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Linkwitz-Riley response not perfectly flat

Started by jungledmnc May 15, 2009

Greg Berchin wrote:

> Let's create a generic Linkwitz-Riley 3-way crossover. The Lo band > covers 0 Hz to "L" Hz, the Mid band covers "L" Hz to "H" Hz, and the > Hi band covers "H" Hz upward. Name the filters "lpL" (lowpass-L), > "hpL" (highpass-L), "lpH" (lowpass-H), and "hpH" (highpass-H).
[...]
> Think that's complicated? You should see the 4-way configuration.
I am surprised to see the interest in that kind of sophistication. Being involved with the design of the audio electronic for many years, I was always told by the acoustic engineers that for crossover filter you never actually need anything more complex then the Butterworth of the 4th order; and I tend to agree with them. In the most of cases, you can get by just the 2nd order filters. I've seen the bizarre arrangements like Bessel lowpass + FIR highpass; the sound was neither better or worse compared to the trivial Butterworth filters. IMO that pre-ringing, linear phase, LinkwitzRiley and such is the audiofoolery of the second kind (The first kind is about the tubes and the silver wires). Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Vladimir Vassilevsky wrote:
> > > Greg Berchin wrote: > >> Let's create a generic Linkwitz-Riley 3-way crossover. The Lo band >> covers 0 Hz to "L" Hz, the Mid band covers "L" Hz to "H" Hz, and the >> Hi band covers "H" Hz upward. Name the filters "lpL" (lowpass-L), >> "hpL" (highpass-L), "lpH" (lowpass-H), and "hpH" (highpass-H). > > [...] > >> Think that's complicated? You should see the 4-way configuration. > > I am surprised to see the interest in that kind of sophistication. Being > involved with the design of the audio electronic for many years, I was > always told by the acoustic engineers that for crossover filter you > never actually need anything more complex then the Butterworth of the > 4th order; and I tend to agree with them. In the most of cases, you can > get by just the 2nd order filters. I've seen the bizarre arrangements > like Bessel lowpass + FIR highpass; the sound was neither better or > worse compared to the trivial Butterworth filters. IMO that pre-ringing, > linear phase, LinkwitzRiley and such is the audiofoolery of the second > kind (The first kind is about the tubes and the silver wires).
Linkwitz-Riley filters are about avoiding destructive interference in auditoriums (auditoria?) where the seats are on a sloping floor. The floors in my house are reasonably level. 'Nuff said? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Vladimir Vassilevsky wrote:
> > > Greg Berchin wrote: > >> Let's create a generic Linkwitz-Riley 3-way crossover. The Lo band >> covers 0 Hz to "L" Hz, the Mid band covers "L" Hz to "H" Hz, and the >> Hi band covers "H" Hz upward. Name the filters "lpL" (lowpass-L), >> "hpL" (highpass-L), "lpH" (lowpass-H), and "hpH" (highpass-H). > > [...] > >> Think that's complicated? You should see the 4-way configuration. > > I am surprised to see the interest in that kind of sophistication. Being > involved with the design of the audio electronic for many years, I was > always told by the acoustic engineers that for crossover filter you > never actually need anything more complex then the Butterworth of the > 4th order; and I tend to agree with them. In the most of cases, you can > get by just the 2nd order filters. I've seen the bizarre arrangements > like Bessel lowpass + FIR highpass; the sound was neither better or > worse compared to the trivial Butterworth filters. IMO that pre-ringing, > linear phase, LinkwitzRiley and such is the audiofoolery of the second > kind (The first kind is about the tubes and the silver wires).
Linkwitz-Riley filters are about avoiding destructive interference in auditoriums (auditoria?) where the seats are on a sloping floor. The floors in my house are reasonably level. 'Nuff said? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
On Tue, 19 May 2009 10:19:23 -0500, Vladimir Vassilevsky
<antispam_bogus@hotmail.com> wrote:

>I am surprised to see the interest in that kind of sophistication. Being >involved with the design of the audio electronic for many years, I was >always told by the acoustic engineers that for crossover filter you >never actually need anything more complex then the Butterworth of the >4th order; and I tend to agree with them. In the most of cases, you can >get by just the 2nd order filters.
Well, a Linkwitz-Riley 4th order is just the cascade of two Butterworth 2nd orders, so I guess that covers both of your assertions. :)
>I've seen the bizarre arrangements >like Bessel lowpass + FIR highpass; the sound was neither better or >worse compared to the trivial Butterworth filters. IMO that pre-ringing, >linear phase, LinkwitzRiley and such is the audiofoolery of the second >kind (The first kind is about the tubes and the silver wires).
To each his own. Having designed a whole class of Bessel-derived matched-delay crossovers (http://www.aes.org/e-lib/browse.cfm?elib=8170) that, to my ears, sound better than the classical designs, I respectfully disagree but refuse to argue about it. In many ways it's like arguing about what flavor of ice cream is the best ... there is no answer. Oh, and I do have tubes in my system, but no silver wire. Greg
On Tue, 19 May 2009 11:38:25 -0400, Jerry Avins <jya@ieee.org> wrote:

>Linkwitz-Riley filters are about avoiding destructive interference in >auditoriums (auditoria?) where the seats are on a sloping floor.
As I understand it, that's close but not exactly correct. With Linkwitz-Riley crossovers, the lowpass section and the highpass section are in-phase at all frequencies. In large venues, where the audience is in the far-field, phase differences between the lowpass and the highpass sections can lead to lobes that cause frequency response variations between sections of the audience. I can intuit the effect that the slope of the floor would have upon this, but overall the most important thing is the off-axis angle and thus the degree to which any interference, destructive or constructive, might occur. Greg
Greg Berchin wrote:

   ...

> Oh, and I do have tubes in my system, but no silver wire.
My first decent hi-fi amplifier had Invar (or some such) wire in it. I had a friend studying EE in Columbia back when I did odd jobs around the neighborhood. One of his fraternity brothers had built a 20-watt Heathkit that turned out to have a hum problem that nobody in the fraternity or willing faculty could track down. I traded him my 10-watt Bogen PA amplifier for it, way overextending my meager abilities. There was a spool component in it covered with yellow tape and some pen indication I couldn't read. Laborious tracing revealed that it was an unbypassed cathode resister, and when I unsoldered it for a better look, it read, "100 ohm 0.1%". I replaced it with a 100-ohm composition Allen-Bradley and the hum went away. The wirewound, evidently a swiped replacement for the lost original component, was near the power transformer. Somewhere, I still have it. When is a resistor not a resistor? When it is the secondary of a transformer! :-) That was a sturdy circuit. Once, with the speaker accidentally disconnected, I heard faint sound anyway. The first clue was a bit of arcing in the 6L6 output tubes. The sound was the plates vibrating due to electrostatic forces. I turned the volume down, reconnected the speaker, and nothing was the worse for it. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;

Jerry Avins wrote:
> Vladimir Vassilevsky wrote: > >> >> >> Greg Berchin wrote: >> >>> Let's create a generic Linkwitz-Riley 3-way crossover. The Lo band >>> covers 0 Hz to "L" Hz, the Mid band covers "L" Hz to "H" Hz, and the >>> Hi band covers "H" Hz upward. Name the filters "lpL" (lowpass-L), >>> "hpL" (highpass-L), "lpH" (lowpass-H), and "hpH" (highpass-H). >> >> >> [...] >> >>> Think that's complicated? You should see the 4-way configuration. >> >> >> I am surprised to see the interest in that kind of sophistication. >> Being involved with the design of the audio electronic for many years, >> I was always told by the acoustic engineers that for crossover filter >> you never actually need anything more complex then the Butterworth of >> the 4th order; and I tend to agree with them. In the most of cases, >> you can get by just the 2nd order filters. I've seen the bizarre >> arrangements like Bessel lowpass + FIR highpass; the sound was neither >> better or worse compared to the trivial Butterworth filters. IMO that >> pre-ringing, linear phase, LinkwitzRiley and such is the audiofoolery >> of the second kind (The first kind is about the tubes and the silver >> wires). > > > Linkwitz-Riley filters are about avoiding destructive interference in > auditoriums (auditoria?) where the seats are on a sloping floor. The > floors in my house are reasonably level. 'Nuff said?
Oh, come on. Just take a microphone and make the phase/frequency response measurement. Then move it couple of feet away and measure again. The variation due to the crossover is barely visible compared to the other irregularities. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com

Greg Berchin wrote:

> On Tue, 19 May 2009 10:19:23 -0500, Vladimir Vassilevsky > <antispam_bogus@hotmail.com> wrote: > > >>I am surprised to see the interest in that kind of sophistication. Being >>involved with the design of the audio electronic for many years, I was >>always told by the acoustic engineers that for crossover filter you >>never actually need anything more complex then the Butterworth of the >>4th order; and I tend to agree with them. In the most of cases, you can >>get by just the 2nd order filters. > > > Well, a Linkwitz-Riley 4th order is just the cascade of two > Butterworth 2nd orders, so I guess that covers both of your > assertions. :) > > >>I've seen the bizarre arrangements >>like Bessel lowpass + FIR highpass; the sound was neither better or >>worse compared to the trivial Butterworth filters. IMO that pre-ringing, >>linear phase, LinkwitzRiley and such is the audiofoolery of the second >>kind (The first kind is about the tubes and the silver wires). > > > To each his own. Having designed a whole class of Bessel-derived > matched-delay crossovers > (http://www.aes.org/e-lib/browse.cfm?elib=8170) that, to my ears, > sound better than the classical designs, I respectfully disagree but > refuse to argue about it. In many ways it's like arguing about what > flavor of ice cream is the best ... there is no answer. > > Oh, and I do have tubes in my system, but no silver wire.
It would be my pleasure to design the pinnacle of the audio DSP technology, however I have to look at that from the practical standpoint. It turns out that the customers are interested in the reliability and the low cost more then in the advanced features and the ultimate specmanship. Since nobody ever expressed considerable remarks about the audio performance, that simply means that the audio performance is sufficient and there is no point to improve it further. Nevertheless it is nice to know that somebody is willing to pay for the advanced crossovers, so I can only express my jealousy :) Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Vladimir Vassilevsky wrote:
> > > Jerry Avins wrote: >> Vladimir Vassilevsky wrote: >> >>> >>> >>> Greg Berchin wrote: >>> >>>> Let's create a generic Linkwitz-Riley 3-way crossover. The Lo band >>>> covers 0 Hz to "L" Hz, the Mid band covers "L" Hz to "H" Hz, and the >>>> Hi band covers "H" Hz upward. Name the filters "lpL" (lowpass-L), >>>> "hpL" (highpass-L), "lpH" (lowpass-H), and "hpH" (highpass-H). >>> >>> >>> [...] >>> >>>> Think that's complicated? You should see the 4-way configuration. >>> >>> >>> I am surprised to see the interest in that kind of sophistication. >>> Being involved with the design of the audio electronic for many >>> years, I was always told by the acoustic engineers that for crossover >>> filter you never actually need anything more complex then the >>> Butterworth of the 4th order; and I tend to agree with them. In the >>> most of cases, you can get by just the 2nd order filters. I've seen >>> the bizarre arrangements like Bessel lowpass + FIR highpass; the >>> sound was neither better or worse compared to the trivial Butterworth >>> filters. IMO that pre-ringing, linear phase, LinkwitzRiley and such >>> is the audiofoolery of the second kind (The first kind is about the >>> tubes and the silver wires). >> >> >> Linkwitz-Riley filters are about avoiding destructive interference in >> auditoriums (auditoria?) where the seats are on a sloping floor. The >> floors in my house are reasonably level. 'Nuff said? > > Oh, come on. Just take a microphone and make the phase/frequency > response measurement. Then move it couple of feet away and measure > again. The variation due to the crossover is barely visible compared to > the other irregularities.
The nulls can be quite deep in the vertical direction. Auditoriums with sloped floors are best served by a main lobe that matches the floor's slope. Linkwitz-Riley filters tend to do that. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;