32 replies to this topic

[Aussierox]

Hey guys, recently I installed some new front speakers and a head unit into my 1997 Ford falcon el station wagon.

If you don't want to read everything there's a summary at the bottem of what i'd like to know.

I installed a JVC head unit with 2 rca and bluetooth which I'm really happy with.
In installed a polk 330 2 chan (75w per channel) amp.
For the speakers I have Polk Db6501 componant speakers (100w rms each).

I would like to get subwoofers installed in my car.

I've decided on getting Rockford fosgate p2D2-12' 400w rms subs in the sealed enclosure but now I'm trying to decide weather I shoud spend $300 and get a 500w rms amp and run the subs 250w each or spend $500 and get 1000w rms amp and run the subs at there full 800w potential? I don't plan to ever have it really really loud since I doubt my speakers will keep up since they're only getting 75w rms each (out of a possible 100w I plan to replace my 2 chan amp later)

The type of music I listen to is
Disturbed
Rise against
A day to remember
Avenged sevenfold
Skrillex
Simple plan
Greenday
Evermore

Basically everything except for rap.


The amplifier

Polk Class D 1000.1 Monoblock amplifier (800w rms at 2 ohms) for $275
http://www.polkaudio...x.php#pad1000_1

But then when someone suggested I get the RF subs I looked into RF monoblocks and Origionally Decided on a prime monobolock (800w rms at 2 ohms)
http://www.rockfordf...x?itemid=120547 for $300

But then I realized a power amp has a lot more "technologies" but basically the same power specs.
So I looked into
http://www.rockfordf...x?itemid=117364 for $500

But Perhaps I would be better off getting
http://www.rockfordf...x?itemid=117363 $200 less than the 1000w version but only does 500w would this 500w be better than the polk or rf primes 800w?

So I'm not sure if I should get a high quallity power RF monoblock that does 500w rms for the same price as the polk class D or the RF prime that each do 800w rms. Basically would I be better off with 500w on a really good amp vs 800w on an amp that apparently isn't so good (I'm not sure I'm just going based on price)

Edited by Aussierox, 04 February 2012 - 05:49 PM.

[shiny_car]

Aussierox, on 01 February 2012 - 07:14 PM, said:

But then someone started mentioning sealed to me and now I'm extremely confused about sealed vs ported.

Properly-matched subs and subboxes that are sealed, will sound as good as combos that are ported. However, all else being equal, sealed setups can be slightly more accurate sounding (ie: lower group delay), and ported setups will be louder and thus 'lower'.

Thing is, the box design depends upon the electromechanical (Thiele Small) specs of the sub, and every model is different. Some subs sound best in sealed boxes, some in ported boxes, some suit either, or something different again.

So, you can either choose a sub, then have the right box built to suit. Or you can decide if you want sealed or ported, and choose a sub that suits. Box design is very important; whilst there can be small variations for each sub, the size of the box needs to be in the ballpark, and if it's a ported box, the size of the port needs to be optimised.

Quote

2 Rockford fosgate P2 400w rms 12' subs in a US Audio competition brand box sealed (looks better than the ones they sell at autobarn although still don't know how great it would be)

Modelling the Polk db1240 sub specs, they do suit ported boxes nicely. But I'd be wanting around 2.0cuft/56L per sub, with a port tuning the box to around 35Hz.

Without knowing exactly what RF P2 sub, I can't model any specs, so I don't know if 'sealed' is the way to go.

Quote

Which amp should I take and what's the difference?

Whislt I haven't used any of those amps, I can only presume the RF T series are built to offer more grunt, and not sag power output under difficult conditions (ie: loud/low subbass); I would expect more dynamic/accurate sound, but it could be marginal or inaudible.

I'm sure any amp would work very well. The prices seem very cheap.

[Aussierox]

Thanks for the reply. I really don't know if I want sealed or ported. I heard my friends sealed today and it sounded good and I've heard the polk ported it also sounded good but without hearing them side by side I wouldn't know the difference :/

Oh sorry I'll post a link to the RF subs (it's an ebay auction) but the subs are either the 4 ohm or 2 ohm models of these. http://www.rockfordf...x?itemid=120415

[shiny_car]

Given your tastes in music, I figure you don't really need super-low subbass (<40Hz), so no loss with a sealed setup. But if you want it really loud, doof doofing down the street, you could go ported.

Otherwise, as you've experienced, a sealed setup is still loud and low enough for most people.

Modelling the RF specs, the P2D212 does suit sealed boxes, but I'd have around 1.5cuft/42L up to 2cuft per sub. You may find that manufacturers often suggest smaller sizes, but this is influenced by marketing because 'small' appeals to buyers better. Sure, they'll work fine in smaller boxes, but they'll be slightly better in bigger boxes.

[Aussierox]

Thanks for the info. I've asked the guy for demensions on the box, LxWxH when he gets back to me I'll post them. Is this enough info to figure out the size and weather it's suitable?

[Aussierox]

Ok the demensions are L77xW38xH33

[shiny_car]

Presuming the box is built from 18mm mdf wood (often are), the gross internal volume will be around 74L/2.6cuft. Not too bad. A little smaller than I would like; smaller = not quite as loud or 'low', slightly peaky/boomy sound.

Generally, sealed setups - esp with 2 subs - can go very loudly as long as the amp is powerful enough.

[Aussierox]

Ok so will the subs still sound good in this enclosure? How much bigger should it be?

Well my amp is going to be the RF power 1000w at 2 ohms amp. Oh also I was wondering do the subs sound better at 4 ohms would I be better with 500w at 4 ohm vs the full 800w at 2 ohms?

[shiny_car]

As I mentioned previously, if building a box from scratch, I would go 1.5~2cuft per sub (42~56L).

It will still sound good. Don't worry about that; the difference is small.

They will perform the same whether they are 2ohm or 4ohm. But with the 2ohm setup, the amp will produce more power, so they can go louder. To achieve 2ohm with 2 subs, each sub will need to be 4ohm (or dual voicecoil dual 2ohm).

[Aussierox]

Alright well if the box will still sound good I'm happy with that.

I think RF only make the p2's in DVC however I am not sure if they're 2 or 4 ohms I suppose once they arrive I'll take them out I assume it says somewhere on the sub what they are?

[shiny_car]

Ah. Then ensure you buy the D2 (dual 2ohm) versions.

[Aussierox]

The subs are apparently the 2 ohm DVC versions. The enclosure has terminals on both sides (one for each sub I assume) but is it possible to wire it up so that you only use one of the terminals to run both of the subs?

Edited by Aussierox, 03 February 2012 - 04:36 PM.

[Aussierox]

Ok So I've decided on the Rockford fosgate p2D2-12' 400w rms subs in the sealed enclosure but now I'm trying to decide weather I shoud spend $300 and get a 500w rms amp and run the subs 250w each or spend $500 and get 1000w rms amp and run the subs at there full 800w potential? I don't plan to ever have it really really loud since I doubt my speakers will keep up since they're only getting 75w rms each (out of a possible 100w I plan to replace my 2 chan amp later)

[shiny_car]

Aussierox, on 03 February 2012 - 12:28 PM, said:

The enclosure has terminals on both sides (one for each sub I assume) but is it possible to wire it up so that you only use one of the terminals to run both of the subs?

You will need to wire the two sets of terminals together, inside the box. One end to the other, joining POSitive to POS, and NEGative to NEG.

Aussierox, on 04 February 2012 - 05:45 PM, said:

Ok So I've decided on the Rockford fosgate p2D2-12' 400w rms subs in the sealed enclosure but now I'm trying to decide weather I shoud spend $300 and get a 500w rms amp and run the subs 250w each or spend $500 and get 1000w rms amp and run the subs at there full 800w potential? I don't plan to ever have it really really loud since I doubt my speakers will keep up since they're only getting 75w rms each (out of a possible 100w I plan to replace my 2 chan amp later)

The extra $200 is well worth it IMO. Even if you won't use all the power, it will have more grunt in reserve, which results in better dynamics. It's like having two different cars, one more powerful than the other: even if you stick to the speed limit, the more powerful one will accelerate better and be more punchy to drive.

[Aussierox]

That's all I needed to hear $500 amp it is however how much better will the $500 RF amp be than the $300 Polk amp just out of curiosity.