[bLue_oNioN]

Hello,

The ER-4Ps have a sensativity of 109dB/mW and impedance of 27 ohms. The ER-4Ss have a sensativity of 109dB/mW and impedance of 100 ohms. Do note that the primary difference between the two simply lies in resistance -- an ER-4P can be converted to an ER-4S with the addition of an aftermarket adapter/cable.

The ER-4Ps are often said to be much easier to drive than the ER-4Ss. The ER-4Ss are also often said to improve much more with amping.

So, here comes my question.

V = I * R

Does this mean that at the same voltage, headphones with greater impedance should draw less current?

If so, why is it then, that the ER-4S, with its higher impedance, is considered the more demanding of the two? Or is the ER-4S demanding in a different way?

Lastly, why is the ER-4S with its greater impedance said to improve more than the ER-4P when amped?

Thank you very much for taking the time to clear this up for me!

 

[recstar24]

Quote:

Originally Posted by bLue_oNioN Does this mean that at the same voltage, headphones with greater impedance should draw less current? If so, why is it then, that the ER-4S, with its higher impedance, is considered the more demanding of the two? Or is the ER-4S demanding in a different way? Lastly, why is the ER-4S with its greater impedance said to improve more than the ER-4P when amped? Thank you very much for taking the time to clear this up for me!

1) Yes, headphones with higher impedance require and draw less current, yet need a higher voltage swing, voltage and current are indirectly proportional as you can see from the formula

2)Ive never understood this either, to me, lower impedance cans are much more demanding than higher impedance cans. Lower impedance needs the output impedance to be lower on the amp but it also needs to supply enough current to drive them, whereas with higher impedance you have more flexibility in the ouput impedance of your amp, less current is needed, and voltage really isnt an issue.

3)Not sure about this one, sorry!

 

[rsaavedra]

These technical issues also puzzle me. For instance, the Grado SR-60's are easily powered by any portable player, and they have 32 Ohm impedance. The Grado HP-2's I think have 150 Ohm impedance, supposedly they require tones of current to sound best

Yet the Senns with even higher impedance require is high voltage swings? So loads of current available are not so critical for the Senns?

yet they are for the middleman HP-2s (in impedance terms), yet tones of current are again not so critical for the even lower impedance SR-60's... which also doesn't really need high voltage swings

Also some headphones are very sensitive to the output impedance of the amplifier (e.g. has to be close to zero), whlile some other headphones are not so sensitive to that

More mysteries to me.

It seems there's more to all of this than just V, I, and R.

 

[bLue_oNioN]

Quote:

Originally Posted by recstar24 1) Yes, headphones with higher impedance require and draw less current, yet need a higher voltage swing, voltage and current are indirectly proportional as you can see from the formula

If the voltage applied varies along with the current, what relationship do they have then with the volume you set the player at?

The other two questions I posed still stand:

Why is it that the ER-4S, with its higher impedance, is considered the more demanding of the two? Or is the ER-4S demanding in a different way?

Lastly, why is the ER-4S with its greater impedance said to improve more than the ER-4P when amped?

 

[joelongwood]

Quote:

Originally Posted by rsaavedra The Grado HP-2's I think have 150 Ohm impedance,

The impedance is 40 ohms and sensitivity is 94db.

 

[saint.panda]

I hope this is correct....
Quote:

Does this mean that at the same voltage, headphones with greater impedance should draw less current?

Quote:

If the voltage applied varies along with the current, what relationship do they have then with the volume you set the player at?

You will have to base your calculations on power as the volume set on your player corresponds to a certain power output. Then, based on a headphone's sensitivity ratings (= volume output at a given power input) you can say that the higher impedance headphone will require higher voltage swings and the lesser impedance headphone a higher current output (as recstar said). See: Rane - Understanding Headphone Power Requirements http://www.rane.com/note100.html For example a sensitivity rating of 106dB means 106 dB SPL sound output at 1mW input.

Calculations example (assuming that 2 headphones have equal power requirements / sensitivity):
U = I x R, P(ower) = I x U =>
P = U^2 / R => U = (P x R)^(1/2) => higher voltage need for higher impedance headphone
P = I^2 x R => I = (P / R)^(1/2) = > higher current draw for lower impedance headphone

Since most headphones have more or less the same sensitivity ratings (around 100 dB/mW), the impedance/current/voltage thumb-rule holds true for most headphones.

Quote:

Why is it that the ER-4S, with its higher impedance, is considered the more demanding of the two? Or is the ER-4S demanding in a different way?

edit: I just read that the Etys have an internal coil impedance of 5 Ohm and they just add either 22 Ohm for the P version or 95 Ohm serial resistance for the S version. More resistance in series means more voltage drop along the wire (heat probably) and less power efficiency.

Quote:

Lastly, why is the ER-4S with its greater impedance said to improve more than the ER-4P when amped?

I don't know about amped but I think there are two issues at play here. Firstly, a portable player may not have enough juice to drive the ER-4S so an amp will alleviate this problem. On the other hand, the ER-4P suffers from a bass roll-off due to most portable players’ undersized output coupling capacitors that are to handle the current. An amp should also discard this problem. Otherwise, I don't see why one Ety should scale better than the other.


edit:
Quote:

Originally Posted by rsaavedra Also some headphones are very sensitive to the output impedance of the amplifier (e.g. has to be close to zero), whlile some other headphones are not so sensitive to that More mysteries to me.

Some threads of interest: http://www6.head-fi.org/forums/showthread.php?t=42444
http://www6.head-fi.org/forums/showthread.php?t=34154

 

[rsaavedra]

Quote:

Originally Posted by joelongwood The impedance is 40 ohms and sensitivity is 94db.

Gee I think I had read somewhere here on Headfi it was 150 Ohm, thanks Joe!

Thanks for the links and info as well Saint.Panda!

 

[BillC]

Quote:

Originally Posted by bLue_oNioN Lastly, why is the ER-4S with its greater impedance said to improve more than the ER-4P when amped?

This is supposition on my part because I don't know anything about the actual electrical characteristics of the Ety drivers but it makes sense to me. A coil of wire like one finds in a speaker driver is an inductor. A resistor and an inductor in series make a low pass filter. I would guess that Ety chose the resistance for the ER-4S to give the break point of the low pass where they wanted it for maximum performance of their drivers. Unfortunately, the resistive element dissipates power. For the 4P they dropped the value of the resistor which would lower the break point of the low-pass filter - in other words roll off the highs a bit. However, with the resistor smaller, less power is dissipated in the resistor and the trade off might be worth it for under powered (i.e. unamped) sources.

So by upping the power (adding an amp) on the 4s you are overcoming the disadvantage of power being dissipated in the resistor. When you amp the 4p you're still dealing with rolled off highs due to a sub-optimal acoustic design.

Just an educated guess.