amp questions.

[BrianG]

You will only get the 3Ω load if you use both subs. These are 8" subs and they shouldn't take up too much space in your trunk. I don't know what the recommended box size is but a sealed enclosure for a pair of average 8" subwoofers is only about .6 to .8cuft. That's about the size of a box for a single 10" subwoofer.

Brian, your power calculations are wrong...
If an amp puts out 800w at 2Ω and 400 at 4Ω...
watts = voltage^2 / impedence
800 = V^2 / 2
V = 40

W = 40^2 / 3
W = 533

So if the amp was rated properly, your pair of 8" subwoofers would receive 533w from that amp, or 266w each. This is close to what I am sending my 8" Eclipse subs, and they hit pretty damn hard.

Yeah, I was just guessing. I knew it would be less than at 2Ω, but more than 4Ω - I just didn't want to dig out the calculator.

And, that sub he is talking about is a dual 6Ω coil sub. So, if he uses one, he could wire the coils in parallel fopr 3Ω or in series for 12Ω. Also, he said they were 10's not 8's after all...

 

[chuyler1]

Duh...my bad. I was thinking they were single 6Ω. I was also still thinking they were 8" but I see you have confirmed that they are 10" 800w RMS. So for that amp at least, there is no good way to power both since it won't handle a 1.5Ω load and you will only get 266w total at 6Ω. Powering just one might work at 533w since it is a 10" (and not an 8" as you originally thought).

I still say get rid of them and buy a pair of 4ΩDVC Image Dynamics ID8v3's or ID10v3's. It isn't hard to find an amp that will put out 400w at 4Ω bridged. I know you picked up the audiobahns cheap or whatever but finding an amp that will do well at 1.5Ω or 6Ω will cost more and you're still left with a bad sounding sub. You can get a pair of ID8v3s from www.sounddomain.com for under $200 shipped. The ID10v3s will cost a little more.

 

[mobomelter]

ok it seems that the easiest route for me to go is to sell the ones i have and go with something else. now heres the question. i have 2 of those audiobahn alum10n subs and a box how much do you think i could get on ebay? ok now for the other question what brand would you recommend for 1 nice 10 inch sub? i've heard some jbl's, but i want opinions here. thanks again.

 

[chuyler1]

JBL subs? Who are you talking to? I'd recommend JL Audio, Image Dynamics, Eclipse, Infinity, or Kicker.

Anyway, if you agree that selling those subs is the best plan (check ebay for similar auctions before posting yours)...then why don't we start from scratch and build you a system that you will enjoy.

1) How much do you want to spend total.
2) What do you want out of this system? Bass? Sound Quality? A little of both?

The amplifier is going to cost more than the sub(s) so you need to figure out a budget and pick the amplifer first. Then select the sub(s) that will match it. If you are looking for more SQ out of your system, I'd suggest picking up a 4-channel amp, a set of speakers, and a single subwoofer. That would be a nice budget system with better SQ and bass than stock.

 

[mobomelter]

1. haven't deiced on a full price.
2. i just want bass for now. i'll worry about the rest of the system later. i had just one 10 inch in my focus and it sounded nice. so i'd like to go the same route for the mazda for now.

 

[chuyler1]

Ok, well then, what's your budget for an amp and sub? I'd say you can get about $150 for the subs (a little more if they're in a box) on eBay based on the current auctions out there.

Here's my pick for you (assuming you don't want to spend a fortune):
Image Dynamics ID10v3d2 (wire voice coils for 4Ω load) $120
http://www.cardomain.com/item/IDSID10V3D2
MTX Audio Thunder 342 (closeout last year's model) $129
http://www.cardomain.com/item/MTX342

That will give you about 340w to a 250w subwoofer. If you want more power/bass later on, you can always use the amp to power a set of front speakers.

 

[mobomelter]

ok i'm new at this still so bear with me.
will this sub work with this amp ? according to cardomain i can wire that sub to run at 2 ohms impedance and the amp will produce 350w rms at 2ohms. i know the sub according to car domain is rated at 250w recommend rms power but i'm thinking the amp won't produce actually 350w rms. will that combo work without blowing up the sub?

EDIT : Wow i just posted this before i refreshed.

 

[mobomelter]

your combo is cheaper than mine and i trust it to work. now my question is how hard is it to bridge a 2-channel amp?

 

[BrianG]

The first thing to do is decide on the full price. Don't forget that power wire, fuse, RCA's, etc need to be included unless you already have them.

If you even think that you might decide to upgrade later, you might as well get a 4 channel. Sure, it will cost more now, but cheaper in the long run - and wiring is easier and cleaner. If you are absolutely sure you just want bass, you might as well get a class D amp since they are more efficient (more of the power you draw from the charging system will make it to your speakers and the amp will heat up less) than class AB designs.

Then you have to decide whether you'd rather have a hi-quality amp with solid power (MTX, Kicker, etc), or a cheaper one that outputs more "spec'd" power. You generally get what you pay for - those 1,000w amps might not be really 1000w (Audiobahn, Profile, etc are good examples). Plus, there is more to an amp than just power - like damping factor, frequency response, features (like subsonic filter, crossover, remote gain, etc). Most decent 10" subs handle between 200 and 400w. Get an amp that will match or slightly exceed the sub's power ratings. A good 400w amp will power most 12" nicely too.

You can use Ebay, but remember you aren't buying from a authorized dealer so there might be no warranty if something happens...

 

[chuyler1]

your combo is cheaper than mine and i trust it to work. now my question is how hard is it to bridge a 2-channel amp?

Voice Coils and Impedence
Please note that I suggested a different model of the same sub. The one you selected (DVC 4ohm) can be wired for 2ohms or 8ohms. The one I selected (DVC 2ohm) can be wired for 1ohm or 4ohms. The DVC 4ohm is good for using a monoblock amp while the DVC 2ohm works well with a 2-channel amp in bridged mode. Always try to get a sub that will run the amp at the lowest impedence it can handle. If you don't understand this, try reading through the following tutorials:
http://mobile.jlaudio.com/support_pages.php?page_id=145

Bridging Amps
Bridging an amp is a piece of cake. Take the negative speaker wire and connect it to the negative terminal of the left channel on the amp. Take the positive speaker wire and connect it to the positive terminal of the right channel on the amp. That's it! There will be instructions on how to do this in the user's manual of whatever amplifier you select.

Class D vs. Class AB
You won't notice a difference. They claim that class D designs consume less power by running more effeciently. I believe them, but I've never noticed a difference. But like I said in my post above, if you buy the MTX amp which is class AB, you can use it to power speakers later on. If you buy the Alpine amp which is a class D monoblock, it will always be limited to subwoofer duties.

Alpine vs. MTX
These two companies are pretty much equals in my book when it comes to amps and subwoofers. Alpine amps are a little better with regards to SQ but MTX amps put out more power at lower impedences. If I had to, I'd pick MTX for my subwoofer amp and alpine for my speaker amp. However, with brand names aside, the deal on the MTX is the best around...they are trying to unload the amps but you will still get the manufacturer's warranty. 380w for $129 can't be beat.

Wiring and other costs
Don't forget that you will need to purchase or build a box for the subwoofer. If you aren't handy with a tablesaw then I suggest purchasing a prefab MDF (medium density fiberboard, not regular fiberboard) from sounddomain when you purchase the subwoofer. You will also need a wiring kit which you can get cheap at www.knukonceptz.com. You can probably get by with connecting the speaker output leads from the factory head unit to either of these amps so you won't need RCA wires.

 

[mobomelter]

ok my plan is to get the mtx that was recommended by chuyler1 and the amp also recommend by chulyer1. i'm having best buy do the install since i am too lazy and hate doing amp installs. one last question. what gauge power wire would i need for that amp? and yes i have a box already. thanks sooo much for the help.

 

[chuyler1]

Please don't go to BestBuy. You will regret it. There must be a car audio specialty shop somewhere in your area. You've seen the people they hire...do you want them touching your car?

The Sub was Image Dynamics, the amp was MTX. An 8ga wiring kit will work fine.

 

[mobomelter]

their is a car audio place near by. problem is i don't trust them either. and if best buy charges 50 the car audio place charges 150. i'll check the car audio place out again since it was remodeled.

 

[hurleyblink]

their is a car audio place near by. problem is i don't trust them either. and if best buy charges 50 the car audio place charges 150. i'll check the car audio place out again since it was remodeled.

why would you pay to get your amp installed? it takes 30 min to an hour of your time thats well worth the $100 or $50 extra you pay to get someone else to install it, plus you will know where everything is, most places **** something up and wont tell you, byt the way those knukoncepts wires, i would recommend using them if you are planning on running a Line out converter (LOC), since the remote wire is in between the rca cables making it harder on you. Yeah that setup sounds like it would be good in your case, right now im waiting for my damn warranty to expire on my 03 ES, only 1200 more miles, then i get to throw my 2 kicker CVR 12's in the back,theyve been sitting in my room for a while only used them a week then i bought a new car. i need to find a different amp for them i had a audiobahn 8002t running them it did the job but it got really hot, had both subs running 2ohm on each channel.. thinking about a mtx 942.2.. hmm but i dunno if my alt will be able to put up with it anyone know? the stock alternators in the proteges are 80 amp right?

 

[chuyler1]

Installing aftermarket audio equipment does not void your warranty.

 

[goldwing2000]

Installing aftermarket audio equipment does not void your warranty.

Yes and no. If you screw up your electronics in the process of installation, you'll be SOL.

 

[chuyler1]

If you follow directions and install fuses in the correct places, there should be no reason why you would screw up any electronics in your car. If you are worried that you might do that...then you should just pay someone (preferably not BestBuy or Circuit City) to do it for you...warranty or not.

 

[goldwing2000]

Because of all the computerized circuits on the Mazda3, it's very easy to unintentionally screw something up, even if you know what you're doing.

I'm not saying that it's going to happen, just that it's a possibility to be watched for.

 

[mobomelter]

Because of all the computerized circuits on the Mazda3, it's very easy to unintentionally screw something up, even if you know what you're doing.

I'm not saying that it's going to happen, just that it's a possibility to be watched for.

thats why i'm letting a store do it. i tend to always mess something up.

 

[chuyler1]

All cars have computer circuits...but a battery is a battery, a head unit is a head unit, and a speaker is a speaker....and you can be sure the people working at BestBuy can't tell the difference between any of them.

Honestly, do you think they are an expert on your car and perform dozens of Mazda3 installs each week? The answer is NO. Are they going to take the time to find a grommet in the firewall to use? NO, they will prolly just drill a hole wherever they damn please. Will they remove your factory head without breaking any clips or scratching the face? NO, they will probably drop it on the floor.

These people get paid minimum wage and probably only stay with the job for 3-6 months tops. The highlight of their resume is probably that they can remove a head unit in under 30 seconds (hmm wonder how they learned that).

Meanwhile, the people installing equipment at a local specialty shop do it for a living. Sure it costs more, but that's because they don't cut corners and they take pride in their work. Search for BestBuy on this forum if you don't believe me. Most people that go their vow to never go back. My experience happened to be with Circuit City back in the day.