Headset Impedance Parameters for a typical cellphone

Headset Impedance Parameters for a typical cellphone

Can anyone tell me the impedance specifications for a typical cellphone? =
 
I'm interested in obtaining a "high-quality" headset from Sennheiser =3F=
 
one that's not specifically intended for use with cellphones. But I 
wonder if it will work reasonably well with a cellphone anyway. Their 
fact sheet on it . . . . . . . . . . . . . . . . . .
http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
. . . . . . . . . . . . . . . . . . . . . . . . . . .
lists the following nominal impedance values:
headphone: 300 Ohms
microphone: 200 Ohms (dynamic transducer, supercardioid pickup pattern)

I've already spoken with Sennheiser from whom I've received conflicting 
information. So, I thought I'd run this by you in hopes that someone 
might take a look and offer an informed opinion.

Any help will be greatly appreciated.

-----------------------------------
BACKGROUND: I'm about to embark on a new career as a trucker and a 
crucial piece of equipment will be a good mobile phone headset. Because 
of engine and road noise I'd like to get one with an over-the-ear 
headphone and a high-quality uni-directional boom mic.
-----------------------------------

Thanks.
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone



Crazy Horse wrote:

> Can anyone tell me the impedance specifications for a typical cellphone?
> I'm interested in obtaining a "high-quality" headset from Sennheiser =3F
> one that's not specifically intended for use with cellphones. But I
> wonder if it will work reasonably well with a cellphone anyway. Their
> fact sheet on it . . . . . . . . . . . . . . . . . .
> http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
> . . . . . . . . . . . . . . . . . . . . . . . . . . .
> lists the following nominal impedance values:
> headphone: 300 Ohms
> microphone: 200 Ohms (dynamic transducer, supercardioid pickup pattern)
>
> I've already spoken with Sennheiser from whom I've received conflicting
> information. So, I thought I'd run this by you in hopes that someone
> might take a look and offer an informed opinion.
>
> Any help will be greatly appreciated.

As long as your high quality headphones do not have an impedance *lower* than
the phone expects (in which case you'd 'overload' the phone's electronics) ,
you'll be just fine.

This is not an example of an 'impedance matching' issue at all, so don't waste
time looking for exact values.

Graham

Re: Headset Impedance Parameters for a typical cellphone

Eeyore wrote:
>
> Crazy Horse wrote:
>
>> Can anyone tell me the impedance specifications for a typical cellphone?
>> I'm interested in obtaining a "high-quality" headset from Sennheiser ?
>> one that's not specifically intended for use with cellphones. But I
>> wonder if it will work reasonably well with a cellphone anyway. Their
>> fact sheet on it . . . . . . . . . . . . . . . . . .
>> http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
>> . . . . . . . . . . . . . . . . . . . . . . . . . . .
>> lists the following nominal impedance values:
>> headphone: 300 Ohms
>> microphone: 200 Ohms (dynamic transducer, supercardioid pickup pattern)
>>
>> I've already spoken with Sennheiser from whom I've received conflicting
>> information. So, I thought I'd run this by you in hopes that someone
>> might take a look and offer an informed opinion.
>>
>> Any help will be greatly appreciated.
>
> As long as your high quality headphones do not have an impedance *lower* than
> the phone expects (in which case you'd 'overload' the phone's electronics) ,
> you'll be just fine.
>
> This is not an example of an 'impedance matching' issue at all, so don't waste
> time looking for exact values.
>
> Graham
>
>
I think the issue is more the microphone than the earpieces. All
cellphones, TTBOMK, use condensors. The dynamic mic of the Sennies
might not like having a bias voltage applied. If it doesn't 'mind' so
much, the result might still not be satisfactory.

jak

Re: Headset Impedance Parameters for a typical cellphone

In article <Psp4i.51$%T3.33@bignews8.bellsouth,net >, 
jakdedert@bellsouth,net says...
> Eeyore wrote:
> > As long as your high quality headphones do not have an impedance *lower=
*
> > than the phone expects (in which case you'd 'overload' the phone's
> > electronics), you'll be just fine.
> > 
> > This is not an example of an 'impedance matching' issue at all, so don'=
t
> > waste time looking for exact values.
> > 
> > Graham
> > 
> I think the issue is more the microphone than the earpieces. All 
> cellphones, TTBOMK, use condensors. The dynamic mic of the Sennies 
> might not like having a bias voltage applied. If it doesn't 'mind' so 
> much, the result might still not be satisfactory.
> 
> jak
> 
Hmmmm... this resonates with what one of the Sennheiser guys said. I 
guess I was skeptical because I doubted that your typical cellphone 
headset uses a condensor mic. This doubt was based on my limited 
experience with condensor mics which have all included their own power 
source (i.e., a battery). Since I was pretty sure the cellphone headset 
mics I've seen have not inluded batteries, I wrongly surmised they 
weren't condensor mics.

The guy at Sennheiser said that another Sennheiser (CC-550) headset
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
http :// www .sennheisercommunications,com /comm/icm eng.nsf/root/05361#
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
has an "electret" mic. I think he said something about "polarized" 
leads that draw power from the device they're plugged into.

Anyway, I guess based on this information about the need for a condensor 
mic, I'll have to go with the CC-550, which is a shame in a way: 
compared to the HMD280, it looks like a toy!

In any event, thanks a lot for the info. It's a big help.
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone

"Crazy Horse" wrote ...
> Hmmmm... this resonates with what one of the Sennheiser guys said. I
> guess I was skeptical because I doubted that your typical cellphone
> headset uses a condensor mic. This doubt was based on my limited
> experience with condensor mics which have all included their own power
> source (i.e., a battery). Since I was pretty sure the cellphone headset
> mics I've seen have not inluded batteries, I wrongly surmised they
> weren't condensor mics.

It is likely that ALL current cellphones use electret microphones.
Both internally, and they likely expect electret mics with any external
headsets, also. They feed the power on the same wire that they
receive the audio from the mic, so external mics don't need any
separate kind of power. Electret mics are smaller and cheaper
than dynamic mics. These two parameters are VERY important
to people who make cell phones by the millions.

> The guy at Sennheiser said that another Sennheiser (CC-550) headset
> http :// www .sennheisercommunications,com /comm/icm_eng.nsf/root/05361
> has an "electret" mic. I think he said something about "polarized"
> leads that draw power from the device they're plugged into.

Yes, thats how electret mics work.

> Anyway, I guess based on this information about the need for
> a condensor mic, I'll have to go with the CC-550, which is a
> shame in a way: compared to the HMD280, it looks like a toy!

It IS a toy compared to the 280. But don't limit your research to
high-end hi-fi headphones (280) and low-end consumer
headsets (550). I did a search on eBay for
david clark electret
and turned up several promising hits for aircraft headsets
running <$100 that would beat the socks off the 550 for
price and performance.

Re: Headset Impedance Parameters for a typical cellphone

In article <5bfdvvF2rc7cfU1@mid.individual,net >, rcrowley@xp7rt,net  
says...
> It is likely that ALL current cellphones use electret microphones.
> Both internally, and they likely expect electret mics with any external
> headsets, also. They feed the power on the same wire that they
> receive the audio from the mic, so external mics don't need any
> separate kind of power.
> :
> [snip]
> :

In article <5bfdfhF2s61ivU1@mid.individual,net >, rcrowley@xp7rt,net  
says...
> Note that over-the-ear headphones are dangerous to drive with
> and actually illegal in some jurisdictions. NOT recommended.
> :
> [snip]
> :

Richard-

You've given me a wealth of information to work with, and I thank you 
very much.

I *had* looked at Sennheiser's aviation family, but they all seemed 
obscenely expensive ($500+!). But the other factor steering me away 
from them is the safety factor -- the Sennys had noise cancellation 
circuitry. My point being that I'm very sensitive to your cautionary 
words about the danger involved in blocking out ambient noise when 
driving.

While I mentioned the HMD280 (dual-headphone), I was really leaning 
toward the HMD281 (single-headphone), for just this reason. I don't 
know if one can get single-headphone aviation headsets, but I suspect 
not. This gets me back to the Senny CC-550 (the toy)*
http :// www .sennheisercommunications,com /comm/icm eng.nsf/root/05361
or its single-headphone version (the CC-515).
http :// www .sennheisercommunications,com /comm/icm eng.nsf/root/5002150

I more than suspect these headphones -- being what I'd term "on-the-
ear" vs. "over-the-ear" (e.g., HMD280, aviation headsets) -- would be 
*less* effective at ambient noise attenuation, and therefore safer when 
it comes to driving. So, what I'm trying to sort out now is whether the 
"dualies" might be ineffective *enough* such that they'd be sufficiently 
safe.

In any event, I remain very grateful for your introducing me to the 
wider world of aviation headsets. I'm quite surprised they're so 
inexpensive. If I ever get into a "team driving" situation -- very 
unlikely barring I meet the "lady trucker girl-of-my-dreams" ;-) -- I 
will definitely look into these for my non-drive time in the truck.

Once again, thanks a lot for all the info. I've saved both your posts 
to my "headsets" directory.

All the best . . .

* Also, there's something to be said for a low-profile cabling/jacks 
footprint when it comes to the confines of a truck cab -- not a deciding 
factor, but still worth consideration.
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone



Crazy Horse wrote:

> jakdedert@bellsouth,net says...
> >
> > I think the issue is more the microphone than the earpieces. All
> > cellphones, TTBOMK, use condensors. The dynamic mic of the Sennies
> > might not like having a bias voltage applied. If it doesn't 'mind' so
> > much, the result might still not be satisfactory.
>
>
> Hmmmm... this resonates with what one of the Sennheiser guys said. I
> guess I was skeptical because I doubted that your typical cellphone
> headset uses a condensor mic. This doubt was based on my limited
> experience with condensor mics which have all included their own power
> source (i.e., a battery).

There are 2 issues here about the power required for condenser mics. The actual
element that picks up the sound in the mic (often called a capsule) requires a
'polarisation voltage' just to operate in the first place. More recently a
different type of capsule based around electret materials which store electric
charge in a way like magnets store magnetism have arrived on the scene and don't
require this polarisation voltage. It's 'built in' if you like.

Additional to that *all* capacitor mics require an amplifier stage immediately
next to ther capsule. This requires power to operate too but usually at a much
lower voltage than needed for those types that require polarisation.

In the low-cost electret type this buffer amplifier is usually (invariably?)
incorporated into the capsule assembly so it's not obvious.


> Since I was pretty sure the cellphone headset
> mics I've seen have not inluded batteries, I wrongly surmised they
> weren't condensor mics.

In this case, the headset mic will doubtless be an electret and the power for
the little amplifer next to/part of the capsule actually goes down the same wire
as the audio signal. You'll see this as a DC voltage on the wire.


> The guy at Sennheiser said that another Sennheiser (CC-550) headset
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> http :// www .sennheisercommunications,com /comm/icm_eng.nsf/root/05361#
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> has an "electret" mic. I think he said something about "polarized"
> leads that draw power from the device they're plugged into.

This is almost certainly the right type for you.


Graham

Re: Headset Impedance Parameters for a typical cellphone

In article <4652D22A.C7013694@hotmail,com >, 
rabbitsfriendsandrelations@hotmail,com says...
> 
> There are 2 issues here about the power required for condenser mics. The
> actual element that picks up the sound in the mic (often called a
> capsule) requires a 'polarisation voltage' just to operate in the first
> place. More recently a different type of capsule based around electret
> materials which store electric charge in a way like magnets store
> magnetism have arrived on the scene and don't require this polarisation
> voltage. It's 'built in' if you like.
> 
> Additional to that *all* capacitor mics require an amplifier stage
> immediately next to ther capsule. This requires power to operate too but
> usually at a much lower voltage than needed for those types that require
> polarisation.
> 
> In the low-cost electret type this buffer amplifier is usually
> (invariably?) incorporated into the capsule assembly so it's not obvious.
> 
> Crazy Horse wrote:
> > Since I was pretty sure the cellphone headset
> > mics I've seen have not inluded batteries, I wrongly surmised they
> > weren't condensor mics.
> 
> In this case, the headset mic will doubtless be an electret and the power
> for the little amplifer next to/part of the capsule actually goes down
> the same wire as the audio signal. You'll see this as a DC voltage on the
> wire.
> 

As Mr. Spock would say, "fascinating!" Thank you.

> Crazy Horse wrote:
> > The guy at Sennheiser said that another Sennheiser (CC-550) headset
> > http :// www .sennheisercommunications,com /comm/icm eng.nsf/root/05361#
> > has an "electret" mic. I think he said something about "polarized"
> > leads that draw power from the device they're plugged into.
> 
> This is almost certainly the right type for you.

Thanks for the feedback on the CC-550. I'm now leaning toward this one 
even more strongly, and largely out of safety considerations (as 
outlined in my reply to Robert).

Thanks for all the info. Really, very helpful.
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone

In article <MPG.20bca9dff96655b99896f0@news.west.earthlink,net >, 
spitting@spammers.is.never.invalid says...
> Thanks for the feedback on the CC-550. I'm now leaning toward this one=
 
> even more strongly, and largely out of safety considerations (as 
> outlined in my reply to Robert).

I meant to say "Richard" and not "Robert."
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone

In article <46520EC7.390EC6E8@hotmail,com >, 
rabbitsfriendsandrelations@hotmail,com says...
> As long as your high quality headphones do not have an impedance *lower* =
than
> the phone expects (in which case you'd 'overload' the phone's electronics=
) ,
> you'll be just fine.
> 
> This is not an example of an 'impedance matching' issue at all, so don't =
waste
> time looking for exact values.
> 
This much is good to know, and I thank you for the reply.

Your comments may also be shedding light on another issue I encountered 
a couple months or so ago. I found a cheapo microphone and plugged it 
into the mic port on my laptop. This was a mic I'd found somewhere and 
I'm pretty sure it was intended to be used with a PC. Immediately 
following that, I started hearing all kinds of RF noise through my 
earphone port: when the harddrive spinned, and particularly when I moved 
my mouse. Interestingly, over time that noise has died down and is now 
virtually inaudible. Another side effect was losing a certain loud tone 
that used to be independent of the software volume settings and worked 
in conjunction with some "Accessibility"-related features. That tone 
has not re-emerged with the passage of time.

I wonder if your comments may be a solution to this heretofore mystery.  
Perhaps the cheapo mic had a lower impedance than what my laptop 
required (or maybe it's just a matter of having a cheapo DELL laptop to 
begin with!). Any thoughts?

In any event, thanks for your reply. Good info to have.
-- 

-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone

If the headphone impedance is 40 ohms or greater it should work.
The microphone is a condenser type, that requires a built in pre-amp.
The phone should supply about 5 to 8 Volts, about 2 ma maximum
for the microphone. When wiring in the microphone, make sure that the
polarity is correct, and you do not cause any type of short, or you may
need to have the cell phone serviced.

--

JANA
_____


"Crazy Horse" <spitting@spammers.is.never.invalid> wrote in message
news:MPG.20bbc7ae4519ce249896ee@news.west.earthlink,net ...
Can anyone tell me the impedance specifications for a typical cellphone?
I'm interested in obtaining a "high-quality" headset from Sennheiser =3F
one that's not specifically intended for use with cellphones. But I
wonder if it will work reasonably well with a cellphone anyway. Their
fact sheet on it . . . . . . . . . . . . . . . . . .
http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
. . . . . . . . . . . . . . . . . . . . . . . . . . .
lists the following nominal impedance values:
headphone: 300 Ohms
microphone: 200 Ohms (dynamic transducer, supercardioid pickup pattern)

I've already spoken with Sennheiser from whom I've received conflicting
information. So, I thought I'd run this by you in hopes that someone
might take a look and offer an informed opinion.

Any help will be greatly appreciated.

-----------------------------------
BACKGROUND: I'm about to embark on a new career as a trucker and a
crucial piece of equipment will be a good mobile phone headset. Because
of engine and road noise I'd like to get one with an over-the-ear
headphone and a high-quality uni-directional boom mic.
-----------------------------------

Thanks.
--
_______
-CH
¯¯¯¯¯¯¯

Re: Headset Impedance Parameters for a typical cellphone

"Crazy Horse" wrote ...
> Can anyone tell me the impedance specifications for a typical
> cellphone?

There probably isn't a "typical" cellphone design, nor a "typical"
earphone impedance.

> I'm interested in obtaining a "high-quality" headset from Sennheiser
> one that's not specifically intended for use with cellphones. But I
> wonder if it will work reasonably well with a cellphone anyway. Their
> fact sheet on it . . . . . . . . . . . . . . . . . .
> http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
> lists the following nominal impedance values:
> headphone: 300 Ohms

The headphone has a reasonable expectation of working. Since
cellphones run on such a low voltage (the internal battery), the
receivers likely have a relatively low impedance to achieve
adequate sensitivity. If there were to be any problem with a
high-fidelity stereo headphone, it would be that the impedance
was too HIGH so that the cell phone couldn't generate sufficient
audio level to overcome your ambient noise.

> microphone: 200 Ohms (dynamic transducer, supercardioid
> pickup pattern)

The microphone may be a different matter. Since likely ALL cell
phones use electret condenser mics, there may be a problem
with the DC power (required for electrets) being applied to the
dynamic mic coil. There may also be a problem with the audio
levels (sensitivity) of the dynamic mic vs. the electret that the cell
phone is expecting.

> I've already spoken with Sennheiser from whom I've received
> conflicting information.

They really aren't in any position to tell you whether it would work
or not. Since they know nothing about whatever cell phone you
have, they would just be guessing along with the rest of us.

> So, I thought I'd run this by you in hopes that someone
> might take a look and offer an informed opinion.

The earphone/receivers would almost certainly work fine.
IMHO, there is a significant chance that the microphone might
not work as well as an electret condenser. But it is unlikely to
cause any damage to the cell phone.

> Any help will be greatly appreciated.

> BACKGROUND: I'm about to embark on a new career as a
> trucker and a crucial piece of equipment will be a good mobile
> phone headset. Because of engine and road noise I'd like to
> get one with an over-the-ear headphone and a high-quality
> uni-directional boom mic.

Note that over-the-ear headphones are dangerous to drive with
and actually illegal in some jurisdictions. NOT recommended.

If you really insist on noise-blocking over-the-ear headphones,
I'd use a conventional cell-phone headset (made for your cell
phone model) and put the receiver into a noise-blocking head
set like a David Clark or equivalent. DC are the kind of ear
protection they wear on the decks of aircraft carriers, etc.

You might find a better fit with a headset made for aircraft use
like this one on eBay # 280116629433 Noise blocking AND
an electret microphone.

Re: Headset Impedance Parameters for a typical cellphone

The impedance for most of the cell phone earphones and microphones
characteristics are an industry standard. Some of the different manufactures
are using a different connector. Most of them are using a sub-sized
tip-ring-sleeve type plug and jack arrangement. For these, you can buy most
any telephone earphone device, and it should work.

I have wired up my share of cell phones to different devices and self built
devices with great success. If the impedance and sensitivity is respected,
it will work.

--

JANA
_____


"Richard Crowley" <rcrowley@xp7rt,net > wrote in message
news:5bfdfhF2s61ivU1@mid.individual,net ...
"Crazy Horse" wrote ...
> Can anyone tell me the impedance specifications for a typical
> cellphone?

There probably isn't a "typical" cellphone design, nor a "typical"
earphone impedance.

> I'm interested in obtaining a "high-quality" headset from Sennheiser
> one that's not specifically intended for use with cellphones. But I
> wonder if it will work reasonably well with a cellphone anyway. Their
> fact sheet on it . . . . . . . . . . . . . . . . . .
> http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
> lists the following nominal impedance values:
> headphone: 300 Ohms

The headphone has a reasonable expectation of working. Since
cellphones run on such a low voltage (the internal battery), the
receivers likely have a relatively low impedance to achieve
adequate sensitivity. If there were to be any problem with a
high-fidelity stereo headphone, it would be that the impedance
was too HIGH so that the cell phone couldn't generate sufficient
audio level to overcome your ambient noise.

> microphone: 200 Ohms (dynamic transducer, supercardioid
> pickup pattern)

The microphone may be a different matter. Since likely ALL cell
phones use electret condenser mics, there may be a problem
with the DC power (required for electrets) being applied to the
dynamic mic coil. There may also be a problem with the audio
levels (sensitivity) of the dynamic mic vs. the electret that the cell
phone is expecting.

> I've already spoken with Sennheiser from whom I've received
> conflicting information.

They really aren't in any position to tell you whether it would work
or not. Since they know nothing about whatever cell phone you
have, they would just be guessing along with the rest of us.

> So, I thought I'd run this by you in hopes that someone
> might take a look and offer an informed opinion.

The earphone/receivers would almost certainly work fine.
IMHO, there is a significant chance that the microphone might
not work as well as an electret condenser. But it is unlikely to
cause any damage to the cell phone.

> Any help will be greatly appreciated.

> BACKGROUND: I'm about to embark on a new career as a
> trucker and a crucial piece of equipment will be a good mobile
> phone headset. Because of engine and road noise I'd like to
> get one with an over-the-ear headphone and a high-quality
> uni-directional boom mic.

Note that over-the-ear headphones are dangerous to drive with
and actually illegal in some jurisdictions. NOT recommended.

If you really insist on noise-blocking over-the-ear headphones,
I'd use a conventional cell-phone headset (made for your cell
phone model) and put the receiver into a noise-blocking head
set like a David Clark or equivalent. DC are the kind of ear
protection they wear on the decks of aircraft carriers, etc.

You might find a better fit with a headset made for aircraft use
like this one on eBay # 280116629433 Noise blocking AND
an electret microphone.

Re: Headset Impedance Parameters for a typical cellphone

There is a phenomenom in cellphone uplink audio on GSM systems called
"bumblebee." The problem is that the phone's transmitter modulates the
mic capsule and/or the wire connecting it to the input preamp,
resulting in a nasty 216 Hz (13E6/48 bits/second * 1 frame/ 1250 bits
= 216.67 frames/second) tone with lots of harmonics.

From this point of view, it would probably be better to get a mic
capsule that has simultaneously high output power (so that the input
preamp AGC doesn't amplify the bumblebee) and low impedance (so less
RF is induced).

--Randy

"JANA" <jana@NOSPAMca.inter,net > writes:

> The impedance for most of the cell phone earphones and microphones
> characteristics are an industry standard. Some of the different manufactures
> are using a different connector. Most of them are using a sub-sized
> tip-ring-sleeve type plug and jack arrangement. For these, you can buy most
> any telephone earphone device, and it should work.
>
> I have wired up my share of cell phones to different devices and self built
> devices with great success. If the impedance and sensitivity is respected,
> it will work.
>
> --
>
> JANA
> _____
>
>
> "Richard Crowley" <rcrowley@xp7rt,net > wrote in message
> news:5bfdfhF2s61ivU1@mid.individual,net ...
> "Crazy Horse" wrote ...
>> Can anyone tell me the impedance specifications for a typical
>> cellphone?
>
> There probably isn't a "typical" cellphone design, nor a "typical"
> earphone impedance.
>
>> I'm interested in obtaining a "high-quality" headset from Sennheiser
>> one that's not specifically intended for use with cellphones. But I
>> wonder if it will work reasonably well with a cellphone anyway. Their
>> fact sheet on it . . . . . . . . . . . . . . . . . .
>> http :// www .sennheiserusa,com /newsite/pdfs/HMD280.pdf
>> lists the following nominal impedance values:
>> headphone: 300 Ohms
>
> The headphone has a reasonable expectation of working. Since
> cellphones run on such a low voltage (the internal battery), the
> receivers likely have a relatively low impedance to achieve
> adequate sensitivity. If there were to be any problem with a
> high-fidelity stereo headphone, it would be that the impedance
> was too HIGH so that the cell phone couldn't generate sufficient
> audio level to overcome your ambient noise.
>
>> microphone: 200 Ohms (dynamic transducer, supercardioid
>> pickup pattern)
>
> The microphone may be a different matter. Since likely ALL cell
> phones use electret condenser mics, there may be a problem
> with the DC power (required for electrets) being applied to the
> dynamic mic coil. There may also be a problem with the audio
> levels (sensitivity) of the dynamic mic vs. the electret that the cell
> phone is expecting.
>
>> I've already spoken with Sennheiser from whom I've received
>> conflicting information.
>
> They really aren't in any position to tell you whether it would work
> or not. Since they know nothing about whatever cell phone you
> have, they would just be guessing along with the rest of us.
>
>> So, I thought I'd run this by you in hopes that someone
>> might take a look and offer an informed opinion.
>
> The earphone/receivers would almost certainly work fine.
> IMHO, there is a significant chance that the microphone might
> not work as well as an electret condenser. But it is unlikely to
> cause any damage to the cell phone.
>
>> Any help will be greatly appreciated.
>
>> BACKGROUND: I'm about to embark on a new career as a
>> trucker and a crucial piece of equipment will be a good mobile
>> phone headset. Because of engine and road noise I'd like to
>> get one with an over-the-ear headphone and a high-quality
>> uni-directional boom mic.
>
> Note that over-the-ear headphones are dangerous to drive with
> and actually illegal in some jurisdictions. NOT recommended.
>
> If you really insist on noise-blocking over-the-ear headphones,
> I'd use a conventional cell-phone headset (made for your cell
> phone model) and put the receiver into a noise-blocking head
> set like a David Clark or equivalent. DC are the kind of ear
> protection they wear on the decks of aircraft carriers, etc.
>
> You might find a better fit with a headset made for aircraft use
> like this one on eBay # 280116629433 Noise blocking AND
> an electret microphone.
>
>
>

--
% Randy Yates % "So now it's getting late,
%% Fuquay-Varina, NC % and those who hesitate
%%% 919-577-9882 % got no one..."
%%%% <yates@ieee.org> % 'Waterfall', *Face The Music*, ELO
http :// home.earthlink,net /~yatescr