• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Pushing a cabinet - Question

#21
Matt O said:
OP: I suggest again, get a cabinet, or two, that will handle that load or get a different head. I would rather play through a 300 watt head that I could push without fear than a 1000 watt head that I'm scared is going to fry my speakers.
Click to expand...

+1 to more speakers generally being a better way to get more volume than driving one cab with a bigger amp.

That said, an w/ all due respect, this approach to "matching" amp and cab ratings risks confusing TBers w/ the apples-&-oranges nature of those ratings. For reasons outlined above, it's perfectly possible to blow speakers in an 4 ohm cab rated for 300 watts RMS with an amp rated for 300 watts @ 4 ohms.

For starters, your amp will exceed its power rating if you hit it with a signal boosted over spec or push it past its specified THD rating. And in the real world, count on your speakers to hit their excursion limits well before thermal failure. (Bass especially tests excursion limits. Boost low end or kick on your bass synth pedal, and watch those speakers start jumping.)
 
#22
Simple answers.

Ryan Schmoll said:
Hopefully some of you can help clarify for me. I have a 1000-watt amp and one 4x10 cabinet that is rated for only 500. I keep asking the question about pushing the cab too hard but I get conflicting answers. Here are some of the answers I've received -
  • It's fine. You're already pushing 1000 watts regardless of your volume.
Click to expand...
No. You're almost certainly *not* pushing 1000 watts. In normal use, power output will vary as you play. Even in a loud stage rig with enough speakers to handle 1000 watts, you won't be driving a 1K watt power amp at 1000 watts except on occasional peaks. And if your rig has one 410 cab, it's *really* unlikely that your amp is regularly feeding 1000 watts into your cab. A few years ago I ran a 2000 watt power amp in my stage rig, but on most gigs I wouldn't have been surprised to find my moment-to-moment power closer to 100 watts than 1000.

Ryan Schmoll said:
  • You should be fine if you don't push the master volume too hard. (I keep it at halfway out of fear, currently).
Click to expand...
Half true. You should be fine, if you haven't blown speakers yet, you listen for signs of trouble, and you don't push the rig for so much volume that the speakers start compressing, farting out, or distorting. This is a matter of overall rig volume and eq, though, not simply the position of the master volume knob. Use a louder bass, or add a pedal with a gain stage, or eq for more bass, and you might need to bring down gain elsewhere if you're getting close to your cab's limits.

Ryan Schmoll said:
  • Be careful, you'll blow your speakers if you go past halfway. Add another cabinet.
Click to expand...
Half true. You can blow your speakers if you push your cab too hard. But the master volume knob isn't The One Magic Control, and keeping the power attenuator or volume knobs at half their travel doesn't guarantee your cab's health. Also, if your current rig is loud enough for the tone you want on your gigs, there's no need to add a second cab. If you need more volume, you can experiment with slowly increasing the rig's volume. If you start hearing signs that the cab is being taxed, then back off. If you need more than that, add another cab.
 
Last edited:
#23
The rule of thumb for any SS (solid sate) amp powering a cab is that the amp should produce 1.5 to 2.25x the program/RMS power of the cab to handle frequency and volume transients.

To answer the OP correctly - without knowing the cabs impedance (even tho' 8-ohm is fairly standard on a 4x10) - is not realistic.
Assuming a 500w 8-ohm 4x10 and an amp producing 1000w at 8-ohm, then the answer is STILL - it depends.
Is that 500w peak or program/RMS?? If the latter, then you can safely power it with an amp that produces from 750w to 1,125 watts. If the former, then you stand a REAL GOOD chance of blowing those speakers.

Keep in mind that LF drivers "eat" more "power" than their mid or HF cousins.
Also keep in mind that volume controls on your average amp are not volume controls.. they are attenuators. The amp can still deliver its rated 1000w when the "volume" level is at 5%... depending on the input signal levels to the power amp stage.

The impact of adding a 2nd cab (as suggested) will depend on type of cab added and it's nominal impedance. Assuming an identical cab and that 1000w was an 8-ohm rating, then two 4x10 5002 8-Ohm cabs in series would reduce the impedance at the amp to 4-ohms, and (assuming the amp can handle it) basically DOUBLE the output to 2000w - normal for a SS amp. Each cab would get half of the output - 1000w each.. so while it WILL be louder, you've not changed you amp/cab matching parameters, nor solved the OP's problem.

All that being said.. without the amp and cab models, one cannot correctly answer the OP's question.
 
#24
ddnidd1 said:
Yeah, but your 'Educated guess', could lead him to blowing up his cab. It doesn't take 1000 watts to fry his speakers - probably a LOT Less.

Could end up being the 'Typical' blown up cabinet.
Click to expand...
dude, relax!

you are correct, and i should have mentioned that; even at this theoretical 750 watts (or even less) he could cook his cab.

by the same token, i could bridge 3000 watts of crown power amp into that same cab and run it all day long without hurting anything, as long as i did it right and kept the levels safely low.

it is indeed all about listening to what's happening and not over-taxing the cab with excess lows (over-excursion) or excess long-term power (melting voice coils).
 
  • Like
Reactions: BrBss and SunnBass
#25
s0c9 said:
To answer the OP correctly - without knowing the cabs impedance (even tho' 8-ohm is fairly standard on a 4x10) - is not realistic.
Click to expand...
Luckily, it's not only realistic; it's easy. :thumbsup: The OP asked for someone to confirm what he should do, and he got that from (almost) all responses. He should stop approaching this as a math problem in which component ratings guarantee the cab's safety, and instead he should listen to his cab for signs of stress.
 
#26
EastCoastThump said:
Luckily, it's not only realistic; it's easy. :thumbsup: The OP asked for someone to confirm what he should do, and he got that from (almost) all responses. He should stop approaching this as a math problem in which component ratings guarantee the cab's safety, and instead he should listen to his cab for signs of stress.
Click to expand...
In many cases, I would agree. However, one cannot always prevent "letting the smoke out" by using ones ears.. sometimes it is simple math.
In the case of over-excursion.. generally yeah, one can hear it.. In the case of overdriving the amp and heating up the speakers coils before ejecting them out of the basket... generally not - until it's too late.
 
#27
s0c9 said:
In many cases, I would agree. However, one cannot always prevent "letting the smoke out" by using ones ears.. sometimes it is simple math.
In the case of over-excursion.. generally yeah, one can hear it.. In the case of overdriving the amp and heating up the speakers coils before ejecting them out of the basket... generally not - until it's too late.
Click to expand...
yeah, but i gotta think that an average 4x10 cab in a bar will get way more than loud enough with less than 500 watts pushing it; at that point he'd be blowing the cab from being Too Damn Loud, not from using the wrong head on it.
 
  • Like
Reactions: s0c9
#28
walterw said:
yeah, but i gotta think that an average 4x10 cab in a bar will get way more than loud enough with less than 500 watts pushing it; at that point he'd be blowing the cab from being Too Damn Loud, not from using the wrong head on it.
Click to expand...
Absolutely... 1000%.
Wish the OP had provided more details.. LOL
 
#29
EastCoastThump said:
That said, an w/ all due respect, this approach to "matching" amp and cab ratings risks confusing TBers w/ the apples-&-oranges nature of those ratings. For reasons outlined above, it's perfectly possible to blow speakers in an 4 ohm cab rated for 300 watts RMS with an amp rated for 300 watts @ 4 ohms.
Click to expand...

I agree, but..

His cab is rated at 500w. So, 300w at 4ohm into a 4 ohm 500w cab is way safer for the speakers than what he's doing now. Most likely his cab is 8 ohm so it would really be no problem for the speakers.

The impedance of his cab really doesn't matter in this case. If it's a 4 ohm cab he probably would have toasted it already running 1000w at 4ohms into a 500w cab. It's most likely an 8 ohm cab, which is still dangerous at a 500w rating, IMO.

So, maybe I should have said: IF your cab is 8ohms then add another 8ohm cab that can handle at least 500w and run that head like it was meant to be run - OR - replace your cab with one that has a higher rating - OR - What are you doing with a 1000w head in the first place?

Also, yes listen for stress in the cabinet, but in my experience, having blown a speaker or two in the past, I hear no stress right up to the point where I hear no bass anymore.
 
#32
ddnidd1 said:
Yeah, but your 'Educated guess', could lead him to blowing up his cab. It doesn't take 1000 watts to fry his speakers - probably a LOT Less.

Could end up being the 'Typical' blown up cabinet.
Click to expand...

I agree with Walter. While there are other variables to think of, in the end, its COMMON SENSE. Which sometimes doesnt seem to be too common anymore. If the speakers sound like they are being pushed too hard or are going to implode, they probably are and will! Its not that hard to figure out. You can play it safe all day and be paranoid about it or you can use your brain and ears to control the cabs volume level. If its not cutting it at practice and its not loud enough, maybe think about getting a different setup/rig.

Its great to know all the mathematics behind all this stuff, but again, as long as your impedances match up and youre using your brain and your ears, you should be fine.
 
Last edited:
#34
It's interesting that when sizing PA components the standard advice is to have twice as much power as your speakers can handle to avoid trying to get more volume and running the amp to clipping (which eats up speakers!). For example, from the Crown website ...

How much power can my speakers handle?
You can determine this by looking at the speaker's data sheet. Look for the Nominal Impedance spec. Typically it will be 2, 4, 8 or 16 ohms. Next, look for the loudspeaker specification called Continuous Power Handling or Continuous Power Rating. It might be called IEC rating or Power capacity.

If you can prevent the power amp from clipping (by using a limiter), use a power amp that supplies 2 to 4 times the speakers continuous power rating per channel. This allows 3 to 6 dB of headroom for peaks in the audio signal. Speakers are built to handle those short-term peaks. If you cant keep the power amp from clipping (say, you have no limiter and the system is overdriven or goes into feedback) the amplifier power should equal the speakers continuous power rating. That way the speaker wont be damaged if the amp clips by overdriving its input. In this case there is no headroom for peaks, so youll have to drive the speaker at less than its full rated power if you want to avoid distortion.

If you are mainly doing light dance music or voice, we recommend that the amplifier power be 1.6 times the Continuous Power rating per channel. If you are doing heavy metal/grunge, try 2.5 times the Continuous Power rating per channel. The amplifier power must be rated for the impedance of the loudspeaker (2, 4, 8 or 16 ohms).

Here's an example. Suppose the impedance of your speaker is 4 ohms, and its Continuous Power Handling is 100 W. If you are playing light dance music, the amplifier's 4-ohm power should be 1.6 x 100 W or 160 W continuous per channel. To handle heavy metal/grunge, the amplifier's 4-ohm power should be 2.5 x 100 W or 250 W continuous per channel.

If you use much more power, you are likely to damage the speaker by forcing the speaker cone to its limits. If you use much less power, youll probably turn up the amp until it clips, trying to make the speaker loud enough. Clipping can damage speakers due to overheating. So stay with 1.6 to 2.5 times the speaker's continuous power rating.
Click to expand...

http://www.crownaudio.com/how_much_power.htm
 
#36
I agree that using your ears will help tell you when your cabinets are struggling. But if you use distortion effects, it will be harder to do.

Regarding thermal failure vs. over excursion, in general, voice coil thermal capacity has improved significantly in the last few decades. I suspect that in the vast majority of cases, a bass cabinet will reach excursion limits well before the thermal limit of the voice coil.
 
#38
RustyAxe said:
Nah ... I suppose the people at Crown are ignorant of such things.
Click to expand...

This has been covered over and over again.

If "clipping" caused woofers to die, guitarists and bass players who use distortion would be replacing speakers every gig.

Recommend you do a search for posts on the subject by AgedHorse (Genz Benz/Mesa), Bob Lee (QSC), and Bill Fitzmaurice.

Clipping can cause your amp to put out MORE POWER then it is rated for - thus OVERPOWERING your speakers, but a clipped signal itself does not kill speakers.

ETA - It is also covered in the Amp sections FAQ's
 

Latest posts

Top Bottom
Back