Impedance And Sensitivity

[ddpaulbell]

My 2x15 cab with 4 ohm 400 watt speakers was wired to be 16 ohm total. I rewired it to 4 ohm total to match the 4 ohm minimum impedance of the head. It doesn't seem to be as loud now. Could it be that the speakers are now less sensitive and therefore less perceived volume output than they were when wired to be 16 ohm?

Does or can lower impedance mean lower sensitivity?

The head is only 100 watt.

[Passinwind]

Originally Posted by ddpaulbell

My 2x15 cab with 4 ohm 400 watt speakers was wired to be 16 ohm total.

Huh?

[Bass_Pounder]

Sensitivity does not change.

Sounds like when you re-wired it, you wired the two speakers out of phase with each other.

[Bassmec]

Originally Posted by ddpaulbell

My 2x15 cab with 4 ohm 400 watt speakers was wired to be 16 ohm total. I rewired it to 4 ohm total to match the 4 ohm minimum impedance of the head. It doesn't seem to be as loud now. Could it be that the speakers are now less sensitive and therefore less perceived volume output than they were when wired to be 16 ohm?

Does or can lower impedance mean lower sensitivity?

The head is only 100 watt.

No it wasn't it could only be wired in series for 8 ohms or in parallel for 2 ohms.

PS If these speakers are in fact eight ohms each, instead of four and your cabinet is wired in series
for 16 ohms and you own a solid state amplifier, you will get a lot more power with the speakers wired in parallel, if they are 4 ohms each and the amp is solid state you will have to make sure its 2 ohm stable to work.
If its an all tube amp and you have a matching output transformer it wont make any difference to the power of the amp as long as the impedances are matched.

[Bass_Pounder]

Originally Posted by Bassmec

No it wasn't it could only be wired in series for 8 ohms or in parallel for 2 ohms.

I scratched my head a little too.............


I think what he is trying to say is his cab is now 4 ohms, and used to be wired for 16 ohms. Since that is possible, I also assumed he simply rewired from series to parallel.

Without more info though, it's a shot in the dark.

[will33]

Most 215's use a pair of 8ohm speakers in parallel. I'd say it's out of phase too. Test the cab with a battery and make sure both cones move out/forward when the battery is +to tip, - to sleeve. Switch the wires on which ever speaker is moving the opposite way.

[Electricblue]

This would go better if we knew what impedance your speakers are. If you wired the cab for 2 ohm total, you are pretty much killing your amp...

[billfitzmaurice]

Originally Posted by ddpaulbell

My 2x15 cab with 4 ohm 400 watt speakers was wired to be 16 ohm total. I rewired it to 4 ohm total to match the 4 ohm minimum impedance of the head. It doesn't seem to be as loud now. Could it be that the speakers are now less sensitive and therefore less perceived volume output than they were when wired to be 16 ohm?
.

No. But if loaded with 4 ohm drivers it could not have been 16 ohms to begin with, nor can it be 4 ohms now. The options are 2 and 8 ohms.

[JTE]

OK, it can't be 16Ω if the individual drivers are 4Ω each. You can only get 2Ω or 8Ω with a pair of 4Ω loads. Simple math....

Parallel impedance-
Z^T=(Z¹*Z²)/(Z¹+Z²)
Two 4Ω drivers in parallel equals (4*4)/(4+4) = 16/8 = 2.

Series impedance-
Z^T=Z¹+Z²
Two 4Ω drivers in series equals 4+4=8.

So, what exactly do you have in there and how are they wired? And make sure which ever way they're wired that you check the polarity as mentioned above.

John

[lokikallas]

Sounds like somebody should have invested in a multimeter before they took apart their cab.