How to do amp matching for headphones?

The lower the ohm rating and the higher the SPL rating for a headphone, the easier it is for an amp to drive it. But there are other factors and ultimately you are right when you say;

until now I counted on my hearing only in detecting if the sound is properly amped or not

I think the quest to determine what headphone amp will drive what headphones is a bit of a silly quest to go upon; much like searching for a headphone solely based on frequency response.

The specs given do not really tell you anything of real importance in terms of driving ability (power output, potential difference and to a lesser extent output impedance would be more helpful). The HD650 is not particularly difficult to drive well IMO, however it most certainly needs an amp of moderate quality.

IMO the best thing you can do is go out and listen to various amps and compare them; there is one thing that (for the most part) specs will not tell you; synergy. The difference between the right amp and a "good amp" cannot be underestimated at this level. You have to ask yourself; are you looking for a pairing that is theoretically adequate, or a pairing that sounds good to you?



Regarding the micro, I have no doubt it'll be able to drive it loud enough but I dunno if it will drive it well (particularly having not seen it and not having stats given of any real meaning in this respect).

No.

The ohm rating as you call it has nothing to do with how easy a headphone is to drive. The Ergo AMT needs minimum of 3 watts and is 4 ohms. The HD-414 is 2000ohms and can run from an ipod on milliwatts.

The SPL level is an indiction of power handling capacity, not ease with which the transducer is driven.

Lol, I really don't know what that synergy really is. It doesn't make any sense from the electronics side (of the amplifier).

Mr. Green, you speak about comparing two amps, but you don't explain plonter how to do it. You just can't plug your headphones and switch between them as volumes will be different for both headphones tried.

There is, however, another method which is measuring the FR via RMAA with the impedance load you are going to use the amplifier with. If that FR remains flat or if the changes are minimal (basically not audible), then you will know that the amplifier ain't adding anything nor taking anything.

They can help, but synergy is more important and that is determined by the ears.

How many watts is the amp you are referring to? A very low power amp will struggle to drive power hungry speakers. That applies to headphones as well as full sized speakers. But there are wide parameters which mean virtually any amp will drive any speaker to one extent or another. So synergy will come into play.

Damn, I thought I had cracked it! Back to this thread then.......

http://www.head-fi.org/forums/f133/w...dphone-463983/

LOL So let me point out that this is the science forum (even if science is not really treated here), and a rational explanation is usually required.

By saying "synergy is determined by the ears" you are giving up that it is a completely subjective thing, that does not work for everyone IN THE SAME WAY, hence it is product of imagination/similar.

If I understood plonter's question, he is not asking for subjective opinions, but numbers and data that could explain that mysterious synergy.

For example, I could say Stax SR-202 + SRM-323II have excellent synergy as in more than one occasion I have really enjoyed my tunes and have been taken away. However other Stax users might think that a BH -or other electrostatic amp- has synergy and the amp I have doesn't have it. How come? If I follow my ears it has good "synergy", but if I follow other member's ears then it doesn't have synergy.

So who is right? Measurements are right. Unfortunately measuring electrostatic amplifiers is more difficult to do, but with dynamic amplifiers it has been done and by no means you need to break the bank for an amplifier in order to power correctly your headphone's drivers.

EDIT: Plonter, I checked your rig and I see you have some cables. I believe you hear some difference when using different ones (well, to say it correctly I believe you don't hear any difference, you just hear the same thing on a different volume and on a different mood). What I am trying to say with this is that you might still think the synergy is real or something.

Finally, I forgot to say that the concept of Synergy can be different between members, so when saying synergy alone it can be a bit difficult to understand what it is really being described.

I don't think he is talking about synergy. He is looking for a way to determine which amp will power a headphone well; which i mentioned as "power output, potential difference and to a lesser extent output impedance": stats that we are not always given the liberty of (for example, if you take my now retired littledot for an example the output impedance is not given, and my now in use HR2 has very little specs available). Even then, I sincerely doubt that this is enough to determine how well a headphone will be driven (and it will give a better impression of how loud the headphone will go). You'd really need to wait for someone who really knows their stuff to chime in about it in more depth (probably someone who works in the industry).

Synergy is indeed a subjective thing; for example I use the etymotic ER4P/S at the moment, which can seem a little cold to some and I am using an RSA amp - which means it is slightly on the warm side and rolled off in the treble (although not drastically). The treble is a little far-back for my taste but would be right up someone elses alley. For me synergy is about compensating for the perceived flaws of a headphone.

Unfortunately the only amp upgrades I have had the pleasure of spending considerable time with have been in totally different leagues and an ABX between the two would be pointless because the upgrade was so blatantly superior.

So I can't give advice on volume matching.



@plonter, input impedance is more significant to your source than the headphones as it is the entry point to the amp circuitry (I.e. where you plug your amp in to your source, not your headphones). There isnt enough info given to tell you how well they are being driven in the specs provided. The most important specs that are usually provided are output impedance and power output, although something like potential difference would help even more, I suspect. But like I say, I have fairly limited knowledge on this.


the ohmage of a headphone circuit is pretty arbitrary. It is more useful in studio applications (which if I recall correctly they either want a very low or quite high ohm rating - i suspect 600 ohm ish), however to us it at best tells us what type of power the headphone needs (whether it needs large amounts of current [low ohm] or not [high ohm] for the desired power).

Well the output impedance isn't that important I guess (at a guess its probably close to zero ohms as most modern headphone amplifiers are). The science behind it is that there is a more effective transfer of power before jack and plug if the impedance of each is closer. There are a lot of people (myself included probably) that will talk down the importance of impedance matching.

The other aspects are output power (which multiplied with sensitivity will tell you if you can make your headphone go loud enough) and various other specs that I have never seen released and I personally do not have enough knowledge to discuss at length. If you're truly that concerned, I would consider talking to a manufacturer or someone with a large knowledge in the area so they can tell you about the importance of voltage, power etc in a headphone system, and maybe even taking some measurements yourself.

I didn't know for sure if it was synergy, but as other member replied speaking about that I thought he was speaking about it.

Regarding any amp (like the little dot), you can measure the FR w/o knowing the manufacturer's specs. After all how the FR remains after amplification is what is important.

That is where you are being subjective. You claim RSA amp is <on the warm side>. That means that the FR when measured is not flat (not talking strictly flat, just approx).

Regarding the two different amps you have tried being in two different leagues, what determines for you which one is in a better league than other, its price, name of the company who built it? As I mentioned before, if when measuring an amplifier (1, 2 or whatever number of them you want to measure), its FR remains flat or/and there is a very small difference between them (I have seen results like that, from different amplifiers, SS, hybrid,...) then that FR will most likely be ignored or not even grasped by you when listening to music.

To put it simple for you as well, Plonter, what you will want for an amplifier to stay calm knowing your headphones are being correctly amplified (simplifying things) is that the input impedance of the amplifier is as highest as possible (from the choices you are looking for), and that the output impedance is as close to 0 as possible. Some amps like M^3 and Beta22 have an output impedance of <0.05. If your headphones have an impedance of 300 Ohm, you are going to want to use an amplifier with an impedance <300 Ohm. Very cheap to find an amplifier like that nowadays.

Regarding THD+N% you are going to want an amplifier with it value <0.5% (average percentage where above is usually heard by humans). That tells you the background noise of the amplifier.

Regarding what I marked, again, you can measure it at your home.

If I am not wrong, the 600 Ohm rating was part of industry standards some years ago, now I think it doesn't need to be strictly followed.


Finally to the OP (and anyone interested), you might want to read the following:

Audio Specifications

Unity Gain and Impedance Matching: Strange Bedfellows Very important
This last link is very interesting as it also explains what you are really doing when you are using your headphones in a balanced configuration.

Hope this clears things up.

The sound. The amp was a gift and RSA is not particularly well regarded locally. The balance is a slight issue for me as I prefer things to be "cold" but other than that everything is much cleaner, well defined, separated, textured etc. Far less blurring, congestion etc.

For the record I do not need assistance but I appreciate the clarifications