Carvin BX500: Part II

[nboyer941]

If you ever got a 2nd 212, I'd suggest stacking them vertically so you have all 4 spkrs in a vertical line, giving MUCH more effective sound transmission a la grateful Dead "Wall of Sound"... I've always wanted to try that.

Anybody doing this?

Good god that would be a lot of sound. I'm running one of the gk 212 cabs at 8 ohms and I'm looking to get one more 8 ohm cabinet to total 4 ohms. Not sure what to get yet.

I'm thinkinf 1 15" at 8 ohms.

 

[bass4worship]

Had my BX500 over three months now with no problems and just got the new EpiFunky 210 cab. The sound with the BX500 is just what I been looking for. Light amp and a light cab ( 30 lbs ).

 

[Lippy1]

Sorry if this derails or should be somewhere else, but I was looking at purchasing a BX500 for the light weight and 2 ohm capability. If I have one 4 ohm 1x12 it will draw the full 500 watts. If I hook up a second 4 ohm 1x12 and set the amp to 2 ohm operation, both cabs will see 250 watts (sort of), right? Soooo, would I be gaining much in volume by adding the second cab? I understand the surface area doubled, but with the drop in power I was just wondering...

 

[eli]

...If I have one 4 ohm 1x12 it will draw the full 500 watts. If I hook up a second 4 ohm 1x12 and set the amp to 2 ohm operation, both cabs will see 250 watts (sort of), right? Soooo, would I be gaining much in volume by adding the second cab? I understand the surface area doubled, but with the drop in power I was just wondering...

This question should bring a TON of responses. I asked it some time ago, and IIRC there was no real science behind any of the responses -- most of it was just "dude if U do more area u'll get more sound". I sure would like to have a well-backed response on this question myself.

The only math I know for this is (a) if you double the power into a single source you get 3 dBA increase in SPL, and (b) if you put two identical sound sources side by side you will see a 3 dBA increase over one alone.

Work these two equations together and they say the SPL should be the same either way -- 500W into one or 250W into each of two.

Anyone have anything better than that?

 

[Lia_G]

If u double surface area while holding total power constant, which is what you would be doing, you'll see a 3db increase.

Liam

 

[greenboy]

Work these two equations together and they say the SPL should be the same either way -- 500W into one or 250W into each of two.

Nope. Liam is right.

 

[eli]

I'm no wizard in this area (pun intended), but that's just not making sense to me. Can you point me to an online treatise on this topic?

 

[greenboy]

Look at your (b) - what is your assumption there about input?

(b) if you put two identical sound sources side by side you will see a 3 dBA increase over one alone.

 

[eli]

You've supported *my* assertion. The "two identical sound sources" in this case are two 12" speakers at 250 watts each. Each of those would be -3dB from a single 12" at 500 watts (half the power). Right? So put two 12"@250W side by side, and you get a 3dB increase -- which is the same as the single 12" at 500 watts. Right?

What's the flaw in that math?

 

[greenboy]

So when you have one driver with 500 watts, or TWO of the same drivers with 500 watts, you don't think something has changed that will give ~ 3 dB? Look at it from the sensitivity standpoint alone. You have gained ~ 3dB in actual sensitivity.

 

[eli]

So when you have one driver with 500 watts, or TWO of the same drivers with 500 watts, you don't think something has changed that will give ~ 3 dB? Look at it from the sensitivity standpoint alone. You have gained ~ 3dB in actual sensitivity.

You mean two of the same drivers with 500 watts TOTAL, or 500 watts EACH?

You agree with the assertion that two identical sound sources placed side by side will give a 3dB increase, right?

So you start with one 12" @ 500W, like Lippy1 has today. Add a 2nd 12" @ 500W, and you should be up 3dB from a single 15" at 500W, right?

Yet Liam's assertion is that this is the same SPL as two 12" @ 250W/ea. How could that be?

I'm not being a smartass really, I just want you to show me where this math is wrong.

 

[greenboy]

Carrying your assertion further, then an 810 is no louder than a 110 if both are getting 100 watts.

Again, look at this from a sensitivity standpoint.

 

[eli]

Assuming that each 10 has the same cabinet size, then no, I would *not* expect the 810 to be any louder. Each spkr is only getting 12.5 watts! What does Liam's assertion say about the 810 -- and does that work out to be true?

 

[Richard Lindsey]

Assuming that each 10 has the same cabinet size, then no, I would *not* expect the 810 to be any louder. Each spkr is only getting 12.5 watts! What does Liam's assertion say about the 810 -- and does that work out to be true?

greenboy and liam are right.

 

[eli]

So the 810, which is speaker area doubled three times over the 110, would be, what, 9 dB louder than the 110 getting the same power? I don't believe it.

Still hoping to see a theoretical verification.

 

[Richard Lindsey]

Assuming that each 10 has the same cabinet size, then no, I would *not* expect the 810 to be any louder.

But it would be, because the cabinet as whole gains efficiency when you add identical drivers in sufficiently close proximity. X amount of power into a cab of efficiency Y yields less volume than X amount of power into a cab of efficiency 2Y or 4Y.

 

[Richard Lindsey]

So the 810, which is speaker area doubled three times over the 110, would be, what, 9 dB louder than the 110 getting the same power? I don't believe it.

Still hoping to see a theoretical verification.

No, 6 dB, because you double the 2 to get 4 (+3 dB), then double the 4 to get 8 (+3 dB).

This stuff about adding speakers improving efficiency is well known to speaker mavens. Ask billfitzmaurice, for one. The process can't be infinitely sustained, but it's real. The drivers have to be more or less the same, and they have to be sufficiently close together (< 1/4 wavelength, IIRC), but it's something that can be and has been measured.

 

[greenboy]

No, 6 dB, because you double the 2 to get 4 (+3 dB), then double the 4 to get 8 (+3 dB).

Hey Richard, I did start with one and not two drivers however, so in that case there would be three doublings, 9 dB... I figured that Eli or someone else could see by the experience of being around load-matching tube heads, that easily an 810 cab is louder than a 110 when there is 100 or whatever watts on tap.

It never occurred to me that someone would think that a 110 is just as loud as an 810 or two 410. If only guitarists believed this ; }

 

[eno50]

Ah The battle of the minds....

 

[vinxbass]

I've been reading this subject about speakers and db's for sometime, so my question is how does this apply to the BX500? Just curious.