Thunderlight Posted September 3, 2014 Share Posted September 3, 2014 I have a couple of 800w 1600w peak bass bins that are 8ohm! What amp's would people suggest?? It's been fun trying to find 800w 8ohm 2 channel amp's!! Thought's??? Tom Link to comment Share on other sites More sharing options...
DrV Posted September 4, 2014 Share Posted September 4, 2014 They don't have to say 800W 8ohms in the spec - if you looked for amps rated at 1600W into 4 ohms these would deliver 800W into 8 ohms and run nice and coolDave Link to comment Share on other sites More sharing options...
Chappie Posted September 4, 2014 Share Posted September 4, 2014 QSC PL340, Full Fat Audio FFA-6000/ 8000, MC2 E45 etc, there are plenty out there. You're probably going to want something bigger than 800W though, especially as they are subs. Link to comment Share on other sites More sharing options...
Thunderlight Posted September 4, 2014 Author Share Posted September 4, 2014 Thanks for the replies! Yer I gathered that you could probably size the amp in 4ohm by doubling the watts but wasn't entirely sure!!You say you would go bigger than the program power of 800w and just set up the limiter to stop any risk of blows?? Tom Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 4, 2014 Share Posted September 4, 2014 Yer I gathered that you could probably size the amp in 4ohm by doubling the watts but wasn't entirely sure!! In theory you can, but not many amps actually follow that maths... Also, be sure to note what the manufacturer is actually measuring / stating.For example. the Yamaha P7000s (quite a nice amp) is rated at 1100W into 4 ohms and 750W into 8 ohms but only at 1kHz. The 20-20,000Hz power output is 950W into 4 ohms and 650W into 8 ohms, plus it's supply voltage sensitive. Link to comment Share on other sites More sharing options...
Thunderlight Posted September 4, 2014 Author Share Posted September 4, 2014 Yer well that goes without saying the faster the transistors are switching for higher frequencies the more current will flow! As for voltage that's Ohm's law of course, V over I and R!! Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 5, 2014 Share Posted September 5, 2014 Yer well that goes without saying the faster the transistors are switching for higher frequencies the more current will flow! As for voltage that's Ohm's law of course, V over I and R!! I wouldn't want to be contentious, but I don't think either statement is quite true! Link to comment Share on other sites More sharing options...
alistermorton Posted September 5, 2014 Share Posted September 5, 2014 The first is perhaps more directly relevant to the power consumption of the likes of CPUs where the power consumption increases with the clock frequency, but they are operating at radio frequencies. The second, well that's just a bit confused http://www.blue-room.org.uk/public/style_emoticons/default/blink.gif Link to comment Share on other sites More sharing options...
warrenstuart Posted September 6, 2014 Share Posted September 6, 2014 If you're only going to run bass bins with it why not use a smaller amp running in mono bridged mode to get the power you need? Just as an example EV CP2200 350w p/c into 8 ohms but 1800w into 4 ohms bridged with both bins in parallel. Just an idea :-) Warren. Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 6, 2014 Share Posted September 6, 2014 Bridging can be be a useful way of getting the 'extra' wanted power, but do bear in mind the manufacturers quote the power output at 1%THD (rather than 0.1%) and the amp may be a little more stressed. Many users prefer to have 3dB headroom so 3200W @ 4Ohms might be preferable. In the example given, the EV CP3000S would be good... Link to comment Share on other sites More sharing options...
Thunderlight Posted September 6, 2014 Author Share Posted September 6, 2014 My statement V over I and R was referring to the input power fluctuating to the amp. Because the resistance of a speaker will be constant say 4Ohm the only factor changing the current flow to the speaker is voltage! This of course doesn't apply to amps with switched power supplies, but if the input voltage to the amp fluctuates in peak to peak value the output from the rectifiers will fluctuate! Admittedly having thought this through that is what the large caps are for after the rectifier!! But if the input voltage is constantly down say 30v then output from the caps will be slightly lower than normal. Meaning the voltage to the power transistors will be slightly less so the voltage to the speaker will be marginally less! Thus Ohms law does apply!! I know that this is not exactly true as the power transistors are never constantly on, as this is what blows speakers! However the basics are there! Like I said it does apply to switched power supplied amps as that is what the switched power supply is for! Hopefully I'm not completely wrong here, however I'm open to learn!! And yes have thought of bridged mono but that is not ideal for some of the event's the PA will be doing. The need for stereo bass bins is important to me as some of the lower frequencies are panned side to side to create a experience for the audience!! Floyd music you see very deeep!!! Tom Link to comment Share on other sites More sharing options...
Thunderlight Posted September 7, 2014 Author Share Posted September 7, 2014 Like I said it does apply to switched power supplied amps as that is what the switched power supply is for! Sorry miss typed I meant doesn't!!http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif Link to comment Share on other sites More sharing options...
audiomik Posted September 7, 2014 Share Posted September 7, 2014 TomRe: "Because the resistance of a speaker will be constant say 4Ohm the only factor changing the current flow to the speaker is voltage!" Think that you should read up on both Impedance and Power Factor and how these change with frequency when driving 'Speakers with an Amplifier.Far too long an explanation of this to put here though. Re: "This of course doesn't apply to amps with switched power supplies" I would trust that virtually all Amplifiers have a switch for their Power Supplies!However, should you be referring to Switch Mode Power Supplies, then they will draw a proportionate Current at the supply Voltage dependant upon the Power being delivered and dissipated by the Amplifier. hope this assists, apology for the short answers..........Mik Link to comment Share on other sites More sharing options...
Thunderlight Posted September 7, 2014 Author Share Posted September 7, 2014 Cheers Mik yes will have a read up!! Yes I was indeed referring to switched mode power supplies not the switch on the front of the amp!!http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif Tom Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 8, 2014 Share Posted September 8, 2014 Tom, As you've noted, the power supply design plays a significant part here. In addition to switched mode PSUs, it is possible (although unusual) to design a regulated linear power supply which would be more tolerant of supply voltage fluctuations. Although we cannot violate the law of conservation of energy (inasmuch we can't get more power out of an amp than we put in) it is possible through good PSU design to draw short term current peaks which are over and above the long term average power output of the PSU. Of course, if the manufacturer tries to sell an amp as more powerful (but not on a continuous basis) then many users will cry foul. The Yamaha amp I mentioned has specs which are quite honest - you can see what happens as a variation of supply voltage. With regards to loudspeakers, sadly their "resistance" is far from constant. The speaker driver itself exhibits resistance, capacitance and inductance, and the load presented to the amplifier is further modified by the loudspeaker's mechanical and acoustic parameters plus the contribution of the loudspeaker cable (wrt damping factor etc.). An 8 Ohm cone driver impedance can vary from 2 Ohms to 40 Ohms with respect to frequency. It is entirely possible for a pair of 8 Ohm bass bins wired in parallel to present a load of less than 2 Ohms to the amplifier at a given frequency. So, unfortunately, the loudspeaker does not behave like a simple resistor! With regards to stereo subs, well done for breaking out of the "bass is omnidirectional" mindset! We have some interesting research going on concerning this - low frequency sound can be localised! Hope you find the amp that meets your needs... Simon Link to comment Share on other sites More sharing options...
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