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Need a graph of Soundmagic PL50 and also a decent Mic

post #1 of 11
Thread Starter 

Could anyone with the soundmagic pl50 and the necessary equipment post a frequency graph of it.

Also, I have a laptop with rmaa installed on it. Can someone post a link to some good cheap microphones that I can use (that work) to make graphs of different headphones myself. I bought a mic but couldn't get it to work so I returned it.

 

 

Thanks!

post #2 of 11

If memory serves, they print the graph on the box they come it, at least mine did.....

post #3 of 11
Thread Starter 

I lost my box. Can you take a close up picture of it and pm me it or just post it here?

post #4 of 11

h1a8, you can use these graphs:

 

 

Original Graph:

 

pl50_frequencyresponse.gif

 

and from an online review:

 

 

88.jpg

post #5 of 11

The original graph looks spot on. Don't worry about the High end looking like it rolls, it's fine and really only lacks the slightest amount of air. The bass is tight and the bump near 3khz is real but not as much as depicted either. It was the biggest issue I had with them but realy picky nits as it was really only a DB or 2 in use. Just a good phone with more clarity and lack of hash than one can expect for the price.


Edited by goodvibes - 7/13/11 at 6:50am
post #6 of 11
Thread Starter 

Thanks so much!

post #7 of 11

The PL50's response will also depend on the output impedance of the headphone amplifier. That's because the PL50's impedance has much variation across the audible spectrum:

Soundmagic PL50 impedance.png

 

I didn't measure much difference between coupled (worn) or in open air. DC resistance is around 27 ohms. The specs say 55 ohms at 1kHz, which is somewhat in agreement with the measurement. If you play the PL50 with a source with a low source impedance, like a Sansa Clip+ or an iPhone 4, you'll probably get the response shown in the graphs in the previous posts.

 

With a very low impedance sources, I hear too much energy at 2.7k and I have to EQ it down by a few dB. I also shelve the treble up because I feel that the presentation could be a little livelier. The spike at 8.5k is from ear canal resonance, and can vary from person to person. Some people lessen its effect with different tips. I'm comparing what I hear from the PL50 to a few pairs of speakers that measure flat at the listening position before I apply a house curve.

Soundmagic PL50 + large foam tips EQ.png

 

 

The PL50 might have been tuned for use with a source with somewhat higher output impedance, for example older portable players. This is what an iPad sends to the PL50 when there is added series resistance:

Soundmagic PL50 with various source impedances.png

 

Except for the half-wave ear canal resonance, the response looks very much like my EQ correction curve.

 

The headphone amp on a typical notebook computer has high source impedance, so you probably won't hear the peak at 2.7k. If the output impedance is high enough, the PL50 will sound thin, lacking bass. If the notebook computer happens to be a newer MacBook Pro, which happens to have low (<1 ohm) output impedance, then adding resistance in series might make the PL50 sound better.

 

Some people like to use a 75 ohm resistor to change the sound of the ER4P to make it sound like an ER4S. (BTW, I'm not one of them.) Channel balance issues aside, you can do something similar with the PL50 with a passive in-line volume control like the ones made by Shure, Koss, or Radio Shack. Think of it as a variable P-to-S adapter for other kinds of single-driver balanced-armature IEMs. Just dial in the resistance until the PL50 sees the right amount.

 

Of course, you could just listen to the PL50 as it is, and just get used to the sound. I do that sometimes.

 

BTW, I also have impedance measurements for the A151. They're very similar. I also hear a response peak at 2.7k. Perhaps they really do share the same model driver. I can post the impedance measurement if anyone is interested.

 

 


Edited by yuriv - 7/15/11 at 3:26am
post #8 of 11

Thank you yuriv! it was really so helpful to me knowing about my PL50.

Lower impedance made my PL50 going to empty-can like sound 'cuz connected to my iPod touch and iPhone.

I'll use my PL50 on oldie devices or note-PC.

 

Regards, Raph.

post #9 of 11
Quote:
Originally Posted by yuriv View Post

The PL50's response will also depend on the output impedance of the headphone amplifier. That's because the PL50's impedance has much variation across the audible spectrum:

Soundmagic PL50 impedance.png

 

I didn't measure much difference between coupled (worn) or in open air. DC resistance is around 27 ohms. The specs say 55 ohms at 1kHz, which is somewhat in agreement with the measurement. If you play the PL50 with a source with a low source impedance, like a Sansa Clip+ or an iPhone 4, you'll probably get the response shown in the graphs in the previous posts.

 

With a very low impedance sources, I hear too much energy at 2.7k and I have to EQ it down by a few dB. I also shelve the treble up because I feel that the presentation could be a little livelier. The spike at 8.5k is from ear canal resonance, and can vary from person to person. Some people lessen its effect with different tips. I'm comparing what I hear from the PL50 to a few pairs of speakers that measure flat at the listening position before I apply a house curve.

Soundmagic PL50 + large foam tips EQ.png

 

 

The PL50 might have been tuned for use with a source with somewhat higher output impedance, for example older portable players. This is what an iPad sends to the PL50 when there is added series resistance:

Soundmagic PL50 with various source impedances.png

 

Except for the half-wave ear canal resonance, the response looks very much like my EQ correction curve.

 

The headphone amp on a typical notebook computer has high source impedance, so you probably won't hear the peak at 2.7k. If the output impedance is high enough, the PL50 will sound thin, lacking bass. If the notebook computer happens to be a newer MacBook Pro, which happens to have low (<1 ohm) output impedance, then adding resistance in series might make the PL50 sound better.

 

Some people like to use a 75 ohm resistor to change the sound of the ER4P to make it sound like an ER4S. (BTW, I'm not one of them.) Channel balance issues aside, you can do something similar with the PL50 with a passive in-line volume control like the ones made by Shure, Koss, or Radio Shack. Think of it as a variable P-to-S adapter for other kinds of single-driver balanced-armature IEMs. Just dial in the resistance until the PL50 sees the right amount.

 

Of course, you could just listen to the PL50 as it is, and just get used to the sound. I do that sometimes.

 

BTW, I also have impedance measurements for the A151. They're very similar. I also hear a response peak at 2.7k. Perhaps they really do share the same model driver. I can post the impedance measurement if anyone is interested.

 

 

 

 The 8 to 1 ratio often discussed is about not having these frequency abberations so anything with a 4 ohm or lower output impedance, which is most things, will show a neglagable amount of additional upper mid bump. It will show more bump with higher impedance sources, not lower. Look at the output impedance as a resistor and the IEM impedance as a percentage. A higher output impedance has a greater effect on the lower impedance portions than the higher ones so the upper mid bump becomes a bigger issue with high output impedance sources, not low ones since it's less affected than the frequencies to either side. In line resitors change the response by dropping the output of the lower impedances more than the higher ones.

 

Those graphs themselves show less than +/- 1db difference with and added 5.5 ohms and 4 times that with 64 ohms so I don't think you got your info correct. If the bump sounds bigger with low output impedance, it's either the character of the source or lowered damping factor of your high impedance source muddying up the bass enough to mask it.

 

It rolls a bit early but I think you're adding too much, could use a bit more fullness in the bottom and has the upper mid bump that helps it sound very clean but also a little glassy. It's a very unhashy IEMbigsmile_face.gif

 

 When I had mine and played around with EQ, by ear, I pulled down something around 2.5Khz by about 2 db and added 1 db or so above 16k. On one pair I had, I vented them for fun successfully but they are very touchy to vent size and easier to make worse than better.


Edited by goodvibes - 11/14/12 at 7:56am
post #10 of 11

My responses in blue.

 

Quote:

Originally Posted by goodvibes View Post
 

 

 The 8 to 1 ratio often discussed is about not having these frequency abberations so anything with a 4 ohm or lower output impedance, which is most things, will show a neglagable amount of additional upper mid bump. It will show more bump with higher impedance sources, not lower. Look at the output impedance as a resistor and the IEM impedance as a percentage. A higher output impedance has a greater effect on the lower impedance portions than the higher ones so the upper mid bump becomes a bigger issue with high output impedance sources, not low ones since it's less affected than the frequencies to either side. In line resitors change the response by dropping the output of the lower impedances more than the higher ones.

 

Yes, but in this case, you want the electrical response to not be flat to compensate for the acoustic response of the IEM. If you use a P-to-S adapter on the ER-4P, you'll see that the frequency response going into the IEM isn't flat anymore, even if it is flat coming out of the player. The 8-to-1 ratio suggested by NWAVguy is for when you want the electrical response going into the headphone to be flat. For example, on most full-size headphones, there's a bump in the impedance at around 100 Hz caused by resonance. Most of the time you don't to be underdamped there or it could make the bass sound slow and tubby.

 

 

Those graphs themselves show less than +/- 1db difference with and added 5.5 ohms and 4 times that with 64 ohms so I don't think you got your info correct. If the bump sounds bigger with low output impedance, it's either the character of the source or lowered damping factor of your high impedance source muddying up the bass enough to mask it.

 

No, it's actually consistent with what I hear on the PL50. I hear a peak at around 2.7 kHz. Look at the graph again. If you increase the source resistance, there will be a dip in the electrical response at roughly the same frequency. That's probably why you're hearing less of a bump with higher output impedance. It doesn't take much to overdo it, though. With too high a source impedance, you'll eventually get a peak at 2 kHz, and too much increase in the treble, compared to the bass.

 

As for the accuracy of the measured frequency response, you can derive them from the supplied impedance-vs-frequency graph, which is typical of a single-armature IEM (resonance around 2-3 kHz and rising reactance at high frequencies due to the inductance of the coil). The Sherwood SE-777 supposedly has the same drivers as the PL50: http://ko.goldenears.net/board/files/attach/images/783980/619/047/1d85b4dd366f095ea87b281840f7bbcc.PNG

 

Here's a sample calculation: The DC resistance is 27 ohms. The impedance at 2200 Hz is roughly 190+j0 ohms. Let V be the open-circuit voltage and let's take the source impedance to be 64 ohms. Then the voltage going into the load will be

 

V*(27 ohms)/(27 ohms + 64 ohms) = 0.30*V at DC

V*(190 ohms)/(190 ohms + 64 ohms) = 0.75*V at 2200 Hz.

 

So the voltage going into the PL50 at 2200 Hz should be 20*log (0.75/0.30) = 8 dB higher than at low frequencies. That's close to what the graph is showing. Repeat for other values of the source impedance.

 

 

It rolls a bit early but I think you're adding too much, could use a bit more fullness in the bottom and has the upper mid bump that helps it sound very clean but also a little glassy. It's a very unhashy IEMbigsmile_face.gif

 

 When I had mine and played around with EQ, by ear, I pulled down something around 2.5Khz by about 2 db and added 1 db or so above 16k. On one pair I had, I vented them for fun successfully but they are very touchy to vent size and easier to make worse than better.

 

You must be referring to the EQ I'm applying. The actual curve should have more filters. I was going for economy and was trying to use only three peaking and two shelving filters, so I could export the settings into a Rockboxed Sansa Clip/Clip+. I didn't show the shelving EQ I eventually used to bump up the bass. Compared to my reference (speakers--flat-measuring or with a gentle X-curve applied), I definitely needed to pull 2.7k down by more than 2 dB. It's more like 5 dB. The response is also very weak around 3.5-4 kHz, something I didn't correct in the econo-EQ settings pictured above. The top octave also comes in very soft. In fact the +3-4 dB shelving filter I used for the treble is a bit conservative. What are you using for a reference?


Edited by yuriv - 11/17/12 at 2:09am
post #11 of 11

 Higher impedances are affected less by increasing the output impedance. Pretty simple and what you're seeing is a low impedance point at 2.7k not reacting as much. The impedance peak is actually at 2.2 in all your graphs and responds exactly as it should, by not decreasind as much as lower impedance portions of the frequency band. If this is what you meant instead of the impedance peak reducing output at it's given frequency, than I misunderstood your initial post. I think the bass dropping off is too severe to play with loading. You lose as much bass quantity over it entire bandwith as you reduce the bump. Better to EQ if you feel it's needed and call it a day.

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