i'm using a 600W amp by 4 channnels, 2 channels go to my rear speakers and my third channel goes to a sub and i have one extra channel. i was wondering if i can combine 2 channels together so i can have a total of 300w going to my sub. is this possible?

Don't mark my word on this, but I don't see why it woudln't work??

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It depends whether your amp is bridgeable or not. If it is, then you can certainly do it. The vast majority of 4 channel amps in the market are bridgeable. You should also be careful to bridge the amp according to the manufacturer's instructions, and also be aware not going below the minimum speaker impedance that the manufacturer recommends for the particular amp especially in a bridged configuration (this will be twice the minimum load reccomended in 4 channel configuration).

public enemy- thanks a lot!
how do i bridge a amp? does bridging mean to put the 2 channels together? the amp is one of the older kenwoods, so i'm not sure if it is brigable or not, nor do i have the manual to it...i'll check and post up the model numbers tomorrow!

ISh,

To bridge is to simply combine the outputs. Get a big thick wire and connect the + outputs of both the channels you want to bridge. Do the same with the - outputs.

Kuan

In order to bridge the amp you will need to follow the manufacturers instructions. Not all amps bridge in the same manner. It depends on the internal design of the output stages. Most amps bridge by connecting the right (+) output terminal to the speaker's (in your case the subwoofer's) positive terminal, and the left (-) output terminal to the speaker's negative terminal. The remaining two terminals on the amp remain unconected. You may also need to press a switch in the input of the amp to the (mono) position, but then not all amps have that. Again, the above is the way that many amps in the market get bridged, but mot all of them. Some for example connect the right (-) and the left (+). That is why you will need to follow the manufacturer's instructions. If you do not have the manual or the amp does not state on it, then call the Kenwood technical support and they will tell you. Again, keep in mind that if your amp is not 2 Ohm stable you can not connect a subwoofer which has an impedance of less that 8 Ohm to the amp in a bridged configuration. If your amp is not 2 Ohm stable and your subwoofer is 4 Ohm (and most subs are), then you will not be able to bridge the amp with it. The solution will be to either get an 8 Ohm sub or add a second identical sub to your other extra channel.

Okay you need to explain a little further about this one. To me, bridging was just connecting two amplifier sections in parralel. Connecting the left + to the right - is just a series connection. In general, use series when the speaker inductance is high, use parralel when speaker inductance is low. Okay this was what I thought, I don't know why you want to use the series method.

Kuan

Kuan, you are on the wrong end. He is talking about how to connect the wires to the amp. What you are referring to is connecting speakers. It is completely different.

Public Enemy is right. Not every amp bridges the same way. In order to bridge my amp, I press a button and connect just the + from both the left and right channels, leaving the - disconnected.

Why can't you connect two amplifier sections in either parralel or in series just as you can connect speakers? I'm sure talking about amps here. To use an analogy, you put 1.5 Volt batteries in series and you get 3 Volts. To run them in parralel will give you 1.5 Volts, but the resistance will be 1/R+1/R instead of R+R in the case of batteries in series. The current for a parralel bridge will be voltage divided by resistance which will be higher. So I don't see the point in bridging in series, which will void the whole purpose of trying to get more current in the first place.

Kuan

Plus to plus and pushing the button makes sense. You're probably making it mono. The right + and the left - which publicenemy mentioned doesn't seem correct to me, that's all I'm actually trying to say.

Kuan

I have a Kenwood 4 channel amp (KAC-736 I think). To bridge a channel, you use the + of one side and the - of the other, exactly as suggested.

I'm not sure if this thread is about bridging amp outputs or connecting amp outputs in parallel. Bridging and running in parallel are not the same thing. I've read a handful of amp manuals. Some have instructions for bridging, none have instructions for wiring the outputs in parallel. Again, this is from very limited experience... and a non-sparky person.

Regards,
Sixto
91 300SE

thanks for everybody that replied!
i'm actually getting kinda confused by what everybody said...sorry, i'm not very good with this. I don't have a button to push or anything like that. I tried to use the neg from one channel and the pos from another channel and it powered the sub but it sounded the same to me...is there a way to test how many watts is comming out? i also tried to connect both pos together and both neg together but that just make a duh duh duh noise....so i guess thats wrong..

the kenwood model number number number is 6903 and it also says this: 2ohm/4ohm stable...don't know if this is anything...

"Ish" the fact that your amp is 2 Ohm stable means that you can use your existing subwoofer in a bridged mode (assuming that this subwoofer is 4 Ohm, not any less). I do not have the manufacturer's specs for the 6903 but all the Kemwood amps that I have seen and installed (I was working as a professional car audio installer until 4 years ago), bridge by connecting the Left (-) output to the (-) terminal of the speaker and the Right (+) output to the (+) terminal of the speaker. Again the other two outputs remain disconnected. O.K. Now as far as the input is concerned, most amps have a switch (sliding or press-in type) that must be configured accordingly for bridged operation. In other words, connecting the output cables as described above is only half of the bridging process. This switch is usually located in the input side of the amp usually next to the input RCA cables. Check one more time to see whether there is such a switch. Almost all the newer model Kenwoods have this switch. In the older amps this switch was sometimes missing and bridging the amp required either a special "bridging module" or a special "two into 1" cable that is available at Radio Shack. So if your amp does not have this switch, then you will need to get this cable. Keep us posted on what you found.
Again, it may be easier to contact Kenwood technical support (your local car stereo dealer should be able to give you their number), and they should be able to tell you how to proceed on this.

A 2 into 1 cable from Radio Shack does exactly what I've been saying. It's connecting the amplifier outputs in parralel. Since you want to move from low to high impedance, I don't see why the subwoofer won't work with a bridged output. For example, if your amp output is 0.1 ohm, your speaker is 4 ohms. When you bridge the amplifier with the 2 into 1 connecter the total impedance of the source is only 0.05 ohms. This is half of the original output impedance. So why would there be any trouble at all?

Ish, you are increasing CURRENT, not voltage, to the speaker. Voltage is what makes the system sound louder. The specsheet should show the voltage/db gain. Another thing about watts. If you're peaking at 150 watts and double the power to 300 watts, you're increasing headroom by only 3db. This may be a little or a lot depending on the system. If you've been pushing the sub and can't notice any clipping at 150 watts, then you probably won't hear any difference at 300 watts. If you are clipping severely at 150 watts, then you might be able to hear the difference at 300 watts.

Kuan