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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Randall Cook on May 27, 2014, 06:04:08 PM

Title: Which amp for subs? FP14000?
Post by: Randall Cook on May 27, 2014, 06:04:08 PM
I'm currently running 2-4 QW218 depending on event. I use a single PL380 to run them in both configurations of 2 or 4.  I want to get a different amp so I can use the PL380 for other purpose. I'm considering getting an fp14000 for subs, but I want to add two more subs for larger events for a total of six QW218.  If I get an fp14000 I won't have an amp for the third pair of subs.
My questions are:
What amp configuration would you recommend?  I do NOT want to run amps in bridge mode. Is there an amp I could get in addition to the fp14000 to run third set of subs?  Or what other amps configurations do you recommend?  Also, I'm not a fan of on-board digital processing.  I prefer higher quality amps, but I'm open for suggestions.  I currently use all PL3 series, so equal or better quality.
I guess the real question is: do I need to maintain watts, ohm, load ratios across all subs?  Or can the third set be run off a sub with different ratings as long as the subs are adequately powered?
Title: Re: Which amp for subs? FP14000?
Post by: Doug Fowler on May 27, 2014, 06:05:55 PM
If you don't mind switching brands:

http://www.speakerpower.net/rack-mount-models.html
Title: Re: Which amp for subs? FP14000?
Post by: Randall Cook on May 27, 2014, 06:26:04 PM
If you don't mind switching brands:

http://www.speakerpower.net/rack-mount-models.html

Doug,
I'm not familiar with that brand.  Could you elaborate on their build and quality?  Also, I don't see binding posts, not that it matters much I guess.  What configuration are you suggesting with these amps?  I also have to consider plugging into 20amp outlets in some venues. 
Title: Re: Which amp for subs? FP14000?
Post by: Geoff Doane on May 27, 2014, 08:41:22 PM
I guess the real question is: do I need to maintain watts, ohm, load ratios across all subs?  Or can the third set be run off a sub with different ratings as long as the subs are adequately powered?

If you're happy now with the QSC PL3 series, I would stick with them.  Having common models and even series allows you to swap things around for special jobs.

Nothing says you have to have the same load on each amp, or even on each amp channel.  If you have two PL380s running the subs, I would put 2 cabinets on the left side of the first amp, one on the right, one on the left side of the second amp, and then two on the remaining channel.  Each amp is equal (I know I said they didn't have to be), so if you have a 240V distro available, put one on each side to balance the electrical load.  Regardless of load on the amp, its gain (in dB) remains the same, so you don't have to change anything in your processing (I assume you have some sort of outboard DSP).  In theory, the channels loaded to 2Ω will limit first if the amp determines the limiting, but if the DSP determines the peak output, the channels should behave exactly the same.  In the unlikely event that you lose a channel, you can still run all 6 boxes off 3 channels of amplification.

GTD
Title: Re: Which amp for subs? FP14000?
Post by: Randall Cook on May 28, 2014, 11:31:28 AM
If you're happy now with the QSC PL3 series, I would stick with them.  Having common models and even series allows you to swap things around for special jobs.

Nothing says you have to have the same load on each amp, or even on each amp channel.  If you have two PL380s running the subs, I would put 2 cabinets on the left side of the first amp, one on the right, one on the left side of the second amp, and then two on the remaining channel.  Each amp is equal (I know I said they didn't have to be), so if you have a 240V distro available, put one on each side to balance the electrical load.  Regardless of load on the amp, its gain (in dB) remains the same, so you don't have to change anything in your processing (I assume you have some sort of outboard DSP).  In theory, the channels loaded to 2Ω will limit first if the amp determines the limiting, but if the DSP determines the peak output, the channels should behave exactly the same.  In the unlikely event that you lose a channel, you can still run all 6 boxes off 3 channels of amplification.

GTD

The QW218 is a double 18" - 4 ohm cabinet, so I can only run 2 cabinets off each side of the PL380.  They are a bit underpowered, but the configuration does handle most jobs.  Some jobs just need more rig for the gig I suppose.

Thanks for your replies.
Title: Re: Which amp for subs? FP14000?
Post by: Doug Fowler on May 28, 2014, 02:52:01 PM
Doug,
I'm not familiar with that brand.  Could you elaborate on their build and quality?  Also, I don't see binding posts, not that it matters much I guess.  What configuration are you suggesting with these amps?  I also have to consider plugging into 20amp outlets in some venues.

Paul Bell is using them and he's picky about these things.  Brian got started with plate amps for loudspeakers then moved to rack mount.  Danley Sound Labs is using these as OEM. I think BASSBOSS is using the plate models. 

Read up about the amps on the speakerpower web site. Brian did a comparison between brands, so read it in the proper context.  I just used them in Miami for EDM in March and was very pleased.  In one case, someone dropped a five second bass note and there was no sag.  They seem to be easy on the AC as well.

If I were buying sub amps today, I'm certain this is what I would choose, barring unknown problems.  I am not aware of any, though. 
Title: Re: Which amp for subs? FP14000?
Post by: Ivan Beaver on May 28, 2014, 06:02:04 PM
  I just used them in Miami for EDM in March and was very pleased.  In one case, someone dropped a five second bass note and there was no sag.  They seem to be easy on the AC as well.


And during a "miscommunication" on my part, the actual load on the sub amp was 4x 4 ohms cabinets per channel-so a 1 ohm load.  Kinda below the rated specs-but nobody knew any different-until now :)
Title: Re: Which amp for subs? FP14000?
Post by: Craig Hamilton on May 29, 2014, 12:02:12 AM
PK sound also uses the SpeakerPower plate amps in their tour grade subs.
Title: Re: Which amp for subs? FP14000?
Post by: Doug Fowler on May 29, 2014, 02:18:03 PM
And during a "miscommunication" on my part, the actual load on the sub amp was 4x 4 ohms cabinets per channel-so a 1 ohm load.  Kinda below the rated specs-but nobody knew any different-until now :)

I spoke to Paul Bell this morning in fact, and he tells me the amp will sustain max power for 4 seconds before it starts to sag.  So maybe it was a 4 second drop.  OTOH it was not anywhere near max output. But it was hella impressive, even more so with the crazy low nominal impedance. 

It was actually 3x 4 ohm subs per channel.  Two NL4s on the output panel, so I jumped two per stack.  Yeah, a bit of miscommunication but what a test of the amplifier.  Also, we were running 240v off the genset.  The meters barely moved.

For anyone using distro setups exclusively: if you're not running subs at 208v or 240v, you're missing out.

These speakerpower amps are badass.
Title: Re: Which amp for subs? FP14000?
Post by: TJ (Tom) Cornish on May 29, 2014, 05:02:22 PM
I spoke to Paul Bell this morning in fact, and he tells me the amp will sustain max power for 4 seconds before it starts to sag.  So maybe it was a 4 second drop.  OTOH it was not anywhere near max output. But it was hella impressive, even more so with the crazy low nominal impedance. 

It was actually 3x 4 ohm subs per channel.  Two NL4s on the output panel, so I jumped two per stack.  Yeah, a bit of miscommunication but what a test of the amplifier.  Also, we were running 240v off the genset.  The meters barely moved.

For anyone using distro setups exclusively: if you're not running subs at 208v or 240v, you're missing out.

These speakerpower amps are badass.
TH118 and SH96HO in blaze orange?
Title: Re: Which amp for subs? FP14000?
Post by: Doug Fowler on May 29, 2014, 05:06:16 PM
TH118 and SH96HO in blaze orange?

It's for the EDM crowd.  Prob wouldn't take those to a corporate gig :-)
Title: Re: Which amp for subs? FP14000?
Post by: Mark McFarlane on May 29, 2014, 06:20:23 PM
...Prob wouldn't take those to a corporate gig :-)

Unless its was a halloween party.
Title: Re: Which amp for subs? FP14000?
Post by: paul bell on May 29, 2014, 11:38:34 PM
Unless its was a halloween party.

EDM events ARE Halloween parties.
Title: Re: Which amp for subs? FP14000?
Post by: paul bell on May 29, 2014, 11:39:47 PM
And yeah, the SpeakerPower amps are pretty spankin.

I'm picky, eh? ;)
Title: Re: Which amp for subs? FP14000?
Post by: Ivan Beaver on May 30, 2014, 07:38:29 AM
EDM events ARE Halloween parties.
Last weekend was a testament to that.  Just like a halloween party-just without as many ghosts and skeletons-but there were some-------
Title: Re: Which amp for subs? FP14000?
Post by: Ivan Beaver on May 30, 2014, 07:43:11 AM
It's for the EDM crowd.  Prob wouldn't take those to a corporate gig :-)
It all depends on what somebody is "after".

I have had EDM guys tell me that there are only 2 colors speakers should be-Black and dark black.  They say it is all about the artist and the music.

And other guys who love wild looking/colored speakers saying that "the look" adds to the show..

So different people look for different things.

But I would agree for corporate shows-basic black would be best in most cases.  Unless it was for a "outgoing" type corp show.  Who knows?

Some people are into  "cool" and others want to hide everything.
Title: Re: Which amp for subs? FP14000?
Post by: Brian Oppegaard on May 30, 2014, 11:45:47 AM
I'm currently running 2-4 QW218 depending on event. I use a single PL380 to run them in both configurations of 2 or 4.  I want to get a different amp so I can use the PL380 for other purpose. I'm considering getting an fp14000 for subs, but I want to add two more subs for larger events for a total of six QW218.  If I get an fp14000 I won't have an amp for the third pair of subs.
My questions are:
What amp configuration would you recommend?  I do NOT want to run amps in bridge mode. Is there an amp I could get in addition to the fp14000 to run third set of subs?  Or what other amps configurations do you recommend?  Also, I'm not a fan of on-board digital processing.  I prefer higher quality amps, but I'm open for suggestions.  I currently use all PL3 series, so equal or better quality.
I guess the real question is: do I need to maintain watts, ohm, load ratios across all subs?  Or can the third set be run off a sub with different ratings as long as the subs are adequately powered?

PL380 is a good amp as you know and you could do worse than just picking up another 1 or 2 of those. Here is my advice to people:

What is the Load? Those QW218 are near the top in ability to handle power. The minimum impedance at 7.2 ohms is not too low to need to avoid paralleling them. The PL380 holds full power very well at 4 ohms, but only 80ms at 2 ohms. So you may be leaving some woofer capability unused when running 2 cabinets per side.

What is the Signal? If you are just reinforcing a Capella groups then most anything will do. But if EDM, special effects and synthesized bass are part of the mix, then you have to hold full power for a few seconds, not milliseconds or protection circuits in the amp will kick in and suck out the bass.

As others have said, most modern amps do not care if loads between the channels are matched or not. Interesting your comment about bridged amps because one case when it does matter is when you have a half bridge Class D amp that is loaded more on one channel and driven to high levels at very low frequencies you can get into a situation called power supply pumping. The back EMF from the sub can cause overvoltage of one polarity of the power supply. Modern amps detect this and protection circuits jump in to avoid blowing the outputs, but the result is a suck out of the bass right when you need it the most. The solution is to bridge the amp so that the back EMF is distributed equally to both power supply . I think 50-60ms hold time (2 cycles at 30Hz/40Hz) is the minimum hold time for rock music (thump thump thump) and 3-4 seconds for EDM (bwaaaaaaaahhhh). Steer clear of 20ms 1KHz power ratings for subs.

Brian Oppegaard
President at SpeakerPower
www.speakerpower.net
Title: Re: Which amp for subs? FP14000?
Post by: paul bell on May 30, 2014, 08:55:28 PM
Thanks Brian!
Title: Re: Which amp for subs? FP14000?
Post by: Randall Cook on June 05, 2014, 12:03:09 AM
PL380 is a good amp as you know and you could do worse than just picking up another 1 or 2 of those. Here is my advice to people:

What is the Load? Those QW218 are near the top in ability to handle power. The minimum impedance at 7.2 ohms is not too low to need to avoid paralleling them. The PL380 holds full power very well at 4 ohms, but only 80ms at 2 ohms. So you may be leaving some woofer capability unused when running 2 cabinets per side.

What is the Signal? If you are just reinforcing a Capella groups then most anything will do. But if EDM, special effects and synthesized bass are part of the mix, then you have to hold full power for a few seconds, not milliseconds or protection circuits in the amp will kick in and suck out the bass.

As others have said, most modern amps do not care if loads between the channels are matched or not. Interesting your comment about bridged amps because one case when it does matter is when you have a half bridge Class D amp that is loaded more on one channel and driven to high levels at very low frequencies you can get into a situation called power supply pumping. The back EMF from the sub can cause overvoltage of one polarity of the power supply. Modern amps detect this and protection circuits jump in to avoid blowing the outputs, but the result is a suck out of the bass right when you need it the most. The solution is to bridge the amp so that the back EMF is distributed equally to both power supply . I think 50-60ms hold time (2 cycles at 30Hz/40Hz) is the minimum hold time for rock music (thump thump thump) and 3-4 seconds for EDM (bwaaaaaaaahhhh). Steer clear of 20ms 1KHz power ratings for subs.

Brian Oppegaard
President at SpeakerPower
www.speakerpower.net

Awesome responses!  Thank you so much!  Working on a game plan now.  LOL!  Thanks!