Connect two Outputs in One Cab

jaferland · #1 10-29-2010, 01:49 PM

Hello,

pretty noob question here. I have a 8 ohms Goliath III cab. I just wan't to know what would happen if I plug a speakon cable from the head to the cab and at the same time plug a 1/4 jack from the jack output of my head to the jack input of the cab. Would it be like if the head was working on a 4 ohms load?

Thank You

J-A

EDIT: To make it simpler... :Plug the two outputs of my amp to the two different inputs of my cab.

billfitzmaurice · #2 10-29-2010, 02:30 PM

Quote:

Originally Posted by jaferland

Would it be like if the head was working on a 4 ohms load?

No. That only happens if you connect two 8 ohm loads, not the same 8 ohm load twice.

anderbass · #3 10-29-2010, 02:41 PM

Unless someone changed the factory wiring in your cab, your Speakon and 1/4" jacks are simply wired together in parallel.

I cant tell what amp you have, but the dual speaker outputs of most (but not all) amps are simply wired together in parallel just like most cabs. Although some are wired in series and some others wired to different legs of the output transformer.

So chances are hooking up the dual speaker cables like you mentioned would just have one speaker cable duplicating the other and the ohm load would remain the same.

kranahan · #4 10-29-2010, 02:46 PM

that would be awesome if it worked!

billfitzmaurice · #5 10-29-2010, 03:18 PM

Quote:

Originally Posted by kranahan

that would be awesome if it worked!

Not really. You're probably operating under the assumption that by having a 4 ohm load you'd be able to 'get all the watts out of my amp' and therefore run louder. That seldom actually happens.

RickenBoogie · #6 10-29-2010, 05:43 PM

Wouldn't that effectively kill the amp? I mean, it's like sending the signal from the amp to the cab, and then back again, no? Either way, don't do it.

edwinhurwitz · #7 10-29-2010, 07:20 PM

Quote:

Originally Posted by RickenBoogie

Wouldn't that effectively kill the amp? I mean, it's like sending the signal from the amp to the cab, and then back again, no? Either way, don't do it.

What he said. It sounds like a recipe for letting the magic smoke out to me.

In a related maneuver, back in the late 70s I used a McIntosh 2105 power amp in my bass rig. It's a stereo amp without a bridging switch (although the 2100 has that capability) and I had a large 2x15 cabinet. I thought it might be cool to run each 15 off its own amp channel so as not to waste half the power of my amp. I wired each of the 1/4" jacks to a separate driver. It sounded great, but the amp would overheat after about 1/2 hour and shut down. Thankfully, Mac amps are pretty indestructible (probably would have smoked a DC300). I finally figured out that the channels were being connected on the ground side by the metal jackplate and it was causing havoc with the amp, causing it to overheat. After building a wood jackplate, all was cool and it sounded great (as does the Mac 30 years later).

Sartori · #8 10-29-2010, 07:22 PM

Sounds like another method for ensuring a trip to a tech.

steveksux · #9 10-29-2010, 07:32 PM

I believe there are 2 possibilities.

1) The wiring is right and you're just using both cables to send the same power to the cab. Kind of like using a thicker cable.

2) The wiring on one of the cables/speakon connectors is out of phase, and plugging them together creates a dead short.

1 doesn't really help, doesn't really hurt. 2 potentially could blow the amp, but most amps have protection circuitry to protect it from shorts, so probably won't destroy anything.

Randy

AwkwardLoudness · #10 10-29-2010, 08:42 PM

Don't plug two speaker cables into the same cab unless each one feeds into it's own set of speaker(s) and the impedances match. There are notably some 8x10 cabs that have the option to power each group of four 10" from separate cables (either from two amps or one) when the stereo mode is selected. The far majority of cabs do not have this option.

jaferland · #11 10-30-2010, 10:39 AM

Thanks for the replies. Probably not a good idea. The goal was to bring only one of my cabs to gigs with smaller stages but to still have the full power out of my amp. The best option would now be to get a single 4 ohms cab.

J-A

will33 · #12 10-30-2010, 10:54 AM

Quote:

Originally Posted by RickenBoogie

Wouldn't that effectively kill the amp? I mean, it's like sending the signal from the amp to the cab, and then back again, no? .

Yes, it'll kill the amp and quick. Kinda like spraying 2 firehoses at eachother, something's gotta give.

billfitzmaurice · #13 10-30-2010, 11:08 AM

Quote:

Originally Posted by jaferland

The goal was to bring only one of my cabs to gigs with smaller stages but to still have the full power out of my amp.A

Read my last post. Power and loudness are not linear with respect to each other.

Calaverasgrande · #14 10-30-2010, 11:42 AM

indeed, this is the big myth with solid state amps. usually going from 8 ohms to 4 ohms only nets you a slight bump in wattage. In order to perceive a real boost in volume its gotta be an effective doubling of watts. It is easier to double speakers to get more volume.
Also, try putting your amp on a couple chairs or tilting it back if you cant hear yourself.