How loud is loud, What DB is actually loud?

Interesting thread.
Mainly of the "who knew?" variety, re: SPLs in a car.

As to the substance of the OP's original question:

I'd propose that he might want to find subwoofer(s) that will produce single digit THD at 95 db (quasi)anechoic - the conditions used for most subwoofer tests - at 30-35 hz. That will allow a safety margin for music, particularly when room gain is considered. There aren't all that many single subs out there that will satisfy this condition - JL, SVS, Rythmik are a few that will do so. A pair (or more) of subs buys more headroom and a wider variety of choices. Once you've found a suitable subwoofer (or subwoofers), your choice of main speakers will be much broader.

If max clean SPL is the main goal, it is the unusual circumstance where you should probably choose a subwoofer first and work backwards to the rest of the system.

Just MHO.

Marty

A Martin Logan can rock out if you want panels. I hit 100db clean at 10 ft. Never tried them louder

01-09-11: Weseixas
The 3 db gain is correct for free space ( anechoic) go ahead and measure your hi-fi system, with speakers l/r and with room gain it is more than 3 db, when you turn off one side from the listen position.

Weseixas, room effects are a separate issue from the contention that I was disagreeing with. The contention I was disagreeing with was that the spl resulting from two paralleled speakers would increase 3db due to doubling of the power supplied by the amplifier, and ANOTHER 3db due to doubling of total cone radiating area.

My contention in response was that total radiated acoustic power would be doubled, resulting in a 3db increase in spl (neglecting any inequalities in the effects of the room on the two speakers). The Stanford paper I cited directly supports that, based on the assumption of "no interference." The paper Frank linked to takes interference effects into account (as distinguished from room reflection effects -- as you may realize they are two different things), and states that on average there will be a 3db increase, with a range between 0 and 6db depending on the interference effects at the exact listening position and frequencies.

Your post that I quoted above refers to a 3db increase as being correct apart from room effects, so I think that we are now essentially converged on that issue.

As far as room effects are concerned, I would certainly agree that inequalities of those effects on the sound produced by the two speakers could change the 3db figure, but not always in the direction of making it larger. Consider the situation where positioning is such that one speaker receives a bass boost due to room effects that is significantly different than the bass boost on the other speaker. Turning off the speaker that is receiving the smaller of the two boosts would reduce spl at the affected frequencies by less than 3db (as averaged over the listening space to account for interference effects), while turning off the other speaker would reduce it by more than 3db (as averaged over the listening space to account for interference effects).

Regards,
-- Al

AL wrote:

The paper Frank linked to takes interference effects into account (as distinguished from room reflection effects -- as you may realize they are two different things), and states that on average there will be a 3db increase, with a range between 0 and 6db depending on the interference effects at the exact listening position and frequencies.

WeSeixas:

Hello Al,

This is what i was alluding to when you measure using a typical 2 channel setup ( hi-fi application ) the localization and summation of both channels lead to 4.5-6 db increase in SPL from the listening position. The 3 db as per previously discussed only applies to free space.

Regards,