Copper would be even worse at low frequencies. The only way copper provides any significant magnetic field shielding is at higher frequencies due to eddy current losses from skin effect.
If you don't understand it, then go to Magnetic Shield Corp's website and show me their copper shielding that you guys are claiming is better than high permeability ferromagnetic materials. Go on, show me. If copper is better, these people should know. Maybe you can email them and set them straight on the matter as they've obviously been doing it wrong all these years.
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"At high frequencies simple conductive shields are quite effective provided that the thickness of the shield is greater than the skin depth of the conductor used (at the frequency involved)."
Key word being "simple." Not that it is inherently better than high permeability materials. Because of absorption loss due to skin effect improves with higher frequencies for more conductive materials, you can achieve effective shielding at higher frequencies without the expense of much more costly high permeability materials like MuMetal. Doesn't mean that MuMetal of the same thickness wouldn't be more effective. Because of its lower electrical conductivity, it would be even more effective in absolute terms than copper.
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Whether something is needless depends on the perspective.
Bespoke shoes are a luxury for most, for some a necessity.
On a technical level, hogging out 40 is a waste, hogging out 400 is not, imo.
On a marketing level, neither of two is, all 40 hogs were sold.
Again, please look at the skin depth of copper at 60 hz... it's 8mm. We're talking in the context of a case machined out of a solid billet (goodness, that'd be awful with Cu), so it wouldn't be surprising if the Blowtorch's case is greater than 1 cm all the way around, which is right about the skin depth of pure Al at 60 Hz.
We're not talking material efficiency here...
Actually, the recipe for selling whatever to the unsuspecting public is both well known and confirmed by practice for the last 50 years or so. Hardly anyobody is still after making good sounds, almost everybody is in just for as fat a profit as they can squeeze out.
As for the many people, Christophe, bear in mind that say 99% of them have never heard better properly demonstrated to them, so they figure: why pay say €300 for Sennheiser HD 598 cans when a €20 of Dr Dres does the same job? Ask them do they really think a small FIAT does the same job as a Mercedes-Benz.
Many people find headphones to be fascinating if they normally listen to boom boxes or portable transistor radios. And they do, when you eliminate bass boom, room interferences and surrounding noise levels. All you need do then is let them heat up for Dr Dres and then give them a go with some serious headphones on an A/B basis, not becessarily with expensive cans, but with something like say Grado SR-80 cans, which are of solid quality for their price.
My g/f's oldest son paid $300 in Vegas for a Studio Wireless Red, an HD598 does half that amount.
Her other son of 17 has a regular Beats, and yells the N-word in his sleep.
The 3d is too cheap, he prefers to puke his cash in a KFC bucket.
All three amigos have a K1000 as reference.
Most people want to look up the cow's-ah in front of them.
The selection of what sounds best is everyone's personal choice. I mentioned the Senns HD 598 simply because I have them, and I came to having them by making rounds to every joint selling half decent headphones and listening.
The one thing I notice about headphones in general for reasons I cannot undestand is that somehow, even though they are in fact transdusers much along the lines of a loudspeaker, somehow the headphone drive is simply disregarded. The headphone damping factor is a dirty little secret nobody ever talks about. We accept the the amp must act on a loudspeaker's Q factor, but disregard the headphones. With that in mind, I developed my own discrete headphone amps, and as expected, I often encountered goblins. Sennheisers are often said to be great everywhere, but with relatively weak bass lines - come to listen to mine and tell me this is so, via the TT or the CD. Ditto for general overall drive capabilities. Give them some ooomph and many of them will make you deaf if you overdo it. In short, given a proper drive, just about every headphone sounds better than when driver by a power amp resistor voltage divider, whose only redeeming point is a very low inplementation cost.
Really, much the same thing as regarding loudspeakers, only on a smaller scale. I use MJE 15030/15031 power devices in a SEPP circuit, biased at 94 mA, so in fact, most of the time, I live in pure class A mode. I understand John also does omething along those lines, but if memory serves, he uses still more bias. Perhaps this si not so much a matter of actual need but of the shanging circumstances, many years ago there was a lot of headphones with a nominal impedance of 8 Ohms, but these days, it's rare to find any below 32 Ohms, and some (like Beyer) go as far upwards as 600 Ohms.
The one thing I notice about headphones in general for reasons I cannot undestand is that somehow, even though they are in fact transdusers much along the lines of a loudspeaker, somehow the headphone drive is simply disregarded. The headphone damping factor is a dirty little secret nobody ever talks about. We accept the the amp must act on a loudspeaker's Q factor, but disregard the headphones. With that in mind, I developed my own discrete headphone amps, and as expected, I often encountered goblins. Sennheisers are often said to be great everywhere, but with relatively weak bass lines - come to listen to mine and tell me this is so, via the TT or the CD. Ditto for general overall drive capabilities. Give them some ooomph and many of them will make you deaf if you overdo it. In short, given a proper drive, just about every headphone sounds better than when driver by a power amp resistor voltage divider, whose only redeeming point is a very low inplementation cost.
Really, much the same thing as regarding loudspeakers, only on a smaller scale. I use MJE 15030/15031 power devices in a SEPP circuit, biased at 94 mA, so in fact, most of the time, I live in pure class A mode. I understand John also does omething along those lines, but if memory serves, he uses still more bias. Perhaps this si not so much a matter of actual need but of the shanging circumstances, many years ago there was a lot of headphones with a nominal impedance of 8 Ohms, but these days, it's rare to find any below 32 Ohms, and some (like Beyer) go as far upwards as 600 Ohms.
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We had a documentary in France at the TV where they were talking about those headphones. If I remember well, they said it was Chineese product buyed on the shelf for less than 10$. They compared the price to similar headphones from the same manufacturer.
Waving flag for 'invented here'. Airbus have been doing that A LOT longer than boeing. It's not for economic reasons per say, it's for weight savings. the mill to carve out a wing from solid is an impressive beast.
The A380 has to be done in 2 sections and then friction welded.
I spent a lot of my early career working with things that needed to be machined from solid then silver plated and like the look, but no justification for audio. Mind you how many amps have bullet proof fascias, connectors hand hewn by virgins, then ribbon cable to carrry the signal inside!
I believe the Idea, here, was not question of sound, it is a fashion accessory.
A 'must have' for the young generation, a sign of 'belonging', like Iphone, with everything in the look.
It has to be high priced to be "hype", not too much for youth can afford-it with efforts.
If I remember well, Dr Dree was a rapper, and his first idea was to go in fashion suits, like all its brethren ?
This said, I don't understand why they don't tried to make decent sounding headphones in their way. After all, some are listening to music (?), while wearing-it ;-)
Notice too that, the sounds that those things are supposed to transduce is rap music. A boom box that you can carry on your head.
Exactly the same story with my son. I tried to convince-him to listen and compare to Porta pro.
Well, he said: yes, it sound a lot better, but it is not the headphone i'll like to wear in the metro. Question of look.
Well, after some months, he changed his mind. Now, all his friends use a... Koss Porta pro ;-)
Given the volumes involved, pennies on amortization costs.
Molds in China are cheap to get made and you can get phenomenal quality and finish if you look around.
Dr Dre's are a rip-off technically and sonically. Here is a classic case of 'brand equity'. But, they are also smart because the distribution and retail channels are well taken care off. Plus, they know their target demographic well - young males with with small brains, no appreciation of fine sound and too much testosterone.
As in all these things, it seems to me the greater the bs, the greater the ability to leverage outrageous, confiscatory pricing models.
Now John, what you are doing wrong is that you get involved in the technical minutae - JFETs, bipolar, Opamps and all that crap. Just go to China (Shenzhen or Guangzhou) and find a low cost manufacturer. Get them to put your name on the product and then sell it through the U.S. retail channels. You will need to wear a suit (no tie but top two buttons of your shirt should be undone), a good pair of sunglasses and look cool. If you need a contact over there let me know.
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