So, I’m a bit confused about the ratings on my amps. I have a four channel infinity 7541a that, according to the manual, is either 111w x 4 or 278w x 2 (@4ohms). I also have an infinity 7521a that is either 97w x 2 or 283 w x 1.
I need to power the front, rear, and sub. The front is a pair of jbl p650c comps rated at 90w, the rear are a pair of infinity 6000c comps at 90w also, the sub is an infinity kp10.1 rated at 350w.
First, will driving the components with 111w damage them, what about 97w? And, I’ve been bridging the 7521a for the sub, but it just doesn’t make sense that bridging two 97w channels will result in more wattage than bridging two 111w channels. Can this be right? How do I measure the actual output?
Thanks.
Replies (5)
swez on 01/29/2006 18:37:50
The 7541a is the right amp for your front and rear speakers. It has a bit more power than the speakers are rated for (continously), but this is good as you have a margin of amp reserves to keep the audio signal clean at all times. It should not blow your speakers if you use proper gain settings and avoid excess EQ boost.
The 7521a is good enough for a 4 ohm sub load, when the amp is bridged to MONO mode operation. It's a tad light on power fo that sub, but not so far underpowered to cause you to run the amp in severe clipping mode, with the gains set correctly on both amps.
Here, you may need to tone down the Mid/Highs a tad, to allow the sub to keep up with everything else. Do you know how to do gain matching beteen both amps and HU?
Swez
PS Both amps are rated at noted power with a 14.4 volt supply voltage. Most cars cannot sustain that voltage level after a vehicle start and the BAT has been topped off by the ALT. That means your 4 channel will deliver about 95 Wrms x 4 @ 4 ohms. The sub amp will deliver about 250 Wrms wne bridged, but here the voltage supplly is normalized to about 13.5 -13.8 volts. This is well within acceptable ranges.
pigwiggle on 01/29/2006 19:19:52
Well, I'm not quite sure what you mean by gain matching, but this is how I go about setting the gain on the amps. I get something with good range and lots of bass (usually Daft Punk), set the HU at 3/4 volume, and flat eq. Turn the bass boost to 0db and tune the entire high end out of the sub with the xover (~120Hz). Then I just turn up the gain until the clip indicator light starts to flicker and back it off a bit. I go back and forth between the eq, gain, and bass boost until it sounds nice without clipping. I can't seem to get as much bass as I would like but I guess that's the amp.
swez on 01/29/2006 19:35:20
Good, right on track and just what I would expect from your system... bass is a tad weak and Mid/highs are too strong.
Here, we have to go to the weakest chain in the link and use that as our reference point. Get the sub amp to max output w/o clipping and then bring down the power to the mid/highs to blend all of this gear together.
It might be as simple as changing the amp gain settings on your 4 channel to attenuate the 4 ch amps' output. The Min/Max Input pots are your tweaking tools here. Hopefully, you can make minor adjustments on these pots to bring down the overall levels of all Mid/Highs in your system to match the Bass Engine.
The other option would be to get a stronger amp for your Perfect.1 sub or go to a ported box and pick up about +3 dB more bass at the Port Tuning Frequency. (PTF) However, now you will need a Sub Sonic Filter (SSF) to block all lows, below PTF. The sub amp does not have an SSF crossover on it.
Swez
pigwiggle on 01/30/2006 20:13:12
Thanks Swez. But let’s say I don’t believe my amp is capable of putting out a given wattage. How do I test it? I’m stuck with the box I have. Sacrificing cargo room was too much to ask of the wife so I fiberglassed in the rim of the spare tire (exactly 0.6 cu ft). Get to keep the spare and all the cargo room. That’s why I got the small sub. You know, I’ve got to wonder why infinity makes a 350W sub but doesn’t make a corresponding amp.
swez on 01/30/2006 20:40:16
Hummm, you will need a "dummy load" resistor of 4 ohms and can handle about 300-400 watts, to get an accurate reading of amp channel output. Ohmite Manufacturing makes some pretty heavy duty ones used in elevator motor citcuits etc.
You can try reading the AC voltage off the amp terminals with the sub connected and some 5 second test tones. The numbers will be a little off, due to changes in voice coil impedances. Once you have voltage numbers, use Ohm's Law to calculate the wattage.
V x V/R = Voltage sq'd/resistance (assume the resistance to be 4 ohms for that sub.
I would anticipate a voltage reading near 37.4 VAC for a true 350 Wrms amp into a 4 ohm load. At certain frequencies, that number will be a bit high or low, based on impedance changes in the voice coil.
Hope that helps,
Swez
PS The coil rating number (350 W continous) is more or less the thermal limits of an average sampling of subs, right off the production line. Am sure there is a Bell Curve used to determine that average and at least +/-3 sigma as the standard. Anything that falls in that range, would be considered good.
However, we do know that some units get out to market, that are well above or below rated limits. I doubt that most sub makers would bother to do 100% testing levels. A $400.00 sub might have 100% testing and verification... but not mass production units like the IKP's... I dunno
I need to power the front, rear, and sub. The front is a pair of jbl p650c comps rated at 90w, the rear are a pair of infinity 6000c comps at 90w also, the sub is an infinity kp10.1 rated at 350w.
First, will driving the components with 111w damage them, what about 97w? And, I’ve been bridging the 7521a for the sub, but it just doesn’t make sense that bridging two 97w channels will result in more wattage than bridging two 111w channels. Can this be right? How do I measure the actual output?
Thanks.
Replies (5)
swez on 01/29/2006 18:37:50
The 7541a is the right amp for your front and rear speakers. It has a bit more power than the speakers are rated for (continously), but this is good as you have a margin of amp reserves to keep the audio signal clean at all times. It should not blow your speakers if you use proper gain settings and avoid excess EQ boost.
The 7521a is good enough for a 4 ohm sub load, when the amp is bridged to MONO mode operation. It's a tad light on power fo that sub, but not so far underpowered to cause you to run the amp in severe clipping mode, with the gains set correctly on both amps.
Here, you may need to tone down the Mid/Highs a tad, to allow the sub to keep up with everything else. Do you know how to do gain matching beteen both amps and HU?
Swez
PS Both amps are rated at noted power with a 14.4 volt supply voltage. Most cars cannot sustain that voltage level after a vehicle start and the BAT has been topped off by the ALT. That means your 4 channel will deliver about 95 Wrms x 4 @ 4 ohms. The sub amp will deliver about 250 Wrms wne bridged, but here the voltage supplly is normalized to about 13.5 -13.8 volts. This is well within acceptable ranges.
pigwiggle on 01/29/2006 19:19:52
Well, I'm not quite sure what you mean by gain matching, but this is how I go about setting the gain on the amps. I get something with good range and lots of bass (usually Daft Punk), set the HU at 3/4 volume, and flat eq. Turn the bass boost to 0db and tune the entire high end out of the sub with the xover (~120Hz). Then I just turn up the gain until the clip indicator light starts to flicker and back it off a bit. I go back and forth between the eq, gain, and bass boost until it sounds nice without clipping. I can't seem to get as much bass as I would like but I guess that's the amp.
swez on 01/29/2006 19:35:20
Good, right on track and just what I would expect from your system... bass is a tad weak and Mid/highs are too strong.
Here, we have to go to the weakest chain in the link and use that as our reference point. Get the sub amp to max output w/o clipping and then bring down the power to the mid/highs to blend all of this gear together.
It might be as simple as changing the amp gain settings on your 4 channel to attenuate the 4 ch amps' output. The Min/Max Input pots are your tweaking tools here. Hopefully, you can make minor adjustments on these pots to bring down the overall levels of all Mid/Highs in your system to match the Bass Engine.
The other option would be to get a stronger amp for your Perfect.1 sub or go to a ported box and pick up about +3 dB more bass at the Port Tuning Frequency. (PTF) However, now you will need a Sub Sonic Filter (SSF) to block all lows, below PTF. The sub amp does not have an SSF crossover on it.
Swez
pigwiggle on 01/30/2006 20:13:12
Thanks Swez. But let’s say I don’t believe my amp is capable of putting out a given wattage. How do I test it? I’m stuck with the box I have. Sacrificing cargo room was too much to ask of the wife so I fiberglassed in the rim of the spare tire (exactly 0.6 cu ft). Get to keep the spare and all the cargo room. That’s why I got the small sub. You know, I’ve got to wonder why infinity makes a 350W sub but doesn’t make a corresponding amp.
swez on 01/30/2006 20:40:16
Hummm, you will need a "dummy load" resistor of 4 ohms and can handle about 300-400 watts, to get an accurate reading of amp channel output. Ohmite Manufacturing makes some pretty heavy duty ones used in elevator motor citcuits etc.
You can try reading the AC voltage off the amp terminals with the sub connected and some 5 second test tones. The numbers will be a little off, due to changes in voice coil impedances. Once you have voltage numbers, use Ohm's Law to calculate the wattage.
V x V/R = Voltage sq'd/resistance (assume the resistance to be 4 ohms for that sub.
I would anticipate a voltage reading near 37.4 VAC for a true 350 Wrms amp into a 4 ohm load. At certain frequencies, that number will be a bit high or low, based on impedance changes in the voice coil.
Hope that helps,
Swez
PS The coil rating number (350 W continous) is more or less the thermal limits of an average sampling of subs, right off the production line. Am sure there is a Bell Curve used to determine that average and at least +/-3 sigma as the standard. Anything that falls in that range, would be considered good.
However, we do know that some units get out to market, that are well above or below rated limits. I doubt that most sub makers would bother to do 100% testing levels. A $400.00 sub might have 100% testing and verification... but not mass production units like the IKP's... I dunno
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