the future. That might allow active line-level digital crossovers to become more widespread.

I also have a question about the crossovers in my current speakers that you helped me with. If I wanted to bi-amp the speakers would it be possible for me to simply separate the leads that go to the high and low section of the crossover and connect them to two separate amps?

Yes.

Also, what is the role of the resistors that shunt both the tweeter and the woofer?

The two 4 ohm resistors in the tweeter circuit lower its output to a level similar to the less sensitive woofer. The use of 2 resistors, one in series with the tweeter and one in parallel, called an L-pad, helps keep the impedance more uniform than a single resistor in series with the tweeter. There is an additional 1.5 ohm resistor in the diagram, on the lower right. It isn't wired to anything. Is it an optional substitute for one of the other resistors?

The 2 ohm resistor in the woofer circuit is part of trap filter, or LCR circuit. It probably is there to further suppress break up noise made by that aluminum woofer.

 

[Hi Ho]

Hi Ho,
I know you built your DIY mains - I assume on existing plans.

No, in fact, I selected the drivers and designed the boxes and with the help of others got a good crossover design. My initial crossover design was very crude and while it worked, the performance just wasn't there compared to the current design that TLS Guy came up with.

The two 4 ohm resistors in the tweeter circuit lower its output to a level similar to the less sensitive woofer. The use of 2 resistors, one in series with the tweeter and one in parallel, called an L-pad, helps keep the impedance more uniform than a single resistor in series with the tweeter. There is an additional 1.5 ohm resistor in the diagram, on the lower right. It isn't wired to anything. Is it an optional substitute for one of the other resistors?

I believe the extra resistor was optional to put in line with the tweeter for additional padding. I believe that I did try that and kept it in place but I didn't change the schematic to reflect this.

I don't want to come off as a total dummy. I learned a lot about speaker design when I built these speakers but the crossover stuff went right over my head. It makes a lot more sense now.

 

[lsiberian]

I think one of the main reasons for not going active has been the lack of good options for low cost amps historically. In the DIY community going active is much easier now than it was even 3 years ago. I literally was looking at thousands of dollars to build my reference set. Now I can get a minidsp and amp module for much cheaper.