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How much is enough when we speak about amp power?

In: Guitar amplifiers Wednesday Jun 25,2008

electric guitars and amplifiers, how much is enough? Because I haven’t had a “poll” here in a while, today’s question is how much is enough when we count the power of an amp for a “regular” rehearsal room?

Let’s define the conditions: regular rehearsal room, let’s say 7-8m long, 7-8 m wide, regular height, I guess, about 2.45 m(?) and a “regular” band, something like drums, bass, 1 guitar, 1 keyboard, 1-2 microphones.

So, considering these conditions(that you may adjust to fit your “regular” image of a rehearsal room/band), how much would you consider it would be enough for a guitar amp? Would 75 watts do it? Or do you need 100 watts? Or 50 watts will do the trick also?

Keep in mind I speak here about distinguishing your guitar from the rest, in a “constructive” way, not making as much noise as possible so nobody else could be heard beside you…

Also, would the same wattage work for the bass amp too, or is it different?

How about for a 2 guitars band, does it change anything? What other parameters should be considered? Walls type? Drummer madness? Music style? Amp type? Number of speakers? Types of speakers? What else?

Let me hear you!

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16 Responses to “How much is enough when we speak about amp power?”

pzychotropic
June 25th, 2008 at 11:23 am

In my experience, there is very little difference in volume between a 50w and a 100w amp.
More relevent is the space your playing in. In nearly all club/pub venues a 50w is perfectly adequate. I would only use a more powerful setup in an open air situation where the extra power projects the sound volume further.
However, a miked up speakers negates the need for walls of guitar stacks. I suspect they are really only for show these days, but nice all the same.
Ovidiu
June 25th, 2008 at 11:45 am

Well, what you say that there is little difference between 50 and 100 watts makes me think that actually there is no need of more than 50 watts. Because if you would turn a 100 watts Marshall full power it will blow you away

So, should we agree on 50 watts?
Gary
June 25th, 2008 at 1:55 pm

My 30 watt Laney tube combo has played many small pubs and has never been turned up beyond 2 on the volume control - in our small rehearsal space I’m usually too loud!
Danel R. Lehrman
June 25th, 2008 at 2:07 pm

I usually use a Peavy Classic 30. That would be plenty with some to spare. Never have a volume problem. I would not mind having 50 watts though. For me I use an overdrive/distorsion with a volume boost. that way I don’t play to loud until i play lead, then I hit the boost. I also use my volume control for swells in volume and general loudness control.
The main thing to me is to pay attention to the other members. FYI, I was told to turn it down last nite at our jam. I got zoned and forgot other people were there too!
Dr. J
June 25th, 2008 at 2:30 pm

Ya gotta look at the resistance of the speaker (or cabinet(s)) the amp is driving. That gives us the whole picture.

If my tube head is rated 100w at 8 ohms, I’ll get 100w of power from the amp if I’m using a 4 ohm 12″ speaker. If I wired two 4 ohm speakers into my homemade cabinet, I’d get 100w, but if I wired two 8 ohm speakers into my cabinet, I’d only get 50 watts of power (if my math and memory skills serve me correctly).
Dr. J
June 25th, 2008 at 2:34 pm

No… that’s not right… two 4 ohm speakers is a 2 ohm load, (50 watts) two 8 ohm speakers is a 4 ohm load (100watts)… I need coffee….
Ovidiu
June 25th, 2008 at 2:45 pm

I also use an amp that is not that loud, around 30 watts too just that the drummer is very loud usually and I would feel the need of a small boost. I also have different volumes on solo and rhythm but I still feel a boost sometimes.

@Dr J: Now I am not convinced…Two 8 ohm speakers wired together means 4 ohm. I guess you get the full power from your amp if it is 100W/4ohm, not on 8 ohm, right? Or I need coffee too…
John
June 25th, 2008 at 5:12 pm

wow….heady discussions today…

I’m using a 30watt (switchable to 60) head, and I have no trouble at all hearing over the drummer, and 1 or 2 additional guitarists.

Watts and Speaker loads not withstanding, I really think that you should be more concerned with your sound pressure level. Anything over 85db is dangerous…protect your hearing…it’s your most valuable asset as a musician

Regarding speaker wiring, you need to look at whether the speakers are wired in series or parallel.

In series, the resistance adds. so, two 8ohm cabinets in series produces 16ohms resistance.

In parallel, however, the resistance formula is more complicated. You multiply the resistance, and then divide that number by the added resistance….

so, for two 8ohm cabinets:
8 * 8 = 64, and 8+8 = 16, therefore, 64/16 = 4
so two 8 ohm cabinets in parallel results in a 4ohm load.

for three or more cabinets in parallel figure out the load for the first two, then use that with the next, etc…

so, for two 8 ohm cabinets, a 16 ohm cabinet, and a 4ohm cabinet in parallel:
8 * 8 = 64, and 8+8 = 16, therefore, 64/16 = 4
now, use the result:
4*16 = 64, and 4+16 = 20, so 64/20 = 3.2
and use the result again:
3.2*4 = 12.8, 3.2+4=7.2, so 12.8/3.2 = 4
so the total load of all 4 cabinets in parallel is 4 ohms.

Okay…sorry for geeking out….going for coffee now!!!!
Ovidiu
June 25th, 2008 at 5:21 pm

The interesting part is that seems that everybody agrees that the 30 watts amp is enough for rehearsing. Very interesting, I have always presumed mine is not enough.

I used to have a band mate, in a previous band with a 100 watts Marshall. Man, he didn’t have any problems with volume. I remember one moment he used his amp for a concert instead of the one provided by the sound company as stage amp and at the sound check, he was loud than the volume on the main system for that place.

Of course, the sound on the main system was not on full power, but we used to laugh hearing his amp right from the stage
Sammy
June 25th, 2008 at 8:09 pm

I’m going to echo the 50w crowd. I’ve played in a room the size you’re speaking of with a guitarist (I mainly sing) who had a 100w Marshall 1/2 stack. He was up around 2 on the dial (maybe 3) and it overloaded the room. My 50w combo (tube) can smoke a room. And of course in a live setting, it’s the PA that’s driving the room’s sound, not the guitar amps.

In my band’s current practice configuration, we use no guitar amps. Everything runs through the PA, so we don’t have that problem of bassist and guitarist inching the volume upward until it’s a wall of sound. As a singer, it’s frustrating when that happens because it just becomes a ridiculous competition for volume and the sound mix ends up burying the vocals. It just creates a cacophony of noise.
Ovidiu
June 25th, 2008 at 8:12 pm

I know the feeling. We use the PA for voices, but each guitar has it’s own amp, so everybody feel that has control.
lex
June 26th, 2008 at 12:31 am

i use a 400w randall just over half way up and i’m deaf now . awesome!
Ovidiu
June 26th, 2008 at 7:42 am

I think you’ve overdone it! Where do you play, on a stadium?
JC
June 26th, 2008 at 9:27 pm

Yeah, really 30w is probably gonna always be more than enough… For more than that, there will most likely be a PA in which you can run your amp!
Ovidiu
June 27th, 2008 at 7:40 am

I see that everybody settled for the 30 watts combo in the end.
burnleaf
June 29th, 2008 at 11:52 pm

I think you must put your self in relation to the other band members. In my current band (classic heavy rock), (for live or practice) the bass player is blowing through 8×10s and rattling the floor, another factor of course is how hard your drummer is hitting it (hard)- and being heard above that, we like it that way. I play a Marshall DSL 100 and the it does it all. In a small venue, I put two 1-12 8 ohm cabs (4 ohm load 100 w) at each corner of the front of the stage pointing back at the band. I crank the Marshall to about 3. For larger places, I bring a 4×12 (4ohms as well) and crank the Marshall between 4-5 usually., blowing out at the audience. The preamp channel is only turned up until it gets fat, not dirty. I use a Boss super Distortion to add a Fender type distortion and a marshall guvnor for heavier stuff. Neither pedal is set to a ‘fuzzy’ distortion - then I step on a clean boost for leads. By turning the guitar volume down in relation to these pedals you can get a whole slew of classic tones.

How much is enough when we speak about amp power?

16 Responses to “How much is enough when we speak about amp power?”

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