Dangers of Under-powered Drivers? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 01-30-14, 05:10 PM Thread Starter
Shackster

Join Date: Dec 2013
Location: Zumbro Falls
Posts: 66
My System
Re: Dangers of Under-powered Drivers?

I am really enjoying this discussion. Thank you. I think I'm starting to get over my confusion. What I envisioned was comparing a smooth waveform to what you get when you take scissors and clip off the tops of the waves. In my mind it seemed obvious that the clipped wave would have less area by the amount you clipped off. Smoothness I get. I get that a clipped wave would be tough for a driver to follow. I get that if you ask a driver to do a lot of tough work, then it will quickly fail. I'm just not sure what area has to do with it. Smoothness is described mathematically as a derivative. A wave that is approximately square has large derivatives. The Fundamental Theorem of Calculus tells us that determining smoothness and area are inverse operations. Can you feel my pain? One way I see it has to do with what you can do with that pond after it's been in a polar vortex. Ice skaters interact with each other with grace and smoothness, much the way a driver interacts with a smooth wave. Hockey players are different. They are more like a driver meeting up with a square wave. They call you for clipping in football, do they in hockey?
I am pleased to be able to celebrate Chinese New Year tomorrow knowing Fed Ex has picked up my 600 W Stereo Integrity HT 18 D4 driver. I'm really hoping it's not the year of the hoarse.
Rubus is offline

Old 01-30-14, 05:16 PM
Shackster

Join Date: Dec 2011
Location: Calabasas, CA
Posts: 29
Re: Dangers of Under-powered Drivers?

Quote:
Rubus wrote: View Post
I am really enjoying this discussion. Thank you. I think I'm starting to get over my confusion. What I envisioned was comparing a smooth waveform to what you get when you take scissors and clip off the tops of the waves. In my mind it seemed obvious that the clipped wave would have less area by the amount you clipped off.
But you left out that you then push up that clipped waveform to the ceiling pulling up everything else with it. So the "duty cycle" is longer than a sine wave of the same peak voltage.
dboomere is offline
Old 01-30-14, 05:32 PM Thread Starter
Shackster

Join Date: Dec 2013
Location: Zumbro Falls
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Re: Dangers of Under-powered Drivers?

Why does the square waveform get pushed up?
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Old 01-30-14, 05:53 PM
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informel

Join Date: Jun 2011
Location: Boisbriand, Quebec Canada
Posts: 262
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Re: Dangers of Under-powered Drivers?

The only drivers that I blew because the amp was probably driven into clipping is the tweeter.
When your amp is driven too hard the output will looks like a square wave, a square wave has the original wave plus multiple waves that are a multiple of the original frequency. (i.e. a note at 60HZ, will also have content at 120Hz, 180Hz, 240Hz, etc). and tweeter cannot take as much power.

but if your amp is only driving your sub, you will never be able to blow your driver.
If I remember my math correctly a square wave a 1.41 time the power of a sinus (hey don't flame me on this, I've been out of college for 40 years).
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Old 01-30-14, 06:33 PM
Shackster

Join Date: Dec 2011
Location: Calabasas, CA
Posts: 29
Re: Dangers of Under-powered Drivers?

I was speaking metaphorically. With a pure sine wave the peak voltage would only touch the top rail of the power supply at one point. With a perfect square wave it would touch it for the entire period of the wave ( a long line).
dboomere is offline
Old 01-30-14, 06:35 PM
Shackster

Join Date: Dec 2011
Location: Calabasas, CA
Posts: 29
Re: Dangers of Under-powered Drivers?

Quote:
informel wrote: View Post
The only drivers that I blew because the amp was probably driven into clipping is the tweeter.
When your amp is driven too hard the output will looks like a square wave, a square wave has the original wave plus multiple waves that are a multiple of the original frequency. (i.e. a note at 60HZ, will also have content at 120Hz, 180Hz, 240Hz, etc). and tweeter cannot take as much power.

but if your amp is only driving your sub, you will never be able to blow your driver.
If I remember my math correctly a square wave a 1.41 time the power of a sinus (hey don't flame me on this, I've been out of college for 40 years).
Actually it doubles.

Last edited by dboomere; 01-31-14 at 01:38 PM. Reason: spelling
dboomere is offline
Old 01-31-14, 07:53 AM Thread Starter
Shackster

Join Date: Dec 2013
Location: Zumbro Falls
Posts: 66
My System
Re: Dangers of Under-powered Drivers?

The sine curve has an area of 2 over the first pi radians. (The integral of sin(x) is -cos(x), evaluated at the boundaries gives -cos(pi) + cos(0) = 2.) A square (rectangular) wave has an area of pi. Pi/2 is about 1.57. A square wave has about 1.57 times the area of a sine wave. As far as power is concerned I have no idea. The square root of two is about 1.41. That might show up in a power comparison calculation but I don't get the modeling.
I heard from Nick at Stereo Integrity today. "You can use a 100 watt amplifier on the woofer. Too little power never killed any speaker. "
Rubus
Rubus is offline
Old 01-31-14, 01:42 PM
Shackster

Join Date: Dec 2011
Location: Calabasas, CA
Posts: 29
Re: Dangers of Under-powered Drivers?

So a sine wave has a 3dB crest factor and a true square wave has none. It's just full on during the entire period. So when you look at it that way the sine wave has 1/2 the power. Of course with music as your source it's almost impossible to actually get perfect square waves although you will get clipping.

Speaker power ratings are usually based on shaped power over some period of time (usually at least 2 hours). So a few clips even at double power probably won't destroy them right away. Besides it probably will sound so awful that you just won't go there.
dboomere is offline

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