# MiniDSP - Why not??



## Dasher

Hi,

I am getting ready to undertake my second DYI sub project and have a question regarding EQ and crossover.
I notice a lot of people use the Behringer Feedback Destroyers but I don't see a lot about the miniDSP.
The mini seems to do everything I want at a great price but I thought I had better find out why more people don't use it? Is there something I am missing here?


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## fusseli

I think the minidsp is relatively new and the the FB Destroyers have been around for years.


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## SAC

Either will work for EQing the direct signal, but neither are effective in addressing the non-minimum phase issues presented within the room caused by the speaker-room interaction of direct and indirect signals.

In other words, this is NOT an effective comprehensive room-speaker interaction treatment. For that you need to be looking and solving issues in the time domain. Hence tools such as the ETC response and the surgical use of signal alignment, absorption and diffusion.

It all depends on what problems you imagine the treatment to address.


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## fusseli

SAC said:


> Either will work for EQing the direct signal, but neither are effective in addressing the non-minimum phase issues presented within the room caused by the speaker-room interaction of direct and indirect signals.
> 
> In other words, this is NOT an effective comprehensive room-speaker interaction treatment. For that you need to be looking and solving issues in the time domain. Hence tools such as the ETC response and the surgical use of signal alignment, absorption and diffusion.
> 
> It all depends on what problems you imagine the treatment to address.


There are other off the shelf devices that do that unlike the BFD and minidsp, but the pricetag starts to elevate quickly. E.g. http://www.creativesound.ca/details.php?model=ANTIMODE8033C

The BFD and minidsp are both economical and effective for acheiving a flatter FR, which does serve most peoples goals. A flattened FR is still a big improvement over no treatment at all to an audio system.


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## Dasher

Thanks for the replies...

_In other words, this is NOT an effective comprehensive room-speaker interaction treatment. For that you need to be looking and solving issues in the time domain. Hence tools such as the ETC response and the surgical use of signal alignment, absorption and diffusion_

To be honest I don't even understand what your talking about so I guess I'm not to worried about time domain issues?.

_A flattened FR is still a big improvement over no treatment at all to an audio system._
All I'm really after is an adjustable crossover and EQ to boost the bottom end on a sealed sub and mayby use it with REW if I can figure out how.

Cheers...


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## SAC

fusseli said:


> A flattened FR is still a big improvement over no treatment at all to an audio system.


I wish that was a valid generalization.

Unfortunately, the 'flatness' of the frequency response is of very little consequence except as a direct source.

Equally unfortunate is the fact that EQ is effective at best only at very low frequencies where the interacting signals are effectively within 1 cycle difference.

EQ does NOT correct for non-minimum phase errors resulting from the interaction (superposition) of direct and indirect signals within the room.

There is good reason why the use of EQ is NOT sufficient to correct speaker-room interaction issues! (And one would be smart to investigate the reason why adjusting a frequency response with EQ can make the FR look flatter, while substantially exacerbating anomalous behavior in the system!!! If this is not understood, more research is advisable!)

My point was to direct one to a larger awareness of the behavior of sound within a bounded space viewed from the causal time domain perspective rather than from a derivative frequency domain perspective. With an awareness of this perspective, coupled with the tools programs such as REW afford one to view such behavior, and the additional tools we now have at our disposal with which to treat such issues, you will discover a much more effective arsenal of techniques and tools to more adequately affect the quality of sound in the room.

I am not here to debate this. It is an established fact (which was debated and reflectively settled in the mid-late '80s in professional and academic circles) that many may not yet be fully aware. Thus my purpose being to simply point this out and hopefully encourage more productive research.

And as has been mentioned, such a technique may potentially effectively be used to modify the character of the minimum phase direct signal emanating from the speaker, but the frequency domain response view does not provide a sufficient degree of insight into the behavior of the speaker-room interaction within the room. Such environmental frequency response anomalies must be solved in the time domain.


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## JohnM

Dasher said:


> All I'm really after is an adjustable crossover and EQ to boost the bottom end on a sealed sub and mayby use it with REW if I can figure out how.


The MiniDSP is a better solution than the BFD for that. The "Advanced" MiniDSP plug-ins can import filter coefficient files generated by REW.


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## fusseli

SAC said:


> I wish that was a valid generalization.
> 
> Unfortunately, the 'flatness' of the frequency response is of very little consequence except as a direct source.
> 
> Equally unfortunate is the fact that EQ is effective at best only at very low frequencies where the interacting signals are effectively within 1 cycle difference.
> 
> EQ does NOT correct for non-minimum phase errors resulting from the interaction (superposition) of direct and indirect signals within the room.
> 
> There is good reason why the use of EQ is NOT sufficient to correct speaker-room interaction issues! (And one would be smart to investigate the reason why adjusting a frequency response with EQ can make the FR look flatter, while substantially exacerbating anomalous behavior in the system!!! If this is not understood, more research is advisable!)
> 
> My point was to direct one to a larger awareness of the behavior of sound within a bounded space viewed from the causal time domain perspective rather than from a derivative frequency domain perspective. With an awareness of this perspective, coupled with the tools programs such as REW afford one to view such behavior, and the additional tools we now have at our disposal with which to treat such issues, you will discover a much more effective arsenal of techniques and tools to more adequately affect the quality of sound in the room.
> 
> I am not here to debate this. It is an established fact (which was debated and reflectively settled in the mid-late '80s in professional and academic circles) that many may not yet be fully aware. Thus my purpose being to simply point this out and hopefully encourage more productive research.
> 
> And as has been mentioned, such a technique may potentially effectively be used to modify the character of the minimum phase direct signal emanating from the speaker, but the frequency domain response view does not provide a sufficient degree of insight into the behavior of the speaker-room interaction within the room. Such environmental frequency response anomalies must be solved in the time domain.


I understand what you're saying but I think this goes well beyond the scope of corrections of 99.9% of most listeners will ever have the tools to correct for, let alone comprehend what they are doing. Nobody's trying to argue with you or refute what you are implying, either. Besides, wouldn't a non-LTI or non-causal room/audio interraction be scary  just kidding.

Also keep in mind the majority of REW users come in, EQ their sub flat or boost where desired, and call it a day. I'm sure a few people do fullrange EQ as well but they are the minority. Unless there's a piece of hardware or software to do it automatically for them, they won't even try to understand things like a room's impulse response or the waterfall plots that REW shows them. Let alone try and correct for them...


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## SAC

fusseli said:


> I understand what you're saying but I think this goes well beyond the scope of corrections of 99.9% of most listeners will ever have the tools to correct for, let alone comprehend what they are doing. Nobody's trying to argue with you or refute what you are implying, either. Besides, wouldn't a non-LTI or non-causal room/audio interraction be scary  just kidding.
> 
> Also keep in mind the majority of REW users come in, EQ their sub flat or boost where desired, and call it a day. I'm sure a few people do fullrange EQ as well but they are the minority. Unless there's a piece of hardware or software to do it automatically for them, they won't even try to understand things like a room's impulse response or the waterfall plots that REW shows them. Let alone try and correct for them...


I agree with the fact that many may not pursue actions more than simply trying to optimize the direct signal. For this group EQ may be the solution they need. But I would disagree in that MANY here are either considering or actively attempting to address speaker room interaction issues and are considering absorption and diffusion treatments while detrimentally restricting their view to the limited perspective provided by the frequency domain.

And not knowing the degree of awareness nor the full scope of the intended use, my purpose was simply to attempt to make folks who may not be intimate with the issue aware of a balance regarding pros and cons of various approaches and to introduce those who may not be intimate with alternative perspectives an awareness that there are much more effective methods of both analysis and treatment available if their needs extend beyond the narrow confines of what EQ will solve - depending of course upon the nature and scope of the issue to be resolved.



Dasher said:


> To be honest_ I don't even understand what your talking about_ so I guess I'm not to worried about time domain issues?.
> .........................
> 
> It seems to me you really went out of your way to make yourself sound intelligent. Unfortunately your rant was so boring I couldn't finish reading it. I'm happy however that I managed to fill in a couple of hours for you.


"...couple of hours" and a "rant"? :laugh: The entire 'dilemma' didn't take more than at most 10 minutes to address, as I, unlike some, DO know to what I refer. But hopefully others will become a bit more aware of the limited appropriate use for EQ and also of the additional available options beyond simple EQ provided by tools such as REW, as that was the simple intent of the reply.

Best of luck in whatever you are trying to accomplish.


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## Zeitgeist

JohnM said:


> The MiniDSP is a better solution than the BFD for that. The "Advanced" MiniDSP plug-ins can import filter coefficient files generated by REW.


The only reason why I'm still running a BFD is because I haven't shelled out the cash for the 4 that I'm going to need... (Going active on LCR).

The BFDs can be had for $50.. cheap. 

But, the $100+ for the MiniDSP *IS* a great deal compared to any of the other DSP solutions that I've seen.


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## Dasher

Ok guys thanks for all your help. Considering I only need one I think I will go for the mini.


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## Mika75

Parametric digital equalizer (with digital in/out)...

On page 2 of the above thread comments by Chris/WmAx regarding phase correction.


> I'll tell you... I don't think phase correction is a big deal. The inverse phase change when you apply a correction to a LF mode with a normal parametric EQ is actually correcting the initial phase modification; because the room modes are a minimum phase phenomenon under about 80Hz or so in a regular sized room. The frequency response anomaly and phase are directly related to each other, so correcting it results in correction. And as far as the phase error the crossovers in the speakers themselves create; this is non-consequential according to the credible research that tested for audibility under different conditions/environments with many trained listeners. The only way to get really high quality correction in the 100-300Hz band, is with proper room acoustics treatments, and of course, the 80 and under band corrected with EQ is only good in a very limited sitting position.
> 
> It does take a while to correct with a manual device like the DCX, this is true. But it does a very good job.
> 
> -Chris
> __________________
> Dedicated to improving the real[quantifiable] parameters of sound reproduction.


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## Dasher

I have just thought of another question I am hoping you guys can advise me on. Balance v's Unbalanced on the miniDSP.
I have your stock standard amps, i.e. no pro stuff. Do I need to get Rev A or Rev B? Does anyone know?


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## terry j

onya dasher

look, I might agree that SAC can type like no-one else!, but sheesh, maybe open your mind a bit?

Hey, you come on (with how ever many posts you have) ask for help, and already start to bite the hand that feeds you?

I'm gonna back SAC on one _very_important_point.

Time domain.

Run around any audio forum you care to name, they'll ALL talk about FR. Fair enough.

But try to get time into the picture?

good luck.

(to all) just one manifestation..run an FR, save it.

Delay the subs (mains whatever, don't care) by however many ms you want.

Run the sweep again.

Now overlay the two. You wanna fix the obvious (time) differences with eq? most will. Enjoy the less than optimum setup.

But hey, go the way you want eh? Makes one wonder why you bothered to ask in the first place.

Having said that, maybe at times his delivery might be a tad dense. But it could pay to at least try to understand.

more for others than you really.


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## Dasher

Terry,
I understand it may seem that I tried to bit the hand that feeds me, however.....
My post on this forum was to find why more people used the BFD rather than the MiniDSP, feel free to debate the merit of each until your heart is content.
If others feel it necessary to debate a different issue then they should start a new thread.

Cheers


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## terry j

Ok then, 'so what are the max time delay/increments available in these units?'

I'm interested in that if people know


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## keyboard

I'm trying the miniDSP. i'm in build stage.
Will report when done.:sneeky:


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## Dasher

I received my MiniDSP today. I only ordered it over the weekend, great shipping.
Anyway I haven't had much time but it looks to have a max delay of 7.5ms with increments of 0.2ms.


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## terry j

thanks dasher, if that is different once you get to learn it let us know yeah?

cheers


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## Dasher

Hi Terry,
I have had a bit more of a play with my new toy and 7.5ms looks to be it.
How does it compare to others?


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## terry j

hi dasher, never used the FBD, only the dcx years ago. It should be easy enough to look that up or have someone answer that for you (both devices)

is the 0.2 ms increment correct?


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## Dasher

terry j said:


> hi dasher, never used the FBD, only the dcx years ago. It should be easy enough to look that up or have someone answer that for you (both devices)
> 
> is the 0.2 ms increment correct?


Yep, as near as I can tell the 0.2ms is correct.


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## penngray

terry j said:


> hi dasher, never used the FBD, only the dcx years ago. It should be easy enough to look that up or have someone answer that for you (both devices)
> 
> is the 0.2 ms increment correct?


Hey Terry 

Yes, I own both!!

The answer is simple. People need to realize that the MiniDSP allows for complex filters. We can pretty much throw out the idea that the GUI screens tell us the MiniDSP's complete functionality. Those GUI screens with pretty buttons, sliders, etc are just to make it simple. I will have to search the MiniDSP forum for the answer but to assume delay is X ms because that is what the GUI says is not the right way to look at the MiniDSP. Example, The GUI also use to only got to 20Hz but with BiQuads we can customize a filter to do things at 5Hz too.


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## mechman

Thread re-opened. Posts removed. Be mindful of the forum rules. Particularly this:



> *Please be polite, courteous and respectful of other members, as well as all products and services discussed. There is no need to be condescending or overly critical, not everyone will be as smart as the next person. If you can help, please do so, but remember, we all start learning somewhere and none of us are perfect. If you are the home theater, audio or video aficionado king daddy audiophile, we are glad to have you around, but please be humble and considerate to those of less fortunate knowledge. If you call a member dumb, stupid or an idiot (or anything resembling those) you will be on your way to being banned. Something to remember is unless we are the smartest human being on the planet, there is always going to be someone smarter than us... and we are always going to be "less" smart than at least a few others. Therefore, if you just absolutely must call someone stupid, consider looking in the mirror and go at it all you want... but keep it off this forum. *


:foottap:


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## ernperkins

A few items:

- The miniDSP's time delay resolution is 0.02 msec, not 0.2 msec. This provides a resolution of 0.27 inches when using time delay to compensate for different acoustic centers of speakers. Or thought of another way, 0.02 msec gives a resolution of 18 degrees of phase compensation when designing a crossover point at 2500 Hz.

- Hifi Zine has done a nice series of articles about the miniDSP. One that might be interesting to this thread is "Subwoofer equalization and integration with the miniDSP 2×4". Unfortunately I can't include the link since I have less than 5 posts. Google will suffice!

- As mentioned earlier, miniDSP has a new set of SW plugins (the "advanced" series) that allow you to program the filters directly using Biquad coefficients. This would be of limited use except that REW can automatically generate these parameters. This provides a "semi-automatic" method of EQing a room if desired. YMMV.


Regards.....


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## Moonfly

penngray said:


> Is this where I say Im just not worthy?
> 
> I guess this needs to be repeating.....
> 
> 
> 
> 
> The OP pretty much summed it up. I with him and you can consider us dumb/myopic individuals all you want. Im okay with it because there is a 97% probability that I have so much more then you
> 
> To the the OP. THe MiniDSP is an amazing product for EQing subwoofer designs.
> 
> To all others "gleaning" again proper subwoofer design requires an EQing product at this time the MiniDSP has more functionality then even the DCX2496 without the DCX noise levels. You first need to design a sub that matches your goals then you need to consider all the room issues. Do not be fooled by Audyssey, anti-mode type products, do not be fooled by measurements seemingly showing incredible differences in decay times. People never scale or EQ the comparisons properly in the first place so the comparisons are always skewed. Ultimate bass response does require multiple subs, broadband absorption, etc. There are experts out there that can help you without being condesending.


Dont be fooled by Audyssey?

Can I assume you have then amassed some data proving Audysseys failings, and if so can we see them. I have used Audyssey many times on many different products and have independently measure the before and after results. I have always found it consistent and reliable, but you do have to use it properly.


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## Zeitgeist

Moonfly said:


> Dont be fooled by Audyssey?
> 
> Can I assume you have then amassed some data proving Audysseys failings, and if so can we see them. I have used Audyssey many times on many different products and have independently measure the before and after results. I have always found it consistent and reliable, but you do have to use it properly.


I like Audyssey and think that it works pretty well. The pro-calibration give more control and flexibility over the "out of the box" solution - and it's fun to play with.

However...... I think Audyssey (and most other quick auto EQ) have it's limitations in EQing a sub (It's a very very difficult task).. and while it's not terrible, I think that it's a little aggravating that the pro-calibration creates graphs that somewhat misrepresent the true response. They're very smoothed and do not represent what REW would show.

There is going to be some performance that simply can't be achieved without a standalone EQ. And regardless, even if Audyssey (etc) gets the response flat........ that may not be desired. I personally like the "hard-knee" curve a lot more than flat.


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## Moonfly

Audyssey does what it does, but IMO it does exactly what it sets out to do. The more help you can give it before hand the better the results, thats a given and I always work to that premise. I always aim for a flat response, so its perfect for me in that respect as well. If you dont like flat then it isnt really a failing of the software, its just aiming for the excepted equilibrium. 

Audyssey isnt the be all and end all, but if you want a flat response then I dont think there is a much better solution out there. If you dont like a flat response, you can easily use Audyssey and then implement some further eq to achieve what you want, and in many respects thats exactly what you would have to do anyway if you want to tinker.

I agree the graphs it produces are far from accurate, but if you dont understand graphs or arent that interested in them, which describes the majority of auto eq users anyway, then it doesnt matter. If you do know your stuff then those graphs wont fool you so is that really that big of an issue. For me personally it isnt. I have used REW to see if Audy is doing what it should and it pretty much does every single time, and to be honest I dont think one can ask much more of it than that, especially if you have got it free with your AVR anyway.

No doubt people will disagree with me, which is fine, but thats my personal opinion. If however someone chooses to essentially rubbish it, I would like to see the evidence by which that analysis was obtained. Many people say things, but few can actually back them up IME.


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## Zeitgeist

I agree. It does what it set out to do. I've read lots of debates about whether people like it or hate it - but that's really irrelevant. 

Ironically after researching what other options there are out there - there isn't a whole lot. I don't think that the high-end market (aka custom) takes Audyssey seriously and yet there aren't many options out there - rather than standalone (QSC, etc) DSP solutions for EQ.

But back to the original topic... My guess is that most people are happy with no EQ, happy with Audyssey's "flat" or are using other cheaper EQ.

I think that MiniDSP is definitely growing in popularity due to it's flexibility power and low price. If you don't get the results you want with Audyssey or whatever - MiniDSP is a strong option.


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## Moonfly

I think that even if you are an Audyssey user, the mini DSP will only help improve your system. If your a DIY'er then it would be of even more use to you. EQ'ing your sub manually with the mini DSP first will get better results from Audyssey so either way I would recommend anyone using something like that in their system personally.


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## Zeitgeist

Moonfly said:


> I think that even if you are an Audyssey user, the mini DSP will only help improve your system. If your a DIY'er then it would be of even more use to you. EQ'ing your sub manually with the mini DSP first will get better results from Audyssey so either way I would recommend anyone using something like that in their system personally.


Seaton Catalyst is a good example of a commercial design that has a DSP built into the amp - so that it's response is well EQ'd out of the box.. before starting with Audyssey.

Makes sense.


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## Moonfly

It certainly does, and more and more products are coming that way now. One could hypothesize that its the future :bigsmile:


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## bginvestor

I'm jumping into a minidsp project. I plan to use my iphone as a music server and go through a Cambridge id100 to the minidsp. Purchasing the minidsp combo which includes the digital card, dsp card, and amp card. It will have a digital signal through to the mid range drivers. Will be interesting..


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## bginvestor

SAC said:


> Either will work for EQing the direct signal, but neither are effective in addressing the non-minimum phase issues presented within the room caused by the speaker-room interaction of direct and indirect signals.
> 
> In other words, this is NOT an effective comprehensive room-speaker interaction treatment. For that you need to be looking and solving issues in the time domain. Hence tools such as the ETC response and the surgical use of signal alignment, absorption and diffusion.
> 
> It all depends on what problems you imagine the treatment to address.


I am interested in learning correction techniques using the time domain. Is there any website links that provide introductions to the theory? If no, any good book references? Looking for applications in a room and/or car audio environments. thx.


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## SAC

PM me and we can arrange to more easily talk interactively via voice chat or by phone (if you are in North America). 

I have Quite a bit of material and we can go into as much or as little detail as you desire. I have 20+ years experience using the measurements, so I am sure we can get you up to speed quickly and focus on techniques that are appropriate to your specific applications.


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## bginvestor

SAC said:


> PM me and we can arrange to more easily talk interactively via voice chat or by phone (if you are in North America).
> 
> I have Quite a bit of material and we can go into as much or as little detail as you desire. I have 20+ years experience using the measurements, so I am sure we can get you up to speed quickly and focus on techniques that are appropriate to your specific applications.


Excellent. I will send PM. Thank you.


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