Bridging Amplifier

[RENDOG]

If you bridge a Crown xti4000 and connect one 8ohm speaker, are you still at 8ohms?

[doncolga]

I believe so.

[Bill Fitzmaurice]

If you bridge a Crown xti4000 and connect one 8ohm speaker, are you still at 8ohms?

If you don't really, really, REALLY know what you're doing do not bridge. It should only be done if one channel is inadequate to deliver sufficient voltage swing. And if you don't know the answer to that you don't know what you're doing. Really.

[doncolga]

I just googled voltage swing...wasn't sure what that was.

http://www.tonmeister.ca/main/textbook/node154.html My new sub amp is about 1/2 of my old one (Mackie M 2600) and this one I'm running mono instead of bridged, using one side into 4 ohms. Gigs so far have been 25-35 volts which has been plenty loud enough.

That Crown is alot like my old one...definitely would not run bridged on 3012 lf's...WAY too much if I'm not mistaken. I believe even if you run that at 8 ohms per side you could still reach 72 volts, which could overload the 3012's... The amp I use now specs closer to the XTI 1000.

[doncolga]

Be careful with that. Be sure your amp is not going to put out more volts than your driver should be taking. I just checked my limiter again and measured my amp since I haven't looked at it in a little while. When I send it Bink test tones (30-90 hz tones, 30 sec each) with the amp wide open (IMPORTANT: NO SPEAKERS CONNECTED) the amp can get up to 52 volts with no limiting, then I've set the threshold on the limiter to clamp it at about 48 volts. With that, gain reduction actually gets up to 8-10 dB depending on the frequency, but usually on music is less or alot less depending on the song content. Ludacris hits GR pretty hard while the Mavericks not quite so much.

[netwerks]

There is no reason to bridge an xti 4000 for use with any BFM designs.

[RENDOG]

Good advice.

I'm not bridging the amp.

What load does a mobile/club amp "see" when it is ran bridged to one 8ohm speaker?

[Dave Non-Zero]

Each channel 'sees' half the impedence, so bridging into 8ohms means each channel is working as if it is running 4ohms.
Similarly, if you bridge into 4 ohms, each channel is working at 2ohms.

[RENDOG]

Thanks Dave.

So there are very few situations where one would need to bridge an amplifier?

[Bill Fitzmaurice]

Thanks Dave.

So there are very few situations where one would need to bridge an amplifier?

This:

It should only be done if one channel is inadequate to deliver sufficient voltage swing.

[SoundInMotionDJ]

Each channel 'sees' half the impedence, so bridging into 8ohms means each channel is working as if it is running 4ohms.
Similarly, if you bridge into 4 ohms, each channel is working at 2ohms.

Almost.

The amp has an internal power supply that converts wall power (voltage & current) into power to be supplied to each of two channels. Ultimately, this power supply and its ability to dissipate heat is what sets the maximum power output (with voltage, current, and impedance related by Ohm's Law) that the amp can safely handle. Amps are designed to work over a range of voltages and applied loads. In the end, the amp will be limited to a certain amount of current that can be supplied to the load....and whose heat can be safely dissipated by the power supply.

In bridge mode, both channels are combined to drive a single impedance load. This will double the voltage swing compared to using the two channels independently. With a constant load, doubling the voltage swing will also double the current supplied. Recall that the amp is limited to a certain maximum current that can be sourced from the power supply. To hold the current constant, when the voltage is doubled, the impedance must also be doubled. If that is not the case, then the amp will overheat and either shutdown or damage itself.

That is why the impedance minimums double when an amp is used in a bridge mode.

--Stan Graves

[RENDOG]

Thanks. Great information.

[Spoon]

RENDOG, you might like this article. Pretty cool way to get your amp to "go to 11."
http://www.prosoundweb.com/article/figh ... _delivered_/

[CoronaOperator]

Pretty cool way to get your amp to "go to 11."

In all my audio experience, asking TOO much from ANY part of the audio chain gets really, really expensive, really, really fast!!!!!

[SoundInMotionDJ]

In all my audio experience, asking TOO much from ANY part of the <insert_gear_for_current_favorite_hobby> gets really, really expensive, really, really fast!!!!!

Fixed it for you.