ok, i know thisis goin to make for biased draw... but i recently installed a powerbass single 12' 600 watts in a sealed box. a Volfenhag 800 watt mono block amp.
thats it, ive been ther done that on the bigg boom setup, this one is to enjoy my classic rock to my little john tunes. the question is this: i see more bandpass boxes in 850s on this site, mines sealed and when the seat is down it hits tight, when the seat is up its not a dynamic. i want the most bass for the power i have. and sould i poly fill my box... its not right now......
and the power, do i need to upgrade the battery, get a power bank, or a 2nd battery?
HELP!!!! :o

I assume you have a sedan, with the situation you express.
There will basically always be a difference in the bass when mounting a box in the trunk, between rear seat down or seat up. You're basically enclosing a sealed box in a sealed box. With the seat up you are creating much more pressure and "drag", of sorts, on the subwoofer (not to mention the large baffling effect of the rear seats...cloth seats will allow easier transfer of the sound than leather, but that's really neither here nor there at this point). With the seat down, you create a very minimal effect of a port and direct transfer of the bass into the cabin, which will of course create the effect of louder bass and with a much more "punchy" and unmuffled sound. This is a hard situation to correct without some modifications to the car itself.

You can make an opening in the rear shelf to allow a direct connection bewteen the trunk and cabin. Most who do this will simply cover the hole (holes) with a mesh speaker grille to hide what it is really for.

You can get rid of the box and use free-air subwoofers mounted directly to the back of the rear seats. Proper choice will also allow for you to port the trunk (as mentioned above) and even better tune the sound.

Basically, the problem is that you are trying to listen to your bass through a wall, as I expect you don't always want to have your rear seat down. If that doesn't matter than the easiest solution is just to leave the seat down (or center section only if you can).

As whether or not to Poly-fil? Thats up to you. You reduce the air volume in the box when you do this...is the box specifically designed for the subwoofer or did you just mount to subwoofer in a pre-made (empty) box? If there were purchased as a single unit, then I would leave it be. If not, then determine what the optimal volume for a sealed box is for your subwoofer and compare that to the volume of the box. Another thing that makes a difference is if the box is square (or rather, is the from surface, with the sub mounted to it, parallel to the rear surface)? Preferably, you do not what them parallel or you just create forces directly in opposition to the subwoofer. Poly-fil can help eliminate some of this with marginal effectiveness.

More power? That depends on your situation, Quality of OEM components, and efficiency of your equipment. I know nothing of Volfenhag, so I cannot speak for their efficiency. I would drive around for about an hour, while listening to your system as the volume level you normally use (or maybe a slightly bit higher), with your headlights on. Check your battery voltage prior to the drive and after the trip. Is the voltage still acceptable or has it been drained somewhat? Do your headlights flicker with the bass? If it has drained, then just adding a second battery really isnt the solution as your alternator simply cannot keep one battery charged properly, so dont expect it to charge 2 batteries. It basically means the alternator cannot keep up with the pull of current, and as such will lessen it's lifespan. A higher power alternator would be preferred in this cas, but good high power alternator are not generally not cheap (about $400-$600+ for a good one).

Power banks or Capacitors only serve the purpose to help provide the initial punch power of a subwoofer (via the amp of course), but does not relieve the stress on the alternator. With your setup I doubt such a setup would prove to be worthwhile or noticable (except lightening your wallet a little).

Basically you need to know the amperage usage of all your components. Generally, your alternator will have an output rating slightly over all needs of the stock vehicle. You then to need add the amperage drain of your system (amplifier mainly) to that and determine if your OEM alternator is designed to put out that much or not. If not you should match it with a higher power alternator that will match the necessary drain, and then you should be in good shape with only needing the one battery.

If you have an issue of draining the battery due to the stereo system (down to where it intereferes with starting the car or other problematic low power situations), and do not want to get a better alternator, then I would suggest putting a system in line with the amplifier that will cur off it's power when the battery power goes below a certain point, and then turn it back on when it charges back up.

(a system in line with the amplifier that will cur off it's power when the battery power goes below a certain point, and then turn it back on when it charges back up.
)
wher do you get a system like this? is it a powered relay? that would seem to be a good idea, till it pops the woofer, unless it has a soft on feature? im confused.
i put a 700 watt kenwood amp, kac-7295, and the woofer in a sloted box... lots more deeper bass, cleaner bass. i leave the armrest access door open, hits great. plus, i found out the woofer was wired at 2 ohms on a 4 to 8 ohm amp, causing large power draws, i corrected the wire issue. the draw stopped. ?
:unsure:

As for the voltage regulation system, you can do a simple homemade version with a couple of components. Basically you need an voltage relay to monitor the system and drop the amplifier out of the system when the voltage drops below a certain specified point. To help prevent the cut-off "pop" you can use a decent sized capacitor after the relay (between the relay and the amp) so that when the relay cuts off the power the amplifier charges down more slowly by sing the remaining power from the capacitor.

As for the subwoofer ohm rating. 2 ohms should be perfectly fine for the amplifier. However, is the subwoofer a dual voice coil or single? It is fairly common for many subwoofers to be 4 ohm rated but actually have a pair of 8 ohm voice coils on them. Generally you dont want to rewire the stock wiring of the voice coils, but if you do and it still works, then no problem. If by chance it was a 2 ohm dual voice coil (two 4 ohm coils in parallel) and you reverse it to series wiring, then you end up with an 8hm speaker, not 4 ohms. You can safely go higher in ohms in a car (over 4 ohms) but most car systems are designed around the 4 ohm setup, as opposed to home systems designed areound 8 ohms.

Changing from 2 ohms to 4 ohms really doesn't pull more power (so to speak), it just makes the amplifier work harder and heat up faster and sometimes even hotter, but the power draw should remain somewhat consistent. Its the extra heat generation at lower ohm ratings that make amplifiers unstable below 2 ohms (most anyways), as the components aren't designed to withstand the excess heat and will begin to fail.

Generally, a ported enclosure will sound better (to me anyways, others may disagree), as the port allows you to tune the subwoofer. You gain more volume out of a ported enclosure with less power needed to push it, but you also reach the clipping point more quickly than in a sealed enclosure. Which is best for you largely depends on the style of bass you prefer, the volume level you prefer and how much power you put to the subwoofer. Either amp you mentioned should be perfectly fine for either type, what ermains is basically personal listening preference.

Changing from 2 ohms to 4 ohms really doesn't pull more power (so to speak), it just makes the amplifier work harder and heat up faster and sometimes even hotter, but the power draw should remain somewhat consistent. Its the extra heat generation at lower ohm ratings that make amplifiers unstable below 2 ohms (most anyways), as the components aren't designed to withstand the excess heat and will begin to fail.
thats what it did. both amps till i rewired it. the sub has two voice coils, when you hook up the red to red, black to black, and the wires to the amp conventinal it drawed more power. rewired to red to black, red to black, the red from the amp on the red terminal voice coil one, and the black from the amp on the black onthe voice coil two side. that made a differnce in power draw... if you can see what im saying.

Usually dual voice coil subs (or most I have messed with), are already pre-wired between the voice coils to produce the specified ohm rating. I expect some may just have a pair of open connections, but never used any that did.

Anyways, if you got that situation straightened out then great :)

This is an old thread but I will deff put some input into this. I have right now a 6 cubic foot box in my trunk now. I have a 96 850. What i have is a kicker L7 15" competition sub. Im running at 1800 watt 900 watt "rms". RMS is what your really looking at. My sub can support around 1000 watts rms which is like breaking class loud! But anyways You can deff go a lot bigger in the box. As for sealed or not sealed depends on what kind of bass you want.

Do you want the bass that kicks hard as hell or do you want the base that can kick but is less subtle. Right now my box is sealed but thats because i just finished building my box and I havent created a port yet because i got to re calculate the volume in the box and everything. But I like ported because when im on the road EVERYONE can hear my car. And when i mean everyone man its like you can hear me about a quarter mile away.

My sealed box hits lower notes a little better but just doesnt vibrate my car enough. As for my amp I have two kenwood amps a mono d block for my sub and a cheap 4 channel for my speakers trying to save up to finish my entire car.

For my power I have one battery running off of everything. Yes my lights do dim when my sub hits but who cares lol looks cool at night. The only thing i can say to you is unless you dont drive your car a lot then get two batteries because i had some problems when i didnt drive my car my battery died cuse i left my amp and crap plugged in yes there is a very very very tiny drain enough to kill ur battery over time. Oother than that thats all i can say.

Good Luck hope it pounds.

+1 on what blackbyrd is saying there.

I am running both my subs down to 1 ohm each as they have dual 2 ohm voice coils. ... they each have they're own amp, and they are putting around 1500w RMS out each ... you can hear me a mile away at least!

I made a custom box for my two subs, its sealed as thats what type of subs they are, pretty good 1.3cubic feet space after sub displacement. my boot can unlock itself when i turn up the volume.

Back to the power thing. Its dangerous if your system dims your headlights as its also taking power away from critical systems such as fuel control, abs, airbag etc... your not only putting your own safety at risk by it, your putting others too. its not hard to fit a new alternator into the the system, usually on these volvo's they are around 50-80 amps which should be enough.

If it is doing that then your either drivng it insanely loud/hard, or you need to consider a better battery/alternator.

The amps will drain tiny current, but if your going to leave your car for a bit, its always worth taking out the fuse to it or something to save the battery. probably best taking the negative terminal off of the battery full stop as there are other systems in the car that will also drain it over time.

Matt