Sound bar in a box . . . can't understand dialog.

We have a large credenza in our bedroom that houses the TV, video gear and sound bar (a modest Visio) facing the bed. It's become our favorite movie theater. Think a 4'x3'x8' box with doors on front. The "booming" caused by the interior reverb of the credenza box makes any dialog unintelligible.  Tried moving it out a bit when open (a pain) as well as adjusting out lower freq.s and boosting treble. No luck.  

Any suggestions on something more creative would be much appreciated!

ALERT! Wife is an interior designer so anything that does not fit inside box is not acceptable. 
Thanks. The soundbar is currently connected to the Vizio via the optical link. The Vizio speakers are turned off.  Setup works fine as far as getting signal to soundbar and the soundbar is working. I'm pretty sure I'm dealing with box resonances with my difficulty understanding dialog.
I also have a Vizio soundbar, but luckily don't have any issues with my setup. Great inexpensive soundbars, btw.

I know the soundbar has rubber pads on it's bottom, but get some tiny self adhesive rubber feet, not flat ones, but round ones like this,

Use 4 on the bottom of the soundbar. This will help minimize contact to the cabinet. Also, pull the soundbar as far forward to the front of the cabinet as possible. I would set bass and treble flat and see if the other adjustments, TVOL and TSHD, affect it any. Then try adjusting bass and treble.
I think the soundbar has ports in it.  Block those and you might stop the boom.  You will lose bass.

It really stinks that almost all tv's these days have down or rear firing speakers.  They are all designed for wall mounting. Doesn't Vizio realize that most of us would gladly pay an extra $50 to get a tv with good built in speakers that are front firing.
Sorry to disagree, but I doubt his soundbar has ports. My Vizio is about 1 1/2 years old and it has passive radiators, as did all the ones in that series. Not sure about the very latest ones, but if they did have ports, I doubt he could get to them without some serious disassembly.
I'd be surprised if the Vizio had passive radiators only because they are typically more expensive to produce but I could be wrong, I'm not very familiar with the brand. The only thing I can think would be to put some type of damping material behind the a dark rolled up soft blanket or pillows or something to absorb sound that is bouncing around in the cabinet. Sometimes putting a speaker in a place like that is going to give you that tunnel sound. How much space is around the edges of the speaker and behind it? 
So I did a quick check and no ports, at least not available to mess with (could be under the glued on fabric).

However, I pulled the soundbar out of where it sits inside the armoire (box) and set it about a foot in front of the armoire on a stool.  Dialog seemed more distinct. So one solution for watching movies is to build a way to do that simply, perhaps a fold/slide out shelf.  We're not heavy TV watchers so that's not a major suck.  Just got to be able to make it invisible when not in use. 

The other alternative, I suppose, is to find some small speakers to hang on the front doors so when they open, they swing outside the box. I do have a pair of small B&Ws that are not in use. Then the issue is no center speaker . . . hummmmm.
If your Visio has an HDMI ARC outlet and your TV has one as well, try that. I had the same problem as you with dialog (but for different reasons) and going from optical to HDMI solved the problem. In fact, everything sounds better.

All the best,
Guess you’ll just have to be surprised and wrong. I know for a fact my Vizio has passive radiators. It’s a 2.0 soundbar having 2 - 2 3/4 in drivers and 2 passive radiators. I doubt the owner’s manual is wrong.

If the dialog is distant, that may be the way you have it adjusted. I also think hanging speakers on the doors is a bad idea. As I previously said, it’s best to minimize contact with the cabinet. Center speaker? Does your soundbar have a center speaker? Can you provide a model number of your soundbar or what is it's width? If 28-32 inches, no center speaker.
Thanks. I’ll ck the model number in the morning. I suspect there’s no center speaker since it was sort of bottom of the line. The free standing approach I tried worked somewhat but would be a pain to set up each use. The next rainy day I’m going to try hanging the extra speakers for the heck of it. My reasoning is that this “box” is extremely heavy, ancient hardwood and not very resonate itself. I think the issue may be reflections inside. 

All the suggestions got my brain going, thanks! Time to experiment...which is half the fun😊
Cabinets and wives are the bane of audio and home theater.  Not sure which I hate more, but at least cabinets don't talk. 

"ALERT! Wife is an interior designer so anything that does not fit inside box is not acceptable."

Does your wife fit inside the box?  The box is probably fine, it's your wife that's unacceptable. 

Or get wireless headphones.  They'll sound better and you won't have to hear your wife complain. 

Spend a crapload on a better soundbar and switch it when she's not around.  She'll never notice. 

+1 Erik.  I'd think pillows would be the easiest and most effective solution.  Just make sure they fill your wife's mouth completely. 

Best of luck. 

Try a better sound bar.  You can always return it.  Buy direct from visio.  I love my zvox but it has huge rear ports and a sub that would just rumble in a cabinet.
Re: pillows...Damn, I like that! Will try the experiment.

Re: the wife thing...this is my second pass...don't think I'll try that experiment again.

Re: better soundbar.  Actually, I think this one is dying so may be in the cards.

Cheers, Dan
Soundbar is something I find really difficult to give recommendations for because every one is unique be it size, features, performance and of course price.

You don’t really need to spend $1k for soundbar... There are soundbars with sub for less than $200. But if you can, spend more. Lots of $$$ in soundbar goes into the form factor and home theatre features such that normal speakers can sound as good for half the price. I find myself needing around $1k to get acceptable sound from TV soundbars, and many brands don’t even manage to reproduce proper sound even at higher prices (Granted, these brands, which shall not be named, also do not manufacture either a) AVRs, b) HT speakers, c) literally any proper audio product of any form, hence me concluding that their target customers are the kum gongs)

Cheap soundbar:

At cheap prices really, soundbars don’t give much improvement over TV speakers (unless you’re using those new super slim LCD/LED TVs which have horribad speakers - maybe the cause of cheap soundbars rising?) except mainly for the fact that it has a subwoofer.
I'm surprise the Samsung HW-MS650 isn't on that list with the link.
I've yet to read a bad review on it and am considering getting one myself.

All the best,

Choosing the sound is not an easy to task as so many varieties are available offering different quality, features, and at different prices. A home theatre system has many considerations to look for. And without knowing about them you can’t figure out which to buy.

If you are a first time buyer, we suggest you to have a sound knowledge of the product. It is because then only you can figure out what requirements you want and are they matching the products you are choosing.

You can check this out:

I had a very similar situation. Put my main system in the family room, but in the living room we had a three-wide Salamander cabinet with a shelf going all the way across that had housed a sound bar (Def Tech) in our old house. In the new set up I crammed into this space Def Tech monitors and a center channel speaker.  Only the subwoofer outside the cabinet.  Better equipment than the sound bar, but dialog uniteligible.  First of all it was the room. Old house had a small room and the sound bar worked fine. New house has cathedral ceiling, large room, lot of glass. What I did to fix it was to get sound absorbing foam from parts express, with an adhesive on one side , and put it on the sides, tops and backs of the cabinet shelf. Then fluff designed for inside speaker cabinets (loosely) in the remaining space.  Put the speakers on rubber cones/feet.  This helped enormously.  Still, I find the sound much better directly in front of the cabinet.  Not perfect, but no room for floor stands, wife’s happy, and it’s not my main system anyway.

I sorted out my mother's TV sound with a cheapo Logitech 2.1 computer speaker set. The sub has its own volume control, which makes balancing the sound fairly straightforward.

Personally, I put the TV through my hi-fi, and am very pleased with the results.

I did something similar, threw together a patchwork of left over mini-monitors with an old Kyocera receiver.  The monitors are attached to the doors so they swing out of the credenza cavity and don't excite the volume like the soundbar did.  

or get a panasonic oled tv,,, the whole tv itself it the  speaker panel.
works great and wife friendly. 
Now a days every TV needs a soundbar. You may ask why? Because the default sound system of the TV is not quite enough. There are lots of soundbar in market right now. They are lots of variety in size, price and price. So it is very difficult to choose right one.

Literally you don't have to spend much to get the right soundbar for you. There are some extremely cheap soundbar in market. They aren't good enough to serve your desire. So you have to find one with $200 or around $200. when I am researching I have found a nice guide on it. You can check it also.

Cheap yet premium soundbar:

I have noticed another thing is that some of them offering soundbar with sub woofer which are really good. Thanks for your time.