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64.13.14.96
In Reply to: RE: Measuring properties or changing operation? posted by Todd Krieger on June 25, 2009 at 12:05:34
"It isn't just the competence, or lack thereof of the designers. Home audio is one of those pathological cases which superficially seems trivial, and yet isn't. "
I don't think it's just home audio..... It's **all** audio....... If you think the stuff designed for the studio is of more competence, I'd kindly but strongly disagree. (I personally think Pro Tools is the single biggest monstrosity of a design ever conceived.) Just look at the horrible recordings that have been put out in recent time.
>Well, I don't have much exposure to that field but I think it's better, at least they are using balanced cables! The main reason I usually say 'home audio' is that that's what I'm familiar with.
"While almost anything thrown together by almost anyone will work, designing a product that really works well, i.e. to the point that it is effectively transparent to the ear, is another matter. Here are a few reasons that come to mind..
1. The lack of systems engineering.
-The home audio system topology wasn't designed, it just happened."
Systems engineering would force a home audio system to be of a "all in one" type design..... Unless every designer agrees upon what the system ought to be, this "lack" will go on indefinitely......
>Nah, I don't think so. The main thing that's wrong is the interfaces are poorly specified especially with respect to impedance and susceptibility.
I personally don't think this facet of engineering is any more of a problem than other facets of engineering.
>Boy I do, look at the stuff people hang onto their systems trying to get them to play well together.
"2. The lack of meaningful standards.
-To put it bluntly, it's not important enough to governments or industry."
It shouldn't be important to government, unless public safety is an issue...... (This is why we have UL standards, by the way.)
>It depends upon your view of government. Ours does have some such as FCC part 15, Europe has more. I've come to view some of the CE requirements as a good thing. It makes my job harder but really does result in a sturdier design.
I do agree in regard to industry...... But it would require an across-the-board agreement amongst many backgrounds, so even if such objective is sought, the chances for successful implementation would be very slim.
"3. Unusually wide bandwidth.
- Three to four decades of signal bandwidth is huge."
Not since digital audio has hit the scene. Bandwidth is limited to 22.05 kHz. And because of that, bandwidth in line and power amplification is no longer so important. So I strongly disagree here.
>On the outside that limitation reduces the bandwidth by less than an octave.
I also disagree in regard to bandwidth being a problem, unless it's so wide, it becomes susceptible to RF interference.
>The wide bandwidth makes the signal more susceptible to problems, especially due to passives such as skin effect and core saturation.
"4. In-band power.
- Having the 60Hz power supply and it's main harmonics where we hear is bad."
The only solution to this is battery power..... Jeff Rowland, a so-called "home audio" manufacturer, has undertaken such approach.
"5. Extreme user sensitivity.
- Reducing distortion to where you really CAN'T be aware of it is tough."
The user sensitivity has always been "extreme." The problem is too many in the design community are trying to convince the masses that associated discomforts should be tolerated to a degree or that the sensitivity is overrated. This is a big reason why audio design has been disappointing, in my humble opinion.
>Agreed.
"6. Conflicting design approaches.
- Nowadays this is less of a problem due to switchers and mixed-signal designs, but traditionally audio guys were clueless about RF and the major rules of thumb are in conflict. It's hard to both star ground and maintain a Faraday shield."
It's not difficult to make a star ground and Faraday shield...... It's that the latter has been deemed unimportant. Whether it is or not is subject to debate, but I will say the internal RFI generated from digital devices has rendered the Faraday shield ineffective. Although it should still be used on purely analog components like phono stages.
>I think it is. Basically you want the shield to ground to the box for RF but to the board for audio so if you do a good job you end up with a little of each but don't get the best of either
In regard to "clueless about RF", this is a problem for most designers across the board, not just home audio. The RFI generated by digital devices has changed everything.
Conflicting designs in itself is not an issue. The might both be competent, they might both be incompetent, and anything in between.
"Enough of that. It isn't trivial, there is no agreement on how good is good enough,"
Now here you hit on an issue. When in doubt, raise the bar, not go the easy route and think a lesser design might still fly. This IMO is a big problem in modern audio design. The bar simply hasn't been set high.
"what factors are important and how they are to be measured and weighted, or what the worst-case environment is that must be accommodated. The latter includes vibration, equipment interface, power supply, EMC and operators both deliberate and inadvertent. I'm trying to think if I know of anybody whose toddler HASN'T put a PB&J sandwich into the VCR."
Or oatmeal.
"But... I'm with Tom. The obvious goal is to design gear where all of these variables become, as much as possible, 'don't-cares'."
If the bar is set low, the variables do become "don't cares"..... The problem is there will be someone who will think the design is inadequate.
If the bar is set high, the variables becoming "don't cares" is next to impossible, in my humble opinion. This is why I think listener feedback is paramount to a good audio design. Until we can attain a more-complete picture from a measurements and specs standpoint, the best yardstick for performance will indefinitely be the collective satisfaction of the end users.
>Well, it just takes too long to consider every possible aspect of every design. At some point you have to develop a good feel for what you can get by with. Sometimes you are wrong which adds to your knowledge of what's important.
I don't know if this format will work Todd, I'm using a WP that I'm not familiar with so I apologize in advance if this is confusing.
Still using CDex? I'm really pleased that you tried it and that it worked for you, it does for me. Now there's something. You are a SW guy aren't you? Why does it sound so good?
Rick
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