Educate me on amplifiers please....

[Admiral Axtell]

I have been playing bass for a while now but never really looked into amps too much, my parents bought me my 100 watt combo amp that I currently use and I bought my other 15 watt combo at a pawn shop for way cheap so I don't really know anything about amps or heads and I feel like I should since I am going to be looking into getting something much bigger when I get into a band. So Iv'e got some questions.
First off; What does Ohm mean, some cabs have 4 Ohm others have 8, what is it and what does it effect?
Also, what does the number of Ohm in the head mean in relation to the cabinet?

I know that the number of watts usually means more power the higher the number but not much else to be completely honest.
I can't think of any more specific questions though.
What else should I know?

[5port]

Very good info here:

Ohms FAQ

[BurningSkies]

Better yet. Start Here:

AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

[Stumbo]

Here are a few more links to check out:

8. COOL RIGS, EQUIPMENT, INFO
Upgrade bass/amp first?

~Amps, Heads, Rigs, Speakers, Cabs
Pros/Cons of Amp Design
Watts: How many do you gig with?(poll)
Watts: Amp "watts" vs. cab "watts"


>30 light-weight cabs,amps, combos
"Light weight" heads
TB micro-amp tone reviews

1 Buying a combo
2
Opinions/experiences-great small combo amps
The ultimate custom built combo?

Combos vs Head/Cab
Pre-amp/Power Amp vs Head/Cab or Combo
1. 2 ohm capable heads
2.
"I want a monster amp!"
Powerful,reliable rack amps

10s v. 12s v. 15s v. 18s
2
4x10 vs. 2x10/1x15
2
6x10 vs. 4x12(two 2x12)
Benefits of vertical speaker cabs

1x10's that do the job
Full range cab (Carvin LS1503)
1x15/6.5 custom cab
Big cabs
Low B reproduction/speakers/cab thread
Rig for low F#

1 Happy with my rig
2
Gig rigs

Micro-rigs of doom
Mini-rigs of doom
Rigs of doom
Cheap rigs of doom
Ulitmate fantasy rig

[AwkwardLoudness]

There's plenty of detailed reading in the above links, FAQ, etc. But, I'll give you the short answers.

First off; What does Ohm mean, some cabs have 4 Ohm others have 8, what is it and what does it effect? Also, what does the number of Ohm in the head mean in relation to the cabinet?

Ohms (Ω) is a measure of electrical impedance, which is similar to resistance, also measured in ohms.
For amps with vacuum tubes in the power sections, the current going in the output transformer needs to closely match the current going out to the speakers. Hence, the selected amp impedance needs to closely match the total impedance of the speakers. For solid state or hybrid amps, the output power is optimized at the minimum impedance rating of the amp, usually 2Ω or 4Ω. You want the speaker cab(s) impedance to be at least as much as that minimum value, and higher cab(s) impedance will reduce the amp's output power since it needs to work harder.

I know that the number of watts usually means more power the higher the number but not much else to be completely honest.

True, watts are a unit of measure for power. Higher power translates to more clean headroom, i.e. louder clean signal, all else being equal. Speaker cab efficiency + design have a larger effect on potential clean volume and overall volume, however.

I can't think of any more specific questions though.
What else should I know?

Play as many amps and cabs to figure out what you like, and then ask more questions or do searches on specific amps and cabs. Vacuum tube amps are higher maintenance and generally heavier compared to solid state amps, but vacuum tubes + transformers can provide tonal character and response that cannot be achieved any other way (for better or worse depending who's ears are listening).

[Admiral Axtell]

Thanks for all the links and answers, I have been doing a lot of reading and think I understand a lot better now, one other question I have that I can't seem to find an answer to... How does the number of watts in the head relate to the number of watts in the cab?? you want more in the head or more in the cab?

[Munjibunga]

Originally Posted by Stumbo

Here are a few more links to check out:

8. COOL RIGS, EQUIPMENT, INFO
Upgrade bass/amp first?

~Amps, Heads, Rigs, Speakers, Cabs
Pros/Cons of Amp Design
Watts: How many do you gig with?(poll)
Watts: Amp "watts" vs. cab "watts"


>30 light-weight cabs,amps, combos
"Light weight" heads
TB micro-amp tone reviews

1 Buying a combo
2
Opinions/experiences-great small combo amps
The ultimate custom built combo?

Combos vs Head/Cab
Pre-amp/Power Amp vs Head/Cab or Combo
1. 2 ohm capable heads
2.
"I want a monster amp!"
Powerful,reliable rack amps

10s v. 12s v. 15s v. 18s
2
4x10 vs. 2x10/1x15
2
6x10 vs. 4x12(two 2x12)
Benefits of vertical speaker cabs

1x10's that do the job
Full range cab (Carvin LS1503)
1x15/6.5 custom cab
Big cabs
Low B reproduction/speakers/cab thread
Rig for low F#

1 Happy with my rig
2
Gig rigs

Micro-rigs of doom
Mini-rigs of doom
Rigs of doom
Cheap rigs of doom
Ulitmate fantasy rig

You must have some kind of search function fetish.

[Munjibunga]

Originally Posted by Admiral Axtell

Thanks for all the links and answers, I have been doing a lot of reading and think I understand a lot better now, one other question I have that I can't seem to find an answer to... How does the number of watts in the head relate to the number of watts in the cab?? you want more in the head or more in the cab?

It's best to have them close to the same, but it's not a problem either way if you know what to do. If your amp is rated at greater wattage than your cabinet, don't crank up the volume too high. If you start to hear distortion, turn it down.

If your amp is rated at a lower wattage than your cab, don't turn the amp up to where it distorts the output. If you hear distortion, turn the amp down.

One of the biggest mistakes people make is trying to get more volume out of a system than it can produce. If your rig starts to distort (fart) at a lower volume than you need, then you need a more powerful amp and/or more speakers. Don't push it beyond distortion or you will blow speakers.

For gigging, I'd put the bare minimum amp at 500 watts (750 and up is better) and at least a high-quality 410 cabinet (or 215, if you like the sound of tone-eating muff monsters).

Jimmy's going to come on here and tell you he gigs successfully with a 15-watt rig, but he won't mention the 20,000-watt PA he sends his DI to.

[GrowlerBox]

Originally Posted by Admiral Axtell

Thanks for all the links and answers, I have been doing a lot of reading and think I understand a lot better now, one other question I have that I can't seem to find an answer to... How does the number of watts in the head relate to the number of watts in the cab?? you want more in the head or more in the cab?

There is no relation at all. The head power rating refers to the power output into a given load (i.e. the total impedance of your cabinets, measured in ohms), and the cabinet rating refers to the total power it can handle before the speakers suffer irreversible heat damage. Pretty much any amp head can blow pretty much any speaker if you do the wrong things -- especially try to push too much low-frequency signal through the speakers and too high a volume. You can, and for the most part should ignore the cabinet manufacturer's reported power rating. Listen to your speakers, and if they're distorting/farting, turn down the volume and/or the bass, and if you need to be louder, you need more speakers, not more power or supposed power-handling.

Edit: I guess Munji and I were typing more-or-less simultaneously. I would agree with most of what he says above, but would tip the balance in favour of more speakers over a more powerful amplifier for increasing volume once you get beyond a certain point. Doubling power output produces an increase of 3dB in volume in a perfect system, which is perceived as a real but trivial increase in volume, due to the fact that our hearing apparatus "damps" sound in approximately logarithmic fashion in order to allow processing of a large range of sounds (a sort of on-board compression). Some of this is lost in the unavoidable inefficiencies inherent in sound reproduction, so in reality, it's even less, more like 2 dB.

[jeff7bass]

Originally Posted by Munjibunga

It's best to have them close to the same, but it's not a problem either way if you know what to do. If your amp is rated at greater wattage than your cabinet, don't crank up the volume too high. If you start to hear distortion, turn it down.

If your amp is rated at a lower wattage than your cab, don't turn the amp up to where it distorts the output. If you hear distortion, turn the amp down.

One of the biggest mistakes people make is trying to get more volume out of a system than it can produce. If your rig starts to distort (fart) at a lower volume than you need, then you need a more powerful amp and/or more speakers. Don't push it beyond distortion or you will blow speakers.

For gigging, I'd put the bare minimum amp at 500 watts (750 and up is better) and at least a high-quality 410 cabinet (or 215, if you like the sound of tone-eating muff monsters).

Jimmy's going to come on here and tell you he gigs successfully with a 15-watt rig, but he won't mention the 20,000-watt PA he sends his DI to.

What he said ^^^. Except I've done plenty of gigs with 200-250 watts and a single, good 15" cab.

If you are looking to buy, tell us what kind of band, what kind of music, what kind of venues, and how much you want to spend and you'll get plenty of good suggestions, and some not-so-good.

[Stumbo]

Originally Posted by Munjibunga

You must have some kind of search function fetish.

Hi Munji,
I collect them as I read'm. No search involved.

I read a lot.

[Stumbo]

Originally Posted by jeff7bass

......I've done plenty of gigs with 200-250 watts and a single, good 15" cab.

So have millions of other bassists. Even 100 watts with 2x15 can play a lot of gigs. If you have the money, buy the best you can afford. Most of the time it will have higher power(head room) and speaker cabs that will handle more watts(heat) and move more air(longer voice coils).

Take your time. Maybe visit a few music stores. Listen to a few rigs. Play a few rigs. Find out what other people are using that play music that you like.

Let us know how it goes. Lots of people to help you out on TB.

Btw, which 100 watt combo do you have?

[Jim Campbell]

Originally Posted by jeff7bass

What he said ^^^. Except I've done plenty of gigs with 200-250 watts and a single, good 15" cab.

If you are looking to buy, tell us what kind of band, what kind of music, what kind of venues, and how much you want to spend and you'll get plenty of good suggestions, and some not-so-good.

yep,and i know a guy that rode from here to la and back on a 250 ducatti single,but it is probably better to have a tad more in reserve......there are plenty of good reliable solid state amps out there for five hundred or so ,and good quality tube amps can be found for about a grand and up used....

a good 4x10 and you're off to the races......quality gear holds it's value,so when you want to sell or upgrade you usually get back close to what you paid...

[AwkwardLoudness]

How does the number of watts in the head relate to the number of watts in the cab?? you want more in the head or more in the cab?

The stated power handling, i.e. thermal rating, of a cab is the estimated point where the amp's power will overheat and damage the speaker voice coils. However, most cabs cannot produce articulate bass notes all the way up to that stated thermal rating because the speakers reach their maximum excursion before that level. The EQ settings on the amp will influence speaker excursion...the magnets move more with more bass frequencies dialed in.

For tube amps, I like to have a cab with thermal rating at least twice the RMS watts of the amp. This is because tube amps are useful well past the RMS (clean) wattage threshold.

For SS amps, it varies a bit depending on the amp/cab because not all manufacturers measure amp RMS power and cab RMS power handling the same way. It's best to have a cab with at least equal power handling (or more) of the amp's RMS power. If the cab is rated more than twice or thrice the amp's power, then the speakers likely will be underdriven

[Russell L]

Extra question here (I've heard this debated):

Which designates MORE resistance, 4 Ohms or 8 Ohms? For instance, when I add another 8 Ohm cab to my 8 0hm head/8 Ohm speaker, it goes to 4 Ohms. Seems like two speakers would present more resistance. Or not?

[Downunderwonder]

That's the difference between series and parallel wiring. Two speakers are nearly always connected in parallel meaning two ways for the voltage to go, think in volts and all becomes clear.

Both cabs get the same voltage, quid pro quo more current comes out of the amp, it works harder, makes more noise.

[AwkwardLoudness]

Originally Posted by Russell L

Extra question here (I've heard this debated):

There's no debate to be had.

Originally Posted by Russell L

Which designates MORE resistance, 4 Ohms or 8 Ohms? For instance, when I add another 8 Ohm cab to my 8 0hm head/8 Ohm speaker, it goes to 4 Ohms.

Two 8Ω cabs in parallel equate to a combined 4Ω load.

Two 8Ω cabs in series equate to a combined 16Ω load.

[Admiral Axtell]

Originally Posted by Stumbo

So have millions of other bassists. Even 100 watts with 2x15 can play a lot of gigs. If you have the money, buy the best you can afford. Most of the time it will have higher power(head room) and speaker cabs that will handle more watts(heat) and move more air(longer voice coils).

Take your time. Maybe visit a few music stores. Listen to a few rigs. Play a few rigs. Find out what other people are using that play music that you like.

Let us know how it goes. Lots of people to help you out on TB.

Btw, which 100 watt combo do you have?

B100 Acoustic combo amp, It's alright... but not really, I can hardly hear myself over the drummer and he can't hear me worth sh*t hahaha.

I'm really into metal. I'd like to play stuff along the lines of Cannibal Corpse, Fleshgod Apocalypse, Nile, Brain Drill (well, maybe not that technical), stuff along those lines.
Basically some heavy tunes,. I hear that you need more power to be heard over everything in this kind of music, is that true?

I think I will check out what the bassists of those bands use too, thanks!

[SteveC]

I'll let everyone else give you the techno stuff. Here's another thought that some may disagree with but is true for most of the average people on this forum. Don't get the biggest thing you can find or afford. Contrary to what you may read or infer from Talk Bass, most of us can get by just fine with a 410 or 212 cab and a 500 watt head - give or take. That will carry most rooms without PA and will be plenty for a stage monitor with PA - unless you are in a band that has no idea what they are doing when it comes to volume.

[Russell L]

I hear ya, Steve. I've been gigging with my Markbass CMD 121H combo (one 12" with 300w) in ballroom-sized rooms, sometimes with PA support, sometimes not. Either way, it's carried the gig. I feel like another 112 cab would help in some case, though, especially outdoors. It would then run at 500w with two 12s and would cover anything I run into. I did run one 15" along with it once outdors and it was more than I needed for the variety band I was with then. They were pretty loud, too, with a large box-truck load of equipment. I have also played for many years before that with a Trace Elliot 115 combo at 200w and never needed more onstage. However, I have played with one mainline band outdoors with a 700w GK head and full-range cab containing an 18", plus two other speakers and horn (not my equipment, so I can't recall). Also, fronted the Atlanta Rhythm Section and played on their equipment with a similar rig. In either case the extra air getting pushed was welcome, but for most bars, ballrooms, and quieter gigs 200w is enough power, or 300w is even better, and one 15" can do the job, especially if there's support (like the Greenbrier Hotel or Grove Park Inn, for instance). In the case of the Markbass, the single 12" is amazingly efficient, and the rig only weighs 39 lbs. All I need is one more 112 cab and I can sell all my old stuff. Heh, heh, I love this neodymian magnet stuff.