Set default embed max youtube video resolution

I have responsive video embeds plugin with customizr theme. The twenty twelve theme has a default max resolution set somehow and works prefectly with this. Whats the best way to set the max embed width with the customizr theme?

So what I did since responsive video embeds already wraps the videos with rve I set my css up to use that in my style sheet.

.rve {
	position: relative;
	padding-bottom: 56.25%;
	padding-top: 30px;
	height: 0;
	overflow: hidden;
}

.rve iframe,
.rve object,
.rve embed {
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
}

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