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Active Crossover Frequencies

Discussion in 'trade discussion' started by RyanSoundLab, May 31, 2019.

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  1. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    McBride was my inspiration to start tweaking Naim circuits over 20 years ago! Lots of good ideas.

    The values in the XO schematics are very close to what I have calculated, too. These are classic 3-pole Bessel filters with excellent transient response. They are my baseline design at the moment.

    I just received a miniDSP to experiment with. Amazing variety of curve types and poles available. Plus the room compensation feature that is effectively an equalizer. I bought the UMIK-1 microphone with it for that purpose, too. the thing that strikes me first is how complex the setup is. Seems to me that the vast majority of people will need a dealer to set one up (and reset it every time you change your room or furniture!). this is in comparison to the relatively simple NAXO type of active crossover.

    Also just read about Dutch & Dutch speakers which appear to have all the DSP circuitry, the microphone, the xover, and the power amps built in so you don't even need a preamp, xover, separate amps, etc etc. Just plug the speakers into the internet and pick up your remote control! I'm wondering if there will be anything left of analog in the future?
     
  2. nobeone

    nobeone pfm Member

    Sound is analogue, analogue is going nowhere, sure good digital implementations can do a lot and processing power is cheaper everyday as are very competent codecs offering ADC and DAC at sample rates vastly above audible range. You will still need to wrestle my record deck from my cold dead hands to separate me from it :) I say that as somebody that has done digital filter design for industrial instrumentation.
     
  3. RyanSoundLab

    RyanSoundLab Trade: Ryan Sound Lab

    Just did an initial listen to the miniDSP vs a prototype Ryan Sound Lab crossover. This was done on my 2nd system which consists of an RSL 72, Mivera Class D power amps, and DIY transmission line speakers. Here are a few key specs of each xover setup:

    miniDSP: 2x4 HD model with best processor (Shark)
    -Linkwitz-Riley 8-pole filters (48db/octave slope)
    -setup as stereo 2-way crossover @ 3400 Hz. (nominally -6db points for L-R type filter).
    -adjusted actual crossover points for constant power output (-3db at 3400Hz): low freq = 3700Hz, high freq = 3100Hz. (this gives flat power through the pass band).
    -did not adjust for time delay (might make a difference since the -3db points are no longer the same).
    -tweeter output adjusted down -2db - about the same to my ears as turning the tweeters down manually to balance with the woofer-mid.

    RSL prototype xover: 2-way
    -Bessel 3-pole filters (18db/octave slope - same as NAXO)
    -Crossover point is 3400Hz also adjusted for constant power across passband. (-3db points: low freq = 3600Hz, high freq = 3200Hz approximately)
    -tweeter turned down for balance by ear.

    Setup: same amps, speakers, source, and preamp for both xovers. No change in volume setting on the preamp when switching (both xovers have unity gain).
    I won't elaborate here on setting up the miniDSP. Only need to mention that after the initial hassles with downloading software and understanding how to use it, the process of controlling the miniDSP is amazingly easy - selecting curve types, # of filter poles, frequencies, etc. Nicely done package.

    Initial listening reaction using CD and LP sources:
    - miniDSP is pretty decent but not great. Voices have added coarseness and a slightly hollow, metallic sound. Not terrible but a bit irritating. Same with piano - leaner, meaner - lacking in great tonality. On the plus side, the dynamics seem to be all there, at least on this system which is not my best one.
    -RSL xover has all the dynamics plus the smoothness and tonality you expect from an analog system. Not to say it's perfect but not fatiguing like the miniDSP for sure.

    There are dozens of possible filter setups for the miniDSP and I should try a couple of others to see what that does to the sound. Maybe these defects can be ameliorated by careful selection of parameters.

    Then, there is the whole equalization feature which I didn't even look at (although I have the microphone to try it sometime). Since that was a constant between the two components, at least the initial impressions weren't affected by that.

    I'm thinking of moving this evaluation to my primary system (Isobariks) to get more revealing information. Since a single miniDSP can only do one 3-way system (or two 2-way systems) I will try putting it on the woofer and midranges first, while leaving the tweeter on the existing analog xover to start.

    More reports to follow!
     

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