Do I need an amp? (Hphones)

[Pixel]

I have a pair of cheap Sennheiser HD 215s which I bought to replace my old Medusa 5.1s () I use them for listening to music and playing games on my PC in the evenings/nights.

At the moment I just have them plugged into my sound card, but should I be using an amp with these? At what point does it become necessary to use an amp with headphones?

Also, does an amp just give you higher volumes, or do they also provide better quality?

 

[markiemrboo]

They are 32 ohms and I have seen the sensitivity listed as 112dB and 108dB. It didn't state what power level this was at, but for headphones I believe it tends to be at 1mW (a milliwatt). It may even be a maximum SPL figure? Lets assume it's 108dB at 1mW.

1mW at 32 ohms is 0.178v - E = sqrt(P x R) - E = sqrt(0.001 x 32)
The required current will be 5.5mA - I = E / R - I = 0.178 / 32

Lets assume the average sound card can put out 2v RMS and 50mA per channel. The above is then well within limits.

For every doubling of power, add about an extra 3dB of output. 108dB is loud, but should you want louder... in order to achieve 111dB you will need 2mW. This works out as 0.252v and 7.8mA. Again, still well within limits.

Now lets say you want 118dB. This will generally be regarded as about twice as loud as 108dB, and requires not double, but roughly ten times the power - 10mW. This works out as 0.565v and 17.6mA. Yet again, still well within limits. Even for the more standard and simple opamp output stages which may only be capable of about 25mA per channel.

I think that's all correct, though obviously someone step in and correct me if not! If this is the case, I don't think you would really benefit much from a headphone amplifier. If the figure stated is at 1mW, well, 120dB is about the threshold of pain and *will* cause hearing damage with long term exposure.

If the figure stated is a maximum SPL, or say an SPL measured at something other than 1mW, then the story will change obviously. I can't find anything which clarifies though so...

 

[Pixel]

They are 32 ohms and I have seen the sensitivity listed as 112dB and 108dB. It didn't state what power level this was at, but for headphones I believe it tends to be at 1mW (a milliwatt). It may even be a maximum SPL figure? Lets assume it's 108dB at 1mW.

1mW at 32 ohms is 0.178v - E = sqrt(P x R) - E = sqrt(0.001 x 32)
The required current will be 5.5mA - I = E / R - I = 0.178 / 32

Lets assume the average sound card can put out 2v RMS and 50mA per channel. The above is then well within limits.

For every doubling of power, add about an extra 3dB of output. 108dB is loud, but should you want louder... in order to achieve 111dB you will need 2mW. This works out as 0.252v and 7.8mA. Again, still well within limits.

Now lets say you want 118dB. This will generally be regarded as about twice as loud as 108dB, and requires not double, but roughly ten times the power - 10mW. This works out as 0.565v and 17.6mA. Yet again, still well within limits. Even for the more standard and simple opamp output stages which may only be capable of about 25mA per channel.

I think that's all correct, though obviously someone step in and correct me if not! If this is the case, I don't think you would really benefit much from a headphone amplifier. If the figure stated is at 1mW, well, 120dB is about the threshold of pain and *will* cause hearing damage with long term exposure.

If the figure stated is a maximum SPL, or say an SPL measured at something other than 1mW, then the story will change obviously. I can't find anything which clarifies though so...

Thanks for the help.

 

[markiemrboo]

Thanks for the help.

Right, I just found that it's 108dB at 1Vrms. I don't know whether this is a maximum figure, but I will assume that it is.

So, in order to achieve 108dB, you will need 1Vrms / 2V peak. I believe an X-fi at full volume has a level of 2Vrms. It will vary between cards / sources, but lets assume 2Vrms is available. At 1Vrms, you'll need an RMS current of 31mA, and peaks of 2V and 62mA are possible. You're now in a bit of trouble with a most opamps! It'll be clipping unless the output stage can deliver 62mA. The opamp on an x-fi (NJM4556) should be capable of about 100mA at such low voltage swings if I am reading the graph right, so if you have an X-fi, or something with such an opamp on the output, you may actually still be quite alright and should easily be able to reach the 108dB maximum.

You should also note that 108dB is still loud.

108dB at 32mW,
105dB at 16mW,
102dB at 8mW,
99dB at 4mW,
96dB at 2mW,
93dB at 1mW.

If you're limited to 25mA per channel you should be able to get about 10mW RMS and 20mW peak out of it, so you'd be looking at something around 103dB. If you listen to music with a crest factor of 20dB, then you should be able to listen at 83dB average level with 103dB peaks without it clipping I think. Most modern music is heavily compressed and you might only have a crest factor of 3 - 6dB, in which case you could listen at about 97 - 100dB average level without it clipping.

If anyone spots anything wrong, please do correct!

I think you should be alright without an amp still to be honest.

 

[Leporello]

Right, I just found that it's 108dB at 1Vrms. I don't know whether this is a maximum figure, but I will assume that it is.

So, in order to achieve 108dB, you will need 1Vrms / 2V peak. I believe an X-fi at full volume has a level of 2Vrms. It will vary between cards / sources, but lets assume 2Vrms is available. At 1Vrms, you'll need an RMS current of 31mA, and peaks of 2V and 62mA are possible. You're now in a bit of trouble with a most opamps! It'll be clipping unless the output stage can deliver 62mA. The opamp on an x-fi (NJM4556) should be capable of about 100mA at such low voltage swings if I am reading the graph right, so if you have an X-fi, or something with such an opamp on the output, you may actually still be quite alright and should easily be able to reach the 108dB maximum.

You should also note that 108dB is still loud.

108dB at 32mW,
105dB at 16mW,
102dB at 8mW,
99dB at 4mW,
96dB at 2mW,
93dB at 1mW.

If you're limited to 25mA per channel you should be able to get about 10mW RMS and 20mW peak out of it, so you'd be looking at something around 103dB. If you listen to music with a crest factor of 20dB, then you should be able to listen at 83dB average level with 103dB peaks without it clipping I think. Most modern music is heavily compressed and you might only have a crest factor of 3 - 6dB, in which case you could listen at about 97 - 100dB average level without it clipping.

If anyone spots anything wrong, please do correct!

I think you should be alright without an amp still to be honest.

Thanks for your thoughtful contributions to this thread. It's nice to see an informed reply on these threads. I absolutely agree that the OP does not need a headphone amplifier. I see the HD215s are promoted as DJ headphones and as suitable for use with an Ipod!

A headphone amplifier wouldn't make economic sense, quite simply, it's a bad bang for buck deal.

Pixel, you ask whether you need an amplifier. No you don't NEED an amplifier any more than you NEED your headphones. Are you unhappy with the sound of your phones? What quality of sound do you want? How important is good quality sound to you? How much are you prepared to spend?

I paid four times as much for my headphones than I paid for my PC with a 24" screen but that reflects my priorities (and my madness!). Have you ever listened to music from a decent source using a headphone amplifier and a set of high end 'phones? If not, perhaps you could find a local Hifi shop where you could audition such a set up. This would provide you with a benchmark to compare with your present setup. If however, all this sounds like too much of a hassle, you don't even WANT a headphone amplifier

 

[markiemrboo]

Thanks for your thoughtful contributions to this thread. It's nice to see an informed reply on these threads. I absolutely agree that the OP does not need a headphone amplifier. I see the HD215s are promoted as DJ headphones and as suitable for use with an Ipod!

Thanks I try my best.

I suppose if using a computer as a source, then it might be nice to have a headphone amp just for the volume control, but other than that it's not really going to be a requirement.

Most importantly: enjoy the music!

 

[Pixel]

Pixel, you ask whether you need an amplifier. No you don't NEED an amplifier any more than you NEED your headphones. Are you unhappy with the sound of your phones? What quality of sound do you want? How important is good quality sound to you? How much are you prepared to spend?

I love music, but only it's only recently that I've considered getting higher quality equipment to enhance my enjoyment of music further. Though most of my music would be played through my PC, which acts as an all-in-one centre for TV, music, gaming, and movies. Headphones are important to me, because I like my music loud, but my current living conditions don't allow me to play music loud with speakers. Closed-back phones are a must for me, I find them more comfortable (strange-shaped ears ) and I like the privacy.

I'm not too unhappy with the HD 215s, they sound good (to me) but not great. I can hear everything through them well, and a lot of sounds that I couldn't hear before in songs are now loud and clear. But I do have to crank up the volume quite a way before I reach my desired loudness. Also the music doesn't seem as "bassy" or "soft" enough for me. My old Medusas were too bassy and soft, and my current ones aren't bassy and soft enough, if that makes any sense. No amount of tweaking the sound card's output has generated a sound I'm truly happy with, but it's better than it was before. The HD 215s also feel very hot when worn for too long.

I'm thinking of buying something a lot more expensive and higher quality, I'm well aware that you get what you pay for when it comes to headphones. Something like the AKG K601s are within my price range, and look as if they'll do nicely, but there's no way for me to really test them before buying. Online reviews can only tell you so much. I also have to bear in mind that they'd be used for more than just music, but gaming, TV and the occasional movie too.