mkeroppi
New Head-Fier
- Joined
- Nov 27, 2004
- Posts
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The ER4 mystery
Introduction:
First of all, there's no mystery about the sound of the Etymotic ER4 (I have the ER-4B); it's easily the most detailed phones I've heard, and in that sense the most precise. The in-ear operation and the built with great care make these earphones very interesting in a layman's (my) acoustic "research".
Secondly, I'd like to thank Don Wilson@Etymotic Research for making them and providing information about them on these forums. I'd also like to thank others for their contribution to any references I've used on these forums and elsewhere.
Basically, I will present some findings on some research of these phones, and also have a few questions about the ER4 (in ear sound characteristics), and basically about the balance of the different versions as related to the equalization (for monitor purposes) which have answers hinted by previous discussions. Hopefully someone who's more knowledgeable will be able to provide better insights to my new most favorite phones.
*Note: This post is not intended to be a discussion of the subjective sound quality/characteristic/response of the ER4 series. I will try to compare the different models in quantitative terms (measurable) with each other and with measured "standards". I've had the luxury to try also the 4P and 4S at a recent meet; I do have my opinions of each of them, and off the record, the 4P does not sound to be in the same class as the other two in terms of clarity and preciseness.
1. Impedence – EQ differences
It has been repeated numerous times that the 4S differs from the 4B by -5dB at 10kHz (http://www6.head-fi.org/forums/showp...43&postcount=8). This seems to be also supported by the "Loudspeaker Room-Equalized Response" graph at the Etymotic website that relative response of the MCK model has a -5dB roll-off at 10kHz; also, probably the flat "relative response" is that of the 4B (http://www.etymotic.com/ephp/er4-ts.asp).
It has been known that the 4B is the only phone in the series that contains a capacitor load (http://www6.head-fi.org/forums/showt...b&pagenumber=2). The general patent document of the ER4 (http://patft.uspto.gov/netacgi/nph-P...070&RS=5887070) shows the series capacitor in the general design (Figure 5), which would lower the load impedance at high frequency. The impedance comparison at headphone.com of the different headphones version (http://www.headphone.com/layout.php?...are+Headphones) confirms this.
It is interesting to note that the impedance plot of the 4P and the 4S is only a linear shift from one another; this shift is around 73ohms as many others had found out (http://headwize.com/ubb/showpage.php...25&srch=er-4b;), or try the Fixup cable (http://www.fixup.net/tips/ety/ety.htm) at 75ohms. In any case, the linear shift, assuming reasonably there is little phase dependence, which is can be partly confirmed by the fact that the 4P and the 4S has no capacitors, indicates mainly a resistive load at the only difference affecting the impedance difference over frequency, which is why the cables with added resistor work to convert a 4P to 4S. One explanation for the difference in sound of the 4P and the 4S is that any changes to the low overall impedance of the 4P would affect it more so than the higher overall of the 4S. A more detailed explanation is available at this thread (http://www6.head-fi.org/forums/showthread.php?t=115835). Etymotic officially reports 73ohms of impedance, but not resistance in the specifications.
Note: One good thing about the impedance is that it's easy to measure, without using expensive equipments, relative to the frequency response using a model head. At least all measurements are done electronically and are reproducible, instead of having problems such as variable head size for different people. A lot can be told about the ER-4S from the impedance because their transducers are the same. Logically, the response will be inversing related to the impedance. High impedance at a certain frequency will generally mean a drop in response at that frequency, which is common sense, and seems to be correct in the ER4S.
So my next question is, is it possible to EQ the 4B externally, for example, to use common FIR/IIR filters, to make it sound very similar to a 4S, and vice versa? As shown, the 4B has a very difference impedance curve than the other two. This can be attributed to the series capacitor, which is normally used as high pass elements, and seems to be the only purpose in this case. Usually, there's more to it than just frequency response, but all evidence points toward the -5dB roll-off in this case, at least theoretically. I guess they can only be tested by people who have both.
Introduction:
First of all, there's no mystery about the sound of the Etymotic ER4 (I have the ER-4B); it's easily the most detailed phones I've heard, and in that sense the most precise. The in-ear operation and the built with great care make these earphones very interesting in a layman's (my) acoustic "research".
Secondly, I'd like to thank Don Wilson@Etymotic Research for making them and providing information about them on these forums. I'd also like to thank others for their contribution to any references I've used on these forums and elsewhere.
Basically, I will present some findings on some research of these phones, and also have a few questions about the ER4 (in ear sound characteristics), and basically about the balance of the different versions as related to the equalization (for monitor purposes) which have answers hinted by previous discussions. Hopefully someone who's more knowledgeable will be able to provide better insights to my new most favorite phones.
*Note: This post is not intended to be a discussion of the subjective sound quality/characteristic/response of the ER4 series. I will try to compare the different models in quantitative terms (measurable) with each other and with measured "standards". I've had the luxury to try also the 4P and 4S at a recent meet; I do have my opinions of each of them, and off the record, the 4P does not sound to be in the same class as the other two in terms of clarity and preciseness.
1. Impedence – EQ differences
It has been repeated numerous times that the 4S differs from the 4B by -5dB at 10kHz (http://www6.head-fi.org/forums/showp...43&postcount=8). This seems to be also supported by the "Loudspeaker Room-Equalized Response" graph at the Etymotic website that relative response of the MCK model has a -5dB roll-off at 10kHz; also, probably the flat "relative response" is that of the 4B (http://www.etymotic.com/ephp/er4-ts.asp).
It has been known that the 4B is the only phone in the series that contains a capacitor load (http://www6.head-fi.org/forums/showt...b&pagenumber=2). The general patent document of the ER4 (http://patft.uspto.gov/netacgi/nph-P...070&RS=5887070) shows the series capacitor in the general design (Figure 5), which would lower the load impedance at high frequency. The impedance comparison at headphone.com of the different headphones version (http://www.headphone.com/layout.php?...are+Headphones) confirms this.
It is interesting to note that the impedance plot of the 4P and the 4S is only a linear shift from one another; this shift is around 73ohms as many others had found out (http://headwize.com/ubb/showpage.php...25&srch=er-4b;), or try the Fixup cable (http://www.fixup.net/tips/ety/ety.htm) at 75ohms. In any case, the linear shift, assuming reasonably there is little phase dependence, which is can be partly confirmed by the fact that the 4P and the 4S has no capacitors, indicates mainly a resistive load at the only difference affecting the impedance difference over frequency, which is why the cables with added resistor work to convert a 4P to 4S. One explanation for the difference in sound of the 4P and the 4S is that any changes to the low overall impedance of the 4P would affect it more so than the higher overall of the 4S. A more detailed explanation is available at this thread (http://www6.head-fi.org/forums/showthread.php?t=115835). Etymotic officially reports 73ohms of impedance, but not resistance in the specifications.
Note: One good thing about the impedance is that it's easy to measure, without using expensive equipments, relative to the frequency response using a model head. At least all measurements are done electronically and are reproducible, instead of having problems such as variable head size for different people. A lot can be told about the ER-4S from the impedance because their transducers are the same. Logically, the response will be inversing related to the impedance. High impedance at a certain frequency will generally mean a drop in response at that frequency, which is common sense, and seems to be correct in the ER4S.
So my next question is, is it possible to EQ the 4B externally, for example, to use common FIR/IIR filters, to make it sound very similar to a 4S, and vice versa? As shown, the 4B has a very difference impedance curve than the other two. This can be attributed to the series capacitor, which is normally used as high pass elements, and seems to be the only purpose in this case. Usually, there's more to it than just frequency response, but all evidence points toward the -5dB roll-off in this case, at least theoretically. I guess they can only be tested by people who have both.
