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Author Topic: Dialing powered sub in a 70v system  (Read 853 times)

Myles Lemansky

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Dialing powered sub in a 70v system
« on: November 13, 2022, 12:53:14 PM »

I have a 4000 sq/ft fitness studio with 25 ft ceilings at peak with the following equipment:

QSC CMX500VA amp
Shure SCM262 mixer
(6) JBL C67 pendant speaker
(2) JBL  C60 subwoofers
(2) Shure Fitness mics

The speakers are tapped for 70V.  I initially did not start with the C60s, but was looking for some thump.  The C60s more or less cleaned up overall sound vs providing any chest pounding thump.   I would not say I am unhappy with the system, but I was looking to gain a little of feel out of the bass.

I found a used  Harbinger V2218s for short and pulled the trigger.  Correct or not, I ran a TRS-XLR from the AUX output on the SCM262.  I just touch the level on the sub and it pumps.  Sounds/feels great to me, but probably not for the masses.  With a wide range of users of the system and clients, I do not want the bass to be offensive.

The Harbinger has a 0 and 180 phase option.  The crossover is a 90 or 120Hz option.  Are there any other options for adjustment or via connections that will allow me to get the most out of the JBL's and sub?

Thank you in advance.

Myles
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Mike Caldwell

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Re: Dialing powered sub in a 70v system
« Reply #1 on: November 13, 2022, 02:07:37 PM »

I think you more or less have it.
I would set the crossover at 90hz.

The phase option may make it sound better at one location and make it worse
at another, take your pick.

You must have plugged into the one of the main output jacks on the 262 mixer as the aux outs are RCA phono jacks, was only one main output jack in use.

You could use the cross over outputs on the sub to feed the QSC amp.

The C60 "subwoofers" were never going to give chest pounding thump but just add a little extra low end at best.

On the QSC amp the filter switch should be on and set to the 50hz position, for the main speakers, in a 70volt system it should be actually higher.

Did you just hook up the C60 speakers in line with the other speakers.

Myles Lemansky

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Re: Dialing powered sub in a 70v system
« Reply #2 on: November 13, 2022, 05:16:46 PM »

Mike,
thank you much for the quick response. 

Yes on the main jack, the line out RCA's are to the amp.

Will double check on the QSC filter switch and the 50hz, will that get more out of 67s?

Yes, I just hooked the C60s in line with other speakers.

The 262 has a bass gain adjustment.  Should I start with that all the way down, dial sub, then go back to the 262 for fine tune?
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Mike Caldwell

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Re: Dialing powered sub in a 70v system
« Reply #3 on: November 13, 2022, 10:12:19 PM »

The QSC High pass will/should help a little with the JBL67's, if driving then fairly hard they will sound a little cleaner, less transformer saturation and the small woofer is not working as hard.
The JBLC60's have a built in high pass to feed the other speakers in the system, you could put
three on each of the C60's.

I would look at using the crossover outputs on the sub to drive the amp.

At the least leave the bass on the mixer straight up or cut back to some, if you use the
subs crossover outputs then  leave it straight up and adjust the sub level as needed.

Are you running the amp in bridged mono and connecting the speaker lines to the two
red terminals on the amp?

Myles Lemansky

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Re: Dialing powered sub in a 70v system
« Reply #4 on: November 26, 2022, 01:30:29 PM »

Mike,
Sorry for delayed response.  Thank you for recommendations.

Switched the QSC to 50 hz, a definite improvement in clarity.

Feeding the C60s is going to take some time to re-wire. Should I run one wire from amp and split to the C60s. Not to question you, but JBL manual seems to favor 2 or 4 vs 1 or 3, non issue?

I am using crossover on sun to power amp, sun strong and clean. 

Yes, speaker lines in proper place in amp.

Thank you.
Myles
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Mike Caldwell

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Re: Dialing powered sub in a 70v system
« Reply #5 on: November 27, 2022, 11:27:23 AM »

Mike,
Sorry for delayed response.  Thank you for recommendations.

Switched the QSC to 50 hz, a definite improvement in clarity.

Feeding the C60s is going to take some time to re-wire. Should I run one wire from amp and split to the C60s. Not to question you, but JBL manual seems to favor 2 or 4 vs 1 or 3, non issue?

I am using crossover on sun to power amp, sun strong and clean. 

Yes, speaker lines in proper place in amp.

Thank you.
Myles

Yep they do need to be connected in even numbers, 2 or 4 and the extension speakers set to 8 ohms on the tap.

Myles Lemansky

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Re: Dialing powered sub in a 70v system
« Reply #6 on: January 30, 2023, 01:53:05 PM »

Mike,
Fully enjoying system after all recommendations thank you.

In speaking with JBL they recommended in order to get optimal performance out of c60s was to run them on their own channel at 8ohm vs in chain.  My QSC can not power channel 2 at that level.   I managed to pick up a used Crown i800 and ran wire for the c60s to run independently on that amp. 

Problem I am having is I can only run one output from the Harbinger sun at a time.  Would it make sense to have to run 2 inputs into the sub in order to get 2 outputs and utilize sub crossover?

Edit: thinking this may be the answer:

https://www.fullcompass.com/prod/253192-technical-pro-xo3-3-way-crossover-with-subwoofer-out

« Last Edit: February 01, 2023, 07:22:57 AM by Myles Lemansky »
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David Morison

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Re: Dialing powered sub in a 70v system
« Reply #7 on: February 01, 2023, 08:22:28 AM »


Problem I am having is I can only run one output from the Harbinger sun at a time.  Would it make sense to have to run 2 inputs into the sub in order to get 2 outputs and utilize sub crossover?

A simple XLR Y-cable would allow you to use both channels of the main amp for the C60's, if that's what you're trying to do.

Edit - that's assuming it doesn't already have a switch to parallel the 2 inputs, many amps do.
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Myles Lemansky

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Re: Dialing powered sub in a 70v system
« Reply #8 on: Yesterday at 08:00:51 PM »

A simple XLR Y-cable would allow you to use both channels of the main amp for the C60's, if that's what you're trying to do.

Edit - that's assuming it doesn't already have a switch to parallel the 2 inputs, many amps do.

Thank you David.  Y would be great, but with qsc500 if running bridge 70v, according to spec, can not get anything out of channel 2.
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David Morison

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Re: Dialing powered sub in a 70v system
« Reply #9 on: Today at 03:50:28 AM »

Thank you David.  Y would be great, but with qsc500 if running bridge 70v, according to spec, can not get anything out of channel 2.

Ahh, sorry, didn't realise you had to be in bridge mode to get it to power 70V systems.
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Re: Dialing powered sub in a 70v system
« Reply #9 on: Today at 03:50:28 AM »


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