Hey everyone! Alright, I am setting up my first system here. I am pretty confident in everything, except my amplifier. Here is what I have:

JL A4300 Four-Channel Amplifer
Infinity Kappa 693.9I, 6x9, 3-way speakers
Infinity Kappa 50.9cs, 5-1/4 speakers

I have three questions:

1. My amplifier runs at 4 x 70W RMS @ 4 ohms, and 4 x 110W RMS @ 2 ohms. If it's bridged it runs at 2 x 140W RMS @ 8 ohms, and 2 x 220W RMS @ 4 ohms. Both my speakers are designed to run at 2 ohms. My 693.9I has a power range of 2-110 watts RMS (330 watts peak power), while my 50.9cs have a power range of 2-85 watts RMS (225 watts peak power). Will my amplifier be powerful enough to run these speakers at a loud, but high quality rate?

2. If the speakers are designed to be run at 2 ohms, will they run at 4? If so, how do you go about setting all that up? Does the amplifier just recognize what it should run at?

3. Do 2 ohm speakers sound just as good as 4 ohm ones do?

Thank you!

Your speakers all have an impedance of 4 ohms. If you want to run them in parallel with each other you will put the amplifier into a 2 ohm load.
If you are running 2 pairs of speakers from a 4 channel amp, then they would be running at 4 ohms. The power in your amp is fine for the speakers.
If you want to run your speakers on half of your amp at a 2 ohm load (110w x 2) and the other half (220w x 1) to a sub, that would be better because your Infinity speakers are going to be kinda bright and will want a sub to counterbalance things.

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#3 you need to hear a 2 and 4ohm speaker for you to tell me but from my ear i like 4ohm speakers
i like the 3ch set up that it up one from sqmonster
or run it as a 2ch to the 5 1/2 and get a sub ,do not us the 6x9s

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here is the low down;
1. for those speakers (which i've owned recently), your amp will deliver it's 2ohm rated power to them...110 watts rms @ 2ohms.

2. those speakers are designed and engineered at 2ohms (the tweeter is 2ohms, the midbass is 2ohms), therefore they run at 2ohms and you can not change them to 4ohms. The amplifier's power output is determined by it's load (4ohm, 2ohm, 1ohm, etc...). Therefore, the amplifier will see a 2ohm load and deliver it's 2ohm power rating into the speakers.

3. That's an individual opinion. Having owned and listen to 4ohm and 2ohm speakers side by side for years, I personally can't hear a difference in a quiet closed garage at night. In a moving car, I know i can't hear a difference. That's up to you to determine though. I can say that the extra power you can leverage from your amp (given that most amps double their 4ohm power into 2ohms) more than outweighs the slight (if there even is one) SQ improvement, and the extra power may actually improve SQ by allowing better control and less clipping at listening volumes (typically more power sounds better than less power as is obvious with deck powered speakers, and outboard amp powered speakers).

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2004 300M SPECIAL
Alpine CDA 9833
Alpine Pxa-h701
Alpine Rux-c701
Rockford fosgate p400-4
Rockford fosgate p4004
Hifonics BX 1205D
JBL c608 GTi
JBL p693
Infinity 2.5" center channel
Alpine type R 12"(2)
all active SQL set up with 1900 watts rms

No they are 2ohm speakers...check the manual.

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2004 300M SPECIAL
Alpine CDA 9833
Alpine Pxa-h701
Alpine Rux-c701
Rockford fosgate p400-4
Rockford fosgate p4004
Hifonics BX 1205D
JBL c608 GTi
JBL p693
Infinity 2.5" center channel
Alpine type R 12"(2)
all active SQL set up with 1900 watts rms