RCF watt? |
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LjudLahger
Young Croc Joined: 31 July 2008 Location: Sweden Status: Offline Points: 838 |
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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 |
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csg
Old Croc Joined: 17 September 2007 Location: bedford Status: Offline Points: 6086 |
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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.
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“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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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.
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10920 |
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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. |
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LjudLahger
Young Croc Joined: 31 July 2008 Location: Sweden Status: Offline Points: 838 |
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Thank you all for your input with awesome info
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Sonic the hedge
Registered User Joined: 12 May 2020 Status: Offline Points: 161 |
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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 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 |
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10920 |
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I'll let the folk at Klippel cover that one
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 |
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4D
Old Croc Joined: 13 November 2008 Location: Winchester Status: Offline Points: 4257 |
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As ever succinctly informative..
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DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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