New Posts New Posts RSS Feed - Peak Momentary Power Output PMPO
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Welcome to the Graham Slee Audio Products Owners Club

 

Open to all owners plus those contemplating the purchase of a Graham Slee audio product wishing to use our loaner program: join here
Subscribe to our newsletter here (Rules on posting can be found here)


Peak Momentary Power Output PMPO

 Post Reply Post Reply
Author
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Telling it as it is

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 8657
Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Topic: Peak Momentary Power Output PMPO
    Posted: 31 Jul 2016 at 1:57am
Seen all those amps and systems that supposedly do thousands of watts?

And some are from previously reputable brands. Some may think they're still reputable but how can they be when they start misleading people?

OK, most of these misled people are the youth generation right now, and I guess the reputable brands have to compete but in doing so they are being very economical with the truth.

PMPO stands for peak momentary power output, and at one time the brands would qualify their power output claims by saying PMPO - but now it seems they've stopped qualifying it at all!

My attention was recently drawn to a couple of amped plastic desktop speakers claiming 3000 watts with no qualification and an asking price of over £2000. This being sold on Amazon so it must be OK?

How loud is 3000 watts going to be? Very loud! A band with a 300 watt PA can sound very loud in a concert room (around 3000 sq ft) so 3000 watts is going to sound twice as loud and probably be just sufficient for an arena?

And all that power is coming from a couple of desktop plastic bluetooth speakers? I don't think so!

It would have been more honest to claim 3000 watts PMPO. At least that would say what its peak momentary power output is.

But what is peak momentary power output?

It is the absolute maximum of power output that can be produced in a very short interval of time - possibly a microsecond - nobody ever says.

So let's see how much PMPO my Proprius amps can do...

If I short out the speaker terminals whilst running the amp flat out into an 8 Ohm load at full output swing - a continuous sine wave - the power supply shuts down, but it cannot do that instantly - it is probably a microsecond or so.

But into a short circuit there cannot be any sound output. We will have to make it less than a short circuit. Let's call it 0.1 ohms. You see, PMPO is never quoted into any particular load.

OK, if it does 25 watts into 8 ohms, the square of the voltage swing is 200 (14.14V rms), so let's now divide that by 0.1. I get 2000 watts PMPO.

But I could make the load 0.05 ohms which gives me 4000 watts PMPO, so if I was up against a brand advertising a 25 rms watt amp at 2000 watts PMPO, I could get away with saying 4000 watts PMPO, so the youths would buy mine instead!

However, because I would never dream of advertising a 25 rms watt amp as being anything other than that, I will never sell one to a typical youth.

Not simple enough for Google-Bot to understand...
Back to Top
BAK View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 Mar 2010
Location: Kentucky, USA
Status: Offline
Points: 904
Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2016 at 4:04am
Graham, Very well stated.
PMPO is for the uneducated.
RMS power (root-mean-square) is real power and is qualified by giving a tested load impedance... ie, 25 watts RMS into 8 ohm load.
Bruce
AT-14SA, Pickering XV-15/625, Technics SL-1600MK2, Reflex M, Lautus, Technics SH-8066, Dynaco ST120a, Eminence Beta 8A in custom cabs;; Using Majestic DAC
Enjoy Life Your Way!
Back to Top
BackinBlack View Drop Down
Senior Member
Senior Member
Avatar

Joined: 05 Feb 2012
Location: Hinton, N'hants
Status: Offline
Points: 1360
Post Options Post Options   Thanks (0) Thanks(0)   Quote BackinBlack Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2016 at 8:25am
IIRC, in the 60s and early70s PMPO was a commonly quoted spec in budget "HiFi" and Music centres, predominantly those coming from Japan along with all the meaningless acronyms describing their supposed features.
Some things don't change.
Just listen, if it sounds good to you, enjoy it.
Back to Top
JamesD View Drop Down
Senior Member
Senior Member
Avatar

Joined: 05 Nov 2012
Location: Bolsover
Status: Offline
Points: 246
Post Options Post Options   Thanks (0) Thanks(0)   Quote JamesD Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2016 at 1:07pm
From college many years ago I thought maximum power transfer was when the load resistance equaled the source resistance so maybe there's room to push the PMPO figure even higher...
Aren't ears brilliant
Back to Top
BAK View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 Mar 2010
Location: Kentucky, USA
Status: Offline
Points: 904
Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2016 at 1:13pm
Originally posted by BackinBlack BackinBlack wrote:

IIRC, in the 60s and early70s PMPO was a commonly quoted spec in budget "HiFi" and Music centres, predominantly those coming from Japan along with all the meaningless acronyms describing their supposed features.
Some things don't change.


Yes, Ian, that is the prevailing advertising method.
The manufacturer will state the PMPO as Peak Music Power Output to make the uneducated think their amplifier produces more power than it actually can.

In 1973 I worked in a C***H***T stereo factory.
I was testing & repairing complete stereo chassis sent from Japan and China that were put into cabinets here.
Their stereo amplifiers were advertised with a rating of 80 watts per channel
Peak Music Power Output... the power amplifier ICs they used actually put out: 2.5 watts RMS into 8 ohms with 1% THD, 5 watts RMS with 10% THD.
 People were buying this stuff under 5 different brand names!


Edited by BAK - 31 Jul 2016 at 1:16pm
Bruce
AT-14SA, Pickering XV-15/625, Technics SL-1600MK2, Reflex M, Lautus, Technics SH-8066, Dynaco ST120a, Eminence Beta 8A in custom cabs;; Using Majestic DAC
Enjoy Life Your Way!
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.092 seconds.