Ohms and more Ohms

[jpexpc 10+ year member]

Okay....I get the Ohms thing. I have been trying to figure out a way to phrase this question for Google with no luck. Here it goes:

My brother just bought 2 crappy 12" SVC 4 Ohm Kenwood subs.

He also bought a crappy 2-channel Sony amp.

Like most 2 channel-amps this amp is not stable at 2-Ohms bridged. Obviously he should have chosen 8-Ohm SVC subs or 4-Ohm DVC subs for this amp, but he didn't.

Getting a mono amp is also out of the question for now. He has to keep what he's got.

The amp pushes 800W @ 4 Ohms x 1 bridged. My question is this:

If the RMS running each sub to it's own channel is 125 watts @ 4 ohms, wouldn't it be better to bridge the amp and series the subs? I understand the impedance would raise to 8 Ohms but in reality wouldn't this create 400 watts at 8 Ohms?

It just seems like 8 Ohms bridged at 400 watts would be better than 125 watts x 2. Is my thinking wrong. Is my math wrong?

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[Einzee 10+ year member]

I understand the impedance would raise to 8 Ohms but in reality wouldn't this create 400 watts at 8 Ohms?
It just seems like 8 Ohms bridged at 400 watts would be better than 125 watts x 2. Is my thinking wrong. Is my math wrong?

Aside from the fact that you are confusing yourself with rhetoric..... IMHO, I'd bridge the amp and parallel the subs. According to Ohm's Law, your theory as you stated above is impossible. When 1 parameter changes... so do the other 2 in Ohm's Law.

In conclusion, just simply realize that what you have is what you have. You can only expect a certain amount of performance from your equipment.

 

[dman4486 5,000+ posts]

just because you go from 4 to 8ohm does not mean you will go from 800 to 400wrms.

 

[93dakota 10+ year member]

the specs that you are ginving dont make sence to me(i dont see how it puts out that much more power at 8 ohms even bridged) but if that is tru then it may be the better way to go. Also look at what each chanel will do if it is at 2 ohms if that is higher than bridging both channels to 8 ohms you can run he subs in parallel to get 2 ohms and just run them off of one channel

 

[jpexpc 10+ year member]

So I'm best leaving them on seperate channels?

Could someone explain to me why my figures are wrong? Obviously I realized something wasn't quite right or would have just ran it.

Also, I feel your wording is a little off-beat. Why would you call it rhetoric? It's a simple question and every person avoided giving a plausible response. I would guarantee you that with the standard "Google" explanation of series and parallel wiring my conclusion was legitimate and there are a few people that would have agreed.

 

[aworldcollision 10+ year member]

because if it is 800 watts at 4 ohms, then it is ______ watts at 8 ohms?

I agree, though, it may be best to bridge at 8 ohms...even though you'll lose power.

 

[Einzee 10+ year member]

I apologize if you're thinking that "rhetoric" was directed at you. I was actually making light of your concerns and didnt mean to disrespect.

In theory, what you said about doubling the resistance = dividing/cutting the power out... seems logical and the math will verify that. The problem that I see with adding resistance is that your amp is going to work harder to produce sound. Working harder = Heat. Heat = Dead Electronics.

 

[Trey803 5,000+ posts]

*** on fire!

 

[PaulThompson229 10+ year member]

What are these "Ohms" that you all speak of? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[jpexpc 10+ year member]

Thanks for the responses. I'll leave it the way it is and remind him again to avoid Best Buy at all costs.

 

[RAM_Designs 5,000+ posts]

What are these "Ohms" that you all speak of? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

I have some for sale if you're missing some ohms...6 to be exact.

 

[smd4life 5,000+ posts]

run the amp in stereo

 

[PaulThompson229 10+ year member]

I have some for sale if you're missing some ohms...6 to be exact.

How many should I need?

 

[mokedaddy 5,000+ posts]

Wow this is a little all over the place.

First of all your amp is not 125x2 at 4 ohms and 800 watts bridged at 4 ohms. I am guessing the 800 is MAX watts so disregard this completely.

Secondly you can wire them to 8 ohm mono or 4 ohm stereo and the power will be very close. I usually bridge the amp in this case since running stereo its not likely that the two channels put out exactly the same power and that can be bad if the subs are sharing common airspace.

 

[mokedaddy 5,000+ posts]

How many should I need?

always use multiples of 7. always.