More speakers with the same head equals what?

[waltschwarzkopf]

Hi guys,

I was trying a Bassbreaker 15 the other day (awesome amp, by the way). I want it for home use, but I asked the guy at the store if it would be enough to take to the rehearsing room. He said maybe and when I asked if connecting another 1x12” speaker would help me, he said “it’s still 15 watts.”

I understand that a 15 watt amp is fixed at that max power, but using a 1x8” cannot possible be the same as using a 4x12”, right? Especially if one gets to spread the sound all over the room, for example placing a 1x12” combo on one side and a 1x12” cab on the other. It may not be twice as loud, but I would certainly be louder and sound more even, right?

I’ve always used combos or one-head plus one-cab combinations, so I don’t have any experience un bigger cabs nor on multiple cabs on one head. So any information and explanations that you could give me will be greatly appreciated!

Cheers,
Walter




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[Blille]

Re: More speakers with the same head equals what?

First there's the difference between speakers. The key there is speaker efficiency. Given the same input different speaker can be significantly louder or softer. If you swap a greenback for a gold for example, the increase in output volume is more than doubling your watts. There's a lot written about DB vs watts so I encourage you to search it.

Then there's the 1 vs several speaker difference. Usually you hear that more speakers move more air and can cover an area better so the perceived output is higher.

(Btw, xposted to TDPRI and strattalk)

 

[FuseG4]

Re: More speakers with the same head equals what?

I hear a lot that every time you double the area of the speakers, all else unchanged, you get 3db volume (sound pressure level) increase, which is noticeable.
So going from a 1x12 to say a 4x12 of the same speakers would be 6db louder, you would perceive this as "substantially louder" and if you had higher efficiency speakers and more of them you could really, really smoke a 1x12.

The 15W thing is about headroom by which I mean the limit on the amp's ability to produce clean tones and bass and go from full quiet to full loud and not compress. Bass frequencies take the most wattage to push through a speaker so even with a 412 cab you will lack a certain thump compared to say a 50W amp, and your sound will be more compressed and dirty because the amp is working hard. By the time you have the same volume as a 50W amp, you may be very distorted on the 15W amp, depending on design of the amps. If you need clean tones, this matters a lot. If you need a really snappy punchy response and have the amp feel like it's always reacting immediately and sharply to what you give it, you want a bigger amp than 15W probably. If you want a dirty clean tone and really pushed overdriven tube amp tone with lots of compression and some "give" to the response, lower wattage amps let you push the amp to the point of power tube breakup. Not everyone needs full on power tube distortion.
A second 112 cab may get you what you want if you need to be just noticeably louder than you are. if you play the amp at practice and think that the amp needs to be a lot louder, or you need just the clean tone a lot louder, or the bass farts or mushes out, consider a bigger amp.
And as far as placement in the room, I like 2 112 cabs next to each other. I use different speakers in each cab and they mix and spread just fine, too far apart and I find the sound less interesting and if your speakers and cabs are different then having them too far apart gets distracting for me.

 

[IM4Tone]

Re: More speakers with the same head equals what?

I hear a lot that every time you double the area of the speakers, all else unchanged, you get 3db volume (sound pressure level) increase, which is noticeable............

That would be a violation of one of the fundamental laws of physics (law of conservation of energy). It's not louder, but the dispersion gives the perception that it is......applied correctly, a good thing.

 

[SlyFoxx]

Re: More speakers with the same head equals what?

It actually is louder and I've run tests on this with my 4x12 cab all speakers being equal. 1x12 will give you XdB. The same configuration with 2x12 will give you X+3dB. 4x12 will give you X+6 dB. Has something to do with midrange drivers in close proximity to one another (coupling) actually increasing the efficiency of the speaker system. Also 4 speakers will give greater horizontal and vertical dispersion of the sound thus giving your rig a larger footprint if you will.

 

[IM4Tone]

Re: More speakers with the same head equals what?

It actually is louder and I've run tests on this with my 4x12 cab all speakers being equal..................

:bsflag:
Your test method had to be faulty. Guaranteed! :bye:

 

[Lake Placid Blues]

Re: More speakers with the same head equals what?

I have run a test with two almost equally sized speaker cabs. One was a 1x12, and the other a 2x12. Both had V30 speakers in them. Both were 8 ohms load. Same tube head, same exact settings, back to back to back. No difference in volume, either perceived or measured. Just saying. That was the observation.

 

[Lake Placid Blues]

Re: More speakers with the same head equals what?

I read about an interesting experiment on another forum. They were taking wattage measurements of a 100 watt amp with 6L6s, 5881s, El34s, clean and dirty... and so forth. Then they set up the amp and the master volume how they always set it in their rehearsal studio with acoustic drums. Output was 2.5 watts on the master volume 100 watt amp.

A 12" speaker will be significantly more efficient and therefore significantly louder than any 8" speaker.

 

[FuseG4]

Re: More speakers with the same head equals what?

That would be a violation of one of the fundamental laws of physics (law of conservation of energy). It's not louder, but the dispersion gives the perception that it is......applied correctly, a good thing.

you're right the relationship is different, sorry. doubling of power supplied in an audio system is a 3db increase in sound pressure levels.
in this case you are decreasing the power to each speaker when you split the signal to more speakers. However,
regardless of whether or not we have all the equations necessary to relate power from the amp to speaker area to sound pressure levels to perceived loudness, when I add my second 112 cab, it's generally louder, just a bit. Don't ask me to quantify it, i'm probably nudging the amp volume up without realizing it.

 

[dave74]

Re: More speakers with the same head equals what?

412 can seem louder because your head is more in line with the speakers, especially a slant cab.

 

[Lake Placid Blues]

Re: More speakers with the same head equals what?

A 4x12 compared to a 1x12, and the size, and design, and materials, of the speaker cabinet does affect the sound even if it is not necessarily louder because of more of the same speakers. 4x12s usually get a fuller tone with more bass and could be perceived as louder by the hearer for that reason.

 

[Darg1911]

Re: More speakers with the same head equals what?

It's depends and it can get complicated. Here is a presentation of the absolute best, short, understandable explanation that I have come across ...

https://www.youtube.com/watch?v=mhIQSxKFgoQ

 

[IM4Tone]

Re: More speakers with the same head equals what?

This will be my last attempt to dispel the myth, since people seem to believe what they want rather than facts.
At 2:48 the video states: "+3dB every time the number of speakers is doubled"
So think about this:
I start with a 1 watt output into a speaker with a 100dB sensitivity. I'll add identical sensitivity speakers and keep the total impedance identical and all measurements are @ 1m.
According to the above claim:
2 speakers=>103dB
4 speakers=>106dB
8 speakers=>109dB
16 speakers=>112dB (110dB-120dB for a Rock concert)
32 speakers=>115dB
64 speakers=>118dB
128 speakers=>121dB (chainsaw = 120dB)
256 speakers=>124dB
512 speakers=>127dB
1024 speakers=>130dB
2048 speakers=>133dB
4096 speakers=>136dB
8192 speakers=>139 db (Airplane taking off)

Yes the number of speakers is getting ridiculous, but if the above claim were true, it would follow.
Does anyone really believe a 1 watt amp could achieve Rock concert (110 dB) levels with 8 to 16 speakers?

No more from me on this topic.....:bye:

 

[Darg1911]

Re: More speakers with the same head equals what?

This will be my last attempt to dispel the myth, since people seem to believe what they want rather than facts.
At 2:48 the video states: "+3dB every time the number of speakers is doubled"
So think about this:
I start with a 1 watt output into a speaker with a 100dB sensitivity. I'll add identical sensitivity speakers and keep the total impedance identical and all measurements are @ 1m.
According to the above claim:
2 speakers=>103dB
4 speakers=>106dB
8 speakers=>109dB
16 speakers=>112dB (110dB-120dB for a Rock concert)
32 speakers=>115dB
64 speakers=>118dB
128 speakers=>121dB (chainsaw = 120dB)
256 speakers=>124dB
512 speakers=>127dB
1024 speakers=>130dB
2048 speakers=>133dB
4096 speakers=>136dB
8192 speakers=>139 db (Airplane taking off)

Yes the number of speakers is getting ridiculous, but if the above claim were true, it would follow.
Does anyone really believe a 1 watt amp could achieve Rock concert (110 dB) levels with 8 to 16 speakers?

No more from me on this topic.....:bye:

Yeah. That's a generalization that probably should have been left out by Segeborn at the end but it's still being taken out of context ... and a "cute" exaggeration on your part. The qualifiers in the video are clear and the math regarding them is about 1/2 way through the video.

 

[Lake Placid Blues]

Re: More speakers with the same head equals what?

This was a direct observation, not theory:

I have run a test with two almost equally sized speaker cabs. One was a 1x12, and the other a 2x12. Both had V30 speakers in them. Both were 8 ohms load. Same tube head, same exact settings, back to back to back. No difference in volume, either perceived or measured......

In my experience a 4x12 does have a psychological influence on people, especially club owners, though.

 

[skyydogg01]

Re: More speakers with the same head equals what?

One thing that you guys aren't thinking of ... Power.

15 watts to one speaker is 15 watts per speaker.

15 watts to 2 speakers is 7.5 watts per speaker.

Assuming that the total impedence is the same, SPL would be exactly the same. You are halving the power to the speaker resulting in -3db from that speaker. Adding another speaker at the same wattage will increase by 3db due to acoustic coupling.

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[SlyFoxx]

Re: More speakers with the same head equals what?

I'm not saying you can keep adding speakers forever and keep getting free volume. As volume is only a certain sound pressure at a tiny point in space....like your ear. Adding much more than 4 speakers to the equation introduces a certain amount of phase shift and comb filtering due to the ever increasing distance from the close speakers to the speakers further away. The coupling of 2,3 or 4 speakers only occurs at a limited range of frequencies as well....about 100Hz to 600hz. But those frequencies also happen to pretty much cover the fundamental frequencies of the 6 string guitar. And it's not that you're getting "free" volume by adding speakers. You're using the amplifier power more efficiently over the fundamental range of the guitar. And I know all this because I've actually done the work by testing all of this.

I started with my dB meter at 6 feet from the cab pointed dead center. Cab lifted 3 feet off the floor to reduce coupling from the floor. Recorded about 20 seconds of a crunchy "A" power chord keeping my right hand as even as possible but chose a crunchy sound for its natural compression. Played sample through the amp to get an average of 100dB at the meter through one speaker (8ohm) with the amp tap set to 8 ohm. Tested the rest of the speakers one at a time to ensure their efficiencies were the same. From there the only changes to the set-up were number of speakers driven and swapping the amp tap to 4 ohm for the two speaker test. Result were three more and six more dB from 2 and 4 speakers respectively.

So yes, with a 4x12 you get a little bit more.

 

[Boogie Bill]

Re: More speakers with the same head equals what?

I'd say you may get a little more with more speakers...if they are more efficient.

But what you really get is less wear and tear on your speakers.

Bill

 

[Jacew]

Re: More speakers with the same head equals what?

While I'd like to agree on the evidence that more speakers does not necessarily make difference in loudness, there's one thing I'd like to question: How linear is the efficiency of speakers?

If you're pushing 15 watts in one greenback, the compression might have some effect on efficiency: If you have 4 of them, it seems less power per speaker would result in less compression and possibly more efficient rig?

 

[Chistopher]

Re: More speakers with the same head equals what?

One thing I will say is that the perception that more speakers equals louder comes from the fact that more speakers can handle higher wattages from louder amps. Provided that every speaker is receiving the max wattage its rated for, it will be louder to have multiple speakers.

When you add another speaker you no longer have a 15w 1×12, you have two speakers being run at 7.5w each, which even if more speakers makes a sizable difference
will not be able to take a bedroom speaker to rehearsal levels.

I'd say what you want is either more efficient speakers or a larger amp. I don't think a 15w tube amp should have any trouble keeping up with a band if you are able to mic it or stand far enough away from the drummer. Toss an Eminence Wizard in that bad boy and you will have no problems with volume.