weak bass, sub or amp?

Systems

I just installed my c300.2 and it is running 2 12" inch alpine type s subs in a sealed box. Granted, I haven't done any fine tuning yet, but it just seems like the bass output isn't as good as I thought it would be for 2 12"s. I have the pre eq on, (not sure if that's good or not). I think I read in a different thread that someone said the pre eq sucks on this amp. I'm running the subs in series/parallel with a final impedance of 4 ohms and the amp in bridged mode. Is there anything different I can do other than just messing with the gain? Thanks in advance for any input.

PolkThug

I thought the pre-eq setting was more for when you're hooking up Polk mids and tweets. Just use the bass management in your HU.

When you turn off the pre-eq, do you get your bass back?

PolkThug

Also, what vehicle is this in? Is the box in the trunk? Which way are the subs facing?

neomagus00

the pre-eq on the 300.2 adds a bump at 45 Hz, so that's not it...

i'm assuming your subs have dual 4-ohm voice coils? if so, then your wiring is fine, if they're something else that could be the issue...

try using this tutorial to set your gains properly...

PT - the pre-eq button you're thinking of is on the 400.4, and on that amp it does precisely what you think it does

PolkThug

Originally posted by neomagus00

PT - the pre-eq button you're thinking of is on the 400.4, and on that amp it does precisely what you think it does

Yep, I acutally own both of those amps but haven't got to hook them up yet.

The wiring configuration on the subs could be wrong, DVC's are a little tricky....

Systems

The subs are dual vc. I'm sure I have them wired correctly. The subs are in a 2000 maxima. They are up against the rear seat facing towards the back of the trunk. The box I put them in give each sub 1 cubic foot of space. Recommended size is .8-1.7, so I think I should be fine there. So it looks like it's ok to have the pre eq on. I'll just mess with the gains, if that doesn't work maybe I'll try some other subs. The c300.2 should be strong enough to run most subs when bridged to mono right?

PolkThug

It should be enough. Your box position is perfect.

Just to double-check:

MacLeod

The wiring configuration was my first thought as well. You say youre sure you have it correct but just to double check, the only way you can get a 4 ohm load would be if they were dual 4 ohm VC subs. Wire both VC's in series and youve got 8 ohms then wire those in parallel bridged and youve got 4 ohms.

My other thought was its just not enough power. Alpine subs usually handle a good bit and youre only giving them 225 each. That aint much.

Another though is to experiment with the box placement.

With the subs facing the rear of the trunk you can get a lot of cancellation from the waves bouncing back off the trunk lid. Try turning the box with the subs facing the rear seat and see if that helps any.

Systems

The subs are dual 4 ohm, and I have them wired just like the attached diagram. Maybe I will try facing them toward the front. They seem a lot louder when I am trying to mess with the amp and the subs are facing me. It could also be that I am just expecting too much out of a sub that is sealed up in a trunk. I miss the sound I used to be able to get out of my integra hatchback. I will try to get my hands on a good cd for setting gains and mess around with my set up this weekend.

1996blackmax

From my experience, having the speakers facing the back of the car provides the best results as far as output. Try reversing the phase on the subs to see if that helps. To do this just reverse the connection on the speaker outputs.

Systems

reason why rear-firing normally works best is because front-firing subs have bass cancellation between the notes entering the cabin and the ones that enter through the rear deck. so its either you aim it at the rear, then if its a huge box it blocks the trunk pass through, so all the bass goes up through the rear deck, or fire it forward but make sure the deck is covered with sound-deadening material. well, at least, among the explanations I've heard that's the most logical.

Now, about the amp and subs. can I assume that you want to keep things simple, with tight, accurate bass, not just outright volume, (so ported may not be a good idea, and an ABC box is definitely out of the question). Id agree with MacLeod, the subs are definitely not getting enough power. they're getting 225 watts each, but that's at 14.4volts. even in perfect conditions the power will not be enough. That's why it's best that amp rms power output is 20% over the speaker's rms rating. Either you get a 700 watt amp for both subs, power just one sub. Ive heard a lot of systems with just one amp

If you are willing to complicate things a bit, Id suggest putting em in a ported box (make sure the chambers are separate).

Meeks32

Just leave your rear seat folded down unless you use your backseat alot. I notice a big difference when I do that, but I have a 240sx so I never use my backseat anyways.

PolkThug

polknewb wrote:

It could also be that I am just expecting too much out of a sub that is sealed up in a trunk. I miss the sound I used to be able to get out of my integra hatchback.

Bingo!! I went down this same path. Start looking for ways to let more sound come through the rear deck.

1996blackmax

I get really good bass response from my single 10" subwoofer. It is now connected to an MTX Thunder801D at 4ohms (birth sheet states it puts out 597 watts RMS at 12.5 V @ a 2ohm load), so it is getting close to 300 watts RMS right now. I had a Kicker ZR240 with about the same power before. My sub is in the left rear corner of my Maxima (driver's side). For a comparison, it does not get as loud as my older setup which consisted of a Kicker 12" L7 and a Kicker KX600.1 (rated at 740 watts RMS), but the bass can definately be heard and felt inside the car (all of my mirrors get to vibrating if I turn it up loud enough). Play around with the location of the box. If I am getting good response out of my 10" sub, you should be able to get good response out of your system. Granted my sub does have 20mm of one way linear excursion, but you have 2 12" subs which you are powering with a little more amplifier power than my setup. You should be getting louder than me.

1996blackmax

By the way, I have a trunk pass through thing but I never use it. My little one's car seat is in front of it.



Right now my sub amp is not being used to its full potential. In the near future I will be getting a 12" dual 4 ohm Sound Splinter RL-p, that way my Thunder 801D can get a little bit of a workout . I think this setup will be a little louder than my L7 and KX600.1 setup . It will have a less power, but the sub will move a lot more air, it has 24.2mm of linear excursion :cool: .

Meeks32

I doubt the soundsplinter will get any louder than the kicker since the square cone has more surface area & offsets the excursion difference. But I would still trade in the kicker for the soundsplinter, SQ over SPL anyday.

1996blackmax

The 12L7 had around 12.4mm of linear excursion. The RLp-12 has 24.2mm of linear excursion. I do not think that the L7's slightly bigger cone area (around 20% bigger) will offset the diffence in the amount of air the RL-p can move.

Meeks32

Sorry, just glanced over your post & thought you were saying the L7 had 20mm of excursion. Kicker doesnt post their t/s spec's on their site so I dont know how the l7 is.

1996blackmax

No prob . My 10" Sound Splinter is the one with the 20mm's.

neomagus00

ah, yes, 'there's no replacement for displacement'... although, it can be shown that if the displaced volume of air is the same for 2 subs (i.e. Sd times xmax), the sub with the bigger cone and smaller xmax will sound better (all else being equal, of course - you can't do this with a 18" and a 8" sub, that's not fair... you have to compare 2 12s or the like...

at the extreme, the bigger the sub, the lower it can reach, no matter how much xmax the smaller sub might have...

and i'm fairly confident that this post is entirely irrelevant, so feel free to ignore me, as usual

Systems

It looks like I might end up changing my setup. The two 12's are just too big and heavy. I am thinking now of a single 10 or 12 jlw3. I was even maybe thinking of a single 8" firing through the rear deck where the bose sub usually sits. It would take a little work, but I might get the best results from that because the sub with be firing into the same air space as the passenger cabin. I guess it's time to start searching ebay for a good deal again.

neomagus00

a single 8" sub is simply incapable of getting the low notes that a pair of 12s can grab with ease... you may find that a single 8 is insufficient after what you're used to... consider the 10, and don't consider jl . too expensive for what you get... you may wish to check out pioneer's shallow subs - they're about 4 inches thick and are supposed to sound pretty good...

MacLeod

There is absolutely nothing wrong with JL. Ignore the bandwagon JL haters.

Neo is right that an 8 probably wont fit the bill. They are good for a setup in which the sub will be in the cab with you but they just dont have enough balls to get the low stuff.

At least go with a 10 but for the trunk I prefer 12's.