wiring question

[big stubby]

When I swapped out the speakers in my V4 cabinet I just hooked everything up the way is was done before. However when I was playing it, after a liitle while the speakers began to hum and I immediately shut it down. After searching for a wiring diagram I found this for my 8ohm cabinet.

My speakers have one extra wire going from the (going by this diagram)bottom left + to the bottom right +. Everything else is exactly the same. I would imagine that this is the problem and that by removing it my cab will be in spec for and 8ohm cabinet. I am using 4 eminence basslite S2012 8ohm speakers. What does that wire do to the cabinet and why is it there? Thanks.

 

[georgestrings]

Yeah, I'd remove that wire, and you should be good to go...


- georgestrings

 

[big stubby]

does anyone have any idea why some would add that extra wire and what load did it make it? I am clueless to this stuff.

 

[BillyB_from_LZ]

If I'm understanding what you wrote correctly, there should be no difference. Jumpering the bottom left + to the bottom right + would effectively create two series connected parallel connections rather than two parallel connected series connections.

The math works out the same...two 8 ohm speakers in parallel equal 4 ohms, those two 4 ohm impedances in series equal 8 ohms. As shown in the diagram, two 8 ohm speakers in series equal 16 ohms, then those two 16 ohm impedances in parallel equal 8 ohms. You end up with a system impedance of 8 ohms either way.

The only difference/benefit is if you blow one speaker (i.e. the voice coil opens). In case of the diagram, two speakers would stop working. In the case of how your cabinet is wired, only the blown speaker would stop working. If that happened, the system impedance would rise to 12 ohms (4+8).

 

[Sparky Mark]

Yes, that extra wire is a simple way only to lose output from the blown speaker. That doesn't explain the hum however?

 

[big stubby]

Yes, that extra wire is a simple way only to lose output from the blown speaker. That doesn't explain the hum however?

Sparky, The hum was due to 2 bad tubes in my head. All has been fixed and is now sounding amazing.

 

[Sparky Mark]

All's well then. I've built two 1 x 12 cabs with S2012 and they (almost) blow my 410 away. I think I'll end up with two 1 x 12 Bergs, now I've caught the 12" bug!