Taco

iTrader: (1)

I need to know what kind (how many channels, etc) of amp I need for my setup.

I have 2 Punch HX2 subwoofers and would like to power them in the most logical, practical way, without spending a lot of money.

What do I need?

Thanks so much!
Taco

***EDIT***

Is Volfenhag a good brand of amp? I have found a lot of their amps on eBay and they are pretty nice looking and relatively inexpensive...

Thanks!

Daley

I've never heard of that brand of amp. What I've found in the industry is that there are a lot of 'off-brand' amplifier manufacturers because it is inexpensive to build a cheap amp and make it look flashy. The cost of a good amp ensures you that you're getting true power, and not some off-the-wall claim. Stick with name-brand stuff, and you won't go wrong. As for powering those subs, get yourself a 2-channel with a couple hundred watts and turn it loose. You'll like what you have, and will be able to enjoy it for a long time.

SilverWS6_2002

They sell Volfenhag @ the local flea market near my house. I always have kids coming into my shop asking to hook them up. They aren't bad, they just aren't good. Enough said. I assume your Rockford Punch HX2's are DVC, so a good 2 channel with say 250-300 watts RMS per channel @ 2 ohms should be great for them. I suggest running them in 2 ohm stereo.

Taco

iTrader: (1)

Can you explain 2 ohm stereo? What exactly does that mean? I don't think i said earlier, but I am a total noob when it come to the technical end of stereo compnents. I know how to hook the hot wire and not-hot wire to one side of the amp and the hots and nots out of the other side into the speakers to make them make noise, but that's about it!

Thanks in advance!
Taco

Daley

Ohms is a measure of resistance, or more specifically impedance when talking about audio stuff. If (as a very basic explanation) a given speaker resists the flow of energy at a value of 4 ohms, a 2 ohm speaker will have less resistance to the flow of energy than the 4 ohm model. Wiring two voice coils in parallel (+ to +, - to -) effectively cuts that resistance roughly in half, thereby allowing the amplifier to push more energy, making it louder. The reason we don't just wire everything to be at zero ohms is because amplifiers are designed to operate at a certain impedance (resistance). The more you lower the operating impedance, the more work the amp has to do, thereby heating it up, potentially overworking it.

Hopefully this confusing explanation has actually made some sense and helps out. Good luck!

2MuchRiceMakesMeSick

Volfenhag is a german brand. In my opinion...stay away.

This may be too technical but heres a good explaination of ohms law...




Understanding what ohms are and how they relate to car audio is most helpful when trying to determine optimal wiring configurations for connecting multiple speakers to an amp. There are some basic electrical engineering formulas I will use on this page. Fortunately they are fairly simple.

Ohm's law: Current = Voltage / Resistance or I = V / R
You can rearrange this formula in a couple ways: V = I * R and R = V / I

Power equation: Power = Voltage^2 / Resistance or P = V^2 / R
Rearranging this formula gives us: R = V^2 / P and V = SQRT(P * R)

Using Ohm's law we can derive some more power equations: P = I^2 * R
Rearranging gives us: I = SQRT(P / R)

Abbreviations used on this page are:
I : current, measured in amps
V: voltage, measured in volts
R: resistance, measured in ohms
P: power, measured in watts

With that out of the way we can get down to business. As stated earlier, ohms are a measure of electrical resistance. It helps in this discussion if we consider amplifiers to be perfect voltage sources.

Consider this 25 watt amp:

P = V^2 / R

Most amps are rated into 4 ohm loads so we now have:

25 watts = V^2 / 4 ohms

Solving for voltage we get: V = SQRT(25 * 4) = 10 volts

So our 25 watt amp can be considered here to have the ability to produce up to 10 volts output.

Now let us consider what happens when we connect two speakers in parallel to the amp. At this point I am going to introduce some more formulas. We are considering speakers to just be simple 4 ohm resistors for this discussion. There are formulas which dictate what happens when you combine resistors in various ways. Before that we need to explain what is meant by parallel and series ConneXions.

Each channel of an amplifier has a positive (+) and negative (-) connection. The amp develops a voltage between these two terminals and this voltage is what drives the speakers. The equivalent resistance of what you connect to the amp is referred to as the load.

Normally when connecting a single speaker to a single amp channel you merely connect the "+" terminal of the speaker to the "+" terminal of the amp. Then do the same thing for the "-" terminals. Things get more complicated when you are connecting multiple speakers to a single amp channel. In a parallel configuration you connect both "+" terminals of the speakers to the "+" terminal of the amp. Then do the same thing for the "-" terminals.

A series connection is a little more complicated. First, you connect the "+" terminal of the amp to the "+" terminal of one of the speakers (let us call it speaker A). The next thing you do is connect the "-" terminal of speaker A to the "+" terminal of the other speaker (speaker B). Lastly, you connect the "-" terminal of speaker B to the "-" terminal of the amp. You can see in this connection that power from the amp goes through both speakers one after the other, hence the name "series."

Finally, here are the formulas that tell you what resistance load you end up with when wiring multiple speakers:

For two speakers in parallel:

1 / Rt = 1 / Ra + 1 / Rb

where Rt is the total equivalent resistance or load and Ra and Rb are the resistances of the two speakers. You can see that you can use speakers of different resistances but there other implications of doing that which are usually undesirable because the power will not be spread evenly between the speakers.

Working through the math if you put two 4 ohm speakers in parallel you get:

1 / Rt = 1 / 4 + 1 / 4 = 1 / 2, Rt = 2 ohms

The equivalent resistance is exactly half of what we started with. We will look at the implications of this a little later. Let us do another example first with three 4 ohm speakers in parallel:

1 / Rt = 1 / 4 + 1 / 4 + 1 / 4 = 3 / 4, Rt = 4 /3 = 1.33 ohms

You can see that as you put more and more speakers in parallel the equivalent resistance will drop further.

Next lets look at the equivalent resistance for speakers in series:

Rt = Ra + Rb

Now that is easy! You just add the resistances for each speaker so putting two 4 ohm speakers in series will you give a single load of 8 ohms.

With that background out of the way we can look at what effect these different wiring combinations have on the amplifier. Going back our 25 watt (10 volt) amplifier with a single 4 ohm speaker we have:

Current = Voltage / Resistance = 10 / 4 = 2.5 amps

So when this amp is producing maximum power (25 watts) into a 4 ohm load, the load will draw 2.5 amps from the amp.

Now let us look at what happens when we connect two 4 ohm speakers in parallel (which gives us a 2 ohm equivalent load) to this amp:

Power = Voltage^2 / Resistance = 10^2 / 2 = 50 watts

This is seems great! Our 25 watt amp is now producing 50 watts but there are some complications. Let us see the current now:

Current = Voltage / Resistance = 10 / 2 = 5 amps

Even though our voltage is still the same (10 volts) our current has now doubled from 2.5 amps to 5 amps. If the amp has the capability to produce this much current and dissipate the heat that this will generate then everything will be fine. One way to determine if your amp is capable of this is to look for power ratings that are given into 2 ohms in addition to the normal 4 ohm rating. Further if the power doubles into the 2 ohm rating then the amp has ample current capacity. Another clue to tell whether the amp will work with 2 ohm loads is look for the phrase "2 ohm stable." Being 2 ohm stable only means that the amp will function with 2 ohm loads; it does not necessarily mean that the amp will produce more power into 2 ohms. If you attempt to use a 2 ohm load with an amp that cannot handle it a well designed amp will shut itself off or blow a fuse and a poor one could be permanently damaged.

2MuchRiceMakesMeSick

Next let us look at a series connection with two 4 ohm speakers. This will give us an 8 ohm load and we will use our 25 watt (10 volt) amplifier again:

P = V^2 / R = 10^2 / 8 = 12.5 watts

Our amp is now producing only half its power rating! And the current is:

I = V / R = 10 / 8 = 1.25 amps

The current is 1/2 its original value as well. Series ConneXions are not used as often as parallel ConneXions because they reduce power. However, they are easier for your amp to drive since they draw less current.

Another option that is often available is to bridge an amplifier. This process takes 2 amp channels and combines them to act as a single more powerful amp channel. How to do this to an amp and wire everything varies so please do not ask me how to bridge your amp. I can explain the effects of it though.

What typically happens when you bridge an amp is that the voltage it can produce doubles. Our 25 watt (10 volt) amp can now produce 20 volts. Let us look at how that affects power:

P = V^2 / R = 20^2 / 4 = 100 watts

This is 4 times the original power of the amp but let us look at the current situation:

I = V / R = 20 / 4 = 5 amps

So now we see even with a regular 4 ohm load the current is already double what the normal value (2.5 amps) was. For other reasons the power usually does not usually quadruple when you bridge an amp but will typically at least double. Connecting a 2 ohm load to a bridged amp raises the current requirement even more. However, if your amp can handle it then you will be squeezing a lot of power out of the amp.

In fact, many people use that kind of setup in competition where the classes are judged by the power rating of the amps in the system. A 25 watt amp can produce many times more power when bridged and driving low resistance loads so the competitor gets more power than what appears on the surface. Zapco and Phoenix Gold make amps which are able to drive such low resistance loads (sometimes as low as 0.5 ohm!)

Some final notes:

On this page I have considered amplifiers to be perfect voltage sources. They are not though and they have some internal resistance which lowers power output slightly.
I have also considered speakers to be perfect 4 ohm resistors. In actuality the resistance of the speaker depends on the frequency the speaker is playing. For example, a speaker may have a 3 ohm resistance at 80 Hz and a 9 ohm resistance at 300 Hz. If you were to make a plot of resistance versus frequency you would get what is called the impedance curve of the speaker. Also, speakers act in some ways as inductors and capacitors so a true model of a speaker must include those components as well. How does this affect the sound you ask? Well if you have an amp that has very weak current capability it may work fine into perfect 4 ohm loads but when you connect our real speaker which has an impedance dip at 80 Hz the amp may have difficulty and smear sounds that have 80 Hz components. These are minor but audible effects. This is why it is good to get a 2 ohm stable amp even if you never plan on running 2 ohm loads.
Placing speakers in parallel and bridging amp channels are effective methods for increasing the power in your system assuming your amp can handle the increased demand.
Use a series configuration when you need to raise the effective resistance of the load. This occurs more often when you are using dual voice coil speakers.
Dual voice speakers have two speaker ConneXions on them. This typically increases power handling capability and gives you more wiring options. For example, if you have two dual 4 ohm voice coil speakers you can get a single 4 ohm load which is suitable for connecting to a bridged amp. You would do this by connecting the voice coils on each speaker to each other in series. This would give you two 8 ohm speakers. Next you put those two 8 ohm speakers in parallel and this will give you a single 4 ohm equivalent load.
Be aware that using lower resistance loads and bridging produces a greater load on the amp. Well designed amps that cannot handle the demand will either shut themselves off or blow a fuse. A poorer designed amp can permanently damage itself. Also, even if an amp works in these configurations it will probably generate more heat so ventilation is even more important.
As mentioned earlier ohms are a measure of electrical resistance. You should be able to understand why resistance changes affect the amp power as it does. If you raise the resistance the amp is not able to drive as much current through the load and thus you get less power. If you lower the resistance of the load math says that more current will be drawn from the amp. Assuming the amp can handle this you get more power.
To understand why series and parallel configurations have the effect on resistance that they do consider this. When you connect speakers in series current must flow through both speakers and so it hits the resistance of both speakers. When you have speakers in parallel, the current has multiple paths since it can go through either speaker so the equivalent resistance is always lower than that of either speaker alone.

LS1_2NV

iTrader: (3)

Spoken like a true Physics Professor... Always been a fan of Ohms Law...

Daley

Dr. Justin, do I see a sticky developing here? Might want to put this in one of the FAQ's that you guys have made - lots of good info here.

MadIceV8

iTrader: (12)

2MuchRiceMakesMeSick - Ya you did do a really good write-up on this and should make it into a new post and have it as a 'sticky'

2MuchRiceMakesMeSick

Sticky it is!

bottlefed90GT

What we need to know is if the speakers are dual voice coil or not, and how many ohms the speakers are. NOBODY can tell you the proper channel amp to get without that information.

If they are single voice coil 4-ohm speakers, getting a 2-channel amp would be stupid/inefficient. You would actually pull the same amount of watts hooking those two 4-ohm speakers in parallel to 1 channel!! You would have to hook these speakers up stereo, which would pull the advertised rms per channel at 4-ohms out of the amp. You would want either a mono amp or a 4-channel amp with 2 4-ohm speakers. With a mono amp, the ones I've seen, are made to accept two 4-ohm spoeakers, and the amp is bridged down to 2 ohms, pulling the maximum amount of power out of the amp. Using a 4-channel amp, bridging one speaker to channels 1&2, and the other speaker to channels 3&4, you are running at 2-ohms, and pulling the maximum amount of power from the amp. I am explaining this with the understanding that we are working with regular amps that are 2-ohm stable in stereo or bridgeable mode. Here are some general hook-ups that I've seen/done.

one 4-ohm speaker=2 channel amp
one 2-ohm speaker=mono amp
two 4-ohm speakers=mono or 4-channel amp
two 8-ohm or 2-ohm speakers=2 channel amp (8-ohm speakers you would parallel and bridge, and 2-ohm speakers you would series and bridge)
one dual 4-ohm voice coil speaker=mono amp or 4-channel amp
one dual 8-ohm or 2-ohm voice coil speaker=2 channel amp
two dual 4-ohm voice coil speakers=2 channel amp
two dual 8-ohm or 2-ohm speakers=mono or 4-channel amp

WhiteBird00

iTrader: (4)

Nice write-up. One question though - isn't it easier to calculate total impedance of parallel speakers by just adding up the ohms and dividing by the number of speakers (essentially calculating the average) rather than using 1/Rt = 1/Ra + 1/Rb + ... ? You get the same answer and it's easier to remember.

bottlefed90GT

Only if you are working with speakers of the same ohm/resistance. Once you start parralleling a 4-ohm and 8-ohm speaker, your system would be 6-ohm, right? The true resistance would be 2.66667. (4x8 / 4+8)

Richiec77

iTrader: (3)

Right. Better to teach the Correct Way 1st, than to teach the Tricks and have to un-learn that.

02Z28LS1

iTrader: (2)

inefficient? yes.....stupid? not necessarily.

the lower the impedance load on the amp, the higher the temperatures will be, due to the extra current that it is having to push. in a hotter climate (such as here in Texas during the summer), this could cause the amp to die before its time. it's generally not a concern if the amp has plenty of air around it to dissipate that heat, and a large enough heatsink to get that heat to the outside air, but it is still a factor to consider.

also, the more current that is drawn by the amp(s), the larger the requirement for the gauge of power wire....not to mention the more current that is drawn from the vehicle's power source, which in some cases, can cause further problems (such as headlight dimming, and faster drain on the battery when the car is not running).

so i would not really call someone stupid for running the amp at only 4 ohms....

spy2520

iTrader: (3)

What are your recommendations for running an amp at 1 ohm? I have a 1 ohm stable sub and two dual 4 ohm subs.

The amp (PG Xenon X400.1) says:
"Maximum Power Output From 1 - 4 Ohms"

Okie5.3

iTrader: (1)

thank god for pictures


http://www.crutchfield.com/S-IslS0c7...ech/kb334.html

http://www.crutchfield.com/S-IslS0c7...ch/kb1158.html

spy2520

iTrader: (3)

So now i have to do math? I just got finished with math. Anyway, there is mention of having to do certain things like run bigger wire for lower impedance amps, does this apply when the amp is stated to have the same power from 1 to 4 ohms? And is there any simple, non-math way for someone to confirm that i can run my subs at 1 ohm to the amp.

02Z28LS1

iTrader: (2)

in your case, having two 4-ohm DVC subs, and having an amp that it stable to 1 ohm, you should be ok. 4 voice coils total divided by 4 ohms per coil = 1 ohm.

the easy method to figure the impedance when wiring in parallel (ONLY to be used when using speakers of the same impedance) is # of coils ÷ impedance of each coil = final impedance.

so:

a ÷ b = c

a = each coil's impedance
b = # of coils
c = final impedance

in your case, a=4, b=4 so:

4 ÷ 4 = 1

so yes, you can run your two DVC 4ohm subs in parallel to achieve a 1 ohm load, and as long as your amp's documentation says it's stable to 1ohm, you're golden.

see THIS PAGE for general guidelines on how to figure out what gauge of wire you will need to use. obviously, you will need to figure out how much TOTAL wattage your system will put out, not just the wattage for one amp.