[KTS]

I purchased pre-built box’s and they do not have the triangle braces installed in it and none were shipped, no big deal at all. I was just wondering if they are indeed needed? They do have the center dowel braces. My apologies for such a simple question, I was looking at the plans and the show the braces in question.

Thank you, Kelly

[E-Zee]

Bracing adds some resistance against pressure related flex and from transmitting vibrations.  The goal is an inert cabinet that doesn't flex under normal use.  Your included center dowel that bridges across the largest panel will help with that.  Adding corner braces would also help.  The corner braces could be any scrap material that you have available. I don't have the official spec or dimension in front of me but a few strips around 4.5" to 5" at longest length, with each end cut at 45, would be all you need if you want that extra assurance. 

If your able to, I would suggest adding the corner braces.  Even a small handsaw cutting on a pencil line is fine and no special equipment is needed.  If you aren't setup to make those cuts and don't want to ask the favor of a friend or neighbor, I don't think your cabinet will be ruined in any way.  Just enjoy your speakers as is.  Yes, plenty of people here will tell you what the best case scenario/option is, which would be to add the corner braces, but if it's not an option there is no shame in enjoying them as is.

[KTS]

Bracing adds some resistance against pressure related flex and from transmitting vibrations.  The goal is an inert cabinet that doesn't flex under normal use.  Your included center dowel that bridges across the largest panel will help with that.  Adding corner braces would also help.  The corner braces could be any scrap material that you have available. I don't have the official spec or dimension in front of me but a few strips around 4.5" to 5" at longest length, with each end cut at 45, would be all you need if you want that extra assurance. 

If your able to, I would suggest adding the corner braces.  Even a small handsaw cutting on a pencil line is fine and no special equipment is needed.  If you aren't setup to make those cuts and don't want to ask the favor of a friend or neighbor, I don't think your cabinet will be ruined in any way.  Just enjoy your speakers as is.  Yes, plenty of people here will tell you what the best case scenario/option is, which would be to add the corner braces, but if it's not an option there is no shame in enjoying them as is.

Thank you, I will add the corner braces. I appreciate the advice!

[DannyBadorine]

I don't have those specific speakers, but in my experience, bracing is really important and makes a huge difference in how a speaker sounds.  The good thing is that bracing can come in many forms and doesn't have to look good since it's inside the box.  I would definitely add the corner bracing and any other bracing that you can get in there that is close to the original design.