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View Full Version : Question regarding RMS, gain, efficiency and volume.



Buffalohed
02-06-2007, 09:55 PM
I'm not currently in the market for new component speakers but I will be in the coming months, and while this question occured to me and I think I am close to a deeper understanding, I figured I would go ahead and ask it.

To give some background, I am running Kicker SS65.2 components off a Kicker SX900.4 amp. The comps are rated at 100rms, the amp at 125rms, both at 4ohms.

Ok I'll try to get to the point. This is my first set of components in car audio. I see lots of people on the board talking about powering, for example, Rainbow Germaniums (rated at 120?? rms) with well over 200 for great performance. Now I don't have a very good understanding of how amplifiers work but I do know this. When I turn up my comps to 35/35, with the gain set about 70% of the way up, they sound like they are at their limit. Not really distortion, but you can tell they are straining.

What happens when you send 200, or 300rms? Will it give the comps the ability to get louder at lower H-U volume settings? (I realize that it depends on the comps you have, and let's just pretend we are talking about Germaniums because people talk about giving them a lot of power.) Or will it increase their frequency response at the given volume, or ???

I'm just curious because I feel like I could be getting more out of my components and I wonder if a larger amount of clean watts will actually enable them to get louder and cleaner with less effort (is this what the term "headroom" actually refers to?). But basically I know very little about this so any insight would be appreciated.

I guess another important question would be how to test this. Bridging my SX900.4 gives it over 400 watts per side and I am very reluctant to try this, even with gain on 0. What kind of hints or specs would indicate that certain components would perform well with extra wattage?

ls20
02-07-2007, 12:20 AM
HU sends out a voltage signal (waves), the amplitude of which is determined by volume control
amplifier boosts/amplifies/multiples that signal, the scale of which determined by gain control

because you never want to amplify a clipped/distorted signal, you'd want to set the gains so that the "ceiling" of the system is before the source clips... hence the rule of thumb of setting amp w/ 70% hu volume

when you hear what sounds like straining, it could be the speakers reaching their limits, AND/OR theyre within their limits but playing a disorted signal.. from the amplifier AND/OR from the HU. your HU at 35/35 is contributing to what sounds like strained speaker output

IF the amp is the bottleneck in the system -- and thus sending distorted signals -- then a diff amp setup feeding more power (technically, more current) is the solution. this may or may not be the case, because the rated specs isnt 100% accurate.

frequency graph is the amplitude as function of frequency. so louder = increase across entire graph.. or overall "response"



keep your HU at fixed level - 70% is good. start increasing the gain until you hear distortion.
change to bridged setup. start increasing gain until you hear distortion. if it distorts at a higher audible level/Loudness, not giving it enough "power" was bottleneck. if it distorts at same loudness, then youve reached limits of the speakers

helotaxi
02-07-2007, 07:22 AM
In all honesty, RMS speaker ratings are not all that important. You are not going to ever run that kind of power continuously to a set of mid/high speakers. You would be feeling pain well before you got above 30WRMS. Where the high power amps come into play is allowing you to effortlessly send dynamic power to the speakers without clipping the amp. This allows for increased dynamic range and "opens up" the sound of the system. This of course assumes that you have a dynamic source to begin with like a well recorded and produced CD. Sadly most music today is not well produced with respect to dynamic range so depending on what you listen to, you may not see the full benefit of adding the extra power.

Buffalohed
02-07-2007, 08:34 AM
I guess I will have to fiddle with my settings then and see what is going on.

For a while I had my gain at max, because I set it per the instructions and there was no distortion from the speakers. But the speakers start to strain between 31-33 depending on the recording, so I turned the gain down to roughly 70% hoping to get more volume. It didn't work, as now the speakers only barely strain at 34-35. So I will try bridging it and working with the gain from there, but I strongly suspect that my components are at their limit and I will have to live with them until I get something that can accomodate my volume preferences.

Thanks for the help folks.

ls20
02-07-2007, 04:16 PM
if your HU is up, and your amp gain is up, and you hear no distortion, yet its not loud enough, maybe the speakers have low efficiency (though their listed specs say otherwise)

DejaWiz
02-07-2007, 04:59 PM
Is your amp capable of gain matching the voltage level of the hu's pre-outs?

Buffalohed
02-07-2007, 05:15 PM
Is your amp capable of gain matching the voltage level of the hu's pre-outs?

Yes, pre-outs are 4 volts, and the amp has digitably selectable input voltage. And yes it is set to 4.

DejaWiz
02-07-2007, 05:44 PM
Yes, pre-outs are 4 volts, and the amp has digitably selectable input voltage. And yes it is set to 4.

Alpine V series?

Buffalohed
02-07-2007, 10:15 PM
Alpine V series?
Head unit is a Kenwood Excelon 590, Amp is Kicker SX900.4.

DejaWiz
02-07-2007, 11:16 PM
Head unit is a Kenwood Excelon 590, Amp is Kicker SX900.4.

props to me for paying attention in the first post where all this was stated... :rolleyes: