Wiring two stereo channels to one sub?

[ancorp]

I have a cheap Soundstorm F4.400 amp (4 channel, non bridgeable, 2 ohm capable).

I want to use it to drive two small drivers in stereo on channels 1 and 2, and to use channels 3 and 4 to power one small 4 ohm subwoofer. I realize that bridging is not going to work like on most higher end amplifiers. What if I combine the positive signal on the left and right and feed them to the sub, therefore giving each channel a 2 ohm load (which the amplifier is capable of doing apparently)? Would the amp survive that and give me mono, while keeping stereo on the other two channels?

Regards,
Alex

[richie00boy]

You are likely to blow both channels. You need a dual voicecoil sub.

[ppia600]

Seller description says its bridgeable to two channels, do you have a pic of the end with the speaker and power terminals? If it is bridgeable you can bridge the two rears into one 4 ohm sub with no problems, that is the correct way to do it.

[markhauguel]

Look into Tri-Mode or Multi-Mode wiring. This is basically running the two stereo speakers separately off of the discrete channels with a high pass filter and the sub across the bridged channel with a low pass filter to keep the impedance more constant. I hope this helps.

Tri-Mode or Multi Mode Amplifier Operation

[luka]

4ch should be always bridgeable

[ancorp]

Thanks for the replies, much appreciated. Nowhere in the manufacturer manual nor on the amp itself does it mention bridging capabilities though...

The amp has a lowpass filter switch for one pair of channels, and a highpass for the others pair, thus I wanted to run some small speakers with the high pass channels, and one sub with the lowpass channels.

How would one bridge it?

Regards,
Alex

[Perry Babin]

With the amp powered up (no audio input signal), what is the DC voltage on each of the speaker terminals (black probe on the amp's ground terminal)?

If they all have ~6v DC, the amp is a 'chip amp' and each channel is already bridged.

Driving the positive woofer terminal with the positive terminal of one channel and the negative woofer terminal with the negative terminal of the other channel would allow both channels to be reproduced by the woofer but would not increase the output (compared to connecting the woofer to either channel).

[ppia600]

Well if its not bridgeable like mentioned here NEW SoundStorm F4.400 4-Channel 400W Car Amplifier/Amp - eBay (item 290514606588 end time Jan-19-11 20:48:32 PST) then you'll need a dual voicecoil sub like richie mentioned. If its not bridgeable yet is still 2 ohm stable a dual 2 ohm voice coil sub would draw the most power from the two sub channels. You would just wire one voice coil to each rear/sub channel.

Another way to check if the amp is bridgeable is to use a meter to check continuity between any two of the sub channels terminals (amp off). If two of the terminals a directly connected according to the meter (0.0-.9ohms approx), then the other two terminals would be the one you would bridge a single voice coil sub on.