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300w vs 500w head with 450w cab?

#21
Fireguy said:
Like Freight Train said clipping blows speakers probably 10 tiems more often than delivering too much "CLEAN" power to a speaker.

Clipping happens most often when the power supply can no longer deliver enough voltage to produce the given frequency at the given amplitude.

Again, this is most common in solid state amplifiers.
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Power delivered is power delivered, it doesnt matter if the signal is clean or clipped. What does happen is that when running a distorted signal, it covers up the farting sound your driver makes when it is reaching its mechanical limitations. Those limits are the same regardless of clipping or clean signal.
 
#22
GlennW said:
I have a 1x15 cab with a Emi K-Lite 3015, 450w @ 8 ohms.

I'm in the market for a light head, and am considering the Carvin BX500 and the GB Shuttle 9.0, 300w and 500w @ 8 ohms respectively.

I'm leaning hard towards the STL9.0, and the only thing making me hesitant is the 500w rating. I figure it'll be fine as long as it isn't too loud, and that with reasonable volume I wouldn't be pressing my luck on overloading the cab.

Any thoughts, experiences?
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To try and pull the thread back to the OP's original question....

Yes, either will work fine. Generally, a cab will start to make awful noises before you may be pushing it too hard. Power ratings are like what your buddies rate a girl on a scale of 1-10...I wouldn't quote it or take it as gospel, but it's a broad guideline that can give you an idea of the ballpark you will be in. Judging on the gear that you mentioned though, I think it will be fine.

IME 1x15's aren't bad, but the extra dispersion from more cone space (i.e. - another 1x15, a 2x15 cab, or perhaps a 4x10 or 8x10) will get you a bump in volume and more efficient dispersion of power. Don't quote me on this but I think that having more speakers means the wattage is dispersed to each speaker evenly if all is wired correctly. So if you have two 1x15 cabs and your head puts out 500w at 4 ohms, theoretically you'd be sending 250w to each 1x15 cab...less chance of it blowing? Either way, it will sound louder and look cooler with more speakers...but YMMV :cool:
 
#23
DANGER WILL ROBINSON!!! Misinformation on this thread has gone rampant. You've got people giving you advice that has no idea what clipping vs. distortion is. Anyone with the slightest amount of knowledge about power amps and speakers knows that a clipping amp presents the most danger to the speaker. I would highly suggest bailing out of this and look to google to find some expert advice, and not on some yay-hoo forum.
 
#24
VanillaThundah said:
So if you have two 1x15 cabs and your head puts out 500w at 4 ohms, theoretically you'd be sending 250w to each 1x15 cab...
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I thought about that too since I also have a 425-450w 3-way PA cab, but doubt if I'd ever use it for just bass.

The BX500 is 500w @ 2 and 4 ohms; the STL9.0 is 900w @ 4 ohms, so the two cabs with the STL wouldn't be increasing the safety margin by much.

I've been using the 1x15 with a 450w Peavey PA head without incident, but not real loud.
 
#25
Just to hammer one more nail in the coffin:

Clipping is NEVER the same as (or even similar to) DC, even when it it is a pure square wave--and in reality, amplifier clipping is almost never a square wave anyway. You'd have to push it to a theoretical extreme to even get close to a square wave. But again, even if you reached that theoretical extreme, it's still not DC.

People get this idea from looking at a picture of a square wave and seeing the flat tops of the waves, and in their minds those short segments of flat line look like the one long flat line that means DC. But the fact that the wave alternates from peak to peak, thousands of times per second, totally eliminates that idea from reality. The speaker cannot "get stuck" for 1/20000th of a second, and it cannot even move from one extreme of its in/out motion to the other end in that short of a time. So the mechanical failures that people ascribe to clipping are imaginary, based on a misunderstanding of a picture.
 
#26
I'll just say this: watch out for the speaker running out of excursion. Too many lows and a hard attack at too much volume can cause it. Turn it down some and it may be ok, or roll off some lows to tame it. If you hear a loud click it's probably happening.

I don't know enough to comment on the other stuff.
 
#27
Freight Train said:
DANGER WILL ROBINSON!!! Misinformation on this thread has gone rampant. You've got people giving you advice that has no idea what clipping vs. distortion is. Anyone with the slightest amount of knowledge about power amps and speakers knows that a clipping amp presents the most danger to the speaker. I would highly suggest bailing out of this and look to google to find some expert advice, and not on some yay-hoo forum.
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<Sigh> Will this never end. If this is a "yay-hoo" forum what are YOU doing here? Folk post on this forum who are experts in the field of audio engineering and make their livings using that expertise. What you are indeed doing is spreading the misinformation that you deem so dangerous.
 
#28
I would go with a 500w head over a 300w head as long as there’s a pre-amp control like GAIN, or in the Carvins case, DRIVE. By keeping the MASTER down and pushing the DRIVE up, you can get the overdriven sound of a less-powered amp (somewhat) at lower volumes.
With a 300w amp, you won’t have the advantage of additional clean volume at higher levels (or driving more speakers) so it’s better to have more power.
Keep in mind that you can buy both a Carvin BX500 and a BX250 for the price of some other amps. That way you can choose, plus you’ll always have a backup head. '
:bassist:
 
#30
GlennW said:
I thought about that too since I also have a 425-450w 3-way PA cab, but doubt if I'd ever use it for just bass.

The BX500 is 500w @ 2 and 4 ohms; the STL9.0 is 900w @ 4 ohms, so the two cabs with the STL wouldn't be increasing the safety margin by much.

I've been using the 1x15 with a 450w Peavey PA head without incident, but not real loud.
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Maaaann...that 3-way cab would be sick for either of those heads!!! :hyper:

I'll have to be honest (since most people razz on me for being such a fanboy), but I own the BX500 and it's a great amp IMO. I like GB amps as well, but the Carvin sounds great for a much lower price....and believe me, it's plenty loud with my cabs (Avatar neo 2x10 and Kasino 2x15s with Eminence legend speakers). The tube pre on the Carvin is good, it has a graphic EQ so it's like a 2-channel amp, onboard compressor, and sweepable mid-frequency knobs are all stuff that sold me on the Carvin. I'll see if I can dig up or make some demo videos for you, if it helps.


** Video on this page, in case you haven't seen it. I'll still shoot for an amateur demo soon, though!
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#31
Here's a good site to start with. It explains pretty clearly how a clipping amp presents a DC voltage to the speaker.
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And what I'm doing here BassmanPaul is trying to help by dispensing some actual knowledge. But I'm tired of fighting against the constant stream of b.s.
 
#34
wcriley said:
Didn't read your reference, but...
If an amp is presenting DC at its output, it needs to be immediately taken out of service and repaired.
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It has nothing to do with DC being present on the output of an amp. That's a power supply issue. Here's the deal - a music signal is constantly varying in amplitude. To oversimplify let's say it's changing levels at the rate of anywhere between 20 and 20,000 times per second. It is an ALTERNATING CURRENT. A.C. = Alternating Current. When a musical signal clips, the top of the waveform is chopped off, and the amp is putting out a CONSTANT voltage, which moves the speaker coil to one position and stops, and if it stays there too long it burns the voice coil. A CONSTANT voltage is a CONSTANT or DIRECT current. D.C. = Direct Current. Please check the link I posted, don't believe me.
Now please ask some of the experts here how a clipping amp does not present D.C. to the speaker.
 
#35
Freight Train said:
It has nothing to do with DC being present on the output of an amp. That's a power supply issue. Here's the deal - a music signal is constantly varying in amplitude. To oversimplify let's say it's changing levels at the rate of anywhere between 20 and 20,000 times per second. It is an ALTERNATING CURRENT. A.C. = Alternating Current. When a musical signal clips, the top of the waveform is chopped off, and the amp is putting out a CONSTANT voltage, which moves the speaker coil to one position and stops, and if it stays there too long it burns the voice coil. A CONSTANT voltage is a CONSTANT or DIRECT current. D.C. = Direct Current. Please check the link I posted, don't believe me.
Now please ask some of the experts here how a clipping amp does not present D.C. to the speaker.
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Can you please explain how that is any different than the signal presented to a speaker when using distortion?
 
#38
Freight Train said:
Because the square wave from a synth is still varying many times per second. It is not one constant voltage.
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So wait a minute....

Clipping is presenting the speaker with a square wave, that still is oscillating. If it wasnt moving then you wouldnt hear anything, the speaker would not be oscillating.

A distortion pedal does the same thing, it clips the edges of the signal to create a square wave.



What you believe to be the end of speakers is actually over excursion masked by the distortion of the speaker.
 
#39
Freight Train said:
It has nothing to do with DC being present on the output of an amp. That's a power supply issue. Here's the deal - a music signal is constantly varying in amplitude. To oversimplify let's say it's changing levels at the rate of anywhere between 20 and 20,000 times per second. It is an ALTERNATING CURRENT. A.C. = Alternating Current. When a musical signal clips, the top of the waveform is chopped off, and the amp is putting out a CONSTANT voltage, which moves the speaker coil to one position and stops, and if it stays there too long it burns the voice coil. A CONSTANT voltage is a CONSTANT or DIRECT current. D.C. = Direct Current. Please check the link I posted, don't believe me.
Now please ask some of the experts here how a clipping amp does not present D.C. to the speaker.
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#40
wcriley said:
No experience with the 3015, but I've pushed 3015LFs with enough power (power amp potential of 1600 watts) that, standing a few feet away, I couldn't hear the drummer.

I would expect the 3015 to be just as conservatively rated and robust in a properly designed cab.
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Glenn - I’m not going to argue with wcriley. Just be careful and if you hear the driver farting back down the volume and or bass EQ before you damage it.
 

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