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Author Topic: amp loading question  (Read 2150 times)

Mike Lolas

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amp loading question
« on: April 15, 2006, 05:05:02 pm »

Is there any problem if i use the one chanel of an amp for subwoofer loading and the second for fullrange?
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Chuck Safrit

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Re: amp loading question
« Reply #1 on: April 15, 2006, 05:25:35 pm »

Yes.

Check out here and here first.

Then go here
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Chuck
Safrit Sound
Now located in Asheboro, NC. Freelance mixing and event planing. Convenient to Greensboro and triad area.
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Mike Lolas

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Re: amp loading question
« Reply #2 on: April 15, 2006, 05:31:32 pm »

I am very sory. I will change to my real name straightaway.
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Chuck Safrit

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Re: amp loading question
« Reply #3 on: April 15, 2006, 06:40:06 pm »

basically the yes still applies as in that it is bad to do it that way. not for the amp but for sound quality.

If you are using subs and tops it is best to have either a passive or active crossover somewhere so that both speakers aren't trying to reproduce the same frequencies. This will lead to that nice muddy sound that nobody really likes to hear. If you were using an active crossover you can send one signal to one channel for the tops and the other channel for the subs.

Things like this are discussed often on here so PM me if you want some specifics on how to do this.
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Chuck
Safrit Sound
Now located in Asheboro, NC. Freelance mixing and event planing. Convenient to Greensboro and triad area.
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Steve Oldridge

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Re: amp loading question
« Reply #4 on: April 15, 2006, 07:08:36 pm »

Mike,
just to clarify... there is no reason that you can't load an amp with one side on subs and the other full range - as far as the amp is concerned. A modern stereo amp is basically two channels, that can be run independently (stereo) or together (bridged).
It should run with a 4-ohm load on one channel, with an 8-ohm load on the other. No problem.

Chuck's point was that you wouldn't want to run a sub and a full range speaker together (no matter how you power them). This leads to both the full range and sub duplicating lower frequencies which will make your sound muddy. If you have a crossover that splits the low freq. sound to the sub and everything else to the full range, then by all means power each off one channel of the same amp.

However, you will probably need the same configuration on both sides of the stage - whether running mono or stereo. If mono, you could get away with a [4 or 8 ohm] sub on one channel then run two 8-ohm full range speakers off the other. Just make sure you amps power output will run both of them and provide 1.8->2.25 times the RMS wattage of both speakers - since you'd be powering them off the same singel channel. i.e if your speakers are 200w RMS at 8-ohms, then 200*2 = 400w at 4-ohms. So your amp should be able to handle between 720 and 900w at 4 ohms per channel.

If stereo you will need a second amp, so you would [normally] run tops off one amp and the sub (or subs) off a second.

Steve
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Paul Opperman

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Re: amp loading question
« Reply #5 on: April 15, 2006, 07:29:59 pm »

Hi.
In the short term, it doesn't really matter how you load your amp channels, as long as you are within the specs.  However, over a long period of time, channels with different loads will physically wear out differently.  You should switch the loads between the channels to make sure both sides of your amp wear out at the same rate.  Others may have better suggestions for how frequently you should alternate, but I would say switch it up every few gigs just to be safe.

~Paul
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Paul Opperman

John Roberts {JR}

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Re: amp loading question
« Reply #6 on: April 15, 2006, 08:48:43 pm »

Paul Opperman wrote on Sat, 15 April 2006 18:29

Hi.
In the short term, it doesn't really matter how you load your amp channels, as long as you are within the specs.  However, over a long period of time, channels with different loads will physically wear out differently.  You should switch the loads between the channels to make sure both sides of your amp wear out at the same rate.  Others may have better suggestions for how frequently you should alternate, but I would say switch it up every few gigs just to be safe.

~Paul



I am not aware of a "physical" wear mechanism in power amps. There are aging or deterioration mechanisms associated with temperature but within normal temperature ranges the number of thermal cycles is a more powerful predictor of potential future failures than relative channel power utilization. In most cases heat stress will be on common elements like power supply components.

There will be a measurable difference in the maximum junction temperature of the harder driven channel's power devices but the impact of thermal cycling is not linear with temperature rise.

That said, over enough trials a stereo amp with both channels driving 4 Ohms "might" outlive the same amp driven with 8 ohms on one channel and 2.66 Ohms on the other, but I wouldn't hold my breath or bet any money on that outcome.    

There is a current x time mechanisms in very fine metalizations such as found in some very dense ICs but power devices are relatively large and more likely to be damaged by voltage spikes or abuse, not normal wear and tear.

JR
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