I didn't see (or didn't recognize) a good answer to the OPs questions about their odd sim results. Can somebody please outline the answer again.
BTW, I am about to shortly try entering the DSP world, perhaps with a 2x8 miniDSP for my tri-amped system. But I can't say as I've seen any satisfactory and comprehensive sets of distortion test results for these gizmos. Beats me why saying "it's digital!!!" should be good enough certification? After all, at least two stages aren't digital (the input and the output stages, eh), not to mention creepy steps like A/D and D/A conversions.
Ben
BTW, I am about to shortly try entering the DSP world, perhaps with a 2x8 miniDSP for my tri-amped system. But I can't say as I've seen any satisfactory and comprehensive sets of distortion test results for these gizmos. Beats me why saying "it's digital!!!" should be good enough certification? After all, at least two stages aren't digital (the input and the output stages, eh), not to mention creepy steps like A/D and D/A conversions.
Ben
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Hi bentoronto,
Regarding your 1'st statement about my original forum question. I gained enough data (through everyone's post contributions) to make an educated decision as to which approach would be best for what I've been wanting to accomplish, which was to "drop the f3" from 43hz to around 30hz. I couldn't do it using an acoustic approach e.g., increasing sealed box size, stuffing... However, I was able to move it downward with an "electrical" alteration, hence... miniDSP.
In your post, I take it that you're having some concern wrt the quality of the analog/digital/analog signal, processor clarity? As far as distortion ratios, I cannot advise. But, since I've already "pulled the trigger" on the "miniDSP" 2x4 platform (w/miniDC isolator "car audio accessory"), along with the 2.1 Adv. stereo crossover plug-in, I can tell you that if there is any measurable thd, "It's inaudible." So, don't let that be a determining factor (implement w/ confidence!), it'll sound just great no matter what the application!
rigtec, best!
rigtec - nice to learn you are happy.
But I'd still like answers to my two questions:
1. Why did the sim results seem odd?
2. What are the distortion and other performance specs for say, a miniDSP 2x4? (And I wonder why it doesn't seem to be of much interest to anybody?)
Ben
But I'd still like answers to my two questions:
1. Why did the sim results seem odd?
2. What are the distortion and other performance specs for say, a miniDSP 2x4? (And I wonder why it doesn't seem to be of much interest to anybody?)
Ben
I'm suprized that there isn't any information for you on "miniDSP.com"; tons of support there. I became a member the day that I put my "2x4" order in.
Perhaps my curiosity is getting the better of me... but, why is that particular data of such interest in your mind, seeing that this device has been reviewed with eminent impunity? Just wondering, no judgements.
rig (Greg)
Are you asking me just why I'm interested in seeing the objective quantitative performance measurements of these devices?
I looked at the miniDSP website and posed the question and googled.... One reviewer off-handedly mentioned favourable tests.
Seems a trivial exercise to do the usual lab tests. No special about the inputs or outputs.
Ben
Yeah I saw your post over there. I too performed a "forum search" on your behalf (just out of pure curiosity), with "no result"... wtf???
Thanks for your try. I re-posted my inquiry yesterday in the hardware forum at miniDSP.
I'd say that absence of critical reviews and objective tests is an astonishing shortcoming. Does it mean DSP advocates are "true believers" rather than sober tech folks?
In the usual parameters used by audiophiles, how linear are the A/D and D/A converters?
I have no good reason to believe these devices are especially deficient. On the other hand, I really like to see the numbers before buying something and committing to a major change in my hobby.
Ben
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Duly noted! There is also a fairly consistent propensity for some of their on-line written documentation to have important words left out of instructive data sheets and technical pages; "S'like doing a puzzle" lol! However, I know they're not there to appease my hypersensitive awareness, towards the improper use of the english language... "They live and work in Hong Kong!" 😀
Spoken like an "orthodox skeptic"! Now my pet peeve is when some well known audio equipment manufacturers use "tricky ricky" testing environments to bolster their products published data sheet results; I've become a real pro at spotting a "wish list", as apposed to an actual fact sheet. But it is what it is, so I have no control of that... you just have be smarter than the advertisers give you credit for
P.S: So glad to know that just because their english/literature skills would seem to be questionable, it has no bareing on the quality, or the performance of their phenomenal product!
Well good luck bentoronto, I know you'll make the right choice!
rig
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Ben,
After a bit of investigation, found the chip used in the MiniDSP.
The Analog Devices ADAU1701 is well documented, the specs below are on just the first page of the 54 page manual.
From all appearances, specifications look quite good.
I have not researched other units using the ADAU1701, but if my memory is correct it is used in some pretty "high end" stuff.
Although A/D D/A was sketchy (lousy sounding) on the first cheap DSP I purchased in 1992, seems good sounding D/A are pretty ubiquitous now.
P.S. Found the chip description in a review by a guy who hates A/D, but after a while he wrote that the MiniDSP beat out all the high end analog crossover stuff he was using.
Art
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Art - very nice of you to go to the trouble of finding the write-up. Alas, I am at something of a loss to translate their terms into those I am familiar with. Analog Devices has umpteen other audio devices that are spec'ed in familiar terms.
For example, the noise seems to be down 100dB. Below what reference? Does the noise floor stay down there? Yet the total harmonic distortion and noise are a mere 17dB worse (83 dB). Does that suggest low noise but big HD? What does that mean? Does -83 dB mean something evil but only further down than .001% (80 dB)? Compared to what reference level?
Since you need at least one A/D and one D/A conversion, what does that do to the levels in the total system?
The chip maker may have their own good reasons for using the nomenclature they do. But still it can be presented in terms of familiar audio levels, etc.
For sure, the infinitesimal distortion specs we expect from op amps (which use cosmic levels of feedback) are orders of magnitude better than the level at which any of us would be aurally satisfied. So, I don't think .5% HD would faze me (or anybody with a knowledge of speakers) - even if it horrified most others here.
Ben
For example, the noise seems to be down 100dB. Below what reference? Does the noise floor stay down there? Yet the total harmonic distortion and noise are a mere 17dB worse (83 dB). Does that suggest low noise but big HD? What does that mean? Does -83 dB mean something evil but only further down than .001% (80 dB)? Compared to what reference level?
Since you need at least one A/D and one D/A conversion, what does that do to the levels in the total system?
The chip maker may have their own good reasons for using the nomenclature they do. But still it can be presented in terms of familiar audio levels, etc.
For sure, the infinitesimal distortion specs we expect from op amps (which use cosmic levels of feedback) are orders of magnitude better than the level at which any of us would be aurally satisfied. So, I don't think .5% HD would faze me (or anybody with a knowledge of speakers) - even if it horrified most others here.
Ben
Ben,
1. It is a SNR, so 100 dB below ODBFS (I think).
2. Yes.
3.HD can't be much.
4.Does not seem evil to me, compared to 0DBFS (which probably is at least +4 dBM or dBV, I did not read the manual, as I already have 3 DBX DSP and am not presently interested in purchasing anything different).
5. They make it a bit worse, without doing the math, through THD + noise would probably be about -82, still less than .001, an order of magnitude less than the speaker distortion plus room noise.
6. It's suppertime.
Art
Hi weltersys,
WOW, What a treasure! How relentless you must have been to have discovered this wealth of "food for the mind". The best to you, sincerely
rigtec
WOW, What a treasure! How relentless you must have been to have discovered this wealth of "food for the mind". The best to you, sincerely
rigtec
Rigtec,
I spent about 10 minutes of "relentless" googling to discover the chip, longer to write about it.
Glad you find it useful.
Art
I spent about 10 minutes of "relentless" googling to discover the chip, longer to write about it.
Glad you find it useful.
Art
Sure hard to google-up any information on DSP distortion... at least that I can understand.
First, not all the garbage that comes out of a DSP is harmonically related to the stimulus tone. And that itself is a scary thought. So the THD+Noise isn't quite the same audible metric as ordinary "pleasant" HD.
Second, and this should have been obvious to all of us, the garbage increases with freq since high frequencies start to impinge on limits of sampling rate. So a single THD number doesn't tell us the whole story.
Moving forward on DSP distortion.
Ben
Ben,
DSP deals in 0s and 1s, there is no "distortion" once in the digital realm.
With the total THD and noise around -82 after both A/D and D/A (which can be distorted), it simply is below an audible threshold- whether distortion and noise is of the "pleasant" or "scary" variety does not matter if you can't hear it.
A jet engine is around 140 dB standing next to one on the runway, but when one flies by at 40,000 feet while I'm indoors, I can't hear it, so it simply does not concern me.
At any rate, don't take my word for it, I have never used a MiniDsp.
I have used many other types of DSP though, and distortion or noise have not been a problem with any of them.
At the price of a few concert tickets, why not just buy the MiniDsp, measure and listen to it.
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I am quite sure you don't want to remembered as the guy who wrote, "there is no "distortion" once in the digital realm"... and forgot to add the smiley! Those of us who teach or taught in computer science departments have all kinds of jokes about software shortcomings that we tell our students in the first lecture.
Nice you to try to set me straight. Genuinely appreciated and not doubtful of the gist of your comments. But just call me crazy empiricist (or skeptical consumer), I'm waiting for someone to dust off their old ABX boxes (blind test switch boxes) and do a test.
(Hey, like the rest of you folks, I'll be fooling with my miniDSP long before the ABX tests are done anyway.)
Ben
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Other than the A/D and D/A sections all that goes on in DSP is computing.
Although computers have limitations and problems, and software has shortcomings, I have never heard of those being called "distortion", but I never taught computer science 🙂.
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