Power handling: How much can a cab take?

[Kongo]

I'm looking to add a 2x10 on top of my 4x10 Trace Elliot cab but here's to problem I've found with many 2x10's...The power handling!
I am soon to be running 700 watts @ 4 ohms...Jacking the 4x10 and 2x10 to the back of the head, both being 8 ohms, will create 4 ohms and thus releasing the entire lot.

Now...every 2x10 I've seen has a power handling rating of 400 watts, regardless of how powerful the head is of that make you can buy.
So, 700 watts is 300 over the limit...Even Trace Elliot themselfs only go down to 600 watts with the new heads that drive this cab so I'm basically asking, how much can they REALLY take?
Obviously, the output and input WON'T be on max, more near half way (less with 2 cabs most prob) so the head won't be at max anyways.

It's still a question of whether I should or not and will be for gigs, not practise if I do. I'd rather my head run at 500 watts and run slightly cooler but used for gigging it'll be fine.
I'm sure someone here can help.

[escholl]

if the loads are equal, ie both cabs are 8 ohms, then the 700 watts will be split evenly between the two at 350 watts per cabinet.

[Mr. Foxen]

Go for a 16 ohm 2x10 so each speaker is getting the same juice, that way the 2x10 won't be breaking when your 4x10 is running at half power.

Or get 2 8x10s because it's [url="http://www.myspace.com/terrasolis"]Doom[/url].

Edited June 17, 2009 by Mr. Foxen

[JTUK]

Be conservative with your ratings...IMV

I'll run a cab at half its rating as bass is very heavy work for speakers..I think the 16 ohm suggestion is a good idea.. altho accept that you'll be geting less than 700 potential into cabs run at 16 and 8


500 watts is a decent power wattage in anyones money IMV.... I'd say the guitarist is deaf

[Musicman20]

I used a Trace for years through a crappy old Peavey at about half way, on 8 ohms....so what...about 200W...maybe less? It was 400W rated at 4ohms....dead loud.

That was always enough...and we play stupid loud.

500W solid state will always be enough.

[alexclaber]

It's complicated.

Basically your speakers have two completely independent limitations. The first is the thermal limit which is the ability of the voice coil to dissipate heat. Bear in mind that a typical loudspeaker is only about 2% efficient, so if you put 500W into a voice coil then 490W of heat will come out of it. The second is the mechanical limit, or how far a speaker can move without damage.

Brief bursts of energy above your thermal limit will not cause a problem because it takes a small amount of time for the voice coil to heat up. So what matters is your average power, taking into account the varying power coming from your amp as you play (anything between zero watts when you're playing a rest and roughly twice the rated power when you hit a really loud note and take the amp right to its limits). If you're playing with little EQ, no compression and no distortion then you're unlikely to ever reach a cab's thermal limits, even with an amp rated at far more power output than a cab's power handling. The more compression or distortion you use, the greater the average power and the greater the risk of thermal damage. It's still rarely a problem though. What can be more of a killer is if you're also adding lots of bass boost, to get more bottom from a cab that doesn't naturally have much down there. This not only raises the the total power output (doubling it for every 3dB of bass boost) but it also raises the ratio of average to peak power (just as compression and distortion do).

The more common failure method for bass guitar drivers and direct radiating subwoofers is mechanical failure. There are a few reasons for this: Firstly it only takes one really loud low frequency peak to kill your speaker. Secondly, too many players assume that because it's a bass cab you can crank up the lows, turn up the volume and everything will be fine because their cab is rated at more than their head. And thirdly, too many players think they can now turn up to a gig with a smaller rig than their guitarist and it'll be fine. It might be, but only if you appreciate that it has limits!

Alex

[Kongo]

[quote name='JTUK' post='516840' date='Jun 17 2009, 08:15 PM']500 watts is a decent power wattage in anyones money IMV.... I'd say the guitarist is deaf[/quote]

This is my new head that should arrive soon.
My old head was 300 watts @ 4 ohms so about 150 - 180 watts 8 ohms...maybe less considering it's a cheap head.

[quote name='alexclaber' post='516909' date='Jun 17 2009, 09:14 PM']It's complicated.

Basically your speakers have two completely independent limitations. The first is the thermal limit which is the ability of the voice coil to dissipate heat. Bear in mind that a typical loudspeaker is only about 2% efficient, so if you put 500W into a voice coil then 490W of heat will come out of it. The second is the mechanical limit, or how far a speaker can move without damage.

Brief bursts of energy above your thermal limit will not cause a problem because it takes a small amount of time for the voice coil to heat up. So what matters is your average power, taking into account the varying power coming from your amp as you play (anything between zero watts when you're playing a rest and roughly twice the rated power when you hit a really loud note and take the amp right to its limits). If you're playing with little EQ, no compression and no distortion then you're unlikely to ever reach a cab's thermal limits, even with an amp rated at far more power output than a cab's power handling. The more compression or distortion you use, the greater the average power and the greater the risk of thermal damage. It's still rarely a problem though. What can be more of a killer is if you're also adding lots of bass boost, to get more bottom from a cab that doesn't naturally have much down there. This not only raises the the total power output (doubling it for every 3dB of bass boost) but it also raises the ratio of average to peak power (just as compression and distortion do).

The more common failure method for bass guitar drivers and direct radiating subwoofers is mechanical failure. There are a few reasons for this: Firstly it only takes one really loud low frequency peak to kill your speaker. Secondly, too many players assume that because it's a bass cab you can crank up the lows, turn up the volume and everything will be fine because their cab is rated at more than their head. And thirdly, too many players think they can now turn up to a gig with a smaller rig than their guitarist and it'll be fine. It might be, but only if you appreciate that it has limits!

Alex[/quote]

Just the man I was waiting to reply.
it's too late right now to take this in so I'll read again tomorrow.

Oh and +1 on the bass boost thing. LOL when I used whatever amps are at rehearsal it was always funny as they'd leave i set how it was and you'd see the volume cranked up WAY more than need be and the bass boosted to 11!!!
TBH I often leave the bass centre...More volume seems to produce more bass anyways and as a tutor once said to be "It's a bass guitar, it's already bassey enough!".
I'm alwasy concious of what my cab is doing. Most of the time the speakers are only just moving so I don't get a read on how hard they are being pushed...That's through that SD800 again too!!!
But using 4x10's it;s never a good idea to boost the pure sub anyways, I treat the 40hz or 32hz slider as a cut option, not boost, it's just too low.
They deliver a lot of low end but are a smaller speaker...they ain't gonna like that low frequency so when I see it pushed at rehearsals it makes me laugh!

[Buzz]

[quote name='escholl' post='516799' date='Jun 17 2009, 07:35 PM']if the loads are equal, ie both cabs are 8 ohms, then the 700 watts will be split evenly between the two at 350 watts per cabinet.[/quote]

This is the answer for the op in regards to using the 2x10 and 4x10 together at the same time.

Although Alex comes in like the second coming of Christ just in a more engineering manner and spreads the truth via his teachings We should really erect a bunch of statues for him and the other experts like Dave Hall and Bill Fitzmaurice who grace these forums.

Edited June 18, 2009 by Buzz

[Mr. Foxen]

[quote name='Buzz' post='517075' date='Jun 18 2009, 01:28 AM']This is the answer for the op in regards to using the 2x10 and 4x10 together at the same time.

Although Alex comes in like the second coming of Christ just in a more engineering manner and spreads the truth via his teachings We should really erect a bunch of statues for him and the other experts like Dave Hall and Bill Fitzmaurice who grace these forums.[/quote]

#I think its important to note that the power is split evenly between the cabs, but the speakers in the 2x10 will be getting double (provided they are all the same impedance in both cabs, which I'm not sure you can do).

[alexclaber]

Yep, I'd try to find a 4 ohm 2x10" that contains two 8 ohm drivers wired in parallel. Then you can rewire it to series and get a 16 ohm load which will give equal power distribution between all the drivers in the 6x10" stack.

Alex

[Raggy]

I had a GK1001 head with a Markbass 4x10 and 2x10 playing in a loud band and never had a problem.

[Balcro]

[quote name='alexclaber' post='516909' date='Jun 17 2009, 09:14 PM']If you're playing with little EQ, no compression and no distortion then you're unlikely to ever reach a cab's thermal limits, even with an amp rated at far more power output than a cab's power handling. The more compression or distortion you use, the greater the average power and the greater the risk of thermal damage.
Alex[/quote]

Thanks for the explanation Alex.

Until I read this, I had assumed that distortion/effects were artificial, i.e simulated distortion/compression etc., rather like the development of tones on an organ or PC soundcard.

How does increasing distortion cause the physical damage?

Cheers,
Balcro.

[51m0n]

[quote name='Balcro' post='517282' date='Jun 18 2009, 11:56 AM']Thanks for the explanation Alex.

Until I read this, I had assumed that distortion/effects were artificial, i.e simulated distortion/compression etc., rather like the development of tones on an organ or PC soundcard.

How does increasing distortion cause the physical damage?

Cheers,
Balcro.[/quote]

Distortion like compression raises the average volume, it literally compresses the signal as well as distorting it because you are overloading the distortion by putting too much juice in to produce the distortion, this effectively results in a raising of the lowest signal level, and hence a raising of the average signal. That means more thermal energy to dissipate....

[alexclaber]

Exactly! However the upside of overdriven/distorted sounds is that they usually cut through the mix better due to having more midrange, which means you don't need as much power to get heard. Exceptions might be if the distorted sound you're using is too similar to your guitarist's sound, in which case it's quite easy for his sound to mask yours, hence you turn up more and more and release the magic smoke.

Also if you're going for dirtier sounds then you're less likely to hear the complaints from your speakers as they run into mechanical (over-excursion) problems. The only time I've managed to damage any bass guitar speakers was when running lots of effects through a single Acme Low-B2 - impossible to discern the over-excursion moans amongst all the synth and fuzz and octaver noises.

I used to regularly damage my old hi-fi speakers at Uni when turning them up too much at parties - I think the surrounds/spiders got pulled a bit out of shape due to over-excursion but I always found they recovered after being used more gently afterwards. Sadly high performance pro sound drivers are produced to much tighter tolerances than old hi-fi speakers (these were early 70s EMI ones) and so damage is more likely to be permanent.

Alex

[Mr. Foxen]

[quote name='alexclaber' post='517306' date='Jun 18 2009, 12:25 PM']Also if you're going for dirtier sounds then you're less likely to hear the complaints from your speakers as they run into mechanical (over-excursion) problems.[/quote]

This is the problem with the whole 'if it makes bad sounds, turn down' rule, I have my stuff make bad sounds all the time.

[Kongo]

[quote name='alexclaber' post='517306' date='Jun 18 2009, 12:25 PM']Exactly! However the upside of overdriven/distorted sounds is that they usually cut through the mix better due to having more midrange, which means you don't need as much power to get heard. Exceptions might be if the distorted sound you're using is too similar to your guitarist's sound, in which case it's quite easy for his sound to mask yours, hence you turn up more and more and release the magic smoke.

Also if you're going for dirtier sounds then you're less likely to hear the complaints from your speakers as they run into mechanical (over-excursion) problems. The only time I've managed to damage any bass guitar speakers was when running lots of effects through a single Acme Low-B2 - impossible to discern the over-excursion moans amongst all the synth and fuzz and octaver noises.

I used to regularly damage my old hi-fi speakers at Uni when turning them up too much at parties - I think the surrounds/spiders got pulled a bit out of shape due to over-excursion but I always found they recovered after being used more gently afterwards. Sadly high performance pro sound drivers are produced to much tighter tolerances than old hi-fi speakers (these were early 70s EMI ones) and so damage is more likely to be permanent.

Alex[/quote]

Not a distortion fan really, I love clean tone..."Liquid Steel" as I call it. As clear and bell like as a piano.
That's why until I found your cabs I avoided 15" cabs like the plague!

Compression is an interesting issue. As you bring the lower levels up and the higher levels down I guess you do increase volume without noticing.
But...if you have a compression output level does this still increase if you turned it down to the level where it's the same as if it was turned off?

[danlea]

[quote name='Kongo' post='517608' date='Jun 18 2009, 05:24 PM']...if you have a compression output level does this still increase if you turned it down to the level where it's the same as if it was turned off?[/quote]
Compression in it's most elementary sense does in fact [i]reduce the volume[/i] of louder sounds (those beyond the threshold level), but then of course you normally have auto-gain which brings everything back up, so on average it's louder. You can't actually say a compressed sound is the same level as the original, unless you're playing at a constant volume, in which case there's no need for a compressor in the first place!

[Kongo]

[quote name='danlea' post='517655' date='Jun 18 2009, 06:13 PM']Compression in it's most elementary sense does in fact [i]reduce the volume[/i] of louder sounds (those beyond the threshold level), but then of course you normally have auto-gain which brings everything back up, so on average it's louder. You can't actually say a compressed sound is the same level as the original, unless you're playing at a constant volume, in which case there's no need for a compressor in the first place![/quote]

And lets face it, not many bassists will be...Unless it's a slow walking blues line or something and even then, human error and free radical will make at least ONE not louder than the other...by how much is the question.

I use compression to bring my dynamics to a normal level...How they would be if my bass was accoustic.
Basically, ridding of the false dynamics loud, electrical amplifiers create making tapping sound ultra boomy and slapping take your ear off, rip your guts appart...or worse, make someone tell you to turn down, resulting in most of your set being unheard because you don't constantly slap.

When I turn compression on, the volume level usually drops.
It can be matched with the output level but most of the time it drops ever so slightly...this is why I got confused.

[Kongo]

Okie dokie...Now shall we say...What if the 400 watt cab was powered by a head running 500 watts @ 4 ohms?
Now it's only over 100 watts and said head is now the head that was built to power it in the first place.

Surely it's be ok now right? And remember, I'm not gonna have it turned to 11!

[alexclaber]

For the speakers in your 400W cab to total a 400W thermal rating that means they were powered by a 1600W amp for a number of hours, putting out a signal whose peak level was 1600W and average level was 400W. This is called a 6dB crest factor because 1600W is 6dB louder than 400W, and crest factor is the difference between peak and average level. For a speaker to be given a thermal rating of 100W it has to handle peaks of 400W and average power of 100W for a good few hours without overheating - that is the agreed standard.

You would have to be heavily compressing bass guitar (through compression or overdrive) to reduce the crest factor to as low as 6dB so your 500W amp is very very unlikely to overheat a 400W cab. If you crank up the lows stupidly you can still kill it through overexcursion but that requires pretty mindless folly.

I run a 2000W amp into my Big One, whose woofer is 'only' thermally rated at 450W. But I know it's near impossible to damage through over-excursion and I'm confident that even with an amp that can peak at well over 2000W the crest factor is never going to be low enough that the average power will sustain over 450W. If I was using it as a PA subwoofer and playing recorded music through it I would not use such a powerful amp - the heavy compression on recorded music means the crest factor is much lower and thus its much easier to overheat a speaker, though conversely it does mean you're much less likely to cause over-excursion.

Alex

[Kongo]

[quote name='alexclaber' post='518723' date='Jun 19 2009, 06:44 PM']For the speakers in your 400W cab to total a 400W thermal rating that means they were powered by a 1600W amp for a number of hours, putting out a signal whose peak level was 1600W and average level was 400W. This is called a 6dB crest factor because 1600W is 6dB louder than 400W, and crest factor is the difference between peak and average level. For a speaker to be given a thermal rating of 100W it has to handle peaks of 400W and average power of 100W for a good few hours without overheating - that is the agreed standard.

You would have to be heavily compressing bass guitar (through compression or overdrive) to reduce the crest factor to as low as 6dB so your 500W amp is very very unlikely to overheat a 400W cab. If you crank up the lows stupidly you can still kill it through overexcursion but that requires pretty mindless folly.

I run a 2000W amp into my Big One, whose woofer is 'only' thermally rated at 450W. But I know it's near impossible to damage through over-excursion and I'm confident that even with an amp that can peak at well over 2000W the crest factor is never going to be low enough that the average power will sustain over 450W. If I was using it as a PA subwoofer and playing recorded music through it I would not use such a powerful amp - the heavy compression on recorded music means the crest factor is much lower and thus its much easier to overheat a speaker, though conversely it does mean you're much less likely to cause over-excursion.

Alex[/quote]

A pacient wait well paid off.

That's in interesting post that didn't go over my head this time!
Also explains why they pair up amps and cabs this way.
The head has built in compression / tube pre-amp for warmth / overdrive but I doubt it would go to the level of what you said.
And as I said before, I NEVER boost the lows to a silly degree...They are 10" for a start.
Most of the time I leave the bass flat.

The 12 band sliders have 30hz and 40hz right at the bottom and to me, they are frequencies used to tame a Low-B string and keep the speaker from farting on any string. I've seen people boost them before...I doubt the 4x10 would even react to boosted 30hz.
At very low volumes yeah, I've put a slight boost in 40hz on my old head to give it added warmth because it's not in it's sweet spot but never at volume.

Well I think the 500 watt is a good bet.
It's Trace Elliot as well so, makes sence I finally paired them up.
I'll be getting it VERY soon and the 2x10 will be a close 2nd to come now.

Edited June 19, 2009 by Kongo

[rodl2005]

All great info on here- thanx Alex & all others. Great to be able to get this info in a language I can understand.
Appreciate it!

[Bill Fitzmaurice]

[quote name='alexclaber' post='516909' date='Jun 17 2009, 04:14 PM']The more common failure method for bass guitar drivers and direct radiating subwoofers is mechanical failure.[/quote]
Most driver failures are electrical, ie., voice coil burn out. The primary reason is thermal power compression. Driver voice coils driven with more than 100 watts or so get very hot. When the wire of the voice coil gets hotter its resistance increases, reducing driver sensitivity, which reduces output, which the player more often than not will compensate for by turning up the amp. This further heats the voice coil, further reducing output, and this cycle continues until the voice coil heats enough to either burn out or for the adhesives holding it together to fail. Prevention of this syndrome is why it's a good idea to run twice the speaker power rating than amp power rating. This practice also better matches the amp output to the amount of power than the average speaker's excursion limits allow it to actually make use of. It's also one more nail in the coffin of the Myth of Underpowering.

[alexclaber]

I'd like to get some hard data on driver failures. I know the vast majority of Acme failures are not voice coil related despite the huge power often being used to drive them and I've heard from other talkbassers in the pro-sound world that >90% of failures are mechanical failure, not voice coil overheating.

If more bassists used highpass filters then that would skew damage away from over-excursion but with all these low B strings around and high thermal ratings I can't see the predominant failure mode on bass guitar cabs (not pro-sound tops or horn subs) being thermal.

Alex

[Mr. Foxen]

Nerd fight!

My primary source of driver failure is damp.