You want them in that soffit? It appears to be too close to the wall. I have a soffit like that in my living room that is 30” deep which allows the lights to be 24” deep off the wall. They are approximately 48” on center.

@HALLETT & Co. Thank you for your response. Yes, but I want to know how many downlight (4 inch) should I put on L-box ceiling, for example (as shown in the picture below).

The answer is zero. Your soffits appear to be too narrow. How wide are they?

Your example picture has much wider soffits so that the lights are further away from the walls.

@greg_2015 the wide for l-box is 14", then should I put extra downlight in the middle of ceiling?

If it’s only 14” soffit you can’t put lights in it, far too close to the wall.

Hallett, why the restriction on the soffit width, especially if LED lights are used?

Because when they are that close to the wall you just get scalloping or hot spots. Not pretty. If you want to make that into an accent I would put rope lights in it. Can lights need to be at least 24” from the wall to provide even lighting. Below is a 30” soffit with lights 24” off the wall.

It isn't that you technically can't put lights in that soffit. It's that you shouldn't because it will look bad.

@HALLETT & Co.@greg_2015 thank you for your point of view and advice.