Which is louder? Se530 vs Westone 3

Being that they're both sensitive IEM's, they should both reach ear damaging levels out of any source. I'm pretty sure an iPod can drive both those IEM's to an acceptable volume level where your hearing won't be at risk. Please take care of your hearing my friend, it's your most important possession in this hobby.

x2. As far as loudness goes, even hard to drive IEMs like the ER4S can get loud enough to damage hearing with an iPod.

The Westone 3 is ridiculously loud. With rock, I never can listen to its sibling the UM3X more than about half volume on the Ipod Classic and even that is locked at about 80% of potential. Very easy to drive.
Not sure which is louder though.

I used to be able to get my SE530's to some serious volume levels, especially through my cowon d2 but even through my iPhone it was right up there before distortion

They are the same and they go VERY LOUD!

If you know how to interpret the specs it's not to hard to figure out for yourself. Here's how to get a good approximation.

You need to know two basic things about a pair of headphones to estimate how loud it will be, the sensitivity and the impedance. You can find usually these specs on the manufacturer's website for almost any higher end headphone. The sensitivity is usually specified in decibels per milliwatt which is how loud it will be if fed a one milliwatt signal. Impedance is the alternating current counterpart to direct current resistance. Impedance varies with the frequency of the signal and is usually specified in ohms at 1Khz, and higher impedance will mean lower volume. Since decibels are a logarithmic scale and the relationship between impedance is roughly linear, the sensitivity counts for a lot more than the impedance.

Now let's look at specs for these IEMs.

SE530 (from HeadRoom)
Sensitivity: 119 dB/mW
Impedance @ 1kHz: 37 ohm

Westone 3 (from westone.com)
Sensitivity: 107 dB SPL
Impedance: 30 ohms

and for some perspective...

Beyerdynamic DT 880 (from HeadRoom)
Sensitivity: 96 dB
Impedance @ 1kHz: 250

As typical for IEM's bothe the Shures and the Westones have high sensitivity and low impedance compared to full size cans. The SE530s have slightly higher impedance but much higher sensitivity. Therefore the SE530s should be louder from just about any source. It would be a very sad amp that was ok with 30 ohms but not 37. There are all kinds of arcane reasons why this isn't a perfect way to figure out volumes, but for very large differences in sensitivity like this case, it's pretty much foolproof.

The SE530s are somewhat well known for their high sensitivity, their ability to be driven to very high volumes by just about anything, and to sound good from just about anything. Right now I'm listening to Vivaldi in a noisy office with my SE530s from my D2+ (which has quite powerful amp for a portable device) and 7 out of 50 is quite enough volume for listening all day. Either pair should be perfectly acceptable from just about any portable source though.

Yes, I don't find the specs very helpful in determining listening volume. Far from fool proof.

The GR8's have 118dB SPL and the W3 is 107dB SPL and the W3's go MUCH MUCH louder.

To be honest, I'm not sure how IEM sensitivity ratings are measured. For speakers, I understand it's the SPL at 1m on the axis of speaker projection, with 1W of power input.

What's the standard measurement for IEMs? Is there even a standard? If there is a standard, then I don't understand why Spyro hears that difference with the GR8s and the W3s, unless of course different IEMs scale differently as power input increases.

Maybe the specs are wrong? I was able to listen with 100% volume on a good 30% of my tracks via Nano with GR8. Pretty loud but certainly not ear-splitting range. Same tracks with W3 I could not go over 80% volume without entering "earsplitting" territory.

I have W3s and I can't go above 80-85% on an iPhone 3GS without it hurting.

I would say the W3s would "sound" louder because of their emphasis on the treble/bass over the laid back treble, mid emphasis of the SE530s.

westone 3 is louder to my ears unamped from classic ipod but not by much maybe 5-10% louder.