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New webpage on loudspeaker cables
The discussion on the new page has prompted me to do something I'd be
meaning to get around to for a while, and to (at last!) add some extra link buttons to the 'HFN' set of pages. :-) I have therefore now added link buttons to the bottom on most of the pages that are based on HFN articles. These should make it easier for readers to move to 'previous' or 'next' ones in any series. Should help people find details on one page that aid understanding others. Given later supply of 'round tuits' I may do some more linking for other pages, and perhaps in due course add a 'technical sidebar' page for some items that goes into detail of how results were obtained. I often already have these in rough note forms but omitted from published articles in HFN due to the density of 'hard sums' or the need for the reader to follow the details of the relevant engineering or physics. But they may be useful for some readers. Slainte, Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
New webpage on loudspeaker cables
On Fri, 07 Aug 2009 09:10:40 +0100, Jim Lesurf wrote:
Hi, I've just put up a new webpage that provides some measurements on the properties of a variety of loudspeaker cables. The page is at http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html It is an expanded version of the article published in 'Hi Fi News' a few months ago. Slainte, Jim Skin effect at audio frequencies?? Haven't you described this as resulting in about 0.02dB loss at 25kHz over near dc? hardly noticeable unless you're a Vulcan :-) At my age (50's) my auditory system is so shot I'm glad I can still hear sounds above the tinnitus. |
New webpage on loudspeaker cables
On Thu, 13 Aug 2009 18:08:53 +0100, Dave Plowman (News) wrote:
In article , Eeyore wrote: You have my 100% agreement again. Is Jim Lesurf one of those out-of-touch academics that never have to build a product that has to work in the real world ? I'll answer for Jim in case he's modest. He designed a variety of amps for Armstrong which were very well regarded. I had experience of a tuner amp which sounded very good indeed. That may be so but all the guff about skin effect at audio frequencies is only of relevance to the sport of measurement - you'll never hear the difference. What well regarded commercial designs are you responsible for? |
New webpage on loudspeaker cables
On Thu, 08 Oct 2009 10:11:47 +0000, Brian Gaff wrote:
Ahem, this debate seems to have been going on for more years than I care to remember. To me, the main reason why some cables do sound different is bad design of output stages themselves. After all, speakers are very weird loads and if an amp is going to sound different just due to cables then it does not bode well for how it will drive real speakers. I'd say there is some truth in what you say but alas I have never come across a situation where the substitution with bell wire of much heavier multi-strand in the speaker leads where I can hear any difference between the two and I have used some of the crappiest audio amps. Ducks behind potted plant. Brian |
New webpage on loudspeaker cables
On Sun, 16 Aug 2009 09:32:22 +0100, Jim Lesurf wrote:
In article , David Looser wrote: "Eeyore" wrote in message ... Perhaps you'd like to explain exactly how the techniques you have used to ensure unconditional stability are an improvement on those used by Jim in his designs for Armstrong. (a) I don't have the time. (b) It's commercially confidential. Yeah, yeah. Excuses excuses. Going off a tangent: I must admit I found (b) above quite interesting/ amusing. There does seem to have been a trend in recent decades for makers and desigers to feel that physics and engineering can somehow be kept 'secret'. A few decades ago makers of items like hifi amps and tuners where happy to let users have circuit diagrams and explain to people how their equipment worked. They were proud of what they had built, and wanted to explain its ingenuity. Indeed, in my exprience they generally felt that open discussions with other engineers about what they had done would help everyone to improve. And they had the confidence that they would have new ideas and improve as they learned. More recently there has been a tendency to treat circuitry as being a 'commercial secret', perhaps even extending to behaviour like removing the printing from some components so others can't read the part numbers. I even read reports some time ago of a well-known designer putting ball bearings into the potting of his output transfomers to stop anyone opening them up to see what he had done. Afraid that to me this behaviour seems to betray a lack of confidence in their work, and in their ability to have newer or better ideas later on, perhaps even almost paranoia in extreme cases. It seems odd to me as it seems like a belief that others are frantic to 'steal' their 'idea', rather than being quite capable of doing things for themself. Perhaps in some cases a form of self-flattery to think others would need to do so. I have often wondered if this obsession with 'secrecy' over matters which could usually be uncovered *if* some other skilled engineer with resources *wanted* to reverse-engineer what had been done is a factor in the growth of 'snake oil' as it feeds ignorance amongst users and may help technobabble to flourish. Perhaps this is a factor in the way users have been led to treat some designers and makers as 'magicians' who practice a magic art beyond the ability of mere mortals to understand. When I worked in audio I and other designers at other companies quite happily exchanged ideas, and loaned circuits to each other. I guess it may be very different now. If so, it may well impede the education of some designers as they will find help from their peers harder to obtain. My personal view is that if you buy something, then it is yours, and with that you should be entitled to have the info to allow you to understand how it works or alter it if you so prefer. So in another area my preference for Linux and the approach of its community to software. And in electronics, a wish for full technical onfo on any item I might want to buy/use. Perhaps this is the 'academic' in me wanting to understand things. Maybe it is that I object to being told, "we want your money, but you can only use the item, not be allowed to try and understand how it works." I've had various items of 'consumer equipment' which have broken and are then impractical to repair as the makers won't release info or parts. So there may also be what seems like a scam here to me, causing repairable or improvable items to end up as landfill. I wonder how many computers will end up as landfill as a result of people feeling "Must have Windows 7 to follow everyone else"?... ...but that is well OT. :-) So coming back on topic, the above does rather support my wondering if all current/recent amplifiers are as good as they *could* be if their designers/ makers were more open, and less fearful of others being able to study what they had done. Slainte, Jim I've seen instances where builders have rubbed off component markings. They are not very common though. What I'd like to say is this, I think that design today is more about fashion than practicality. Looks and form over function. You can see it everywhere. |
New webpage on loudspeaker cables
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:
Jim Lesurf wrote: Hi, I've just put up a new webpage that provides some measurements on the properties of a variety of loudspeaker cables. The page is at http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html It is an expanded version of the article published in 'Hi Fi News' a few months ago. What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the listening experience. I wouldn't want to buy an audio amp that could potentially do anything at 30mHz. It's madness. Ideally you want the gain to tail off at just above normal human hearing ~ 20kHz. It's not well known but ultrasonic sound at high intensity is capable of causing tinnitus (I'm talking power levels found in ultrasonic burglar alarm systems which I have repaired and found out from personal experience). And since when ( Fig 1 for example ) do you run a cable open or shorted as a valid test ? WHAT A COMPLETE HEAP OF MINDLESS JUNK ! You should be ashamed of yourself and run some REAL models. Graham |
New webpage on loudspeaker cables
In article , John
wrote: On Thu, 13 Aug 2009 18:08:53 +0100, Dave Plowman (News) wrote: In article , Eeyore wrote: You have my 100% agreement again. Is Jim Lesurf one of those out-of-touch academics that never have to build a product that has to work in the real world ? I'll answer for Jim in case he's modest. He designed a variety of amps for Armstrong which were very well regarded. I had experience of a tuner amp which sounded very good indeed. That may be so but all the guff about skin effect at audio frequencies is only of relevance to the sport of measurement - you'll never hear the difference. I presume you missed the comments I made about this at the time. However the page had two overall main purposes. 1) To investigate cable+load combination behaviour at ultrasonic/RF frequencies that can, indeed, affect amplifier behaviour in ways that can be both audible and measurable at *audio* frequencies. e.g. problems with lack of stability into some presented loads. 2) To use the values obtained by the ultrasonic/RF measurements as one of the methods to work out the cable capacitance, inductance, etc. Which again can affect the results at audio frequencies in ways that can be both audible and measurable. Did this because attempts to measure short run C and L values are tricky at LF and also prone to the problem that the values do alter with frequency. So did measurements by various methods to obtain cross reference and reliability. Skin effect was included, because internal impedance does indeed influence behaviour and so is part of the above. In most cases 'skin effect' isn't likely to be audible. But the difference it makes from one cable design/length/load case to another might upset one amp audibly, but not another. So it can matter. If you have not already done so, I'd recommend you read the previous articles in the series (hint: this one was 'cables3' :-) ) as that may help make these points clearer. The 'cables3' article *is* part of a series, so just reading the one page is a bit like reading one page of a book and then complaining it doesn't make sense (because you don't know the context). Slainte, Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
New webpage on loudspeaker cables
In article , John
wrote: On Sun, 16 Aug 2009 09:32:22 +0100, Jim Lesurf wrote: I have often wondered if this obsession with 'secrecy' over matters which could usually be uncovered *if* some other skilled engineer with resources *wanted* to reverse-engineer what had been done is a factor in the growth of 'snake oil' as it feeds ignorance amongst users and may help technobabble to flourish. I've seen instances where builders have rubbed off component markings. They are not very common though. What I'd like to say is this, I think that design today is more about fashion than practicality. Looks and form over function. You can see it everywhere. I would agree. However I've often found both good, and bad, designs in terms of performance. And the responses I got to the page(s) you mentioned did support my impression that some makers/designers may still not ensure their designs are unconditionally stable. Slainte, Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
New webpage on loudspeaker cables
In article , John
wrote: On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote: Jim Lesurf wrote: Hi, I've just put up a new webpage that provides some measurements on the properties of a variety of loudspeaker cables. The page is at http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html It is an expanded version of the article published in 'Hi Fi News' a few months ago. What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the listening experience. I wouldn't want to buy an audio amp that could potentially do anything at 30mHz. It's madness. Then you may have a problem to worry about. :-) Many of the gain devices in audio power (and pre) amps have gain at frequencies reaching up into that region. As a result *unless* the designer/maker has ensured unconditional stability and no other problems affected by RF loading, then changing the cables can affect the amplifier behaviour. If you wish to avoid the 'madness' then you have two choices... 1) never buy or use any audio amplifiers. or 2) only buy ones where the maker/sellers/reviewers have told you the unit is unconditionally stable and that behaviour is unaffected by RF loading. Otherwise you have just 'plug and prey' to go by. :-) Ideally you want the gain to tail off at just above normal human hearing ~ 20kHz. It's not well known but ultrasonic sound at high intensity is capable of causing tinnitus (I'm talking power levels found in ultrasonic burglar alarm systems which I have repaired and found out from personal experience). The problem, alas, is that the amplifier is still connected to the load, via the cables, at higher frequencies. The gain devices will have gain at these frequencies. And the length and type of cable will affect the load presented to the amp at RF. Change the length or type of cable, and the load seen by the amp will change. So if the system isn't unconditionally stable then it may misbehave without you explicitly trying to put into it frequencies above 20kHz. Chances are, anyone who has spent long designing audio amplifiers will have seen them oscillate or otherwise misbehave at such frequencies with some loadings. And that can then affect the audio behaviour. I've certainly witnessed this. I have also seen someone puzzled by an amp having high levels of distortion *at audio frequencies* that appeared with some speakers but not others. Only to find later that using an oscilloscope with wider bandwidth showed that the amp was producing bursts of oscillations in the region well above 1MHz with one load, but not another. He could not see the oscillations with the first scope he used, so was baffled by the behaviour. The better scope showed the reasons and helped him fix the problem. I have also seen this with a real-world commercial amplifier that had a high reputation and sold at a fancy price. So if the designer/maker don't understand this and take care, it can get out into the home. Slainte, Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
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