Legitimate question.
Would you find it better to power a pair of subwoofers that have a high power requirement from twin amplifiers to match the required power from the subwoofers rather than get a single, larger amplifier? If you had them set to the exact same specification, would it sound just as good?
Ok, now... if two subwoofers rated at 600wrms each total out to about 1200wrms and the single amplifier was 1000wrms max, it would be underpowered right? well i think it wouldnt be too 'bothered' right?
anyways, instead of getting an even larger single super-amp, get maybe two same exact model amps of say about 600rms or 625wrms or something amps? and set the crossovers, gains, etc etc to the same exact levels? I think it comes out cheaper...
What do you guys think?
Notladstyle
12-24-2006, 11:56 AM
dual amps - less efficient but much cleaner output.
TJElite
12-24-2006, 12:02 PM
OK...you guys are in trouble. As soon as I finish this post, I have to help wrap Christmas gifts...which I hate doing. So, here comes the thesis...
watt for watt, from the same manufacturer line, for the same impedance, one big amp will almost always (if not always) be cheaper.
Also, one amp is almost always easier to set up...one power, one ground, one set of RCA's, etc. You'd also be hard pressed to set two amps 'exactly' the same as to xover and gain, but that's probably not a huge problem...but not a problem at all, with one amp.
There might be some advantages to going to two amps, like more heatsink. A 1000 watt amp is usually not twice as big as 2 500 watt amps, so you will probably get more heatsink with two smaller amps. There also might be some design advantages...like two of the 500 watt power supplies might be more robust than one of the 1000 watt supplies, due to available component size, etc. In any event, I would think that these advantages are minor, and won't make up for the cost and installation difference.
Now, I do think that there might be some advantage to running amps into higher ohm loads, but that's not what you are asking. I have no data, but I would think that running two 1 ohm stable amps, each into 2 ohms would be better than running just one of them into 1 ohm. Dampening factor, for example, goes down with impedance. I would also expect more headroom from the power supply. Again, I don't know if any of these would justify the cost of two amps vs. one.
As for matching amp power to RMS ratings of speakers...that's a whole different argument. It is worth noting that the RMS rating of a speaker is almost always a thermal rating...ie, the amount of power the voicecoil can dissipate without burning up. Its also worth noting that I think RMS ratings have become more about marketing than science. Its amazing how one companies 2 inch vc can handle twice as much power as anothers, regardless of their latest 'turbo vortex super computer designed cooling vents'.
What's more important is the excursion limited power handling. This depends on factors like the motor strength, xmax, and box design, and will vary with frequency. For example, if a speaker in a given enclosure is driven to xmax at 40 hz with 40 watts of power, you really won't get any more output by putting more power to it. Output of a speaker is dictated by displacement, which is cone area x excursion...that's all there is. There are some advantages to more power, like quicker response, and at higher frequencies, you'll need this to hit xmax (same distance, less time to get there...the excursion limited output curve is not linear, and will exceed RMS as frequency goes higher), but there is still a limit, and diminishing returns. This is one of the reasons people don't see the expected gains in SPL when they go to bigger amps. This is also part of where the 'bigger boxes are louder but smaller boxes handle more power' logic comes from. Bigger boxes, less pressure for the cone to over come, less power to reach xmax. Smaller boxes, more pressure, more power to reach xmax. In short, bigger boxes are more efficient.
Now, in my opinion, there is a real advantage to using bigger amps. I can get to the excursion limited power number with a lower gain setting. This means everything from less noise and less heat to more importantly, less distortion. When an amp 'distorts' due to over running the gain, the normal sine wave becomes square. The area under a square wave is greater than the area under a sinusoidal wave, so more heat is generated in the voice coil, leading to burned up stuff, with minimal if any increase in output. Now, sending a square wave to a speaker on purpose, vs. generating one through over driving an amp, can boost spl, but that's another topic.
Another point is the concept of "RMS". It actually means root mean squared, but that's not as important as thinking of it as an average. Unless you play nothing but sine or square waves, the output to your subs will be varied. This variation over time determines actual heat generated by a voice coil. This is why you can use amps with much higher output than the rms rating of the subs, and not just kill them. A 1000 watt amp still puts out 0 watts with no input. Depending on the amp, however, it might put out much more than 1000 watts, for a short time, when driven to its max. This is why many amps have a dynamic power rating that is much higher than its rms output...some just use it as a marketing ploy.
So, in short, for general use, I'd probably start by picking some subs that, in the enclosure I want, have highest combination of efficiency (NO or 1/2 space efficiency, not that hokey db@ 1w/1m crap) and excursion limited power handling over the frequency I intend to use them. Then I'd chose an amp that will deliver about 20-50% more RMS power than the subs are rated for, and keep my gains down. If I already owned the subs, I'd just determine the excursion limited power handling, and pick a similar amp.
If I were building a DB only car, I'd probaby go with an amp rated for 5 to 15 times the rms of my subs, since I'd most likely use them at a frequency that gave me an excursion limited rating several times that of the rms rating. They would only be 'on' for brief periods, and short life spans would be expected.
Time to go wrap presents...
Toby
k4rts
12-24-2006, 12:42 PM
one big amp. draws less current.
Notladstyle
12-24-2006, 12:43 PM
cliffnotes: its more work but technically the only gain is more heatsink hence less thermal distortion hence cleaner sound.
Wow Toby, :nworthy:you da man, i appreciate the lecture:nerd::D
Anyways yeh i thinking of a VR2000d, you have in stock?
damage price?
cliffnotes: its more work but technically the only gain is more heatsink hence less thermal distortion hence cleaner sound.
fuck cliffnotes, i liked reading that, very informative
stompy
12-24-2006, 06:06 PM
nice, i think he was saying use a bigger amp than subs require to keep noise down.