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JBL PRX618S-XLF


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I've played one gig with my new PRX-XLF sub. It was a decent-sized room for a class reunion. It had plenty of thump even though we didn't get a proper sound check, like I would have preferred.

 

Tomorrow, we are playing in a much-smaller bar. So, I'm planning on only using the XLF and not my other HPR151i sub.

 

I was wondering, however, how the XLF sub works when there is only one channel being used. The manual states that it sums a stereo signal into a mono signal.

 

However, if I plug into the left channel only, am I getting only half of the power? The manual doesn't mention this.

 

Even if I'm running a mono output from my mixer into the sub, should I use an XLR splitter to send the signal into both channels of the sub?

 

Thanks

mike

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Even if I'm running a mono output from my mixer into the sub, should I use an XLR splitter to send the signal into both channels of the sub?

 

 

No. If you are running stereo then you should use both inputs to sum the stereo channels into the sub. If you are running mono, it doesn't matter. Either way you can still get full power out of your subs.

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One side of the amp will not mean half the power (non-bridged mode). Amps are rated per channel so, for example, 800 watts per channel will be delivered to each output. If you are asking if 800 watts per channel is the same as 1600 watts...and using only one side means 800 watts or half the power, it really isn't that simple. Just use one side and you will be fine.

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Your splitter idea should work too. But I'm going to join this discussion from a slightly different angle.

 

If you liked your sound last week, I'd set up the same way tomorrow. It's only one extra cab.

 

You just never know. I don't know how many times I wish I had brought that other sub when I've cut down to just one.

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Just to throw this out there, the first gig we used the XLF, we were thinking it wasn't a whole lot of bass relative to what we were expecting, but we ran in mono with daisy-chained tops. The second show we ran in full stereo, plugged into both sides of the XLF, and the difference was noticeable. There were a lot of factors that changed -- it was a completely different venue for example -- but we swear there's a difference between plugging into the left-only and chaining the tops, and plugging in both inputs and running the rig stereo, even with everything panned center.

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Your splitter idea should work too. But I'm going to join this discussion from a slightly different angle.


If you liked your sound last week, I'd set up the same way tomorrow. It's only one extra cab.


You just never know. I don't know how many times I wish I had brought that other sub when I've cut down to just one.

 

The other sub will be in the truck. This place is kinda weird in that on one side, we have a thin wall that separates the band area from the bathrooms. The other side has a bunch of electronic dart boards and kitchen cabinets/counters. Cutting down on one sub would make it a bit less-cramped.

 

My plan is to put the sub to the left, then both tops next to each other, but angled out just a bit.

 

I'm not really sure how I'm going to do it, until I get there and have some time to think about it.

 

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Just to throw this out there, the first gig we used the XLF, we were thinking it wasn't a whole lot of bass relative to what we were expecting, but we ran in mono with daisy-chained tops. The second show we ran in full stereo, plugged into both sides of the XLF, and the difference was noticeable. There were a lot of factors that changed -- it was a completely different venue for example -- but we swear there's a difference between plugging into the left-only and chaining the tops, and plugging in both inputs and running the rig stereo, even with everything panned center.

 

 

This will be easy enough for me to test. I can quickly run a stereo signal to the sub, then switch it out for a mono signal.

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Last night, we first ran only into one channel of the PRX-XLF sub. It had decent output considering the layout of the room and nearby obstacles.

 

Then, using the XLR splitter, we sent a signal into both channels. There was a noticeable increase in output.

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Thank you for confirming this.

 

I presume you could get the same overall result by backing off the gains/attenuators on the tops and running more signal from the board, but it's just as easy for us to run the rig in stereo and not have to worry about that.

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Last night, we first ran only into one channel of the PRX-XLF sub. It had decent output considering the layout of the room and nearby obstacles.


Then, using the XLR splitter, we sent a signal into both channels. There was a noticeable increase in output.

 

 

A powered sub has a power amp built in. In general if it has 2 inputs these inputs are combined to mono. Combining 2 inputs

( if both inputs are in phase and have the same level ) to mono in general gives 6dbs more input level to the power amps.

 

If the sub reaches full input at +6dbu and only *1* input is used you'll need to have your boards output meters at +6 dbu for the sub to give full volume.

If your going into the sub with *2* inputs then your board only needs to be at 0dbu. The 2 signals combined in the amp to mono will equal +6 dbu and the sub will give full volume.

 

Using both inputs causes the sub to reach full output sooner and with less input voltage Per Channel total.

Using just 1 input means you need to have the input voltage higher before the sub reaches full power.

 

In both cases the sub will only put out so much volume. Only the votage required on the input to drive it to that level changes.

 

Dookietwo

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