Where did we get to with headphones (loudness thereof)?

[Piers]

Hi List,

Just coming back after a bit of a hiatus (ML is just so complete now). I notice that Alex' latest build has "volume control", and from looking at the data sheet, the 4646 has monstrous amounts of gain available there.

But I also just noticed that there's up to +6dB on the stereo line out port, so I thought I might play with that - or does "volume" work and I'm wasting my time?

The +6db comes from the "LOVLn" bits in Signal Select 2 if anyone wants to try before me - hobby time pretty curtailed for the next few days.

PG

[Morgan Look]

I was going to put this in my other email, but since we have a thread for it now.

The AK4646 data sheet specifies a minimum load impedance of 10k (ohm) on the line output.

Low impedance headphones are somewhere around 150ohm, and high impedance ones are typically around 600ohm.

This means a typical set of headphones is going to be asking the IC to provide over 10x the rated power.

Most likely this will just result in distortion as the output impedance of the amp limits the power at the load, but it could potentially damage (overheat?) the audio IC.

For the price of a Fiio E3 or E5, I suggest people use a headphone amplifier.

Morgan

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[Piers]

Mmmmm, you may have a point there ...

[Antony Newman]

Headphone Impedance mismatch:

Maybe buying 600 ohm headphones would be a good investment?

http://www.dolphinmusic.co.uk/article/321-headphones-impedance.html

Has anyone got a pair?  Do they sound distorted / can they play louder before distortion sets in?

AJ

[Piers]

My dad has a high-impedance crystal earpeice from the serious olden days (telephony use I think, bakelite, has 'gator clips on it). Not a huge lot of use on a film shoot, but ...

(600 is still a fair way from 10,000, but as always actual results from the field are best)

PG

[Antony Newman]

I've starting investigating which headphones to get for monitoring.
Does anyone have any recommendations?  Closed back / open back?

If your current pair is too quiet - could you let me know (in this thead).
+) Make of headphone
+) dB/mw  Sensitivity.

==================================================

If you only have the the 'dB/V' sensitivity, could you find out the 'Resistance' of your headphones, and type in the following equation into Google, substituting your our headphones detail

[Sennheiser HD 650]
-> For a 102 dB/V headphone
-> With 300 Ohm resistance
==================
102+10*log(300*0.001)
==================
= 96.8 dB/mW

==================================================

I've started reading about the Direct Sound EX-29
= 114 dB / mW    (ie about 50 times louder than the HD650s)

And they also have an incredible amount of (passive) isolation (29dB = 790 times less)

Has anyone ever used used them?

Regards,
AJ

[Ba...@aol.com]

A lot of video shooters use the Sony MDR-7506 closed phones.   Can tell you  a lick about the specs (sure you can find that on line),  but I know they are good and loud.

 

Chris

 

--

[Morgan Look]

Make sure they provide the impedance (resistance) as well, the efficiency alone will not give you the full picture.

I started generating some calculated results based on an assumed output impedance of 200ohm (as recommended by the spec sheet).  It became apparent that headphones with less than 200ohm impedance will be dumping more power into the output resistance than the headphones (while putting this additional load onto the IC).

My preliminary investigation suggested that two sets of headphones, one 600ohm and another 100ohm of equal efficiency should sound equally "loud".  But the chip will be working several times harder to drive the lower impedance phones.

I'll try to illustrate this with some actual data since there seems to be continued interest in the subject.  But that will have to wait till some time other than Saturday night (New Zealand).

Regards, Morgan.

--

[Piers]

Doing a bit of reading up, a passive transformer can be used to impedance match. I like passive!

PG 

[Antony Newman]

Thanks for the input.

With my (very simple) understanding (/guesswork) so far:

+) The fidelity of the AUDIO_IC signal is linked to current used.   Too much current, and the signal becomes distorted.

+) Power:   P = I^2 x R.

    If we decide there is fidelity point - that would fix the Current(I) 
    If we then reduce Resistance by 4 times, the Power is reduced by 4 times.

    Effect on dB level =  10 x Log ( 1 / 4 ) = - 6 dB

    => So, if we find a headphone that 200 ohm,  it would require a 50 ohm headphone
         to be 6 dB more sensitive (dB/W) to sound as loud (at the same fidelity level).

+)  If the specs of the following site are correct:
     http://www.extremeheadphones.com/ex-29.html

     The headphone has a 32 Ohm resistance, and a Sensitivity of 114 dB/Watt.

     => Effect on dB level =  10 x Log ( 32 / 200 ) = - 8 dB    (for same fidelity as 200ohm headphone)

     So this should sound as loud as  200 ohm headphone with a sensitivity of 114 - 8 = 106 dB/Watt.

+)  If the specs of the following site are correct:
     http://pro.sony.com/bbsc/ssr/product-MDR7506/

     The headphone has a 63 Ohm resistance, and a Sensitivity of 106 dB/Watt.

     => Effect on dB level =  10 x Log ( 63 / 200 ) = - 5 dB    (for same fidelity as 200ohm headphone)

     So this should sound as loud as  200 ohm headphone with a sensitivity of 106 - 5 = 101 dB/Watt.

+)  In my earlier (converted) listing of for the Sennheiser (96.8dB/W), 300Ohm
    
     This should sound as loud as  200 ohm headphone with a sensitivity of 96.8 + 1.76 = 98.5 dB/Watt.
     

If I've got this right (I can't be wrong all the time :D ) - then the 'Extreme' headphones should be able to play a clean signal considerably louder then the other two headphones (even though it is only 32 ohms).

=====

There is a secondary element to this. The sound isolation.
If there is little background noise - you need considerably less headphone volume.

If the 'Extreme' headphone does cut down the ambient sound by 29dB (almost 800 times lower) - you should be able play the audio signal even lower (as the headphone sound wouldn't be competing with anything) - and end up with a slightly higher fidelity sound.

AJ

[chungdha]

Found in ear plugs quite good especially ones goes really almost
unside and closes off all the sounds with headphones doesn't make a
perfect seal and would still hear allot of stuff.

[lightimages]

My results from listening to the T2i.

I have Sony MDR-7506 phones
http://pro.sony.com/bbsc/ssr/product-MDR7506/
They work with the T2i without amplification.
Impedance 63 Ohms
Sensitivity 106 dB/W/m
They are closed cup and claim to reduce external noise, but not much.
Big peak in voice frequencies. Sometimes helps when recording voices.
These phones are pretty much the standard of the video industry.

I also have, and always use Sennheiser HD 25-1 phones
http://www.sennheiserusa.com/professional_DJ-headphones-HD-25-1_502188
These work with the T2i without amplification, much louder than the
7506's.
Impedance 70 Ohms
Sensitivity not listed in Sennheiser specs.
They are closed cup and reduce external noise a lot more than the
7506's. Listed as DJ Headphones - High Attenuation of Ambient Noise.
Rated to suppress noise in 120dB environments.

Pros: Using these phones you only hear what the mics hear. If you
don't hear a truck drive by, it wasn't recorded.

The 25's are on-ear phones with smaller cups that don't bang into the
gear as much while shooting. Less sweaty too.

Much smoother frequency response.

Cons: When the director wants you the change the shot, you usually
won't hear that either. I have to ask directors to tap me if I'm
running camera and sound.

Pricy, but mine still work after using them for over 10 years.

lightimages

On Mar 18, 8:30 pm, Antony Newman <antony.new...@gmail.com> wrote:
> I've starting investigating which headphones to get for monitoring.
> Does anyone have any recommendations?  Closed back / open back?
>
> If your current pair is too quiet - could you let me know (in this thead).
> +) Make of headphone
> +) dB/mw  Sensitivity.
>
> ==================================================
>
> If you only have the the 'dB/V' sensitivity, could you find out the
> 'Resistance' of your headphones, and type in the following equation into
> Google, substituting your our headphones detail
>
> [Sennheiser HD 650]
> -> For a 102 dB/V headphone
> -> With 300 Ohm resistance
> ==================
> 102+10*log(300*0.001)
> ==================

> = *96.8 dB/mW*
>
> ==================================================
>
> I've started reading about the *Direct Sound EX-29*

[Piers]

On Sunday, March 20, 2011 3:55:36 AM UTC+11, aj_newman wrote:

Thanks for the input.

With my (very simple) understanding (/guesswork) so far:

+) The fidelity of the AUDIO_IC signal is linked to current used.   Too much current, and the signal becomes distorted.

+) Power:   P = I^2 x R.

    If we decide there is fidelity point - that would fix the Current(I) 
    If we then reduce Resistance by 4 times, the Power is reduced by 4 times.

Yes, but if you change R (which is actually Z - the impedance) you will (inversely) change I, so the power will not change in a linear way with the headphone impedance. Power goes up as impedance drops (until you get into impedance mismatch, see below)

If I understand things right (and I have no great confidence here) the output impedance and the HP impedance effectively form a voltage divider: the lower impedance in the cans, the lesser proportion of the voltage gets dropped across the HP coils.

(modern buffered gear typically has low output impedance and high input impedance so that most of the volts go into the "destination". The 4646 is, hence, specced for a 10KΩ load, so its output impedance is probably in the 100's of Ω)

The higher Z on the headphones, the more volts (and amps and watts) they're able to suck out of the output.

I think a transformer will change the impedance linearly to its ratio: so a 10:1 transformer would make the 32Ω iPhone headphones look like 320Ω.

Naturally, the most informative web page I first found about this is now eluding me ...

PG

[Antony Newman]

Lightimages,

Very useful information.

After combing the internet - the Sennheiser HD-25's were the other contender I was going to consider.

What is interesting is that it also comes in a 600 Ohms form:
http://www.amazon.co.uk/Sennheiser-II-Closed-Back-Headphones-Professional/dp/B000V6R8SK

I found the cable impedance of the 70 ohm version was reportedly 20 ohms (total =90 Ohms at plug)
 http://www.canford.co.uk/Products/54-176_SENNHEISER-HD-25-13-II-HEADPHONES-600-ohms

And the same site reckoned the sensitivity was 105 dB / mW.


-
Chungdha, Piers,

Thankyou for your insight in this too.

-

I have decided to order a pair of Extreme-29's

Reasons:

+) I am also trying to learn a language on London underground - and the sound isolation of these headphones is supposed to be amazing  (maybe even a step up from the Sennheiser HD-25s ?)

+) Diversity is the spice of life - I'll report back and tell you what they sound like compared to my very old Sennheiser HD 545's (which are rather temperamental and the reason I'm looking for some more cans).

Thoughts:

+) I am expected the HF sound from 3KHz upwards to be somewhat reduced. 
If this causes issues, I may well buy one of the HD-25 range.


AJ

[Antony Newman]

Here is a summary of my experience:

=================================
========= VOLUME 0 ==============
=================================

Ipod heaphones
+) Tinny, no bass.
+) Loudest

Sennheiser HD 545.
+) Very Clean
+) open sound with good bass.
+) Most Real sounding
+) 2nd Loudest

DirectSound Ex-29
+) A little bit tinny, not much bass.
+) Voices clearly heard
+) Not 'open'
+) Not as loud the other two headphones at Vol0
+) Usable

=================================
========= VOLUME 4 ==============
=================================

Ipod heaphones
+) Tizzy, no bass.
+) Loudest
+) Fatiguing

Sennheiser HD 545.
+) Too Loud!
+) High Frequencies a little distorted.
+) Still quite good.

DirectSound Ex-29
+) Tinny
+) Distorted
+) Not real sounding

=================================
====== On London Underground  ======
=================================

Ipod heaphones
+) Could not hear above the sound of the Tube without fear of going deaf.

Sennheiser HD 545.
+) Could not hear above the sound of the Tube without fear of going deaf.
+) Got some strange looks.

DirectSound Ex-29
+) Usable
+) (Probably sounds better with real sounds around you)
+) Got some even stranger looks (they are not exactly the prettiest looking headphones!)



Conclusion:  The Sennheiser HD545s were loud enough on headphone volume (0).    I'm going to see if I can find a shop where I can listed to some Sennheisser HD650s and report back.
   
With twice the impedance - I am hoping for an even cleaner sound on Volume 0,  and the ability to increase  the volume a few notches before any distortion creeps in.

AJ

[Antony Newman]

OK folks.

One last update from me on this:

I would heartily recommend the following pair of headphones for the Canon camera:

===================
Sennheiser HD 23-13 II
===================

+) 600 ohms
+) 140 Grams
+) Closed back
+) Sensitivity 104 db/w

Subjectively
+) Almost no distortion at max Headphone volume
+) Loud enough
+) Light / Compact
+) Good Bass / Quite Open high frequencies
+) Comfortable & Cable only on one side (ie doesn't get the way)

Regards,
AJ

[Trammell Hudson]

Markertek is making adapter cables for plugging in headphones to the 5D
and 550D:

http://www.markertek.com/Cables/Audio-Cables/DSLR-Audio-Cables/Sescom/DSLR-5DMKII-HOCF.xhtml
http://www.markertek.com/Cables/Audio-Cables/DSLR-Audio-Cables/Sescom/DSLR-550D-HOCF.xhtml

--
Trammell

[Antony Newman]

I used one so that I could walk into HiFi shops and 'test out' various headphones (ie without them seeing me with a soldered monstrosity of a patch cable)

They are very neat & professional, and seem to be just the right length.

AJ

[chungdha]

Nice, also used someones Azden Headphone which was crazy loud and had
to set like the output to zero and in playback reviewing the videos
had to set the sound to lowest and it was even loud forgot to set
write down which headset it was and can't seem to find it. Need to ask
the guy the next time which headphone it is.

[Antony Newman]

Chungdha,

The Azden DSR-12    http://www.adelcom.net/AzdenHP.htm

Impedance: 200 Ohms
Sensitivity: 105 db/W
Design: Open back

AJ

[chungdha]

Not sure doesn't look like that picture.

But anyone notice the distortions when listening to external mic when
the sound is recorded loud in the yellow zone. Mainly when monitoring
the onboard microphone the sound is loud and pretty clean without
distortion, kinda always worry when recording that the sound on
external mic will be very distorted when recorded too loud but
reviewing back you dont hear distortion at all on the laptop but on
the camera would hear the distortion.

[Antony Newman]

Chungdha,

I think the problem is the driver circuitry (AV Out) that we are hijacking is expecting a device that expects a very small about of electrical current.

When we hook up standard headphones that present very little electrical resistance,  this outputs too much electrical current - and distorts.

--- ON THE CAMERA --- (expects high resistance)

When I use low resistance (also called impedance) headphones of 32 Ohms -> I hear a lot of distortion at low volumes

When I use high resistance headphones of 600 Ohms -> I get very little distortion when connected to the camera.


--- ON AN IPOD --- (expects low resistance)

When I use low resistance headphones of 32 Ohms -> I hear No distortion, and headphones play loud

When I use high resistance headphones of 600 Ohms -> The sound has low volume.


My Conclusion for Camera headphones was:  
1) (most important) Use As high resistance headphones as you can find (eg 600 Ohm).
2) (or secondary importance) Use as sensitive headphones as you can find (eg 105 dB/watt)

Note: 'Sensitivity' is sometimes deliberately misprinted by some manufactures as:
i) dB/V (which gives a much higher number).  
ii) some put down the Maximum loudness (which is useless.  Unless you are DJ who is interested in permanent hearing loss)

FYI:  I'll be testing a pair of 300 Ohm Headphones in 2 weeks  (Sennheiser HD595s).

AJ

[mirek krejci]

How many different mics have you tried or do you know that particular one
well? Theres different mics and how they function.

What mic did you use?

--

[Antony Newman]

Mirek:

I have:
+) Rode Videomic Pro  (Small light)
+) Rode NTG3
+) Shure 55SH series 2
+) Sanken COS 11-DBP
+) Countryman B6
+) Senheisser ME66
+) Velodyne Subwoofer testing microphone

I haven't had much time use them on ML yet.
Current Microphone that I am using for testing => Rode Videomic Pro.

AJ

[mirek krejci]

Cheers Anthony, thats quite a collection.

good luck with the tests.

of interest is the phones you found most responsive.

So much depends on where and how its recorded and where and how its
listened to.., never ending. :)