BillFitzmaurice.info

Bill Fitzmaurice wrote:

djengineer wrote: it seems undesirable to bridge an amp and then run parallel anyway...Correct me if I'm wrong on this! But if it yields more power to T48s then I'm all for it.

You can't bridge and run parallel at the same time. That could be the issue if you're trying to do so. Bridging seldom is of any value into less than 16 ohm loads.

Def not trying to do this. I thought that's what Bruce was telling me to do, and me thinking it's undesirable is correct. I've done nothing more than I've listed in previous posts. To recap: From day one, I've been running my T48s in parallel on channel 2, and DR250s on channel 1. I would like to get a little more power to T48s and just use my amp (Crown XLS 602) only for T48s....The T48s have the recommended 3015LF.

Upon trying to do 1 T48 on each channel, I experience huge cancellation between them. This has not occured with current setup with them paralleled. This rules out 1 of them being wired out of phase. (trying to be an analytical student)

Bruce Weldy wrote: Ok, I see where you are going. While I understand the desire to use the gear - why complicate matters by having to duplicate settings on a second output from the DCX? A Y-cable is not necessary. XLR from the DCX to the amp. Depending on your amp connections:

1. Use an XLR or 1/4" short jumper from channel 1 to channel 2.
desire.

Not trying to sound like a jerk, but how is this less work than turning a knob and pressing a couple buttons to duplicate settings on 2 channels of the DCX? I only have a pair of XLR inputs on my Crown anyway, so a jumper isn't possible.

Thanks guys for all your input. It gives something to have intelligent conversation about. None of my friends have a clue about any of this stuff.

Dual/bridge switch on bridge? Did you jump from 1 sub to the other when running on 1 channel or run a separate cable to each box? Binding posts or speakon outputs out of the amp? Sounds like an XLR or speaker cable is reverse phase. Do you own a cable checker?

Greg Plouvier wrote:Dual/bridge switch on bridge? Did you jump from 1 sub to the other when running on 1 channel or run a separate cable to each box? Binding posts or speakon outputs out of the amp? Sounds like an XLR or speaker cable is reverse phase. Do you own a cable checker?

It's a Crown XLS602. I utilized the dual speakon setup and link to the other. This setup also rules out that a speaker cable is backwards, as I don't have the problem when they are hooked paralleled on one channel (dead horse yet?)

However, I'm thinking that the channel 1 DCX-to-amp XLR may be backwards. I was (still am) using channel 2 for T48s without issues. I start using channel 1 now and almost 100% cancelled out sound. I can turn up on either channel, and not the other, and it's fine. It sucks because my gear is at the bar and the restaurant is upstairs. Not good for me stopping by and testing this theory out, at least until Sat night.

djengineer wrote:
Not trying to sound like a jerk, but how is this less work than turning a knob and pressing a couple buttons to duplicate settings on 2 channels of the DCX? I only have a pair of XLR inputs on my Crown anyway, so a jumper isn't possible.

.

I didn't know what kind of amp you had when I wrote the options that I did. You are right that the 602 doesn't have additional inputs, so a jumper is out. Also, bridging is out since that amp will only bridge at 8 ohms. So, I would suggest building a Y-cable and only use one channel of the DCX, and here's why: You won't be setting the DCX one time and leaving it. You will be making changes to it every place that you set up (or, at least you should). So, by only having to set one channel - it will be less work, and more importantly - less chance of making a mistake. Plus, less wires means less things to go wrong and/or troubleshoot when something does go wrong.....as evidenced by the problem you are having right now. I don't buy Y-cables, I build them myself - but, there are short Ys available if you don't want to build one.

Or, you can run with the second channel......I'm just making suggestions based on my belief that the less cables and options you insert in the signal chain, the better. Less to go wrong and less to fix.

There's more than one way to skin a cat.......

From all the stuff that's been posted, the simplest thing would that one of the xlr cables will be reversed as all other scenarios basically eliminate all the other things in the path. simplest thing to do is to use another xlr cable or to actually test polarity of the xlr cable with either a cable tester or a multimeter.

Other than that and the only other thing that I can imagine is if the signal is summed in an odd way in the dcx and your input cables on the dcx are out of phase. However, the summation of into mono rules unless the dcx is not summing the signal but only using the Left and never seeing the Right unless both L/R outputs are plugged in, but this sounds very unlikely.

If you find no solution, I guess using the y cable would be the only choice.

Or the amp channels are miswired. Or the linking jack and a cable, just to cover bases.

djengineer wrote:Upon trying to do 1 T48 on each channel, I experience huge cancellation between them. This has not occured with current setup with them paralleled. This rules out 1 of them being wired out of phase. (trying to be an analytical student)

Actually, that's not 100% true. If you're at all anal retentive (I know I certainly am!) and tend to set up identically each and every time, you could possibly have an issue that you are likely to not discover. If the speaker cable between the amp and first sub has a polarity reversal and the jump cable between boxes is good, you'll never hear an issue. If the connector on the sub that gets the input from the amp is reversed in polarity, same thing: you'll never notice or hear it. Another possibility is that the one not normally used has a reversal.

How likely is that? Hopefully not very, but even after wiring up hundreds of connections of all kinds I still surprise myself from time to time with an amazingly stupid screw up. The last one was an NL4 Speakon with four conductor cable with one correct end, and the other end had only ONE right connection! Oops, no wonder the loudspeaker made no noise.

An XLR cable with reversed polarity is probably far more likely. That's easy to test with the meter you already own, and doesn't make any noise of consequence. Also confirm the mode switch on the amp is in Dual and not Bridge.

I'm with the others in recommending an XL Y-cable to feed both amp inputs for numerous reasons. One is that apparently the DCX-2496 doesn't have enough DSP to do everything all the time: you can run out of processor. Also, it only takes one error in copying settings to risk ending a driver, and since we always have so much time to make everything happen before the show starts..... </sarcasm>

Good point, I can't be so sure it's channel 1 DCX-to-amp XLR just yet. I will bring extra speakon cables this Sat night to try out and see if I can find the culprit.

Throwing a reversed cable at it will fix it but you won't know the source until you test individually.

Your amp is fine.
Your processor is fine.
Your speakers are fine.
Your approach is making things complicated.

In bridged mode, the two hot / red / positive / + terminals change function.
One of them becomes the negative terminal.

Look carefully at the back of this unit.

http://soundselect.co.za/store/catalog/ ... 000big.jpg

By the red binding posts there is even a very brief warning / note regarding this point.

Anyway... check an amplifier manual or even Wikipedia:"A bridged amplifier or H-bridge is a configuration for creating a larger output voltage swing than that possible with one amplifier by inverting a second amplifier"

One amplifier channel is inverted. Internally. That's the way bridge mode works. Your amplifier and processing hardware are fine. However, you should only use one input channel, or reverse the phase on the second unnecessary cable going to the second unnecessary and not recommended input...
Otherwise the signals will indeed cancel each other out.

Please, make it easy for yourself, just use a single sub out from the processor to a a single input on the bridged amplifier.

Regards, Ben

ben.in.salzburg wrote:
Please, make it easy for yourself, just use a single sub out from the processor to a a single input on the bridged amplifier.

Even better, do not bridge. Read the fine print: Bridging doubles the swing voltage. That's fine if you have to do so for the amp to reach the voltage limit for your speakers per the plans. But if your amp doesn't require bridging to do so, don't.
IMO amps should not be configured with series bridging, as it doesn't give users what they want, which is higher current capability. That only happens when the amp is parallel bridged, and 99% of amps don't have that ability. Series bridging has little real value other than as a marketing tool to allow amp manufacturers to claim inflated wattage ratings.

I've had my XLS602 since '05, and haven't bridged it once yet, so thanks Bill. I will stick with a single T48 on each channel plan.

Thanks everyone for your help. It was my XLR from DCX to amp channel 1. I reversed polarity on DCX to see if that fixed the problem, and it did. Then I tried a different XLR and the problem returned. Pretty easy fix, silly mistake when I made the cable. BTW, not much (noticeable) sound improvement by having them on their own channel anyway.

That's great.......that you found the problem, I mean. Something for the rest of us to keep an eye for.