impedance

I am somewhat new to the car audio scence and I have read a lot and learned a lot.  However,  I am still a little confused when it comes to impedance.  Lets use my 6"x9" JBLs to help explain.  I have the GTO927 model.  RMS: 100W Max: 300W  Impedance: 2-Ohms.  Now, does 2-Ohms resistance mean that each speaker applies 2-Ohms resistance individually, or does it mean as a pair they do.  Ie.  If i were to connect these 2 speakers to an amplifer.  How much impedance would I be applying to the amplifier?(I know there are different setups which will vary this answer, which is actually what I really want to know, I would just like the basic knowledge so I can calculate and figure out whats the best setup for myself)

I'm sorry if this has been asked before, I did search, I just couldn't find anything else.  If anyone knows a link, or wishes to explain this to me, even in more detail than I asked,  I would greatly appreciate the help.  I used to own a Geo Metro and I had installed a head unit, with 4 speakers and a sub but I didn't pay much attention to specs.  I just made sure I didnt apply to much power to anything.  I just recently bought a new Sunfire and I want to transfer some stuff over and add some more stuff but I want to make sure I do it correctly.  Thank you very much!  I have taken courses in Electricity and Magnetism so I do understand a lot of the physics equations, if that makes it easier to explain.

ok, that makes sense.  so this is one of the amplifiers i have:

Sony 480W Amplifier XM-280GTX

190W x2 (4 Ohm)
240W x2 (2 ohm)
480W Mono (4 Ohm)

Suitable Speaker Impedance:
2 - 8-Ohm (stereo)
4 - 8-Ohm (when used as a bridging amplifier)

(i have no clue what the 2nd part about suitable speaker impedance means)

So basically if i connect the speakers 2 this amplifier they are each getting pumped with 240W? Right?

I have one more question then.  I'm lookin into buying this amp:

Specifications:

• Max Power, 2 Ohm: 2200Wx1
• Max Power, 1 Ohm: 3000Wx1
• RMS Power, 4 Ohm: 1200Wx1
• RMS Power, 2 OHm: 1700Wx1

It's a class D amplifier.  If I want to connect 3 subwoofers (each with an impedance of 4-Ohms) how would I do so? I just want to verify my logic with you.  If i connect them in series then the circuit has a total of 12-Ohms resistance right?  How would I figure out from there how much power each sub is getting?

P.S. I want to run 2 8" Shallow Pioneer Subs so I can put them right underneath the seats have you heard them or heard anything about them? How do they perform?

y2j514 wrote:

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Suitable Speaker Impedance:
2 - 8-Ohm (stereo)
4 - 8-Ohm (when used as a bridging amplifier)

(i have no clue what the 2nd part about suitable speaker impedance means)

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It is a stupid way of saying that each channel of the amplifier can be connected to no less than a 2-ohm impedence.  When you bridge, say, your JBL's across that amplifer, you are bridging a 2ohm speaker across both channels, for a 1-ohm impedence on each channel.... this would damage the amplifier.  If you connected a 4-ohm speaker across two channels, you would a 2-ohm impedence..

y2j514 wrote:

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So basically if i connect the speakers 2 this amplifier they are each getting pumped with 240W? Right?

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Right.

y2j514 wrote:

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It's a class D amplifier.  If I want to connect 3 subwoofers (each with an impedance of 4-Ohms) how would I do so?

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What amp is it?  If it is 1-ohm stable, you'd wire them in parallel for ~1.3 ohms.  If it is not 1-ohm stable, then you cannot connect 3 subwoofers in that way.

y2j514 wrote:

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I want to run 2 8" Shallow Pioneer Subs so I can put them right underneath the seats have you heard them or heard anything about them? How do they perform?

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Pioneer makes garbage... but good shallow mount subs are hard to come across.

I'd prolly go with something like this:

https://www.woofersetc.com/index.cfm?fuseaction=product.display&Product_ID=3340

or if you have a modicum of patience,

https://mobile.jlaudio.com/jlaudio_pages.php?page_id=213

What amp is it?  If it is 1-ohm stable, you'd wire them in parallel for ~1.3 ohms.  If it is not 1-ohm stable, then you cannot connect 3 subwoofers in that way.

Ok, so I understand why it needs to be 1ohm stable  (1/Req)= 1/4 +1/4 +1/4   Req=1.33....that makes sense.  So the reason I can't do it in series is because it applies 12-Ohms or resistance and thats just too much resistance to the amp to supply the subwoofers with too much power right?

The higher the impedence the lower the power, so you actually would decrease total power output.

P = V*I
(Power = Volts * Current)

I=V/R
(Current = Volts / Resistance)

Based on these formulas you can visually see the relationship between impedance (resistance) and power.