T.D. Posted February 22, 2005 Share Posted February 22, 2005 OK, Hand up, I'm really a lampy with a 'bit' of sound knowledge - so please be gentle..... 100V line systems to be used as emergency public address on outdoor events, but also for hire stock so preferably not going to sound like a station masters anouncement. Ideally able to play background musak 1/We have some old Millbank Ultima 1205 amps that we could use but they've seen better days so will need some service/repair - does anyone have any tips, and can they be run from 24V DC without an inverter (modification perhaps) 2/Secondly, we're looking for speakers. I'm swaying towards RCF 'DP 1420' sound projectors see RCF web page but don't know how they'll compare to the traditional horns. Is coverage JUST down to SPL at 1m, then 6dB drop off every time you double the distance, or does the type of speaker effect it as well. The DP 1420's are listed at 108dB/1 m which is higher than many of the horns. thanks for any words of wisdom.... T.D. Link to comment Share on other sites More sharing options...
Lamplighter Posted February 22, 2005 Share Posted February 22, 2005 Secondly, we're looking for speakers. I'm swaying towards RCF 'DP 1420' sound projectors see RCF web page but don't know how they'll compare to the traditional horns. T.D.<{POST_SNAPBACK}> TD The quoted spl is at rated music power, not the usual 1 watt @ 1 metre. I would also feel unhappy with IP 36 outdoors in this country. Brian Link to comment Share on other sites More sharing options...
Brian Posted February 22, 2005 Share Posted February 22, 2005 100V line systems to be used as emergency public address on outdoor events, but also for hire stock...If they are really going to be used for emergency systems then you should know that there are some quite stringent standards laid down for such use. Link to comment Share on other sites More sharing options...
T.D. Posted February 24, 2005 Author Share Posted February 24, 2005 Thanks folks Lamplighter: The quoted spl is at rated music power, not the usual 1 watt @ 1 metre. I would also feel unhappy with IP 36 outdoors in this countryis there any way of compareing the two? I think I understand the 1 watt @ 1 meter, but don't really know how they get the rated music power. Is it rms, peak, three bears singing into a miced up honey pot? Brain:Any idea where I could find out more about regs and standards governing emergency PA's? thanks again T.D. Link to comment Share on other sites More sharing options...
Brian Posted February 24, 2005 Share Posted February 24, 2005 Any idea where I could find out more about regs and standards governing emergency PA's? BS 5839-8 Code of Practice for the design, installation and servicing of voice alarm systems. Link to comment Share on other sites More sharing options...
Lamplighter Posted February 24, 2005 Share Posted February 24, 2005 Thanks folks Lamplighter: The quoted spl is at rated music power, not the usual 1 watt @ 1 metre. I would also feel unhappy with IP 36 outdoors in this countryis there any way of compareing the two? I think I understand the 1 watt @ 1 meter, but don't really know how they get the rated music power. Is it rms, peak, three bears singing into a miced up honey pot? Brain:Any idea where I could find out more about regs and standards governing emergency PA's? thanks again T.D.<{POST_SNAPBACK}> TD Quoting the RCF website "Sound pressure level at music power; 108dB/1m"and "Music Power/RMS 40/20W" If you are bold enough to assume that the unit is delivering 108dB@1metre with an input of 20W then this might be assumed to equate to an SPL of 95dB for 1 watt @ 1 metre. There are rather a lot of assumptions, mights and even guesses in this! I think I would need a test against a proper standard if I were to use this as a basis for a real world design. Brian Link to comment Share on other sites More sharing options...
T.D. Posted February 25, 2005 Author Share Posted February 25, 2005 If you are bold enough to assume that the unit is delivering 108dB@1metre with an input of 20W then this might be assumed to equate to an SPL of 95dB for 1 watt @ 1 metre. How did you get to the 95dB? I've found 'DNH's web site' (who manufacture something 'remarkably similar looking' do the point of surely being the same) quote the following figures "Rated / max. power 15W / 20 W "" SPL 1W/1m 92 db "" SPL rated power 103 db " ....this suggest your're calculations to be roughly spot on (if that's not a contradiction) even if their figures dont match RCF's. hmmm - perhaps the RCF badge on the front improves the units resonance and gives them an extra few dB. T.D. Link to comment Share on other sites More sharing options...
Lamplighter Posted February 25, 2005 Share Posted February 25, 2005 TD How did I get 95dB ? 1 watt is 13dB below 20 watts (10 log P1/P2) 108 - 13 = 95 Brian Link to comment Share on other sites More sharing options...
T.D. Posted March 7, 2005 Author Share Posted March 7, 2005 I've had a look into the BS standards and must say am not keen on spending £492 to buy a copy so will be looking into sourceing a copy to look at from the library. Regarding non-emergency applications. I'm looking to provide spoken word along a roadway and perimeter. There will not be any significant backround noise aside from the crowd gathering (around 250 people) at each end. When I work out the distance between speakers does anyone have a suggestion for a min SPL I should be aiming to achieve and how would I allow for the effects of wind (obviously an unknown). Its moderately exposed. I'm guessing I should be looking for around 70dB? T.D. Link to comment Share on other sites More sharing options...
david@audioleisure.com Posted April 8, 2005 Share Posted April 8, 2005 If you would like a copy of a little program that I compiled in VB for several audio application calculations, including decibel calcs and loudspeaker placement let me know and I will be pleased to give you a copy gratis. Its quite useful. Link to comment Share on other sites More sharing options...
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