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Pro Audio Mixers, mics, outboard, monitors, headphones

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Old 4th September 2008 , 11:12 AM
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Default Headphones and resistance.

I'm looking at getting a pair of DT100s for university but they come in two different resistances; 16 and 400ohms.

What's the difference between the two? I would be using mine for mixing on a laptop and possibly monitoring in a studio.

Please help! I need to buy them asap so I get them before I go to university...
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Old 4th September 2008 , 12:40 PM
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The low impedance headphones at 16 ohms may be directly plugged into the headphone jack routinely found on recording and playback equipment. The high impedance 400 ohm heapdhones are more useful in studio installations.
The 400-ohm models are more rugged than low impedance models in that the higher resistance coils are less susceptible to burn out than low impedance models.
The advantage of high impedance headphones is that they can be used with almost any amplifier output without any risk of being damaged by overload. However, they may be not loud enough with some portable recording devices.
Low impedance headphones will sound louder with devices with low output voltages such as portable MD recorders, possibly your laptop etc.
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Old 4th September 2008 , 01:18 PM
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So the best option is to go for the 16ohm ones?

I'm still unsure as to which is best!
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Old 4th September 2008 , 01:44 PM
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If you wanted them purely for mixing on the PC then I would say the 16 ohm headphones would be the best choice. However, if you want them for the PC mixing and potentially for the studio too then 400 ohms is the best bet. The 400 ohm headphones will produce less volume on the PC than the 16 ohm headphones. I do not think this should be a problem since the DT100's are high sensitivity and should be able to produce decent usable volume on the PC whether you have the 16 ohm or the 400 ohm version.
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Old 4th September 2008 , 02:30 PM
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The 'less volume' issue with the 400 ohm headphones is the only worry. 16 ohm headphones can be used at home mixing on the PC and for monitoring in the studio too. The 400 ohm heapdhones will give you more flexibility in a studio situation - eg, more than one high imepdance pair of headphones can be connected to the same output simultaneously.

So to summarise;
16 ohm - will work well for your PC mixing and will work in many but not all studio settings.
400 ohm - will work for your PC mixing but will sound less loud than the 16 ohm headphones. Will handle a wide range of studio settings.

If you wanted to go for the 400 ohm headphones but found they were too quiet on the PC then there would be a not too expensive fix - use a headphone amp;
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Old 4th September 2008 , 05:52 PM
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I agree with everything posted above...I'd go with the 400ohm set just because I think it offers more options. All you'd have to do if they're too quiet is add a headphone amp. Cheap solution.

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Old 5th September 2008 , 06:12 AM
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16 Ohm phones make no sense to me (and 8R even less).

You cannot plug them into a device that needs a 16R load (and what does theses days apart from valve guitar amps?) because that would be dangerous to both phones and ears* and the amp noise would be intolerable.

Low Z phones can only be used on "hi fi" amps that have an attenuated jack outlet and they are too low for most iPod type gear (no harm, but probably more distortion).

As has been said, 400 Ohms will be quieter on some sources but fine on mixers and such and peeps tend to listen too loudly than is safe anyway!

*Oh! and valve amps too because they would O/C p.d.q.

Dave.
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Old 5th September 2008 , 06:52 PM
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I'm guessing that this goes back to the good old days when winding the very fine wire required for higher impedance headphones was more costly than winding fewer turns of the thicker wire used in low impedance coils. (I remember a previous employer buying a machine for winding coils as used in very small speakers, like telephone handsets - it was one of the finest wire winding machines in the UK at the time, and cost over 1 million). So to keep the price down for domestic users, (who generally would be plugging into a hi-fi amp), 8 ohms was fine. Also, because the amp output had to have attenuating resistors in series with the headphone output, there was no risk of the user shorting the amp outputs by using headphones with dodgey wiring. (Hi impedance headphones badly wired = goodnight output transistors!)
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Old 5th September 2008 , 08:04 PM
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Evening Stagesound,

I have a different theory. All hi fi amps were once valved. How do you connect a high sensitivity h/p to a valve output stage? You don't! You would have to arrange a load of the correct resistance and power rating and an attenuating network for the phones in most cases.

The advent of the transformerless transistorised amplifier which could run into an O/C made it possible to have a simple switching jack* with something around 100R to provide attenuation. At some point some buffoon saw that transistor amps "liked" 8 Ohm speakers so the first "domestic" headphones were 8R! Once this daft value became something of a standard most mfctrs followed like sheep, despite castigation in the technical audio press at the time (600R AKG K50's worked beautifully on most amps if a little quiet on some).

*Peter Walker of Quad fame would not have any kind of switch in a speaker circuit. He said he had never found one that did not oxidize and create distortion.

My earlier comment about an "optimum" impedance was to effect that the more turns of finer wire you put on the more dc resistance you create and apart from copper loss the thing gets closer to a low pass filter (L and R going up). No doubt with different pole architectures and magnet materials, headphone design is a black art indeed!

Oh! And just in case not everyone has got my drift, headphones with an impedance below 32 Ohms are a technical cockup! ( and I don't have much time for 32's!)
Dave.
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Old 5th September 2008 , 08:15 PM
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Wow Dave. You lost me at "transformerless transistorised".

Frank
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Old 5th September 2008 , 08:17 PM
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I think I have come to know you better than that Frank!

Dave.
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Old 5th September 2008 , 08:19 PM
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Quote:
Originally Posted by ecc83 View Post
I think I have come to know you better than that Frank!

Dave.
Oh no my fine British friend, when it comes to the truly technical I know who the real master is...and it ain't me.

Frank
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Old 5th September 2008 , 09:33 PM
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Dave - I'm not old enough to remember valve amps!
Out of interest, how did they protect both the user from deafening himself (in the absence of attenuation), and the amp from being damaged when said user unplugged the headphones?

Don't you think production cost might have been a factor?

How important is the L & R of the headphones when they are being driven by an amp through an attenuator, rather than through a dedicated headphone amp? Presumably the attenuator resistance does terrible things to the damping factor, but is this of any bearing, given the "stiffness" of the environment?
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Old 6th September 2008 , 06:12 AM
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Morning Stagesound,

They didn't! Valve amplifiers did not have headphone outputs. Production cost would certainly have been a factor, look at what is required...

Two 15Ohm (all decent speakers were 15R) power resistors rated 20-50W, a metal case to put them in, switching to effect the change over*. And remember, this was at a time when the distaff side held even more power in the home than today! What a man did in his shed was his buisiness but "don't bring your OXO tins in here!" And to what end? There were very few decent headphone about save in studios and they were not available, AFAIK to the common man. Furthermore, listening to music was an "event". Dinner done, cat fed, kids in bed, at 9.30 you could settle down for a hour or two of Bach or Mantovani! The idea that you went about wired all the live long, was totally alien.

Damping, ha! Sorry, very old argument. To be of much use you would expect an amplifier to have a source impedance of better than 1/10 of the nominal transducer ( good valve hi fi, Zout <1Ohm, bog standard transistor, <1/100Ohm), now the sort of equipment that "studio" phones are plugged into, will rarely have an o/pZ of less than 100R. The conclusion I come to is that electromagnetic damping is not a factor in H/P design and it is all done mechano-acoustically.

I just measured my Senny HD202's (superb HD 565's are broke, like me!) and although they have a nominal Z of 32Ohms (Senns' site info) they have a DC resistance of 33 Ohms! So, even if you had a dedicated, 1/1000Ohm o/p Z amp, any talk of damping those is bollocks!

Dave *Naturally, I built one!
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Old 7th September 2008 , 12:22 AM
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Dave - when I mentioned production costs, I meant the production costs of the headphone coils rather than the amps - finer wire being required for higher impedance, making them more difficult, and more expensive to produce. (Therefore in the early days, manufacturers went for the cheap option). Bearing in mind that early hi-fi headphones were generally fairly big, and cheaper ones at least, used "off the shelf" speakers as used in transistor radios, this may partly account for their low impedance "design".
Presumably once the trend was set, and hi-fi amplifier manufacturers designed around the available headphones, 8 - 16 ohms became accepted as normal.

A lot of low to mid range mixing desks used to work very well with low impedance phones, and couldn't produce nearly enough volume in high impedance ones. There are still a few desks which suffer the same problem. I remember my dissapointment on buying my first set of DT100's to discover that most of the desks I had at my disposal (Yamaha's, Soundcraft and a few other odd-balls) couldn't drive them - which is a pretty serious problem when you're mixing for FOH PA, and need to hear something on PFL!

I presume when you say about "studio" phones being plugged into equipment with o/p impedance of over 100 ohms, you're referring to stuff which just uses an op-amp with a 100 ohm resistor in series with the output to act as an attenautor for lo-z phones, and protect the output from short-circuits?

Most of the better quality desks I ever worked on had properly designed headphone circuits (though thankfully it's been a while now since I've had the soldering iron at one, so newer desks may have gone cheapskate!)
Circuits like this -
are down to around the 10 ohms of the o/p resistors. (This is a dedicated headphone amp rather than part of a desk, but the design's pretty typical).

I havn't done the maths re. the filtering effect of the resistors, coil resistance and inductance on the sound (again - thankfully I've given that up too!) - have you any idea what kind of difference it makes in practice?

It's interesting what you say about the mechano-acoustical damping factors in headphone design. I recently read a review (can't remember which phones, but they were something in the "more money than sense" league!), where the reviwers discovered that the initial tests sounded awful, but when they added extra foam to the ear cushions (why would you think of doing that when you're conducting a review???) the phones suddenly came to life and sounded brilliant. Presumably by allowing more air into the cavity, the mechanical damping became less "stiff", and affected the performance?

Re. damping factor, I always thought it was the resistive part of the speaker load, divided by the source impedance (where the source impedance is the sum of the amp output resistance, the connecting cable resistance etc.) In the crappy headphone amp designs which use series resistors, or in hi-fi amps which use attenuating resistors, this would make the damping factor figure really low - which can't be good! - right?
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