Why high (or low for that matter) impedance?

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dB Cooper

Why high (or low for that matter) impedance?
« on: 6 Dec 2017, 03:40 am »
Maybe this belongs in the Lab, and move it if so, but I'm wondering why a designer chooses a particular impedance. I kind of 'understand' that wattage is the square of voltage divided by impedance, and the power available from (let's say) a cell phone battery can't swing the volts required to really drive (let's say) a pair of 600 ohm Beyers, but may be able to deliver current into IEMs... I guess what I'm asking is, assuming a home stereo or headphone amp. why do some designers/manufacturers (Beyer and Sennheiser come to mind) continue to opt for high impedance, especially given the overall trend towards lower impedances that has paralleled the ascendancy of portable audio? What's the advantage?

poseidonsvoice

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FullRangeMan

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Re: Why high (or low for that matter) impedance?
« Reply #2 on: 6 Dec 2017, 04:11 am »
Why makers chose a such impedance I dont know, I suspect there are various factors on play, but a low impedance VC have more wire lenght usually 2 layers(on speakers) of flat wire and can stand more power than the hi impedance, some VC use aluminium or silver wire.

dB Cooper

Re: Why high (or low for that matter) impedance?
« Reply #3 on: 6 Dec 2017, 03:07 pm »
Not according to the article but I only had time to give it a quick skim (gotts go to work). I noticed they said a high impedance voice coil has (all other things being equal) a lower moving mass, so I guess transient response is one benefit of high impedance. I've actually owned 2KOhm (!) impedance headphones (Senn 414). Those were reportedly made using mic elements but I guess the 2K load was easy for the tube amps that were ubiquitous then.

adydula

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Re: Why high (or low for that matter) impedance?
« Reply #4 on: 6 Dec 2017, 04:13 pm »
It may be that headphone designers now look at all the dsp devices that their products could hook too...to sell the most stuff they have had to start looking at the devices to which they attach...iphones, android devices etc...

They want to make sure that the end user has a pleasant experience and the device will have enough power/volume control so the end user will be happy and NOT return them AND recommend to others to purchase.

Alex

dB Cooper

Re: Why high (or low for that matter) impedance?
« Reply #5 on: 7 Dec 2017, 02:41 am »
Fullrangeman, as I went back and read the article poseidonsvoice cited, the high-impedance driver has more windings but of extremely fine wire, with a  lower moving mass than a comparable low impedance driver (and apparently also has a stronger interaction with the magnetic field). I guess this makes sense.  :scratch: Aluminum is favored for its light weight, although Grado uses copper for all their vice coils, but that is probably a whole  different conversation.

FullRangeMan

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Re: Why high (or low for that matter) impedance?
« Reply #6 on: 7 Dec 2017, 03:29 am »
Fullrangeman, as I went back and read the article poseidonsvoice cited, the high-impedance driver has more windings but of extremely fine wire, with a  lower moving mass than a comparable low impedance driver (and apparently also has a stronger interaction with the magnetic field). I guess this makes sense.  :scratch: Aluminum is favored for its light weight, although Grado uses copper for all their vice coils, but that is probably a whole  different conversation.
Alu VC is used in pro audio drivers, in HPs dynamic drivers is all about thin copper or silver. About the driver impedance x lenght wire it depend on the wire gauge.

dB Cooper

Re: Why high (or low for that matter) impedance?
« Reply #7 on: 7 Dec 2017, 04:12 am »
Almost all Sennheiser headphones (excluding the low-end ones possibly) use aluminum voice coils (lower moving mass). Haven't looked at others. I don't see voice coil metals mentioned in much manufacturer literature (or reviews for that matter). I'd be interested in any data on this. Think I'll see what I can find on it.

FullRangeMan

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Re: Why high (or low for that matter) impedance?
« Reply #8 on: 7 Dec 2017, 05:56 pm »
Incredible I unknew this, alu is not a good sound wire as copper and silver.

BigChubby

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Re: Why high (or low for that matter) impedance?
« Reply #9 on: 9 Dec 2017, 04:58 am »
I'm a big fan of higher impedance phones based on my listening experience.  The trend however, seems to be going in the opposite direction.  I've seen most of the newer high-end phones have a Z below 50 Ohms.  I don't get it.  I've heard the argument that it's so the phones can be driven by smart phones, tablets and portable DAPs.  I must be missing the connection though as I don't see a typical smart phone user listening to his mp3s or AAC files with a big set of Focal Utopias on their head.

Then again, I ran across a discussion as to why Sennheiser HD-600/650s still sell so well after so many years.  Nobody seemed to really know, but being biased, I think it's the Hi-Z and open-back design.  Paired with an amp that has decent rails and the dynamics will take care of the rest.

Of course, that's just my opinion.

FullRangeMan

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Re: Why high (or low for that matter) impedance?
« Reply #10 on: 9 Dec 2017, 07:40 pm »
I must be missing the connection though as I don't see a typical smart phone user listening to his mp3s or AAC files with a big set of Focal Utopias on their head.
I have never see any also, they use the free IEM that came along w/the phone.

dB Cooper

Re: Why high (or low for that matter) impedance?
« Reply #11 on: 10 Dec 2017, 04:09 am »
I'm a big fan of higher impedance phones based on my listening experience.  The trend however, seems to be going in the opposite direction.  I've seen most of the newer high-end phones have a Z below 50 Ohms.  I don't get it.  I've heard the argument that it's so the phones can be driven by smart phones, tablets and portable DAPs.  I must be missing the connection though as I don't see a typical smart phone user listening to his mp3s or AAC files with a big set of Focal Utopias on their head.

Then again, I ran across a discussion as to why Sennheiser HD-600/650s still sell so well after so many years.  Nobody seemed to really know, but being biased, I think it's the Hi-Z and open-back design.  Paired with an amp that has decent rails and the dynamics will take care of the rest.

Of course, that's just my opinion.

According to the article linked by poseidonsvoice early in this thread (Thanks PV!), a high impedance design is harder (and thus more expensive) to make than a low impedance one. Since the public at large is deserting component audio systems, more and more headphones are being plugged into battery powered sources that can't swing the volts to drive a high impedance load effectively.

BigChubby, I think you're pretty much on point. Driven from a source with good damping factor, a good low impedance phone can sound just fine, but I figured there must be reasons that Beyer and Sennheiser have stuck with higher impedance all these years, so I started the thread to try and find out what those reasons are. As you point out though, the trend seems the other way. The HD700 came out at half the impedance of the 800, and now we see the same with the 660S. I guess they don't want uninformed listeners plugging HD800's into phones and blaming the weak sound on the headphones '("My earbuds play plenty loud, and these things cost HOW much???")