Amp + DVC sub question!

[mbowen89]

So I recently bought a used amp, a Pioneer GM-X862.

I also just bought a new 12" DVC sub, the Infinity Reference 1252w (http://www.crutchfield.com/p_1081252W/Infinity-Reference-1252w.html)

Now, since this is a dual voice coil sub, I can either get a 2ohm or 8ohm impedance.

Here are two examples of what I could do:

http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/1DVC_4-ohm_mono.jpg

OR

http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/1DVC_4-ohm_2ch.jpg

Here are my amp specs:

Maximum power output --- 250 W × 2 / 760 W × 1
Continuous power output ---
125 W × 2 (at 14.4 V, 4 Ω, 20 — 20,000 Hz, 0.08% THD)
380 W × 1 (at 14.4 V, 4 Ω, 20 — 20,000 Hz, 0.8% THD)
190 W × 2 (at 14.4 V, 2 Ω, 20 — 20,000 Hz, 0.8% THD)
Load impedance ---
4 Ω (2 — 8 Ω allowable)
(Bridge connection: 4 — 8 Ω allowable)


What would be the best way to wire my DVC sub up to this amp to get the most power out of it? Would putting the DVC in parallel (2ohm imped.) and putting it on channel one be the best? Am I able to do that, only bridge it (or can I not bridge a 2 ohm imped?)?

Thanks for any help!

[Randyman...]

Either way should work. I'd try it as 2 Ohm on one channel (DON'T Bridge it wired as 2ohm), and also try 8 Ohm Bridged - pick the one you like better. You should get more power @ 8Ohms Bridged accoring to the specs. Specs are a great place to start, but trust your ears - they are all that matters in the end...

:cool:

[mbowen89]

What did you see that told you 8 ohms bridged is better than 2 ohm on channel 1?

I completely agree that it's what the ears hear that matter, but it also matters if my amp starts smoking! :D

So, 2 ohms bridge is BIG NO?


------

Also, what if I hook up one coil to channel one, and the second coil to channel two? Is that a big NO-NO? The gain would match, and I could have both channels be from same input...

[ratbuddy]

So, 2 ohms bridge is BIG NO?

Yeah. The amp would die a painful death. Run it in series, 8 ohms bridged.

[Randyman...]

You can take the 4 Ohm x2 rating and it is identical to running @ 8 Ohm Bridged (when you bridge an amp, each channel sees 1/2 the total load impedance - it is like a person opening a door while another person closes the same door - the load is equally split between the 2). 125 x2 @ 4 Ohms = 250Watts @ 8 Ohms Bridged versus a single chanel @ 2 Ohms which is 190Watts...

2 Ohms Bridged is not recommended in the specs (equivalent to 1 Ohm per channel) - so you will run into current limiting and likely overheat...

:cool:

[mbowen89]

So, by doing the 8ohm bridge, I am getting a total of 250W, compared to the single channel at 2 ohm which would give me a total of 190W.

250 is BIGGER!

Here's the question though... since this is a DVC sub, each coil will get 125W, correct?

This is the spec of my sub: power range: 60-300 watts RMS (150 watts per voice coil)

That means, I would basically be giving each coil the nominal RMS of 125W... all this is correct, right? :)

--------

About wiring now...

If I run two wires together as so for power and ground:
http://i36.tinypic.com/2wdt4k8.png

Would 12AWG be sufficient? 12AWG handles 9.3A, so if I did it like the picture and ran two together, it could handle 18A. That is surely enough for this system wouldn't you say? Also, I see that sometimes there is a fuse on the power wire... but there are fuses on the amp as well. What if I don't have a fuse on this power wire... will I be ok?

[deadlysyn]

You would be ok without a fuse on the power line, but I wouldn't take the chance. As an MECP certified installer, I would put it about 12" or less from the positive terminal of the battery. The reason for this, is if a short appears in the line after the fuse, the fuse will blow instead of causing a possible fire. Also, I would wire the sub to 8 ohms, by connecting the positive terminal of one voice coil to the negative terminal of the other voice coil, and then bridge the amp. You will get equal power to each voice coil, which is the absolute best way to do it. One guy I used to work with would swear that you can hook up each channel on a dual channel amp to each voice coil on the sub. The problem is sometimes the output from each channel on an amp can vary a little bit, which will cause one voice coil to work against the other. Also, since you are powering a subwoofer, you will really only want one channel anyway. There is a reason Class D subwoofer amps are single channel, although I have seen some that were 2 amps in one.

[Randyman...]

#1 = Yup.

#2 - I'd go for a single 8-Gague run versus 2x 12Ga runs. You will ABSOLUTELY POSITIVELY want to install a fuse as close to the battery as possible. If that wire shorts out anywhere along the way, the fuse will pop. If the wire shorted out w/o a fuse, the wire would literally get hot enough to burn through the insulation and start a fire (seriously). A wire can get squeezed enough to eventually rub through the insulation, you could get into an accident where the wire is smashed into a dead short, etc. A fuse at the battery IS A MUST...

I once neglected to securely mount 2x "8D" Diesel type batteries in my Snug-Top. The battery slid around and the + terminal made contact with the side of the bed (the tie-down thingy that protrudes off the bed). Luckily, I had a thinner ground wire than I should have been using (a 4Ga Ground IIRC), and I literally MELTED the 4Ga Ground Wire in pieces and filled my Snug Top up with smoke. I was very lucky my truck didn't catch on fire (no carpet in the Bed at that time). If I would have been using 1/0 ground wire like I usually do and had the back finished in carpet, I am confident my truck would have burned to the ground :eek: . While not exactly a "Use a Fuse" rant, it demonstrates the danger of high-current wires that aren't adequately protected against shorts...

:cool:

[deadlysyn]

#1 = Yup.

#2 - I'd go for a single 8-Gague run versus 2x 12Ga runs. You will ABSOLUTELY POSITIVELY want to install a fuse as close to the battery as possible. If that wire shorts out anywhere along the way, the fuse will pop. If the wire shorted out w/o a fuse, the wire would literally get hot enough to burn through the insulation and start a fire (seriously). A wire can get squeezed enough to eventually rub through the insulation, you could get into an accident where the wire is smashed into a dead short, etc. A fuse at the battery IS A MUST...

I once neglected to securely mount 2x "8D" Diesel type batteries in my Snug-Top. The battery slid around and the + terminal made contact with the side of the bed (the tie-down thingy that protrudes off the bed). Luckily, I had a thinner ground wire than I should have been using (a 4Ga Ground IIRC), and I literally MELTED the 4Ga Ground Wire in pieces and filled my Snug Top up with smoke. I was very lucky my truck didn't catch on fire (no carpet in the Bed at that time). If I would have been using 1/0 ground wire like I usually do and had the back finished in carpet, I am confident my truck would have burned to the ground :eek: . While not exactly a "Use a Fuse" rant, it demonstrates the danger of high-current wires that aren't adequately protected against shorts...

:cool:

I couldn't tell you how many times I have had to fix installs because someones neighbor "knew how to do it". I remember one very vividly. No fuse on the power wire, no grommet in the firewall, and the power wire was several pieces of 4, 8, 10, and 12 guage wires twisted together and black taped. There were several splices in the RCA patch cable going from the head unit to the amp. And the ground cable from the amp was just twisted around a screw through the trunk floor of the car. The wires going from the amp to the subs were about as small as the wires in a SATA cable. On top of that, there was a 60 amp fuse, and the amp only required a 30. Luckily the owner of the car caught the bad install in time and brought it to a professional shop, before something serious happened.

[Randyman...]

Scary indeed :eek: . I also have another rather embarrassing story from my past (early 90's). I installed 2x Punch 18" subs and an Autotek 7600 and a slew of Sony Components in my friend's 1987 Mustang GT. I spent all day making the box and running wires, etc. So, it is late and I go to mount the amp, and w/o thinking I mount it to the trunk floor where the spare tire used to go. Well, what is below the trunk floor? THE GAS TANK! Neither of us realized my massive mistake until his car would randomly die. I guess moisture was entering the gas tank causing the car to stall like crazy. I felt SOOOOOOOOOOOOO stupid, and now I ALWAYS triple check under the car before drilling anything. He got his car fixed, sold it, and bought an Isuzu Rodeo - the 18's sounded much better in the Rodeo for sure (6.5Cubes ported @ 32Hz IIRC) :p

Yet another time, I drilled a screw right through my brake light wire (the + is always hot, the - passes through the switch at the pedal). The wire burned up from the X-Tra cab all the way under the dash. I had to pull out ALL of my carpet (including seats) and even had to remove the DASHBOARD to fix (re-run and re-splice) the wire. I also sawed through some wires in my 1987 4-Runner when mounting some rear seat speakers. Sheesh! I've made plenty of mistakes in my day - it is how we learn :p Now, I take my time - as much time as it takes. Triple check EVERYTHING. I've been fairly "Error Free" over the past few decades, but my late teens were adventurous to say the least :)

:cool:

[deadlysyn]

Scary indeed :eek: . I also have another rather embarrassing story from my past (early 90's). I installed 2x Punch 18" subs and an Autotek 7600 and a slew of Sony Components in my friend's 1987 Mustang GT. I spent all day making the box and running wires, etc. So, it is late and I go to mount the amp, and w/o thinking I mount it to the trunk floor where the spare tire used to go. Well, what is below the trunk floor? THE GAS TANK! Neither of us realized my massive mistake until his car would randomly die. I guess moisture was entering the gas tank causing the car to stall like crazy. I felt SOOOOOOOOOOOOO stupid, and now I ALWAYS triple check under the car before drilling anything. He got his car fixed, sold it, and bought an Isuzu Rodeo - the 18's sounded much better in the Rodeo for sure (6.5Cubes ported @ 32Hz IIRC) :p

Yet another time, I drilled a screw right through my brake light wire (the + is always hot, the - passes through the switch at the pedal). The wire burned up from the X-Tra cab all the way under the dash. I had to pull out ALL of my carpet (including seats) and even had to remove the DASHBOARD to fix (re-run and re-splice) the wire. I also sawed through some wires in my 1987 4-Runner when mounting some rear seat speakers. Sheesh! I've made plenty of mistakes in my day - it is how we learn :p Now, I take my time - as much time as it takes. Triple check EVERYTHING. I've been fairly "Error Free" over the past few decades, but my late teens were adventurous to say the least :)

:cool:

Scary things like that have happened to all of us. On one of my first solo installs, my old boss told me to put the amp on the back of the back seat of an older Mercedes (it was new at the time). As I proceeded to put the first screw in, I noticed the smell of gasoline. It turned out, that the fuel tank was in the trunk, right behind the seat on that particular model.

another one was on an old car I drove for a while. It was my 2000 Honda Prelude. I didn't stop to think about the fact that the factory stereo system was amplified, and an easy way to feed the signal from your amp (was a JL Audio quad channel, don't remember the exact model)is to run the speaker outputs to the wiring harness in the dash. This was a competition level system (I used to do IASCA db Drag Racing), so I had 4 15" W6 subs, running off 4 1000/1 amps in a custom fiberglass enclosure that took up the back seat and trunk. When I first turned on the system, all I heard was bass, and smelled the lovely smell of burnt electronics. After about half an hour, a buddy that I worked with asked "you did bypass the factory amp, right?" I felt like a moron at the time, but ran wires directly to the factory speaker locations, and it sounded decent. I proceeded to make all the adjustments to make it sound good. Then set up the db meter from the shop in the car, and cranked it up. I couldn't get an accurate reading, because the back window blew out of the car and ended up being a big mess that I had to clean up. The moral of this story is, if your stock stereo is amplified, make sure you bypass the factory amp, and if you have that much power in a small Honda, make sure you have Lexan windows before you compete. :p

[tweakboy]

Nice randyman you rock.

Ya the last thing you want is to blow your amp or blow your woofer... gl

[ratbuddy]

So, by doing the 8ohm bridge, I am getting a total of 250W, compared to the single channel at 2 ohm which would give me a total of 190W.

250 is BIGGER!

Here's the question though... since this is a DVC sub, each coil will get 125W, correct?

This is the spec of my sub: power range: 60-300 watts RMS (150 watts per voice coil)

That means, I would basically be giving each coil the nominal RMS of 125W... all this is correct, right? :)

--------

About wiring now...

If I run two wires together as so for power and ground:
http://i36.tinypic.com/2wdt4k8.png

Would 12AWG be sufficient? 12AWG handles 9.3A, so if I did it like the picture and ran two together, it could handle 18A. That is surely enough for this system wouldn't you say? Also, I see that sometimes there is a fuse on the power wire... but there are fuses on the amp as well. What if I don't have a fuse on this power wire... will I be ok?

You wanna wire it the way shown in the second picture, series. Yeah, each coil should 'get' 125w. You want to be careful when using an amp that doesn't put out as much power as the sub is rated for. People tend to turn the gain on the amp way up and end up driving them to the point of clipping. That's what kills way more subwoofers than 'blowing' them due to too big an amp.

For the wire, 8 gauge would work but why not run 4 gauge just for futureproofing? You're already gonna be making the effort to run it, and the thicker wire doesn't cost all that much more. That way when you step up to something bigger or add a second amp for the other speakers, you won't have to repeat the process :beer:

The fuse on the amp protects.. The amp. Definitely don't go naked on the power wire. Like the others have said, it's a good way to burn down your car.

[Randyman...]

This was a competition level system (I used to do IASCA db Drag Racing), so I had 4 15" W6 subs, running off 4 1000/1 amps in a custom fiberglass enclosure that took up the back seat and trunk.

Nice! I remember attending my first Rockford Fosgate "Thunder on Wheels" competition as a spectator when I was like 13 or 14. I was instantly hooked, but never really competed all that much. I do it for the love of music :) None of my installs have been terribly flashy (my glassing skills leave much to be desired and I HATE sanding :( ), but they are always solid for the most part. My silliest install was 8x 18" Punch Pro SPP-188 on 2x Power 650's, and then on a Power1000. Those amps were way too expensive for me to afford the quantity I would have liked (the Power1000 sold for around $2K back in the later 80's/early 90's), but damn that thing hit 15-30Hz like you would not believe! I know your 4x 15" W6 probably destroyed that setup in SPL, but the subsonics in that system were gut-wrenching... I still have the Power1000 in my closet. Today, I've streamlined and I run a T20001BD on a air of JBL 12" W12GTi's (the ones that compare to W7's)...

Nice randyman you rock.

Ya the last thing you want is to blow your amp or blow your woofer... gl

LOL - I certainly do try to "rock" to the best of my abilities :p

:cool:

[mbowen89]

Hey guys, my sub is rocken! Thanks for the help.

I do have some questions though.

Right now my DVC sub is wired up in series (8ohm) and bridged across the 2 channels.

Here is my question: how should I set up the RCA inputs? Do I need both RCA inputs?

Here is from the manual:

http://i34.tinypic.com/nmxmxx.jpg

This looks like I have it on one-channel mode - mono. But what do I do for the RCA inputs.

This may sound like a dumb question I am asking.. but it is odd because if I have both RCA in, and both lines turned up on my line converter, I don't get any bass. As soon as I unplug one channel I get bass. I just want to make sure I have my line converter hooked up correctly and that I have the amp inputs right.

Thanks!

[deadlysyn]

In some cases, you would only use the left input for a bridged amp. I have always found that the output of the amp is better if you use both of them anyway. Even my Kenwood KAC 8152D only really needs the left RCA hooked up, but I get twice the output using both of them. Also, if your head unit has a dedicated subwoofer output, use that, since most decks with a sub out will have level control. This will allow you to turn up the sub for some kinds of music, and down for others. They may also have some cross over settings (aka low pass filter), but I always set them at the deck to thru or off. Use the amplifier for your crossover settings, since they work much better, and will sound much better.

[mbowen89]

My stock HU doesn't have anything like that.

The line converter is just spliced into both of my rear speakers.

I do only have one hooked up to it now, but as I said, I had to UNPLUG one of them just to get it to work at all. What does that tell you?

[Randyman...]

It tells me that your +/- polarity is reversed on one of the connections into the Line Converter ;) Either find the correct wiring diagram for your car, or simply swap the + and - on one of the Line Converter's channels (don't flip both channels or you will be in the same boat you are in now)...

Ideally, you'd want the sub to be of the same polarity as the factory speakers (+ voltage results in a compression wave from both sets of speakers), but the sub is likely dwarfing any bass output from the factory speakers, so any constructive/destructive interference from Sub > Factory speakers will be minimal at best.

:cool:

[mbowen89]

I did reverse the wires on one of the line converter connections. Now, I get the biggest bass when it is centered, and it doesn't go down much if I pan left or right.

The thing is, I have to still turn down one of the adjustments on the line converter, basically only turning on one line. So, it's like I can only have one input into the amp...

[deadlysyn]

I did reverse the wires on one of the line converter connections. Now, I get the biggest bass when it is centered, and it doesn't go down much if I pan left or right.

The thing is, I have to still turn down one of the adjustments on the line converter, basically only turning on one line. So, it's like I can only have one input into the amp...

It sounds like you have the gain (sometimes called input level or sensitivity) on the amplifier too high. The way I tend to adjust it, is to turn it all the way down, turn your volume up about 3/4 on the volume scale, and adjust the gain up until you have a good balance between bass and music. Another way, recommended by JL Audio is with a DMM set to DC voltage at the speaker terminals of the amp, but their chart only seems accurate with their amps.

[Randyman...]

I'd agree. The issue comes with the line adaptor and how to calibrate it to spit out standard line level when the radio is at maximum clean volume.

I'd probably try setting the Amp's gain around 25% (1/4) or less for now. Then crank the line adaptor's gains all the way down. Crank up the radio until you get it nice and loud while remaining 100% clean (no distortion). Then, I'd slowly crank up the Line Adaptor's L/R level controls equally until the bass starts clipping (farting) and back off a hair. Then try nudging the amp's gain up a hair to see if you can get any more clean output.

Basically, you want all gain stages to clip simultaneously so one point in the system is not a bottleneck or needlessly adding gain (and noise) to the system...

Beyond this, the amp itself is more than likely combining (summing) L+R to a mono signal (and then inverts the signal to feed the other half of the amp to allow "Bridged Mode"), so it *probably* won't matter if the left and right sub inputs aren't perfectly balanced with regard to full output power.

Gain staging is a critical part of getting optimal performance out of any system, and is often one of the least understood concepts among cunsumers that DIY IMO...

:cool:

[mbowen89]

Ok guys, I will try this, thank you very much.

[mbowen89]

Hey guys... something has started to happen.

I have a switch inline with the sysrem, right. Well, from what I have deduced, if I turn my car off, leave the switch on, come back later, start the car up, sometimes my headunit resets, some digital stuff on my dashboard such as my MPG resets.

I think however, that if I start my car up with the switch off, it won't do this. BTW, the fuse I am using to get the sysrem is only on when car is fully running.


Do you think the problem is that when I am starting the car, it's trying to charge the amp, and for some reason messing everything else up? I believe I also noticed that my dome light dimmed as well. The car had no problem starting or anything.

[Randyman...]

Do you listen with your car turned off (not running)? If so, you likely drained your battery enough to allow it to start the car, but with severe voltage sag which would also cause some electronics to "reset" (like the MPG meter, etc). You could also be pulling more from your Alternator than it was designed for resulting in a simular "partially discharged" scenario, but adding one amp is not likely to cause such issues (3000Watts RMS in my ride, and the stock alternator is still cranking along - it is all in the listening habits IMO).

Aside from that, we need more info as to other accessories and crap that might be contributing to your overall accessory load...

:cool:

[deadlysyn]

Do you listen with your car turned off (not running)? If so, you likely drained your battery enough to allow it to start the car, but with severe voltage sag which would also cause some electronics to "reset" (like the MPG meter, etc). You could also be pulling more from your Alternator than it was designed for resulting in a simular "partially discharged" scenario, but adding one amp is not likely to cause such issues (3000Watts RMS in my ride, and the stock alternator is still cranking along - it is all in the listening habits IMO).

Aside from that, we need more info as to other accessories and crap that might be contributing to your overall accessory load...

:cool:

I have to agree. A single amp that small is not likely to over draw your alternator. My wifes 1994 Honda Passport has a 900 watt RMS amp, with (2) 40 amp fuses in it, and it is enough to dim the lights, but has been running off the same battery for 4 years. It needs a capacitor on the power line, but has been running without any issues for a while.

And Randyman, 3k is pretty beastly. I remember back when you were considered to be nobody in the car audio scene unless you had 1000 watts or more, and were running Pyle Driver subs, or some of the old school Orion, JL Audio (and is still up there in performance). PM me your system specs, I'm very curious to know what your rockin.

[mbowen89]

My remote wire is hooked into my power steering fuse. It ONLY gets voltage when my car is running. My amp won't even turn on unless I turn the car completely on, so no I don't listen to it with the car off.

The only thing I can think of is that when I have the switch on, my car and all the electronics are turning on at the same time the amp sees the remote wire come on.

[Weeman]

why is this getting so complicated? yes you need a fuse... IASCA says 18", that guy says 12." MECP??? Really? regarless you're getting the same output from the speaker (1watt @ 1meter). The human ear can only detect a difference of 3dB. The only way to get a 3dB difference is to aprox double your power, are you really saying you can tell the audible difference between 195W and 250W? I've got my money on you can't. Not to mention you're going to blow your sub anyway from underpowering it. As per most MOSFET amps you can go down to 2 ohms in stereo (this means 2 ohms, one terminal), if you're bridging it you min impedance is 4ohms. The difference in power output is negligible.