What is the power rating into 4 Ohms?

What is the power rating into 4 Ohms?

Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
Ohms nominal loudspeaker system? I understand that it is rated at 70 wpc
into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.

Any info on this would be of great help. Thanks in advance.

-DJ

Re: What is the power rating into 4 Ohms?

In article <fl8iu302mkq@news4.newsguy . com >, wenwaudio@qwest . net says...
> Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
> Ohms nominal loudspeaker system? I understand that it is rated at 70 wpc
> into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.
>
> Any info on this would be of great help. Thanks in advance.
>
> -DJ
>
>
Google is your friend.

* w w w .arcam.co.uk/alpha/amps/ampalpha9.html

The last Arcam Alpha 9 was produced in Autumn 2000 after a 4 year run.
It produces over 70w/ch into 8ohms and 140w/ch into 4ohms (per the blurb
above the picture)
--

Re: What is the power rating into 4 Ohms?

DJ wrote:
> Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
> Ohms nominal loudspeaker system? I understand that it is rated at 70 wpc
> into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.
>
> Any info on this would be of great help. Thanks in advance.
>
> -DJ
>

That answer ought to be supplied by the manufacturer.
Email them, and download the owners manual??

However, *any amplifier* will drive a 4ohm or 2ohm load.
The limitation on that is the SOA or safe operating area of the output
devices. In practice this means that as long as you do not clip the
amp, or overheat it, it will work.

Also, you can't exceed the capabilities of the power supply in terms of
current. If you do, the amp will clip. So, it is unlikely that a small
amp's power supplyl will do 280wpc x 2 = 560watts into 2 ohms, see?

Since the nominal power approximately doubles as you halve the load
(with a low Z output, which is typical of solid state amps) that implies
that you'd expect something like 140wpc out of your Arcam amp into 4 ohms.

IF the practical limitation of the amp is 70 watts, and the equivalent
heat generation, then you can't get 140wpc from the amp. If you try,
the amp will either a)blow up; b)blow a fuse or c) go into a proctection
mode (if it has protection modes).

Otoh, the difference between 70 watts and 140 watts is only 3dB.

So, if you keep the volume down, you will probably find it will work fine.

Otoh, if this is an inefficient speaker, in a large room, and you like
relatively loud playback, this isn't the amp for you.

Re: What is the power rating into 4 Ohms?

On 30 Dec 2007 17:01:55 GMT, "DJ" <wenwaudio@qwest . net > wrote:

>Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
>Ohms nominal loudspeaker system? I understand that it is rated at 70 wpc
>into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.
>
>Any info on this would be of great help. Thanks in advance.
>
>-DJ

Try putting
arcam alpha 9 amplifier
into Google. The first Google result (for me) is one click from the
answer. [It's on the Arcam website.]

Re: What is the power rating into 4 Ohms?

On Sun, 2007-12-30 at 17:01 +0000, DJ wrote:
> Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
> Ohms nominal loudspeaker system? I understand that it is rated at 70 wpc
> into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.
>
> Any info on this would be of great help. Thanks in advance.
>
> -DJ
>

It should be able to safely drive 100 watts into 4 ohms. Unless the
loading of the speaker is such that it will drive the amplifier into
current limiting and thus have it shutdown (via protection
circuit/fuse).

Joe

Re: What is the power rating into 4 Ohms?

On Dec 30, 12:01 pm, "DJ" <wenwau...@qwest . net > wrote:
> Will an Arcam Alpha 9 integrated amplifier comfortably drive the average 4
> Ohms nominal loudspeaker system?  I understand that it is rated at 70 wpc
> into 8 Ohms, but I can't find any info on what it will do into 4 Ohms.
>
> Any info on this would be of great help.  Thanks in advance.
>
> -DJ

Bear pretty much nails it. But to fill out the skeleton some:

a) Any amp with a rating at (nominal) 8 ohms will drive any speaker
with a rating at a nominal 4 ohms. Whether the actual output will
higher or lower (or the same) into the reduced load is a matter of the
amplifier design - and somewhat of the speaker design.
b) Assuming a speaker of conventional elements and no internal
amplification, with a conventional crossover, there should be no
issues.
c) A conventionally designed Solid-State amp will typically put out
more watts into a lower-impedance speaker. Rule-of-thumb is about 1.6
- 2.0 x at 1/2 the impedance.
d) The magic term here is "impedance". A speaker may be *rated* at 4
ohms, but across the frequency spectrum, actual impedance may be as
little as 1/3 of the nominal rating at certain frequencies. So,
amplifier stability at very low impedances is critical when you are
starting at 4 ohms.

And where Bear *really* nailed it: CHECK WITH THE MANUFACTURERS! You
could do considerable damage to the amp (and/or the speakers) if there
is a mismatch.

Then there is the matter of headroom. You have given nothing about the
efficiency of your speakers. If 70 watts will do it, then 140 watts is
only a little bit more. If 70 watts won't do it, then 140 watts is
only a little bit more. Either way, if you are pushing limits at 70
watts, there is little likelyhood that you will gain any advantage at
140 watts excepting at the margins.

Peter Wieck
Wyncote, PA