How to fabricate a tight fitting grille

Select Products sells some pretty informative videos on how to make killer custom flush mount grills. But you will need some special tools and materials.

If you want something inexpensive and simple this can be done with basic equipment..

Use a router with a circle guide to make a ring out of 1/2'' MDF...make it slightly smaller so when you adhere the grill cloth or acoustic carpet to it..it will fit snug. And make sure the speaker cone can not touch the grill during high excursion. You want to leave a small "lip" of material that hangs in front of the grill so you have a "pull tab" in event of needed to remove it. This tab can be stapled to an inside edge of the MDF ring. I do it that way all the time and it works great. Use a quality spray adhesive for the material. Spray the ring, and the fabric LIGHTLY..let it tack for a minute..and pull it tight as you wrap it..trim excess with a sharp razor.

In addition I also prime the MDF flat black for cosmetics and to help a bit with moisture..MDF will swell if moist and come apart if wet.

nicely done sir, pretty much exactly what I was going to say.  The outer diameter of the grill ring should be the same as the inner diameter of the flush mount ring and the inner diameter of the grill ring should be the same as the mounting diameter of the sub.  I typically use grill cloth to cover it but you can do some perforated abs or grill metal, whatever is acoustically transparent really.  Be sure you take your time and fab all these rings prior to starting the project so you dont get to the end and have to take some awkward measurements or anything.  And like master said be sure to take into consideration the thickness of the material being used.  Also, I like to round the bottom outside corner of my grills with a router so that it slides in very easily.

Hey master, nice idea with the pull tab, I likes.

Thanks..funny too because after looking closer at the picture of the grill (the one where it is off) you can see it has a pull tab on it as well.

I also found out today that some trunkliner is totally acoustically transparent. I am selling an old POS I had for a while..someone gave it to me in exchange for some alarm work on thier other vehicle...the interior is in decent shape except for the headliner and dash cracks (south florida sun is murder on dashes).

So I fixed the headliner with trim adhesive and made a cheesy dash cover out of off the shelf trunkliner. (well it was free..lol)  I cut the cover perfect..it looks like a store bought but before I cut the speaker openings out I laid it over my dash speakers and gave a listen. No loss in sound quality at all..at least that I could tell...so I figure if mids and highs pass through...sub bass should be a non issue...which appears what was done in the above pics..and what he wants..I say go for it.

Anything is possible my friend!  Well almost anything.  I can't really say how much extra room it is going to take up in your trunk as I don't even know how much room its taking up now.  From the looks of the picture though, that is a pretty beefy box so I would imagine that you wouldn't need to add much more to the design in the way of internal volume, you would just have to change the speaker layout to accomodate two 10's.  Best bet would be to angle them away from each other like 45 degrees so that they are firing away from each other. 

The amp is most likely a class d as it is a mono block but I can't say 100% on that.

I run all my diamond subs in my display room off the d3 amp and it sounds good.

When I do a grille, it's typically made out of 1/4" mdf and since its outside diameter is equivalent to the total diameter of the sub minus whatever material you are using, and the inner diameter of it is equivalent to the mounting diameter of the sub, it typically ends up being about 1/2".  As for the middle sagging, I haven't had any issues with that, just make sure you pull your material nice and tight while making sure you don't warp the ring and you shouldn't have a problem.  Diamond sent me a bunch of the flying d chrome logos so I decided to put two of them on the port grilles of two of the ported boxes I posted on here about.  Looked awesome but it was funny as hell how they would dance around when the sub was playing.