View Full Version : JBL S800 Amplifier 4 OHM LOAD CAPABLE?

07-03-2008, 07:50 PM
I have a SLEW of S800 amplifiers (run K2's, SK1000's, etc) and wanted to use 3 as monoblocks to a 4-ohm speaker. I know they are rated at 800W into 8 ohms in a bridged configuration, does anyone know what they will do bridged feeding a 4ohm load? Power ratings anyone? Manual doesn't state.

07-03-2008, 09:27 PM
Dunno about that amp specifically, but if it's not rated to drive 2 ohms per
channel in stereo, it's unlikely to be happy driving 4 ohms bridged,
especially at higher levels.

07-03-2008, 11:12 PM
Here is a link to the page:http://www.jbl.com/home/products/product_detail.aspx?prod=S800&Language=ENG&Country=us&Region=USA&cat=AMP&ser=SYN

And I see this here: GeneralPower Bandwidth5Hz – 100kHz +0, –3dB Power Output200 Watts in Stereo mode into 8 ohms;
800 watts in Bridged mode into 8 ohms

I don't see anything here that recommends a 4 ohm load in bridged mode.
Just found this in the owner's manual: http://www.jblsynthesis.com/products/product_detail.aspx?prod=S800&Language=ENG&Country=US&Region=USA

NOTE: The minimum load impedance that this
amplifier can handle safely is two ohms per channel in
stereo operation, and four ohms in mono. Using lower
impedance loads can damage the unit and will void
your warranty!

Good Luck!


07-04-2008, 08:22 AM
Any power amplifier that uses a single power supply for the HV is not going to give dependable performance into 2 ohms per channel. It will work but the heat buildup and the high currents will cause issues eventually.

This is REALLY a problem if they are multi-channel amps ( like the ones you always add to your auction pictures ). 2 ohms is just not good for anything but very specific SR use with HD amplifiers.

Check the amp's schematic to see what the case is.

If you have a dual LF cone speaker consider running one channel into one cone and the other into the other cone/crossover. You would need to duplicate the LP crossover components and rewire but it would work. This would be considered a hybrid bi-wire.


07-04-2008, 08:50 AM
Thanks for the responses. I am not using a 2-ohm load speaker, rather a 4-ohm nominal, 3.2 minimal. I would never use the S800 for a 2-ohm speaker - Crown K2's would do that for me. I am running a normal 80hZ 3-way 94.5 efficiency, 4-ohm speaker in a dedicated theater. Crossed at 80hZ, I don't think the JBL amplifiers would be an issue.

And agree subwoof, the 7150's would not feed 2-ohm either - I am not even sure I would use those for a 4ohm nominal load either.


07-04-2008, 11:31 AM
If you bridge a 2 channel amplifier, each channel sees 1/2 the load Z - this is basic electronics.

This is why most manufacturers do *not* specify bridged 4 ohm operation..

And 1/2 of the 3.2 minimum is 1.6 so not only will the amp be woofing hard, a LOT of loss in the speaker wire will change the dampening equation...


06-30-2010, 11:12 PM
sounds good to me :crying: