PMPO Query

[jean]

Archived from groups: rec.audio.tech (More info?)

How is it possible?
An audio power amplifier with a 40v power supply,powering two 8 Ohm
speakers in parallel(Not a BTL load).Whatever it does,the maximum
power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
it written 5000W PMPO on it?

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Jean wrote:
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

Any manufacturer who uses PMPO ratings has a unhhh, certain reputation to
*protect*. This is how they do it. ;-)

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

alertjean@rediffmail.com (Jean) wrote in message news:<4138e33e.0405120850.64c289b@posting.google.com>...
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

They're liars. It's as simple as that. PMPO is a complete fantasy
"spec" that has absolutely NO physically justifiable meaning.
The claim is just outright dishonest, and the company knows it.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

>How is it possible?
>An audio power amplifier with a 40v power supply,powering two 8 Ohm
>speakers in parallel(Not a BTL load).Whatever it does,the maximum
>power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
>it written 5000W PMPO on it?

Because there is _no_ agreed-upon technical definition of PMPO,
because it means whatever the person writing the advertising
puff-sheet wants it to mean (presumably Bigger Is Better), and because
there appears to be no interest in Government circles in prosecuting
people for making meaningless or misleading claims in their advertising.

My own personal heuristic is this: if a product's ads or spec sheets
make _any_ mention of PMPO whatsoever, I assume that the product is a
steaming pile of fewmets and I don't buy it.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Jean <alertjean@rediffmail.com> wrote:
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

Easy.

PMPO is like dynamic headroom, but free from any legal requirements for
it to relate to anything at all.

Amp manufacturers should be required to advertise continuous RMS power
output for a sine wave at a given frequency. If they're going to advertise
peaks, they should be regulated as to what they're allowed to claim.

Colin

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Jean wrote:
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

Two ways to look at it
The first
They are bloody liars
The situation is even worse than you are describing because you will
feed your loudspeakers with a bunch of sinewaves. For a simple sinusoid
it is half the power you calculated. So 200 watt. Unless you want to
listen to square waves of course.

The second:
They are quite right
Loudspeakers have an impedance that is anything but straight. Depending
on the frequency of the signal they may have an impedance that is
significantly lower than rated.
The amplifier needs to be able to deliver enough current at these low
impedances too. Hence some reserve.



It might be an idea to give both the rated power at 4 (and/or 8 ohms)
ohms and the maximum power (=PMPO?) the amp can deliver.

kind regards
Bert Kraaijpoel

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Jean" <alertjean@rediffmail.com> wrote in message
news:4138e33e.0405120850.64c289b@posting.google.com...
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

Marketing watts. Back in the '70s, I think it was the FTC that required
amplifier manufacturers to rate power based on RMS output voltage under
specific continuous worst-case conditions. This was in response to the
myriad of "IHF" "Peak", and "Music Power" watts. It still wasn't perfect,
but it seems we've regressed a long way from "100 watts RMS, continuous
power, both channels driven into 8 ohms, 20 Hz - 20,000 Hz with < 0.1 %
total harmonic distortion" (or whatever), which IIRC, is how Heathkit used
to state their amplifier ratings.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Bert Kraaijpoel" <b.kraaijpoel@nowhere.ned> wrote in message
news:40a2774e$0$12753$4a441750@news.wanadoo.nl...
> Jean wrote:
> > An audio power amplifier with a 40v power supply,powering two 8 Ohm
> > speakers in parallel(Not a BTL load).Whatever it does,the maximum
> > power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> > it written 5000W PMPO on it?

> The situation is even worse than you are describing because you will
> feed your loudspeakers with a bunch of sinewaves. For a simple sinusoid
> it is half the power you calculated. So 200 watt. Unless you want to
> listen to square waves of course.

This is wrong too, because the "RMS" power output (actually average power
but that's another argument) is based on the RMS voltage and a nominal
resistive load. If the DC voltage is 40V total, then the max peak to peak
swing is a little less than that, peak voltage is half that, or < 20V, and
the RMS voltage is < 14V. So into 4 ohms the maximum "RMS" power is < 50
Watt.

TonyP.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

TonyP wrote:
> "Bert Kraaijpoel" <b.kraaijpoel@nowhere.ned> wrote in message
> news:40a2774e$0$12753$4a441750@news.wanadoo.nl...
>
>>Jean wrote:
>>
>>>An audio power amplifier with a 40v power supply,powering two 8 Ohm
>>>speakers in parallel(Not a BTL load).Whatever it does,the maximum
>>>power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
>>>it written 5000W PMPO on it?
>
>
>>The situation is even worse than you are describing because you will
>>feed your loudspeakers with a bunch of sinewaves. For a simple sinusoid
>>it is half the power you calculated. So 200 watt. Unless you want to
>>listen to square waves of course.
>
>
> This is wrong too, because the "RMS" power output (actually average power
> but that's another argument) is based on the RMS voltage and a nominal
> resistive load. If the DC voltage is 40V total, then the max peak to peak
> swing is a little less than that, peak voltage is half that, or < 20V, and
> the RMS voltage is < 14V. So into 4 ohms the maximum "RMS" power is < 50
> Watt.
>
> TonyP.
>
>
>
You are quite right. I calculated a bit too fast. Peak in stead of peak
peak.
thanks for the correction.
kind regards
Bert

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Jean" <alertjean@rediffmail.com> wrote in message
news:4138e33e.0405120850.64c289b@posting.google.com...
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

It is not possible, it is a lie. I bought a pair of cheap computer speakers
that were rated 80+80 watts PMPO. They had a 6 volt supply and a 8 pin DIP
IC for the stereo amplifier. I did not buy them for that rating, I bought
them because they were $8. I needed basic sound for the computer.
John

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Jean" <alertjean@rediffmail.com> wrote in message
news:4138e33e.0405120850.64c289b@posting.google.com...
> How is it possible?
> An audio power amplifier with a 40v power supply,powering two 8 Ohm
> speakers in parallel(Not a BTL load).Whatever it does,the maximum
> power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
> it written 5000W PMPO on it?

**Ignore it. The figure is essentially meaningless anyway. I just took
delivery of a new computer. With it came the obligatory computer speakers.
The box proudly proclaims them to be 300 Watt PMPO. In small writing, down
one side, the manufacturer acknowledges them to be rated at 3 Watts RMS.
Even that figure is optimistic, IMO. I'd reckon the transformer is good for,
maybe, 2VA, tops. I'd figure on about 0.5 Watts continuous. I'll measure
them later on.


--
Trevor Wilson
www.rageaudio.com.au

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Arny Krueger wrote:

> Jean wrote:
>
>>How is it possible?
>>An audio power amplifier with a 40v power supply,powering two 8 Ohm
>>speakers in parallel(Not a BTL load).Whatever it does,the maximum
>>power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
>>it written 5000W PMPO on it?
>
>
> Any manufacturer who uses PMPO ratings has a unhhh, certain reputation to
> *protect*. This is how they do it. ;-)
>
>

Surely you wouldn't insinuate that a little known Chineese
computer speaker manufacturer would embellish their power ratings,
now would you? ;-p

--
Check out the gaming & computer forums at the [SS] clan site.
http://www.shamikaserver.com

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

>
>Arny Krueger wrote:
>
>> Jean wrote:
>>
>>>How is it possible?
>>>An audio power amplifier with a 40v power supply,powering two 8 Ohm
>>>speakers in parallel(Not a BTL load).Whatever it does,the maximum
>>>power it can deliver to the load is VxV/R i.e 40x40/4=400W.Then why is
>>>it written 5000W PMPO on it?
>>
>>
>> Any manufacturer who uses PMPO ratings has a unhhh, certain reputation to
>> *protect*. This is how they do it. ;-)
>>
>>
>
> Surely you wouldn't insinuate that a little known Chineese
>computer speaker manufacturer would embellish their power ratings,
>now would you? ;-p
>


Pretty amazing how a company can get 50 watts out of a device powered by a wall
wart that puts out 12 Volts 1/2 amp.
I've actually seen that on some computer Subwoofers.

Lool at how much power the system consumes (it is printed somewhere on the
system or power supply) Half that and you will be pretty close to power output.
Distortion isn't figured into that however.
Richard H. Kuschel
"I canna change the law of physics."-----Scotty

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

rickpv8945@aol.com (Richard Kuschel) writes:
> [...]
> Pretty amazing how a company can get 50 watts out of a device powered by a wall
> wart that puts out 12 Volts 1/2 amp.
> I've actually seen that on some computer Subwoofers.

Maybe their engineers were playing hookie the day they covered the law of
the conservation of energy.
--
% Randy Yates % "Ticket to the moon, flight leaves here today
%% Fuquay-Varina, NC % from Satellite 2"
%%% 919-577-9882 % 'Ticket To The Moon'
%%%% <yates@ieee.org> % *Time*, Electric Light Orchestra
http://home.earthlink.net/~yatescr

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Randy Yates" <yates@ieee.org> wrote in message
news:wu31gb42.fsf@ieee.org...
> rickpv8945@aol.com (Richard Kuschel) writes:
> > [...]
> > Pretty amazing how a company can get 50 watts out of a device powered by
a wall
> > wart that puts out 12 Volts 1/2 amp.
> > I've actually seen that on some computer Subwoofers.
> Maybe their engineers were playing hookie the day they covered the law of
> the conservation of energy.

Not at all. Whilst PMPO has no real meaning, the *Peak* (music) power
delivered to a speaker has very little to do with the continuous VA rating
of the power supply.
The engineers probably put a capacitor in the power supply! I've never seen
one that didn't.

TonyP.