1 speaker vs 2 speakers

[LeoZeppelin]

Hello everyone,

Happy New Year !

I am new to this website and pretty much a newbie when it comes to anatomy of amps. All I know is what I learned in school in basic electronics & sonic and some during college.....all in all, not much....which is why I thought that experts & more knowledgeable folks here could probably advice me better.

I am hunting for an amp right now, a tube amp to be specific. I plan to use it during my jam with rest of the band (so drums/2nd guitar/vocals/bass/possibly keyboard soon....making it all loud enough), and for small/medium size gigs (where generally they would mic the amp). I play Blues, Hard Rock, Progressive Rock/Metal etc. I know a 30/40/50W amp can go loud enough (Peavey classic 30/Orange 30 W or a regular 40W Fender hot rod, Peavey Classic 50).

What I can't justify yet is, why would I need 2x12 instead of 1x12 (I used 12" there as generally I find that as standard size). What extra kick a second speaker will give when it comes to basement practice with band or a regular gig? In your opinion guys, will there be any difference amongst 2, going by the usage I mentioned above?

Thank you all in advance.
Best Regards.

[Bruce / Mission Amps]

It is generally accepted that with two really good 12" speakers (high SPL per watt).... you can expect that combo will be quite a bit louder than the same amp using a single 12".
What that infers is that a 20-30 watt amp driving a 2x12 bottom will sound as loud as a 50-60 watt driving a single 12" cab.
I would always go with the lower wattage and two better speakers.

[pdf64]

All else being equal, the 2x12 amp will put out 3dB higher sound pressure level than the 1x12. Which is equivilent to doubling the power input to the 1x12, ie a 50 watt 2x12 will be as loud as a 100 watt 1x12.
By the same token, the 1x12 amp will be hitting it's sweet spot at a lower sound pressure level than the 2x12, getting you a good tone without drowning out everyone else.
Tonally, the 2x12 will have a bit more bottom end, due to the larger cone area being moved, and the (probably) larger cab.
The 2x12 will be more directional than the 1x12, ie there will be more of an 'on-axis' trebley beam than the 1x12.
If the 2x12 speakers are wired in parallel, it will be more reliable (than the 1x12 or 2x12 series wired), as if one of them dies, the other will still be putting out.
It would be best for your hearing and the overall sound quality to keep the stage sound pressure levels as low as practical.
With a 5 piece line up, that might be difficult to manage, and will depend on the personalities, egos, musical intelligence and sensitivity of the individuals involved, as well as the group personality and chemistry that you create as a whole.
A 2x12 will give you a bit more firepower, but a 1x12 will spread you sound out a bit better, will allow you to push the amp harder and so thicken up the tone, and will fit onto a crowded stage a bit easier.
Of course, 'all else being equal' is not the case, as 1 beefy speaker will be equal to 2 weedy ones, though the 2 weedy speakers (ie greenbacks) may be the only way to get the tone you're after. And a 2x12 configuration will allow you to mix 2 different speakers to really fine tune your tone (my preference being a greenback and blue).

[cminor9]

you called greenbacks "weedy". I don't think I have ever heard this term used to describe a speaker. What do you mean by that? Weedy sounds pejorative, and I have always read good things about greenbacks.

[tedmich]

why not one open backed and one sealed or ported? It'd be the best of both worlds...has anyone tried this? Two different speakers, even open backed can add some complexity to the sound, say a Tonker + Bigben, see:
Eminence - The Art and Science of Sound

[pdf64]

No intention to disparage greenbacks - I've got 6 of them! I just picked on them as an example of speakers of lower efficiency than the norm. I meant weedy in terms of not being able the generate the same spl as, say, an EVM12L.
I tried running my Fender 75 combo (EV SRO12) with a 4x12 (closed back with Fanes), and wasn't keen on the result, it was neither one thing nor the other, in a bad way. Set the tone controls to suit the 4x12 and the SRO sounded honky, set to suit the SRO and the 4x12 was too woofy and boomy - it was difficult not to have the negatives dominating. The tone was better with one or the other.
Dispersion wise, on-axis the beam from the 4x12 dominated, whereas off axis it was the honk from the SRO, except for certain low notes that set off the resonant thunk of the 4x12.

[GibsonLover]

Maybe do a little more searching about SPL on this forum - there is more information and math out here to support it.
Wired in series, there is no increase in SPL for two speakers over one, because each speaker sees half the voltage. There is a -3dB penalty due to half of the voltage, and cancels out the +3dB gain by added cone surface. Cone excursion is less, so you should have a better bottem end.
Wired in parallel, each speaker sees the same voltage and you get the 3dB benefit noted above because the cone area is doubled.
Remember to switch between the output jacks on the amp (4/8 ohm) to maintain the same load to the amp in order to evaluate the difference correctly. If you want higher SPL, a more efficient speaker is also a huge plus. You can get that 3dB difference just by using a more efficient speaker, and not break your back with a 2x12 combo.

[rudutch]

Shavano Music Online - Speaker SPL - How much power do you need?

[mooreamps]

why not one open backed and one sealed or ported? It'd be the best of both worlds...has anyone tried this? Two different speakers, even open backed can add some complexity to the sound, say a Tonker + Bigben, see:
Eminence - The Art and Science of Sound

yes. The 2x12 I built, the upper speaker is sealed internally. The lower speaker is a back folded horn which is vented out the front. I used mahogany ply and neo magnet celestion speakers. I don't think the total cab weight is any over 30 pounds. The system is now down-reved as I have a newer design I am planning to build in the next few coming months. Just not sure if I want to build another 2x12, or do it as a raptor style 4x15.

-g

[Glass Snuff]

Wired in series, there is no increase in SPL for two speakers over one, because each speaker sees half the voltage. There is a -3dB penalty due to half of the voltage, and cancels out the +3dB gain by added cone surface. Cone excursion is less, so you should have a better bottem end.
Wired in parallel, each speaker sees the same voltage and you get the 3dB benefit noted above because the cone area is doubled.

I think there's something wrong with your math. Either way you wire them, each speaker will have half the current flowing through it. It's the current in the coil that generates the magnetic field that causes the cone to move.

[mooreamps]

Maybe do a little more searching about SPL on this forum - there is more information and math out here to support it.
Wired in series, there is no increase in SPL for two speakers over one, because each speaker sees half the voltage.

perhaps one of the most simple concepts for power transformers inside a guitar amp, but it eludes so many. Think of it this way ; for a given input, the 8 ohm tap produces "twice" the output voltage as the 4 ohm tap....


It's just that simple ......


-g

[GibsonLover]

That's what we got for short answers to long questions...

"Either way you wire them, each speaker will have half the current flowing through it." Well, two elements in series have the same current, don't they? You might be saying that either way the amp is supplying the same voltage and current to a given load, but that's only true if your amp can provide the current in the first place.

I'm only saying that if more SPL is the goal, an array or more efficient speakers will get you there. Everyone has plugged a 5W Champ into a 4x12 and has said, "Wow...". That's because it is louder - with the same load.

Here's a blog from someone who knows more about it than we do.
Stimulus & Power Boosters (about half way down)

Yes, my math was wrong, but my point is the same. Notice with an array AND more efficient speakers, the SPL adds up nicely, whether it's two speakers or nine - given the same load and the ability to provide current.

[Glass Snuff]

Looking back, my math was wrong too. I know what I was thinking, but...

In terms of 'in the room' sound, as opposed to what might be measured right in front of the speakers, two speakers will give you slightly more bass and slightly less treble, due to reinforcement of the former and cancellations of the latter.

In short, Bruce was right. And pdf64 added some some practical considerations that are worth thinking about.

BTW, I don't think Mr. Broskie "knows more about it than we do". If he were to actually build that lline array he envisions, I think he would be quite surprised. Here's a link to someone that actually does know more:

linkwitzlab.com/

[GibsonLover]

OK - I can point to an encycolpedia too.

The Broskie post was only an illustration of the math, because opinions are like belly buttons. It provides foundation to answer 'why', if you understand it. Yes, the tone will be different with multiple speakers, but PDF was also off the mark with the numbers. 3dB is not 'equivalent to doubling the power', nor is the number 3dB. It also takes 10 times the power for twice the volume, not achievable by adding one speaker.

Read the original post and see if you have answered anything. I'm still recommending what Bruce said - get a better speaker.

I use a cab with three different baffles for the same reason the original poster was asking. They all sound different, yes, but provide different SPL as well.

[pdf64]

'PDF was also off the mark with the numbers. 3dB is not 'equivalent to doubling the power', nor is the number 3dB.'

Please explain why you think that, and then I'll try to help you see where you are getting mixed up.