Double Cabs are Louder ..or are they.

[brensabre79]

[quote name='Count Bassy' timestamp='1407336131' post='2519560'] Because ?? (Not being facetious, it's a genuine question). [/quote]

Because...

[quote name='Bill Fitzmaurice' timestamp='1407255491' post='2518853']
The number of cabs doesn't matter, the number of drivers does. Maximum output is limited by the total driver displacement, T/S spec Vd. The displacement of two drivers is double that of one, the resulting increase in maximum output by doubling the driver count is 6dB. It doesn't matter if the two drivers are in one cab or in two cabs with the same net internal volume.
By the same token when you plug a second identical cab into your amp the voltage swing into each cab remains constant, the total driver displacement doubles, and you get a 6dB increase in output. But you can only do so if the halving of the impedance load doesn't go below what your amp can deliver.
[/quote]

[Lozz196]

[quote name='chrismuzz' timestamp='1407253120' post='2518820']
Bigger rigs certainly LOOK louder
[/quote]

They certainly do. My old band got told we`d have to turn down once, whilst we were wheeling our 412s across to the stage at an outdoors gig in a field facing nothing but more field. They thought we were going to be loud just due to the cabs we used.

[HowieBass]

From what I've read, in the situation where you go from one cab at say 8 ohms to two cabs at 4 ohms this 6dB increase that's been noted is due to +3dB by doubling the power (where in this situation this idealised amp can deliver 100 watts at 8 ohms and 200 watts at 4 ohms) and another +3db by doubling the number of drivers (where you've gone from say two speakers in one cab to four speakers in two cabs). What we're saying therefore, is that doubling the cabs/drivers gives a higher gain in volume (+6dB) than you'd expect by going from 100 to 200 watts (+3dB).

[Ghost_Bass]

[quote name='HowieBass' timestamp='1407343293' post='2519642']
(...)
(where in this situation this idealised amp can deliver 100 watts at 8 ohms and 200 watts at 4 ohms)
(...)
[/quote]

I'm understanding the OP's question as to what would be the difference between using one or two cabs if this amp could deliver 100W at both 8ohm and 4 ohms. Basicly, what's the difference between using one driver and two drivers if both systems are fed with the same amount of signal/power/eq/impedance/etc.

I think that the valve amp example is the best, you have two identical amps set to give exactly the same output signal (the first set at 4 ohm and the second at 8ohms) to two different speaker systems, the first with two identical cabs (8ohm each) and the second to a single 8 ohm cab identical to the other two. Wich system would sound louder?

Maybe i'm wrong and didn't read well the OP.

[Chienmortbb]

[quote name='stingrayPete1977' timestamp='1407275826' post='2519172']
Im no expert but as I see it in laymans terms the problem with your calculation is that you are working on the 100 watt amp running flat out, constantly, I suppose if you did that your theory might work until the amp or speakers died but in real world terms how much wattage is an amp putting out during a gig?
[/quote] The amp power is not important except, as Bill says, that it can cope with half the impedance (yes I am talking of two identical cabs). The more I think of this, the more I think of other parameters that may affect matters. It there a different effect if the cabs are stacked vertically or side by side.


I think I may have to get some cabs out and measure. Don't hold your breath though as the cabs are at the back of a very stacked garage.

Edited August 6, 2014 by Chienmortbb

[Muzz]

[quote name='Lozz196' timestamp='1407340759' post='2519613']
They certainly do. My old band got told we`d have to turn down once, whilst we were wheeling our 412s across to the stage at an outdoors gig in a field facing nothing but more field. They thought we were going to be loud just due to the cabs we used.
[/quote]


Hahahahahaha...that's fantastic: the earliest we've ever been asked to turn down is when the drummer hit his snare once (unmiked and not very hard) - it was the first sound we'd made setting up...

[Bill Fitzmaurice]

[quote name='Ghost_Bass' timestamp='1407344588' post='2519657']
, you have two identical amps set to give exactly the same output signal to two different speaker systems, the first with two identical cabs (8ohm each) and the second to a single 8 ohm cab identical to the other two. Wich system would sound louder?
Maybe i'm wrong and didn't read well the OP.
[/quote]I don't think you read post #5.
The difference will be 6dB.

[Ghost_Bass]

[quote name='Bill Fitzmaurice' timestamp='1407352850' post='2519766']
I don't think you read post #5.
The difference will be 6dB.
[/quote]

I did, i'm just trying to clarify what's the main question here. I see people answering to things as "doubling the speakers you half the impedance and get more output" and i don't think that this was the OP's question.

[yorks5stringer]

Not seen any mention of "head room".( as in the extra created when an additional speaker/speakers is added).....

[chrismuzz]

[quote name='yorks5stringer' timestamp='1407424110' post='2520394']
Not seen any mention of "head room".( as in the extra created when an additional speaker/speakers is added).....
[/quote]

+1

If you have two cabs side by side, you've got room for another head!

[Count Bassy]

[quote name='Ghost_Bass' timestamp='1407423791' post='2520386']
I did, i'm just trying to clarify what's the main question here. I see people answering to things as "doubling the speakers you half the impedance and get more output" and i don't think that this was the OP's question.
[/quote]

+1, I don't think this was the OP's point either.

Obviously if you half the impedance, and the amp is capable of driving that impedance, then it's obviously going to be louder.

I think his question was if the impedance you're driving remains the same, but one cab has two drivers (total impedance 8 ohm), and the other has one (Also 8 Ohm), then is the 2 driver cab louder and, if so, why?

[Beer of the Bass]

[quote name='Count Bassy' timestamp='1407429265' post='2520490']
I think his question was if the impedance you're driving remains the same, but one cab has two drivers (total impedance 8 ohm), and the other has one (Also 8 Ohm), then is the 2 driver cab louder and, if so, why?
[/quote]

I've seen it suggested elsewhere (and in older forum posts by BFM) that the increase in sensitivity from coupling closely spaced woofers is 3dB, though only where they are spaced at less than 1/4 of the wavelength. So the quoted 6dB increase in SPL when adding a second cab or driver to a solid-state amp is 3dB from doubling the amps power output and 3dB from the increased sensitivity, if I've understood this correctly (and if I haven't, feel free to explain why!).

[HowieBass]

[quote name='Beer of the Bass' timestamp='1407433505' post='2520555']
I've seen it suggested elsewhere (and in older forum posts by BFM) that the increase in sensitivity from coupling closely spaced woofers is 3dB, though only where they are spaced at less than 1/4 of the wavelength. So the quoted 6dB increase in SPL when adding a second cab or driver to a solid-state amp is 3dB from doubling the amps power output and 3dB from the increased sensitivity, if I've understood this correctly (and if I haven't, feel free to explain why!).
[/quote]

I pretty much said this on post #28 LOL.

[Bill Fitzmaurice]

[quote name='Beer of the Bass' timestamp='1407433505' post='2520555']
I've seen it suggested elsewhere (and in older forum posts by BFM) that the increase in sensitivity from coupling closely spaced woofers is 3dB, though only where they are spaced at less than 1/4 of the wavelength. So the quoted 6dB increase in SPL when adding a second cab or driver to a solid-state amp is 3dB from doubling the amps power output and 3dB from the increased sensitivity, if I've understood this correctly (and if I haven't, feel free to explain why!).
[/quote]That's another way of viewing the result of doubling driver count while maintaining the same voltage swing. For that matter if you double the displacement via doubling the excursion with one driver, which is accomplished by doubling the voltage swing, the result is also 6dB. It's very clear when you look at it from the standpoint of displacement and voltage swing, but as clear as mud when you look at it from the standpoint of power and impedance. That's one reason why when engineering speakers we look at volts, not watts.

[Roland Rock]

I've seen a yacht analogy used. The wind speed (power) may remain the same, but if you increase the sail area (coneage), you'll go faster.

Edited August 8, 2014 by Roland Rock

[Phil Starr]

Bill is of course absolutely right about this. The interesting thing is about what the implications are for us as bassists. If you want a single speaker to do the job for you then you have to have something engineered for high volume displacement. This usually has a cost in terms of efficiency or a large exotic and expensive magnet system.

The other thing is that doubling the number of drivers gives you 3dB of extra sensitivity. 6dB if your amp can maintain the voltage swing. Go to an 8x10 and you have a potential 12dB of sensitivity or 9dB at the same wattage. Although this comes at the cost of the speakers radiation interfering with each other to make a lumpy bumpy frequency response and radiation pattern.

This extra efficiency means that your system is using much less power. 3db is half the power and 10db a tenth. So instead of 400W into an exotic lightweight you might be using 40W into an 8x10 for the same sound level, and only 5W into each of the eight speakers. If you are using the same amp it is going to run cooler and maintain its output, it is also much less likely to distort because of peaks in your playing. More importantly probably the speakers will run cool, 400W into a tiny coil trapped in a tiny air space inside a magnet does get very hot. Speakers running consistently high powers run very hot and the resistance of the coil rises reducing the speakers output so the sound changes as they warm up.

Of course this is only one variable, there are many other differences to take into consideration but there are distinct advantages in multiple speakers vertically stacked.

[Ghost_Bass]

[quote name='Roland Rock' timestamp='1407475767' post='2520853']
I've seen a yacht analogy used. The wind speed (power) may remain the same, but if you increase the sail area (coneage), you'll go faster.
[/quote]

That's what i'm trying to explain here, this analogy is wrong in the OP's POV. Using this yacht analogy think that at the same time you double the sail's area you also half the wind speed. Now wich boat will go faster?

(edited)

Edited August 8, 2014 by Ghost_Bass

[xgsjx]

I thought sails were triangle (or even square), not cone shaped.

[Bill Fitzmaurice]

[quote name='Ghost_Bass' timestamp='1407495849' post='2521097']
That's what i'm trying to explain here, this analogy is wrong in the OP's POV.
[/quote]It's a perfect analogy. The sails are equivalent to cones, the wind speed equivalent to voltage swing.

[Ghost_Bass]

[quote name='Chienmortbb' timestamp='1407251484' post='2518791']
(...)

Take for instance a Valve/Tube amp running into one cabinet at 8 ohms it is a 100 watt amp running at 100watts. Add second cabinet and switch the impedance switch to 4 ohms and at each cabinet will recieve 50 watts is all else is equal. Added to gether we have twice the speaker size in both driver ans cabinet but the same power, so no extra acoustic output, the SPL is the same. The only difference is that the new cabinet is closer to the player's ear so it will sound louder and have more mids and highs.

[/quote]

[quote name='Bill Fitzmaurice' timestamp='1407499144' post='2521165']
It's a perfect analogy. The sails are equivalent to cones, the wind speed equivalent to voltage swing.
[/quote]

So you're saying that feeding 100w (sorry to use watts but i think is better to example) to a single 4 ohm driver and feeding 100W to two 8 ohm drivers the voltage delivered from the amp to the cab system will be exactly the same?

[Bill Fitzmaurice]

[quote name='Ghost_Bass' timestamp='1407506189' post='2521300']
So you're saying that feeding 100w (sorry to use watts but i think is better to example) to a single 4 ohm driver and feeding 100W to two 8 ohm drivers the voltage delivered from the amp to the cab system will be exactly the same?
[/quote]Forget about watts. You'll never really understand how speakers work when your thinking is wattage bound. FWIW 100w into a 4 ohm load is 20 volts, and two 8 ohm drivers in parallel is 4 ohms, so yes, the voltage swing will be the same as into a single 4 ohm driver.

[UglyDog]

[quote name='Muzz' timestamp='1407347256' post='2519686']
Hahahahahaha...that's fantastic: the earliest we've ever been asked to turn down is when the drummer hit his snare once (unmiked and not very hard) - it was the first sound we'd made setting up...
[/quote]Pretty much exact same thing happened to my band many years ago, at a [s]working mens'[/s] [i]retired old farts' [/i]club. Drummer sat down behind his kit, hit the snare once, and a voice from the room somewhere said "Ooh, it's a bit loud..."

[mcnach]

[quote name='Lozz196' timestamp='1407340759' post='2519613']
They certainly do. My old band got told we`d have to turn down once, whilst we were wheeling our 412s across to the stage at an outdoors gig in a field facing nothing but more field. They thought we were going to be loud just due to the cabs we used.
[/quote]

A few times sound guys have expressed concern about volume when I was still setting up my gear (typically in a situation where bass is backline only and perhaps another band would have just used a crappy tiny weeny bass combo on the floor, and I chose to bring two cabs to stack one upon the other... this sometimes was a 2x10 and 2x12 (TC cabs) or more recently a BF Compact plus a small 12" on top).
I can understand that if they don't want things to get too loud, they have to let the bands know. That's ok. I actually prefer it when we're not crazy loud, as I can hear everything better! But when someone keeps going on about it... it gets annoying. Last guy I asked to come over, and showed him my volume knob "look, you see? I've got one of these too! So you're in charge, if it's too loud, let me know and I'll turn down"... he got a bit offended at my tone of voice, but come on, I heard him already the third time he told me.
I love having two cabs stacked, I just hear myself better and it sounds better, without having to play loud at all. My legs don't have ears.

[LukeFRC]

[quote name='Phil Starr' timestamp='1407492515' post='2521041']
Bill is of course absolutely right about this. The interesting thing is about what the implications are for us as bassists. If you want a single speaker to do the job for you then you have to have something engineered for high volume displacement. This usually has a cost in terms of efficiency or a large exotic and expensive magnet system.

The other thing is that doubling the number of drivers gives you 3dB of extra sensitivity. 6dB if your amp can maintain the voltage swing. Go to an 8x10 and you have a potential 12dB of sensitivity or 9dB at the same wattage. Although this comes at the cost of the speakers radiation interfering with each other to make a lumpy bumpy frequency response and radiation pattern.

This extra efficiency means that your system is using much less power. 3db is half the power and 10db a tenth. So instead of 400W into an exotic lightweight you might be using 40W into an 8x10 for the same sound level, and only 5W into each of the eight speakers. If you are using the same amp it is going to run cooler and maintain its output, it is also much less likely to distort because of peaks in your playing. More importantly probably the speakers will run cool, 400W into a tiny coil trapped in a tiny air space inside a magnet does get very hot. Speakers running consistently high powers run very hot and the resistance of the coil rises reducing the speakers output so the sound changes as they warm up.

Of course this is only one variable, there are many other differences to take into consideration but there are distinct advantages in multiple speakers vertically stacked.
[/quote] most interesting post i've read for a long time.

[bridge]

[quote name='mcnach' timestamp='1407529505' post='2521601']
A few times sound guys have expressed concern about volume when I was still setting up my gear (typically in a situation where bass is backline only and perhaps another band would have just used a crappy tiny weeny bass combo on the floor, and I chose to bring two cabs to stack one upon the other... this sometimes was a 2x10 and 2x12 (TC cabs) [b]or more recently a BF Compact plus a small 12" on top).[/b]

[/quote]

Dude,
I am at present, running a BF compact and a GB Streamliner 900. I intend to get a midget to compliment this set up, A) when one is available at the right price, B)when I actually [i]have [/i]the right price!! my question is, what 12" are you using with the compact? I need an extra cab, and was about to reseach what alternatives would be suitable, in place of a midget, should they become available at a price I can afford. cheers mate.

Edited August 13, 2014 by bridge