Wiring up an amp questions

[cwapface]

Right now i have a cheap kenwood mp3 playing deck with 1 set of 2V preamp outs. My 4" door stockers are almost completely blown and they sound like ass :3d_frown: Soon I will have a set of decent 5.5's waiting to go in plus a nice polk 12" sub, and here comes the amp question. Assuming the amp is a 4-channel with crossovers and everything, would it be ok to have it power the front speakers and the sub while the headunit powers the rear speakers? Would that be better or worse than just having a powered sub and letting the deck power the rest of the speakers?

 

[Dirgle]

You have a few options.
1) Run the sub off the amp and the door speakers of the headunit. This option is best if your Kenwood unit has the option for highpass filtering on it's channels. I'm not familiar with the newer Kenwood’s, but I know the majority of Pioneer have this option so I would assume Kenwood would in some way as well. The highpass is necessary to preserve your speakers as well as the sound quality coming out of them.

2) If your deck doesn’t have this option then most likely your amp does. So run all 4 of your main speakers off of channels 1 and 2 on the amp. Channel 1 for the left side and channel 2 for the right side. Then bridge channel 3 and 4, (assuming there bridgeable, most amps are.) for your subwoofer channel. Then set the highpass filter on channels 1 and 2 for somewhere between 125HZ and 160HZ. Then set the low pass on the subwoofer for the same. Now adjust the gain so the sound level between the sub and the component speakers is about equal. This will give you the best sound quality and make the most of your amp and speakers.

 

[Charlie97L]

more than likely, the rear channels of the amp won't push enough power, even bridged, to run a 12" polk. i was a manager and installer at a custom audio shop for a long time, and the most those kenwood amps will put out (unless it's the higher end eXcelon) is like 35W continuous. that's about 70W continuous, to a polk sub that probably needs at least 150W to run properly.

a lot of people don't know this, but you can damage a sub by running too little power to it... plus you'll end up turning the gain all the way up on the rear channels to get any sound out of the sub, and then you'll fry the amp quickly.

run the door speakers off of the 4 channel, and hop on ebay and grab an alpine or kenwood eXceleon mono amp from a few years ago... you should be able to find a 200-250W continuous amp (check the rating on your polk, once you have that I can recommend some) for about 40-70 bucks. those brands both have excellent longevity, and then you'll have more than enough power to run the sub. you'll just end up with busted speakers and blown amps if you try to jerry-rig your setup with an amp that wasn't designed to do what you are asking it to do.

 

[bluemax]

Sounds like your going to have to use dirgle's option 1, unless you get a monster amp. There are a lot of monster amps that are designed to run full range speaker and a set of subs. Personally on my every day driver, I use dirgle's option 1 with small 6 ohm studio type near-field monitors in the rear. My head unit will not push the 6 ohm speakers and even the audiobahn amp I have has a lot on its hands.

Don't run a tiny multi-channel amp on the 12" polk sub. The sub is going to need a lot of power. Especially if you play your music at decent levels. The power needed to run the sub exponentially increases with higher listening levels. Also check the load (resistance) of the sub. Most speakers for cars are 4 ohms nominal (home speakers are usually 6 to 8 ohms). A lot of subs are 6 ohms. So an amp rated at 100 watts at 4 ohms will probably only push 50 watts at 8 ohms. The higher the resistance, the more power the amp will need to put out to make equivalent sound levels. The manufacturer usually publishes recommended power required. You can always go over the recommended power levels. Get a dedicated sub amp to run off the pre-outs or a monster multi-channel amp designed to run large subs.

 

[cruzinbill]

He should be fine if he gets a decent size 4 channel 2 bridged to run the single sub then the other 2 to run the rear speakers beacause the eac 2 channels are independent on the amp he should be fine. I have seen it done many times before, eventhough to do it bes you should run a mono amp for the sub and a 4channel for the front and rear. here is a hint even tho it is not as good amp do have line level inputs as in you can use your speaker wires from the deck into the amp until you get a better deck with more preamp outs

 

[cwapface]

I don't have an amp picked out yet, the head unit is kenwood mp-228 and the polk sub is 4 ohm but i don't know the max power i can run through it. Which is fine, because i'm not looking for a hard hitting sub, just a modest setup where i can hear sub 100Hz tones instead of the stock 4" crappers. A separate mono amp is completely out of the question, as is a new head unit, sound insulation, capacitors, or cool external crossovers. It's a frickin car stereo, not a home theater

If it came down to choosing between these 3 setups, which would you choose?

1) Head unit preamp out to amp, which powers all 4 door speakers on 2 channels and bridged to power the sub on the other 2.

2) Head unit powers the rear 2 speakers, peramp out to amp which powers the 2 front speakers and the sub

3) Head unit preamp out to amp, which powers the front 2 speakers and the sub. rear speakers unused...

i think that's what it boils down to for me...how do I know if I can run 4 door speakers on 2 channels of the amp without overworking it?

 

[Dirgle]

I would go with option 1 as long as it's a descent amp. Some alpine amps are even designed to be run this way. You won't have any problem running the Sub with the last two channels bridged. It most likely won't be at it's maximum performance, but you said that’s not what your shooting for. Also the type of sub enclosure can contribute to the type of performance per watt you'll receive. The key term in all this is a descent amp. No Audiovox or Jensen amp. With a cheep amp it's possible to burn out the sub channel, just because of the uneven load, Also like was mentioned earlier the poorly controlled power coming from a cheaper amp can destroy a sub over time. So as long as you get a descent amp, I would go with option 1 if I were in your shoes.

 

[bluemax]

You probably don't need 4 full range speakers and a sub. You only need a left and right full range speaker and a sub. The other set of full range speakers just downgrade your audio sound. Use the best sounding full range speaker set-up, probably the larger door set. So technically you only need 3 channels.

 

[antman]

iam using option (2), but i have alittle more adjustable headunit than you, and 5 1/4's in the front. stock rears are just a rear field.

listen to drigle! he sounds like the only one with real experience. plus is the sub a single 4ohm voice coil or dual?
also when your adjusting make sure to turn off the sub and adjust your mids and highs first. make sure that their not going to distorte at your prefered max volume. then adjust your sub. gl