GK 2001 RBP question! Regarding running Bridge mode

calmb4tehpwn · #1 10-05-2011, 08:30 AM

Okay! So I'm looking at picking up a second cab, and will be running bridge mode, GK 2001RBP > Crown 1500 Drivecore > 2x Acme low B4

Now, I know I need to change the amp end of the first speakon cable so it can take the power from both channels. Put the cable into "Bridge mode" capatiblity.

The problem, is that reading on the GK 2001 RB/P manual, it says never to plug a bridged mode speakon cable into the GK 2001RB (which is the pre/power combo of the version I'm using) because their amp is made to run a 4 connection speakon, and running a bridge mode with that will cause issues. My question, as the manual has almost no info specifically on the RBP, which is the pre amp I'm using. Since I'm running it through a crown power amp, which -is- made for 2 pin speakon cables, and -is- made to use bridge mode speakon cables, I should be using a bridge mode speakon, correct? Since the information in the manual -can- only apply to the combo amp, and not to the pre amp specifically?

If I'm being confusing, or if I'm being dumb, please let me know. Otherwise, just looking for a confirmation on my thoughts before I go cranking this through 2 Acmes.

Thanks, guys.

BassmanPaul · #2 10-05-2011, 10:18 AM

What are the impedances of your B4s? If you're using a GK pre-amp to drive a Crown power amp then nothing GK says about the full amp version has any relevance. Many amps have a third speakon only for use in bridge. These just need a standard two pole speakon cable. Make sure you buy the four pole speakon as they seem to have become the de facto standard.

Before you try to bridge I'd try the system out in parallel running one cabinet per channel. You could well find that that configuration is more than loud enough.

calmb4tehpwn · #3 10-05-2011, 10:45 AM

But that's assuming there's any such thing as "loud enough"

It is something that I've considered. Its just that the cabs are made for about 800w and the power amp puts out 600 per channel at 8ohm, but 3100 bridged at 4ohm, so to get its recommended wattage, bridged is the way to run. Thanks for confirming my thoughts. If I ran a 4 pole speakon, would I need to rewire for bridged? Or Would it work as either at that point?

billfitzmaurice · #4 10-05-2011, 11:25 AM

I would not bridge. The power is moot, 600w per cab is plenty. By bridging you double the risk of creased cones and that's about it.

calmb4tehpwn · #5 10-05-2011, 12:08 PM

I was going off memory for the wattage, and was not correct. I have the drivecore 2k, 375w per channel at 8ohm. And 2100w bridged at 4 ohm. The Rws for the acme b4 is 375. So if I go stereo, I will barely scratch half the power these babies are made to run.

BassmanPaul · #6 10-05-2011, 12:12 PM

IIRC Andy states that the B4 takes 750W so that's 1400W for the pair. You want to run up to 2100W. As Bill advised that's a great potential for creased cones. I gig with a vertical stack of a pair of the B2. Each cabinet gets up to 325W from a Carvin DCM1000L or 450W if I use my Carvin BX1500. One cabinet per channel. I've never needed more inside or out. I never have felt the need to bridge in spite of the fact that ALL of my power amps could do so.

xring · #7 10-05-2011, 02:19 PM

I would bridge it and watch the volume. Sorry I can't answer the tech question on the cable. The Drivercore's want a hot signal. I know because I have the 1500 that I had bridged into a 4 ohm Aggie 212. It was loud enough using 1 channel, but I had the attenuator so high that I was getting unwanted extra noise. So I bridged it and turned it down. Much quieter.
I also want to use a speakon for bridging, but can't grasp the 2 wire, 4 wire thing, and I can't find polarity markings on my cable??