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Author Topic: Sub Question  (Read 1343 times)

Bob Burke

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Sub Question
« on: July 21, 2014, 06:15:12 am »

  Hello all. I'm thinking of adding a small powered sub (JBL EON518S) to our passive rig  which consists of 2 Yamaha S115V's,  a Soundcraft EFX8 and a QSC PLX1804. My question regards the output from the mixer. I can't find an answer in the mixer manual.

  Is the Aux 1 signal affected by the channel EQ's, or is it a flat signal? Should I run it Pre or Post? I want to run our backing tracks and the bass guitar (with a direct out from the bass amp) through the sub. Should I roll off the lows from the mains?

  Finally, what's the best way to hook the sub up? The JBL appears to have an internal crossover and a high pass. I've never used a sub, and don't want to mess it up!


Thanks,

Bob

dick rees

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Re: Sub Question
« Reply #1 on: July 21, 2014, 06:53:54 am »

  Hello all. I'm thinking of adding a small powered sub (JBL EON518S) to our passive rig  which consists of 2 Yamaha S115V's,  a Soundcraft EFX8 and a QSC PLX1804. My question regards the output from the mixer. I can't find an answer in the mixer manual.

  Is the Aux 1 signal affected by the channel EQ's, or is it a flat signal? Should I run it Pre or Post? I want to run our backing tracks and the bass guitar (with a direct out from the bass amp) through the sub. Should I roll off the lows from the mains?

  Finally, what's the best way to hook the sub up? The JBL appears to have an internal crossover and a high pass. I've never used a sub, and don't want to mess it up!


Thanks,

Bob

Use a cross-over to divide the frequencies between the subs and tops.  You can find usable analog units used for very little money. 
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Simon Hutson

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Re: Sub Question
« Reply #2 on: July 21, 2014, 07:08:19 am »

Hi Bob.

Personally, I'd keep things simple. Run the LR outputs from your Soundcraft EFX8 into the LR inputs of your JBL EON518S, then run the LR outputs of the JBL into the LR inputs of your QSC PLX1804 and hook up your Yamaha S115Vs as normal. Select the HPF setting on the JBL and turn up the level until you get the right balance between the tops and sub, keeping an eye on the "clip" light to make sure you are not overloading the sub. If things don't sound quite right, try changing the polarity switch on the JBL to see if it makes things sound better/worse.

Best regards, Simon

P.S. According to the schematic in the Soundcraft EFX user guide, Aux 1 is globally switchable for pre or post fader, but will always be affected by the channel EQ regardless of this setting.
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David Allred

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Re: Sub Question
« Reply #3 on: July 21, 2014, 07:52:13 am »

You are right, the manual is useless.  I thought I had a definitive answer, but the block diagram is a little unclear.  The mono vs stereo inputs are routed differently as well, so take that into account when you do my recommendation, as they may not be the same functionally.

Connect an amp / speaker to the Aux output and physically test what the fader and EQ do when they are adjusted.   

David
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David Allred

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Re: Sub Question
« Reply #4 on: July 21, 2014, 08:00:09 am »

Hi Bob.


P.S. According to the schematic in the Soundcraft EFX user guide, Aux 1 is globally switchable for pre or post fader, but will always be affected by the channel EQ regardless of this setting.

On the mono channels, there is definitely a before and after connection at the EQ, apparently... PK is a switch.  Perplexing... indeed.  Do a test.

David
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Simon Hutson

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Re: Sub Question
« Reply #5 on: July 21, 2014, 08:54:16 am »

On the mono channels, there is definitely a before and after connection at the EQ, apparently... PK is a switch.  Perplexing... indeed.  Do a test.

David

Hi David.

I think that's the Channel Peak LED which lights when the signal level approaches clipping at any of the three monitored points:
a) PRE-EQ
b) POST-EQ
c) POST-FADE

Both the pre and post aux 1 signals seem to come after the EQ.

Best regards, Simon
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Bob Burke

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Re: Sub Question
« Reply #6 on: July 21, 2014, 09:24:07 am »

Hi Bob.

Personally, I'd keep things simple. Run the LR outputs from your Soundcraft EFX8 into the LR inputs of your JBL EON518S, then run the LR outputs of the JBL into the LR inputs of your QSC PLX1804 and hook up your Yamaha S115Vs as normal. Select the HPF setting on the JBL and turn up the level until you get the right balance between the tops and sub, keeping an eye on the "clip" light to make sure you are not overloading the sub. If things don't sound quite right, try changing the polarity switch on the JBL to see if it makes things sound better/worse.

Best regards, Simon

P.S. According to the schematic in the Soundcraft EFX user guide, Aux 1 is globally switchable for pre or post fader, but will always be affected by the channel EQ regardless of this setting.





Thanks Simon.

David Allred

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Re: Sub Question
« Reply #7 on: July 21, 2014, 10:27:09 am »

Simon, Nice catch.  Why not label it "Peak"?  Pretty of room... and clear. 

I guess Soundcraft is assuming that operators would never use the strip EQs for feedback control or speaker tone control(undesirable as it may be).

david
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Simon Hutson

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Re: Sub Question
« Reply #8 on: July 21, 2014, 01:39:27 pm »

Thanks Simon.

No problem. Enjoy your new purchase.

Best regards, Simon.
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Bob Burke

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Re: Sub Question
« Reply #9 on: August 17, 2014, 08:06:55 am »

Sorry to resurrect this thread, but I'm confused about the specs JBL provides for this sub, particularly the frequency range(s).

(http://www.sweetwater.com/store/detail/EON518S/)


System Type: Self powered 18", bass-reflex design
Frequency Range (-10 dB): 36 Hz - 130 Hz
Frequency Response (3 dB): 42 Hz - 100 Hz

Crossover Frequency: 120 Hz (HPF switchable on outputs)
System Power Rating: 500 W continuous, 1000 W peak


  What is the difference between the -10 dB and the  +  3 dB rating? Does this sub produce down to 36 Hz or 42 Hz? I know that I should know, but I've forgotten half of what I did know already! ;D


Thanks.


Bob
« Last Edit: August 17, 2014, 08:16:48 am by Bob Burke »
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