Hi, I have two rockford 4ohm 12's which are being powered by a Profile Callifornia 400 bridgeable amp. I decided to take a chance and run both negatives into the negative side and both positives into the positve side. (it is now bridged) The way I have the subs wired (independently) has made them 2ohm.

I now get double the base, but my amp gets REALLY HOTT! too how to touch.

Is bridging two subs from a 2 channel amp ok??

Is my amp getting hot b/c now i am running at 2ohms?

Thanks, Ben

 

Hey man, you might wanna be careful bridging that Profile amp down to 2ohms. Most likely, after about a half hour (maybe sooner), that amp will self-destruct. That's not the best amp out there, and running it at 2ohms is definitely shortening it's life span. I would run it at 4ohms until you get a better amp.

My two cents...

 

those amps are only 4ohm stable bridged. You running your amp on very limited time.

 

dont listen to them, just put a smaller fuse in the amp, so that if it starts to short, it might save it.

i ran an old fultron tidal wave 400 at 2 ohm mono, it sounded alright, for a LONG time, and i had it sitting in a shoe box, because i didnt care enough to do a real install, until i got my good stuff.

hell, get a dc current fan, wire it to the remote and the ground, and screw it to your rack so it blows over the heatsink/cooling fins.


adam

 

First: Your amp is NOT running at a 2-ohm load! It’s at 1 ohm per channel. When you bridge an amp each cannel “see” half of the load! So your 4-ohm stable amp is running at 1-ohm. You said the amp is getting hot. There are only two thinings that will kill a transistor, heat and a hammer! Heat WILL shorten the life of a transistor.
Second: “dc current fan, wire it to the remote and the ground” NO NO NO. Your remote out of the radio is NOT designed to drive a fun! This vary well could damage the HU. Most HUs remote out is only a 200mA output MAX.
Third: “just put a smaller fuse in the amp”? This will do NOTHING to help your amp, NOTHING. “so that if it starts to short, it might save it”. They don’t “start” to short, they just short. If the fuse blows because a transistor is getting leaky, not shorted, the transistor is ALREADY bad.
Listen, all I do all day is fix car audio equipment, installs like this are why I have a job.

 

1 ohm stereo is 2 ohm mono.




adam

 

i have never seen a fan kill a head unit through the remote, but i should have specified, i have my remote on a relay, and alot of people run remotes from the firewall, as the head unit does not always put out enough power to turn on multiple amps.


adam

 

I just got the parts in to fix a Clarion RDB245d. The customer was powering two fans, a light, and three amps. Your right, you'll be fine if you use a relay.

What your friends are seeing is what I was saying. The radio can only supply a limited current out of the remote output, 200mA as a rule of thumb. If you try to pull more from the radio the small switching transistor for the remote output will over heat, and in some cases shot. And yes, in these cases the radio is damaged. If that switching transistor goes shorted, the output of the microprocessor is driving a dead short, so now you have two parts to replaced, the switching transistor and the processor. Most new radio prevent this by using digital transistors, these will limit the output current by a great voltage drop at the internal emitter and base resistor. So in short, it is more common in older units but the potential is still there. If you are going to tell some one to do it and not tell them to use a relay they could damage there HU. If someone is going to try it they should be aware of what they are doing.

 

I also run my amps off a relay- the factory's power antenna relay! My remote runs to my power antenna relay.. and the power antenna has been missing for years. (Pulled it in '95.) Then the relay kicks on the two amps.

And I agree with NEEDAZ; it's a one ohm load on the amp.

Giving a 2 channel amp- 2 speakers, each speaker is 4 ohms, 1 speaker per channel, each channel sees 4 ohms.

Giving a 2 channel amp- 1 speaker, the speaker is 4 ohms, channels bridged, each channel sees 2 ohms. The amp "total" is seeing 4 ohms. This is how amps rate themselves as being "bridged into one channel".

Combine those above two scenarios, and you get:

Giving a 2 channel amp- 2 speakers, each speaker is 4 ohms, channels bridged, each channel sees 1 ohm. The amp 'total" is seeing 2 ohms.

Be careful not to melt the amp.

 

it does not make a half a **** what ohm rating each channel sees. what matters is the total ohm load on the amp and whether or not it is in the range of acceptable.

i would consider two ohm mono acceptable, i have run many amps this way, trying to overcome a cheap amp.

i have done it on my systems, and others' after explaining the possibility for failure.


it is a risk worth taking, hell, they always last long enough to save up for a better one.

adam

 

Calm down onebadwagon, I’m not trying to attack you and I’m sorry if it came across like that. I’m just trying to make shore TBI89Formula knows ALL the info he can on doing this. This board is for sharing information. But a couple of things should be cleared up. I think there is some confusion out there on bridging an Amp. If you bridge an Amp each channel “see” half the load.
“it does not make a half a **** what ohm rating each channel sees.” If the amp is rated as a 2-ohm stable amp, it means that each channel can drive a 2-ohm load. If an amp is 2-ohm stable and you bridge it into a 2-ohm load each channel has a 1-ohm load and in this chase the amp is driving a load below what the amp was designed to drive. Even thow the amp doesn’t say that the 2-ohm stable rating is for each channel, that what it means. The load on each channel IS what matters, not the “total load”.
“i would consider two ohm mono acceptable” If the amp is only rated at 2-ohm stable the manufacture doesn’t consider it acceptable.
“it is a risk worth taking, hell, they always last long enough to save up for a better one.” But in your other post you didn’t explain the risk, which is all I was trying to do. And it is up to TBI89Formula if he wants to take that risk. It’s his amp and he might not want to replace for some time, it’s his call

 

okay, unlike other boards, everyone on this board thinks you are getting pissed off, kicking and screaming when you type a four letter word.

im not, im stating that, the total load on the amp actually is what matters, not to say that a total 2 ohm load on a 4 ohm stable amp is safe,


so are you saying if i put 2 ohms on one channel and 8 on the other that it would have overheating problems? NO, because the amp isnt seeing a two ohm load,


and you are right, i did not go out of my way to further explain the dangers of running an amp at a lower impedance than its rated for, however i did list things that would prevent failure.

mainly fuse the amp with a smaller fuse than what it came with, and run a fan, to keep air moving across it, and then i listed an experience with a fultron (cheap crappy amp) at a MUCH lower impedance than it was rated for.

that amp was only supposed to be 4 ohm STEREO rated, but i was saying that i had it running at 2 ohm mono, for a long time. so what its rated at doesnt really make a half a crap, as long as you try to keep air moving over the amp, and know what youre doing.



adam

 

“everyone on this board thinks you are getting pissed off, kicking and screaming” I don’t think that, just trying to keep things civil. They can get out of hand some times.

“so are you saying if i put 2 ohms on one channel and 8 on the other that it would have overheating problems?” If you did this and the amp as only 4-ohm stable one channel would. Most amps use four output devices per channel, whether they’re bipolar transistors, or FETs, Or MosFETs, most of the time there are four. So in this setup four of the outputs would get hot. On the exterior of the amp you would probably not notes the extra heat. The entire exterior or the amp is heatsink and the extra heat would spread over the case of the amp. But if you opened the amp and checked the outputs them selves you would fined that the four of them on the channel with the 2-ohm load WOULD be noticeably hotter then the four of them on the channel with the 8-ohm load. Heat will kill a transistor, or at the vary least weaken it. It IS the load that the channel sees that is what matters. Think about it like this. Each channel is independent of one another. Each cannel is like its own amp. Once the signal gets past the pre-amp stage the right and left channels share nothing but supply voltage. Most of the heat that an amp makes comes from the output stage, that’s where all the work is done. The rest of the heat will come from the power supply. The per-amp stage makes almost no heat.

 

As an electronics technician, I have to agree with NEEDAZ on this...You are at 1 Ohm per channel. Lots of people do what you are doing, and in some cases, the amp MAY handle it...for awhile. The simple fact that the amp is too hot to touch is proof enough that your are on the fast track to eBay to search for a new amp. Every Xistor, resistor, cap, inductor, etc. is not operating at it's rated capacity because they are all cooking inside the amp. That not only reduces your power, it turns your signal quality into pure crap. A fan wired to the remote won't help, either, as .2A is not enough current to drive a fan enough to cool an amp that is hot to the touch.The remote WOULD work, however, as a turn on relay for your fan, which you could wire to some other power supply.