Ohms? Bridged? 2/4 channels? Help!

[vincentp83 10+ year member]

So I've decided to just go ahead and use this Amp I have sitting around for my system. I'm on a budget to get some slightly better sound quality and enhanced bass. I listen to rock and just want some fuller, punchy bass above what 6.5" speakers can offer. I've decided to go with just one sub, either a 10 or 12" in a sealed box. I'll probably buy an RF Punch or something similar, it doesn't need to be crazy loud, and it should probably be a lower RMS rated speaker since my amp doesn't put out that much power.

Anyways, this is what I have setup at the moment:

Kenwood Excelon KDC-x890 Head Unit

4 6.5" Alpine SPS-17C2 Speakers

And this is what I'm planning on adding in the near future:

JBL LC-A504 - It's a 200W 4-channel amp, don't know much else

10/12" Sub in a sealed box

Honestly, I have no idea what all of this stuff means. Do I run the amp in 2 channel or 4 channel? Which channels go where? How exactly does it connect to the head unit / speakers? Should I look for a 2ohm or 4ohm sub? Can the amp handle running a sub AND all 4 speakers? Will it even sound better than running them off the head unit?

As you can see, I have a ton of questions. I'm obviously new to this stuff, so cut me a little slack. I think I made good purchasing decisions so far, because the HU and speakers I have sound incredible already, so I imagine it can only get better if I continue to take the advice of people around here.

Thanks in advance

-Vin

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[thch 10+ year member]

basically, and amplifier boosts an AC (musical) signal to a higher AC Voltage (which also resembles the music played).

low impedance (measured in ohms) speakers will receive more power from the amp, or at least try to.

An amplifier "channel" is a distinct audio signal, and basically a seperate amplifer. It makes sense to have two channels for "stereo". and 4 channels for some cases (the rear speakers might not need to be played with as much power as the fronts, ect...).

the HU will send music signals (AC voltage) to the amplifier by means of an RCA cable. failing that, a "line output converter" can be used to take the output of the HU's speaker outputs and convert it into a suitable RCA input for the amplifer. alternatively, some amplifiers have "line level inputs" which perform a similar function.

The amplifier will use a thick cable to the battery to provide it with power. the amp will take the signal from the HU and the power from the battery, and send a high power signal to the speaker. This signal will vary with the music -- silence means no power to the speaker, loud music means more power to the speaker.

so now each channel of the amp has a signal from the HU, and power from the battery. it will attempt to control the speaker. The manufacturer designed each channel to work with a specific "impedance" (measured in ohms). using the correct impedance will mean the amplifier can put out a safe amount of power into the speakers. using a higher impedance will be safe, but the speaker's won't get as much power. using a lower impedance will mean more stress on the amp, and may cause the amp to protect itself or fail. it may work, but the manufacturer doesn't claim it will!

now people got smart one day, and decided to "bridge" amplifers. basically one amp puts out a signal, and the other amp puts out an anti-signal. this doubles the voltage to the speaker, and by power-law, this means 4x power to the speaker. This is a very high power increase. there are two amps involved in bridging, but each amp is still working twice as hard as it would like to. This is why amps are stable to 2ohm stereo and 4ohm bridged (or 1ohm stereo, 2ohm bridged).

Some people became smart (i guess), and realized that they could attach MULTIPLE speakers and even put multiple coils on each speaker (DVC), then wire these in interesting ways to get a desired impedance*.

the amp will have no issue with the sub and the speakers. likely a 4channel amp will work best with 2ohm loads on each channel (4ohm loads on bridged channels). likely you will run a 4ohm speaker on two of the channels (2 speakers), and a 4ohm subwoofer (either a 4ohm SVC, 2ohmDVC, or two 4ohm DVC) on a bridged channel made from the remaining two channels.

later you will become hooked, and will buy a dedicated sub amp, and move the remaining two (4ohm) speakers to the 4channel amp.

*check wiring guides or ANY of the thousand of DVC threads out there.

edit -- I often use "amplifer" and "channel" interchangeably. this may be confusing. a 4channel amp is merely 4 amplifiers in a single case.

 

[thch 10+ year member]

Also, you will want to look into the filtering features offered by modern HU's and amplifiers. Basically they will help you blend the system toghter by allowing the mids to play only the mids, and the subs from playing only the bass. the subs probably won't sound as good as the mids when it comes to vocals, and the mids have trouble playing bass, so the "crossover" made of a lowpass (to pass lows to the sub) and a highpass (to pass highs to the mids) will help out.

you will also want to look up gain settings, keeping in mind that half way doesn't in any way mean "half volume".