# Will impedance rise protect a 1 ohm stable amp on a .75 ohm load? Arc amps



## audijay (Mar 18, 2014)

I have a 13w7 and I am trying get an ARC audio amp to match the rest of my amps, I have an alpine pdx1000.1 but I want to try a different route

Since I have the arc fd4150, I have been looking at the fd1200, ks600.2, and the ks1000.1 and 1200.1

I did talk to an arc rep and he told me to wire the sub at 3 ohms and run the 600.2 bridged, but he noted the amp will be fine but will recognize the lower load and give less power

So I am thinking, the 13w7 can be wired to .75 ohms, that is so close to 1 ohm but I am no expert, and impedance rise will bring the ohm loan up if my understanding is correct and hopefully keep the ohm load in a safe range, but I am really not sure

Please dont recommend the alpine or jl amps, had them already and want something different

Experts should I be safe on a 1 ohm amp? I would like to get the fd1200.1 since I see them around for cheap now and then


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## minbari (Mar 3, 2011)

There is not alot of difference in that impedance. Yes, impedance rise will help some, but that will be mostly at higher volume when the coil is warming up. Also, if you look at the impedance graph of a sub, it is not going to be at minimum impedance at all freq.

At any rate, unless you are not pushing the amplifier to the limits, it wont matter. if your output stage on the amplifier will put out 50amp of current, then at 0.75 ohms, it will run out of current capability before it clips. So make sure you set the gains conservatively and you should be fine.


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## audijay (Mar 18, 2014)

Thanks for the input, I know many people run much lower ohms on amp than they are rated at, but also I'm not running some lanzar or other inexpensive amp, I don't want to fry a nice amp


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## minbari (Mar 3, 2011)

look at it this way.

If you have a 100 watt channel and it is 2ohm stable. that means the amplifier is putting out 14.14vac. at RMS values the amplifier is putting out 7 amps of current (with some safety margin.) so if you ran that amplifier channel at 1 ohm, then you would need to limit the output voltage to about 7volts by keeping the gain low.. (this will limit current to 7amps, the limit of the channel)

problem with this is, of course, that you cant limit current completely. if you set the gain to 7volts( for this example) and then play a song that is recorded louder than what you used to set the gain with, you will exceed your amplifiers current rating. You are really rolling the dice that you wont damage the amplifier, which is why loading it lower than rated can lead to problems. In reality you wont be pushing an amplifier to 100% of capacity very often or for more than a few mS, so, it should be ok. Just the same, loading it at lower impedance that recommended will make the amplifier operate at closer to maximum more often, so it may increase heat and reduce amplifier life.

things to consider.


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## audijay (Mar 18, 2014)

I might just pick up a fd1200.1 for cheap and sent it to arc to test and/or mod it, spoke to someone over there and they are more than willing to put there amps on the bench and play with the internals to how they can be pushed


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## minbari (Mar 3, 2011)

audijay said:


> I might just pick up a fd1200.1 for cheap and sent it to arc to test and/or mod it, spoke to someone over there and they are more than willing to put there amps on the bench and play with the internals to how they can be pushed
> 
> 
> Sent from my iPhone using Tapatalk


ya, making a 2ohm stable amp 1ohm stable is really as simple as lowering the operating voltage on the channel.(thus limiting current to stay in spec) If the manufacture has the ability to do that.


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## audijay (Mar 18, 2014)

minbari said:


> ya, making a 2ohm stable amp 1ohm stable is really as simple as lowering the operating voltage on the channel.(thus limiting current to stay in spec) If the manufacture has the ability to do that.



I just want to make sure a 1 ohm amp is. .75 stable


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## cubdenno (Nov 10, 2007)

Make sure your electrical is up to the task and barring a weak component on the amplifier, you should be OK. If your electrical is not up to the demand, then all bets are off.

A loooonnnnnggggg time ago, I was speaking to an Orion rep regarding the HCCA amplifiers. And basically it came down to this, and I am paraphrasing from an old memory... 

The minimum ohm rating for an amp is based on the speaker coil wiring DCR configuration. So if you wired 8 4 ohm subs for a .5 ohm load on the amp, depending on the enclosure design, the amp manufacturer knew that in all probability there would be a minimum of at least doubling the lowest resistance the amp saw and more likely much more than that3-4 times. especially and like Minbari brought up, the heating up of the coils. And this went for all amplifiers. On a purely resistive load, the amp will deliver "X" watts. But on a reactive load (speaker) the impedance seen varies by frequency to start with and is almost never what the speakers DCR is. So the power the speaker actually sees is more often than not less than what the amp is rated for.

Now, all that taken into consideration, with the amp manufacturer counting on the actual resistance seen by the amp to be much higher than a DCR number, the lower you drop the DCR, the more current that amp is going to pull to make the wattage. Also the more load on your electrical. if your electrical s not up to it, the more voltage drops which causes the amp to pull even more current... **** heats up quick!!


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## minbari (Mar 3, 2011)

audijay said:


> I just want to make sure a 1 ohm amp is. .75 stable
> 
> 
> Sent from my iPhone using Tapatalk


its not! that is why it is rated for 1 ohm  you are asking if you can get away with it and not cause damage and the answer is "probably"

dont take what I said as a recommendation. I would find an amplifier that will give you the wattage you want at 3ohms instead. and there are many reasons for that, more than just what your amplifiers rating is.

If you look at resistive losses in just connectors and wire, you will make up that 0.25ohms pretty quick.

as an example, let assume you have 0.5 ohms of resistance in connections and wire to the subs. with a 1000watt amplifier that is 1 ohm stable you will lose 333 watts of power or about 33%. Take that exact same setup, but with an amplifier that can produce 1000 watts into 4 ohms and your 0.5ohm loss is only a 220 watt loss or 11% loss. that alone is worth running at higher impedance.


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## audijay (Mar 18, 2014)

minbari said:


> its not! that is why it is rated for 1 ohm  you are asking if you can get away with it and not cause damage and the answer is "probably"
> 
> 
> 
> dont take what I said as a recommendation. I would find an amplifier that will give you the wattage you want at 3ohms instead.



I'm looking for a class a/b or h amp that will do that as we'll, they seam to be few and far between


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## minbari (Mar 3, 2011)

audijay said:


> I'm looking for a class a/b or h amp that will do that as we'll, they seam to be few and far between
> 
> 
> Sent from my iPhone using Tapatalk


why just class A/B or G/H? I dont want to get into a Class argument, but especially at bass freq, a good class D does an excellent job and much more efficient than class A/B or G/H.

The JL with Rips or the Alpine (with thier similar circuit) will put out rated wattage at 3ohms easy.


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## audijay (Mar 18, 2014)

minbari said:


> why just class A/B or G/H? I dont want to get into a Class argument, but especially at bass freq, a good class D does an excellent job and much more efficient than class A/B or G/H.
> 
> 
> 
> The JL with Rips or the Alpine (with thier similar circuit) will put out rated wattage at 3ohms easy.



I've had both jl and currently have an alpine, I'm looking for something new really


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## Schizm (Jun 12, 2011)

How about get a 2 channel amp and run a single coil on each channel? 

Sure level matching could be an issue. So could running a 1ohm stable amp at .75... 

For example: the Arc se2300 would give each coil between 700 and 800 theoretical watts according to my birth sheet which would be right about what that sub is rated for. Plenty of other amps to the same

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## audijay (Mar 18, 2014)

Schizm said:


> How about get a 2 channel amp and run a single coil on each channel?
> 
> Sure level matching could be an issue. So could running a 1ohm stable amp at .75...
> 
> Sent from my SCH-I545 using Xparent Green Tapatalk 2



That's an idea, each channel would have to be 1.5 ohms stable, again most amps will be 2 ohm stereo stable so choices are still limited




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## Schizm (Jun 12, 2011)

audijay said:


> That's an idea, each channel would have to be 1.5 ohms stable, again most amps will be 2 ohm stereo stable so choices are still limited


I edited my reply the arc se2300 is 1ohm stable but gives no more power at 1 ohm than it does at 2ohms. Lol


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## audijay (Mar 18, 2014)

Schizm said:


> I edited my reply the arc se2300 is 1ohm stable but gives no more power at 1 ohm than it does at 2ohms. Lol
> 
> 
> Sent from my iPhone using Tapatalk
> ...



Yea umm that's a lot of money though lol


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## cubdenno (Nov 10, 2007)

audijay said:


> I've had both jl and currently have an alpine, I'm looking for something new really
> 
> 
> Sent from my iPhone using Tapatalk


Then look for an OS "cheater" amp
Orion HCCA
PPI ProMos
Hifonics ISIS
Phoenix Gold MPS
US Amps

All were class AB that could rock low impedance loads


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## Hanatsu (Nov 9, 2010)

Amps doesn't care about impedance, only about current. Too much current damages the output stage. Depending on the enclosure type you're driving, the impedance will almost always be above "nominal impedance". Count in VC heat build-up and Revc will be even higher after a while.

Tapaaatalk!!


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## audijay (Mar 18, 2014)

I guess I just need to find an amp to run the sub at 3 ohms, the w7s have the stupidest voicecoils, they could have just made it dual 2s 


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## minbari (Mar 3, 2011)

audijay said:


> I guess I just need to find an amp to run the sub at 3 ohms, the w7s have the stupidest voicecoils, they could have just made it dual 2s
> 
> 
> Sent from my iPhone using Tapatalk


They designed them to work with thier own amplifiers. (which work between 1.5-4 ohms)


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## audijay (Mar 18, 2014)

minbari said:


> They designed them to work with thier own amplifiers. (which work between 1.5-4 ohms)



I know such bs, it could have been just as easy to wire the coils differently 


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## audijay (Mar 18, 2014)

I guess this thread has confirmed I just need to run the sub at 3 ohms


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