Do Soffits Need to go to ceiling?

bassman · Post by **bassman** » Sat Oct 23, 2004 3:48 pm

Just curious if soffits need to extend all the way to the ceiling to be effective. I have a sloped roof and the soffits wall would be about 12 feet tall in the current design. Wondering if I could stop at 10' and seal the top, making a sort of shelf?

The bezel only needs to be 4-5x the diameter of the woofer, right? I'm using Mackie's and 10' is surely enough. Since the soffits do not need to be sealed, I could vent the hear (from the built in amps) out the top maybe?

I'm trying to visualize the whole thing and just trying to make the constrution as simple as possible. If I go to the ceiling, I'm gonna have compound angles between the soffit and ceiling. could get real tricky for a novice carpenter like me. A straight wall I can do.

-bassman

knightfly · Post by **knightfly** » Sun Oct 24, 2004 9:51 am

Actually, the distance from the CENTER of woofer to ANY edge of the bezel should be 4-5 times the woofer diameter; and the woofer should be off center in either axis by a slightly different distance to avoid possibly getting the same freq range of diffraction effect in any two dimensions.

For example, 8" woofer means about 40" from woofer center to each edge; if you offset the speakers so this is 1-2" different sideways, then offset vertically so it's 3-4" different at top compared to bottom of the bezel, any diffraction at the edge of bezel would happen at different frequencies... Steve

Arthur Rice · Post by **Arthur Rice** » Tue Oct 26, 2004 1:42 pm

8" woofer means about 40" from woofer center to each edge

Hmmm... Steve do you mean the soffit needs to be 80 inches wide total? Sorry if this is a dumb question but maybe I'm just reading it wrong. Thanks.

knightfly · Post by **knightfly** » Tue Oct 26, 2004 4:52 pm

Yes, this would be ideal; I'm not sure just where this starts to be serious, but as you narrow the flat area around the speaker (the total baffle area, in other words) you start to cause a "horn" effect, which narrows the propagation pattern of the speaker - this will eventually narrow the effective "sweet spot".

I know that following this concept would make the bezels for 8" woofer speakers nearly 7 feet wide (each), so not everyone will have enough room to fully follow the recommendation...

I think that the main thing here is to remember that there are reasons NOT to make baffle extensions too small, so we don't "paint ourselves into a corner" by forgetting that the effective baffle needs to be as wide (and tall) as we can make it, and that 5 diameters is the "holy grail" - the closer we can get, the less effect on the sweet spot.

Remembering this might, for example, keep us from "using" that "un-used" space for a door, or a shelf, etc, when it would better be left flat in the same plane with the speaker... Steve

Sen · Post by **Sen** » Tue Oct 26, 2004 9:15 pm

This "rule" used to give me headaches but not anymore.It's just not possible to build such soffits within the CR I'm planning. In fact,nearly within any room with a window between the speakers which have 12" woofers

.I can't recall seing a professional studio with such wide soffit baffles

going by this "rule" the mixing position in a WELL SIZED control room would end up at the back couch (following the equilateral triangle rule).
So it is a very hard rule to follow and I'm pretty sure you could get your monitors pretty "truthful" sounding without implementing the rule completely..
just 2 cents

knightfly · Post by **knightfly** » Wed Oct 27, 2004 3:48 am

Exactly, Sen; as I pointed out, this is more of a guideline so we don't make drastic mistakes - it's better to know the "rules" and their reasons so we know the possible consequences of ignoring them, than to be "blindsided" by a decision based on something like ergonomics that turns into an acoustic problem.

In fact, I saw one noted manufacturer who makes a "portable environment" package that PURPOSELY turns ALL your speakers into horns, in order to focus on a small "sweet spot" - don't remember which one, but it was one of the big ones... Steve

Arthur Rice · Post by **Arthur Rice** » Wed Oct 27, 2004 5:46 am

Thanks so much for help on this, so here's my situation, I'm using Event 20/20 bas monitors. With my slat resonator walls at just 6 degrees and my glass doors it only leaves room for my soffits to be about 40" in width but I could go about 7' high. Do you think I'd be wrong to soffit mount them or would I be better off to just free stand them and treat where I would have put the soffits. I know it may be best guess but I'm just trying to avoid a lot of work if I'm not going to benefit anything but a headache from it. You haven't steered me wrong yet so I value your oppion, thanks.

Arthur

knightfly · Post by **knightfly** » Wed Oct 27, 2004 10:02 am

Arthur, it's almost always true that even a bad soffit beats a good free-standing; even a narrower bezel will do tons less damage to a sound field than all the cabinet edge diffraction, extra dose of early reflections, etc, that free-standing monitors cause - I'd go for it, and just maximise the flat area as much as possible.

You may find that (if those slats are beside the mix position) the 6 degrees per doesn't fix early reflections from the sides; if so, you might need to add some squares of 2" 703 at the first reflection points (mirror trick) on top of the slats. There's nothing that says these patches of absorbent can't be rotated 45 degrees if it looks better against the slats... Steve

Arthur Rice · Post by **Arthur Rice** » Wed Oct 27, 2004 12:18 pm

Thanks man, boy it seems a vicious circle, more angle, less bezel, more reflections, too live, too dead, sometimes I think I'd been better off to just slapped up 4 walls and built traps and for gone all the astetic crap. Oh, well maybe in a month I'll look back and laugh... or cry

Can't thank you enough for the help.

Arthur