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Barefaced 2 Cabs vs 1volume question

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I have recently acquired a Barefaced 210s and Ashdown ABM Evo iv 600W

Its plenty loud enough for most situations (I do think its as loud as a good 410 as advertising suggests). On the rare occasions when I have a bigger gig with no PA support I intend to pair it with another cab. I have an ampeg 410 that I can pair it with, but I'm considering replacing that with another Barefaced 210s.

A Barefaced 210s can run at 4ohms or 12 ohms. The ashdown head can push 600w at 4ohms. So a single cab can potentially receive the the full 600w from the amp.

If I run 2 cabs, Ill need to switch the cabs to 12ohms, So I'm guessing I could be pushing around 450w split between both cabs at 6ohms. 

Therefore is the potential volume of a cab on its own is way more than that of a paired cab?

Would 300w to a single cab, be half as loud as 600w (is it linear)?

What is potential volume increase as a percentage if I run a second cab?

Hopefully the above makes sense.

Thanks 

Alex

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No. More speakers = more air being moved which generally (definitely in your case)  = more volume

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Quote

Would 300w to a single cab, be half as loud as 600w (is it linear)?

Halving the power (into one cab) would be -3dB.  In your case, it's slightly less, as you're going from 600W per cab to ~250W per cab; so perhaps -4dB.

 

Quote

What is potential volume increase as a percentage if I run a second cab?

Stacking twice the number of identical cabs is +6dB.

So overall, your two-cab system will be +2dB louder, which is a bit louder but not "twice as loud".

 

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Will your amp run happily at 6 ohms, I'm no tech but I remember a thread on here a while back about 6x10s which were rated at 6ohms and a few folks seemed to think that some amps simply won't do it. I might be wrong 

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18 minutes ago, Beedster said:

Will your amp run happily at 6 ohms, I'm no tech but I remember a thread on here a while back about 6x10s which were rated at 6ohms and a few folks seemed to think that some amps simply won't do it. I might be wrong 

ABM has a solid state output section so 4 ohms and above is fine.

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Since I posted this I’ve checked out some info online and in all honesty, I’m probably more confused.

so far I know that +6db is double the volume (I think!).

55 minutes ago, jrixn1 said:

Halving the power (into one cab) would be -3dB.

 

Did you take 6db as double the volume and divide by 2 (because your halving the power) to get a value of -3db? I did read that relationship between watts and volume is not linear.

Thanks all for the help so far

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3 hours ago, alexa3020 said:

 is the potential volume of a cab on its own is way more than that of a paired cab?
 

No, because watts don't matter. Volts, sensitivity and decibels do. I'll spare the math, but the two will go louder than the one.

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19 minutes ago, Bill Fitzmaurice said:

No, because watts don't matter. Volts, sensitivity and decibels do. I'll spare the math, but the two will go louder than the one.

Sorry I haven’t explained myself very well. I  do expect 2 cabs to be louder than 1.

A single cab at 600w I assume will be louder than a single cab at 250w (which is what a single cab would receive roughly if paired with another in the above scenario and assuming watts to volume relationship is not linear). 

So my train of thought was; if at 250w it reaches 75% of the volume it reaches at 600w, would pairing 2 cabs be 150% louder than a single cab.

after a bit of research I can see it’s really not that simple.
 

Edited by alexa3020

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1 hour ago, alexa3020 said:

Did you take 6db as double the volume and divide by 2 (because your halving the power) to get a value of -3db?

dB is a logarithmic scale.

Doubling (2) the power = 10 x log(2) = 3dB

Halving (0.5) the power = 10 x log(0.5) = -3dB.

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First of all, forget percentage and watts, like our grand old Mr. @Bill Fitzmaurice said. He sure knows speakers and maths, as well as dBs.

When you double the power, the dBs raise only a bit, around 3 dB.

If you want to hear the sound to double, you need 10 dB = 1 B more volume. In power this would equal multiplying the power output by 10. Now you have 450 W, so you would need 4500 W to double the volume you hear. 250, 600, or 450 watt produce practically the same volume to your speaker.

Clear so far?

If you believe the impedance (Z) is linear and a constant, you are walking on really thin ice. It changes drastically over the frequency range. If you want to dive into the amplifier technology, you will find that reducing impedance will increase the need for amperes. More amperes = higher temperature of the amplifier. After certain level the amplifier can not produce more power, or it would melt.

I could describe this Z like a stick, which you press with your thumb. The smaller number is like a sharper stick. Try to press this sharper stick and you feel just like the amp. The rise of power is not linear, otherwise our cabs would be Z = 0.08 ohms. Try to calculate the possible power output to this Z with a 30 W / 8 ohm amp... hint: it would be in kW class.

You are still following?

You have an issue with hearing your playing, raise the speaker. Turn it to you. Take a step away from the drummer, ask that g-word player to do the same and turn her amp away from you. Pretty simple, when you just adjust the current situation slightly. To play with just a little less volume helps, too. Talk to the others and just try it.

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13 minutes ago, itu said:

You have an issue with hearing your playing, raise the speaker. Turn it to you. Take a step away from the drummer, ask that g-word player to do the same and turn her amp away from you. Pretty simple, when you just adjust the current situation slightly. To play with just a little less volume helps, too. Talk to the others and just try it.

Yep. Re some of the previous posts here and elsewhere, the maths might explain why you hear what you hear, but in my experience will rarely predict it with any reliability. Trial and error is the best bet, and the best place to start is the gear you already have, adding extra cabs will always make a difference, just not always the difference you want

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8 hours ago, jrixn1 said:

Halving the power (into one cab) would be -3dB.  In your case, it's slightly less, as you're going from 600W per cab to ~250W per cab; so perhaps -4dB.

 

Stacking twice the number of identical cabs is +6dB.

So overall, your two-cab system will be +2dB louder, which is a bit louder but not "twice as loud".

 

That would be assuming adding 2 identical 8 Ohm cabs in parallel would have been as good as if the same amp had produced 1200W into a similar 4 Ohm cab, and somehow I doubt those numbers.

However theory says that adding up 2 sound sources of the same amount of dB gives +3dB, which mean that in theory the above equation should add up with exactly the 600W that the amp is rated at, since ((X Watt into an Y Ohm cab)= Z dB) + ((X Watt into an identical Y Ohm cab)= Z dB) = Z dB +3dB, as  600W distributed over 2 identical 8 Ohm cabs, as in 2 times 300W, theoretically will be the same as 2 sound sources producing the same amount of dB, added to each other equaling an increase of +3dB, and ((X Watt + X Watt) =  2X Watt) = +3dB, as in the increase from 300W to 600W, doubling the power, into an identical 4 Ohm cab also equals an increase of +3dB.

I am aware that this in practice is not actually the case, as you should expect an increased output adding additional speakers, as they will push more air, but as said I very much doubt that doubling the amount of speakers will actually add up to as much as if you had doubled up the amount of watts of the given amp fed into 1 single cab, beside the fact that the increase in output would depend very much on the specific cabs in question and not least what kind of speakers they were actually equipped with. 

Where are you getting those numbers from? 

 

Edited by Baloney Balderdash

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35 minutes ago, Baloney Balderdash said:

However theory says that adding up 2 sound sources of the same amount of dB gives +3dB,

Yes, and then on top of that +3dB I think you get up to another +3dB from mutual coupling (assuming you stack the cabs and point them both in the same direction).

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1 hour ago, jrixn1 said:

Yes, and then on top of that +3dB I think you get up to another +3dB from mutual coupling (assuming you stack the cabs and point them both in the same direction).

So the same as if you had doubled up the amount of watt of the amp into a similar cab of half the load?

I have a hard time believing that can actually be the truth.

Where do those +3dB come from?

Logically it would have to depend on the specific cabs and the specific speakers in those cabs, or else you would get +3dB no matter if you used 2 cabs each equipped with 1 x 5" with a sesitivity of [email protected] or 2 cabs each equipped with 4 X 15" with a sensitivity of [email protected]

Consequently meaning I could  compete with an 8 X 10" cab hooked up to a 200W amp in loudness if I just added 4 16 Ohm 1 x 5" cabs in parallel to my 50W 4 Ohm amp.

And that can't possibly be how it actually works.

Also please read the post you quote from again, I edited it to explain my point a bit more thoroughly. 

 

Edited by Baloney Balderdash

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1 hour ago, jrixn1 said:

Yes, and then on top of that +3dB I think you get up to another +3dB from mutual coupling (assuming you stack the cabs and point them both in the same direction).

 What causes a driver to create sound is cone excursion. What causes cone excursion is volts. A SS amp will deliver the same voltage into any load impedance. When you double the number of drivers parallel wired the voltage pushing each remains constant, the excursion of the drivers remains constant, but the cone area is doubled. That gives a 6dB increase. so long as the drivers are placed less than 1 wavelength apart, which insures that their outputs combine fully. Amps do have a limit to how much current they may deliver. Current also doubles each time the driver count is doubled when parallel wired, so you do have to wire multiple drivers so that their impedance isn't too low, causing current flow to be too high.

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The barefaced 210s are pretty much designed for flexibility rather than volume. The 4-12 ohm switch makes them amazingly flexible.

Having the 4-12ohm switch means you can:

1. Use one cab at 4ohms ("louder" than using the same spec cab at 8ohm).

2. Use 2 cabs at 4ohms each - ONLY if your amp runs at 2ohm. Otherwise DONT do it.

3. Use 2 cabs at 12ohm each = 6ohm.

4. Use 3 cabs at 12ohm each = 4ohm - which is what the majority of solid state or class d will go down to.

Now, if you're only going to run 2 cabs, it does get you thinking on why not just use 2 8ohm cabs? But, dont worry, x2 210s will be more than sufficient for almost any gig, but you always have the option to add a third cab that you wouldnt have if you had 8ohm cabs.

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19 hours ago, Bill Fitzmaurice said:

 What causes a driver to create sound is cone excursion. What causes cone excursion is volts. A SS amp will deliver the same voltage into any load impedance. When you double the number of drivers parallel wired the voltage pushing each remains constant, the excursion of the drivers remains constant, but the cone area is doubled. That gives a 6dB increase. so long as the drivers are placed less than 1 wavelength apart, which insures that their outputs combine fully. Amps do have a limit to how much current they may deliver. Current also doubles each time the driver count is doubled when parallel wired, so you do have to wire multiple drivers so that their impedance isn't too low, causing current flow to be too high.

I hesitate to type this - but is there a typo in this?  I'm no expert and I'm not trying to be a smart-derrière.

Frank.

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10 hours ago, Bill Fitzmaurice said:

If there is a typo I don't see it, but that could be a forest and trees situation. I can clarify anything that doesn't seem right.

Sorry Bill, I was a little bit intoxicated when I posted this last night :)

I just thought that two identical speakers, connected in parallel, resulted in a 3db increase. I absolutely stand to be corrected.

Now, I'm an electrical engineer with well over 40 years experience, but I'm definately not a qualified acoustical engineer, so apologies. And I cringe at posting this. 😕

Frank.

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With no change to the amp volume two speakers parallel wired get a 6dB increase over one. That's because the voltage into each speaker is the same as that into one. The effect is the same as it would be if you doubled the voltage into one speaker. If you double the power into one speaker that's 3dB, but when you double the voltage you quadruple the power.

Edited by Bill Fitzmaurice
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19 hours ago, Bill Fitzmaurice said:

If there is a typo I don't see it, but that could be a forest and trees situation. I can clarify anything that doesn't seem right.

That's a great lesson in how to reply to a question on the internet, lovely response Bill :)

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If you liked that consider this: If a man is walking through the woods and says something, and there's no woman there to hear him, is he still wrong?

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41 minutes ago, Bill Fitzmaurice said:

If you liked that consider this: If a man is walking through the woods and says something, and there's no woman there to hear him, is he still wrong?

There is wisdom there, but I suspect many would argue it works both ways :)

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19 hours ago, Bill Fitzmaurice said:

With no change to the amp volume two speakers parallel wired get a 6dB increase over one. That's because the voltage into each speaker is the same as that into one. The effect is the same as it would be if you doubled the voltage into one speaker. If you double the power into one speaker that's 3dB, but when you double the voltage you quadruple the power.

Thanks Bill for being gentle with me  :)  and for taking the trouble to explain it.

Frank.

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Doesn't that '+6dB' logic only hold true if we were talking about 1x 12R cab being doubled to 2x identical 12R cabs though? I think what's being lost in this is that, if only using one cab, we can use the 4R setting to cheat the impedance/power game a little. 

 

I guess the real question is: what's the volume difference between 600W into a 2x10 and ~400W into a 4x10? Which after all that doesn't really change the answer, it's going to be the 4x10.

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