Is double the speaker worth half the watts?

[Wasnex]

In any case, given the same output volume, having double the speakers is going to feel a lot better and I dare anyone to disagree.

Feel better maybe. Course if it's loud enough to produce a brown note you may disagree. I have been in situations where the bass was loud enough to give me vertigo and nausea, but no poop...yet.

Sound better is entirely a different matter. When you add a second driver you get perfect coupling in the frequency band where the driver spacing is less then 1/4 wavelength. So the tone will be fuller. However as the frequency increases, the wavelength shortens, so off axis you start to get destructive interference between the drivers. This can be viewed as a compromised dispersion pattern, comb filtering, phasing, the formation of primary and secondary lobes, etc.

Personally I don't need huge lows on stage, so I prefer the purer sound of a single driver cab or perhaps a mult-way cab. But if more volume or low end is required than a single driver cab can produce...that's when you need more drivers.

I did much of my pro work with an Eden D210XLT placed vertically on top of a 10 space or larger rolling rack. I wedged a Countryman Type-85 under the front edge of the cab so it tilted back and aimed the primary lobe at my ears. I also had an D410XLT. Sometimes I stacked both Eden cabs on top the rolling rack. I have to admit it sounded better and punched a lot harder, but it was way more than I needed, and also a lot of additional unnecessary work. (The top of the full array was just over my ear-level, so standing directly in front of it put me in the primary lobe.

 

[MVE]

I would invest a few bucks to built myself a good looking speaker stand that raises your existing cab 2 feet of the ground and thus closer to your ears. Take it from someone who used to own two 212 cabinets and most of the times only brought one or ended up unplugging the bottom cab. I like loud, but I feel that with four 12s you sacrifice punch for boom in most rooms. Unless you play really large venues at high stage volumes all the time, I think it's overkill.

Thank you. Your response is most helpful. As you have actually tried the vertical 412 stack and didn’t seem to love it.

Everyone, I never said my rig is not loud enough. It’s plenty loud! It’s louder than I need. I was just asking if the second cab would add additional “feel” to the rig.

It sounds like, from the people who have tried it, that it really doesn’t and isn’t worth it.

 

[jnewmark]

A little different situation, yours: Nineteen-pound lighter cabs and no need to run in series and halve the power. OP has 46lb. cabs. and can’t run his amp at 2 ohms. There are a lot of cab and amp combinations that would make the math work for me, but not the OP's.

Understood.

 

[Rip Van Dan]

I have a 4ohm Berg CN212 being pushed by my Demeter amp that is only stable down to 4.
Thinking about getting another matching CN212 and running them in series at 8 ohms.

My question is: How does twice the speaker area at twice the impedance compare?

It seems 3-400 watts pushing four 12s would be more fun than 700 watts pushing two.

Thoughts?

The two ways to increase your sound level is to either double your wattage - for instance 500-watts up to 1000-watts - or to double your speaker area. Both will raise your sound level by 3db. Scientifically speaking, a 3db increase is actually a doubling of the sound pressure level, but the human ear doesn't hear it that way. It takes a 10db increase for the human ear to recognize it as "twice as loud". It's generally less expensive to buy more speakers than to double the watts of your amp, so adding speakers is a common way to get more sound out of your gear.

Best choice in my opinion is to get an amp that will put out some serious rms wattage to begin with and match it to cabs that not only sound good but have good power handling and good sensitivity.

As far as sensitivity goes, Sound Pressure Level (SPL) ratings are typically given at 1-Watt of power, 1-Meter away from the source. That means they run 1-watt through it and measure the decibel level 1-meter away from the source. Unfortunately this is about as good as the standard gets. Rarely will they specify what frequency range was used for the reproduction of sound at 1-watt. Often it is a tone at 1KHz, but can be others. And, all that really does is show the results of a 1KHz sound, not the wide spectrum of frequencies that we use. Still, it beats a poke in the eye with a sharp stick.

I have a first generation acoustic B410 and I also have a DNS410 from DNA. Both are 410's but there is a huge difference in the sound they produce. I had to write acoustic over and over to get their SPL rating for their 410 cab because they didn't list it in their specs. They finally wrote back and said their sensitivity rating for that cab was 92db @ 1W/1M. That is what would be known as low sensitivity.

The other cab is rated with an SPL of 106db @2.83v/1M, which is extremely high. The 2.83volts actually = 1 watt in an 8 ohm environment. In a 4 ohm environment that would be 2-watts. My cab is 8 ohms so the comparison of the cabs would the same 1W/1M as far as power applied. No idea what signal was used at 1-watt by either of them, so it still may be comparing apples to oranges, but at least it's something.

What that means, if all things were equal, is that it would take about 15-watts of power (16 watts to reach 107db) to produce the same decibel level of sound (106db) that 1 watt of power produces through my DNS410 cab. That sounds like a huge disparity and it is.

In actual practice My DNS410 cab is far louder than any 410 cab I've heard and most 810 cabs. Plus it has more clarity, definition, and articulation than my acoustic 410 does, as well as about 3 times the power handling capability (1400-watts rms vs 400-watts rms). I use an 800 watt Eden amp to drive it and have not been able put the master volume higher than 9:30 either indoors or outdoors.

So another big part of the volume of your system is the sensitivity of the speakers combined with the power of your amp. Anything that starts you out around 100db is going to be decent sensitivity. Because of the various testing methods to come up with the SPL rating, one cab can be significantly louder than another brand with the same SPL rating. The real proof will be when you hear it, so best to try out a cab before you buy it if at all possible.

 

[jnewmark]

Thank you. Your response is most helpful. As you have actually tried the vertical 412 stack and didn’t seem to love it.

Everyone, I never said my rig is not loud enough. It’s plenty loud! It’s louder than I need. I was just asking if the second cab would add additional “feel” to the rig.

It sounds like, from the people who have tried it, that it really doesn’t and isn’t worth it.

Started raising my cabs closer to ear level 30 years ago. tremendous improvement in " how " I hear what I want to hear.

 

[Wasnex]

Thank you. Your response is most helpful. As you have actually tried the vertical 412 stack and didn’t seem to love it.

Everyone, I never said my rig is not loud enough. It’s plenty loud! It’s louder than I need. I was just asking if the second cab would add additional “feel” to the rig.

It sounds like, from the people who have tried it, that it really doesn’t and isn’t worth it.

If the rig is louder than you need, it could "add additional 'feel'" due to the added coupling in the low frequency range. I explained why in post #41. Whether this makes it worth dealing with the extra cab is entirely up to you. Also, if you do a vertical 412 array and get the top speaker up close to ear level, it could sound really nice and the vertical orientation of the drivers will have better horizontal dispersion than a traditional 412 with side-by-side drivers.

Why not try it and find out for yourself?

I can assure you this rig sounds and feels awesome, but I have no intention of ever gigging with it. It's simply to much to carry and setup. "Quad of Quads" I.E. four Genz Benz 1288T Uber Quads.

 

[mjmeche]

Invalid Link Removed

 

[eukatheude]

Feel better maybe. Course if it's loud enough to produce a brown note you may disagree. I have been in situations where the bass was loud enough to give me vertigo and nausea, but no poop...yet.

Sound better is entirely a different matter. When you add a second driver you get perfect coupling in the frequency band where the driver spacing is less then 1/4 wavelength. So the tone will be fuller. However as the frequency increases, the wavelength shortens, so off axis you start to get destructive interference between the drivers. This can be viewed as a compromised dispersion pattern, comb filtering, phasing, the formation of primary and secondary lobes, etc.

Personally I don't need huge lows on stage, so I prefer the purer sound of a single driver cab or perhaps a mult-way cab. But if more volume or low end is required than a single driver cab can produce...that's when you need more drivers.

I did much of my pro work with an Eden D210XLT placed vertically on top of a 10 space or larger rolling rack. I wedged a Countryman Type-85 under the front edge of the cab so it tilted back and aimed the primary lobe at my ears. I also had an D410XLT. Sometimes I stacked both Eden cabs on top the rolling rack. I have to admit it sounded better and punched a lot harder, but it was way more than I needed, and also a lot of additional unnecessary work. (The top of the full array was just over my ear-level, so standing directly in front of it put me in the primary lobe.

Well, he does already have two drivers. AFAIK, if he stacks the cab vertically he won't have issues with dispersion.

 

[Wasnex]

Well, he does already have two drivers. AFAIK, if he stacks the cab vertically he won't have issues with dispersion.

Stacking vertically limits dispersion vertically, so there are still ramifications. To overcome the problem either elevate the speakers so your ears are in the primary lobe, or tilt the top speaker back so the primary lobe is aimed at your ears....this is assuming you want to hear the direct, full range response of the speaker. I do, but not everybody does.

When you elevate the speakers so your ears are in the primary lobe, you can vary your distance from the speaker and the tone doesn't really shift much. If you tilt the top speaker back, so the primary lobe is aimed at your ears, you may have to stay in a sweet spot, to prevent the tonal balance from changing. It really depends upon how effectively the speakers integrate across the splay angle.

 

[Rick James]

When the system height is doubled the vertical dispersion angle is halved, but the dispersion reduction tends to be more than offset by moving the uppermost drivers closer to ear level.

 

[HaphAsSard]

When you add a second driver you get perfect coupling in the frequency band where the driver spacing is less then 1/4 wavelength. So the tone will be fuller. However as the frequency increases, the wavelength shortens, so off axis you start to get destructive interference between the drivers. This can be viewed as a compromised dispersion pattern, comb filtering, phasing, the formation of primary and secondary lobes, etc.

If I understand your post correctly (at least the part that would seem to address the question in my post above):
if we had a solid-state amplifier
and a subwoofer
and then added an identical one
(both low-passed below the baffle step so the latter's lowering is not in the equation)
the increase in voltage sensitivity for the lowest frequencies would actually approach 9dB = (potentially) 3dB from the doubling in power delivery from the amp and as much as 6dB from the coupling of the lows...right?
The oft-quoted "double the drivers -> +3dB" figure is thus an average of what happens to the lows (which are more point-sourcey) and what happens to the mids (which are progressively less so) as regards our bass cabinets (which are fuller-range than low-passed subwoofer cabinets), correct?

EDIT - Finally: is it then correct to state that adding an identical cab to an existing one, even without an increase in sensitivity due to series wiring in the OP's scenario, does not simply mean "more of the same" in terms of tone, but actually a general darkening thereof due to both a lowering of the baffle step (because of the larger total baffle area) and more coupling in the lows than in the mids?

 

[fdeck]

The oft-quoted "double the drivers -> +3dB" figure is thus an average of what happens to the lows (which are more point-sourcey) and what happens to the mids (which are progressively less so) as regards our bass cabinets (which are fuller-range than low-passed subwoofer cabinets), correct?

Correct. I'd say that most of the rules of thumb apply when the speaker is in the range where it's largely omnidirectional, probably up to 250 Hz or so given typical spacing between stacked speakers.

 

[CryingBass]

1 x Berg NV115 = Stimulating. 2 x Berg NV115 = Spiritual!
Obviously mine is a small and targeted comparison, YMMV, and your ears will point the way

 

[Wasnex]

If I understand your post correctly (at least the part that would seem to address the question in my post above):
if we had a solid-state amplifier
and a subwoofer
and then added an identical one
(both low-passed below the baffle step so the latter's lowering is not in the equation)
the increase in voltage sensitivity for the lowest frequencies would actually approach 9dB = (potentially) 3dB from the doubling in power delivery from the amp and as much as 6dB from the coupling of the lows...right?
The oft-quoted "double the drivers -> +3dB" figure is thus an average of what happens to the lows (which are more point-sourcey) and what happens to the mids (which are progressively less so) as regards our bass cabinets (which are fuller-range than low-passed subwoofer cabinets), correct?

EDIT - Finally: is it then correct to state that adding an identical cab to an existing one, even without an increase in sensitivity due to series wiring in the OP's scenario, does not simply mean "more of the same" in terms of tone, but actually a general darkening thereof due to both a lowering of the baffle step (because of the larger total baffle area) and more coupling in the lows than in the mids?

I am not an expert on these matters. Here's what I think I know: Assume the voltage is held constant when you add an identical speaker, and thus cut the load impedance in half. In other words the first cab continues operating at the same SPL, and another cab is added that is also operating at the same SPL. Under this condition you theoretically get +6dB across the range in which diver spacing is within 1/4 wavelength.

I know even less about the baffle step aspect of this. But it seems logical that the size of the baffle between the two drivers would be extended, so there should be some effect, but probably rather small, because only a very small percentage of the total baffle is extended.

I wouldn't necessarily call it a darkening of the sound...too me that implies reduced highs instead of enhanced lows. But now we are arguing semantics I suppose.

 

[ashtray]

I have an Eden combo that has the external speaker jack wired in series. Weird. But adding a 4 ohm cab to my 200 watt combo results in something like 120 watts total, 60 going in to each cabinet. So, is it louder when I add a cab? Yes it is. Can I explain why? Probably not. But probably has to do with me not pushing the combo to its limits to start with, so adding another cab really reduces the chance of overpowering the speakers, so I can freely turn it up if needed

I think the whole +/- db thing is frequency dependent too. So adding speakers and dropping wattage might have different effects across the frequency spectrum.

 

[ashtray]

In contrast to my previous post, I have a 15 watt guitar amp (at 8 ohms min). Solid state. Played through a 16 ohm 4x12 cab, the volume was noticeably lower and “less defined”. When running through only half of the cab (2x12 vertical) at 8 ohms, the amp was louder and more full. More highs and lows.

This amp actually sounds really good, and I gigged this setup all the time as a guitarist. Guessing 16 ohms dropped the wattage to the point each speaker was getting 1-2 watts, and the speaker was “eating” much of that wattage - if that makes sense. Maybe the first watt sent through the speaker gets mostly lost to heat and movement? I don’t know - can’t explain. Just know what my ears were telling me. I expected a similar result to my Eden amp where double the speakers at half the wattage was an increase in noticeable volume. That wasn’t the case though with that amp.

So... I guess the answer is it will really depend how much you crank your amp, the speakers themselves and their arrangement, the room acoustics, the eq of the amp, the humidity of the room, the number of people wearing corduroy, etc.

 

[Rick James]

I am not an expert on these matters. Here's what I think I know: Assume the voltage is held constant when you add an identical speaker, and thus cut the load impedance in half. In other words the first cab continues operating at the same SPL, and another cab is added that is also operating at the same SPL. Under this condition you theoretically get +6dB across the range in which diver spacing is within 1/4 wavelength.

That's pretty close to expert. If the amp is solid state the voltage will remain constant with the second speaker and you'll get the full 6dB up to a point. When you get near the maximum output of the amp there's voltage sag in the power rails, so it won't be able to maintain the full voltage output into the halved impedance load. That's why halving the impedance doesn't give twice the maximum power output, more like 1.7 times, but unless your amp is way too small to begin with it's unusual to be running at full power anyway. At average levels you can put an SPL meter in front of your two cab rig and while playing a test tone see the meter go up by 6dB when you plug in the second cab.

I know even less about the baffle step aspect of this. But it seems logical that the size of the baffle between the two drivers would be extended, so there should be some effect, but probably rather small, because only a very small percentage of the total baffle is extended.

The baffle step is where the baffle is one wavelength in dimension. Above that frequency radiation is no more than 180 degrees, below it the sound wraps back around the cab, with a maximum loss of 6dB in the axial response when the frequency gets low enough to be fully omni-directional. But that formula only applies when the baffle is a circle. When it's a rectangle you get one baffle step frequency for the width, one for the height. Doubling the baffle height halves the baffle step frequency, but only with respect to the vertical axis. It's even more complicated when the cab is in front of a wall, because the sound that wraps around the cab isn't lost, it's reflected off the wall, so that reflected output adds back to the forward radiation, except where the distance from the baffle to the wall is 1/4 wavelength. In that case the reflected wave meets the original wave at the 1/2 wavelength distance, which is 180 degrees out of phase, so the reflected wave and direct wave cancel each other. That's called Allison Effect.