Here's a basic amp question for all the experts here.

Say a stereo amp is rated 100wpc. It has 2 speaker out posts, though,
and a switch for "Speaker A, Speaker B" (or both). it's a 2channel
amp so if hooked up to 2 speakers, does it then power at 50wpc for all
4 speakers or is it in parallel so still powers at 100wpc?

Also, i understand that most people say that speakers sound better
when bi-wired. What is the best way to bi-wire? My B&W801s have 2
sets of speakers posts with a shunt that connects them. I am
connecting my amp to one set and it is concurrently powering both
drivers. I have seen bi-wire cable that goes from 1 set of speaker
terminals on an amp and splits to 2 sets of speaker connectors. it
had a writeup regarding the type of wire for each and how some
"frequency" transmits better across one of the conductors than others.

SO is it best to (a) cable from amp to speakers and use the speakers'
shunt to bi-wire (b) use bi-wire cabling (c) connect separate cable
from each of the amp's speaker out terminals. Does getting a separate
identical amp and wiring that to the separate driver offer any
performance upgrade to (a-c)?

thx in advance
-goro-

On Thu, 11 Dec 2003 21:08:55 GMT, (Evil) wrote:

Here's a basic amp question for all the experts here.

Say a stereo amp is rated 100wpc. It has 2 speaker out posts, though,
and a switch for "Speaker A, Speaker B" (or both). it's a 2channel
amp so if hooked up to 2 speakers, does it then power at 50wpc for all
4 speakers or is it in parallel so still powers at 100wpc?


This is something you see in home stereo more than car stereo. If the
amp is rated at 100 Wpc into two channels, then that's what it will
deliver into your two "A" speakers. If you have it power the "B"
speakers at the same time, then not all four will be getting 100 watts
each. Without knowing how the 2nd set of speakers is wired into the
circuit, it's impossible to tell just how many watts each of the four
speakers will get.

Also, i understand that most people say that speakers sound better
when bi-wired. What is the best way to bi-wire? My B&W801s have 2
sets of speakers posts with a shunt that connects them. I am
connecting my amp to one set and it is concurrently powering both
drivers. I have seen bi-wire cable that goes from 1 set of speaker
terminals on an amp and splits to 2 sets of speaker connectors. it
had a writeup regarding the type of wire for each and how some
"frequency" transmits better across one of the conductors than others.

SO is it best to (a) cable from amp to speakers and use the speakers'
shunt to bi-wire (b) use bi-wire cabling (c) connect separate cable
from each of the amp's speaker out terminals. Does getting a separate
identical amp and wiring that to the separate driver offer any
performance upgrade to (a-c)?

thx in advance
-goro-

If you do scenario "a", then you're not bi-wiring. Using the shunt
across the two sets of terminals is for when you *don't" want to
bi-wire.

"Bi-wiring" is one of those "audiophile" things that some people claim
makes a "huge" difference in the sound, but no one can ever reliably
tell the difference between a bi-wired system and a
conventionally-wired system in double-blind tests.

All bi-wiring means is that you're sending the exact same signal from
your amp output terminals to two different speakers, using two
different pairs of wires. Electrically, you're connecting the two
divers together in parallel, but rather than using the shunt at the
back of the speaker cabinet, your running separate wires to each
driver and terminating them at the same place at the amplifier.

The theory is that by running separate wires to each driver (usually a
tweeter and a sub), each wire pair would somehow "optimize" itself for
the particular driver it was powering. Also, the "delicate treble
signals" wouldn't have to ride the same cable as those "slow, clumsy
bass signals". You can see what I think about bi-wiring - I think
it's a lot of audiophile hocus-pocus that hasn't been able to stand up
to scrutiny. Just one one wire pair from you amp to your speaker
cabinet, and use the shunt to parallel the two drivers.

As for getting a separate amp and using it to power some of the
drivers, that's "bi-amping", not "bi-wiring". and it does have some
benefits, most noticeably being more power.

Scott Gardner

I would'nt be so dogmatic about declining to bi-wire. I would try it both ways
and let your ears decide. There are many variables and from experience with my
ML Aerius' I can tell you that they definitely sound better bi-wired. -Bob
Bernstein.

On 12 Dec 2003 03:17:28 GMT, (RBernst929) wrote:

I would'nt be so dogmatic about declining to bi-wire. I would try it both ways
and let your ears decide. There are many variables and from experience with my
ML Aerius' I can tell you that they definitely sound better bi-wired. -Bob
Bernstein.


Good point - thanks for reining me in. It certainly isn't going to
cost him much to give it a try both ways.

Scott Gardner

Scott Gardner wrote:

On Thu, 11 Dec 2003 21:08:55 GMT, (Evil) wrote:

Here's a basic amp question for all the experts here.

Say a stereo amp is rated 100wpc. It has 2 speaker out posts, though,
and a switch for "Speaker A, Speaker B" (or both). it's a 2channel
amp so if hooked up to 2 speakers, does it then power at 50wpc for all
4 speakers or is it in parallel so still powers at 100wpc?


This is something you see in home stereo more than car stereo. If the
amp is rated at 100 Wpc into two channels, then that's what it will
deliver into your two "A" speakers. If you have it power the "B"
speakers at the same time, then not all four will be getting 100 watts
each. Without knowing how the 2nd set of speakers is wired into the
circuit, it's impossible to tell just how many watts each of the four
speakers will get.

In the majority, this is incorrect.

Regardless of what the "rating" of the amp is, all amplifiers will deliver
different amounts of power to a load depending upon the *impedance*
of the load.

Assuming it is a nominal 100 watts RMS per channel amplifier - which
is *different* than the tag on the back of typical consumer gear that lists
the power draw from the *wall* socket - it is rated at this power into some
load impedance. The standard load impedance for *most* amplifiers is
8 ohms. This doesn't mean that your amp was rated into 8 ohms.

So, if the amp puts 100 watts RMS into 8 ohms it will TRY to double
that power into *half* the impedance, or 200 watts @ 4 ohms. Since
most amplifiers have internal losses, it probably will fall short of *double*
power into half the impedance.

This *assumes* that the amp *can* double its power, which requires that
the output voltage remain the same, and the current *doubles*. This
requires two important things: 1) that the power supply can deliver
the extra current and 2) that the output section can deliver the power
and dissipate the extra heat. Not all amps can do this. As the impedance
drops *below* 4 ohms, this becomes increasingly demanding and
many amps will not perform well at all.

Since you are talking about running TWO sets of speakers, you have
to expect that the *nominal* impedance will be that of the two loads
in parallel - half. IF they were resistors, then it would be exactly the
same as two resistors in parallel, and if they were both 8 ohms then
the result would be 4 ohms. BUT, if they are both *less* than 8 ohms
in reality, and *not equal*, then the parallel combination will be *less*
than 4 ohms and not exactly half of 8.

Here's the rub - unless both pairs of speakers are *identical* (same
model, no differences) running them in parallel is a spectacularly
*bad* idea. This is because speakers are *not* resistive loads at all,
and the combination of the two in parallel can and will produce
unpredicatable variations in impedance and phase angle. In the most
extreme case, like in the SR/PA applications where they are run at
or near their power limits, this can cause *one* driver to "hog" power
and get fried. Even in home use, you can have problems with the amp
running out of headroom, over heating, and unpredicatable variations
in frequency response.



Also, i understand that most people say that speakers sound better
when bi-wired. What is the best way to bi-wire? My B&W801s have 2
sets of speakers posts with a shunt that connects them. I am
connecting my amp to one set and it is concurrently powering both
drivers. I have seen bi-wire cable that goes from 1 set of speaker
terminals on an amp and splits to 2 sets of speaker connectors. it
had a writeup regarding the type of wire for each and how some
"frequency" transmits better across one of the conductors than others.

SO is it best to (a) cable from amp to speakers and use the speakers'
shunt to bi-wire (b) use bi-wire cabling (c) connect separate cable
from each of the amp's speaker out terminals. Does getting a separate
identical amp and wiring that to the separate driver offer any
performance upgrade to (a-c)?

thx in advance
-goro-

If you do scenario "a", then you're not bi-wiring. Using the shunt
across the two sets of terminals is for when you *don't" want to
bi-wire.

Correct.



"Bi-wiring" is one of those "audiophile" things that some people claim
makes a "huge" difference in the sound, but no one can ever reliably
tell the difference between a bi-wired system and a
conventionally-wired system in double-blind tests.

This is not a fact, it's the poster's opinion - but there are measureable
differences between a bi-wired system and a jumpered system if for
no other reason than you are hanging two sets of capactive and
inductive cables off an amp vs. one. Some people like what they
subjectively percieve as the result of doing this. If it makes no
difference to you, then it doesn't matter.



All bi-wiring means is that you're sending the exact same signal from
your amp output terminals to two different speakers, using two
different pairs of wires. Electrically, you're connecting the two
divers together in parallel, but rather than using the shunt at the
back of the speaker cabinet, your running separate wires to each
driver and terminating them at the same place at the amplifier.

The theory is that by running separate wires to each driver (usually a
tweeter and a sub), each wire pair would somehow "optimize" itself for
the particular driver it was powering. Also, the "delicate treble
signals" wouldn't have to ride the same cable as those "slow, clumsy
bass signals".

I don't know who chatacterizes things this way. But, clearly the use of
a very inductive cable on the tweeter would have an effect, while
not effecting a connection to say a midrange driver made through
a not inductive cable...

You can see what I think about bi-wiring - I think
it's a lot of audiophile hocus-pocus that hasn't been able to stand up
to scrutiny. Just one one wire pair from you amp to your speaker
cabinet, and use the shunt to parallel the two drivers.

Or not.



As for getting a separate amp and using it to power some of the
drivers, that's "bi-amping", not "bi-wiring". and it does have some
benefits, most noticeably being more power.

Actually that is not accurate. The power available to the load *might*
be the same or less or more depending upon the power of the amp itself,
the sensitivity of the driver being driven and the impedance of the
load when separated, as compared to combined. What you will likely
get is effective *headroom* in some cases, assuming a x-over at
the *input* of the amps, and that the amps are not driven full range.
The headroom benefit in the majority coming from reducing the
maximum "duty cycle" (power vs. bandwidth vs time) that is
required of a given amp.

In practice, this may or may not have an audible effect or even
a technically beneficial result - much depends upon the specifics
of the amps and the load.



Scott Gardner

_-_-bear


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