The following is as far as I understand things, and may be incorrect, but I don't think so. I've had these things explaind to me at variouse audio shops -from crappy local stores to Best Buy to awesome local shops- and they all more or less agree.

Its difficult to use a ohmmeter on subs. The 2 or 4 Ohm rating is an average, as the resistance changes with temperature and position of the cone. You just need to make sure that you wire them to be what you want. Also, dual and single voice coils make no difference to the sound produced, it's just a way to get the resistance your amp wants. That being said, very few amps can run at 1 Ohm, and most have half power output at 4 Ohm, so 2 Ohms is what you're really looking for, although there are exceptions.

Power from the amp will divide evenly between the two subs, if they're in parallel or series doesn't matter, that's just a way to give the amp 2 Ohms. So you can -theoretically- run 2 600Wrms subs off a 1200Wrms amp safely, although you should probably leave some wiggle room in case the resistance of the coils isn't exactly the same.

The gain only deals with the input signal. If you have a lower output voltage from your deck -I can't imagine a Jensen having more than 4V RCAs- then you need to turn up the gain a little. Some decks have as little as 2V RCAs, and some have 5V or even 8V. That is why the gain is there. As far as I understand it, the gain does not affect the output power, but will contribute to clipping.

Remember, power=voltsxamps, and the gain is dealing with voltage, so a higher voltage with the same power will be less amps, and less magnetic force to move the cone.

I had a similar thing at one point. I had a 1000W kicker amp (ZX1000.1) and a 750Wrms sub (Kicker CompZX 12"). I kept the gain lower, but still kept blowing them out, I asked the good audio shop why, and they explained about the gains as I just did. After replacing that sub 3 times, I was done with it, so I bought 2 Memphis C3 12", and haven't looked back.

 

How do you make sure an amp is firing good?

When you say difficult to use an ohm meter on subs, what exactly do you mean? Hard to measure the ohms of the coils? Hard to set the gain? Please clarify. But yes, as the cone moves the impedance of the sub changes, this is commonly referred to as box rise. This phenomenom is a major reason why you can take a sub and put it in two different boxes with the same amp in the same car and get two different results.

Just because you have your amp wired to 1 ohm doesn't meant that's the load it's seeing since the cone is constantly moving the load is constantly changing. So that 1 ohm load you thought you had on the amp can actually rise to 4 ohms depending on the design of the box and how much control it has on the excursion of the sub. However, for the daily ground pounder this shouldn't be a concern at all. Why? Because the music we play is dynamic, constantly changing. But for a spl burp car, box rise is extremely important because it's a one note wonder so they want as little rise as possible to ensure the maximum power output from the amp.

Not true. There are tons of amps that can run at 1ohm! That's true for both major name brands as well as the lesser known underground brands.

If the gain does not effect the power, why does the sub stop moving when you turn the gain all the way down? Are you saying that turning the gain down like that still results in the same amount of power being put out by the amp as if the gain were turned up halfway? It absolutely effects output power, TO A POINT. Once you turn the gain up past a certain point it won't increase power output, it'll just induce clipping as turning it too high it forces the amp to put out a signal thats higher than the signal it's getting.

 

I'm saying that if you measure the resistance across a sub that is properly wired for a 2 Ohm output, you may actually measure 1.5 Ohms, which may leave you guessing whether you have 2 or 1 Ohms on your sub.

I didn't say no amps can run at 1 Ohm, just that most are 2 Ohm stable. I've seen very few amps that list 1 Ohm output wattage, but many that list it for 2 and 4 Ohm.

I suppose I wasn't entirely clear and correct on the gain control. This article seems to say more of what I was driving for, but didn't get to.

http://www.teamrocs.com/technical/pages/gains.htm

 

and another thing to think of as far as the subs go. more is not always better.

 

you'd have to take it to a shop and have them put it on a scope, you really can't tell with just yuour every day DMM, and unless you wanna drop 1000$ on a meter i'd suggest dropping a couple bucks or seeing if they'll give ya a free test.

 

So you're saying it's difficult to ohm out subs with a dmm? LMAO! Man I hope you're joking. But anyway, I wasn't talking about ohming out a sub with a dmm, I was talking about setting the gain with one. But anyways, the fact that the impedance on a sub changes as the cones moves is irrelevant anyway cause nobody ohms out a sub while it's playing.

I know, you said "very few", but that's not true. There are tons of sub amps that are 1 ohm stable. Would you like me to put together a nice list for you of amps that are 1 ohm stable?

Can't tell what? Where to set the gain at or what impedance your coils are? There's a very helpful graph that i've been using for years to set my gain properly and have not had a single failure yet, using this graph and following the instructions at the bottom of it on how to set the gain is very easy and alot better than doing it by ear.

 

Very nice. Ive seen this before and it does the job very easy. ******This should be a sticky***********

 

I'll post a new thread for this and see if a mod can sticky it