[winny1]

Hello everybody!
 
This is my first post on the forums so excuse my "noob-iness".
 
I have a question about headphone impedance curves that has been confusing me for a while (I've searched everywhere but answers vary a lot).
 
I own a pair of Sennheiser HD598 which are rated as 50 ohms, but the impedance varies with frequency, reaching a peak of almost 300 ohms at 100hz. My understanding is that higher impedance requires higher voltage; thus, as I am driving them out of my laptop output, I don't know whether they are receiving enough power at the frequency where the impedance peaks. My general impression of the headphones from my laptop output jack is that they sound great with my only caveat being that the bass lacks physical impact (doesn't lack "bass" per se, just the visceral punch -- almost like a balanced armature earphone, but not quite as thin). I'm not sure whether they are voiced this way, or whether they were designed to be used with an amp. What I've read ranges from "they don't need an amp at all" to "they absolutely need one" which is really weird. 

 

I could live with them the way they are and I enjoy them quite a bit, but I don't know whether I am getting the best out of them.

 

I understand that tube amps would probably help, but they are too expensive for my current budget and they are already smooth sounding as is. I am mostly referring to solid state amplification, and whether more power would benefit the sound, as the impedance peak at 300 ohms seems to require more power than my laptop can output. 

 

Also getting off topic a bit -- graphs from InnerFidelity and Golden Ears seem to suggest that the Sennheiser HD598 sounds very similar to the Sennheiser HD600. Not only in frequency response, but also in the 30hz and 300hz square waves. Distortion and CSD plots also look similar, as do the impulse response. I'm wondering for anyone who have compared the two, is the HD600 having "better sound" just placebo as a result of the higher price? I'm sure they sound better, but twice-the-price better I am not too sure, especially considering how close they measure.

 

tl;dr - do headphones with impedance peaks require amps to compensate for the higher impedance at certain frequencies, and how will they benefit?

 

[VNandor]

To answer your off topic question: While I haven't heard truly high-end headphones, IME, differences between a 50$ headphone vs. a 100$ headphone will be far greater than the differences between a 100$ headphone vs. a 200$ headphone.
What I'm saying is that just because you payed twice as much money for a headphone, the sound won't be twice as good, and I assume the higher the prices the more this effect applies but again, I haven't heard kilo buck headphones so this is just my assumption based on my experience.
So, I wouldn't expect the HD600 to sound twice as good compared to the HD598. Actually I heard both of these and I personally didn't find the HD600 to be twice as good as the HD598.
 
The amp question is a bit tricky because unless you know how your amp and headphone measure, you can't "calculate" if they are getting enough power. Maybe you could try and audition some entry level amps with your HD598 to see if they drive them better than your laptop?

 

[castleofargh]

to be specific there would be a need to test your laptop at 50ohm and then at almost 300ohm, and know a good deal more about the actual specs.
now in general, the amplifier doesn't make individual deliveries per frequencies, it's just dealing with a voltage that moves around in amplitude over time. and that movement is the analog signal over time.  the impedance over frequencies in a fine system will just be one more variable to alter the signature of the headphone. for example the sensitivity at different frequencies doesn't have to follow exactly the impedance curve, and power needs aren't known from headphone impedance alone. there is more at play and you shouldn't try to read too much into it when you lack all the other variables.
 
what we do know for a fact, is that if you use a high impedance amp(your laptop has an amplifier too). then the impedance curve of the 598 will create a boost in the 100hz area. but if you use an amplifier with close to 0ohm impedance at the output, then you won't get such a boost at 100hz.
that much is a sure thing. but how your laptop may or may not have enough power to drive the hd598 is another matter. there is a general rule of impedance ratio that for so many reasons is a good idea to follow when in doubt, and it suggests to have the amp output impedance at least 8 times smaller than the impedance of the headphone. IDK if you can find the output impedance of your laptop, but often enough it's pretty high. mine is around 20ohm if I remember right. following the at least 1/8 ratio would be a bust with a 50ohm headphone. meaning I wouldn't get a good electrical damping, I would get the 100hz boost in the signature, and I may have other small problems with higher distortions, higher crosstalk and stuff like that. not necessarily obvious or even reaching audible levels, to know that I would need to try and measure the combo. but I can already say that it's not an ideal situation.
 
anyway, if you get ample loudness for your use, then voltage is probably fine(voltage and loudness are directly related, half the voltage is 6db quieter). current at 50ohm could be another matter, but again, there is no point making claims when we don't have measurements for the laptop's output into those loads.
people will tell you that you always need more power, better amp, more expensive amp... but most of them rely on how they feel and not at all on electrical measurements. so they could be right sometimes, but they could also be full of crap and tell you that power was the answer when they just preferred the sound of the other devices because it rolls off the trebles more, or some silly stuff any EQ could do for free. it's in the game when we only trust how we feel but still decide to make objective claims.
tube amps aren't anything special when it comes to power, in fact they can have some pretty specific problems of their own in some designs. but they certainly can sound different, and many people enjoy the sound of some tube amps even when they don't measure very well. taste is taste and you should always get what you enjoy the most.
 
I tend to be simple when it comes to audio, if I don't have an obvious problem, I don't spend time and money trying to solve it.

if you enjoy your music as it is, keep enjoying it. if someone put so much doubt in your mind that insecurity is growing a little more ever day, then just go try to get an amplifier, and maybe an external DAC to go with it. money isn't much if it can bring you peace of mind. it can very much end up sounding different, and who knows? you might love it, or you might feel like you wasted money and the difference is insignificant to you. everybody is different with different expectations.
 
and nothing at twice the price is twice as good. the world doesn't work that way. even less so in a domain like audio where personal preferences usually don't follow objective improvement. for example, SS amps can measure a good deal better than tube amps, but many audiophiles prefer tubes. it's all a giant mess and the best answers you can get will come from your own preferences. never takes other people's claims of superiority for granted, half the times what they call superior really meant "I like the sound better". and claims about power needs also meant "I liked the sound better on the one that happened to give bigger power number and I decided to jump to conclusion for no valid reason". try to go to some audio meetings. to try stuff in stores.  try to find audiophiles in your area and offer them a non alcoholic beer if they're underage, while you discuss stuff and try each other's gears. trying plenty of devices is the only way for you to find if what you use needs changing and also to know for sure your very own preferences in sound. then you go look at measurements and try to find patterns in signatures and impulse response or whatever to help you find the next device you may want to try.
 
 
wow that's one long rant to say not much. sorry about that ^_^.

 

[PurpleAngel]

  Hello everybody!
This is my first post on the forums so excuse my "noob-iness".
tl;dr - do headphones with impedance peaks require amps to compensate for the higher impedance at certain frequencies, and how will they benefit?

 
The HD598 do not come with a lot of bass.
I like to think of the HD598 as "amplifier optonal", they are fairly easy to drive, so can be used without a dedicated headphone amplifier, but should get some improvment when decently amped.
Maybe get a USB-DAC/amp, like the FiiO Q1 ($70) or Schiit Fulla 2 ($100).

 

[MindsMirror]

  tl;dr - do headphones with impedance peaks require amps to compensate for the higher impedance at certain frequencies, and how will they benefit?

No. Headphones like the HD598 are designed to sound correct from a controlled voltage amplifier. That means that the amplifier should not output higher voltage because of the impedance peak, it should have a neutral voltage frequency response. In fact the higher impedance at the peak actually means that it will draw less power from the amp at that frequency. That is because at a given voltage, increasing impedance will decrease current and power.
 
The opposite situation would be a controlled current amplifier. In this situation the current output from the amp would have a neutral response. That would mean that the impedance peak would in fact require more power, since given a constant current, increasing impedance will increase voltage and power. There might be some unique, rare, or unusual headphones and amps that are controlled current, but I am not aware of any of them.

 

[derred]

MindsMirror is right. I would just add that normally an amplifier would just increase the voltage and current equally on all frequencies. There are some amps that use low/high pass filters and then amplify things separately. For 55 Ohm headphones amps shouldn't be required, but if you find yourself having issues with the volume output of your laptop, you could consider a cheap little DAC/Amp like the FIIO K1 to get you a little more juice.
 
Best of luck!