frequency response of headphones

Professional audio recording and studio engineering, post #45,404
Author:
Date:
Subject:
 bobopi
 2008-07-04 04:19:08
 frequency response of headphones
Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?
Here are the selected models:


*Beyer*

dt 770 pro
closed
5-35000Hz
<http://www.beyerdynamic.de/en/broadcast-studio-video-production/
products/headphonesheadsets/headphones.html?
tx_sbproductdatabase_pi1[showUid]
[showUID]=44&tx_sbproductdatabase_pi1[showUid]
[backPID]=93&cHash=cd6f9075a1>

dt 880 pro
semi-open
5-35000
<http://www.beyerdynamic.de/en/broadcast-studio-video-production/
products/headphonesheadsets/headphones.html?
tx_sbproductdatabase_pi1[showUid]
[showUID]=1851&tx_sbproductdatabase_pi1[showUid]
[backPID]=93&cHash=cef9b324c4>

dt 990 pro
open
5-35000 Hz
http://www.beyerdynamic.de/en/broadcast-studio-video-production/products/headphonesheadsets/headphones.html?tx_sbproductdatabase_pi1[showUid][showUID]=45&tx_sbproductdatabase_pi1[showUid][backPID]=93&cHash=cb51219012


*Fostex*

T50RP
semi-open
15-35000Hz
<http://www.fostexinternational.com/docs/music_products/
rp_series_spec.shtml>


*AKG*

K 702
open
10-39800Hz
<http://www.akg.com/site/products/powerslave,id,1082,pid,1082,nodeid,
2,_language,EN.html>
available in august

*Sony*

MDR 7509HD
closed
5-80000Hz
<http://pro.sony.com/bbsc/ssr/product-MDR7509HD/>


*Sennheiser*

HD 595/600/650
open
10-39000 Hz
<http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/09969>


*Ultrasone*

Pro 750/2500
closed/open
8-35000Hz
<http://www.ultrasone.com/index_en.php?
level=1&CatID=13.37&inhalt_id=45&shop_level=2&shop_CatID=1&shop_inhalt_id=0&do=showDetails&artikel_typ=allgemein&artikel_id=17>

I like this last one because it is magnetic shielded, which is
especially interesting when we perform intracerebral recordings which
are perturbated by magnetic fields but their S-logic system is not
that nice for my use I guess.

Thanks
Boris
Author:
Date:
Subject:
 Ken
 2008-07-04 13:50:52
 Re: frequency response of headphones
On Fri, 4 Jul 2008 04:19:08 -0700 (PDT), bobopi <[email protected]> wrote:

> Hi,
>
> in the context of physiological recordings with small animals (guinea
> pig) in a small anechoic chamber, I would like to use headphones as
> speakers between, say, 100 Hz and 35 kHz. I'm interested in the
> flattest response possible. I've selected a bunch of headphones, but
> the shape of their frequency response is never given on their
> constructors websites. Has someone performed tests ? I wonder, do they
> have a flat response (more or less) or has their response been adapted
> to the human ear ? Do you have some advice on some of these models ?


http://www.headphone.com/technical/product-measurements/build-a-graph.php
Author:
Date:
Subject:
 Angelo Campanella
 2008-07-04 11:51:50
 Re: frequency response of headphones
bobopi wrote:

> Hi,
>
> in the context of physiological recordings with small animals (guinea
> pig) in a small anechoic chamber, I would like to use headphones as
> speakers between, say, 100 Hz and 35 kHz. I'm interested in the
> flattest response possible. I've selected a bunch of headphones, but
> the shape of their frequency response is never given on their
> constructors websites. Has someone performed tests ? I wonder, do they
> have a flat response (more or less) or has their response been adapted
> to the human ear ? Do you have some advice on some of these models ?
> Here are the selected models:

Have you investigated small piezoelctric wafers? These are a slab of
for instance barium titanate or any of the the piezoectric families. The
output level is likely small at low frequencies.

Another posssibility is a condenser microphone driven as a transducer.
This will indeed be flat up to the resonance frequecy of the cavity
behind the diaphragm, about 20 to 30 kHz. A 1/4" microphone will be flat
up to your 40 kHz or higher, but the sound output SPL will be less.

What SPL levels do you need to conduct your work?

"Earphones" imply that you can allow the transducer to be near the ear..

Angelo Campanella
Author:
Date:
Subject:
 answerman
 2008-07-06 21:14:04
 Re: frequency response of headphones
Angelo Campanella <[email protected]> wrote in
news:q9obk.93940$102.12127@bgtnsc05-news.ops.worldnet.att.net:

>
>
> bobopi wrote:
>
>> Hi,
>>
>> in the context of physiological recordings with small animals (guinea
>> pig) in a small anechoic chamber, I would like to use headphones as
>> speakers between, say, 100 Hz and 35 kHz. I'm interested in the
>> flattest response possible. I've selected a bunch of headphones, but
>> the shape of their frequency response is never given on their
>> constructors websites. Has someone performed tests ? I wonder, do
>> they have a flat response (more or less) or has their response been
>> adapted to the human ear ? Do you have some advice on some of these
>> models ? Here are the selected models:
>
> Have you investigated small piezoelctric wafers? These are a slab
> of
> for instance barium titanate or any of the the piezoectric families.
> The output level is likely small at low frequencies.
>
> Another posssibility is a condenser microphone driven as a
> transducer.
> This will indeed be flat up to the resonance frequecy of the cavity
> behind the diaphragm, about 20 to 30 kHz. A 1/4" microphone will be
> flat up to your 40 kHz or higher, but the sound output SPL will be
> less.
>
> What SPL levels do you need to conduct your work?
>
> "Earphones" imply that you can allow the transducer to be near
> the ear..
>
> Angelo Campanella


There is no significant difference between using a piezo element
(bimorph) and a back-driven condenser microphone in this application.
Depending on the required SPL,a piezo bimorph might be a bit more linear
than a back-driven condenser microphone. On the other hand, for a given
diameter,the resonant frequency and upper frequency limit of a back-
driven condenser microphone is going to be much higher than that of a
piezo bimorph of the same diameter. In fact, the likelihood of using even
a 1/4" diameter piezo element (which will have very limited volume
displacement) to construct a sound delivery system that can provide a
flat response at the eardrum to 40KHz is zip to none. Additionally,
because both transducers are volume displacement sources, a closed,
sealed sound delivery system is required in order to achieve a flat
response down to 100Hz.
Author:
Date:
Subject:
 Scott Dorsey
 2008-07-04 08:42:32
 Re: frequency response of headphones
bobopi <[email protected]> wrote:
>in the context of physiological recordings with small animals (guinea
>pig) in a small anechoic chamber, I would like to use headphones as
>speakers between, say, 100 Hz and 35 kHz. I'm interested in the
>flattest response possible. I've selected a bunch of headphones, but
>the shape of their frequency response is never given on their
>constructors websites. Has someone performed tests ? I wonder, do they
>have a flat response (more or less) or has their response been adapted
>to the human ear ? Do you have some advice on some of these models ?
>Here are the selected models:

The problem is that closed-back headphones use the ear canal as part of
a resonant system, and so the low end response varies depending on the
size and shape of your inner ear.

Note also that if you get above 20 KHz, the beaminess becomes a problem
even with headphones. Very small changes in position result in large
changes in response.

Consequently, your local audiologist can't test above 8 KHz. If you
want a full-range test, they put a pressure transducer in your ear
canal to act as a reference.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."