Understanding Sub-woofer SPL

[STIchris722]

I am in the process of designing some PA sub-woofers and I am not understanding the results that my modeling software is spitting out. With one (1) B&C 18TBW100 in an 8ft^3 cabinet tuned to 38Hz, I am hitting 129dB @ 50.7Hz. If I make a cabinet with two (2) 18TBW100 in an 16ft^3 cabinet tuned to 38Hz, I am hitting 134.8dB @ 50.7Hz. I always thought (and forgive me if I'm wrong), that every time surface area is doubled, there is a 3dB gain. Should I not be doubling the input power to 3KW when using the two (2) speaker method? I feel as thought I am missing something very simple here and need a sanity check from my fellow members. Any help would be greatly appreciated!

[STIchris722]

Post them on my forum. Thanks.

Done. Thank you

[billfitzmaurice]

I tried to send you a PM, but it wouldn't allow me to. I have some questions regarding a set of Tuba plans I purchased from you.

Post them on my forum. Thanks.

[STIchris722]

Because bigger and more expensive is always better, and in the words of a high end cable executive, 'As long as people are stupid enough to buy what we're selling we'll keep selling it'.

I tried to send you a PM, but it wouldn't allow me to. I have some questions regarding a set of Tuba plans I purchased from you.

[billfitzmaurice]

why would anyone purchase a 21" over an 18"? !

Because bigger and more expensive is always better, and in the words of a high end cable executive, 'As long as people are stupid enough to buy what we're selling we'll keep selling it'.

[STIchris722]

So I contacted a B&C rep and they told me that the reason a 21" speaker doesn't have anymore output than an 18" is due to the additional mass of the cone being moved. If this is the case then why would anyone purchase a 21" over an 18"? I have been so intrigued with the 21" speaker because of the Tim Allen tool time mentality of bigger is better, but after modeling them, they look terrible. I can post some pictures if anyone is interested, but so far this B&C 18TBW100 is kicking more butt than anything else I can model. If someone could shed some light on this I'd appreciate it. Cheers!

[filmslayer]

That looks outstanding. What is it tuned to? Does it sound good? I like the design!

IIRC it was a couple years ago . it was tuned low 20's and could handle 3600w before X-max became an issue . the sound was clean and amazing . not a cheap though .... https://www.parts-express.com/bc-21s...4-ohm--294-689

[donradick]

What is this supposed to mean?

Wayne's World - a comedy sketch on Saturday Night Live with Dana Carvey (as Wayne) and Mike Myers (as Garth)
The proper response is "rock on Garth!"

It means, have fun, enjoy yourself.

[Pete Schumacher ®]

What is this supposed to mean?

Wayne’s World

Party on Garth

[STIchris722]

You're comparing a top shelf driver to a mid level driver so they're not really in the same ballpark, even a Definimax doesn't compare to the B&C when it's being pushed. Have you modeled the 18TBX100? I'm also seeing 5.5 cu/ft per driver as the optimum for power handling.

Paul -- That's precisely why I am asking the question. I know nothing about B&C and wasn't sure if their price point was due to being imported from Italy rather than being produced in the US such as Eminence. I am going to model that driver per your recommendation. Thank you for the advice!

[STIchris722]

i've not heard any of B&Cs 18's , but this is Jbrunner's B&C 21 in 13^3ft . it was amazing !

That looks outstanding. What is it tuned to? Does it sound good? I like the design!

[STIchris722]

Fair enough, rock on Wayne

What is this supposed to mean?

[Paul O]

I am designing a set of 18" PA sub-woofers right now and am torn between the Eminence KappaProLF 18" vs the B&C mentioned earlier.

You're comparing a top shelf driver to a mid level driver so they're not really in the same ballpark, even a Definimax doesn't compare to the B&C when it's being pushed. Have you modeled the 18TBX100? I'm also seeing 5.5 cu/ft per driver as the optimum for power handling.

[filmslayer]

i've not heard any of B&Cs 18's , but this is Jbrunner's B&C 21 in 13^3ft . it was amazing !

[donradick]

I appreciate the advice, but I don't have any interest in horns or scoops. I don't care for their directivity and complexity in construction. I will not disagree that you can get a lot of output out of a horn with a small speaker, but I don't care for the response curve or directivity. This is not a slam on Bill or anyone else that uses these products. I simply prefer direct radiating.

I am looking for some advice on driver selection at this point.

Fair enough, rock on Wayne