godzilla1978

that may be so for smaller caps, but at one farad and depending on the voltage drop(or current draw because it's a 1:1 ratio) it can take longer than 5-6 seconds. Also caps don't partially discharge, which means it's kinda a one way street(I'm pretty sure i read that somewhere and could be wrong, I'm sure some one will correct me if i am). They use up all of there capacitance then recharge.I don't think i've ever seen a cap in any SPL or SQ competition. I agree though that because of the fluctuating demand of music they are pretty much useless! I only have one cause I like the pretty lights and the voltmeter that's on it! They do have one use that i can think of, if any AC ripple gets past your battery, a cap should clean it up!

gtabmx

OK, so after some thinking and more planning here is my final setup, taking everyone here (as well as other sources) opinion into consideration.

I am not changing the battery or alternator.
I am not changing the head unit.
I returned the cap, so I am going capless.
I have 4 Pioneer TS-A6872R 6"x8" speakers (at 40W rms each, 4 Ohms).
I have one 12" Pioneer TS-W308D4 subwoofer (Dual 4 Ohm VCs) wired in parallel to 2 Ohms.
I have an Alpine MRP-M500 (500W rms @ 2 Ohms) amp for the sub.
I have an Alpine MRP-F300 (50W rms x 4 @ 4 Ohms) for the speakers.
The battery to MRP-M500 will be gauge 4 wire and the leads will be extended to the MRP-F300 with gauge 8 wire.
Speaker level inputs from head unit to 4-channel amp.
RCA pre-out from 4-channel amp to sub RCA in.

The system's total RMS power is about 600W rms (maybe at most pulling 750W rms due to inefficiencies). And that's at the max, which I don't expect to be listening to music at that level most of the time, so I honestly don't think my current setup warrants me doing the big 3.

As for the enclosure, given that I now only have one sub and thus more usable cubic feet per sub, I am deciding between a vented/ported or a 4th order. The maximum volume I have after taking into account wall thickness (but not taking into account driver/basket displacement) is 70L (sorry for metric, but this is a Canadian board after all), which is still theoretically more than enough.

So far, with some tweaking, the 4th order design will give me 3dB more @ 50Hz than the ported, but the ported design's bandwidth is nearly double that of the 4th order design (crossing 0dB at 27Hz and 138Hz). I still have some tweaking to go and I will try to see if I can maintain a good bandwidth and 30Hz to 50Hz dB rating while shaving off some volume.

Also, I would be welcome to some suggestion for port tuning frequencies and advice as to whether tuning below the Fs is an issue in a enclosure (the general consensus on such discussion boards is that it isn't).

Thanks for all the help,
Mike

DeadlySones

iTrader: (4)

Completely wrong... it takes about +3dbs to notice a difference to your ear. It takes approx. +10dbs to be noticeably "twice as loud."

Much closer to reality.

When I went from one sub to two, I only gained .9 at first. After testing and tuning I went up 2.4db's and some of that was more power due to a different load.

The +3db rule NEVER actually happens in real life. At least I haven't seen it... just like by adding the Dynamat Xtreme door kit claims to get you +3db's... NEVER going to happen...

RomanticMoments

Realistically, any additional load can warrant the Big 3.... The factory electrical is designed for the factory loads in a vehicle. At your 600w rating, you can do some simple math and find out you are adding around a 42 amp draw to the electrical system. Add that to night driving in the winter, for example, and you will find dimming lights and all the rest of the symptoms of an overworked electrical system. The alternator is usually first to die in this war. Who knows... Maybe I'm just crazy

DeadlySones

iTrader: (4)

The big 3 is one of the most cost effective upgrades anyone car do.

gtabmx

I guess that's why they call it the big 3. I don't know much about car parts; how much would this big 3 cost on average? What am I looking at in terms of the price of a decent battery and alternator? Also, how does this all effect gas mileage? I'm sure the higher output alternator and larger capacity battery will cause the engine to have a larger load, and thus use more gas.

Also, while I'm here, can anyone tell me what to do if winISD tells me my con excursion will be about 190% the Xmax at 20 Hz? I need to finish designing this cas so I can finally build it and actually enjoy the sound.

-Mike

veeman

iTrader: (3)

1. big 3 will cost you about $20-40.00 (depending on what you buy, you need about 10ft of 4awg or 0awg preferably, and some ring terminals), do a search as I think mbr YULI had a great tutorial on how to do it.

2. battery and alternator can get expensive, but your system does not need it yet...when it does, then you can price it accurately based on what you need. Just to answer your question...100-250 for a battery, 250-500 for an alternator. The milage change is negligible as the system isn't constantly under load...and high output alternators are really only high output when the rpm's are up and only when needed...when there's high demand for power.

3. if your cone excursion is too high at 20hz, that's normal, you'll want to incorporate a high pass filter to control over excursion just below the box tuning frequency, so basically set the "subsonic" or infrasonic(correct term) filter just below your tuning frequency and the excursion will be under control.

gtabmx

Well, in winISD, I set the EQs for a 200Hz Lowpass and a 15Hz highpass (the subsonic filter that the Alpine MRP-M500 has built in) and the 190% excursion at 20Hz was after those filters. Without them, the excursion hits 190% at 20Hz and remains at that level down to 0Hz. Obviously there won't probably be any signal in the audio source below 20Hz (and even less after the amps highpass subsonic filter) so perhpas its fine. However, In order not to go over the Xmax on the next opeak, at around 50 or 60 HZ (I don't remember as I am at work and have the graphs on ym PC at home), I had to give the sub and input of 250W rms, even though my sub is capabale of 400W rms, and my amp 500W rms. I feel like the Xmax is limiting the use of my equipment.

-Mike

veeman

iTrader: (3)

200 hz lp is too high and 15 hz subsonic is too low to be effective. Does your head unit have a crossover? Assuming your box design is reasonable and tuned to reasonable frequency, then you'll have to live with it and understand that below the box's tuning (asuming this is a ported box) that the cone becomes unloaded and can therefore over excurt and be damaged mechanically if over powered (that can be with less power than the woofer is thermally capable of handling which is what you're noticing with the simulation on winisd). Now keep in mind that before subsonic filters, and fancy speaker design programs, people were building boxes and playing music and for the most part it all worked fine...you just have to know the limits of your equipment and how to recognize when it's at that point.

godzilla1978

it's really some of the best money you'll spend. Let's not forget that 600rms is really quite a bit for the average person. Easily 10x the power in a normal stock stereo, and nearly 1 horsepower worth of electrical power. In order to maximize every little bit of electrical energy you must have the capactity to deliver that type of current. If you don't something's gotta give. About the gas mileage, it would actually improve if you upgraded the alt and battery. The improvement would be minimal, but improvement none the less. If the alt is taxed and is constantly charging the battery that will use more gas than if it doesn't have much to do. Not to mention the effects of having an ignition system that's starved of current. A weaker spark means less efficient burning of the gasoline, and that's just 2 reason's. There are many more!