amp, speakers, sub how to know what works

Hello, I am fairly new to car audio. I am putting together a system for my car. I am looking at the following speakers: Rainbow SLC 230 or Rainbow SLC 230.25 NG Amps, I'm considering the eclipse EA4100 4 channel amp. How am I to know what components are compatible? I understand speaker RMS rating, and I am assuming I want to match the output per channel of the amp to the RMS of the speakers as closely as I can? Exactly how important is this? I also don't fully understand 2, 4 and 8 ohms. It seems some speakers are 2 ohm and some are 4 ohm speakers? What does that mean in terms of matching an amp? Finally, I want to run a 4 channel amp, 2 front components and one sub. My understanding is I can "bridge" the amp to run the sub off two channels of the amp? In that case would I buy a sub which has the RMS equal to tho channel off the amp? Thanks for any help anyone can provide.

with that amp it would be safe to get components that are 4 ohm and a sub that is 4 ohm. the reason this is so important to match the minimum ohm rating of the amp to the ohm rating of the speaker is because if you hook a speaker with an ohm rating that is lower than what the amp is rated for it can put your amp into protect mode or cause your amp to heat up faster which can damage your amp over time. the reason for matching the amp's rating to the speaker's rating is because if you hook a speaker with a lower rating than the amp can safely handle it causes the amp to draw more electrical current than it is designed to handle. if you go with a speaker with a higher rating than the amp then that is ok. if your amp is rated to handle a 2 ohm load and you hook a 4 ohm speaker to it that is perfectly fine. it really isnt as complicated as it might seem

Thanks soundnsecurity! your two paragraphs explain in clear detail what I've been trying to understand for the longest time! I think my only remaining question is: When powering a single sub off two channels of an amp (this is "bridging, correct?) so you just multiply the RMS per channel times two, and select a sub with a RMS at least a minimum of this number (example: Amp is 4x75 watts RMS so, I would want to select a sub which has a minimum rating of 150 watts RMS?) Does ohm's come into play when bridging an amp, IE if the amp is rated for 4 ohm speakers, and I bridge, do I now want to run a 2 ohm sub? I assume the answer is "no" but, I just want to be clear. Now I'm off to learn how to set gains...

Some good info: http://www.bcae1.com/gaincon2.htm

Bridging is the correct term.  Your amp is capable of running a 2 ohm per channel stereo load.  Or a 4 ohm bridged load.  If you are bridging the amp, the woofer impedance can be no lower than 4 ohms.

vtvette wrote: Does ohm's come into play when bridging an amp, IE if the amp is rated for 4 ohm speakers, and I bridge, do I now want to run a 2 ohm sub? I assume the answer is "no" but, I just want to be clear.

No, it's the opposite.  If the amp were only rated to accept 4 ohms per channel, bridging a speaker across two channels would require that you use an 8 ohm speaker.  Amps are usually rated to 2 ohms/channel and so the bridged sub would have to be 4 ohms.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Thanks for all the help so far. I think I am starting to get it now... Here is what I have narrowed down to. Could someone tell me if these components will work well together? I want to be sure: AMP Eclipse EA4100 4 channel 400 watt     * Amplifier Class: AB     * Number of Channels: 4     * RMS Power (4 ohms): 75 watts x 4 channels     * RMS Power (2 ohms): N/A     * RMS Power (1 ohm): N/A     * Bridged RMS Power: 150 watts x 2 channels     * Total RMS Power Output: 300 watts     * Peak Power Output: 200 watts x 2 channels     * Total Peak Power Output: 400 watts     * Minimum Impedance Unbridged: 4 ohms     * Minimum Impedance Bridged: 4 ohms     * THD at Rated RMS Power: .05%     * Built-in Crossover High-pass (HP), Low-pass (LP)     * High-Pass Crossover Frequency: 30 - 500 Hz     * Low-Pass Crossover Frequency: 50 - 500 Hz     * Subsonic Filter: 18 Hz     * Signal-to-Noise Ratio: 90 dB     * Channel Separation: N/A     * Bass Boost: 0 - 8 dB Front Speakers: Rainbow SLC 230.25 NG components # Peak Power: 120 Watt # Power Rating: 80 Watt # Sensitivity: 90 dB 1W/1m # Frequency Response: 60-30,000 Hz # Impedance: 4 Ohm # Crossover Slope: 2x12 dB/Oct. # Crossover Frequency: 3,600 Hz # Thermal Protection: HALO + PTC # Mounting Depth w/o/w Ring: 58mm/56mm # Tweeter Mounting Depth: 15mm SUB Image Dynamics ID8V.3-D4 8" sub     * Impedance: 2/8 Ohms     * Resonant Frequency 24.7 Hz     * DC Resistance 1.95/7.8 Ohms     * Electrical "Q" .367     * Mechanical "Q" 3.572     * Total "Q" .332     * Equivalent Volume 1.55 cuft(44 liters)     * One way linear 15 mm     * Cone Area 231 cm2     * Sensitivity SPLo: 85.6 dB     * Power Handling 150rms/300max I plan to bridge two channels on the Eclipse amp to run the single sub. I don't know what the 2/8 ohms is all about - My understanding from their site is it's a 4 ohm sub, with dual voice coil. Again, thanks for the help. I'd hate to make a costly mistake.

yeah, that sub has a dual 4 ohm voice coil. all this really means is its like having two 4 ohm subwoofers in one. this is only there to give you more wiring options. you could use that sub but it will need to be wired a certain way to keep your amp happy when you bridge it. the reason it shows 2 or 8 ohms for the DC resistance is because it has a dual voice coil so depending on how the sub is wired you can get a 2 ohm or an 8 ohm total load. other than this, everything you have picked out will work just fine.