rob.d Posted September 23, 2006 Share Posted September 23, 2006 Hi again folks If you've got a top box with a rated continuous output of 125db/ 1m, to get a nice balance from a sub, what kind of output does it need to produce continuos? I've always been told use the 3:2:1 ratio for bottom-mid-top, or maybe even 4:2:1 in the amp rack, but isnt continous db output represent a more reliable measure? Do I need 130db from the bins? If not what would I need? All this assuming the program material is common garden pop/ rock, maybe a splash of dancier tunes here and there.. Cheers Rob Link to comment Share on other sites More sharing options...
Chris Hinds Posted September 23, 2006 Share Posted September 23, 2006 The answer is always "it Depends" I'm afraid. I've never used a set ratio for a system. I did a classical concert for 8000 earlier this year with only 4 D&B Q Subs at the front and nothing on the delays, but then for dancy events I've done 2 Nexo B1-18 to one eM which is more bottom end than is usually there. I have generally for recorded music had more low end than high end. The things is that your speaker system is never working at max level continuously. Basically if you have a certain generic 12"+1" box then I'd use the same mfrs 15" or 18" bin and do the adjustments on the crossover/DSP until it sounds balanced. Hope that's of some use Regards Chris Link to comment Share on other sites More sharing options...
rob.d Posted September 23, 2006 Author Share Posted September 23, 2006 Hi chris Cheers for the response. I guess for the most part, what you said is as much as I guessed.. I realise there's no hard and fast rule for this sort of thing, and of course, the program material determines it to a large extent. My thinking behind the post was, before you take into account the extra power you need to move the "weight" of sub vs mid and top (in terms of the 4:2:1) ratio, doubling amp power will give 3 db (or is it 6?), ceteris paribus. So I suppose my question is... If my 125 db top box is biamped, and 250 drive the highs, 500W into mids to generate that sound pressure, is the 750w/ 1000w (depending on what ratio you use), normally sufficient to give what level of sound pressure from the bins (assume the program is pink noise, if you wish)? I dont know if this boils down to maths or what not, but I'm actually a drummer, and therefore anything difficult or requiring brain power of any kind is destined to leave my head hurting a bit.. Is the ratio naff? if it takes no account of box efficiency? Cheers rob Link to comment Share on other sites More sharing options...
mikewheeler Posted September 24, 2006 Share Posted September 24, 2006 Hi Rob, You are right in some ways - in thinking of a ratio in decibels of SPL rather than watts. The relationship between how much power a speaker will take from an amp and what it will chuck out the front in terms of decibels or acoustic watts is very different - dependant largely on the type of enclosure. As an example, a well-designed reflex enclosure might be approaching 10% efficiency in extreme best-cases, yet a well designed horn enclosure will be in the 40-45% efficiency bracket. Suddenly your 1000W makes a lot more acoustic output! Chris is also right - in that I don't think there is a set formula for the bin/top ratio - although sometimes manufacturers will publish recommended numbers of subs/tops for a particular system. The best bet is set a system up and try it....that's where the fun is anyway! Cheers, Mike Link to comment Share on other sites More sharing options...
Ben Lawrance Posted September 24, 2006 Share Posted September 24, 2006 I think as Chris has stated, it depends what your application is. If your doing classical (like Chris did) you don't need huge amounts of bottom end. However, if your supplying Fatboy Slim on Brighton Beach, you may want a fait bit. Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 24, 2006 Share Posted September 24, 2006 Is the ratio naff? if it takes no account of box efficiency? Rob, variation in box efficiency (and a few other factors) would tend to make such ratios somewhat meaningless.... Link to comment Share on other sites More sharing options...
rob.d Posted September 24, 2006 Author Share Posted September 24, 2006 Is the ratio naff? if it takes no account of box efficiency? Rob, variation in box efficiency (and a few other factors) would tend to make such ratios somewhat meaningless.... Cheers Simon :) Sounds good to me. I'll experiment one day, and let you know how I went on ;) Rob Link to comment Share on other sites More sharing options...
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