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Author Topic: What are your thoughts or experience running at 2 ohms?  (Read 4838 times)

Steve-White

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #10 on: August 19, 2021, 07:43:13 PM »


I have been running JBL SRX 728 bridged at 4 ohms for years and not 1 failure of amps or drivers.  That is why I wanted to start this discussion.  Why can I run the bridged at 4 ohms but others are saying stereo at 2 ohms is a no, no?

You can run them at 1 ohm (2 ohms bridged) if you like.  You asked for advisement and got it.  I will guarantee you if you push the amp at 2 ohms it won't live long and prosper.  2 ohm loads, as has already been stated, is something I would never do unless in a real bind, as has also already been stated, in which case the drive to the amp would be reduced and temperatures monitored closely.

Why have you been able to pull off a 4 ohm load on a bridged amp?  An educated guess is that you haven't been pushing it very hard.
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Luke Geis

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #11 on: August 19, 2021, 07:58:49 PM »

I will reiterate what has been said several times: As a design goal, running your system down to 2ohms is NOT prudent or in the best of interest. Running down to 2 ohm's is something to be done when there is nothing else left that you can do. It is very much a caveat emptor sort of thing when you do it purposefully. For a small, easy-going gig where there will be little stress on any part of the equipment, sure, but if you need any amount of real performance, I would highly suggest NOT going that way with your system design.
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Paul G. OBrien

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #12 on: August 19, 2021, 10:38:37 PM »


I have been running JBL SRX 728 bridged at 4 ohms for years and not 1 failure of amps or drivers.
What amps are you using this way? Some amps cannot handle this use at all, others can tolerate it but don't really excell at it, then there are amps that are designed for it. This mode of operation puts the heaviest electrical load and thermal stress on the amplifier and often performance at 2R is compromised in the name of keeping the amp functional. In numerous threads over the years it has been suggested and confirmed that using a bigger amp that can generate roughly the same power into a box at 4ohms/ch results in noticably tighter sound than using smaller bridged mono amps, and a side benefit is that the total AC electrical draw is reduced... significantly reduced (1/2 as much or less) if going from an old school class AB or class H amp to a class D.
« Last Edit: August 19, 2021, 10:41:34 PM by Paul G. OBrien »
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John Roberts {JR}

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #13 on: August 20, 2021, 12:08:14 AM »


I have been running JBL SRX 728 bridged at 4 ohms for years and not 1 failure of amps or drivers.  That is why I wanted to start this discussion.  Why can I run the bridged at 4 ohms but others are saying stereo at 2 ohms is a no, no?
MTBF

JR
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Brian Jojade

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #14 on: September 27, 2021, 09:53:25 PM »

When you look at the specs on the PLX amps, what you will notice is that as you get lower in ohms, to get to the rated power, your trade off is a MASSIVE increase in distortion.  The PLX 3602 is 1250 watts into 4 ohms at .1% distortion, but at 2 ohms, it's 1800 watts at a whopping 1% distortion.  So less power per speaker, way more distortion.  Also notice that their spec ONLY shows 1khz, not full band range.  That's telling that the full range has even less impressive numbers.

Running an amp at it's max load rating just means you're driving it harder. Well designed amps should be able to operate just fine, but like anything else, if you run it harder, it may not last quite as long.  But, with current equipment, the life of the gear is long enough even at high load that it may not really matter.

BUT, what does matter is if your amps are all running to their max load, that means there's no option to re-patch to account for the possibility that an amp fails.

1 amp running at 2 ohms dies, show over.  2 amps running at 4 ohms each and one dies, and you can patch together and get back to running with very little loss.
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Tim Weaver

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #15 on: September 28, 2021, 12:51:30 AM »

Have used rigs running PLX at 2ohm. When I convinced them to buy more amps jaws were dropping because the difference is not at all subtle.

All things being equal, if you insist on running amps at 2ohms the PLX is one of the worst possible choices to do it with. It just doesn't have the grunt to do it well.

iTech's and Macrotech-i's do 2ohm loads reasonably well. As do a number of other "D" amps out there that I don't have a lot of experience with. Unfortunately all the amps that do it well are also expensive.

So you have the choice. Buy the expensive amps and run at 2ohms per channel and have no backup plan, Or buy double the amount of PLX's and run at a happy 4ohms per channel, and if you have a failure you have the choice to run one or more amp at 2 ohm to get through the gig.
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Scott Holtzman

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #16 on: September 28, 2021, 03:26:21 AM »

Have used rigs running PLX at 2ohm. When I convinced them to buy more amps jaws were dropping because the difference is not at all subtle.

All things being equal, if you insist on running amps at 2ohms the PLX is one of the worst possible choices to do it with. It just doesn't have the grunt to do it well.

iTech's and Macrotech-i's do 2ohm loads reasonably well. As do a number of other "D" amps out there that I don't have a lot of experience with. Unfortunately all the amps that do it well are also expensive.

So you have the choice. Buy the expensive amps and run at 2ohms per channel and have no backup plan, Or buy double the amount of PLX's and run at a happy 4ohms per channel, and if you have a failure you have the choice to run one or more amp at 2 ohm to get through the gig.


PL2's do OK though.  I haven't tried PL3's.  I have PL236's running 4 ohms bridged (effectively 2 ohms) but I have 4 of them if I lose one the show goes on.  I am using them on STX828S's 
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Tim Weaver

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #17 on: September 28, 2021, 10:59:09 AM »


PL2's do OK though.  I haven't tried PL3's.  I have PL236's running 4 ohms bridged (effectively 2 ohms) but I have 4 of them if I lose one the show goes on.  I am using them on STX828S's

It's a Pro amp compared to a Pro-sumer amp though. Much better power supply and the cost new was quite a bit more. Maybe double? I don't know what either of them cost when new.....
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mike kunz

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Re: What are your thoughts or experience running at 2 ohms?
« Reply #18 on: October 17, 2021, 10:07:22 PM »

I have several QSC PLX2 3602 amps and I am considering a new speaker system that will require me to run them at 2 ohms per channel.  What are your thoughts or experience running at 2 ohms?

I have been running Subs at 2 ohms for many years with no issues . I had plx3402 for a while and now I have the Pl380 . They were powering EV MTL 4 .
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ProSoundWeb Community

Re: What are your thoughts or experience running at 2 ohms?
« Reply #18 on: October 17, 2021, 10:07:22 PM »


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