kenpo_350Z

iTrader: (15)

I am trying to pick a single 12" sub and a mono block amp. I don't get how it says that you get different ratings for 2 ohm or 4 ohm. Some subs are 8 ohm! I am thinking about either a JL 12w1v2, a Kicker cvr, or RF stage 2 12. I have used the California profile APM 1000 mono block amp class d. I had great results with it before pushing a memphis sub.

Can anyone explain this to me and what a great combo would be that won't cost an arm and a leg.

Also are the 08's glove boxes the same size as the 04's. We are building a speaker glove box to take the place of the stock Bose.

THanks!!!

PabloZ

Ohms explained. I will swing at that pitch and let others chime in on the rest...I have some questions about this myself (which I believe support the spirit of this thread).

Disclaimer: this is a layman's discussion, intented to convey general observable behavior, not absolute technical accuracy.

1) Ohms measure resistance to current flow. A 4 Ohm speaker presents twice as much resistance as a 2 Ohm speaker.

2) Amps (amperes, not amplifiers) are a measure of current flow.

1. Multiply Amps by the Ohms and you get Volts. (Amps X Ohms = Volts)
   
2. Another way of saying it : Volts = Amps / Ohms
   
3. Multiply Amps by the Volts and you get Watts. (Amps X Volts = Watts, or Amps X Amps X Ohms = Watts)

3) So, if the Voltage is fixed, raising the Ohms (resistance) will lower the Amps (and therefore, the lower the Watts). That's why an amplifier will have a higher wattage rating at 2 Ohms than with 4 Ohms. It's easier for the current to flow through 2 Ohms, so more of it gets through.

A simple analogy that works well is a water faucet & garden hose. The bare faucet (fully open) puts out a certain amount of pressure (Volts) and therefore flows a certain rate of water (Amps) because there is no hose to limit the flow (Ohms). After the water exits the faucet, there is no resistance (other than atmospheric pressure, but that's getting technical ). When you put a small-diameter hose (a resistance, measured in Ohms) on the faucet, the same pressure (Volts) exists, but less water flows due to that resistance. You can progressively increase the resistance (hold your thumb over the end of the hose) until the "Ohms" are so high that flow stops completely.

So, back to audio...at a given voltage, an amplifier will push more current (measured in Amps, or more commonly, Watts) through a 2 Ohm speaker than it will a 4 Ohm speaker.

Which is where I will stop and ask someone else...in that example, how does the actual sound differ? Will the 2 Ohm speaker cone travel farther (increasing volume) because there are more Watts, or is the 4 Ohm speaker (at lower Wattage) moving just as much?

0jiggy0

iTrader: (13)

The 2 ohm speaker can handle more power. less resistance = more current. current x voltage = watts. If you tryed to hook up 2 4 ohm subs in parrallel and brought them down to 2 ohms them would sound much more powerful but wouldn't last long.

I'm not a very good teacher so if you dont understand something i said ill try to reiterate.

Also what is the ohm rating for the amp your trying to use, basically just get a sub with the same ohm's reading.

BoostedProbe

iTrader: (9)

You can start here:

http://www.sengpielaudio.com/calculator-ohm.htm

The math is simple, if you are not sure just plug in some numbers and you should be able to figure out the basics.

It gets much more complicated when it comes to speakers, as one has to factor in frequency.

Another good source of info:

http://www.howstuffworks.com/speaker.htm

kenpo_350Z

iTrader: (15)

Thanks for the help. That explains a lot. I just never understood how you decide okay this is a 4 ohm speaker. Is it the way the speaker is bridged? How do you know the speaker is getting a certain ohm?

The amp I was looking at using because I had luck in the past was a California Profile Mono Block. AP1000M At 4 ohms it is rated at 310 RMS 620 max and at 2 ohms 500 watts or 1000 max.

The subs I am looking at are either the JL Audio 12w1v2, Kicker CVR, or RF stage 2 punch.

I just don't understand how you make it 4 or 2 ohm? Is it just in the wiring? Thanks for the noob help!

michaeljr6

iTrader: (14)

12volt.com your answer to audio life

michaeljr6

iTrader: (14)

www.the12volt.com

BoostedProbe

iTrader: (9)

If you wire two 4ohm speakers in parallel your net resistance is 2ohms. If you wire them in series then you get 8ohms.

For parallel resistance calculation:

http://www.carstereo.com/help/images..._p_resist2.gif

kenpo_350Z

iTrader: (15)

Okay im starting to understand this. If I run a 2 ohm sub DVC in parallel it will be 1 ohm. I am looking at a Rockford Stage 3 punch, 2ohm 500 rms 1000 max. If I run it at 1 ohm with a 1000 watt amp rated for 1 ohm, would this be a good combination?

adamtaylorpcb

iTrader: (7)

resistance

ADMAN

iTrader: (9)

Yep. DVC is the way to go if you are only going to run one sub. But, you may find that, although you can run the speaker at 1ohm, it may sound better running 2ohm or even 4ohm in stereo. My RF DVC did, once I adjusted the phase. A lot depends on the box and the amp and the placement...and, whether you are going for raw power/thump vs. sound quality.