[maviduya]

I'm still googling for the definitive answer, but I'd like to ask the experts here:

Is it safe to use only 2 channels of a 4-channel amp?

Backstory:
I have a sub and a 4-chan amp already from a previous install. I know I can get a mono or 2-chan amp to drive the sub but I really don't want to spend if I don't have to?

I did a test-run with this setup and observed that the 4-chan amp was much warmer than the main amp from which I was tapping into RCA outputs, with the sensitivity turned way down.

I'm concerned with the heat from the 4-chan amp. I drove around the block listening to music for about 10 minutes and the 4-chan amp was just a bit too warm...

Thanks in advance for any advice!

[david in germany]

Depends on the amp. If you are able to bridge 2 channels to each speaker it makes it easier and if the amp is capable of the speaker impedance you will normally make more power.

[e90bmw328i]

If you connect 4 speakers to 2 channels, the output from the amp has to drive all speakers. Do read about serial and parallel conmections. Neither is really good for the amp. I would just pick up a small mono amp for the sub. You dont want to take any risks with heat/fire hazard on such an expensive car

[maviduya]

To be clear: I bridged two channels to drive the sub. The other two channels I've left empty (both the speakers output and RCAs input). The sensitivity of the empty channel is turned all the way to minimum. The sensitivity of the bridged channels driving the sub is about 1/8th of total (so not a lot).

Yet it ran warm. That's my worry and question: is the warmness normal or should it run "cooler" because only two of its four channels are being outputed (spelling?).

[kaigoss69]

Originally Posted by maviduya

To be clear: I bridged two channels to drive the sub. The other two channels I've left empty (both the speakers output and RCAs input). The sensitivity of the empty channel is turned all the way to minimum. The sensitivity of the bridged channels driving the sub is about 1/8th of total (so not a lot).

Yet it ran warm. That's my worry and question: is the warmness normal or should it run "cooler" because only two of its four channels are being outputed (spelling?).

It would help if you told us what amp and what sub and its impedance. It needs to be determined whether the load on the two channels in bridged mode is safe or not. Leaving the other two channels unused is perfectly fine and will not hurt anything.

[maviduya]

Amp is xd400/4. Sub and enclosure are JL Audio. I will have to remove the sub from its enclosure to learn the impedance/model of the sub, unless there's a way of discovering the impedance without disassembling the sub from enclosure.

[maviduya]

Sub+enclosure is CS112RG-W1v2: One 12W1v2-4, sealed enclosure, rear-firing, gray carpet finish, 4 Ω final impedance, steel mesh grille included.

Amp specs for Bridged @ 4Ω: 200 W RMS x 2

So it seems the sub and amp both show 4ohms as configured.

So I'm guessing and assuming that the warmth of the amp is sorta normal

[david in germany]

Originally Posted by maviduya

To be clear: I bridged two channels to drive the sub. The other two channels I've left empty (both the speakers output and RCAs input). The sensitivity of the empty channel is turned all the way to minimum. The sensitivity of the bridged channels driving the sub is about 1/8th of total (so not a lot).

Yet it ran warm. That's my worry and question: is the warmness normal or should it run "cooler" because only two of its four channels are being outputed (spelling?).

You need to learn what the gain control is for. Just because it is 1/8 does not mean you have it set anywhere near correct. gains are to signal match the input. You need a good measuring tool to measure the signal in and match it to the gain on the amp ( signal is around 2v, gain should be set at 2v so the amp is not producing a clipped output and getting too hot) 1/2, 1/4 or 1/8 meen nothing on a gain pot.

Originally Posted by e90bmw328i

If you connect 4 speakers to 2 channels, the output from the amp has to drive all speakers. Do read about serial and parallel conmections. Neither is really good for the amp. I would just pick up a small mono amp for the sub. You dont want to take any risks with heat/fire hazard on such an expensive car

How long have you been involved in car audio? Many amps run even more efficient in those type of configurations so that statement is incorrect.

I do agree that he needs to learn about series and parallel configs but because of impedance loads as I mentioned in my first post.

Originally Posted by maviduya

Sub+enclosure is CS112RG-W1v2: One 12W1v2-4, sealed enclosure, rear-firing, gray carpet finish, 4 Ω final impedance, steel mesh grille included.

Amp specs for Bridged @ 4Ω: 200 W RMS x 2

So it seems the sub and amp both show 4ohms as configured.

So I'm guessing and assuming that the warmth of the amp is sorta normal

I would reccomend that you look for either a 2 channel bridgeable amp or a small mono amp that put out the proper 50-300w at 4 ohm as jl Audio reccomends for that enclosure.
The warmth is normal but if it is HOT, your gains may be set too high.

An after thought, is this a hifi or logic 7 system? You could use the extra channels to power the underseat woofers.

[maviduya]

sigh...the impedance question i have answered...yes the adjustment of its sensitivity should be more scientific...thanks to all!

[david in germany]

Originally Posted by maviduya

sigh...the impedance question i have answered...yes the adjustment of its sensitivity should be more scientific...thanks to all!

not impedance statement not directed at you brother.

By the way, if you are into car audio and may do other installs, look into a SMD dd-1 a great tool to use setting gains.

[csu87]

Yes you can run 2 out of 4 channels with no issue.

Yes you can run your 4ohm sub bridged on the 2 channels.

Yes you need to properly set your gains. Amps do get warm, but clipping will make it hot, fast; and will ruin your sub/amp.

Originally Posted by e90bmw328i

If you connect 4 speakers to 2 channels, the output from the amp has to drive all speakers. Do read about serial and parallel conmections. Neither is really good for the amp. I would just pick up a small mono amp for the sub. You dont want to take any risks with heat/fire hazard on such an expensive car

Yes you need to never listen to anything this guy says on car audio.


Also, you can check the impedance of the sub by measuring it at the sub leads. No need to remove from box as long as you know how you wired it.

[e90bmw328i]

Originally Posted by csu87

Yes you can run 2 out of 4 channels with no issue.

Yes you can run your 4ohm sub bridged on the 2 channels.

Yes you need to properly set your gains. Amps do get warm, but clipping will make it hot, fast; and will ruin your sub/amp.




Yes you need to never listen to anything this guy says on car audio.


Also, you can check the impedance of the sub by measuring it at the sub leads. No need to remove from box as long as you know how you wired it.

Yes Mr.Audio expert. I am completely noob at this but has basic sense to not do stupid things with my car.

I had misunderstood that he was running multiple speakers using a single channel. Thats why I was suggesting him to not do that based on my reading.

[csu87]

Originally Posted by e90bmw328i

Yes Mr.Audio expert. I am completely noob at this but has basic sense to not do stupid things with my car.

I had misunderstood that he was running multiple speakers using a single channel. Thats why I was suggesting him to not do that based on my reading.

running multiple speakers in series and/or parallel on a single channel does not hurt amps either.

[maviduya]

My thanks to all who commented! I'm running the amp and sub with no worries. You guys really helped!