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Author Topic: Am I routing this correctly? Effectively?  (Read 2136 times)

Sam Costa

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Am I routing this correctly? Effectively?
« on: August 01, 2017, 10:28:30 pm »

 Hello guys, wanted to pick your brains a little bit  and get your professional opinions on.

 This is only to get information on my sub amp and if you feel I have it routed correctly, also would like to know if this is the most effective way to run this type of set up (amp and speaker cabs)

I use a QSC 4.0 for my subs,  I love the amp and it's never left me hanging.  It runs in conjunction with a four-way digital crossover so depending on the venue I adjust the frequencies and amount of low-end needed.

 The routing I have always run it on was left and right stereo mix. Don't know why, but I feel I can get a bit more sound/wattage  if I run it in bridged mono, is this correct? Currently I'm going from the output of the amp into one of my dual 18 inch sub cabinets then I use the thru Port of that cabinet and jump it to the next which is also a dual 18 inch sub cabinet.  I use this confirguration for both Left & Right outputs on the amp.

However, would it be more effective to get more wattage from the Amp if I were to run the system this way but in a bridged mono set up?

« Last Edit: August 01, 2017, 10:33:34 pm by Sam Costa »
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Mark Amber

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Re: Am I routing this correctly? Effectively?
« Reply #1 on: August 01, 2017, 10:51:15 pm »

What kind of subs?

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Steve Crump

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Re: Am I routing this correctly? Effectively?
« Reply #2 on: August 01, 2017, 10:58:51 pm »

Hello guys, wanted to pick your brains a little bit  and get your professional opinions on.

 This is only to get information on my sub amp and if you feel I have it routed correctly, also would like to know if this is the most effective way to run this type of set up (amp and speaker cabs)

I use a QSC 4.0 for my subs,  I love the amp and it's never left me hanging.  It runs in conjunction with a four-way digital crossover so depending on the venue I adjust the frequencies and amount of low-end needed.

 The routing I have always run it on was left and right stereo mix. Don't know why, but I feel I can get a bit more sound/wattage  if I run it in bridged mono, is this correct? Currently I'm going from the output of the amp into one of my dual 18 inch sub cabinets then I use the thru Port of that cabinet and jump it to the next which is also a dual 18 inch sub cabinet.  I use this confirguration for both Left & Right outputs on the amp.

However, would it be more effective to get more wattage from the Amp if I were to run the system this way but in a bridged mono set up?




Are you running a total of (4) double 18s, (2) per side? Are the cabinets 4 ohm cabinets? Haven't looked at the specs on the QSC mentioned, but is it rated at that low of an impedance bridged?
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Sam Costa

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Re: Am I routing this correctly? Effectively?
« Reply #3 on: August 01, 2017, 11:57:53 pm »

What kind of subs?

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I'm using the Carvin TRX218 sub cabs. Depending on the venue, I use 1 per side, but probably deploy the second sub cab at 80% of the shows I do.
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Chris Grimshaw

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Re: Am I routing this correctly? Effectively?
« Reply #4 on: August 02, 2017, 04:07:20 am »

They're 4ohm cabinets, and AFAIK the QSC PL series will drive down to 2ohm on each side, or 4ohm when bridged.

So, you can run up to 2 on each side in stereo mode, for 4 cabs in total. Each one would get about a kilowatt.
Or, you can run a single cabinet with the amp bridged. That cab would get about four kilowatts.

Chris
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Tim McCulloch

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Re: Am I routing this correctly? Effectively?
« Reply #5 on: August 02, 2017, 04:32:24 am »

Sam, when you bridge an amp you get more voltage out because both channels are essentially in series; what you do not get is greater current capability.

Chris Grimshaw's analysis is correct, and frankly I'd rather see you power them in stereo, 2 per channel.  You'll save on reconing that way.

The dirty little secret is that more large coil woofers go into power compression when sustained average power is surprisingly low (think low hundreds of Watts) after a relatively short time.  Applying more voltage only gets turned into heat, not more acoustic output.  Don't cook your voice coils.

Also, when you bridge an amp you pick up an additional 6dB of gain.  If you don't compensate for this you'll have a real big impression, "bridging the amp is MUCH more powerful", but it would be wrong.  The amp has the same current potential regardless of gain so when the gain is higher, it's louder, until you run out of current, which will happen sooner.  TANSTAAFL.  I suggest if you bridge an amp, go into your system processing and reduce it's pass band output level by -6dB and do it before you even think about turning the amp on.  Your system will respond as it did before.

If this were my rig I'd put 2 218 per channel on the PL4, keep the air vents clean, and beat it like a rented mule. YMMV.

ps. no mules were harmed in the making of hyperbole.  Honest. 8)
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Chris Grimshaw

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Re: Am I routing this correctly? Effectively?
« Reply #6 on: August 02, 2017, 07:40:49 am »


The dirty little secret is that more large coil woofers go into power compression when sustained average power is surprisingly low (think low hundreds of Watts) after a relatively short time.  Applying more voltage only gets turned into heat, not more acoustic output.  Don't cook your voice coils.


Not many manufacturers give you that data, and those that do...
Well, it ain't pretty.

The Beyma 15P1200Nd drivers I use in some of my subs are rated for 1.2KW long-term, but have 3dB of power compression after 5 minutes of 700w pink noise.
Presumably, that's in free air, too, so once you've got it in a cabinet it's going to suffer even more.

Chris
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duane massey

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Re: Am I routing this correctly? Effectively?
« Reply #7 on: August 02, 2017, 06:25:00 pm »

Simple answer: No, don't do it. bridging an amp and driving a load of less than 4ohms is almost never a good idea. If you actually connected all of your subs to this amp in bridged mode you would be subjecting the amp to a 1ohm load. Bad idea.
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Duane Massey
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Sam Costa

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Re: Am I routing this correctly? Effectively?
« Reply #8 on: August 02, 2017, 07:10:01 pm »

Sam, when you bridge an amp you get more voltage out because both channels are essentially in series; what you do not get is greater current capability.

Chris Grimshaw's analysis is correct, and frankly I'd rather see you power them in stereo, 2 per channel.  You'll save on reconing that way.

The dirty little secret is that more large coil woofers go into power compression when sustained average power is surprisingly low (think low hundreds of Watts) after a relatively short time.  Applying more voltage only gets turned into heat, not more acoustic output.  Don't cook your voice coils.

Also, when you bridge an amp you pick up an additional 6dB of gain.  If you don't compensate for this you'll have a real big impression, "bridging the amp is MUCH more powerful", but it would be wrong.  The amp has the same current potential regardless of gain so when the gain is higher, it's louder, until you run out of current, which will happen sooner.  TANSTAAFL.  I suggest if you bridge an amp, go into your system processing and reduce it's pass band output level by -6dB and do it before you even think about turning the amp on.  Your system will respond as it did before.

If this were my rig I'd put 2 218 per channel on the PL4, keep the air vents clean, and beat it like a rented mule. YMMV.

ps. no mules were harmed in the making of hyperbole.  Honest. 8)

Good to know no Miles were harmed, thanks. ;)

So in essence, I am running it correctly for my setup.
Thank you gents.
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Re: Am I routing this correctly? Effectively?
« Reply #8 on: August 02, 2017, 07:10:01 pm »


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