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TOPIC: FIR location in miniSHARC plugins

FIR location in miniSHARC plugins 6 years 7 months ago #11665

  • dreite
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If I missed it searching, sorry.

Am I the only one who thinks the FIR capability of the miniSHARC plugins should be on the input channels vice the output channels?
(A much more logical place to put it considering the objective use in most systems.)

Cheers,

Dave.
Last Edit: 6 years 7 months ago by dreite.
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FIR location in miniSHARC plugins 6 years 7 months ago #11680

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Dave,

I guess that it depends a bit of the application, but the idea here was more to "linearize" each crossover/filter on specific outputs. (e.g. using rephase to build each xover with FIR rather than IIR) Now putting the same amounts of total taps to the input side could indeed be done (e.g. OpenDRC like). Something we can consider for next year but would again need another two plug-in/firmware since 48/96 are requiring quite major modification to make it work as it should..

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FIR location in miniSHARC plugins 6 years 7 months ago #11686

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It just seems more logical (to me) to generate phase-correction as a composite vice individually. It's certainly doable either way, but more cumbersome (IMO) when generating linear filters for each driver since they're already minimum-phase response even with the appropriate IIR filters added.

The excellent rePhase utility allows to create easily a composite phase-correction response which means a psuedo-linear-phase system response could be created by loading just a single set of coefficients in a common path.

Of course the FIR capability can be used for more than phase correction, but I'm guessing that we crazy audiophiles out here are primarily interested in it for that capability. :)

Just my two cents.

Thanks,

Dave.
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FIR location in miniSHARC plugins 5 years 6 months ago #17618

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Just b ecame aware of this topic as I have a similat need and thought about a work around (despite higher cost...):

- Use one miniSHARC board in Stereo with OpenDRC 2x2 plug-in
- connect a second miniSHARC by I²S with miniSHARC 4x8 plug-in
- program both separately for a really well aligned system!
- Cost still way below DEQX!

All this to have sufficiently many FIR Taps available for Phase Correction.

BUT: Having a lot of well recorded high res music, my system shall be "native" 24/96 capable, which the OpenDRC 2x2 plug-in does not seem to support: What a PITY!

Sad greetings,
Winfried
Last Edit: 5 years 6 months ago by Hoffmann.
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FIR location in miniSHARC plugins 5 years 6 months ago #17651

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Hello Winfried,

Thanks for the follow up and indeed that is a good work around. We still do plan to have the large FIR bank at the input, on our magic growing TODO list.. :-)

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FIR location in miniSHARC plugins 5 years 1 month ago #19995

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I also use OpenDRC-DI for FIR filtering and 4x10 HD as a crossover.

To edit phase would suffice 2000-3000 taps, 6144 is not necessary.
And I would like to get from OpenDRC 24/96 as in 4x10 HD, and not 48k as it is now...

Please do support 96k in 2x2 plugin!
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FIR location in miniSHARC plugins 5 years 1 month ago #19996

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dreite wrote:
If I missed it searching, sorry.

Am I the only one who thinks the FIR capability of the miniSHARC plugins should be on the input channels vice the output channels?
(A much more logical place to put it considering the objective use in most systems.)

Cheers,

Dave.

My guess is that even if it would be more logical as you've described it would provide less profit margin as not so many people would buy a 2nd Shark just for FIR filter job. So, do not expect to much motivation for doing that too soon. When other vendors will start doing such a setup maybe then we'll see some emulation from these dev guys.
Regards,
Dorin
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FIR location in miniSHARC plugins 5 years 1 month ago #20033

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@ Dorin,

Mmmh, I'm not sure what kind of insider information you're getting from Hong Kong headquarter to make such statements about our values (i..e we want to sell more), but I can tell you that sometimes, the story is actually much simpler than that.. :-) FIR tap count is related to processing power. Period. Nothing to do with any other values you try to imply in your statement. :-)

The miniDSP 4x10 runs on a processor that can't do both FIR + all the things he's doing @ 96kHz. simple explanation.
The OpenDRC runs on a Sharc DSP that already does the most number of taps by USD on the market. We already run at 100%

A 2nd Sharc wouldn't help much actually because there is no way to stack it to either boards. :-)
We'd love to have more taps, more features, more everything.. Sometimes, it's just down to DSP power. That's all.

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FIR location in miniSHARC plugins 5 years 1 month ago #20037

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I can understand most of what you've said except of why did you choose to put 8 small FIR blocks on each output channels instaead of just 2 bigger FIR blocks on the input channels? What I said in my previous post is just a guess but "Se non è vero, è bene trovato".;-)

Also, there is no need to stack two Sharks, they can be put one after another in the signal flow as two different boxes.
Last Edit: 5 years 1 month ago by DorinD.
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FIR location in miniSHARC plugins 5 years 1 month ago #20038

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Dorin,

The cynicism in your posts is not necessary.

The architecture of the FIR blocks in the plugin is defined, at this point. For my own usage, I would prefer all the FIR blocks at the inputs, but I can easily work with the plugin in its current state. In fact, that's what I've done to create a "linear-phase" version of the Linkwitz LX521 system.

I suspect, for most users, FIR blocks on the output channels might be preferable. It depends upon what your objective is.
I don't see this is being a serious issue with plugin architecture. Just my opinion.

Cheers,

Dave.
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FIR location in miniSHARC plugins 5 years 1 month ago #20045

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DorinD wrote:
I can understand most of what you've said except of why did you choose to put 8 small FIR blocks on each output channels instaead of just 2 bigger FIR blocks on the input channels? What I said in my previous post is just a guess but "Se non è vero, è bene trovato".;-)

I am completely against using 2 large FIR banks on the inputs instead of using the current 8 on each output. I am using the FIR filter to create linear phase crossovers for each speaker in the output. If the FIR banks were moved to the inputs then I couldn't get the slopes I need as I would have to use the conventional minimum phase crossovers and then try to linearize them from the input section.

Besides, how would you implement the FIR filtering? The miniSHARC has 4 inputs. So either you have all your FIR taps allocated to just two of the inputs, ignoring the other two channels, or you divide the FIR filters among all four inputs for those using all four channels. Let's say someone were to feed 2 sources to the miniSHARC. They would need four input channels but only 2 would be active at a time. In this case that person would only have half of the taps available for each source. The way miniDSP has done it is better. You can correct the individual channels regardless of source. There are no limitations in the way it is done now (other than the number of taps). The way you propose would only make it more convenient in a few cases while severely limiting people who do different things with their DSP.

Devteam, please do not move the FIR filters to the input section unless you develop two plugins that give people the choice.
Last Edit: 5 years 1 month ago by sly.
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FIR location in miniSHARC plugins 5 years 1 month ago #20046

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Yes, this is exactly the trade-off I was alluding to. (There are advantages/disadvantages either way.)

I don't understand your comment regarding not being able to get the slopes you need. Are you wanting to use slopes greater than 48db/octave? In that case, I can understand your point. I don't use slopes greater than 24db/octave and those be programmed with the minimum phase filters and a composite phase correction applied on the inputs. You will achieve the same result with a constant group delay across the audio band.

The splitting of the available taps to support both inputs is a good observation. However, I believe most miniSHARC users are utilizing just one set of inputs.

I'm not unhappy with the plugin the way it's currently configured, but it would be nice to have the other option.

Cheers,

Dave.
Last Edit: 5 years 1 month ago by dreite.
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FIR location in miniSHARC plugins 5 years 1 month ago #20048

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I'm using 96db/octave slopes. I use the FIR taps to create the crossover slope while keeping it linear phase. I'm considering implementing a brick wall crossover. I need to measure the output though as I'm not sure the miniSHARC has enough taps.
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FIR location in miniSHARC plugins 5 years 1 month ago #20051

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Given that taps can currently be allocated to different FIR blocks, it doesn't seem like an either/or proposition. If miniDSP added FIR blocks on the inputs, then you can allocate whichever way suits the application. There will be some cost as there's a minimum of 8 taps per block. Just a suggestion :)
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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FIR location in miniSHARC plugins 5 years 1 month ago #20052

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double post, sorry.
Last Edit: 5 years 1 month ago by sly.
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