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Thread: DSP active crossover

  1. #21
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    Ah yes I know the frustration of having to wait in. We have friendly neighbours so usually something can be arranged. Once I had a neighbour sign for a car that was being delivered. Lol

    Going the avr route at this stage is the cheaper option. Assuming things go swimmingly I may consider going up the chain in terms of quality. What I don't have my head around on a multi channel power amp set up (say using your 7ch nak) is how I would incorporate a simple attenuation box without having to go down an expensive multichannel preamp road.

    Yes I know the naks can be very heavy. A mate has a PA Nelson pass one. That is a two man lift.

    Good luck with your new toys.





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    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  2. #22
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,514
    I'm Ken.

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    I attenuate the mid/tweeter signal at line level on my active crossover, before the power amps. The Woofer demands more but is 4ohm so its the 8ohm Mid/Twt that needs slight attenuation. (My power amp channels all have the same gain).

    Gordon has a MYTEK eight channel DAC and I think it has variable output on each channel, plus DSP software adjustment.

    I think that's right but he would explain it better than me.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + AT 33PTG II / AQVOX Phono 2 CI / Pro-Ject Pre Box RS / ESP Active X-Over / Nord MC500 Power Amps/ Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  3. #23
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    Thanks. Interesting.

    My cunning plan (!?) is to attenuate via the parametric eq each channel to take account of different driver's sensitivities (so instead of resistors in a passive xover).

    I could do overall volume control in the digital domain (and given that all the math is in 64 bit there will be negligible loss) but I'm scared of that as for sure I will at some point drive the speakers at full tilt. Been there and got the T shirt.

    Need to find a minute to pm Gordon.

    Did you get your new toys wired up?

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    Last edited by Edwardlon; 27-06-2018 at 18:47.
    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  4. #24
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,514
    I'm Ken.

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    I did a basic test on the amps to make sure they were working, with a cheap passive pair of speakers.

    I'm making a matching case for the active crossover about 2/3 the width of an amp and Using the same illuminated switch, which I need to match for brightness using the voltage I have available. 9k1 seems to be the resistor I need, so just ordered those. Got some feet to fit, I'm almost there. This is my build thread if you've not seen it:

    http://theartofsound.net/forum/showt...sh-Start/page4
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + AT 33PTG II / AQVOX Phono 2 CI / Pro-Ject Pre Box RS / ESP Active X-Over / Nord MC500 Power Amps/ Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  5. #25
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    Ah yes I've been following that thread. Quality!


    Via Tapatalk
    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  6. #26
    Join Date: Sep 2011

    Location: County Durham, UK

    Posts: 91
    I'm Gordon.

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    Quote Originally Posted by Edwardlon View Post
    Thanks. Interesting.

    My cunning plan (!?) is to attenuate via the parametric eq each channel to take account of different driver's sensitivities (so instead of resistors in a passive xover).

    I could do overall volume control in the digital domain (and given that all the math is in 64 bit there will be negligible loss) but I'm scared of that as for sure I will at some point drive the speakers at full tilt. Been there and got the T shirt.

    Need to find a minute to pm Gordon.

    Did you get your new toys wired up?

    Via Tapatalk
    Spot on with your cunning plan! It's a good idea to provide a bit of headroom in each channel - so dropping each input by a few db (on top of what you may need for driver sensitivities) will be beneficial - digital clipping is not nice! Don't worry about digital volume control either - you're working inside a 64 bit environment in JRiver which is dithered down to 24bit at the output. 6db attenuation = 1bit less so you have plenty to play with.

    If you are looking for an 8 channel DAC I'd suggest the Motu 8A - an excellent piece of pro gear at about 750 and compact to boot. I love my Mytek 8x192ADDA and it's not going anywhere, but it's a big piece of gear and at more than 2k, not cheap. The Motu is a bargain by comparison and it's what I would choose if I was doing this now.

    I went the software dsp route about 4 years ago now and don't regret it one bit (sorry for the pun).

    There's been some good input from others on this thread so I'd just say go for it - you won't regret it. DSP controlled speakers is the way forward IMO. I've heard both the Kii3 and the Dutch & Dutch 8Cs (way ahead of anything else at the recent Cranage show for me) and they are both outstanding speakers.

  7. #27
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    Hi Gordon

    Thanks for the very helpful response. Yes I will create a few db headroom but I was guessing the JRivers clipping control will save my bacon in extreme.

    I've moved ahead a bit on this cunning plan (hope it is not a Baldrick failure mind you!) and got various additional bits - or they are on their way. A Sony 7.1 AVR is heading over. This AVR, I'm reliably informed, has top notch amps (relative to other AVRs that is). Extra speaker cable on its way (will need 6 x 2m + internal cab wiring) and a dozen speaker posts. Plus various line level cabling. Oh and a xonar 7.1 dac (nice and cheap).

    Still need to get some caps (to protect the tweeters from user error). The sacrificial speakers I will be using have their passive crossovers set at 800hz and 5khz so I will start from there.

    Also sussed out fully how to set things up in JRiver - routing of channels and crossovers etc.

    As this is just a fun learning project my focus is simply to do things cheaply. I'll need to get a decent mic at some point to create a room correction filter.

    Maybe later on I can go up the tree in terms of quality. The Moto or Mytek or MiniDSP comes to mind. Or just plagiarise what Ken is doing with his build.
    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  8. #28
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    Just had a skim at the Motu-8 unit. Yummy.
    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  9. #29
    Join Date: Mar 2017

    Location: London N2

    Posts: 812
    I'm Edward.

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    I'm confused on what value capacitor I need to get to protect the tweeters in this project. In post #2 of this thread James/Jazid suggests 2.2 uf but in various other places I see differing values being mentioned. For example in this post a value of 68uf is mentioned.

    Given that the passive mid-range/tweeter crossover point in my speaker is currently at 5kz what value cap do I need to get to protect the tweeter? In my simple way of thinking I need a cap that provides a basic high pass filter at somewhere below 5kz (say4.khz) such that any stuff below 4.5kz does not get transmitted.

    Clearly I'm missing something in my understanding.
    Source: Tidal/Roon
    DAC: Metrum HEX NOS

    Amp: Sugden Masterclass 2018 spec, Radford Revival STA25,
    Speakers:, Tannoy Eaton


  10. #30
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 35,720
    I'm Geoff.

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    68uF is far too big. 3uF or smaller will do the trick.

    3uF in a 1st order crossover will roll an 8 ohm tweeter in at 6db/oct to near enough level (full) output at around 3kHz.

    If you need to attenuate the tweeter level in comparison to the mid driver using a two way active crossover, an 'L' pad will do this.

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