wiring for stereo or bridged mono. does this work?

So I have a basic crown xls 202 that works in stereo and bridged mono. I'm trying to build a couple 18" subs for them with two 4 pole speakon inputs each. in order to get a little more power out of the amp before i can afford a new one, i want to bridge the amp and daisy chain the cabinets so they run on a 4 ohm load instead of two 8 ohm loads. I attached a simple diagram of how i want to wire the inside of each cabinet. I'm just wondering if this is a "legal" setup or if i'll be running into problems with it.
thanks.
 

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Xoc1

Member
2008-11-08 8:25 pm
Devon UK
The XLS 202 can deliver 200w per 8 ohm speaker in stereo, or 600w into a single 8 ohm speaker.
It is not capable of running both speakers as a 4 ohm load in bridge mode.
If you do this it will probably overheat and shut itself down.:(
How you upgrade is up to you? Maybe buying a another XLS 202 is an option.
1.2KW of bass from 2off 18" speakers would be OK!
Personally I would use it as a HF tweeter amp in a 3 way active setup, or use it for monitors.
 
Given sufficient cooling of the amplifier (ie, some fans or something), you might be able to prevent it overheating.

It would, however, be much safer to run the amplifier at 2x200w into 8ohm. Bridging the amplifier into 4ohms would make each channel see 2 ohms, which it's not rated for.
 
wait, i was thinking that this setup would be running a single 4 ohm load, as in two 8 ohms daisy chained in parallel to make a 4 ohm load. which i believe this amp is able to hold that. if i'm wrong please correct me. if not, i do plan to upgrade to a much more powerful amp that can hold a bridged 4ohm load, and use the 202 for a hf amp like Xoc1 suggested. so i was more interested in knowing if i could use this wiring and run either in stereo or bridged without any problems.
 

Xoc1

Member
2008-11-08 8:25 pm
Devon UK
Bridge Mode -
Speakers are wired across both amplifier +ve outputs. Outputs are run out of phase with each other. This doubles the potental voltage, the amplifier struggles to provide double the current. Connect both 8 ohm speakers this way and this doubles the current again, so each channel of the amplifier acts as if it has a 2 ohm load - This is only possible with very capable amplifiers and is rarely optimal.
Parallel Mode-
Both sides of the amplifier are coupled together to make a mono amplifier. The output potental to each speaker is unchanged so the current (& power) to each speaker is unchanged.
Advantage is a 4 ohm per channel amplifier can drive a single 2 ohm load.
This is not an option with most amplifiers, and probably will damage the amplifier.
Either way this small crown amp will be toast.:redhot:
 
Running each cab off its own channel at 8 ohms, or bridged together at 4 ohms, the result is identical. As it's easier to wire each cab with its own lead I would go for the individual channel method.

Richie, are you sure?

Bridged 8ohms vs 4ohm stereo, I'd agree. Perhaps you've mixed the numbers up?
not only Richie is sure, I am sure as well.

a pair of bridged amplifiers delivers double the power into double the load impedance.

If you have a 220W into 8ohm amplifier and bridge it with another 220W into 8ohm amplifier you get 440W into 16ohm.
Bridge the amps and series the 8ohm speakers and you get the same power delivery.

Now let's try and be too clever for the knowledge we have.
Let's bridge the amps and feed the resulting power to ONE 8ohm speaker.
A pair of very good 40hm capable amplifier will be capable of delivering at least 700W into that 8ohm load. A crap pair of amplifiers will shut down or damage themselves with that load if driven medium, never mind hard.

If someone wants to be real stupid, then connect the 8phm speakers in parallel, resulting in a 4ohm load, and attach that to the bridged pair of amplifiers.