Head and cab wattage maths

[Phil Starr]

[quote name='karlfer' timestamp='1481886392' post='3195925']
This is beyond me. Most things are beyond me.

Am I to understand that a Markbass LM800, run with no effects, no compressor (I never use either) all EQ points noon, VLE/VLF (whatever they call them) off, that the maximum average ? I'm achieving is around 80 watts?
[/quote]

Depending upon the way you set up and play it could be even less. If each note fades to a quarter of it's initial volume that's half the volume on average which only takes 1/10th of the power, and then you have rests in your playing

[chris_b]

[quote name='karlfer' timestamp='1481886392' post='3195925']
I'm achieving is around 80 watts?
[/quote]

If you have good cabs (and enough of them) then you need fewer watts than you think.

[karlfer]

Well my flabber is certainly ghasted.
Never had a volume issue apart from a pretty crap TC BH800 and a Tone Hammer 500.
Ho hum.

[28mistertee]

So with the above in mind, is head wattage irrelevant as long as it isn't over the cab rating? Also lots of talk about tube heads with lower wattage are equivalent to SS of higher so with my cabs in mind would a 200w all valve be up to the job as easy as a non valve or hybrid 500w?

[Bill Fitzmaurice]

[quote name='28mistertee' timestamp='1481989881' post='3196820']
So with the above in mind, is head wattage irrelevant as long as it isn't over the cab rating?
[/quote]No, it's just plain irrelevant. You can blow a speaker using an amp rated at half the speaker rating, you can use an amp rated for ten times the speaker rating with no issues. There are too many variables involved to say that this amp goes well with that speaker.

[28mistertee]

[quote name='Bill Fitzmaurice' timestamp='1481991370' post='3196838']
No, it's just plain irrelevant. You can blow a speaker using an amp rated at half the speaker rating, you can use an amp rated for ten times the speaker rating with no issues. There are too many variables involved to say that this amp goes well with that speaker.
[/quote]
I spoke to our sound engineer last night and he said you're better off having a little bit more power and that speakers like to be driven a bit, amps that are too low in power can be running at full chat and cause clipping.

[chris_b]

Nothing sounds good for long if you're trying to run it flat out.

IMO your usual volume should be somewhere in the middle of the amps working power range and you should have enough speaker to manage the power you need with plenty of headroom. In my estimation, that's more watts in the speakers than you have in the amp. I used to put an 800 watt amp into a 1000 watt 410 and 700 watt 210. Both good quality cabs. The actual numbers didn't matter, I was pealing paint with the volume and I never came close to a bad sound or damaging my gear.

If you are trying to put on the performance of your life you don't want to be listening out at the same time for tell tale signs of speakers going over the limit and breaking up. If you're having to do this in the middle of a gig then you didn't do your homework properly at the planning stage.

I'm assuming if you're playing at a volume level that is threatening to break your gear then [i]that's[/i] the level you need to buy gear for. Turning down probably isn't an option in these cases. Get as technical as you like. . . . you bought the wrong gear.

[28mistertee]

[quote name='chris_b' timestamp='1482059718' post='3197236']
Nothing sounds good for long if you're trying to run it flat out.

IMO your usual volume should be somewhere in the middle of the amps working power range and you should have enough speaker to manage the power you need with plenty of headroom. In my estimation, that's more watts in the speakers than you have in the amp. I used to put an 800 watt amp into a 1000 watt 410 and 700 watt 210. Both good quality cabs. The actual numbers didn't matter, I was pealing paint with the volume and I never came close to a bad sound or damaging my gear.

If you are trying to put on the performance of your life you don't want to be listening out at the same time for tell tale signs of speakers going over the limit and breaking up. If you're having to do this in the middle of a gig then you didn't do your homework properly at the planning stage.

I'm assuming if you're playing at a volume level that is threatening to break your gear then [i]that's[/i] the level you need to buy gear for. Turning down probably isn't an option in these cases. Get as technical as you like. . . . you bought the wrong gear.
[/quote]
Volume is normally about half way, loads to go on head. Cabs are 500 and 400w respectively and are great sounding cabs. Just looking at a change from my SVT, miss the sound of my old vba400 so all valve is one direction, or try something different i.e. a 500w SS head with less knobs to twiddle 😉 Normal pub rock band volumes on stage, PA handles everything else.

[chris_b]

You have more options if there is FOH support involved.

I think we'd all like to know what you choose to replace an SVT. That's the gold standard for most genres.

[Guest bassman7755]

[quote name='28mistertee' timestamp='1481747340' post='3194875']
Probably been done to death but finding lots of conflicting advice on matching heads and cabs wattage wise especially with more than one cab.
I was always under the impression that your head had to be rated less than the cabs as not to overpower the speakers but I'm also reading that it's also possible to underpower them. Some also say as long as impedances match then all is cool?
In my case I run a 212 and a 210 cab which are 500 and 400 watts respectively so this would be a combined wattage of 900watts??
Head wise am i better off to run a 300, 500 or 1000watt? Apologies again for a novice question but i seem to be finding lots of conflicting advice.
Cheers ��
[/quote]

It doesn't matter if one is rated higher than the other so long as which ever is lowest rated is loud enough for you. In your case that much cabbage will have potential volume to spare so it then becomes a question of using an amp that's loud enough through those speakers. All other things being equal Id always err on the side of a more powerful amp because you can turn an overpowered amp down but you cant turn an under powered one up. In your case Id go for the 1000w again all other considerations begin equal and money no object. Of course things may not be equal - theres a lot more choice of bass amps around the 4-500w mark than pretty much any other rating and most of these would probably be plenty loud enough so if theres a 500w amp that you really like the tone of, dont be put off - at the end of the day 500w from a 500w amp is as loud as 500w from a 1000w amp running at half power (although the latter may sound better because its not running at its max rating).

Yeah there are some people who are OCD about not having an amp with more theoretical power than the cab rating but it makes no odds really so long as youve got the ability to use a volume control and not go crazy with low EQ boosts etc.

Edited December 18, 2016 by bassman7755

[28mistertee]

[quote name='chris_b' timestamp='1482069092' post='3197331']
You have more options if there is FOH support involved.

I think we'd all like to know what you choose to replace an SVT. That's the gold standard for most genres.
[/quote]
Me too, just didn't quite do it for me as I hoped it would 😉

[28mistertee]

[quote name='bassman7755' timestamp='1482074474' post='3197401']


It doesn't matter if one is rated higher than the other so long as which ever is lowest rated is loud enough for you. In your case that much cabbage will have potential volume to spare so it then becomes a question of using an amp that's loud enough through those speakers. All other things being equal Id always err on the side of a more powerful amp because you can turn an overpowered amp down but you cant turn an under powered one up. In your case Id go for the 1000w again all other considerations begin equal and money no object. Of course things may not be equal - theres a lot more choice of bass amps around the 4-500w mark than pretty much any other rating and most of these would probably be plenty loud enough so if theres a 500w amp that you really like the tone of, dont be put off - at the end of the day 500w from a 500w amp is as loud as 500w from a 1000w amp running at half power (although the latter may sound better because its not running at its max rating).

Yeah there are some people who are OCD about not having an amp with more theoretical power than the cab rating but it makes no odds really so long as youve got the ability to use a volume control and not go crazy with low EQ boosts etc.
[/quote]
Sound advice and backs up what our sound engineer said at the gig last night. Had trouble in the first set for one the guitarist had moved my mic right in front of the kick drum. Engineer told me to turn down as too much bottom in the sound. Half time, took some bass out, put the master back up and all was crystal clear 😊

[Jack]

I always think buying an amp based on the power rating is like buying a car on the same basis. Yes, in the broadest, most general sense a car that has more horsepower will probably go faster. Most of the time. Maybe. But there are just too many factors for it to really make any difference. A Caterham 7 is faster than a Range Rover, despite the much higher horsepower of the latter.


Similarly the power rating of an amp is probably a little bit important, but it doesn't really tell you a great deal about how loud the amp really is.

[Phil Starr]

First of all I like the car analogy for people who are not technical.Just as a more powerful engine will have a predictable effect fitted to the same car once you start changing speaker cabs the engine power becomes just one of many things you'd need to consider. Power isn't unimportant but you wouldn't start looking for a new car based only upon the horsepower of the engine.

It's also true that a lot of sound engineers like a little more power in their amps than speaker watts, I do myself. I don't in my bass cabs.

If I'm engineering sound I do so from the best seat in the house, I hear everything. Any clipping in the vocals sounds awful and there is almost no bass content in the voice. All my mic channels bar one are subject to filtering out the bass, I've also got metering on the output which I can see all the time, limiters protecting the speakers and control over my dynamic range. What I want is lot's of clean output, I'm not going to run my system into distortion or blow my speakers so overhead is critical to me.

When I'm playing bass I've no control over the rest of the band and I may be forced into playing louder than I'd like. I can't hear my bass amp clearly in most venues because I am too close to the speakers and I'm not going to notice even quite high levels of distortion. I'm also concentrating on the drummer and the rest of the musicians in the band and my own playing. I'm putting out a lot of deep bass into the speakers so I'm pushing them into high excursion levels. What i need to know is that however hard i push the power up I can't overdo it. It makes more sense to me to know I can't destroy my speakers and have one less thing to distract me so I tend to have more handling ability than amp power. My set up can overpower the drums so I know I have the volume I need.

[28mistertee]

Very valid point, does anyone know the difference between solid state power and tube i.e. although 200w all tube is very loud I'd still be safe using say a 300w cab obviously if you don't pile a load of low end through your cab?

[Phil Starr]

There isn't any difference in valve watts and SS watts, but there is a difference in the way they are usually used.

When you play at 200W that means you are actually playing with peaks of 200W, that moment when your pick or fingers hit the string really hard on your loudest notes. Until you pick the next note the sound dies away and the next note might be one you want quieter. If it is half the volume that's 10dB down and actually only uses 10% of the power or 20W. Once that note has died down to half its volume its only using 2W! The average power of an amp flat out is only a few watts.

Let's imagine you are operating at a very loud average of 10W with peaks of 200W. You want to turn up just a tiny amount, which is 3dB. Conveniently that's double the power. You are asking for 20W average which both Valve and SS amps will be happy with. The trouble is that the peaks are now 400W. A 200W valve amp will still only give 200W and so it will distort the loudest bits. the thing is that it will do so in a way that sounds OK, Some people even love valve distortion and seek to make it by turning their amps right up. With a SS state amp the distortion is liked by almost no-one and sounds awful.

So, valve amps are often deliberately turned right up to get distortion and are louder because they are turned up with higher gain on average. They are also usually used with big old speakers which are more efficient.

So as far as protecting your speakers a 200W valve amp is no different from using a 200W SS amp, you'll probably just be turning it up louder to get some valvey distortion.

[karlfer]

Genuine question. Why are big old speakers more efficient?

[chris_b]

[quote name='karlfer' timestamp='1482309156' post='3199316']
Genuine question. Why are big old speakers more efficient?
[/quote]

Mine never were!

[Jack]

[quote name='karlfer' timestamp='1482309156' post='3199316']
Genuine question. Why are big old speakers more efficient?
[/quote]

They're not really. Speakers are the one analog holdout in an increasingly digital world and whilst they are getting marginally better they haven't had a revolution on anywhere near the scale of other parts of a signal chain. Neodymium helped, meaning magnets were stronger and therefore could be made lighter but really they're much of a muchness. In short, they are getting slightly more efficient not less, but really they're not moving a great deal.

I have a pet theory that older speakers seemed louder because we never expected big bass from them. So maybe they were more efficient in the upper registers at the expense on the boomy bass. I dunno.

[Bill Fitzmaurice]

[quote name='Jack' timestamp='1482319313' post='3199474']
I have a pet theory that older speakers seemed louder because we never expected big bass from them. So maybe they were more efficient in the upper registers at the expense on the boomy bass.
[/quote]Maximum driver sensitivity was realized in 1949, with the JBL D130. It was very bass shy, because its low Qts responsible for high sensitivity also chokes off bass response. At the other end of the scale are high Qts drivers, typically found today in cheap combos and entry level separates. They have high sensitivity in the midbass, so they subjectively can sound loud, but they also sound boomy. Most vintage drivers were high Qts.

[Dan Dare]

Could I pick your brains, Bill? What is your favourite all round 10" driver(s) for bass guitar use (in a suitable cab, properly driven, etc, of course)? Thanks. I appreciate this may be a bit of a naïve question, but would be interested in your thoughts. Thanks.

[Bill Fitzmaurice]

The Eminence Deltalite II 2510 is very well balanced.

[LukeFRC]

[quote name='Dan Dare' timestamp='1482357424' post='3199923']
Could I pick your brains, Bill? What is your favourite all round 10" driver(s) for bass guitar use (in a suitable cab, properly driven, etc, of course)? Thanks. I appreciate this may be a bit of a naïve question, but would be interested in your thoughts. Thanks.
[/quote] the answer to the question after this is either the Simplexx or the Jack. Bill will tell you the Jack is better, more efficient but you need to have a fw Q points on your amp to get the most out of it. Other people who built them will say that two is more than double better than one. Someone else will chime in about their barefaced 210 cab which they really rate. Someone will possibly meantion the handles barefaced used half a decade ago.... then you're wondering - is it any good for metal.
Which I don't know

[Phil Starr]

[quote name='karlfer' timestamp='1482309156' post='3199316']
Genuine question. Why are big old speakers more efficient?
[/quote]

Because they had to be. It was the primary design goal.

With old materials it was hard to get high power handling, even as late as 1970 he average 12" speaker often only handled 25-50W. Amplifiers were really expensive and 100W was as big as most went. Drive units in those days often boasted 100dB/W or higher efficiencies as opposed to the typical 96db of a lot of todays units. This was achieved by ever larger magnets, light cones and short voice coils. Bass response was correspondingly poor.

In cab design two techniques broadly were used to raise sensitivity. A lot of PA designs used horn cabs to increase efficiency and I remember a lot of touring bands going out in the UK with huge stacks of Martin horns.


The solution for guitars and bass were to use multiple speaker units like the Marshall 4x12, usually used in pairs. The efficiency of a speaker increases with the square of the increase in radiating surface so you get a 3db increase in sound with double the no of speakers for the same power. For bass this led to 2x15's and 8x10s. Each 10" speaker may only handle 50W but the cab handles 400W and gives you 9db more than a single speaker for each of those watts. Each speaker may only have a couple of mm excursion before distorting but together that's all they need.

A lot of rock conventions were the result of a bid for ultimate volume. Guitarists used speakers with huge midrange peaks to get extra volume. Bassists adopted underdamped cabs with a bass peak for the same reason. Singers adopted falsetto or the upper part of their range to cut though over all this sound. To an extent the conventions of rock were determined by the technology of that time.

[28mistertee]

So in a nutshell it's subjective really, I'll look at ensuring the wattage of my head doesn't exceed rating of cabs.
This is turning into a really informative thread though, brilliant 😊