Matching phase when using two amps

[blackba]

I am wanting to run 2 4ohm ampeg bass cabs with piezo tweeters off of my ampeg SVT3pro. The problem is the SVT3pro only goes down to a min load of 4ohms and I don't want to run the cabs in series.

I have a crown k1 power amp. I can take the preamp out of the ampeg SVT3pro and run it into the crown and put both cabs on that amp, but than I miss a tube gain stage from the ampeg SVT3pro. So what I am wanting to do is run one cab off the ampeg's power amp and the other off the crown. The problem is that when I do this, it doesn't sound good, like the speakers are out of of phase. I can't verify this easily since the one cab has thick grill cloth and its hard to see the speakers. The speakers do sound in phase when run off each side of the crown amp.

So my question is what is the best way to change the phase so the speakers are firing in phase?

I have thought of two ways that might work.
1. Swap the positive and negative leads on the crown output. Since I use dual banana plugs, this would be very easy to do. Main concern with this is the piezos and hooking those in reverse.
2. Take the cable from the ampeg preamp out to the crown and on the cable end make the cable so that the shield is to the tip on one end and center conductor is to the ring on the same end.
3. Get a radial big shot ABY and use the polarity switch on the box and run it in between the ampeg preamp out and the crown input.

 

[cardinal]

Have you thought about using something like the Weber Z-Matcher and ditching the complex Crown setup?

But I think you can flip the phase by just swapping the leads on one end of a cable as you suggest in #2

 

[blackba]

Have you thought about using something like the Weber Z-Matcher and ditching the complex Crown setup?

But I think you can flip the phase by just swapping the leads on one end of a cable as you suggest in #2

The ampeg puts out 450Watts into 4ohms. The Z-Matcher only handles 100Watts. Good Idea though.

I am wondering too if just swapping the leads would work to combine two out of face channels on a blackface fender amp with reverb.

 

[Dave L]

Well, flipping the phase (or is it in fact polarity? I can never remember) on cables works perfectly fine with balanced circuits, just flip over the tip and ring and leave the screen on the sleeve, otherwise you need a transformer like that Radial or a Lehle. Does the Crown have balanced in? I know that Ampeg has balanced out.

 

[blackba]

Well, flipping the phase (or is it in fact polarity? I can never remember) on cables works perfectly fine with balanced circuits, just flip over the tip and ring and leave the screen on the sleeve, otherwise you need a transformer like that Radial or a Lehle. Does the Crown have balanced in? I know that Ampeg has balanced out.

Actually I am using the unbalance preamp output. I will try the balanced XLR out set to post-EQ.

So I assume that it is not possible to flip the phase on an unbalanced cable? What about flipping the phase on the speaker polarity?

 

[Dave L]

Correct, you need a balanced-to-balanced connection to flip phase in the cable, if it´s balanced-unbalanced or unbalanced-unbalanced you need a transformer in there.

Yes, you can always wire speakers in reverse, so to speak. Heck, you can even flip the speaker cable if you want to but the barrel of the plug and the connector could short out the signal if you´re unlucky.

 

[PatF]

People do flip the speakers but for bass I would want to push air and have them only excurse outward.

Why run the cabs in series? You have 4 ohm cabs?

For the Fender, maybe a buffer or clean boost pedal would invert the phase 180 on 1 channel.

 

[blackba]

People do flip the speakers but for bass I would want to push air and have them only excurse outward.

Why run the cabs in series? You have 4 ohm cabs?

For the Fender, maybe a buffer or clean boost pedal would invert the phase 180 on 1 channel.

I don't want to run the two bass cabs in series as I will only get 275watts from my amp.

Crown k1 amp just broke, so my focus right now is on fixing that.