[PasqualeF]

I am looking at building a set of 3 way mains which have a tweeter, a mid woofer and two woofers for upper bass. Why do people use two woofers? The way they're wired (parallel) would result in an approximate gain of 6db (assuming the amp produces double output at half impedance). Is this done:
1)To make up for a lower sensitivity compared to the mids? 2)Produce more output in that range (mid-bass)?
3)Just for looks?

Thanks for any help

[Michael R Price]

You got all 3! But I would say the main reason is to boost output/dynamic capability - for lower frequencies in the 30-50Hz range that towers are designed to cover, twice as much power handling and displacement can't hurt.

[Brian Bunge]

Also, using something like dual 8's gives you more surface area than say a single 10 but allows for a more narrow cabinet.

[Jonathan M]

All of the above is perfectly correct. The woofer is generally the main efficiency problem in a speaker system, due to both their inherent inefficiency compared to tweeters, and this is compounded by the baffle step. Usually the mid and tweeter need to be padded down quite a bit to fall inline with the woofer. Parallelling two woofers increases the overall efficiency of the system, and at the same time has the other advantages mentioned above: Less distortion, better power handling, more dynamic range etc.

[Jonathan M]

Sorry, Double post - no idea how or why - most bizarre.

[PasqualeF]

Thanks for the quick replies. I was asking because I will probably not use the exact same drivers in my project and was wondering if I will need 1 or 2 mid-basses.

By the way, the tweeter in the design was also padded down. Is this to further offset the sensitivity?

[Dave Milne]

Quote:

I will probably not use the exact same drivers in my project

If you change any drivers from a proven/published? design, you must start over with the crossover. A woofer change also requires re-modeling the cabinet and port (if used).

Quote:

tweeter in the design was also padded down. Is this to further offset the sensitivity

You got it.