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Author Topic: 2 ohm loads on bottom end  (Read 30902 times)

Craig Hauber

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Re: 2 ohm loads on bottom end
« Reply #50 on: August 28, 2016, 07:41:23 PM »

I have never been a fan of 2 ohm loads, so close to a dead short. I have been reading and people say 2 ohms on a "modern" amp is ok. What i have is a QSC 4050HD, discontinued for the A model i think. QSC gives an output rating for 2 ohms, like 1600 watts per side. I want to use it on 4 ev mtl2b cabs (dual 18 manifold design for the youngsters). each cab is 4 ohms and i have been driving them with 4 BGW 620a mono amps ( no one has been able to id this mono model yet) and they do very well. I have 3 bgw amps x2 racks, 2 in use and a spare on each side, running on 240v. As i said they sound great but before i use the QSC i just want some feedback on using it at 2 ohms on a all day event. Next big thing i need the subs for is bluegrass and accustic stuff leading up to wide open rock for the closer at an outdoor festival. Is this 4050 modern enough for the task? I have access to another one( one serial # apart) for one channel per cab if this would be better. Thanks for any input!

The 4050 will do it all day long.  I've sinced switched to using 2 powerlight type amps to do exactly what you are.  (8 MTL2, 2 per side of each amp)  I have "old iron" BGW and crown as backup but haven't had to use them.

I've also "abused" a 4050 in a club install with clip level EDM into 4 dual-18's 5 nights/wk and never experienced any issues.  I did have good limiting and HPF running but the clip lights winked occasionally.

It helps if you run 4-cond speakon to each cab (as they were factory wired) and home-run each cabinet to the amp rack where the parallel connections occur -that way you're not trying to pump all that current down 1 pair. 
(Worst-case you jump 2 cabinets per home-run, but with the 4-pin wiring you're still only seeing 4-ohms per wire pair.)
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Craig Hauber
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Ivan Beaver

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Re: 2 ohm loads on bottom end
« Reply #51 on: August 28, 2016, 08:31:25 PM »


It helps if you run 4-cond speakon to each cab (as they were factory wired) and home-run each cabinet to the amp rack where the parallel connections occur -that way you're not trying to pump all that current down 1 pair. 
(Worst-case you jump 2 cabinets per home-run, but with the 4-pin wiring you're still only seeing 4-ohms per wire pair.)
Actually-smaller wire puts less of a load on an amp than larger wire.

The added SERIES resistance of the small wire raises the overall impedance that the amplifier "sees".

Amplifiers "like" a higher impedance.  Larger wires put an overall "lower" impedance load on the amp.

The larger wire is better for getting more power to the speaker (but only a very small percentage more), and helping to control the damping factor. Those are the reasons to use larger wire-NOT the amplifier trying to "push more current" down the wire.

Electricity simply "flows", and is not "pushed" by any device.
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Ivan Beaver
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Craig Hauber

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Re: 2 ohm loads on bottom end
« Reply #52 on: September 01, 2016, 08:42:46 PM »

Actually-smaller wire puts less of a load on an amp than larger wire.

The added SERIES resistance of the small wire raises the overall impedance that the amplifier "sees".

Amplifiers "like" a higher impedance.  Larger wires put an overall "lower" impedance load on the amp.

The larger wire is better for getting more power to the speaker (but only a very small percentage more), and helping to control the damping factor. Those are the reasons to use larger wire-NOT the amplifier trying to "push more current" down the wire.

Electricity simply "flows", and is not "pushed" by any device.

Of course I used the wrong terminology.  The amp is really just a modulated valve on the pressure line -and of course everybody knows electricity is pushed, pumped actually! -and driven by giant turbopumps -there's a couple at the dam near me -can't figure out what turns those pumps but they suck water out of the lake and converts it into electrons -takes about 63,000 Allis-Chalmers horsepower to make that happen too! 
-and boy oh boy all those violently compressed electrons really shake the whole building before they leave!
  ;)
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Craig Hauber
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Kevin Conlon

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Re: 2 ohm loads on bottom end
« Reply #53 on: September 01, 2016, 11:41:18 PM »

The 4050 will do it all day long.  I've sinced switched to using 2 powerlight type amps to do exactly what you are.  (8 MTL2, 2 per side of each amp)  I have "old iron" BGW and crown as backup but haven't had to use them.

I've also "abused" a 4050 in a club install with clip level EDM into 4 dual-18's 5 nights/wk and never experienced any issues.  I did have good limiting and HPF running but the clip lights winked occasionally.

It helps if you run 4-cond speakon to each cab (as they were factory wired) and home-run each cabinet to the amp rack where the parallel connections occur -that way you're not trying to pump all that current down 1 pair. 
(Worst-case you jump 2 cabinets per home-run, but with the 4-pin wiring you're still only seeing 4-ohms per wire pair.)
Cool that we are using the same stuff. I do parallel at the amps and when i use series i do it at the speakers. I must learn more about the interaction of the wire as Ivan mentions. Seems like smaller wire would have more negatives at higher voltage than larger wire. I stated in my OP that i am not a fan of low z amp loading, just looking for opinions. You all have given me lots to ponder, thank you. I will set my stuff up outdoors and do some testing, just to piss off the neighbors, not really a problem on my 90 ac. land, but some will hear it. Thank you all again for your insight.
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Kevin Conlon

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Re: 2 ohm loads on bottom end
« Reply #54 on: September 21, 2016, 11:45:55 PM »

Did not intend to bump this thread. I did a comparison with the BGW amps and the 4050 last monday and am selling the 4050 to the friend that has it's brother. He has more use for it than i do. The measured output was lower than expected and the sound was not as musical, for lack of a better verb. These mono 620's are not anything like the specs i have seen, beat the qsc on all loads. Thanks for all the advice on how not to run an amp, i knew most of it already, but got some great tips. thanks to all. Does anyone know anything about a bgw 620 mono amp? Probably not. I spoke with someone who had 36 schems on different versions of these and he has no idea about them. Just use them till they die and then move on? May not happen in my lifetime!! Thanks again for the input!   Kevin C.
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Jeff Bankston

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Re: 2 ohm loads on bottom end
« Reply #55 on: September 22, 2016, 02:47:22 AM »

Did not intend to bump this thread. I did a comparison with the BGW amps and the 4050 last monday and am selling the 4050 to the friend that has it's brother. He has more use for it than i do. The measured output was lower than expected and the sound was not as musical, for lack of a better verb. These mono 620's are not anything like the specs i have seen, beat the qsc on all loads. Thanks for all the advice on how not to run an amp, i knew most of it already, but got some great tips. thanks to all. Does anyone know anything about a bgw 620 mono amp? Probably not. I spoke with someone who had 36 schems on different versions of these and he has no idea about them. Just use them till they die and then move on? May not happen in my lifetime!! Thanks again for the input!   Kevin C.
If this 200 watt BGW thing beat a 4050 the 4050 has something wrong and needs fixin   http://www.hifiengine.com/manual_library/bgw/620.shtml
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Kevin Conlon

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Re: 2 ohm loads on bottom end
« Reply #56 on: September 22, 2016, 12:41:27 PM »

If this 200 watt BGW thing beat a 4050 the 4050 has something wrong and needs fixin   http://www.hifiengine.com/manual_library/bgw/620.shtml
I would tend to agree exept i think the only thing my amps have in common with the one in the link is the case, and it is even a bit different. That site is where my search for info on these started years ago. I had to drive the 4050 till the clip lights flickered, at 4 ohms to match the a weighted output at the speaker. I may be going about this all wrong, but i expected a higher spl and it was not there. The 4050 may have cold and need service but it was not beaking up or making any bad noises. The testing was not done with a live band, that may change things a great deal.
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Steve M Smith

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Re: 2 ohm loads on bottom end
« Reply #57 on: September 23, 2016, 03:05:43 AM »

CS800 still brings a nostalgic tear to the eye

I have a CS800 and a CS1000 which were in use a year ago.  Might use them again one day!


Steve.
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Ivan Beaver

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Re: 2 ohm loads on bottom end
« Reply #58 on: September 23, 2016, 07:25:02 AM »

I had to drive the 4050 till the clip lights flickered, at 4 ohms to match the a weighted output at the speaker.
Were you running the 4050 in bridge mode?

If so, ARE YOU SURE!!! You had channel B turned ALL THE WAY down?

Some QSCs produce nasty stuff when in bridge mode and channel B is not turned all the way down.

Also were the switches on the rear panel FULL ENGAGED-did you switch them to check?

I have had cases where they were "not quite engaged" and weird things (including clip lights coming on early) happen.
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Ivan Beaver
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Scott Carneval

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Re: 2 ohm loads on bottom end
« Reply #59 on: September 23, 2016, 08:25:11 AM »

Were you running the 4050 in bridge mode?

If so, ARE YOU SURE!!! You had channel B turned ALL THE WAY down?

Some QSCs produce nasty stuff when in bridge mode and channel B is not turned all the way down.

Also were the switches on the rear panel FULL ENGAGED-did you switch them to check?

I have had cases where they were "not quite engaged" and weird things (including clip lights coming on early) happen.


I had a case a few weeks ago where somebody had switched an Ashly KLR3200 into bridge mode, but left the two Martin Blackline subs wired in parallel. All they did was invert the polarity of one of the subs, and they wondered why it wasn't as loud as it used to be.


Sent from my iPhone using Tapatalk
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Re: 2 ohm loads on bottom end
« Reply #59 on: September 23, 2016, 08:25:11 AM »


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