monsterer Posted August 20, 2007 Share Posted August 20, 2007 Hi guys, This is my first post on this forum - I'm totally new to PA speakers and my electronics skills aren't brilliant... However, I recently bought a pair of omnitronic dx-2222 speakers which are three way (piezo tweeter, horn and 2 woofers) and while I was fixing a problem with the contacts on the connectors (which had come lose and didn't work out of the box) I noticed that the crossover circuit is only two way, with both horn and tweeter being driven from the same source. The odd thing is that the crossover circuit-board itself does have mid-range tracks on the board but the components aren't soldered on there. In the picture you can see the M marking in the middle, but there isn't anything connected to it. The question is, how difficult would it be to turn this into a proper 3 way crossover? The midrange is understandibly 'lacking' compared to a reference set of speakers I've got. The speaker unit is rated at 500W RMS, at 8ohms. I have an actual wiring diagram of the circuit if anyone needs it? Cheers, Paul. http://www.pfirth.co.uk/catspeaker_002.jpg Okey, I've scanned the circuit diagram: http://www.pfirth.co.uk/crossover.jpg Link to comment Share on other sites More sharing options...
tokm Posted August 20, 2007 Share Posted August 20, 2007 While I can't help you on turning your boxes into true 3way, I believe I can offer an explanation as to why the 'mid' horn and HF tweeters are fed from he same part of the crossover, this be because they're both Piezos.. Thats also why the mids lacking, seeing as theirs no dedicated driver for it, those frequencies are just made from a mush of the ones made by the LF & HF drivers.. But you already knew that Turning them into proper 3way boxes sounds like a good idea, the large horn should be able to handle a fair bit of the mid range stuff sent to it and you'll finally be able to get something half decent out the cabs :) Tom Link to comment Share on other sites More sharing options...
monsterer Posted August 20, 2007 Author Share Posted August 20, 2007 While I can't help you on turning your boxes into true 3way, I believe I can offer an explanation as to why the 'mid' horn and HF tweeters are fed from he same part of the crossover, this be because they're both Piezos..Tom Ahhh, I see - if the horn is piezo, do I have to handle it differently than if it wasn't? Can I still use the horn with a better crossover design? Cheers, Paul. Link to comment Share on other sites More sharing options...
Rob_Beech Posted August 20, 2007 Share Posted August 20, 2007 Piezo's don't necessarily need a crossover, a resistor in series helps though. I'd say that the horn (if it is a piezo which I'd say it was looking at the crossover) it'll not be too different from the other HF drivers in the box. I'd expect the 12's to go up high enough to cover alot of the MF to be honest. You could put a different HF driver in but would need a suitable crossover. Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 Piezo's don't necessarily need a crossover, a resistor in series helps though. I'd say that the horn (if it is a piezo which I'd say it was looking at the crossover) it'll not be too different from the other HF drivers in the box. I'd expect the 12's to go up high enough to cover alot of the MF to be honest. You could put a different HF driver in but would need a suitable crossover. You'll have to fogive my ignorance - HF = high frequency? I presume there is a highpass filter in line before the tweeter and horn in my crossover circuit - is that what the 4.7 micro Farad (capacitor?) denotes? Does anyone have any idea what I'd need to add to this circuit to get a decent midrange out of the horn? :) Link to comment Share on other sites More sharing options...
Simon Lewis Posted August 21, 2007 Share Posted August 21, 2007 Does anyone have any idea what I'd need to add to this circuit to get a decent midrange out of the horn? :) If the horn is a piezo device, then it's unlikely that you'd get midrange of any description out of it. Piezo loudspeakers are essentially a capacitive load, in other words they act as their own crossovers, and do not produce much in the way of usable sound below about 4kHz. The only way to really upgrade the system is to buy a midrange horn and flare that fits your box, buy a new three way crossover and fit it all in. By then, I suspect that it would be more cost effective to sell the existing cabs and upgrade to a new or second hand good quality three way box, or probably a two way system that has a real compression driver (as opposed to the piezo) midrange / high frequency system. Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 Does anyone have any idea what I'd need to add to this circuit to get a decent midrange out of the horn? :) If the horn is a piezo device, then it's unlikely that you'd get midrange of any description out of it. Piezo loudspeakers are essentially a capacitive load, in other words they act as their own crossovers, and do not produce much in the way of usable sound below about 4kHz. The only way to really upgrade the system is to buy a midrange horn and flare that fits your box, buy a new three way crossover and fit it all in. By then, I suspect that it would be more cost effective to sell the existing cabs and upgrade to a new or second hand good quality three way box, or probably a two way system that has a real compression driver (as opposed to the piezo) midrange / high frequency system. Doh! :) How can I tell if my horn is piezo? Also, anyone know what that capacitor in the circuit diagram is for? Link to comment Share on other sites More sharing options...
Shez Posted August 21, 2007 Share Posted August 21, 2007 Also, anyone know what that capacitor in the circuit diagram is for? Capacitors block DC (and low frequencies when used in an appropriate circuit) i.e. they are a high pass filter.Inductors (the coil feeding the LF driver) do the opposite i.e. they are a low pass filter. Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 Also, anyone know what that capacitor in the circuit diagram is for? Capacitors block DC (and low frequencies when used in an appropriate circuit) i.e. they are a high pass filter.Inductors (the coil feeding the LF driver) do the opposite i.e. they are a low pass filter. I suspected as much :) - so there is infact already a high pass filter on my circuit before the horn? That can't be helping with midrange... Link to comment Share on other sites More sharing options...
Chris Beesley Posted August 21, 2007 Share Posted August 21, 2007 :) If the horn is a piezo device, then it's unlikely that you'd get midrange of any description out of it. Piezo loudspeakers are essentially a capacitive load, in other words they act as their own crossovers, and do not produce much in the way of usable sound below about 4kHz. :) Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 :) If the horn is a piezo device, then it's unlikely that you'd get midrange of any description out of it. Piezo loudspeakers are essentially a capacitive load, in other words they act as their own crossovers, and do not produce much in the way of usable sound below about 4kHz. :) That being the case, why is there a separate high pass filter on the circuit? Link to comment Share on other sites More sharing options...
Chris Beesley Posted August 21, 2007 Share Posted August 21, 2007 The high pass filter will be in place to block the majority of the LF from the HF circuit. Guys - for reference here is the Omnitronic site... Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 The high pass filter will be in place to block the majority of the LF from the HF circuit. Guys - for reference here is the Omnitronic site... My point is that if you've filtered out all the low frequencies, you're not giving the horn much of a chance of reproducing mid-range, piezo or not, surely? My horn is almost certainly piezo, I found a link to a very similar looking separate via the omnitronic site: http://www.omnitronic.com/omn_artdetail.ph...0050&lang=E It says frequency range 5kHz-18kHz... Another thing, :) am I right in thinking that 100/10W resistor is for dropping the wattage by 10th to feed the tweeter/horn? Link to comment Share on other sites More sharing options...
SteveAATW Posted August 21, 2007 Share Posted August 21, 2007 You need to protect the drivers from the LF energy as well though, even if a driver can't transduce a frequency if the signal is going through it will try, thus sending a full range signal through HF drivers will just result in blowing them, hence the crossover - that filter on the HF side of that circuit is (if memory serves me) a first order high pass and has a break frequency (-3dB point) of 338.63Hz. The problem is that HF drivers were never designed to go that low and LF drivers were never designed to go that high, this is why traditionally, 2 way systems sound pants - there's a massive gap in the middle of there response and the components that are there are stretched beyond the point at which they sound any good, the circuit allows some of the mid-range to goto your HF driver but ultimately its pointless as your HF can't transduce it properly - HF drivers should never be taken much below 5KHz. The wattage of the resistor is to take the amount of heat its going to generate in filtering the LF part of the signal out - the energy has got to go somewhere and in this case it goes out as heat, the resistor has to be rated to handle this. edit - just noticed that these are billed as '3 Way Speakers', although they do have a horn and then a tweeter, they're not really what I'd call 3 way at all!! Link to comment Share on other sites More sharing options...
monsterer Posted August 21, 2007 Author Share Posted August 21, 2007 You need to protect the drivers from the LF energy as well though, even if a driver can't transduce a frequency if the signal is going through it will try, thus sending a full range signal through HF drivers will just result in blowing them, hence the crossover - that filter on the HF side of that circuit is (if memory serves me) a first order high pass and has a break frequency (-3dB point) of 338.63Hz. Is that the frequency at which the signal is split? How do you work out that value? The wattage of the resistor is to take the amount of heat its going to generate in filtering the LF part of the signal out - the energy has got to go somewhere and in this case it goes out as heat, the resistor has to be rated to handle this. And I imagine the tweeter and horn aren't rated at the same wattage as the two woofers - does it serve the job of compensating for that as well? edit - just noticed that these are billed as '3 Way Speakers', although they do have a horn and then a tweeter, they're not really what I'd call 3 way at all!! Well, quite. Do you think its worth me trying to make a better crossover to feed the horn separately? Link to comment Share on other sites More sharing options...
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