Basic question on OB

[oon_the_kid]

Hi,

I am planning an open baffle with the SEAS FR22 full range with a extra woofer.

There are a few things I would like to know?

1) Is there a minimum distance from driver back to wall? Is there a recommended this?

2) For an open baffle, if I have additional fold/wing to the baffle at the sides that is perpendicular to the front baffle, to make it look somewhat like a 3 sided box, does the bass response go lower, as if it is wider baffle?

Thanks ahead,

Oon

[gooki]

1, yes, 1 to 2 meters.
2, yes, wings create larger baffle.

What you a building sounds like a u-frame open baffle. Google it to see its effects.

[a_tewinkel]

Please note that with wings, you create a resonating pipe with one closed end. In theory the resonance would be 1/4 lambda, although in practice it is lower with relatively shallow U-frames. See Frontiers . Also, front-back symmetry will be slightly diminished at higher frequencies.

[oon_the_kid]

Originally Posted by gooki

1, yes, 1 to 2 meters.
2, yes, wings create larger baffle.

What you a building sounds like a u-frame open baffle. Google it to see its effects.

Hey,

Now I know what it is called. U frame.

Is there a reason why there needs to 1~2m from the wall. Still trying to understand the physics of the problem. What are the consequences of it being too near the wall? My primary concern is mostly the mids, will be using something else for the bass....

Many thanks.

Oon

[rvsixer]

How open baffles work (go to downloads section):
Dipolplus

You might want to revisit using something else for bass, OB is oh so nice for that .

[454Casull]

Originally Posted by rvsixer

How open baffles work (go to downloads section):
Dipolplus

You might want to revisit using something else for bass, OB is oh so nice for that .

OB bass costs more (sometimes much, much more) for the same SPL and distortion.

[badman]

Originally Posted by 454Casull

OB bass costs more (sometimes much, much more) for the same SPL and distortion.

Oh, I dunno. The price of one nice Seas 8" that would be sufficient in a box, in some people's rooms, more than pays for a couple of Alpha 15A.


Regarding distance to the wall- you need the time delay for the summation peaks and dips of the reflection off the back wall to be smoothed, and delayed so as to have precedence on the forward radiation. If you wanted to be closer you'd have to start damping the back wall.

[oon_the_kid]

Originally Posted by a_tewinkel

Please note that with wings, you create a resonating pipe with one closed end. In theory the resonance would be 1/4 lambda, although in practice it is lower with relatively shallow U-frames. See Frontiers . Also, front-back symmetry will be slightly diminished at higher frequencies.

That would explain why most of those baffles are tapered with the shape of the wings a triangle. That would distribute the resonant frequency over a range of frequency instead of one, and would reduce the height of the resonant hump.

So if I were to build 12" wide U baffle with sides that are tapered to the top with a base of about 12", The bass should be more than a 12" wide normal baffle only right? And since it is tapered at the top, it will not have a peak resonant frequency. Is this correct?

Oon

[454Casull]

Originally Posted by badman

Oh, I dunno. The price of one nice Seas 8" that would be sufficient in a box, in some people's rooms, more than pays for a couple of Alpha 15A.

Yes, but not a Beta-8, which would be the appropriate analogue, I think.

[badman]

Originally Posted by 454Casull

Yes, but not a Beta-8, which would be the appropriate analogue, I think.

Naw, 'cause a pro-style 8 doesn't dig deep enough for home use.