 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
67.146.34.102
Hi inmates, for a 2nd order 2 way crossover, is there a benefit to a Butterworth or Linkwitz-Riley or ?? design? Thanks, Mark
Follow Ups:
Sorry forgot to add this to my first response to your question. When you ask about the difference between a Butterworth and Linkwitz 2nd order crossover did you learn of the 2nd order Linkwitz passive crossover from the diyaudiovideo.com online crossover calculator? because the Linkwitz & riley is most always thought of as a 4th order crossover and most people don't know a Linkwitz & riley can be a 2nd order passive or active.
The 2nd order Butterworth and Linkwitz are the same configuration so if you looked at a schematic it's the same layout it's just the value of the components that are different. But once again passive crossovers will never be textbook Butterworth, Linkwitz,
So, are you trying to design a crossover for some drivers you have or are you just curious??
A two-way speaker usually never has a pure 2nd order crossover, and it will never be a textbook alignment. Most 2-way crossovers are a 2nd order on the woofer and a 3rd order on the tweeter. The woofer is usually fine with 2nd order 12db per octave slope and the tweeter will usually need a 3rd order 18db per octave slope. You can find a lot of popular 2 way speaker crossover schematics online and they will almost always be a hybrid. This is also the case on three way designs. As far as the linkwitz go's you don't see 4th order passive crossovers.
If you wanted to learn more about crossovers, you could download xsim crossover simulator it's free and easy to use. You will need your drivers FRD & ZMA files these are the frequency response & impedance response measurements of your drivers. If you just wanted to use the software, you can go to parts express and download the FRD & ZMA file of any Dayton driver import them into xsim and you can design a proper crossover. And have fun learning.
This is 90% accurate to be 100% you would need to measure the drivers in the cabinet they are going in the woofers response will be slightly different than the manufacture that measure on a baffle and you can also compensate for baffle step.
You don't see textbook crossover alignments like Butterworth, Bessel, Chebyshev, Linkwitz used in crossover design it's always a hybrid
If you use 2nd order HP/LP filter combo then:
* with L-R, the "knee frequency" of each filter is defined as the -6dB (half voltage) point.
So a L-R XO @ frequ 'X' will be flat across the XO region.
* in contrast, a Butterworth XO @ frequ 'X' will be 3dB up at the point the two slopes intersect.
This is because the "knee frequency" of each BW filter is defined as its -3dB point.
If you want to achieve a flat frequ across the XO region ... you need to spread the HP & LP "@ frequencies" apart slightly.
So you might have a 2nd order L-R XO defined as being "@ 200Hz" - whereas if you wanted a flat frequ response a 2nd order BW XO would need to be:
* LP @ 1650Hz", and
* HP @ 240Hz.
You would need a sim program like 'lspCAD' to work out the right spread of the two "@ frequencies".
Not least of which is the unfiltered acoustic response, in cabinet, of the drivers themselves. The actual crossover slopes are a function of the electrical transfer functions of the filters COMBINED WITH the natural slopes of the drivers. The resulting component values may differ significantly from textbook calculations, especially once you factor in baffle step compensation (so you don't sacrifice bass and get a lean and shouty midrange) and impedance compensation (so the filters track properly). If the chosen drivers have any nasty response peaks, you'll also need notch filters, which add their own complications.
There is actually no such thing as 2nd order LR -- Linkwitz filters are by definition 4th order, consisting of two cascaded 2nd order Butterworths -- but you can certainly have a 2nd order filter with a Q of 0.5 (tapering gently down to the elbow frequency), that is down -6dB at the crosspoint. Butterworths of any order have a Q of 0.7 (maximally flat down to the elbow frequency) and are down -3dB at the crosspoint. The important thing is to achieve a summed response that is flat through the crossover region, for an octave or more either side, indicating good phase tracking.
I would no longer attempt such a design without proper software. There are many inexpensive or even free programs you can download, and if you get REALLY serious there is SoundEasy, the most advanced speaker design program available.
For fuller discussion, see both Ray Alden's Loudspeaker Design 201, and the Zaph Audio website. Zaph provides, for many of his designs, separate graphs of the raw driver responses, electrical transfer functions of the filters, and combined and summed responses, so you can really see how everything works together.
nt
No Tom I did not read his post before I posted I usually just post what I know. But I just went and read the post one time no need to read a couple times and caught the mistake, did you? Yes indeed there are 2nd order passive and active Linkwitz & Riley crossovers. Next time I will read what others post before I post thanks for pointing that out to me. NT
Linkwitz and Reilly ORIGINALLY designated their crossover innovation as a fourth order topography, derived from two cascaded second order Butterworth filters. It is of course entirely possible to derive a second-order function with a Q of 0.5 and a crosspoint at -6dB, and this is now generally called an LR2 transfer function. Theoretically, you could even make a third order filter with those parameters.
Vance Dickason's book was my bible when I got started in DIY, some 30+ years ago. It's a treasury of textbook formulae, but at least my early (fifth?) edition did a poor job of explaining the applicability of some of the formulae. Like shelving filters for BSC. But nowadays, ANY decent design software that starts with actual acoustic and electrical measurements of the drivers IN THE INTENDED BOX will get you closer to an optimum blending of the drivers without endless number-crunching on your scientific calculator. For the actual testing, the Dayton Audio OmniMic and DATS software/hardware packages are unbeatable for the price.
I use OmniMic v2 DATS V3 and Clio pocket have used leap in the past agree for the money and it's easy to use the Dayton OmniMic V2 & DATS V3 can't be beat.
I didn't mean it like that (pointed at you) but those two paragraphs are important parts of making crossovers that many don't appreciate.
One can look up formula's or tables to find parts values for filters using a resistor as load but what drivers actually look like electrically can have a major impact on the result.
Software like mentioned often use both the drivers raw response and impedance curves to derive the needed parts values to get say "flat" response.
I think LSPcad demo version allows one to try things, make filters etc (but not save). This will do more than you need, it is very powerful and one can use a curve fitting tool to "let it" adjust parts valued to hit a target.
The people that don't appreciate never will. They can stick to guessing asking others that do know or using online calculators. The people that understand stick to real world measurements and good simulation software. And the number one tool in learning speaker/crossover design is
Vance Dickson loudspeaker design cookbook.
Butterworth
A signal processing filter that's designed to have a flat frequency response in the passband. It's also known as a maximally flat magnitude filter. Butterworth filters have a sharp initial cutoff, a +3 dB sum at crossover, and a smoother response. They're commonly used in control systems because they don't peak.
Linkwitz-Riley
A filter made by combining two Butterworth filters. It has a flat summed output, moderate rolloff, and is always 6 dB down at the filter cutoff frequency. The Linkwitz-Riley alignment is the most commonly used active crossover alignment in the professional audio industry
Linkwitz-Riley filter is made by combining two Butterworth filters. The main difference between the two is that Butterworth crossovers are 3dB down at the filter cutoff frequency while the Linkwitz-Riley filters are flat
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
