Linkwitz-Riley 24dB/octave Phase Coherent Crossover - diyAudio
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Old 23rd September 2002, 07:50 PM   #1
djdan is offline djdan  Romania
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Default Linkwitz-Riley 24dB/octave Phase Coherent Crossover

Dear Friends,

I need your opinions about this project :
24dB/octave Phase Coherent Crossover based by Rod Elliot project 09.

This crossover it would be better becouse combine the quality of 24db/octave Linkwitz-Riley filters with best phase-coherency and 24db/octave subsonic and ultrasonic filters.

Daniel
djdan40@hotmail.com
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Old 23rd September 2002, 09:17 PM   #2
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My only comment is your use of 1uF and 100nF caps: what kind of tolerence are you aiming for? Sallen & Key filters are rather suseptable to variations in the RC constant caused by component tolerence.

I built something similar over the summer and used 1% polystyrene caps and 1% metal film resistors throughout.

Regards,
David
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Old 23rd September 2002, 09:19 PM   #3
grataku is offline grataku  United States
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DJdan
I built the LR Xover of Rod Elliott and it worked fine, however, in the sound department I found it lacking (ie cold though not bright, mostly not very musical or involving), I can't really be more specific than that .
At this time I am ready to concede that it is probably due to the effect of the op amps not to the LR concept itself although I have heard that people temd to like lower order XOVER arrangment better.
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Old 23rd September 2002, 10:32 PM   #4
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At first glance it looks like an equaliser. You can't expect good sonics from an op amps farm although it may measure well.
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Old 23rd September 2002, 10:53 PM   #5
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For some obscure reason, I've never been able to warm
up to the sound of 24 dB/oct. It can measure great, and
I've tried it many times, but have always gotten better
sonic results with fewer poles. Go figure.

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Old 23rd September 2002, 11:11 PM   #6
djdan is offline djdan  Romania
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Schematics looks very complex , but this is nothing compare with a very good mix console where the sound is routed by 8 - 20 integrated circuits.
In fact , the music (80%) on CD or LP it is not such HI-FI to our expectations , so a 4 or 5 another circuits don't change it so much.

Fake STEREO ( a smart trick using PAN pot.) or,
Fake REVERB , DELAY , HALL etc.
Fake VOICE tonality maked by EQ, COMPRESOR, etc.

This is what we hear allmost the time when play music.

Anyway , if it is something better ( analog ) , I am very excited to see.

Regards !
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Old 23rd September 2002, 11:21 PM   #7
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I always recommend this crossover i need and GOOD active XO Since it comes from Nelson Pass, you can't go wrong with it. It's two way but by combining 2 you can have three way. It's using discreet op amps, and by updating semiconductors you can improve it even more. Actually, the whole idea is not that far from his current design (just few less variations ). I've built it and I like it.
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Old 24th September 2002, 12:04 AM   #8
dc is offline dc
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I ordered PCB's for Rod Elliot's Project 09 on Friday... Haven't received them yet, but his descriptions say that the same boards may be used for 12db/octave or 24db/octave. I'm hoping that parts substitutions will allow me to avoid the cold sound Grataku reported.

I built a three-way designed by Mr. Linkwitz (as part of the Phoenix project) using OPA2134's and am happy with it. Any comments on the OPA2134? Any suggestions for a better opamp for the next XO? BTW, this XO will be used with rear speakers, not as a replacement for Mr. Linkwitz's boards.
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Old 24th September 2002, 03:36 AM   #9
grataku is offline grataku  United States
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let's not get into the whole argument about how many opamps there are in a mixer, please. That is a real tragedy and we don't need to be reminded of that. I probably own a total of 3 CD that "sound" good the rest of them...never mind you got to listen to something. All my classical music CD are so bad that is almost impossible for me to listen to standing in front of the stereo, I mostly play them as a background. However, when I listen to my "good' CD I need a certain level of performance that quite frankly I wasn't getting from the LR xover setup.
The technology is there to produce good sounding CD the problem is with time and money and good audio engineers.

dc
did you actually build the phoenix? How do you like it? I use some lm6172, I think, There are many other "audio" grade opamps out there. One only needs some money to experiment with various models. There are several lists of recommended OpAmp available on the web and on this site too.
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Old 24th September 2002, 07:49 AM   #10
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A LR 4th order filter means that all the drivers are connected in phase, but it is not phase coherent thru the XO point. I have a Marchand which is a state-variable 4th order XO. It definetly adds a veil when in circuit. It uses a lot fewer op-amps than the posted scema. Could you not put a 2nd order filter on each op-amp and get away with half the active parts in the filter stages?

I plan on replacing my Marchand with a home brew subtractive XO (using tubes if i can figure it out). Or with just a 1st order PLLXO (might need more extended woofers thou).

dave
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