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Author Topic: Speaker Question  (Read 7369 times)

Bob Burke

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Re: Speaker Question
« Reply #10 on: July 08, 2014, 10:23:45 am »

  Thanks guys. Pardon my ignorance. I'm just trying to get as much performance out of my liitle system without blowing anything up. ;D

Alex Rigodanzo

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Re: Speaker Question
« Reply #11 on: July 08, 2014, 11:17:24 am »

I had the PR12's in my dj rig with that same amp.  550 watts each in stereo 8ohms (crossed to subs at 90hz).  I did drive them hard and had no issues at all.  I know others have poo-pooed these cabs, but for the price and light weight, I found they're sound more than acceptable.  I can see where using them for monitors might not engender the same love.  Playing mp3's for a room full of drunks doesn't usually demand the same sq as a musician's monitor rig.
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Brian Jojade

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Re: Speaker Question
« Reply #12 on: July 08, 2014, 11:20:08 am »

The 400 watt power rating is for the entire speaker.  However, the HF driver is rated at only 30 watts continuous.  Under normal circumstances, the average power for musical programming has most of the energy in the lower frequencies.  However, a quick high frequency feedback can deliver all of the amp's power to the HF driver.  It doesn't take much for the HF driver to blow when that happens. 

On the Peavey's, the protection circuit is usually a light bulb that begins to glow as the voltage increases.  This is in a sense creating compression of the HF energy and can be quite audible.  However, quick HF feedback will still blow the driver, and it's possible to blow the driver before the lamp goes in certain situations.
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Art Welter

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Re: Speaker Question
« Reply #13 on: July 08, 2014, 02:24:54 pm »



Bob,

  The guy plugged a 1/4" cable right into the speaker input on the back of the speaker, then contacted the tip of the other end to the sleeve with the 9V poles. I later learned that you can test woofers that way, but never tweeters. I don't think they were blown at all when I brought them in (to return them) - I think this idiot did that.

  I have them at the shop now.

  The power thing - those PR-12 are getting 800 watts at 4 ohms, daisy-chained. I'm asking if it's safe to run them at 1/2 the amp level (400 watts?).
Bob,

Running your amp at 1/2 level means you simply have more potential to clip your mixer and EQ, it does not limit the output power. 1/2 power is only a 3 dB reduction, start thinking in terms of dB and things will start making sense- it takes a 10 dB reduction (1/10th the power) to sound half as loud in the mid range where the HF driver operates.

The tweeter is protected by passive crossover which includes a capacitor which blocks DC battery current (and low frequency musical content), unless one flips the 9 volt over back and fourth, you won't even hear a "click" out of the tweeter assuming it or the protective light bulb are not blown.

A 9 volt battery (like you put in guitar pedals) used for a click test does not have enough current potential to blow out any PA compression driver, period. Even if it could deliver a full 9 volts (it can't) in to an 8 ohm load (9 x 9 =81/8), that would only be 10.1 watts.

Anyway, point the horns at your ears rather than your knees to avoid blowing the diaphragms or light bulbs after they are repaired  ;).

Seriously, the picture you posted recently showed your mic (and therefore ear) position at least 6 dB off axis from your monitors, which requires 4 times the power to be heard at the same level if they were pointed at your ears. It's pretty easy to burn stuff up when you can't hear it.

Art
« Last Edit: July 08, 2014, 02:36:14 pm by Art Welter »
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Bob Burke

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Re: Speaker Question
« Reply #14 on: July 09, 2014, 08:04:20 am »

Bob,

Running your amp at 1/2 level means you simply have more potential to clip your mixer and EQ, it does not limit the output power. 1/2 power is only a 3 dB reduction, start thinking in terms of dB and things will start making sense- it takes a 10 dB reduction (1/10th the power) to sound half as loud in the mid range where the HF driver operates.

The tweeter is protected by passive crossover which includes a capacitor which blocks DC battery current (and low frequency musical content), unless one flips the 9 volt over back and fourth, you won't even hear a "click" out of the tweeter assuming it or the protective light bulb are not blown.

A 9 volt battery (like you put in guitar pedals) used for a click test does not have enough current potential to blow out any PA compression driver, period. Even if it could deliver a full 9 volts (it can't) in to an 8 ohm load (9 x 9 =81/8), that would only be 10.1 watts.

Anyway, point the horns at your ears rather than your knees to avoid blowing the diaphragms or light bulbs after they are repaired  ;).

Seriously, the picture you posted recently showed your mic (and therefore ear) position at least 6 dB off axis from your monitors, which requires 4 times the power to be heard at the same level if they were pointed at your ears. It's pretty easy to burn stuff up when you can't hear it.

Art



  Thanks Art. I will be propping the monitors up next time. ;D

 I still can't get my head around the "Running your amp at 1/2 level means you simply have more potential to clip your mixer and EQ, it does not limit the output power." thingy.

  I'm so used to guitar amps, where the volume knob raises the level. So I should set my QSC higher to keep from clipping? I know this is common knowledge here and I'm being obtuse, but I just don't get it! >:(

Tim McCulloch

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Re: Speaker Question
« Reply #15 on: July 09, 2014, 08:22:11 am »



  Thanks Art. I will be propping the monitors up next time. ;D

 I still can't get my head around the "Running your amp at 1/2 level means you simply have more potential to clip your mixer and EQ, it does not limit the output power." thingy.

  I'm so used to guitar amps, where the volume knob raises the level. So I should set my QSC higher to keep from clipping? I know this is common knowledge here and I'm being obtuse, but I just don't get it! >:(
Bob, the input level control on a power amp is an attenuator.  When you turn it to the left, it increases the electrical resistance - the amp has the same output voltage potential, it will just take a hotter input signal to reach full output.

Guitar amps are different animals.  You have control over actual gain at multiple stages within the amp.  Power amps used in audio don't generally work that way.
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Scott Olewiler

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Re: Speaker Question
« Reply #16 on: July 09, 2014, 08:38:58 am »


Seriously, the picture you posted recently showed your mic (and therefore ear) position at least 6 dB off axis from your monitors, which requires 4 times the power to be heard at the same level if they were pointed at your ears. It's pretty easy to burn stuff up when you can't hear it.


Never underestimate the power of even just a few degrees change in angle. I recently worked with a very diminutive female fiddle player who stood a few feet back from a monitor designed to be very close who went from politely repeatedly asking for her monitor to be turned up because it was shooting right over her head to "screaming" for us to turn it down when I place a 1" roll of console tape under the audience side.
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Bob Burke

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Re: Speaker Question
« Reply #17 on: July 09, 2014, 08:40:20 am »

Thanks Tim. So, if my QSC is set at 12 O'clock (-10) it is putting out 1/2 of the rated power, regardless of the mixer output?


Bob Burke

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Re: Speaker Question
« Reply #18 on: July 09, 2014, 08:42:36 am »

Never underestimate the power of even just a few degrees change in angle. I recently worked with a very diminutive female fiddle player who stood a few feet back from a monitor designed to be very close who went from politely repeatedly asking for her monitor to be turned up because it was shooting right over her head to "screaming" for us to turn it down when I place a 1" roll of console tape under the audience side.



Wow. I had no idea. I never knew monitors were that directional!

David Parker

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Re: Speaker Question
« Reply #19 on: July 09, 2014, 08:43:47 am »



  Thanks Art. I will be propping the monitors up next time. ;D

 I still can't get my head around the "Running your amp at 1/2 level means you simply have more potential to clip your mixer and EQ, it does not limit the output power." thingy.

  I'm so used to guitar amps, where the volume knob raises the level. So I should set my QSC higher to keep from clipping? I know this is common knowledge here and I'm being obtuse, but I just don't get it! >:(

the setting on the volume knob on the amp has no affect on clipping. It is there to match the input of the amp with the output of whatever is driving the amp. The amp itself is at 100% at all times. If you turn the knob down on the amp, but turn the output up from the mixer, the music you hear remains the same. Just like if you were to turn your guitar amp down at the amp, but then turn the volume up on one of your pedals, the music is just as loud as before. A 1000 watt amps is a 1000 watt amp with the volume knob at 50% or at 100%. An amp can actually put out considerably more power than it's rating if you send it a hot enough signal(overdrive it), and that is where the danger is in tearing up speakers.
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Re: Speaker Question
« Reply #19 on: July 09, 2014, 08:43:47 am »


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