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TOPIC: Need 2In/4Out miniSHARC

Need 2In/4Out miniSHARC 6 years 9 months ago #10425

I am looking for a miniSHARC or OpenDRC solution that will provide 2 inputs and 4 outputs. I don't see a box with this configuration, but I'm having a little trouble deciphering the options available for the minSHARC I/O. Any help would be greatly appreciated!
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Need 2In/4Out miniSHARC 6 years 9 months ago #10430

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openDRC will always be 2ch in and 2ch out. So if you need 4 ch out miniSHARC is the way to go.
In order to give you more support regarding the proper setup it would be helpful to learn a bit more about your system. Do you have an analog or digital source? Do you want to use existing DACs (or amps with digital input) or will you need analog outs?
A possible all analog setup would be for example: regards, Daniel
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Need 2In/4Out miniSHARC 6 years 9 months ago #10432

Thanks for the info! I'm just getting my feet wet with the miniDSP products and there are certainly a lot of options.

Sorry for the lack of detail. I am trying to put together processing to allow me to use four side surround speakers rather than just two. I need FIR all-pass filtering to properly calibrate it. I would like to connect my AVR preouts for my left surround and right surround to the DSP, and from the DSP go into an external amplifier. Preouts from the AVR are unbalanced, but the amp can be either balanced or unbalanced. The left surround channel would supply two speakers, each with different filtering, and the same for the right surround.

Would it be preferred to use two curryman DACs so that all four output channels are produced by the same hardware?

Are there any options for a curryman DAC that are Plug-N-Play? My soldering skills are not what I would like for them to be :)

Thanks again!
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Need 2In/4Out miniSHARC 6 years 9 months ago #10433

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To be honest I am not sure if FIR filters will have a real big benefit in this setup. You'll probably use Audissey or a similar system to EQ the other speakers and in this system using some IIR to EQ the additional surrounds will probably do very well. Not sure though what you need the allpass filter for? Do you want to realize a linear phase EQ of the speakers? If you simply need some delay, that available in all miniDSP products (partly limited wrt maximum available delay but should be perfectly sufficient for your application).

In your specific setup I'd recommend the 2x4 balanced. The inputs can also be used unbalanced and for the outputs you'll have both options for the connection to your amps, balanced or unbalanced. Together with the 2way advanced plugin you'll be perfectly fine.
Although I'd really appreciate if you buy some curryman DACs with a miniSHARC I have to admid that this is not really plug'n play (given that you mention that soldering is not your most loved hobby) ;)

best regards, Daniel
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Need 2In/4Out miniSHARC 6 years 9 months ago #10434

I need to be able to decorrelate the first surround from the additional surround. A time delay will do that to some degree, but I need additional decorrelation to prevent comb filtering. One approach is to apply an all-pass filter that randomizes the phase of the subsequent signal, which to my knowledge can only be done with an FIR filter. Do I understand correctly that the miniSHARC and OpenDRC are the only miniDSP products with FIR filtering capabilities?

If soldering is required, I can suffer through it :)
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Need 2In/4Out miniSHARC 6 years 5 months ago #12145

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curryman wrote:
openDRC will always be 2ch in and 2ch out.

regards, Daniel

Haven't even bought yet, but I'm not a newbie. I have Acourate and Acourate Convolver already configured and working in a 5.1 plus two stereo subs system... 8 channels of DACs (just showing off ;-). Anyway, I want to bulid a stereo backup in case the computer goes down. And I'd like to have control over phase response and resolution, so IIR plus FIR phase fix with the Open DRC looks like a solution. But the Open DRC (as you say) is stereo. And one MiniSharc with 4 channels would cut the number of taps per channel down to 2048 if I have my math right. Maye that's not a big deal using Acourate or Rephase in combination with IIR but I don't know. I could get my feet wet with one Mini Sharc and four AES outputs.

But I like the convenience of the Open DRC in a box. They're ready to go, already boxed. Two of them is only $140 more than two miniSharcs plus front panel and two Digi I/O boards. Could I use two Open DRC and develop a 2 x 4? For stereo with two sats and two subs? I have a Z Sys router so it's no trouble for me to feed the same AES signal into two Open DRC.

Do you think it would be hard to manage all the programming and USB-addressing of two Open DRC boxes? I would like to do the IIR in them to start with linearization, and then use Acourate or Rephase to top it off with some nice FIR phase correction.
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Need 2In/4Out miniSHARC 6 years 5 months ago #12164

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I don't see any problem doing so, especially as you already have the digital signal router (feed the same input signal to both openDRC). Only drawback is the USB-adressing. You'll have to program the openDRCs one after another. AFAIK there is no way to keep both attached and select them in the software (technically not possible).
regards, Daniel
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Need 2In/4Out miniSHARC 6 years 5 months ago #12165

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bobkatz wrote:
curryman wrote:
openDRC will always be 2ch in and 2ch out.

regards, Daniel

Haven't even bought yet, but I'm not a newbie. I have Acourate and Acourate Convolver already configured and working in a 5.1 plus two stereo subs system... 8 channels of DACs (just showing off ;-). Anyway, I want to bulid a stereo backup in case the computer goes down. And I'd like to have control over phase response and resolution, so IIR plus FIR phase fix with the Open DRC looks like a solution. But the Open DRC (as you say) is stereo. And one MiniSharc with 4 channels would cut the number of taps per channel down to 2048 if I have my math right. Maye that's not a big deal using Acourate or Rephase in combination with IIR but I don't know. I could get my feet wet with one Mini Sharc and four AES outputs.

But I like the convenience of the Open DRC in a box. They're ready to go, already boxed. Two of them is only $140 more than two miniSharcs plus front panel and two Digi I/O boards. Could I use two Open DRC and develop a 2 x 4? For stereo with two sats and two subs? I have a Z Sys router so it's no trouble for me to feed the same AES signal into two Open DRC.

Do you think it would be hard to manage all the programming and USB-addressing of two Open DRC boxes? I would like to do the IIR in them to start with linearization, and then use Acourate or Rephase to top it off with some nice FIR phase correction.
Hello Bob,

Very impressing/intimidating to see you here :)

I am planning on doing an evolution to rephase to automatically generate a mix of IIR (biquads) and FIR corrections. The user would set the number available biquads and rephase would try to use them to make the FIR "lighter". That would typically cover minimum-phase EQs as well as some linear-phase filters (eg a linear-phase LR would be turned into a minimum-phase LR + phase linearization). This would of course have to take into account some limitations of the openDRC regarding biquads (currently only some of the available biquads have enough precision to do clean corrections in LF...).

If you are doing a 2-way speaker then you have the option of using a pair of openDRC (one per side or one low one high, that would end up the same as the plugin is fixed to 48kHz and taps cannot be distributed among channels), or an openDRC for DRC and/or phase linearization in front of another crossover (IIR or FIR).

What is your system and what corrections are you doing?
Are you using automated (DRC-like) or manual corrections?

Thomas
https//wavetracing.com | rephase.org
Last Edit: 6 years 5 months ago by pos.
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Need 2In/4Out miniSHARC 6 years 5 months ago #12167

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pos wrote:

I am planning on doing an evolution to rephase to automatically generate a mix of IIR (biquads) and FIR corrections. The user would set the number available biquads and rephase would try to use them to make the FIR "lighter". That would typically cover minimum-phase EQs as well as some linear-phase filters (eg a linear-phase LR would be turned into a minimum-phase LR + phase linearization). This would of course have to take into account some limitations of the openDRC regarding biquads (currently only some of the available biquads have enough precision to do clean corrections in LF...)

Brilliant, that would be very helpful!!!

Can you make it so that I can load in two+ drivers at the same time as well please :-)

Stefan
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Need 2In/4Out miniSHARC 6 years 5 months ago #12168

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You mean doing more than one channel at a time in rephase, or loading several measurement and switching (or averaging) between them?
The later is on the todo list (has been for ages, it was meant to be that way from the start, but I became lazy...), the former would be a bit more convoluted to do.
https//wavetracing.com | rephase.org
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Need 2In/4Out miniSHARC 6 years 5 months ago #12169

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OOh, the later would be VERY handy as well.

I meant being able to load in both a midbass driver and tweeter ( or mid and bass drivers) so that It is possible to see the acoustic results of filters and their transfer function. Like you would in LSPCAD etal. Having to go back and forth between drivers comparing slopes can be a pain. This is all pie in the sky thinking though. I still haven't done my first setup yet and I promised I'd write a tutorial for you......I'm starting to think that it seems unlikely there will be enough taps to do the filters and phase linearisation in FIR though. Hopeful that next weekend I can have some time to mess around as the lid should be on the mega DAC with sharc by then.

Stefan
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Need 2In/4Out miniSHARC 6 years 5 months ago #12171

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orangeart wrote:
OOh, the later would be VERY handy as well.
Don't hold your breath, as it has been very difficult for me to find time to work on rephase lately :pinch:
I meant being able to load in both a midbass driver and tweeter ( or mid and bass drivers) so that It is possible to see the acoustic results of filters and their transfer function. Like you would in LSPCAD etal. Having to go back and forth between drivers comparing slopes can be a pain.
Ok I see.
Normally you do not need that: you should be able to *know* that you drivers will add properly (granted the levels and delays are properly set).
The filters in the "linear filters" tabs are all complementary LP/HP, so you are assured that the electrical filters will be complementary.
So to obtain complementary acoustical filters you should EQ your driver response for flat amplitude and phase throughout the crossover before applying the filter (say 1 octave around, depending on the slope, watch your measurement noise floor though if your driver has a steep natural rolloff...), so that the electrical and acoustical filters match.

Another method (typically used in passive or active IIR filters) is to try and match an acoustical target (that is what the "capture" function is for, but it is not there yet, either...) using EQ and filters of different slopes, but it makes trying different filters types and cross frequency much more difficult as you have to constantly adjust your EQ, whereas the "EQ to flat" method let you switch between different filter settings without further ado.
https//wavetracing.com | rephase.org
Last Edit: 6 years 5 months ago by pos.
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Need 2In/4Out miniSHARC 6 years 5 months ago #12172

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Dear Thomas:
Don't let me intimidate you! I bow to your superior knowledge. You know much more of the inside math than I know. I'm really just learning about the in-depth aspects of impulse responses. My expertise has been with hardware, clocking, some digital design. And I do know something at this point about room and loudspeaker correction, but most of it is by rote and learning from people like you and Uli.
You asked:

If you are doing a 2-way speaker then you have the option of using a pair of openDRC (one per side or one low one high, that would end up the same as the plugin is fixed to 48kHz and taps cannot be distributed among channels), or an openDRC for DRC and/or phase linearization in front of another crossover (IIR or FIR).

I am concerned about timing between two unrelated boxes, so I'm not 100% sure it would end up the same. I have a question in another thread about synchronizing the reset circuits and synchronizing two ASRC chips in two different boxes. I know how to deal with the hardware and the circuits, so technically I already know how to do that. I'm just not sure if it is necessary. Perhaps the timing differences will be small enough to be unmeasurable or insignificant after D to A conversion. I will buy two Open-DRC boxes, configure them as High pass left/High pass right and Low pass left/Low pass right. And try powering them on and off at different times and see if the timing between mains and subwoofer varies measurably. If it does, then it means that we have to synchronize either reset signals or clock signals or both between the two boxes.

What is your system and what corrections are you doing?
Are you using automated (DRC-like) or manual corrections?

Thomas

I'm using Acourate and Acourate Convolver with a dedicated computer and interface doing 5.1 plus two sub bass management.
"Automated" is not a good word to describe the capabilities of Acourate. Acourate is "semi-automated" for sure, but it has "automatic" facilities that are very smart. Uli has a psychoacoustically-valid measurement with a sliding FFT window that is so good that it avoids overcorrection. I have never had to adjust a filter that Acourate creates in terms of its magnitude! With other "automatic" systems, they tend to overcorrect, or to identify bands that don't have to be touched. It is not even necessary to give Acourate "limits", it takes care of it itself. Quite remarkable. I've never encountered a system this smart and this human-ear-right

Acourate uses a 65536 FIR filter order and is all FIR filters. I am not sure if the band eq is minimum phase or linear, but I believe the band eq is minimum phase. The crossover most commonly used is a Neville-Thiele "2nd order" linear phase. This is a very steep crossover that has enabled me to drop the harmonic distortion of my previously analog crossover by 10 to 15 dB! This is because the drivers are now running in their linear regions. It was an amazing event to see and hear that. The purity of tone is unmatched. As part of the procedure Acourate has an "excess phase" adjustment which must be done manually and helps to take care of analog passive crossovers which may already exist in your loudspeakers. It allowed me to tighten the measured impulse of the loudspeakers so that they look almost like a single point source or planar driver, it's remarkable. And the resulting transient response is remarkable.

Now I would like to build a backup system with mini-dsp because I'm totally dependent on the windows computer running Acourate Convolver to play my audio! And it would be fun to try two boxes so as to extend the FIR impulse response and have a bit more frequency resolution with the FIR.

Does this answer your questions, Thomas?

Now wh
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Need 2In/4Out miniSHARC 6 years 5 months ago #12191

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Hello Bob
bobkatz wrote:
Don't let me intimidate you! I bow to your superior knowledge. You know much more of the inside math than I know.
Math are easy (especially when it comes to convolution) but you experience and ear is priceless :)
When it comes to audio I'd take your subjective opinion over a mathematical proof :lol:
I am concerned about timing between two unrelated boxes, so I'm not 100% sure it would end up the same
Maybe I am wrong, but I think the maximum difference between two unrelated boxes fed by the same AES/EBU signal would be 1 sample after ASRC.
That is equivalent to about 7mm of distance difference between the speakers (or drivers) fed by each box, so you should not have any problem I guess.
Acourate is "semi-automated" for sure, but it has "automatic" facilities that are very smart. Uli has a psychoacoustically-valid measurement with a sliding FFT window that is so good that it avoids overcorrection. I have never had to adjust a filter that Acourate creates in terms of its magnitude! With other "automatic" systems, they tend to overcorrect, or to identify bands that don't have to be touched. It is not even necessary to give Acourate "limits", it takes care of it itself. Quite remarkable. I've never encountered a system this smart and this human-ear-right
I am sure this algorithm does a great job: Although I have never tried it myself I have only heard good things about Acourate and Uli.
rePhase only does manual corrections, so the responsibility is entirely on the shoulders of the user, both in terms of choices of what should be corrected and how, and in terms of measurement(s) quality and interpretation (but that is also the case with automated methods, and a single point measurement is not likely to precisely represent the real situation).
The crossover most commonly used is a Neville-Thiele "2nd order" linear phase. This is a very steep crossover that has enabled me to drop the harmonic distortion of my previously analog crossover by 10 to 15 dB! This is because the drivers are now running in their linear regions. It was an amazing event to see and hear that. The purity of tone is unmatched.
Brickwall filters are tempting beasts, but also have their drawbacks: they put a lot more pressure on polar response matching between drivers, as you don't have any overlap "smoothing", and any difference will turn out as a discontinuity off axis.
Preringing will also become apparent (at least measurable, if not audible) in this situation (preringing gets canceled only when drivers are summed exactly in phase), and even with perfectly matched polar responses it will still happen off axis on the vertical plan (unless you are using coaxial drivers, that is).
But the fact that it can be measured not not mean it is audible or problematic of course...
Does this answer your questions, Thomas?
Well, partly :D
I must say I am much interested in your loudspeaker setup.
I know mastering engineers tend to use floorstanding multiway passive loudspeakers (not unlike HIFI enthusiasts), so you setup with a two way actively filtered loudspeaker has me curious, to say the least!

Thomas
https//wavetracing.com | rephase.org
Last Edit: 6 years 5 months ago by pos.
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