amp questions. [Archive]

BrianG

10-08-2005, 06:02 PM

Yeah, looks like you'll need to take them out of the box. They should have some sort of way to determine impedance, either by the model number, or labeled outright. If by some off chance they don't have any way to find out, just take a meter and measure the resistance across the coil. An 8 ohm sub will measure about 7 ohms on the meter (give or take). A 4 ohm sub will measure 3 ohms, give or take. The DC resistance is usually lower than the AC impedance.

The amp you choose will depend on the coils of the subs. Sub coils can be single coil 8 ohm, single coil 4 ohm, DVC (dual voice coil) at 2 ohms each, DVC at 4 ohms each, etc. Once you find out if each sub is a single coil or DVC, and what the impedance of each coil is, let us know and we can suggest an amp.

No matter what amp you get, you really need to get a box that is designed for those subs. A properly tuned box can make a huge difference in how those subs sound. However, don't expect huge low-end out of 8" subs - they will tend to be "punchy". If you like a lot of loud, deep bass, get a bigger sub (12"). Otherwise, those 8's should do nicely.

Once you get the sub specs, you can use a box design program like WinISD to figure out the optimum box for those speakers, the sound you want, and the space you have. Or, post the TS parameters and I (or someone else) can calculate the box size values.

mobomelter

10-09-2005, 05:33 PM

i found out they are the alum10n from audiobahn. stats are as followed from the audiobahn website.

Size: 10"
Magnet Weight: 120oz
Power Handling: 800 rms
Frequency Response: 20hz - 500hz
Effciency: 95.6db
Voice Coil: 3" Dual 6 Ohm
Operation: 3 or 12 ohm
Mounting Depth: 5"
Hole Cutout: 9 3/4"
Outer Diameter: 10 7/8"

I'm trying to find an amp that isn't too expensive so ebay is probably the ticket. thanks for your help!

chuyler1

10-09-2005, 09:10 PM

1600w RMS for a pair of 8" subwoofers? umm, ok. Good luck finding a budget amp for those.

1sty

10-09-2005, 09:11 PM

1600w RMS for a pair of 8" subwoofers? umm, ok. Good luck finding a budget amp for those.
Thats audiobahn RMS.

If I hooked one of those up to a real 1600 watt rms amp, the cone would hit you in the head on its way to mach 4.

Mobo, becuase of there incredibly BS rating schemes at audiobahn, you are best off looking for a 1600 watt rms audio bahn amp that is mono amp and is 1 ohm stable. Since audiobahn is also the worst whore on the planet, you can buy them for dirt cheap all over the net.

I assume this is what you have?
http://www.caraudiodeals.com/product_info.php?products_id=177

Heres an option for an amp:
http://www.thezeb.com/p-Audiobahn-Class-D-A12001DT-100069.htm

chuyler1

10-09-2005, 09:14 PM

Yeah, i figured as much...although i'm sure they would work great with a 1600w audiobahn amp. 95.6db efficiency? yeah right.

1sty

10-09-2005, 09:24 PM

We both know that sub could handle a real 800 watts rms but it likely needs that much to hit X-Max do to itsincredibly shitty motor structure design.

Being an $90 sub, it would be better used with about 200 watts rms.

chuyler1

10-09-2005, 09:29 PM

I'd say sell the damn things on eBay and buy a real subwoofer and amp.

BrianG

10-09-2005, 09:35 PM

And, being DVC 6 ohms, the choices of amps is a little more confusing. For typical setups, you'd wire both subs with either all coils in parallel for a 1.5ohm total load, or the coils on each sub wired in series (12ohms) and that in parallel with the other sub wired the same way for a total of 6 ohms. So, you have to find an amp that will put out the power you want at 1.5ohms or 6ohms. The Audiobahn A12001DT or A18001DT would probably be a good match since the wattage claims on both the subs and amp are inflated. Personally, I'd stick with about 800w total of real honest rms power.

chuyler1

10-09-2005, 10:11 PM

Or a JL Audio amp that puts out the same power at any impedence.

1sty

10-09-2005, 10:40 PM

They goes the keeping it cheap thing. Although the Jl 250/1 is all those subs realisticly need. Perhaps a 500/1 would be fun to watch.

chuyler1

10-09-2005, 10:43 PM

...and smell

mobomelter

10-09-2005, 11:44 PM

1sty

10-10-2005, 12:11 AM

Whats your amp budget?

mobomelter

10-10-2005, 12:27 AM

thats the thing i'm trying to stay cheap. i'd like to spend at the most 200. thats why i'm only going to hook up 1 sub for now.

BrianG

10-10-2005, 12:38 AM

ok after reading all your posts i'm still a tad bit confused (i also haven't slept in awhile so that could be part of it.) do i really need to run full power through the subs? or would i be ok running a little less than full power? remember i'm trying to keep it cheap so ANY brand amp will be ok.

No, you don't need to run full power, but running too low power could damage the subs just as easily as running too much power. It is easier just to get an amp that has the output you need at the impedance you need.

EDIT: Ok i've decided that dealing with 2 subs is too much of a pain in my ass. Besides i rather like trunk space. What kind of power would you suggest running through just 1 of those subs?

EDIT 2: Well from what i can tell you guys think i should get an audiobahn amp rated at 800watts rms. since i only want to power one sub will this (http://cgi.ebay.com/Audiobahn-A8000T-Intake-Mono-800W-Amp-NEW_W0QQitemZ5816650767QQcategoryZ64571QQrdZ1QQcmd ZViewItem) fit the ticket?

The amp in your link is rated 400w at 4Ω mono and 800w at 2Ω mono. Since your sub is 3Ω (both coils wired in parallel), the output will be about 600w. This should still be a decent match.

BTW: That amp uses two 30A fuses, which according to my calculations outputs only about 560wrms max in an ideal world. So, the real output at 3Ω will be more like 400-450wrms. This is still OK since the sub is probably overrated as well.

hurleyblink

10-10-2005, 01:25 AM

Just a suggestion id look into hifonics amps if i were you, usually they overrate their power but it is not in a way like audiobahn does, if you go hifonics though, get the brutus amp to pus them, their zeus series isnt all that great, but i mean that will work too if it is in the buidget you are looking for look on ebay for these amps as well, you can get a new one for around 200 maybe a little less, and what kind of speakers are u using, im assuming the audiobahn alums, lol i seen something about wiring them down to 3 ohms, and i know those dual 6ohm coils, the hifonics amps i think some are .5 ohm stable, and some are 2 ohm stable, make sure you look at that too

chuyler1

10-10-2005, 09:50 AM

The amp in your link is rated 400w at 4Ω mono and 800w at 2Ω mono. Since your sub is 3Ω (both coils wired in parallel), the output will be about 600w. This should still be a decent match.
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.

BrianG

10-10-2005, 10:04 AM

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

10-10-2005, 12:08 PM

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 shitty 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

10-10-2005, 06:48 PM

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

10-10-2005, 07:18 PM

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

10-10-2005, 07:22 PM

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

10-10-2005, 07:43 PM

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

10-10-2005, 07:46 PM

ok i'm new at this still so bear with me.
will this sub (http://www.cardomain.com/item/IDSID10V3D4) work with this amp (http://www.crutchfield.com/S-20yKjFxMn6G/cgi-bin/ProdView.asp?g=120&I=500MRPM350) ? 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

10-10-2005, 07:50 PM

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

10-10-2005, 08:10 PM

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

10-10-2005, 08:25 PM

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 (http://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

10-10-2005, 08:55 PM

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

10-10-2005, 10:55 PM

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

10-11-2005, 01:11 AM

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

10-11-2005, 01:55 AM

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 fuck 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

10-11-2005, 09:56 AM

Installing aftermarket audio equipment does not void your warranty.

goldwing2000

10-11-2005, 10:40 AM

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

10-11-2005, 11:24 AM

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

10-11-2005, 12:18 PM

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

10-11-2005, 12:26 PM

chuyler1

10-11-2005, 02:54 PM

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.

goldwing2000

10-11-2005, 02:57 PM

All cars have computer circuits...

True enough, but we seem to be blessed with an inordinately large number of them, controlling things that you would never think needed a computer to control them.

I'm with you on the rest of the rant.

BrianG

10-11-2005, 03:29 PM

I agree with the goldwing2000's sentiment about there being cpu circuits controlling who knows what. Kinda reminds me of the older civic (late ninety's) where you had to keep the stock head unit in the dash to retain door locks or domelamp or something. You had to intall a Y adapter for some of the wires to route power to the stock and aftermarket HU and then stuff the stock HU behind the heater control area to make room for the new HU.

However, in the 3, there is nothing about the factory deck that controls anything else other than audio. As long as you're careful about where you drill holes and run wires (and don't yank/stretch/stress other wires when you run the new wiring), you'll be fine. Stick to the "accepted" methods of stereo installs and there will be no problems. Once you start adding things like remote starters/alarms/window roll modules/etc do things get more involved because you start tapping into things CPU controlled.

BTW: Speaking from experience, basic alarms with door locks, door/trunk triggers, and flashing parking lights are easily installed in the 3.

mobomelter

10-11-2005, 08:31 PM

my only concerns are the line out converter and drilling a hole in my firewall. if anyone could point me to a place or if someone could show me where they drilled their hole i'd do the install myself. the line out i'm pretty sure wouldn't be too hard but the part about drilling a hole in my firewall sucks. also if anyone could point me to what line out convertor and amp kit i should pick up that would help out alot too. sorry to keep bothering you guys but i want to do it right this time around. thanks again for the help.

mobomelter

10-11-2005, 08:46 PM

Scosche SLC4 Four-channel line output converter
http://www.crutchfield.com/S-oulsvBuNljG/cgi-bin/ProdView.asp?g=721&I=142SLC4
i basically just take that and hook it up to the speaker wires from my head unit that go to my rear speakers correct?

chuyler1

10-11-2005, 09:26 PM

Yup, that's it. Search the forum for pictures of where people have gone through the firewall. There are rubber grommets that you can drill an extra hole into. I don't have a Mazda3, otherwise I'd take a picture and show you.

mobomelter

10-11-2005, 09:50 PM

ok seems that i can run an 8-gauge power wire through the hole where my hood latch goes. so no drilling needed. another question. does it matter if i hook up the loc to the rear left or rear right? also will any standard 8 gauge amp kit work?

chuyler1

10-11-2005, 11:06 PM

The LOC should have two channels (4 wires). Hook it up to both rear channels. On the 5-door, its easiest to pull out the head unit and tap into the wires behind it.

mobomelter

10-11-2005, 11:12 PM

ok. also i just scored the amp you suggested for 50 bucks on ebay and it works. :)

goldwing2000

10-12-2005, 10:18 AM

Another place you can run a wire through is the soft foam seal by the A/C evaporator. No drilling required, just push it around the side of the seal! The foam is soft enough to completely seal around it.

mobomelter

10-12-2005, 01:43 PM

yeah i went to my local car specialty shop and they want $175 for the install i was like wtf?

ZoomVT

10-12-2005, 02:11 PM

they want to charge me 250 but it includes a custom box.

BrianG

10-12-2005, 03:49 PM

Another place to run wire, although it requires drilling, is behind the glove box. Once the glovebox is out (pretty easy to do) there is a pretty big open space to drill. Just make sure you know where you are drilling and use a grommett.

mobomelter

10-12-2005, 06:05 PM

thats a crazy price. considering all they are doing is running the wires and the loc. it shouldn't cost 175.

mobomelter

10-12-2005, 08:21 PM

amp kit (http://www.cardomain.com/item/LITPK8IC) is this what i need?

chuyler1

10-12-2005, 10:18 PM

Or this one for $13.99...
http://www.knukonceptz.com/productDetail.cfm?prodID=eKo-K8

tsunami

10-12-2005, 11:06 PM

wonder what they mean by "built in tunr on lead" with thier rcas? also i have heard from others on this board that the knuconceptz rca's suck but their power wire is good stuff....

hurleyblink

10-12-2005, 11:14 PM

wonder what they mean by "built in tunr on lead" with thier rcas? also i have heard from others on this board that the knuconceptz rca's suck but their power wire is good stuff....
well the rca's are normally stuck together (the two wires) the knuckoconceptz ones are stuck together the same but the remote wire is inbetween them.. yeah that gives you noise.. power running through the middle of rca's aint good. i had these wires the power wire is absolutly great, looks good too, but the rca's suck.. your better off with the ones they sell at walmart..
(rca)(remote)(rca) ||| thats how it is..

mobomelter

10-12-2005, 11:47 PM

yeah and with shipping the walmart ones would be the same price.

chuyler1

10-12-2005, 11:49 PM

It sends such low current that it shouldn't be a problem. You can always run a separate wire if it is. In many cases, amps have auto-sensing turn on so the remote wire isn't even necessary.

BrianG

10-13-2005, 08:36 AM

It sends such low current that it shouldn't be a problem. You can always run a separate wire if it is. In many cases, amps have auto-sensing turn on so the remote wire isn't even necessary.

I agree with chuyler1, the majority of the noise from the power line comes from the high current draw of the battery wire. Any decent after market deck will have internal power filters so the remote output is cleaner than regular battery connections. Just keep your RCA's at least 6" away from any power cable, and if they do get close, make sure they intersect at a 90degree angle rather than running parallel to each other. If you still get noise on the remote, a small 10uF capacitor (about $1 from radio Shack) will help reduce the noise.

mobomelter

10-13-2005, 08:46 PM

tsunami

10-13-2005, 08:58 PM

how does a capacitor reduce noice??? 10 micro farads is some small stuff but where would you put that with rca to reduce noise...??

BrianG

10-13-2005, 10:21 PM

how does a capacitor reduce noice??? 10 micro farads is some small stuff but where would you put that with rca to reduce noise...??

A capacitor by nature passes AC and blocks DC. It also stores a charge - which is the feature we take advantage of when using a large one on an amps' power wire.

If you attach the + of the cap to the remote wire and the - of the cap to ground, it will shunt the very small induced AC (noise) to ground. The uF value of the cap to use depends on the load and the frequency. Since the induced noise has very little sourcing current and the frequency is fairly high, a small cap is all that is needed. This cap is a decent example: http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=272-1013 An even smaller cap may be necessary (1uF or even lower). Again it depends on the amount of sourcing current of the noise and the "load".

You wouldn't want to do this on an RCA signal wire since you'd end up blocking or shunting (depending on the configuration of the cap) the signal! If you have noise on the RCA itself, they must be running alongside a fairly heavy current wire somewhere. You can either move the wire or shield it at the problem area.

Another way to supress noise is to use an inductor (choke) in series with the power. An inductor is basically just a coil of wire wrapped around a core (usually air or ferrite). An inducator passes DC, but blocks AC by using back EMF. The mH value to use depends on the load and the frequency. SInce the load is in series with the inductor, the size of the wire in an inductor depends on the current the load needs. Sometimes simply getting a ferrite choke core (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=273-105) and wrapping the remote wire through it a few times is enough to eliminate the noise.

Those noise supressors on the market are basically just a capacitor and inductor network wrapped in a small box. Actually, this is basically a low pass crossover meant to pass very low AC (to the point of being DC).

Speaking of crossovers, the principles explained above is what makes them work. A high-pass xover uses an inductor in series and then a cap in parallel to the load. The inductor blocks some AC and the cap shunts the rest. Since the frequency determines the impedance of the xover network, the output is a slope - 6db for a single component (inductor or cap), 12 db when using both of them, and so on. Reverse the order of components for a low pass xover.

Sorry about the long explanation and the slight deviation from the topic on hand... I do tend to get carried away.

tsunami

10-13-2005, 11:03 PM

BrianG

10-14-2005, 10:56 AM

ah so it takes the ac to ground and b/c its such a small cap doesn't interfer with the dc... did i read that right??? no worries bout the explanation on my end, i always try to learn bout stuff i don't understand... thats why i ask a lot of questions... i just can't help it!!!

Sort of. Think of a cap as a variable resistor whose resistance is dependant on frequency. The higher the frequency, the lower the resistance. Formula:

Xc = 1 / ( 2*Pi*F*C)

Xc=impedance
Pi=3.1415926538...
F=Frequency
C=Capacitance.

So, if the noise is 1kHz and the capacitor is a 10uF, the impedance is 15.9ohms. So, to the noise (at 1kHz), it looks like there is a 15.9 ohm resistor going to ground - but to DC, there is nothing there (infinite resistance). This is because we can consider DC to be 0Hz and I said that the impedance will go up as frequency goes down. Plugging in 0 to the equation as frequency will result in an error because most calculators can't handle a division by 0 - but actually the answer is infinity. While the cap effectively blocks the DC, it will also store a DC charge, so the remote wire will remain on a little bit longer than normal when the radio is shut off (maybe 1/2 second - not much).

I can see we are getting really far off track here: from what amp to buy, to AC component theory. For the sake of the thread, PM me if you have any more questions. :)

tsunami

10-14-2005, 09:36 PM

I can see we are getting really far off track here: from what amp to buy, to AC component theory. For the sake of the thread, PM me if you have any more questions. :)

haha....will do... though thanks for explianing that, really started to make some sense there (kinda scary)

mobomelter

10-20-2005, 12:24 AM

haha....will do... though thanks for explianing that, really started to make some sense there (kinda scary)
i just installed the amp tonight and it works great. i got the amp for 50 bucks on ebay and the sub for 120 from cardomain. i finally got around to testing my audiobahns and it turns out they are actually alum10q's which have dual 2 ohm voice coils. i'm running a single audiobahn set up for a 4 ohm load until my image dynamic shows up in the mail.

tsunami

10-20-2005, 07:24 PM

congrats man... i assume the install went smooth enough and you didn't have any magor snags?

mobomelter

10-20-2005, 08:07 PM

nope none at all. the sub is a tad bit loud though.

tsunami

10-20-2005, 08:14 PM

yeah you are seriously overpowering your stock speakers with the sub... my problem is my sub isn't loud enough....yet...

mobomelter

10-21-2005, 03:11 PM

whats going to make me angry is if my image dynamic isn't as loud or nice as the audiobahn. oh and having hatchbacks is great the whole trunk area acts like a box so it sounds so sweet inside the car.

chuyler1

10-21-2005, 11:39 PM

The two subs are close in price range but I'm pretty sure the ID10v3 is going to sound much better. It should have a smoother frequency response and will probably play a little deeper with the same amplifier power.

Please give us an honest review when you do the swap. Listen to a few songs just before you pull out the audiobahn, then listen to them again with the ID. Pay carefull attention to dynamics, tone, frequency response, and accuracy.

mobomelter

10-22-2005, 04:40 AM

its scheduled to be here wednesday so i'll try and get it in the car when it gets here.

mobomelter

10-24-2005, 07:13 PM

i've actually decided i'm going to be selling my new sub because i can't find anyone that wants to buy my audiobahns. so i have no reason to replace the one i am using. if anyone wants the image dynamic sub let me know asap because i'm going to be returning it if not.

chuyler1

10-25-2005, 10:12 AM

You're not even going to listen to it? Sell the Audiobahns on ebay. Someone will bite.

mobomelter

10-25-2005, 12:29 PM

thats true. now what do you think would be a good price for those audiobahns 160 shipped?

chuyler1

10-25-2005, 01:45 PM

Just do a search on ebay for the model number and add watches to the auctions. When they finish, base your starting price around the starting and ending prices of the other auctions.

mobomelter

10-26-2005, 10:57 PM

i installed the image dynamic sub today and its just not as loud as the audiobahn. right now i'm going to chalk it up to it being brand new and the audiobahn being way past worn in.

tsunami

10-26-2005, 11:25 PM

deffinatly could be true... as i have read a sub does need a "slight" wear in period for full throw??? but then again, i read it on the internet so....???

mobomelter

10-27-2005, 12:52 AM

i hope thats the case.

BrianG

10-27-2005, 07:55 AM

Yeah, most subs will loosen a bit after a few hours of playing time. The surround and spider are a bit stiff when new. You can either play music for a few hours or play a 45-60Hz test tone through it for a little while. It also depends on the suspension material and temperature. Rubber surrounds in cold will obviously be stiffer than when it is warm.

The box size plays a big part as well. Manufacturers usually recommend a range of box sizes, but I find most recommendations to be a bit on the small side. Smaller boxes will play tighter and fit more easily, but you may want a larger box for more output. Plus, each sub's specs can help determine whether it is more suited for a ported or sealed box. A good program for box building is WinISD. Once you enter the driver's T/S parameters, it will recommend a box type and size. You can tweak it for the sound you want from there. The basic program is free: http://www.linearteam.dk/default.aspx?pageid=winisd