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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Adam Lambert on July 20, 2015, 06:32:12 PM
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Hi all, I have a question about impedance and parallel sub wiring.
Here's the set up:
3 - B&C 18SW115-8 wired parallel in a custom enclosure.
1 - Crown K2 amp running in 4 ohm bridged mono mode (2500w per spec sheet).
I found a calculator online that said with three 8 ohm drivers wired parallel the amp sees a 2.4 ohm load but the Crown spec sheet doesn't give a 2 ohm rating for the bridged setting. Is there an inherent problem here? Can this be optimized to get more out of the drivers?
It also seems the K2 is woefully undergunned to be running three 1700W drivers, but with three subs how could I add an amp to help out? Add 2 amps and run each driver on its own?
Thanks in advance for your thoughts.
Adam
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Hi all, I have a question about impedance and parallel sub wiring.
Here's the set up:
3 - B&C 18SW115-8 wired parallel in a custom enclosure.
1 - Crown K2 amp running in 4 ohm bridged mono mode (2500w per spec sheet).
I found a calculator online that said with three 8 ohm drivers wired parallel the amp sees a 2.4 ohm load but the Crown spec sheet doesn't give a 2 ohm rating for the bridged setting. Is there an inherent problem here? Can this be optimized to get more out of the drivers?
It also seems the K2 is woefully undergunned to be running three 1700W drivers, but with three subs how could I add an amp to help out? Add 2 amps and run each driver on its own?
Thanks in advance for your thoughts.
Adam
The last time I checked-8/3=2.67 ohms-not 2.4.
But that "assumes" the speakers are actually 8 ohms-which they are not.
You did not give any information on the type of cabinet. It could be that the actual impedance is a bit higher-or not.
What you needs is an actual measurement of the impedance (and NOT DC resistance).
The reason Crown does not give a rating for 2 ohm bridged mode is that the amp is NOT recommended for 2 ohm bridged. That would mean that each channel sees a 1 ohm load.
The best way would be to get a second amp, and bridge both amps.
Run 2 drivers off of one amp and the 3rd driver off of the other amp.
The voltage would be the same to all drivers-until you get to the last dB or 2 of maximum output.
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Thank you Ivan this helps a lot!
Each driver is in it's own "box" with 4 ports each (3" tube supposedly "tuned" to the enclosure and driver).
The last time I checked-8/3=2.67 ohms-not 2.4.
But that "assumes" the speakers are actually 8 ohms-which they are not.
You did not give any information on the type of cabinet. It could be that the actual impedance is a bit higher-or not.
What you needs is an actual measurement of the impedance (and NOT DC resistance).
The reason Crown does not give a rating for 2 ohm bridged mode is that the amp is NOT recommended for 2 ohm bridged. That would mean that each channel sees a 1 ohm load.
The best way would be to get a second amp, and bridge both amps.
Run 2 drivers off of one amp and the 3rd driver off of the other amp.
The voltage would be the same to all drivers-until you get to the last dB or 2 of maximum output.
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It is the tuning that will affect the impedance of the finished system. Depending on how high a Q it is tuned to and how the port tuning matches up with the drivers resonant frequency, the resultant impedance can go quite low.
IME, running sub amps at very low impedances rarely works as well as intended. On paper there is more power, but in practice it usually doesn't sound as good.