More speakers with the same head equals what?

[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.

[Red_Label]

Re: More speakers with the same head equals what?

As has been mentioned, speaker type and its EQ curve matters more than using more speakers IMO. My Friedman V30-loaded 2x12 is much more in your face than my H30/Greenback loaded 4x12 (though the latter sounds far more pleasant). If I really want to cut through the mix, then I use the 2x12. If I want to sound fuller, then the 4x12. But fuller and louder aren't the same. Yes, adding an additional speaker of the same type will make it louder (or more full), but I won't be as big of a difference as using a more efficient or more in-your-face EQ'd speaker.