Rigged up poweramp

[Kingofpain678]

I received a surround sound 95W power amp at 6 ohms, My plan is to sum the outputs and wire it to a 1/4" output to power my 4x12. My 4x12 is 8 ohms and from what I understand running 6 ohms into an 8 ohms cab shouldn't really cause a problem but is there any reason why summing the surround sound outputs to power the 4x12 wouldn't work?

 

[mshilarious]

I received a surround sound 95W power amp at 6 ohms, My plan is to sum the outputs and wire it to a 1/4" output to power my 4x12. My 4x12 is 8 ohms and from what I understand running 6 ohms into an 8 ohms cab shouldn't really cause a problem but is there any reason why summing the surround sound outputs to power the 4x12 wouldn't work?

Summing? You mean wiring two outputs to a single cab? That's not the same as bridging an amp that was designed to be bridged.

http://www.bcae1.com/bridging.htm

It's important to note that power into a given load is dependent both upon an amp's source impedance (which should be so low as not to matter into its rated load) and its voltage rails. If you want to increase power into a given load, and you are already driving one amp near its rails, lowering the output impedance of the amp won't help (assuming it is already sufficiently low, which it should be).

OK, you don't really have a 6 ohm amp, you have an amp capable of driving a 6 ohm load. The actual output impedance of the amp will be a very small number, should be much less than an ohm. So yes, an 8 ohm load is fine, but lowering the output impedance further probably won't help.

As the article points out, bridging gives you two inverted hot wires, that effectively doubles voltage into the load (and thus 4x power). But if your amp doesn't have that feature, well, it doesn't have that feature.

Now, on the other hand if you rewire your cab for four independent 8 ohm speakers, and use four different channels of your amp to drive each, then you can increase power by four times.

 

[Kingofpain678]

Summing? You mean wiring two outputs to a single cab? That's not the same as bridging an amp that was designed to be bridged.

sort of... the amp is from a home theater system, it's just a surround sound system with a right front and right rear, subwoofer, center, and left front and left rear.

my idea was to solder the positive outputs together and then the negative outputs together, run the positive to the tip on a 1/4" output and the negative to the sleeve of the 1/4" output. then using and instrument cable, run that output to the input on a speaker cab.

 

[mshilarious]

sort of... the amp is from a home theater system, it's just a surround sound system with a right front and right rear, subwoofer, center, and left front and left rear.

my idea was to solder the positive outputs together and then the negative outputs together, run the positive to the tip on a 1/4" output and the negative to the sleeve of the 1/4" output. then using and instrument cable, run that output to the input on a speaker cab.

First, don't use an instrument cable, use a speaker cable. Second, don't do that, reread my post and that link. Your best option with that surround amp is to rewire the cab.

 

[Kingofpain678]

First, don't use an instrument cable, use a speaker cable. Second, don't do that, reread my post and that link. Your best option with that surround amp is to rewire the cab.

Ah, I see... so each channel has to be 90 degrees out of phase, or are does it make a difference how out of phase it is?


and that really sucks, I really had my hopes up

 

[Kingofpain678]

Hmm.... Well, I'll have to read over it again later.

Thanks for the info MSH!

 

[mshilarious]

Ah, I see... so each channel has to be 90 degrees out of phase, or are does it make a difference how out of phase it is?


and that really sucks, I really had my hopes up

Not 90, 180. I don't know why they went into the whole 90 degrees thing. Actually, it's not even phase, it's polarity. The trouble with confusing the two is that reverse polarity is 180 out of phase at all frequencies. That is not normally otherwise true of phase--for example, a capacitor will create a phase shift, but the degree of phase shift is frequency-dependent (depending on the values of components in the circuit).

 

[Minion]

This won"t work for a number of reasons ...
What you are doing when you take all the Positives and the negatives and wire them together is you are paralelling the amps , which would deliver higher power but only into a lower impedance load , For paralelling to work all the components in each amp have to be matched , the resistors to 0.1% , and if it is a discrete amp the Transistors for each channel would also needed to be matched , each amp would also need a matched power resistor at the output so each channel shares the load equally .....

Bridging the amps would entail sending a Positive polarty audio signal to one amp and a negitive to another amp and then connecting the positive amps output to the positive speaker and the negitive output to the negitive of the speaker ....... This allows you to delive twice the power into the same impedance load but if forces each amp to deliver that power into half the load , meaning into an 8ohm load each amp is seeing 4 ohms and if the amp isn"t designed to run on half it"s rated impedance it will quickly overheat and smoke will likely escape ......


Cheers