A few questions for a PR box

[gckless 5,000+ posts]

So, I want to get an idea of what would be a good PR setup. Got a bunch of questions. Here is what I have to work with:

This box is for a Subaru Legacy.

About 4.5 cubic feet, minus driver displacement.

Running off a DC 2.0k.

Big 3 done, soon to be a 230A alternator.

I'll start with box design. I would like to build a box with 2 drivers and 1 PR in the middle of them facing the trunk, and one PR on the opposite side of the box facing forward. Both PR's would be centered to cancel out the moving mass. First question is, how would facing the drivers/PR's this way sound?

I'm pretty much set on 2 12" PR's, I'm looking at the TC VMP12's ( TC Sounds VMP 12" Passive Radiator 293-680 ). I would like to use 2 12" drivers, I currently am running a RE SX 12", so only purchasing one more would cut down costs. I know you are normally supposed to use double either the cone area or the Xmax of the drivers for your PR's. The RE's have an xmax of 22mm, which would be 1.7" when the xmax is doubled (xmax is only one way, from rest, travel, correct?) and converted. Since the VMP's have a max excursion of 3.5", would I be ok to use the SX's, or would I need to use 10" drivers?

If I need to use 10" drivers, I need some recommendations on decent ones for around $200 each. They'd be ran off my DC 2.0k, and I am going for somewhere in the middle of SPL and SQ. I do want it to be decently loud, but I would also like something that sounds good.

I really appreciate any help that can be offered. Since I realize this might be a little complicated, let me know if I need to clarify anything!

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[gckless 5,000+ posts]

Anyone?

 

[hispls 5,000+ posts]

I think pointing the PR's one out each side would be best with subs firing to the rear. Porting forward is typically fail, and I suspect PR forward would be similarly fail.

They will move a LOT. I'd say if you wanted to use a pair of 12's a pair of 15" PR's or possibly a single 18" pr may hang, but with 2KW on a pair of 12" drivers I think 12" PRs would really run away from you.

 

[T3mpest 10+ year member]

I've done a few PR setups in trunks before. My last setup was 2 15's with 4 passives. I had 2 facing forward and one on each side.. If I had to do it again, I would say best bet is to do the subs firing rearward and PR's on left and right side of box side firing.. You just have to make sure you have clearance for the motors if you do it that way. I do feel like I had a bit of cancellation in the lower bass frequencies, although that may have been partially since I think my box was too big for my trunk.. However, I'd still stick with side firing and you should be ok with that setup. Your passives shouldnt' run out of excursion as long as you tune near 30 and keep a sharp filter for anything much lower.

Also, you may want to look into creative sounds passive radiators... IMO, they are better passives than the TC sounds all things considered. First off, they are ALOT cheaper, gives you more money to spend on drivers, bigger amp etc. Secondly, they are very durable (I've used them). Third and most important, they are front mass loaded. You unscrew the dustcap to add and subtract weight.. This allows you to change tuning on the fly until you get the exact sound you want. No guessing at what the best tuning is. Use a box modelling program to get you in the ballpark and if it doesn't sound right easily add and subtract weight until it's right. you can go from a burp box to a daily pounder to a pure SQ setup in a matter of minutes using no tools!

Anyway if you want to post t/s for your subs I can model the exursion for you to double check your woofers will be ok...

 

[gckless 5,000+ posts]

I've done a few PR setups in trunks before. My last setup was 2 15's with 4 passives. I had 2 facing forward and one on each side.. If I had to do it again, I would say best bet is to do the subs firing rearward and PR's on left and right side of box side firing.. You just have to make sure you have clearance for the motors if you do it that way. I do feel like I had a bit of cancellation in the lower bass frequencies, although that may have been partially since I think my box was too big for my trunk.. However, I'd still stick with side firing and you should be ok with that setup. Your passives shouldnt' run out of excursion as long as you tune near 30 and keep a sharp filter for anything much lower.
Also, you may want to look into creative sounds passive radiators... IMO, they are better passives than the TC sounds all things considered. First off, they are ALOT cheaper, gives you more money to spend on drivers, bigger amp etc. Secondly, they are very durable (I've used them). Third and most important, they are front mass loaded. You unscrew the dustcap to add and subtract weight.. This allows you to change tuning on the fly until you get the exact sound you want. No guessing at what the best tuning is. Use a box modelling program to get you in the ballpark and if it doesn't sound right easily add and subtract weight until it's right. you can go from a burp box to a daily pounder to a pure SQ setup in a matter of minutes using no tools!

Anyway if you want to post t/s for your subs I can model the exursion for you to double check your woofers will be ok...

Ok, so nothing firing forward. Because of that, I will not have the space to use 12's. I will need to purchase some 10's. To be honest, I'm not set on a PR design, but so far from what I have seen, they are a better option to ported, besides cost.

But you are right about the Creative Sounds PR's. The TC's do look nicer and have a greater Xmax, but I think that's about it.

 

[T3mpest 10+ year member]

Can you a passive on each side of the box