Speakerplans.com Homepage
Forum Home Forum Home > General > Newbie Discussion
  New Posts New Posts RSS Feed - RCF watt?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

RCF watt?

 Post Reply Post Reply
Author
Message
LjudLahger View Drop Down
Young Croc
Young Croc


Joined: 31 July 2008
Location: Sweden
Status: Offline
Points: 838
Post Options Post Options   Thanks (0) Thanks(0)   Quote LjudLahger Quote  Post ReplyReply Direct Link To This Post Topic: RCF watt?
    Posted: 27 October 2021 at 9:18pm
I got a pair of cabs with RCF L15P/200 AK (green backplate) in very good condition.
But I don't know how to read the power figures, in modern use.
Info I find say

Long-term Power (W) - 300
Program Power (W) - 600
100 Hours IEC P (W) - 700
AES P (W) - 800

Could the AES be the same as they measure today?

Thank's.


Edited by LjudLahger - 27 October 2021 at 9:20pm
Back to Top
csg View Drop Down
Old Croc
Old Croc


Joined: 17 September 2007
Location: bedford
Status: Offline
Points: 6086
Post Options Post Options   Thanks (1) Thanks(1)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2021 at 9:55pm
Ive always treated this driver as a 600w “rms” unit, would employ a 40v RMS limiter with a 2 second attack, 8 second release, with a peak limiter of 135V of 2ms, 32ms release.

Nice driver, these were my preferred driver in my lovely old Nexo SI2000 bass cabs.
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
Back to Top
Conanski View Drop Down
Old Croc
Old Croc
Avatar

Joined: 26 January 2006
Location: Ottawa, Canada
Status: Offline
Points: 2515
Post Options Post Options   Thanks (1) Thanks(1)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2021 at 10:28pm
AES spec uses a noise signal with 6dB crest factor... that is the peak to average ratio. The IEC spec used a similar signal with additional factors for bandwidth and duration. 
Peak ratings using these specs were simply 2x the continuous rating, the catch is you have to realize that means the peak signal has a 12dB crest factor. The old school RMS(sine wave) rating should be cosidered to be 1/2 AES.
Back to Top
toastyghost View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 09 January 2007
Location: Manchester
Status: Offline
Points: 10920
Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2021 at 8:28am
Originally posted by Conanski Conanski wrote:

. The old school RMS(sine wave) rating should be cosidered to be 1/2 AES.


RMS Voltage. The average power was then calculated from this value, based on the impedance minimum (possibly the value of Re) or worse yet, whatever frequency the marketing team decided gave the biggest number.

Guess what? That was, and still is, the fundamental method in the AES standard. First the '84 revision, and then the later revision to use a 12 dB crest factor (4:1 peak to average) based on the nominal impedance to better represent the fact we play music with these things instead of welding.

People act like the standard is confusing, but it's a damn sight better than the 'bad old days' when people did whatever they wanted. Let alone the bloody 'RMS Watts' bollocks.

Peak output is far more useful with a dynamic signal, and is harder to achieve in many circumstances. If you're trying to run your components based on the 3 dB crest factor of a sine wave signal, not only are you causing havoc with the thermal envelope but you're stuffed when I come along and ask the system to play a kickdrum...

Here's a good chart of the different filtered signal bandwidths across the AES, IEC and EIA standards:

Taken from https://www.doctorproaudio.com/content.php?2260-loudpeaker-power-handling which I recommend reading.

Nevertheless, at no point was any driver rated by an actual measurement of power. It is always calculated from Ohm's law, regardless of standard.

If you want measured values for real Power over time, you need Klippel data from the manufacturer. You also need to know how to read it, but it contains far more useful things like Bl(x) and Kms(x).

The power rating of a transducer will be different once you put it in a box, anyway.
Back to Top
LjudLahger View Drop Down
Young Croc
Young Croc


Joined: 31 July 2008
Location: Sweden
Status: Offline
Points: 838
Post Options Post Options   Thanks (0) Thanks(0)   Quote LjudLahger Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2021 at 7:44pm
Thank you all for your input with awesome infoClap
Back to Top
Sonic the hedge View Drop Down
Registered User
Registered User


Joined: 12 May 2020
Status: Offline
Points: 161
Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2021 at 8:33pm
Originally posted by toastyghost toastyghost wrote:


Nevertheless, at no point was any driver rated by an actual measurement of power. It is always calculated from Ohm's law, regardless of standard.

 
So the issue is not that 'watts' per se are 'wrong', but the way they are conventionally 'measured' (calculated IRL) WRT to driver rating, is highly inaccurate/misleading? 

I must confess I struggled with your constant assertion that 'watts are bollocks' but that explanation totally clears it up. And to be fair a lot of the 'old school' guys never took much notice of thermal power ratings anyway, so it looks like they agree with you Tongue

Anyways good explanation, thanks. 

Edit: Nice link also BTW, recommended reading! Here's a clickable URL for lazy people...




Edited by Sonic the hedge - 28 October 2021 at 11:11pm
Back to Top
toastyghost View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 09 January 2007
Location: Manchester
Status: Offline
Points: 10920
Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2021 at 1:54pm
I'll let the folk at Klippel cover that one
Quote
The high crest factor (Cu > 12 dB) of common audio signals makes the peak voltage to a more limiting factor in amplifiers than the long-term power capabilities. This becomes even worse in efficient transducers having a high motor efficiency factor Bl2 / RE that increases the electric damping, giving a
low-quality factor (e.g. QTS < 0.3 in woofers) and low voltage sensitivity at the resonance frequency fs.


Borrowed from their library of papers on efficiency and non-linear control methods, all available open access on their site.

Watts used are a function of the required peak voltage required to deliver the signal - loudspeakers are voltage driven devices. The current demand from the amplifier is a function of the frequency-dependent impedance curve, which in turn gives the Watts used. It is almost always a calculation, even on most DSP amplifiers with thermal limiters. That’s not a problem per se, because the Wattage used isn’t really what we care about in most end-user cases, as shown above.

If you watch Bennett Prescott’s excellent videos on transducer power ratings you’ll get an even better understanding. I can’t remember if he shows the examples, but the Klippel data for real Power on their (very bloody good) high power transducers is telling. It’s also not lying, as lots of people seem to think. The problem is a lack of understanding - the AES spec itself is very clear on all this stuff.

The simplest answer I can think of for the whole use of Watts in specifications back in the day was familiarity (a holdover from transmission lines perhaps) and the fact the numbers were big for the marketing departments.

Edited by toastyghost - 02 November 2021 at 2:02pm
Back to Top
4D View Drop Down
Old Croc
Old Croc


Joined: 13 November 2008
Location: Winchester
Status: Offline
Points: 4257
Post Options Post Options   Thanks (0) Thanks(0)   Quote 4D Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2021 at 7:07pm
Originally posted by csg csg wrote:

Ive always treated this driver as a 600w “rms” unit, would employ a 40v RMS limiter with a 2 second attack, 8 second release, with a peak limiter of 135V of 2ms, 32ms release.

Nice driver, these were my preferred driver in my lovely old Nexo SI2000 bass cabs.

As ever succinctly informative..
DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.156 seconds.