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Author Topic: Underpowering Speakers  (Read 31130 times)

David A. Parker

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Re: Underpowering Speakers
« Reply #20 on: January 16, 2009, 03:42:34 pm »

the amp he referred to was 500 watts briged mono 8 ohms, which would work out to 125 watts 8 ohms in stereo mode. That was the problem, he would have to run the amp in stereo mode to get enough mixes. I'd say buy another amp and be done with it, amps are cheap these days.
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David Parker
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David A. Parker

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Re: Underpowering Speakers
« Reply #21 on: January 16, 2009, 03:49:20 pm »

I'm not an electrical engineer like JR, I'm just a sound guy, and I know that my job got a lot easier when I doubled the power on my monitor amps. I work a lot of one-0f-a-kind jobs, different bands, different venues, everything different, and when something makes a problem better ACROSS THE BOARD, I just enjoy it, don't try to analyze it, and share my success with others that might benefit. JR is the first guy with credentials to offer an explanation of why it worked that way for me. Everyone else said it couldn't have happened.
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David Parker
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Tom Reid

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Re: Underpowering Speakers
« Reply #22 on: January 16, 2009, 04:12:20 pm »

David A. Parker wrote on Fri, 16 January 2009 14:40

The passive crossovers wouldn't have been the reason, because they were the same in either case, same passive wedges. For whatever reason, I DID have less trouble with feedback after doubling my power. Also, when I got rid of the behringer eq's and replaced them with DBX there was a huge improvement in gain before feedback.


I over analyze things when they piss me off and I can't figure out why.

Yup, something inserted in the gain stage that is inadequate will mess up your whole day.

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Bob Lee (QSC)

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Re: Underpowering Speakers
« Reply #23 on: January 16, 2009, 06:01:32 pm »

Well, there's a lot of incorrect stuff there.
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Bob Lee
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Rob Timmerman

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Re: Underpowering Speakers
« Reply #24 on: January 16, 2009, 06:32:46 pm »

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David A. Parker

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Re: Underpowering Speakers
« Reply #25 on: January 16, 2009, 06:54:08 pm »

Art Welter wrote on Fri, 16 January 2009 14:27

David,

Feedback is caused by gain, the microphone hearing the speaker and reproducing it, not  “because an amp loses it's flat response as you push it harder”.

If you put a hard limiter on your monitors, you can cause them to feed back with under a watt, at a very low SPL, which can be useful for finding rings without blowing ears or drivers.

In the same fashion, if you don’t have enough power for your monitors to get loud enough, you may turn them up to increase the average level causing feedback, and the peaks will be clipped, a basic (nasty) form of limiting. The clipping will be heard more in the HF, where the clipped harmonics are more prevalent and your ears are more sensitive to distortion, the   “exaggerated frequencies” you mentioned.

With more power, the peaks are reproduced without clipping, so the monitor gets louder, the performers don’t have to sing (scream) as hard, until enough power is put in and thermal compression sets in...

Art Welter


All I know is that EVERYTHING with regards to monitors got better when I doubled the size of my amps. I went from Crown Microtech 1200's to QSC RMX 2450's. The crowns were top of the line amps and the QSC RMX are just average weekend warrior stuff, and the difference was night and day. I suspect that you get 3db increase in volume from doubling the power without adding any gain. How that works I don't know, and really don't care, because it works, and anyone with too small monitor amps and feedback problems can read what I did and learn from it. Quite often the waters get muddied with techno-jargon, when the original question isn't that complicated.
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David Parker
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Bob Lee (QSC)

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Re: Underpowering Speakers
« Reply #26 on: January 16, 2009, 07:10:33 pm »

  • There's no such thing as "underpowering" a loudspeaker.
  • The loudspeakers really don't care about the shape of the waveform. A square wave is not by itself a killer of tweeters, woofers, etc.
  • Well over 90% of the power put into a loudspeaker driver turns into heat, whether the waveform is square or not.
  • Overpowering (thermal damage from too much power) and overexcursion (excessive cone travel, typically from low frequency energy) are what damage loudspeakers.
  • When an amp clips, it puts out power in excess of its published ratings. Depending on the amp and the loudspeaker, that excessive amount of power may make a seemingly "safe" amp actually quite damaging.
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Bob Lee
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Brad Weber

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Re: Underpowering Speakers
« Reply #27 on: January 16, 2009, 07:22:26 pm »

A wonderful summary Bob, thanks!  A great post to reference when this same topic comes up again and again and again...
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Brad Weber
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Mike {AB} Butler

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Re: Underpowering Speakers
« Reply #28 on: January 16, 2009, 09:34:41 pm »

Jack Gunn wrote on Fri, 16 January 2009 01:41

Real simple, direct answer to your question:  Can you damage speakers by under powering them?  YES.  In fact, it is more likely and EASIER to cause damage by too small an amp, than by too large an amp.


Boy, this old saw dies hard! OK, so you're saying if a driver is rated at 100W Continuous (above the manufacturer's recommended minimum frequency), and you feed it 10 Watts of clipped amp signal, that will be enough to do it in? Not likely at all!
Jack Gunn wrote on Fri, 16 January 2009 01:41


You should never push your amp to the point it is right up to the peak light and then peaks.  Stay away from way up there.  Because if that read clip/peak light comes on, that means your tweeter is being sent a SQUARE wave.  That's no longer audio signal... That's tweeter death signal.


As far as the square wave being a "tweeter death signal", again, I take issue with this, as I have seen many a guitar and bass amp with supertweeters that survive for years. How can this be.. if they are sending overdriven signals to it? Simple.. it's not being overpowered! Sure, all drivers have a more limited lifespan in stressful conditions.. but reproducing a square wave isn't the issue.. overpowering the driver IS the issue..
Regards,
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Mike Butler,
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Sean Berry

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Re: Underpowering Speakers
« Reply #29 on: January 17, 2009, 11:54:32 am »

A lot of good stuff here,and some strange things as well.

Where should I start? You can fry a 100W speak with a 5W amp.

You can fry a 100W speak with a 1000W amp.

As someone said "gain structure" will do anything you want....Or don't want. If you clip the mic at the preamp stage of your mixer, you are SOL. Because, as we all know, once clipped, still clipped.

Just my $.02

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