Would you recommend this amp with these speakers and sub? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 2 Old 04-30-2020, 03:26 PM - Thread Starter
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Would you recommend this amp with these speakers and sub?

Hi guys, I have a pontoon that I'm going to be upgrading the sound system soon and I have a couple of questions. I want to buy a Kenwood KAC-M8005 5 channel amp that has 50 watts RMS x 4 + 300W @4 ohms, 75 watts RMS x 4 + 500 watts RMS x 1 @ 2 ohms, 150 watts RMS x 2 bridged at 4 ohms + 500 watts RMS x 1 at 2 ohms. The 4 speakers I want (Kicker 45KM654L) say on Kicker's website that they work best with 65 watts of recommended power. The sub I want (Kicker (46CWTB104) recommends 400 watts. The amp is $100 off right for $268. Would this amp be too underpowered for these speakers and sub and would I regret the purchase? The speakers and sub I picked are both 4 ohm but I can always choose the 2 ohm version of the sub but I don't think that would be the right choice because I'm assuming the 4 ohm version will drain my battery slower. I really don't feel like having to spend the money on 2 separate amps if I don't have to. I should probably mention I have a head unit (Jensen MS30BT) that has a max output of 160 watts, 4x40 watts. Not sure if this matters. Any help or suggestions would greatly be appreciated.
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post #2 of 2 Old 05-15-2020, 09:57 AM
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Originally Posted by armysgt1 View Post
I'm assuming the 4 ohm version will drain my battery slower.
That is an interesting statement. Offhand, I was going to post that the impedance of the subwoofer won't affect battery drain. BUT! Losses in amplifiers are proportional to current, which is inversely related to impedance, so what you say is actually correct, though not by a huge amount.

I worked in this area for many many years, and due to those losses I do NOT believe in loading down amps to their lowest impedance. Even if the amp is rated at 1 ohm, for example, I'd run at 2 ohms, to get just as much real-world power with less heat and less current drawn from the battery. This is my firm belief based on measuring a lot of amps, testing with the PowerCube, and intimate familiarity with the real impedance of speakers (which are NOT like the resistors amps are tested with).
--> Yeah do the 4 ohm sub

Speaker power ratings are meaningless (see below). That amp will play those speakers and sub pretty loud. Loud enough for you? That I can't say. I can say to play a lot louder I'd be getting into like 8" woofers with horns and massive subs, and yes separate and significantly bigger amps-probably not what you have in mind for your pontoon.

Here are "Head_Unit’s Rules Of Protection" to digest:
1) If when things start to sound distorted or odd you TURN IT DOWN, you are unlikely to ever break anything.
2) If you constantly "turn it up to 11" you will break something.
3) The amp and speaker power ratings do not matter. Don’t bother “matching” the amp and speaker power. That is a seemingly sensible yet actually meaningless exercise, because:
- Speaker specifications are 92% useless (and I say that as a loudspeaker engineer).
- Specs for amps are not thorough since they are measured into resistors for pragmatic reasons and speakers are not resistors at all.
- You are less likely to damage speakers with a big amp, since let’s face it everyone cranks it up sometime, and a small cheap amp is then more likely to clip and possibly put out DC and ultrasonics
- Car amps' 2 ohm or even 1 ohm rating is the most meaningful even if your speakers are 4 ohms. Should be 20-20k Hz, distortion under 1% or it's baloney.
- For amps "more" power means (IF specs are comparable) at least three times as much due to the logarithmic nature of hearing.
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