Balancing power

 

New member
Username: Ohiopilot

Post Number: 1
Registered: Nov-04
I have a little BMW Z4 and I'm finally losing all the factory junk. Since it's a small cabin 2-seater, I'm just putting a pair of Infinity Kappa Perfect component 6.5/1 up front (100W rms) and a pair of JL audio 6.5" mids (75W rms) in the rear wall behind the seats, nothing in the 4" spots on door or rear wall (good luck finding 4" speakers made for 100W range).

As such, I'll probably put a RF Punch 8004 100Wx4 in to drive these. I *may* add a trunk sub/amp if I think it needs it. My question is this:

If I add a sub/amp in the trunk, does the power need to be in the same range? I was looking at the Infinity Kappa Perfect 10 or 12 inch subs, but they call for 75-400W rms, and I don't know if I should stay low at 100W like the rest or if it would overpower everything by powering the sub at 200W or higher. Also, would 2 amps be too much draw on the factory 120Amp alternator? I don't wanna get into this project so deep that I'm replacing factory battery/alternator.

Feedback on those 2 questions is appreciated in advance.
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5891
Registered: Dec-03
for the perfects, 50-100 wRMS per channel is good.
for the Perfect sub(s) you'd want around 300-350wRMS each.

that should work well as a balanced system.
you can fine tune that with your crossover/head unit.
 

New member
Username: Ohiopilot

Post Number: 2
Registered: Nov-04
And the power draw issue?
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5897
Registered: Dec-03
shouldn't be a problem
 

New member
Username: Ohiopilot

Post Number: 3
Registered: Nov-04
Okay. Now, in a different small vehicle. It has two little 6.5" JL Audio 6w0 subs (75w rms 4ohm ea). Would it be smarter to buy 1 75w 4ohm x 2 channel amp like a Punch P3002, or to wire the 2 subs together for a 2ohm load and run off one mono channel amp?

I'm confused on the whole wiring 2 subs together for lower resist. I understand the lower ohm, but do I need more power? In other words, if you connect 2 75W 4ohm speakers together to create a 2 ohm resistance/load, how much power do you push through that channel? 75W or 150w?

If this were a multiple choice test, which choicewould be correct?

1) Wire the 2 subs on seperate 75W 4ohm channels on a 2-channel amp
2) Wire the 2 subs together on a mono-channel 2ohm 75W amp
3) Wire the 2 subs together on a mono-channel 2ohm 150W amp
4) You can do either 1) or 3) depending on your heat dissipation
5) You can do either 1) or 2) depending on your heat dissipation
 

New member
Username: Ohiopilot

Post Number: 7
Registered: Nov-04
Glass, any answer?
 

Silver Member
Username: Carguy

Post Number: 286
Registered: Nov-04
Hey Ray, are you sure the speakers are subwoofers? They sound too small in size and power to be a sub. Anyways, if it is, wire them into 2ohms (paralle wiring) and use 1 channel mono amp. What I mean by that is an amp with only 1 channel. If you must buy a 2 channel amp, then bridge it so that you get 1. Also make sure the amp is 2 ohms stable.
To answer your question above, it's #2 since your 2 speakers are only 75W.

 

New member
Username: Ohiopilot

Post Number: 8
Registered: Nov-04
Yes, they are called subs by the manufacturer. Check them out for yourself....

http://www.jlaudio.com/subwoofers/6w0.html

Thanks for the feedback. The other challenge is finding a 2ohm amp that small. I'll probably just run #1 in the above list...oh well.
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