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  #1   Report Post  
elfa
 
Posts: n/a
Default Newbie question re impedance matching

I'm connecting a small 3" 8 ohm speaker to a low power, battery operated
amplifier that was originally connected to a 4 ohm speaker. I want to match the
impedances by making my own small audio transformer using just a torroid ring
and some very thin wire from an old AC transformer.

Question...

What are the mechanics involved. I know I'll need two windings, a primary and
then a secondary. Can I just wind some of the wire on one side of the torroid
as the primary and then wind 2 times as much (because of 2 times the ohm value)
around the other half of the torroid?

Is there a minimum number of winds or is it a case of the more winds the better?

I'm trying to keep this bedrock simple.

Any advice will be appreciated.

thanks

elfa

  #2   Report Post  
Ethan Winer
 
Posts: n/a
Default Newbie question re impedance matching

Elfa,

I want to match the impedances by making my own small audio transformer


I'll go out on a limb and say that a home-made transformer will probably
have more losses (and other problems) than any efficiency gain you could
possibly hope for. This is not to discourage you from experimenting! Go
ahead and make the transformer anyway. But don't be disappointed if it
doesn't work well.

You mentioned having a toroid ring. Audio transformers need to work over a
wide range of frequencies. Is your toroid meant for audio, 60 Hz power, or
radio frequencies?

--Ethan


  #3   Report Post  
Ethan Winer
 
Posts: n/a
Default Newbie question re impedance matching

Elfa,

I want to match the impedances by making my own small audio transformer


I'll go out on a limb and say that a home-made transformer will probably
have more losses (and other problems) than any efficiency gain you could
possibly hope for. This is not to discourage you from experimenting! Go
ahead and make the transformer anyway. But don't be disappointed if it
doesn't work well.

You mentioned having a toroid ring. Audio transformers need to work over a
wide range of frequencies. Is your toroid meant for audio, 60 Hz power, or
radio frequencies?

--Ethan


  #4   Report Post  
elfa
 
Posts: n/a
Default Newbie question re impedance matching

In article , Ethan Winer says...

Elfa,

I want to match the impedances by making my own small audio transformer


I'll go out on a limb and say that a home-made transformer will probably
have more losses (and other problems) than any efficiency gain you could
possibly hope for. This is not to discourage you from experimenting! Go
ahead and make the transformer anyway. But don't be disappointed if it
doesn't work well.

You mentioned having a toroid ring. Audio transformers need to work over a
wide range of frequencies. Is your toroid meant for audio, 60 Hz power, or
radio frequencies?

--Ethan


I have no idea what the toroid was originally designed for....I just bought a
handful of them at an electronics discount house. I used one for a balun (used
in shortwave antennas for impedence matching cable to plain old copper wire).
The toroid is about 1 1/4 inches in diameter.

The amp has an 'input' of 450 mV and a max output of 2W. The speaker is 8 ohm
and max of 6W. Without impedence matching, my little low power amp over drives
the speaker. I just want to reduce the distortion. I'm not an audiophile so I
really don't care about the 'perfect' sound system. I have a hearing disability
and the whole point of this project is to listen to my small radios (shortwave)
with their tiny speakers without the frustration of not understanding what I'm
hearing.

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.

thanks

elfa

  #5   Report Post  
elfa
 
Posts: n/a
Default Newbie question re impedance matching

In article , Ethan Winer says...

Elfa,

I want to match the impedances by making my own small audio transformer


I'll go out on a limb and say that a home-made transformer will probably
have more losses (and other problems) than any efficiency gain you could
possibly hope for. This is not to discourage you from experimenting! Go
ahead and make the transformer anyway. But don't be disappointed if it
doesn't work well.

You mentioned having a toroid ring. Audio transformers need to work over a
wide range of frequencies. Is your toroid meant for audio, 60 Hz power, or
radio frequencies?

--Ethan


I have no idea what the toroid was originally designed for....I just bought a
handful of them at an electronics discount house. I used one for a balun (used
in shortwave antennas for impedence matching cable to plain old copper wire).
The toroid is about 1 1/4 inches in diameter.

The amp has an 'input' of 450 mV and a max output of 2W. The speaker is 8 ohm
and max of 6W. Without impedence matching, my little low power amp over drives
the speaker. I just want to reduce the distortion. I'm not an audiophile so I
really don't care about the 'perfect' sound system. I have a hearing disability
and the whole point of this project is to listen to my small radios (shortwave)
with their tiny speakers without the frustration of not understanding what I'm
hearing.

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.

thanks

elfa



  #6   Report Post  
Kevin Murray
 
Posts: n/a
Default Newbie question re impedance matching

Not to discourage you from experimenting either, but my recommendation would
be to wire two 8 ohm speakers in parallel and connect them across the output
of your amp. This would allow you to reach your amp's full output and also
increase your volume ouput. Of course if you don't have a second speaker
then my advice is useless :s


"elfa" wrote in message
...
I'm connecting a small 3" 8 ohm speaker to a low power, battery operated
amplifier that was originally connected to a 4 ohm speaker. I want to

match the
impedances by making my own small audio transformer using just a torroid

ring
and some very thin wire from an old AC transformer.

Question...

What are the mechanics involved. I know I'll need two windings, a primary

and
then a secondary. Can I just wind some of the wire on one side of the

torroid
as the primary and then wind 2 times as much (because of 2 times the ohm

value)
around the other half of the torroid?

Is there a minimum number of winds or is it a case of the more winds the

better?

I'm trying to keep this bedrock simple.

Any advice will be appreciated.

thanks

elfa



  #7   Report Post  
Kevin Murray
 
Posts: n/a
Default Newbie question re impedance matching

Not to discourage you from experimenting either, but my recommendation would
be to wire two 8 ohm speakers in parallel and connect them across the output
of your amp. This would allow you to reach your amp's full output and also
increase your volume ouput. Of course if you don't have a second speaker
then my advice is useless :s


"elfa" wrote in message
...
I'm connecting a small 3" 8 ohm speaker to a low power, battery operated
amplifier that was originally connected to a 4 ohm speaker. I want to

match the
impedances by making my own small audio transformer using just a torroid

ring
and some very thin wire from an old AC transformer.

Question...

What are the mechanics involved. I know I'll need two windings, a primary

and
then a secondary. Can I just wind some of the wire on one side of the

torroid
as the primary and then wind 2 times as much (because of 2 times the ohm

value)
around the other half of the torroid?

Is there a minimum number of winds or is it a case of the more winds the

better?

I'm trying to keep this bedrock simple.

Any advice will be appreciated.

thanks

elfa



  #8   Report Post  
henryf
 
Posts: n/a
Default Newbie question re impedance matching

elfa wrote:

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.


If you feel lucky, you could start with 50 turns for the
primary and 70 turns for the secondary. However, I won't
guarantee your satisfaction with the result.

In my opinion, you should reconsider the suggestions that
don't involve an impedance-matching transformer.

Have you tried using headphones jacked into your radios, and
do they sound OK?

  #9   Report Post  
henryf
 
Posts: n/a
Default Newbie question re impedance matching

elfa wrote:

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.


If you feel lucky, you could start with 50 turns for the
primary and 70 turns for the secondary. However, I won't
guarantee your satisfaction with the result.

In my opinion, you should reconsider the suggestions that
don't involve an impedance-matching transformer.

Have you tried using headphones jacked into your radios, and
do they sound OK?

  #10   Report Post  
elfa
 
Posts: n/a
Default Newbie question re impedance matching

In article . net, henryf
says...

elfa wrote:

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.


If you feel lucky, you could start with 50 turns for the
primary and 70 turns for the secondary. However, I won't
guarantee your satisfaction with the result.

In my opinion, you should reconsider the suggestions that
don't involve an impedance-matching transformer.

Have you tried using headphones jacked into your radios, and
do they sound OK?


Thanks for the suggestion re number of turns. As for headphones, that's a
'given'. My challenge is speakers.

elfa




  #11   Report Post  
elfa
 
Posts: n/a
Default Newbie question re impedance matching

In article . net, henryf
says...

elfa wrote:

Now....can you tell me about the number of winds needed? To experiment, I need
to start somewhere.


If you feel lucky, you could start with 50 turns for the
primary and 70 turns for the secondary. However, I won't
guarantee your satisfaction with the result.

In my opinion, you should reconsider the suggestions that
don't involve an impedance-matching transformer.

Have you tried using headphones jacked into your radios, and
do they sound OK?


Thanks for the suggestion re number of turns. As for headphones, that's a
'given'. My challenge is speakers.

elfa


  #12   Report Post  
Engineer
 
Posts: n/a
Default Newbie question re impedance matching


"Kevin Murray" wrote in message
able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them across

the output
of your amp. This would allow you to reach your amp's full output

and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are lots
of cheap 8 ohm speakers around, even free ones - you might find a 4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)


  #13   Report Post  
Engineer
 
Posts: n/a
Default Newbie question re impedance matching


"Kevin Murray" wrote in message
able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them across

the output
of your amp. This would allow you to reach your amp's full output

and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are lots
of cheap 8 ohm speakers around, even free ones - you might find a 4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)


  #14   Report Post  
Kevin
 
Posts: n/a
Default Newbie question re impedance matching

Great minds think alike Roger. What industry do you work in?

PS: I'm in Ottawa and I like your politics.

"Engineer" wrote in message
...

"Kevin Murray" wrote in message
able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them across

the output
of your amp. This would allow you to reach your amp's full output

and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are lots
of cheap 8 ohm speakers around, even free ones - you might find a 4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)




  #15   Report Post  
Kevin
 
Posts: n/a
Default Newbie question re impedance matching

Great minds think alike Roger. What industry do you work in?

PS: I'm in Ottawa and I like your politics.

"Engineer" wrote in message
...

"Kevin Murray" wrote in message
able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them across

the output
of your amp. This would allow you to reach your amp's full output

and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are lots
of cheap 8 ohm speakers around, even free ones - you might find a 4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)






  #16   Report Post  
Barry Mann
 
Posts: n/a
Default Newbie question re impedance matching

In , on 11/19/03
at 02:42 PM, elfa said:

...


The amp has an 'input' of 450 mV and a max output of 2W. The speaker
is 8 ohm and max of 6W. Without impedence matching, my little low
power amp over drives the speaker. I just want to reduce the
distortion. I'm not an audiophile so I really don't care about the
'perfect' sound system. I have a hearing disability and the whole
point of this project is to listen to my small radios (shortwave) with
their tiny speakers without the frustration of not understanding what
I'm hearing.


[ ... ]


Consider rethinking the project. Most amplifiers won't care about your
mismatch. Many "8 Ohm" speakers are closer to 6 Ohms anyway.
Technically, if your amplifier is optimized for 4 Ohms, you are not
driving the speaker as hard as you could. However, why bother? If the
speaker is being overdriven now, you don't need to deliver any more
power to it.

Further thought:

Depending on its design, you may be overloading the input stage of your
amplifier.

You may also be overloading the small radios as you connect them to the
amplifier.

Because of your hearing disability, you need more acoustic power than
that little speaker can provide. Consider finding a larger speaker in a
proper enclosure. You may need more power.

Also, consider using a tone control or equalizer to taylor the
frequency response of your speaker system to compliment your hearing
deficiency.

---

"WHAT? DON'T SHOUT, I CAN HEAR YOU," has been part of my life for
decades. Since I'm a stranger, I'll take the liberty of sharing one of
my pet issues.

Living with a hard of hearing person can be very frustrating for the
rest of us. Often, the hard of hearing person will deny they have a
problem. We do catch on after a while and we want learn how to deal
with the situation, but the hard of hearing person can sometimes be
more helpful. I don't want to drag all my dirty laundry out on this
forum, but please be mindful that, what seems like a comfortable
listening level to you, could be painfully loud and distracting to
nearby normal listeners. (and I do mean physical pain)

Having you listen through headphones to your TVs and radios would be
much more comfortable for the rest of us, but I know there is a concern
that you won't be able to hear or understand what is going on in the
room.

A better project for you would be to build a TV/radio headphone
amplifier that mixes in sound from the room. You could fiddle with the
frquency response of the amplifier to heighten your comprehension. I
can imagine that features such as separate muting and volume controls
for each input would be useful. A plus would be a provision for hearing
the phone and doorbell.

Some types of hearing loss result in a limited dynamic range. You can't
hear quiet sounds, but even moderately loud sounds cause discomfort.
There is a very narrow loudness range where your hearing can operate.
If this is your situation, consider adding a compressor to your
headphone amplifier.

-----------------------------------------------------------
SPAM:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, SPAMers are ruining my mailbox]
-----------------------------------------------------------

  #17   Report Post  
Barry Mann
 
Posts: n/a
Default Newbie question re impedance matching

In , on 11/19/03
at 02:42 PM, elfa said:

...


The amp has an 'input' of 450 mV and a max output of 2W. The speaker
is 8 ohm and max of 6W. Without impedence matching, my little low
power amp over drives the speaker. I just want to reduce the
distortion. I'm not an audiophile so I really don't care about the
'perfect' sound system. I have a hearing disability and the whole
point of this project is to listen to my small radios (shortwave) with
their tiny speakers without the frustration of not understanding what
I'm hearing.


[ ... ]


Consider rethinking the project. Most amplifiers won't care about your
mismatch. Many "8 Ohm" speakers are closer to 6 Ohms anyway.
Technically, if your amplifier is optimized for 4 Ohms, you are not
driving the speaker as hard as you could. However, why bother? If the
speaker is being overdriven now, you don't need to deliver any more
power to it.

Further thought:

Depending on its design, you may be overloading the input stage of your
amplifier.

You may also be overloading the small radios as you connect them to the
amplifier.

Because of your hearing disability, you need more acoustic power than
that little speaker can provide. Consider finding a larger speaker in a
proper enclosure. You may need more power.

Also, consider using a tone control or equalizer to taylor the
frequency response of your speaker system to compliment your hearing
deficiency.

---

"WHAT? DON'T SHOUT, I CAN HEAR YOU," has been part of my life for
decades. Since I'm a stranger, I'll take the liberty of sharing one of
my pet issues.

Living with a hard of hearing person can be very frustrating for the
rest of us. Often, the hard of hearing person will deny they have a
problem. We do catch on after a while and we want learn how to deal
with the situation, but the hard of hearing person can sometimes be
more helpful. I don't want to drag all my dirty laundry out on this
forum, but please be mindful that, what seems like a comfortable
listening level to you, could be painfully loud and distracting to
nearby normal listeners. (and I do mean physical pain)

Having you listen through headphones to your TVs and radios would be
much more comfortable for the rest of us, but I know there is a concern
that you won't be able to hear or understand what is going on in the
room.

A better project for you would be to build a TV/radio headphone
amplifier that mixes in sound from the room. You could fiddle with the
frquency response of the amplifier to heighten your comprehension. I
can imagine that features such as separate muting and volume controls
for each input would be useful. A plus would be a provision for hearing
the phone and doorbell.

Some types of hearing loss result in a limited dynamic range. You can't
hear quiet sounds, but even moderately loud sounds cause discomfort.
There is a very narrow loudness range where your hearing can operate.
If this is your situation, consider adding a compressor to your
headphone amplifier.

-----------------------------------------------------------
SPAM:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, SPAMers are ruining my mailbox]
-----------------------------------------------------------

  #18   Report Post  
Engineer
 
Posts: n/a
Default Newbie question re impedance matching

"Kevin" wrote in message
. rogers.com...

Great minds think alike Roger.


Ah... thanks, Kevin.

What industry do you work in?


Engineering - we make process sensors for the steel rolling and mining
industries worldwide. Electronics, electro-optics and DSP are the
core technologies.

PS: I'm in Ottawa and I like your politics.


Thanks again. So, how do we get rid of the Li(e)berals?

Cheers,

Roger

"Engineer" wrote in message
...

"Kevin Murray" wrote in

message

able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them

across
the output
of your amp. This would allow you to reach your amp's full

output
and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are

lots
of cheap 8 ohm speakers around, even free ones - you might find a

4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)




  #19   Report Post  
Engineer
 
Posts: n/a
Default Newbie question re impedance matching

"Kevin" wrote in message
. rogers.com...

Great minds think alike Roger.


Ah... thanks, Kevin.

What industry do you work in?


Engineering - we make process sensors for the steel rolling and mining
industries worldwide. Electronics, electro-optics and DSP are the
core technologies.

PS: I'm in Ottawa and I like your politics.


Thanks again. So, how do we get rid of the Li(e)berals?

Cheers,

Roger

"Engineer" wrote in message
...

"Kevin Murray" wrote in

message

able.rogers.com...
Not to discourage you from experimenting either, but my

recommendation would
be to wire two 8 ohm speakers in parallel and connect them

across
the output
of your amp. This would allow you to reach your amp's full

output
and also
increase your volume ouput. Of course if you don't have a second

speaker
then my advice is useless.



IMHO, still good! This is clearly the best solution. There are

lots
of cheap 8 ohm speakers around, even free ones - you might find a

4 or
6 inch one - better than your 3 incher.

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario
Canada

"Friends don't let friends vote Liberal"


(snip)




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