Amplifier question - very basic - update

[rothman]

Thanks to everyone who helped me with my question below. Here's what we did
at rehearsal last night.

I put the amp in "bridged mono", fed it one signal into input A, twist
braded the speaker wires of two separate 12" 8 Ohm speakers together and put
them on the two positive terminals on the amp. (so I was driving two
speakers on the red terminals in bridged mono)

It was considerably louder...I would say it is now perfect. I didn't get any
abnormal heat, the speaker wires stayed cool and didn't light up like a
light bulb. Needless to say my house didn't burn down.

I'm so new at this...let me know if i'm not supposed to be driving two
speakers on the red terminals in bridged mono.

Thanks

Doug

[Scott Dorsey]

rothman > wrote:
>
>I put the amp in "bridged mono", fed it one signal into input A, twist
>braded the speaker wires of two separate 12" 8 Ohm speakers together and put
>them on the two positive terminals on the amp. (so I was driving two
>speakers on the red terminals in bridged mono)

Now you are producing a lot more power, BUT each side of the amp is now
seeing a two-ohm load. This is bad for the amp although some amps can deal
with it.

>I'm so new at this...let me know if i'm not supposed to be driving two
>speakers on the red terminals in bridged mono.

What is the minimum rated impedance in bridged mono for the amp? The
manual will say so if the nameplate does not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

rothman > wrote:
>
>I put the amp in "bridged mono", fed it one signal into input A, twist
>braded the speaker wires of two separate 12" 8 Ohm speakers together and put
>them on the two positive terminals on the amp. (so I was driving two
>speakers on the red terminals in bridged mono)

Now you are producing a lot more power, BUT each side of the amp is now
seeing a two-ohm load. This is bad for the amp although some amps can deal
with it.

>I'm so new at this...let me know if i'm not supposed to be driving two
>speakers on the red terminals in bridged mono.

What is the minimum rated impedance in bridged mono for the amp? The
manual will say so if the nameplate does not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[rothman]

Scott,

The Manual says "don't add less than a 4 Ohm load in bridged mono as this
can damage your amplifier"

How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
thought it would combine to make 4 Ohm load.

Thanks for your help

Doug




"Scott Dorsey" > wrote in message
...
> rothman > wrote:
> >
> >I put the amp in "bridged mono", fed it one signal into input A, twist
> >braded the speaker wires of two separate 12" 8 Ohm speakers together and
put
> >them on the two positive terminals on the amp. (so I was driving two
> >speakers on the red terminals in bridged mono)
>
> Now you are producing a lot more power, BUT each side of the amp is now
> seeing a two-ohm load. This is bad for the amp although some amps can
deal
> with it.
>
> >I'm so new at this...let me know if i'm not supposed to be driving two
> >speakers on the red terminals in bridged mono.
>
> What is the minimum rated impedance in bridged mono for the amp? The
> manual will say so if the nameplate does not.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

[rothman]

Scott,

The Manual says "don't add less than a 4 Ohm load in bridged mono as this
can damage your amplifier"

How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
thought it would combine to make 4 Ohm load.

Thanks for your help

Doug




"Scott Dorsey" > wrote in message
...
> rothman > wrote:
> >
> >I put the amp in "bridged mono", fed it one signal into input A, twist
> >braded the speaker wires of two separate 12" 8 Ohm speakers together and
put
> >them on the two positive terminals on the amp. (so I was driving two
> >speakers on the red terminals in bridged mono)
>
> Now you are producing a lot more power, BUT each side of the amp is now
> seeing a two-ohm load. This is bad for the amp although some amps can
deal
> with it.
>
> >I'm so new at this...let me know if i'm not supposed to be driving two
> >speakers on the red terminals in bridged mono.
>
> What is the minimum rated impedance in bridged mono for the amp? The
> manual will say so if the nameplate does not.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

rothman > wrote:
>
>The Manual says "don't add less than a 4 Ohm load in bridged mono as this
>can damage your amplifier"

Okay, that's fine, then.

>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
>thought it would combine to make 4 Ohm load.

Two speakers with 8 ohm impedance combine to make a four ohm load.
1/8 + 1/8 = 1/4.

But, in bridged mono, each side of the amplifier is seeing half of the
load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
it should be rated for 2 ohms a side in stereo. Again, you can think of
bridged mono as having the two sides of your amplifier in series with one
another. It doubles the voltage produced but it doesn't produce any more
current.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

rothman > wrote:
>
>The Manual says "don't add less than a 4 Ohm load in bridged mono as this
>can damage your amplifier"

Okay, that's fine, then.

>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
>thought it would combine to make 4 Ohm load.

Two speakers with 8 ohm impedance combine to make a four ohm load.
1/8 + 1/8 = 1/4.

But, in bridged mono, each side of the amplifier is seeing half of the
load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
it should be rated for 2 ohms a side in stereo. Again, you can think of
bridged mono as having the two sides of your amplifier in series with one
another. It doubles the voltage produced but it doesn't produce any more
current.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[rothman]

Scott,

Thanks again. Here's the specs

The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.

675 watts bridged mono @ 4 Ohms

So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
bad for the amp?

If you could answer that I think I will be straight.


Thanks

Doug



"Scott Dorsey" > wrote in message
...
> rothman > wrote:
> >
> >The Manual says "don't add less than a 4 Ohm load in bridged mono as this
> >can damage your amplifier"
>
> Okay, that's fine, then.
>
> >How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
> >thought it would combine to make 4 Ohm load.
>
> Two speakers with 8 ohm impedance combine to make a four ohm load.
> 1/8 + 1/8 = 1/4.
>
> But, in bridged mono, each side of the amplifier is seeing half of the
> load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
> it should be rated for 2 ohms a side in stereo. Again, you can think of
> bridged mono as having the two sides of your amplifier in series with one
> another. It doubles the voltage produced but it doesn't produce any more
> current.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

[rothman]

Scott,

Thanks again. Here's the specs

The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.

675 watts bridged mono @ 4 Ohms

So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
bad for the amp?

If you could answer that I think I will be straight.


Thanks

Doug



"Scott Dorsey" > wrote in message
...
> rothman > wrote:
> >
> >The Manual says "don't add less than a 4 Ohm load in bridged mono as this
> >can damage your amplifier"
>
> Okay, that's fine, then.
>
> >How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
> >thought it would combine to make 4 Ohm load.
>
> Two speakers with 8 ohm impedance combine to make a four ohm load.
> 1/8 + 1/8 = 1/4.
>
> But, in bridged mono, each side of the amplifier is seeing half of the
> load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
> it should be rated for 2 ohms a side in stereo. Again, you can think of
> bridged mono as having the two sides of your amplifier in series with one
> another. It doubles the voltage produced but it doesn't produce any more
> current.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

rothman > wrote:
>Thanks again. Here's the specs
>
>The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
>4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.

Right. A perfect amplifier will put out twice as much power as the output
impedance is halved. In the real world that doesn't happen, which is why
you see these numbers.

>675 watts bridged mono @ 4 Ohms

If this were a perfect amplifier, since the bridged mono configuration
consists of two halves each seeing 2 ohms, the total output power should
be twice the output power of the 2 ohm rating. But it's not a perfect
amplifier, so it's lower.

>So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
>4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
>that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
>bad for the amp?

A lower impedance means a greater load, that pulls more current from the
amplifier. This is why you get more power from the amp with a 4 ohm load
than an 8 ohm load: there is more current being pulled by the load and
therefore more power.

POWER = CURRENT X VOLTAGE

VOLTAGE = CURRENT X RESISTANCE
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

rothman > wrote:
>Thanks again. Here's the specs
>
>The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
>4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.

Right. A perfect amplifier will put out twice as much power as the output
impedance is halved. In the real world that doesn't happen, which is why
you see these numbers.

>675 watts bridged mono @ 4 Ohms

If this were a perfect amplifier, since the bridged mono configuration
consists of two halves each seeing 2 ohms, the total output power should
be twice the output power of the 2 ohm rating. But it's not a perfect
amplifier, so it's lower.

>So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
>4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
>that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
>bad for the amp?

A lower impedance means a greater load, that pulls more current from the
amplifier. This is why you get more power from the amp with a 4 ohm load
than an 8 ohm load: there is more current being pulled by the load and
therefore more power.

POWER = CURRENT X VOLTAGE

VOLTAGE = CURRENT X RESISTANCE
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[P Stamler]

Wiring the two speakers as you have, in parallel, generates a 4-ohm load. That
means each side of the amp is driving 2 ohms. For most amps that would be a
disaster; and they would go into protection, or combust. However, the specs on
your amplifier say that it's okay; it's rated for a 2-ohm load in normal mode,
or a 4-ohm load in bridged-mono mode. And an 8-ohm load would be fine too.

So you're okay. However, do NOT try to add any more speakers in parallel to
what you already have!

Peace,
Paul

[P Stamler]

Wiring the two speakers as you have, in parallel, generates a 4-ohm load. That
means each side of the amp is driving 2 ohms. For most amps that would be a
disaster; and they would go into protection, or combust. However, the specs on
your amplifier say that it's okay; it's rated for a 2-ohm load in normal mode,
or a 4-ohm load in bridged-mono mode. And an 8-ohm load would be fine too.

So you're okay. However, do NOT try to add any more speakers in parallel to
what you already have!

Peace,
Paul

[S O'Neill]

You actually have a 4-ohm load, and your amp is in bridged-mono mode seeing that
load, emphasizing MONO. Calling it two ohms per channel is *one way* of looking
at it, but only as an academic exercise, since what bridging actually does is
make one channel out of two.

rothman wrote:
> Scott,
>
> Thanks again. Here's the specs
>
> The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
> 4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.
>
> 675 watts bridged mono @ 4 Ohms
>
> So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
> 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
> that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
> bad for the amp?
>
> If you could answer that I think I will be straight.
>
>
> Thanks
>
> Doug
>
>
>
> "Scott Dorsey" > wrote in message
> ...
>
>>rothman > wrote:
>>
>>>The Manual says "don't add less than a 4 Ohm load in bridged mono as this
>>>can damage your amplifier"
>>
>>Okay, that's fine, then.
>>
>>
>>>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
>>>thought it would combine to make 4 Ohm load.
>>
>>Two speakers with 8 ohm impedance combine to make a four ohm load.
>>1/8 + 1/8 = 1/4.
>>
>>But, in bridged mono, each side of the amplifier is seeing half of the
>>load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
>>it should be rated for 2 ohms a side in stereo. Again, you can think of
>>bridged mono as having the two sides of your amplifier in series with one
>>another. It doubles the voltage produced but it doesn't produce any more
>>current.
>>--scott
>>
>>--
>>"C'est un Nagra. C'est suisse, et tres, tres precis."
>
>
>

[S O'Neill]

You actually have a 4-ohm load, and your amp is in bridged-mono mode seeing that
load, emphasizing MONO. Calling it two ohms per channel is *one way* of looking
at it, but only as an academic exercise, since what bridging actually does is
make one channel out of two.

rothman wrote:
> Scott,
>
> Thanks again. Here's the specs
>
> The amp puts out 400 watts per channel @ 2 Ohms stereo, 300 watts/channel @
> 4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.
>
> 675 watts bridged mono @ 4 Ohms
>
> So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
> 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
> that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
> bad for the amp?
>
> If you could answer that I think I will be straight.
>
>
> Thanks
>
> Doug
>
>
>
> "Scott Dorsey" > wrote in message
> ...
>
>>rothman > wrote:
>>
>>>The Manual says "don't add less than a 4 Ohm load in bridged mono as this
>>>can damage your amplifier"
>>
>>Okay, that's fine, then.
>>
>>
>>>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms? I
>>>thought it would combine to make 4 Ohm load.
>>
>>Two speakers with 8 ohm impedance combine to make a four ohm load.
>>1/8 + 1/8 = 1/4.
>>
>>But, in bridged mono, each side of the amplifier is seeing half of the
>>load impedance. So if the amplifier is rated for 4 ohms in bridged mono,
>>it should be rated for 2 ohms a side in stereo. Again, you can think of
>>bridged mono as having the two sides of your amplifier in series with one
>>another. It doubles the voltage produced but it doesn't produce any more
>>current.
>>--scott
>>
>>--
>>"C'est un Nagra. C'est suisse, et tres, tres precis."
>
>
>

[rothman]

So I'm Cool then? Thanks for everyone's help!

Doug





"S O'Neill" > wrote in message
...
> You actually have a 4-ohm load, and your amp is in bridged-mono mode
seeing that
> load, emphasizing MONO. Calling it two ohms per channel is *one way* of
looking
> at it, but only as an academic exercise, since what bridging actually does
is
> make one channel out of two.
>
> rothman wrote:
> > Scott,
> >
> > Thanks again. Here's the specs
> >
> > The amp puts out 400 watts per channel @ 2 Ohms stereo, 300
watts/channel @
> > 4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.
> >
> > 675 watts bridged mono @ 4 Ohms
> >
> > So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less
than a
> > 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you
clarified
> > that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be
very
> > bad for the amp?
> >
> > If you could answer that I think I will be straight.
> >
> >
> > Thanks
> >
> > Doug
> >
> >
> >
> > "Scott Dorsey" > wrote in message
> > ...
> >
> >>rothman > wrote:
> >>
> >>>The Manual says "don't add less than a 4 Ohm load in bridged mono as
this
> >>>can damage your amplifier"
> >>
> >>Okay, that's fine, then.
> >>
> >>
> >>>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms?
I
> >>>thought it would combine to make 4 Ohm load.
> >>
> >>Two speakers with 8 ohm impedance combine to make a four ohm load.
> >>1/8 + 1/8 = 1/4.
> >>
> >>But, in bridged mono, each side of the amplifier is seeing half of the
> >>load impedance. So if the amplifier is rated for 4 ohms in bridged
mono,
> >>it should be rated for 2 ohms a side in stereo. Again, you can think of
> >>bridged mono as having the two sides of your amplifier in series with
one
> >>another. It doubles the voltage produced but it doesn't produce any
more
> >>current.
> >>--scott
> >>
> >>--
> >>"C'est un Nagra. C'est suisse, et tres, tres precis."
> >
> >
> >
>

[rothman]

So I'm Cool then? Thanks for everyone's help!

Doug





"S O'Neill" > wrote in message
...
> You actually have a 4-ohm load, and your amp is in bridged-mono mode
seeing that
> load, emphasizing MONO. Calling it two ohms per channel is *one way* of
looking
> at it, but only as an academic exercise, since what bridging actually does
is
> make one channel out of two.
>
> rothman wrote:
> > Scott,
> >
> > Thanks again. Here's the specs
> >
> > The amp puts out 400 watts per channel @ 2 Ohms stereo, 300
watts/channel @
> > 4 Ohms stereo and 200 watts per channel @ 8 Ohm Stereo.
> >
> > 675 watts bridged mono @ 4 Ohms
> >
> > So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less
than a
> > 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you
clarified
> > that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be
very
> > bad for the amp?
> >
> > If you could answer that I think I will be straight.
> >
> >
> > Thanks
> >
> > Doug
> >
> >
> >
> > "Scott Dorsey" > wrote in message
> > ...
> >
> >>rothman > wrote:
> >>
> >>>The Manual says "don't add less than a 4 Ohm load in bridged mono as
this
> >>>can damage your amplifier"
> >>
> >>Okay, that's fine, then.
> >>
> >>
> >>>How do two speakers with 8Ohm impedance each combine to produce 2 Ohms?
I
> >>>thought it would combine to make 4 Ohm load.
> >>
> >>Two speakers with 8 ohm impedance combine to make a four ohm load.
> >>1/8 + 1/8 = 1/4.
> >>
> >>But, in bridged mono, each side of the amplifier is seeing half of the
> >>load impedance. So if the amplifier is rated for 4 ohms in bridged
mono,
> >>it should be rated for 2 ohms a side in stereo. Again, you can think of
> >>bridged mono as having the two sides of your amplifier in series with
one
> >>another. It doubles the voltage produced but it doesn't produce any
more
> >>current.
> >>--scott
> >>
> >>--
> >>"C'est un Nagra. C'est suisse, et tres, tres precis."
> >
> >
> >
>

[Justin Ulysses Morse]

rothman > wrote:

> So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
> 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
> that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
> bad for the amp?

8 ohms is "less of a load" than 2 ohms, meaning that at 8 ohms the amp
has to do less work than at 2 ohms. But when they say "not less than a
4 ohm load" that means that 4 ohms or 8 ohms or 1000 ohms is fine, but
2 ohms or 3.8 ohms is bad. You can run an 8-ohm load in bridged mono
without any problems with your amp. You're fine at 4 ohms also. If
you added more speakers in parallel, you'd get less than 4 ohms and
that would be bad.

This confusion makes more sense when you understan Ohm's Law. Look it
up.

> If you could answer that I think I will be straight.

Do you like girls now?


ulysses

[Justin Ulysses Morse]

rothman > wrote:

> So which is less a load 2 Ohms or 8 Ohms? So if the amp says not less than a
> 4 Ohm load in Bridged mono....That means a 2 Ohm load (which you clarified
> that i'm now running) is OK, and a 8 Ohm load in Bridged mono would be very
> bad for the amp?

8 ohms is "less of a load" than 2 ohms, meaning that at 8 ohms the amp
has to do less work than at 2 ohms. But when they say "not less than a
4 ohm load" that means that 4 ohms or 8 ohms or 1000 ohms is fine, but
2 ohms or 3.8 ohms is bad. You can run an 8-ohm load in bridged mono
without any problems with your amp. You're fine at 4 ohms also. If
you added more speakers in parallel, you'd get less than 4 ohms and
that would be bad.

This confusion makes more sense when you understan Ohm's Law. Look it
up.

> If you could answer that I think I will be straight.

Do you like girls now?


ulysses

[Rob Reedijk]

rothman > wrote:
> So I'm Cool then? Thanks for everyone's help!

I don't get it. Why have you not put one speaker on each amp, in bridged
mode. Why not?

Rob R.

[Rob Reedijk]

rothman > wrote:
> So I'm Cool then? Thanks for everyone's help!

I don't get it. Why have you not put one speaker on each amp, in bridged
mode. Why not?

Rob R.

[Monte P McGuire]

In article >,
Rob Reedijk > wrote:
>rothman > wrote:
>> So I'm Cool then? Thanks for everyone's help!
>
>I don't get it. Why have you not put one speaker on each amp, in bridged
>mode. Why not?

He only has two channels of amp I guess, which end up bridged to one channel.

If he has two stereo amps, each of which could be bridged, then it
would be best to do as you say and put one speaker on each bridged
amp.


Regards,

Monte McGuire

[Monte P McGuire]

In article >,
Rob Reedijk > wrote:
>rothman > wrote:
>> So I'm Cool then? Thanks for everyone's help!
>
>I don't get it. Why have you not put one speaker on each amp, in bridged
>mode. Why not?

He only has two channels of amp I guess, which end up bridged to one channel.

If he has two stereo amps, each of which could be bridged, then it
would be best to do as you say and put one speaker on each bridged
amp.


Regards,

Monte McGuire