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[joecool85]

Yeah, I hadn't mentioned anything about frequency since I was only referring to guitar.  But it is true.  Bassists normally need roughly 3x the wattage to get loud enough to be heard well and not be "fuzzy".

Part of that is due to not being able to hear the bass as well (human ear limitations) but alot of it is also mechanical limitations of he speaker - it is simply more difficult to produce low frequency notes, thus requiring more watts.

[Jack1962]

yes bry frequency makes a world of difference the higher frequencies will ride on top of the low frequencies.
yes in theory joecool and jm this is true , but in practice it isn't , it is true that between a 100 watt and a 50 watt amp you won't hear much difference in volume. I have a Marshall JMP and a MG10 and 2 1960 cabs if ya want to come and prove your theory 

                                          Rock On

[DavenPaget]

yes bry frequency makes a world of difference the higher frequencies will ride on top of the low frequencies.
yes in theory joecool and jm this is true , but in practice it isn't , it is true that between a 100 watt and a 50 watt amp you won't hear much difference in volume. I have a Marshall JMP and a MG10 and 2 1960 cabs if ya want to come and prove your theory 

                                          Rock On

Ears naturally compress high volumes
So 100 watts is actually 2x louder then a 50w much further away . ( like 20m )

[Puguglybonehead]

As a guitarist, I've come to realize, not that much power is really needed. My band is a basic old-school punk band. (we started playing in 1978) Drums, bass, guitar, singer (if you can actually call what he does "singing"). In the past, I would use an 80 watt, 80 lb Traynor Mark 3 combo. This thing could blast a Fender Twin off the stage, no problem. It was way too much power! I only had occasion to turn it above 3 once. That was at an outdoor gig at Nathan Phillips Square.

I realized how much I hated hauling this 80 lb monster around. Now I use an old 20 watt Supro, a small combo with a single 10" speaker. It's so small, I can carry it to gigs in my backpack. I installed the best 10" speaker I could afford, an Eminence Ragin' Cajun. It's rated at 100dB SPL sensitivity. I've found this setup to be more than enough, even with an aggressive drummer. No problem being heard. Strangely enough, I'm still not turning this amp up much past 3. 

I would think that a 20 to 30 watt amp in a combo with something like the 12" Eminence Wizard (103 dB SPL) would be more than enough for any situation. In fact, I'll bet that a speaker like that could make a decently designed 10-watt amp be heard just fine.

[DavenPaget]

As a guitarist, I've come to realize, not that much power is really needed. My band is a basic old-school punk band. (we started playing in 1978) Drums, bass, guitar, singer (if you can actually call what he does "singing"). In the past, I would use an 80 watt, 80 lb Traynor Mark 3 combo. This thing could blast a Fender Twin off the stage, no problem. It was way too much power! I only had occasion to turn it above 3 once. That was at an outdoor gig at Nathan Phillips Square.

I realized how much I hated hauling this 80 lb monster around. Now I use an old 20 watt Supro, a small combo with a single 10" speaker. It's so small, I can carry it to gigs in my backpack. I installed the best 10" speaker I could afford, an Eminence Ragin' Cajun. It's rated at 100dB SPL sensitivity. I've found this setup to be more than enough, even with an aggressive drummer. No problem being heard. Strangely enough, I'm still not turning this amp up much past 3. 

I would think that a 20 to 30 watt amp in a combo with something like the 12" Eminence Wizard (103 dB SPL) would be more than enough for any situation. In fact, I'll bet that a speaker like that could make a decently designed 10-watt amp be heard just fine.

The reason why people think tube is louder then solid-state , is because . well SS practice amps are always given *s!!t* speakers .
10W can do some serious *s!!t* with a 103db monster . ( no less 30W )
but i think it can at most do ... 105db .
i don't know about 30W , though . But my insane 30W DSP amp ( i have never been able to crank it up above 2 ) , came with a unnamed mad 10" 98db , can do some serious sound . It even won those dumb AC30's

[joecool85]

I fixed some math and stuff in the first post.  You can't just add speakers to get more volume.  If you take two 96db/watt speakers and run them together each with their own 1watt source, you would come out with 99db.  If you ran them together splitting a 1 watt source, you would still only get 96db.  This is assuming a large distance between the speakers (say one on each side of the stage or farther apart).  If they speakers are in a single cab, they will work together acoustically, producing more volume per watt and also producing more vibrant lower tones due to the increase in cone area.

So the big advantage of more speakers is two fold: tone (yes, it will sound different) and maximum wattage handling.

I apologize for any confusion.

The key thing to remember is use efficient drivers.  It doesn't matter if you have a single 8" or two full 4 x 12" cabs, the more efficient the drivers, the more volume you get.  Look for at least 97db, ideally 100db or better.

[its_cabs]

Sound Pro,
go ahead - 'spress yerself! Couldn't agree more. It's the sound, not the volume, that leaves an impression. I mean, even Cream, loud as they were, was very considerate of the sound, all well balanced and clear for each player. Conversely, after weeks of practice, and only one warm up gig, when my nephew and I finally got a good tone dialed in at this club for our Costa Rica debut, after 2 or 3 songs I noticed the sound was all messed up. I told the promoter to track down the culprit. Seems the club owner, accustomed to louder, more aggressive hard rawk than our own down home, mostly accoustic southern blues thing, kept sneakin over and cranking up the board - after we had it set just right for the room. Oh, well, he did recently ask me when I'm coming back...cabs

[Axeslinger61]

Fascinating. Quite informative, as well. Who do y'all recommend for a manufacturer of efficient, reasonably priced speakers? Back when I was gigging regularly as a bassist, the Peavey Black Widow was one of the most efficient speakers out there-but I wasn't that crazy about the tone. Nowadays, I'm playing guitar primarily, and am thinking about downsizing my rig, so speaker efficiency is a definite concern.

[Puguglybonehead]

For speaker efficiency, have a look at some decent quality ceramic speakers. The "vintage-tone"snobs seem to love alnico, but those speakers are seldom as efficient. If you can find the full specs (including the all-important SPL rating and frequency range) then you can get some idea.

Eminence make really efficient speakers, full specs available. So do Weber. (but they don't publish their full specs) Also, decide on which speaker size works best for you, tone-wise. The larger the speaker, the better chance of it being more efficient. Lots of loud 15-inch, 12-inch and even 10-inch speakers out there. 8-inch or smaller and you're starting to lose out.

Read lots of the reviews online. They may seem subjective, but they've usually steered me right. Anyways, Eminence and Weber both make great sounding, loud speakers.

[KMG]

Don`t forget another important thing - specific "voices" of different speakers.
One speaker maybe good for vintage sound but poor for modern.
http://www.youtube.com/watch?v=jWK0sa7tlfI

[QReuCk]

Most of "vintage" speakers do have a huge boost (sometimes 3 to 6db more than the overall ratting) in high mids (in the region of 3KHz to 6KHz). I do think you should really be carefull when selecting a speaker based on efficiency. Try to find response curves and see if most of this efficiency is located in frequencies you don't want to push too far. Overwize you will need to filter them out somehow and obtain an overall efficiency of the speaker + filters that is not what the overall spl indicates.
E.g. if your tone is more in the 200 to 2000 Hz frequency range, a speaker with overall 100 db/W.m with a speep boost at 4KHz won't be more efficient for you that a 98db/W.m one which have a boost precisely in the frequency range you seek.
 

[Steve Dalllman]

Many if not most of modern guitar speakers are in the high 90's to low 100's in dB's. Even high excursion bass speakers are usually in the high 90's but the compromise is usually less highs.

This is for 12's and 15's. As you go smaller, especially with 8" and 6 1/2" speakers, the sensitivity is often lower, in the 92dB range.

Most manufacturers will not only give all the specs, but will include a frequency graph. Every speaker will have a rather shallow low end rolloff, relatively flat across the mids, and then have a large peak between 2 and 4kHz followed by a treble rolloff that may extend gracefully to 5-6kHz or beyond, or be rather ragged.

A guitar pickup is similar, with it's "resonant peak" producing a characteristic tone.

Bass and PA speakers will usually use a crossover selected to be below that large peak, bass less so.

Tube VS SS watts...an endless argument. Let me give my take. When you reach the limits of a SS amp, there won't be much beyond it's limits. A 100watt amp may be rated 100 watts @ .05% distortion. Once the rails are hit, there may be nothing much left above a certain point.

With a tube amp rated at 100watts @.05% distortion, may be capable of 200 watts @ 30% distortion and sound great doing it.

The tube amp may keep putting out far more than it's rated power, at a very high distortion level, but still sound good. With the SS, the possible output will be limited by it's power supply limits, and at high distortion, may not sound very good.

My 12 watt Princeton Reverb will put out a lot more than a 15 watt SS amp using a TDA2030 power amp chip...a LOT more.

[Roly]

A guitar pickup is similar, with it's "resonant peak" producing a characteristic tone.

Just to remark that I've done a bit of modeling of guitar pickups where it seemed that the input impedance of many amps was too low and seriously damped this self-resonance, and lately building some high impedance buffers which has confirmed that impedances in excess of 1Meg (e.g. ~5Megs) lets the pickups "sing" more, are more tonally rich (and that's into a s.s. amp).  Adding shunt capacitance to bring this resonance down in frequency, VariTone style, is something I'm also fooling with.

Tube VS SS watts

Not taking sides, since I use one of each, but Rod Elliott at ESP has some interesting views on the very different output impedances of each.

Another factor is that when a s.s. amp clips it presents the speaker with an effective short circuit, and thus high damping, but when a valve amp with an output transformer clips di/dt goes to zero and it's more like an open circuit; the upshot of which is that during clipping the speaker in one is highly damped while in the other it's effectively cut loose.

[Jack1962]

Great explantions on this subject 

I love hearing JM and Joe lay the info down for ya , so here's a twist to this , why is a lower wattage tube amp louder than higher wattage solid state amp , thru the same speaker.

[Roly]

Again Rod Elliott at ESP has an interesting take on this;

http://sound.westhost.com/valves/valve-trans.html
http://sound.westhost.com/valves/valve-trans2.html

There are a number of factors in play, but the essence of this observation is that a valve amp has a much higher output impedance than a transistor amp, perhaps as much as 20 ohms compared to a fraction of an ohm.  This results in a valve amp behaving somewhat like a current source, while a transistor amp behaves much more as a pure voltage source.

Into a resistive dummy load there is little apparent difference between the types, but the situation changes considerably when they drive a real world loudspeaker load.  The impedance of a real loudspeaker cab is anything but constant across the audio spectrum and the drive voltage available from a valve amp tends to track these changes of impedance and thus seems to have more headroom to overload than a transistor amp of the same power.

Apart from technical considerations, I have been running a 60 watt valve amp and a twin-50 watt solid state amp, both homebrew, for guitar and keys/synth into the same cabs for many years now, and as a player the difference is very apparent when I have been forced for some reason to cross over and use the valve amp for keys or the solid-state amp for guitar.  Running keys into the valve rig results in a more or less dirty/muddy output at all levels, while running guitar into the transistor rig has a "distortion wall" at overdrive that sounds downright nasty.

The inherent and progressive distortion of valves sound better with tenor guitar, specifically, but keys, PA, and I note bass guitar, sound better with the ample clean power of a solid-state amplifiers run below clipping.  Bass rigs frequently contain some form of signal compression as well as very large amplifiers so they rarely clip.