Power Feeder and Voltage Drop

[Chris Delcambre]

Hi Y'all,

I recently upgraded my 2 FOH ampracks to 3 Crown Itech6000, 1 Crown Itech8000, 1 Crown Itech9000HD each.
Yesterday we had an outside show and I did not see the performance out of the amps I expected. I was using 6 Peavey Versarray 112 Cabinets over 4 JBL SRX728 Subs a side.

Ohm reading on the amps is
Itech 6000 1: Ribbons (4 ohms) 2: Ribbons (8 ohms)
Itech 6000 1: Mids (4 ohms) 2: Mids (4 ohms)
Itech 6000 1: Mids (4 ohms) 2: Mids (Not Used. Its for the 2 boxes when we run 8 boxes a side)
Itech 8000 1: Subs (4 ohms) 2: Subs (4 ohms)
Itech 9000 1: Subs (4 ohms) 2: Subs (4 ohms)

My question is...

I was expecting to see some voltage drop as I have not upgraded my main power distro and rack packs to accomodate them. However I never once threw a breaker and the Voltage readings on the amps were 116-119 the entire night. Would I see an improvment by upgrading my power feeder. I have all intentions of doing this ASAP but I just want to know if this could be my problem with performance.

My current main distro feeder is 6/4 SOOW and my RackPack Feeders are 10/4.
My upgrade plan is to go to a 2/0 Banded Stage Cable Feeder with 6/4 RackPack Feeders and to upgrade my rackpacks to 50A 240V from the 30A 240V I have now.

Will this upgrade solve the amplifier performance problem I am having????

Thanks for any help you may be,
Chris Delcambre

 

[Gene Hardage]

Re: Power Feeder and Voltage Drop

Hi Y'all,

I recently upgraded my 2 FOH ampracks to 3 Crown Itech6000, 1 Crown Itech8000, 1 Crown Itech9000HD each.
Yesterday we had an outside show and I did not see the performance out of the amps I expected. I was using 6 Peavey Versarray 112 Cabinets over 4 JBL SRX728 Subs a side.

Ohm reading on the amps is
Itech 6000 1: Ribbons (4 ohms) 2: Ribbons (8 ohms)
Itech 6000 1: Mids (4 ohms) 2: Mids (4 ohms)
Itech 6000 1: Mids (4 ohms) 2: Mids (Not Used. Its for the 2 boxes when we run 8 boxes a side)
Itech 8000 1: Subs (4 ohms) 2: Subs (4 ohms)
Itech 9000 1: Subs (4 ohms) 2: Subs (4 ohms)

My question is...

I was expecting to see some voltage drop as I have not upgraded my main power distro and rack packs to accomodate them. However I never once threw a breaker and the Voltage readings on the amps were 116-119 the entire night. Would I see an improvment by upgrading my power feeder. I have all intentions of doing this ASAP but I just want to know if this could be my problem with performance.

My current main distro feeder is 6/4 SOOW and my RackPack Feeders are 10/4.
My upgrade plan is to go to a 2/0 Banded Stage Cable Feeder with 6/4 RackPack Feeders and to upgrade my rackpacks to 50A 240V from the 30A 240V I have now.

Will this upgrade solve the amplifier performance problem I am having????

Thanks for any help you may be,
Chris Delcambre

So how long is your 6/4 SOOW cable and what are you hooking it up to?
Generator?
50 amp range plug?
Direct connection with camlocks with your own 50 amp breaker?
If it's standard 240v power from a breaker panel - what gauge of wire feeds it and how long is that wire?
Sometimes you can have an iffy supply from the provider before you add your long feeder.
I'm not sharp enough to figure out your power needs for that rig but if you can afford the upgrade - bigger wire is always better.

 

[John Moore]

Re: Power Feeder and Voltage Drop

Look at the specs of your sub amps...at 1/3 power rating they are going to draw close to 30A in that mode...#6 has a power rating for transmission of about 40A and once you start adding length to the #6 , down you go (an we have not even addressed the other amps yet)...unless you have the subs on separate legs os a single phase distro with 2 hot legs...you are grossly under wired for what you are doing... 2/0 is going to get you almost 200A. Best thing to do is to get a current clamp meter and measure the load as you are doing an event...as we don't know how hard you are driving the amps...if even to 1/3 power...

Or....it may just not be enough rig for the gig...we had a PV rig and found that you need a sub for each pair of top boxes...so maybe adding another set of subs to get the low end you are looking for...we used similar 6 tops per side and the 112 boxes did well...the ribbons didn't project as far as we hoped...

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

Look at the specs of your sub amps...at 1/3 power rating they are going to draw close to 30A in that mode...#6 has a power rating for transmission of about 40A and once you start adding length to the #6 , down you go (an we have not even addressed the other amps yet)...unless you have the subs on separate legs os a single phase distro with 2 hot legs...you are grossly under wired for what you are doing... 2/0 is going to get you almost 200A. Best thing to do is to get a current clamp meter and measure the load as you are doing an event...as we don't know how hard you are driving the amps...if even to 1/3 power...

Or....it may just not be enough rig for the gig...we had a PV rig and found that you need a sub for each pair of top boxes...so maybe adding another set of subs to get the low end you are looking for...we used similar 6 tops per side and the 112 boxes did well...the ribbons didn't project as far as we hoped...

What I didnt understand about it was that I never tripped any breakers and the voltage never dropped severely and the amps were getting hit really hard...

I was tieing into an electrical panel on a 60A 240 with 2/0 feeding it.... Feeder is 90ft long so I was expecting to see some voltage drop but never did...

Chris

 

[John Moore]

Re: Power Feeder and Voltage Drop

See if you can get a ampacity clamp meter and actually measure during an event what the rig is drawing...once you find out...power may not be the issue at all..maybe something else...we have done events with our PV rig (sold now) in the past and thought the loads would be much higher and come to find out, was no where close to what we thought...and that was good !

 

[Silas Pradetto]

What aspect of performance was lacking?

Sent from my XT907 2

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

What aspect of performance was lacking?

Sent from my XT907 2

I would've expected more out of the entire rig however the main part was the subs... all amps were getting driven really hard; almost into clip and the ribbons were slightly into the 67V Peak Limiters on kick snare hits...
I had a Crest 5200 on the ribbons, a Crest 9200 on mids, and a Crest 9200 on the subs before and it doesnt seem like I had all that much more power with all the Itechs than I did with the Crests...
I disabled all the limiters on the Processor and am only using the limiters in the Itech so its not getting limited anywhere...

Chris

 

[Rob Timmerman]

Re: Power Feeder and Voltage Drop

I would've expected more out of the entire rig however the main part was the subs... all amps were getting driven really hard; almost into clip and the ribbons were slightly into the 67V Peak Limiters on kick snare hits...
I had a Crest 5200 on the ribbons, a Crest 9200 on mids, and a Crest 9200 on the subs before and it doesnt seem like I had all that much more power with all the Itechs than I did with the Crests...
I disabled all the limiters on the Processor and am only using the limiters in the Itech so its not getting limited anywhere...

Chris

An Itech 9000HD has ~2dB more output per channel than does a Crest 9200 when both are driven into a 4 ohm load. A 2dB difference is typically considered "barely audible", and can easily be eaten up by power compression in the drivers.

My guess is you simply didn't have enough rig for the gig.

 

[Art Welter]

Re: Power Feeder and Voltage Drop

I would've expected more out of the entire rig however the main part was the subs... all amps were getting driven really hard; almost into clip and the ribbons were slightly into the 67V Peak Limiters on kick snare hits...
I had a Crest 5200 on the ribbons, a Crest 9200 on mids, and a Crest 9200 on the subs before and it doesnt seem like I had all that much more power with all the Itechs than I did with the Crests...
I disabled all the limiters on the Processor and am only using the limiters in the Itech so its not getting limited anywhere...

Chris

Chris,

Voltage drop occurs rapidly on kick hits, a VOM may not register it. Plug a light into your amp rack power, if you notice it dims on kick/snare hits, your amps are starved on peaks.

If you look at the i-T6000 Current Draw, notice that although the average 1/8th power is 11.6 amps, divide 6000 watts by 65.7, the "watts out Per 1A line current" and the answer is 91.3 amps for each amplifier.
On the mids and highs, the amp's power supply capacitors can "smooth over" that peak draw, but the duration of a 40 Hz wavelength can be enough to need to pull that 80-90 amps for some portion of the peak.
Breakers can take as much as 10 times their rated ampacity before opening on peaks, as long as the average power is OK, they won't pop.

I have measured 6 dB less LF output in "brownout", and considering the 8000 and 9000 draw even more peak power than the i-T6000, it seems likely that the voltage was dropping a lot more than you measured.

 

[Raul Suarez]

Re: Power Feeder and Voltage Drop

Another issue in addition to the voltage drop is Latancy:
Crown IT8000: Analog: 1.13 mS.
Crown IT9000HD: 1.16 mS at 48 kHz, 529μS at 96 kHz
Which mode are you operating the 9000 in 48K or 96k?

Raul Suarez
Third Ear Sound

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

Another issue in addition to the voltage drop is Latancy:
Crown IT8000: Analog: 1.13 mS.
Crown IT9000HD: 1.16 mS at 48 kHz, 529μS at 96 kHz
Which mode are you operating the 9000 in 48K or 96k?

Raul Suarez
Third Ear Sound

96kHz... So I need to add .5ms delay to my 9000 so it lines up with the 8000... Correct? I was wondering how close they were on latency and you answered that... Thanks

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

An Itech 9000HD has ~2dB more output per channel than does a Crest 9200 when both are driven into a 4 ohm load. A 2dB difference is typically considered "barely audible", and can easily be eaten up by power compression in the drivers.

My guess is you simply didn't have enough rig for the gig.

I went from 2- 9200s at 2 ohms to 2-8000 at 4ohms and 2-9000 at 4ohms.

9200s at 2 ohms are 3250 which equals 13000w total
itechs at 4 ohms are equal to 31000w total

that's close to 2 1/2 times the power of crests.
if I have misinterpreted something or am not taking something into consideration please let me know...


Thanks,
Chris

 

[RYAN LOUDMUSIC JENKINS]

Re: Power Feeder and Voltage Drop

Uhmmmm, you want to upgrade to 2/0 banded....? I think you mean #2 banded. Home boy would never roll up 2/0 at the end of the night if it was banded.

So here is my take on it. You don't have an amplifier performance problem. You probably won't notice any difference in most situations by upgrading your distros and feeder cables unless you are constantly into the limiters.

What you will notice with more power is that your amps will be trotting along giving you the same performance that you would have been slamming your old amps to get.

I think you are more than likely experiencing some serious power compression and your rig is physically not capable of Irving you any more.

Somewhere here or on the other forums I started a thread about current draw. I measured my current draw on a fairly large EDM show and was totally surprised at how little current I was pulling even with massive bass notes. Amplifiers these days are so efficient that we just don't use nearly as much power as we think we do.

All that being said, I would definitely upgrade your power distribution, not for performance but for safety. More copper is safer, less chance of heating the jackets and melting down, etc.

 

[Brandon Blakeney]

Re: Power Feeder and Voltage Drop

Chris, I know that you are still using the VSX's for your crossover right? Is it that your subs can't keep up with your tops? When I had your rig I used 3 Versarray 218's per side under the 6 tops and it was PLENTY of low end. I have no experience with the Crown Power Amps you speak of.....we used a 2/4 125' feeder cable and all Crest 200 Power Amps. You should be hitting 113-115 C weighted at FOH around unity gain.

 

[Rob Timmerman]

Re: Power Feeder and Voltage Drop

I went from 2- 9200s at 2 ohms to 2-8000 at 4ohms and 2-9000 at 4ohms.

9200s at 2 ohms are 3250 which equals 13000w total
itechs at 4 ohms are equal to 31000w total

that's close to 2 1/2 times the power of crests.
if I have misinterpreted something or am not taking something into consideration please let me know...


Thanks,
Chris

That's what I get for assuming you did a 1 for 1 swap...

So you're at about a 4dB increase, not 2dB. Still in the realm of what isn't particuarly noticible, especially after power compression is taken into account.

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

Chris, I know that you are still using the VSX's for your crossover right? Is it that your subs can't keep up with your tops? When I had your rig I used 3 Versarray 218's per side under the 6 tops and it was PLENTY of low end. I have no experience with the Crown Power Amps you speak of.....we used a 2/4 125' feeder cable and all Crest 200 Power Amps. You should be hitting 113-115 C weighted at FOH around unity gain.

Yessir I am using the vsx for processing... At what distance was your FOH???

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

Uhmmmm, you want to upgrade to 2/0 banded....? I think you mean #2 banded. Home boy would never roll up 2/0 at the end of the night if it was banded.

So here is my take on it. You don't have an amplifier performance problem. You probably won't notice any difference in most situations by upgrading your distros and feeder cables unless you are constantly into the limiters.

What you will notice with more power is that your amps will be trotting along giving you the same performance that you would have been slamming your old amps to get.

I think you are more than likely experiencing some serious power compression and your rig is physically not capable of Irving you any more.

Somewhere here or on the other forums I started a thread about current draw. I measured my current draw on a fairly large EDM show and was totally surprised at how little current I was pulling even with massive bass notes. Amplifiers these days are so efficient that we just don't use nearly as much power as we think we do.

All that being said, I would definitely upgrade your power distribution, not for performance but for safety. More copper is safer, less chance of heating the jackets and melting down, etc.

Hi Ryan,

So are you saying 2/0 is too big for the application or its just too heavy too mess with... We generally have union hands so I'm not terribly worried about the weight however I am the performance... I want room for expansion as our next growth, hopefully next year will be 8-12 VT4888 over 6 JBL SRX728 a side... Along with the speaker growth will come more power amplifiers... Also need room to run some lighting...

thanks for your help and suggestions.
Chris

 

[Silas Pradetto]

Re: Power Feeder and Voltage Drop

Hi Ryan,

So are you saying 2/0 is too big for the application or its just too heavy too mess with... We generally have union hands so I'm not terribly worried about the weight however I am the performance... I want room for expansion as our next growth, hopefully next year will be 8-12 VT4888 over 6 JBL SRX728 a side... Along with the speaker growth will come more power amplifiers... Also need room to run some lighting...

thanks for your help and suggestions.
Chris

You should refer to NEC400 for ampacity of free-air feeder cable. Common sizes are:

#2 AWG 190 amps
#1 AWG 220 amps
#2/0 AWG 300 amps
#4/0 AWG 400 amps

I use #1

Especially consider that you CANNOT band feeder cable as it will require derating. Also know that 2/5 SOOW cord has WAY less current capacity than free-air #2 due to derating as well.

 

[Chris Delcambre]

Re: Power Feeder and Voltage Drop

You should refer to NEC400 for ampacity of free-air feeder cable. Common sizes are:

#2 AWG 190 amps
#1 AWG 220 amps
#2/0 AWG 300 amps
#4/0 AWG 400 amps

I use #1

Especially consider that you CANNOT band feeder cable as it will require derating. Also know that 2/5 SOOW cord has WAY less current capacity than free-air #2 due to derating as well.

Thanks Silas... Does that #1 run your vertec rig I see in your pictures and all your lighting or do you have a seperate light distro???

Chris

 

[Shane Presley]

Re: Power Feeder and Voltage Drop

Thanks Silas... Does that #1 run your vertec rig I see in your pictures and all your lighting or do you have a seperate light distro???

Chris

Chris, I only have #2 and I have 24-36k plus Lekos and sometimes run audio off the same run. Not usually a problem these days w led lighting and such... I don't use the pars that much anymore except for when I do television lighting, but so far so good. Hooked up to 200 amp with inspections, it's all good... Obviously the thicker you can afford the better, but at the time I thought 200 amps was all I would need... Thank god for led lighting my requirement has never passed 200