400 watts Rms

[Jase]

I'm looking to get a new head, the cab I have is 400 watts RMS, what does this mean and if I add another 400 watt RMS cab what type of power should the amp be able to put out?

Cheers,
Jase

Very slow at learning about amps, ohms, Rms and all other important stuff

[Phaedrus]

800w?

Any watt rating given in respect of a cab is related to its power capacity, not its output.

Two pieces of data are important here, both for an amp's output and a cab's capacity:

1. Power, usually listed as "watts" or "W" (whether listed as RMS, program, continuous, peak, average or anything else).

2. Impedence (or resistance), listed as "ohms". This is a number that relates the speaker's resistance to the power being offered to it by the amp.

Amps will be listed as (for example) 400w output @ 8 ohms or maybe 280w @ 4 ohms.

If you are trying to mate a new amp with a cab you already have, you need to know the impedence rating of that cab. If it's 4 ohm cab with a capacity of 400w, then any amp you consider shouldn't really put out more than that power at that rating.

This is all very dependant on how the power output of any amp you're considering was rated.

Our 4 ohm JBL PA subs are rated at 400w continuous, 800w program and 1600w peak. We power them with Yamaha P5000S amps which put out 700w at 4 ohms. JBL's recommended amp for these subs should put out about the same power as the speaker's "program" rating.

Try this:

[url="http://basschat.co.uk/index.php?showtopic=135"]http://basschat.co.uk/index.php?showtopic=135[/url]

And search for "ohms", "watts", "power" - any of these should yield threads that will help.

Others on here know more than me and will doubtless be on to help.


Mark

[Chopthebass]

Nicely explained, Mark.

[Jase]

The input impedance is 8 ohms, so is this right....if I had another cab at 8ohms 400 watts Rms would this then become 4 ohms?

Thanks for the info by the way.

[alexclaber]

Good explanation. One thing to correct:

[quote name='Phaedrus' post='55392' date='Sep 4 2007, 04:56 PM']If it's 4 ohm cab with a capacity of 400w, then any amp you consider shouldn't really put out more than that power at that rating.[/quote]

For a cab rated at 400W I'd recommend an amp of between 200W and 800W into that impedance. Less than 200W won't cause any problems, you just won't be able to play quite as loud before your amp runs out of power. More than 800W and your cab is unlikely to go any louder due to power compression and you run the risk of damage if you push it too hard.

The more power you put into a speaker, the more it distorts. Although this distortion is subtle during normal use, exceed the speaker's capabilities and the distortion hugely increases. This big increase in distortion (it often is termed 'farting') is a warning sign that if you continue to push the speaker this hard then damage may occur. Musical instrument and pro audio speakers are designed to give this warning distortion well before they suffer damage, unlike hi-fi speakers which die very quickly if you push them into distortion.

Alex

[bass_ferret]

[quote name='Jase' post='55493' date='Sep 4 2007, 07:36 PM']The input impedance is 8 ohms, so is this right....if I had another cab at 8ohms 400 watts Rms would this then become 4 ohms?

Thanks for the info by the way.[/quote]
Provided they were wired in parallel then yes. Read the sticky! Power handling and impedence are unrelated. Most cabs are 8 ohms whether they can handle 10 watts or 1000 watts, you just would not use an amp rated at 1000 watts into 8 ohms with a 10 watt cab unless you were doing it for kicks.

[Jase]

Cheers guys,

All this concern has come about from being offered regular work with a hard rock band, they're pretty loud and powerful, I normally use a Trace Elliot which is around 280 watts but I got totally blown away by the band, it's not so much the volume but the power, the Trace can't hack it. I need to find something that'll deliver either by just using the 400 watt cab or by adding another cab and finding the right amp.

[bass_ferret]

Dont forget that double the watts does not double volume - you need 10 times for that.

[gypsymoth]

let's try this again.

your cab & speakers don't "put out" watts, they put out volume. the more watts that are put into them, the more volume they put out ....until you get up around their maximum rating, when they will cease generatingf additional volume and start generating distortion. as noted previously, too much of this is a bad thing as the speakers can fail, which in turn can cause they amp to fail as well.

adding another cabinet will make you louder, as there are more speakers. a higher rated (max watts) will not make you louder - unless your prior amplifier didn't put out anywhere near the cabinets maximum rating, and the new one does.

solid state/transistor amps put out more power at lower ohms (see the back of the amp for lowest allowable load), while tube amps with impedance selectors put out pretty much the same watts regardless of ohms. (owners of antique fenders need not protest the general concept).

if you want to be louder, add speakers as they are generally cheaper than amps. if your 280 watts is peak, your rms is about half that, typically adequate, but many/most rock bass players prefer amps around 200 rms in tube amps, more for solid state. and, as previously mentioned, a second cab typically halves your impedance, so if you are using solid state, your power doubles when you add the cabinet - which was going to make you louder anyway.

pay attention to all labels/warnings/stickers/etc on your amps & cabs as they supercede any general info given here, especially while you are in the learning stages. it is best not to learn by quickly buying or destroying expensive stuff.

[MoJ]

[quote name='Jase' post='55505' date='Sep 4 2007, 07:59 PM']Cheers guys,

All this concern has come about from being offered regular work with a hard rock band, they're pretty loud and powerful, I normally use a Trace Elliot which is around 280 watts but I got totally blown away by the band, it's not so much the volume but the power, the Trace can't hack it. I need to find something that'll deliver either by just using the 400 watt cab or by adding another cab and finding the right amp.[/quote]

For my two pence worth, I had to use an old Trace head last week - an SMC 7 band (wouldnt know if thats pre-Gibson ie good or not) but I found it lacked in the bottom end quite a bit, especially for a 300 watt head. Not sure what people rave on about, but the AH500-7 (new Peavey owned) was better by ten fold. The SMC didnt cut it for me at all. Horses for coarses. Im sure others really like them...
Try a Peavey Tour 450. I borrowed one from work as a road test on Monday and it rocks! Tons of (mid) bottom with very little EQ and I could get the bite in my sound I like too, and my shop is doing them for £259. Might even be a bit less, I cant quite remember this time of the day (after Jaeger...) Honestly, I defy ANYONE to find an amp as good as this, new, for the same price!

Andy

[Phaedrus]

[quote name='alexclaber' post='55496' date='Sep 4 2007, 07:43 PM']Good explanation. One thing to correct:
For a cab rated at 400W I'd recommend an amp of between 200W and 800W into that impedance. Less than 200W won't cause any problems, you just won't be able to play quite as loud before your amp runs out of power. More than 800W and your cab is unlikely to go any louder due to power compression and you run the risk of damage if you push it too hard.[/quote]

Yep. I had intended my comments about our subs and amps to be a "but in the case of..." caviat, but Alex is on the money more or less in accordance with what JBL say. But if I interpret [url="http://www.prosoundweb.com/studyhall/jbl/lowpower.php"]this article[/url] correctly, underpowering a speaker can cause as much damage as overpowering it.



[quote name='gypsymoth' post='55636' date='Sep 4 2007, 11:11 PM']let's try this again.

your cab & speakers don't "put out" watts, they put out volume.[/quote]

Gypsymoth,

I just read back quickly over all the posts - I didn't see anyone say that speakers or cabs put out watts.

Maybe I'm being sensitive cos it's early and my car had a flat tyre yesterday and I had to borrow my dad's car today while my tyre is being repaired, and his car stinks of smoke, but I take "let's try this again" to be a little condescending and dismissive of everything posted prior to your post. Though I'm sure that wasn't your intent... Was it?

I use the term "put out" to describe what an amp does cos everyone else I know also does. And most people on any music forum also seem to understand it. Sorry if it confused you.

Bad or incorrect information on watts & impedence could easily lead to an expensive mistake, but AFAIK, no-one posted any dangerous advice or comment.

Mark

EDIT: BTW, MoJ - What cab did you try the Tour 450 with. I had been talking with my local shop about getting in a Tour 450 and a TVX410 4 ohm cab for me to try. Shame he said that if he got it in for me, I'd have to buy it. I'm more interested in a 2x10 combo now (playing my part in cutting down weight & van space and trying to lower on-stage volume), but the Tour 450 + TVX410 still niggles at me as a potentially good, versatile, robust rig.

Edited September 5, 2007 by Phaedrus

[Jase]

[quote name='gypsymoth' post='55636' date='Sep 4 2007, 11:11 PM']let's try this again.

your cab & speakers don't "put out" watts, they put out volume. the more watts that are put into them, the more volume they put out ....until you get up around their maximum rating, when they will cease generatingf additional volume and start generating distortion. as noted previously, too much of this is a bad thing as the speakers can fail, which in turn can cause they amp to fail as well.

adding another cabinet will make you louder, as there are more speakers. a higher rated (max watts) will not make you louder - unless your prior amplifier didn't put out anywhere near the cabinets maximum rating, and the new one does.

solid state/transistor amps put out more power at lower ohms (see the back of the amp for lowest allowable load), while tube amps with impedance selectors put out pretty much the same watts regardless of ohms. (owners of antique fenders need not protest the general concept).

if you want to be louder, add speakers as they are generally cheaper than amps. if your 280 watts is peak, your rms is about half that, typically adequate, but many/most rock bass players prefer amps around 200 rms in tube amps, more for solid state. and, as previously mentioned, a second cab typically halves your impedance, so if you are using solid state, your power doubles when you add the cabinet - which was going to make you louder anyway.

pay attention to all labels/warnings/stickers/etc on your amps & cabs as they supercede any general info given here, especially while you are in the learning stages. it is best not to learn by quickly buying or destroying expensive stuff.[/quote]


[quote name='MoJ' post='55686' date='Sep 5 2007, 02:03 AM']For my two pence worth, I had to use an old Trace head last week - an SMC 7 band (wouldnt know if thats pre-Gibson ie good or not) but I found it lacked in the bottom end quite a bit, especially for a 300 watt head. Not sure what people rave on about, but the AH500-7 (new Peavey owned) was better by ten fold. The SMC didnt cut it for me at all. Horses for coarses. Im sure others really like them...
Try a Peavey Tour 450. I borrowed one from work as a road test on Monday and it rocks! Tons of (mid) bottom with very little EQ and I could get the bite in my sound I like too, and my shop is doing them for £259. Might even be a bit less, I cant quite remember this time of the day (after Jaeger...) Honestly, I defy ANYONE to find an amp as good as this, new, for the same price!

Andy[/quote]
That seems to make sense to me Gypsymoth, so in theory another cab would be just fine?

MoJ, I used to have an old Peavy head the Centurian and that was great, no complaints what so ever. I might just look into the Tour 450.

Cheers guys

[bass_ferret]

Be fair to Gypsymoth this is probably frustration talking because it is all the sticky that a lot of time and effort was put into, with pictures and everything, so any idiont can read it and know all about watts and ohms but no bugger ever looks at it.

[gypsymoth]

just trying to reword much of what was previously written but seemed to leave the poster still confused - simply because ( I think) the poster was starting at zero and there is a lot that goes into this.

if others had first written exactly what I had written, chances are I'd have said "let's try this again" and written what the others had said. no reflection intended on anyone - not even the poster, as nobody is born knowing this stuff, and any one explanation - short of a multi chapter book - is going to leave stuff out.

[MoJ]

[quote name='Phaedrus' post='55730' date='Sep 5 2007, 09:13 AM']EDIT: BTW, MoJ - What cab did you try the Tour 450 with. I had been talking with my local shop about getting in a Tour 450 and a TVX410 4 ohm cab for me to try. Shame he said that if he got it in for me, I'd have to buy it. I'm more interested in a 2x10 combo now (playing my part in cutting down weight & van space and trying to lower on-stage volume), but the Tour 450 + TVX410 still niggles at me as a potentially good, versatile, robust rig.[/quote]

Hi Phaedrus,
I used the Tour 450 with my current cabs, which are a Trace Elliot 1028 (Peavey era 2 x 10) and an older Trace 1153T cab. The thing had awesome power through these. I mean, the EQ is powerful and it was uber loud. Barely got it past 11 o'clock (and we do play loud in rehearsal, no thanks to our deaf guitarist!). The Kosmos octaver is a bit rubbish, but then most things like this built into amps I usually find are, like the Ashdown one too. But, it's hardley gonna be a deal clintcher.
It does make me reconsider my current amp (Peavey Pro 500) because of the price, but I could get the same sound from that compared to the Tour 450, plus more, so it's not a problem.

I have tried the TVX410, when I borowed the Pro 500 to test, and it is a great sounding cab. Very loud and great bottom from a 4 x 10, but the weight puts me off. If you can bare the weight, Id definitly jump at a Tour 450/TVX410 setup. Thats going to sound awesome!

Hope that helps. If you get a chance to try a Tour 450 or 700 out (I think my shop is doing those for around £300) then you'll definitley want to buy one, but like all things, I would want to try before I buy.

Andy

[Jase]

I've been looking at the Tour 450 since MoJ mentioned it earlier, I'd have one I reckon going by my last Peavey experience, good price £259 in Nevada Music.

[gypsymoth]

btw, a spare tire is generally considered more convenient than a spare car, and those borrowing cars because they don't have a spare shouldn't be complaining about the smokey smell of daddy's rescue vehicle.

that WAS condescending

[Jase]

Right, so....if 280 watts RMS is just that, then what does it mean if it says 580 watts peak ?

[BOD2]

[quote name='Phaedrus' post='55730' date='Sep 5 2007, 09:13 AM']But if I interpret [url="http://www.prosoundweb.com/studyhall/jbl/lowpower.php"]this article[/url] correctly, underpowering a speaker can cause as much damage as overpowering it.[/quote]

Oh no !! don't bring this debate back

This has been discussed in depth earlier. The key issue to note for we bass players is the statement in the article "These harmonics can be particularly dangerous to high frequency drivers." This is not such an issue for bass amplifiers/cabinets.

However, the Guidelines at the bottom of the article are all very good advice - in particular "Do not drive the amplifier into clipping" and all of the advice above is sound.

[BOD2]

[quote name='Jase' post='56053' date='Sep 5 2007, 04:43 PM']Right, so....if 280 watts RMS is just that, then what does it mean if it says 580 watts peak ?[/quote]

RMS is effectively an "average" power across a wide range of frequencies which gives a good basis for comparison between different amps and speakers.

"Peak power" indicates transient power peaks, which can be sustained for very short bursts anmd may be frequency dependent. It's best to ignore "peak power" and "music power" and any other power ratings and stay with RMS as this gives the most standard indication of power rating.

[bass_ferret]

Read [url="http://basschat.co.uk/index.php?showtopic=3730"]this[/url]

[bass_ferret]

and [url="http://basschat.co.uk/index.php?showtopic=135"]this[/url]

[Jase]

Thanks Bod, Thanks Ferret

Learning all the time.

[Phaedrus]

[quote name='gypsymoth' post='56024' date='Sep 5 2007, 04:04 PM']btw, a spare tire is generally considered more convenient than a spare car, and those borrowing cars because they don't have a spare shouldn't be complaining about the smokey smell of daddy's rescue vehicle.

that WAS condescending [/quote]


I guess I have to take that on the chin.

What's really bad is that I don't even have a jack either. Flat spare and no jack. What a flake, eh?

Wasn't I lucky I got the flat just 1km from work?

Mark

[gypsymoth]

conveniently located auto problems are good carma - and should (as you noted) be veiwed as good luck, not bad