I have a dual voicecoil sub and a 2 channel amp. How can I take the input - 2 channels - and make it mono so I can run the 2 coils off the stereo channels without killing the sub?

Thanks.

 

what kind of amp? who makes it? model????

is the amp only for the sub or fronts and also for the sub?

 

Old Fosgate 500a2. Just for the sub.

 

What impedance are the coils on the sub? The A2 series was stable only at 4ohms when bridged(2 ohm stable in stereo mode). If you have 2 ohm coils you can wire the coils in series then just wire them bridged to the amp. If you have 4 ohm coils there's no way to get the most out of the amp, but the best wiring is the same as with 2 ohm coils, wire the coils in series then wire them bridged to the amp. This will be the same power output from the amp as wiring each coil to an independant channel, but won't have the ill efffects of trying to drive the coils in different directions from a stereo source. DO NOT wire the coils in parallel and try to bridge that amp, you will cook the amp real quick as the impedance will be too low, and too much current will flow, making the power FETs kick the bucket.

To wire the a2 series bridged just take the outermost speaker connecters. To wire as I've suggested take the + from the amp to the + on the first speaker, take the - on the first speaker to the + on the second speaker, take the - from the second speaker and wire it to the - on the amp.

 

yeah-- he's got the right idea. But in that last explanation the series wiring doubles the impedance of your speaker coils, as seen by the amp. However, bridging reduces the impedance by 1/2, so you will be running the amp at the same impedance as the coils like that. AFAIK, all RF amps I've dealt with (even the older ones) are stable down to 2ohms- most of the mono amps can even go below that.

Here's what to remeber:
series wiring: doubles impedance
bridging or parrallel wiring: reduces impedance by 1/2

So, if you try to do both of the latter at once, (two speaker leads into each bridge terminal)- and your coils are 4ohm, then you will be at 1ohm and your amp might work for a while, but it'll probably start smelling funny soon.

However, if you have 8ohm coils, this method would drop you to 2ohms- where you want to be to maximize power output.

here's a question: if the coils are 4ohm, would the bridging/series wiring (4ohm) produce the same power as hooking them up in stereo, just simply +- +- (also 4ohm)? I realize you don't want stereo-just wondering

I made sure to get the right impedance on my DVC's- I chose 4ohm, because I'm running the single DVC (two voice coils) in parallel off a single mono channel-(2ohms at the amp) This way I can get more out of the amp, compared to running it at 4ohms.

 

Bridging the amp looks like 1/2 of the load(heat wise) to the amp due to doubling the voltage. Putting an 8 ohm load on a bridged amp will put out the same power as showing the amp 4 ohms per channel in stereo wiring. The same as showing the amp a 4 ohm load when bridged will give you the same output as putting a 2 ohm load in stereo mode. When you bridge an amp you are doing the same as stacking a pair of batteries in series, you are in effect stacking the output voltage from the output devices. If you take a 1v battery and wire a 1 ohm load you will get 1 coulombs of electrons per second(using 100% efficiency), If you take two of those batteries and put them in series you will now have 2 volts, with the same one ohm load you will now have 2 coulombs(or 2amps) flowing per second. If you double the impedance of the load to 2 ohms you will be back to the same 1 coulomb per second(1amp) as using a single battery.

The current isn't the killer of the amps, its heat. When you make the devices put out more heat than the package can dissipate then silicon self destructs, the impedance of the driver is a current limiter so the output FETs don't make more heat than they can expel.


Not in order

8 ohm coils in parallel would lead to a 4 ohm load.

Series wiring is Rt = R1 + R2 +R.......
Parallel Wiring is 1/Rt = 1/R1 + 1/R2 + 1/R......

Running a DVC driver with a stereo amp can cause the coils to fight eachother if the channels aren't aligned exactly. Wiring the coils togethers makes it to the coils see the same signal.

I WOULD NOT recommend showing an older fosgate a.2 anything less than a 4 ohms load bridged. I cooked one in about 3 minutes.

I'm running a pair of 2 ohm solobaric L7s with the coils in parallel(1 ohm) and the drivers in series showing a 2 ohm load to a DX700 amp. I have them in small boxes tuned pretty high so there isn't a whole lot of spl, but I had the same speakers and amp in my previous car in a tuned shared port enclosure and it was just unreal, I snapped the rear view mirror 4 times in 6 months before I got smart and put 2 ton epoxy all around where it kept breaking, which in turn caused the windshield to crack lol. I never had to a sanctioned event but it was metered at 151.3db at a local shop.

too bad it had no trunk

 

Man- that's too much bass for me- but if that's what you want- looks like you know how to acheive it You were probably knocking parts off of other cars at stoplights...

Anyway, I disagree on the 2ohm load issue. I looked up an old maual on RF's site and noticed it talked about power outputs at 2ohms, etc. I dunno if it's old enough, though- its from '98.

http://www.rockfordfosgate.com/scrip...ted=1083781894

 

surprisingly it was pretty even when I had the back seats up and the ski passthrough thing open, I was feeding 120w(173 according to the birth certificate) a channel to a set of CDT 642dtm with the mids and tweets in kick panels and the midbass in the doors. Originally I was pushing 60w a channel to the front and also feeding a pair of braxial 6 in the rear deck but it was hosing up the image and was WAY bass heavy so I opted to bridge the 4ch amp and feed the crap out of the CDTs up front lol. It was enough to make your ears bleed lol



From that PDF
I found a few places about the web that say "Stable Into (stereo/mono) : 2 ohms / 4 ohms" for the a2 punch series.

I tried(I was installing in a friends car) to push a a brand new JL 13W7 with the 1.5ohm coils in series(measured at 2.97) with the 800a2 and it didn't even move it for a few minutes before it went belly up, and that was 3 ohms let alone 2. Many of the fosgate power series amps were 1 ohm stable in stereo, 2 ohm stable in mono, he ended up using a power T8002 and it hits pretty damn hard, although if JL had some normal human coil impedance it would probably be even more ferocious.

 

I have to check the sub. It's an older Bazooka 8" "Reference" series with a DVC driver. I was asking because I also have a Kappa Perfect 10.1 DVC I want to put in my RS. This one has dual 4ohm coils, and I haven't boght an amp yet. Considering a PPI unit.

 

I'd go with a single channel, 'mono' amp if it is just for the sub. If you've got two 4ohm coils to hook up, you're best bet at getting the most out of any amp is running them parallel (2ohms at the amp) to one single channel. The crossovers on them are more useful for low freq. and they usually have somekind of bass boost control (RF has a punch bass remote you mount near the drivers seat- very useful- not very familiar w/ PPI- but have heard good things). Not to mention their uncanny stbility at low impedances (some below 1ohm) It just doesn't make sense to buy a stereo amp that's built to reproduce midrange and highs when they make amps suited just for your needs. Also, they dont draw near as much current as multi-channel (2+) amps, due to their more efficient 'class D' circuitry.

my .02

 

Just to clarify, I currently own: 1x Bazooka 8" DVC sub and an old Fosgate 500a2 (pre bass remote)

I plan to use the above setup in my daily driver since it's extra gear that I already own. I wanted to find a way to make the L+R signal coming from my HU be mono but still L+R (or 2 channels, depending on how you say - but NOT stereo) so I can us the 500a2 in stereo with the Bazooka and not kill the woofer.

I also currently own an Infinity Kappa Perfect 10.1 DVC that I plan to use in my 2.5RS with an amp that I need to pruchase. IMHO a mono sub amp would be best for this use. I plan to run the VC's in parallel at a 2 ohm load and get an amp that is 2ohm stable.

 

You could safely use the series bridged wiring that illusion explained (use the outermost terminals + -+ -, and run the positive bridged amp terminal to one of the positive terminals on your coils (a single wire), run the negative bridge terminal to the neg. on the other coil (again, a single wire) and finally run another single wire from the remaining + on one coil, to the remaining - on the other) It may look weird if you haven't used series wiring before, but yes. It works fine. And is a safer bet that parallel when concerned about impedance. And you said it's a 8 in bazooka tube and a 500a2? Trust me. You dont need nor want all of the power out of that amp- so running at 4 or even 8ohms would be perfectly fine.

Nice choice on the 10" Kappa Perfect- those are pieces of work. I had a pair of 'em (SVC's) and it was the most musical, true-to life bass I'd ever heard. The 12"s can reach a little deeper, but I still prefer the 10" for the clarity.