I have a 2 channel amp that is 100 RMS into 4 ohm stereo and 225 into 4 ohm mono and is 2 ohm capable. A friend of mine has 2 older but BNIB 8" subs, (I forget right at the moment but *think* they're MTX, definitely 90w RMS, 170 max), with an appropriately sized, nice home made box, (3/4" MDF, screwed and glued). For beer money, I can get them but they are 8 ohm speakers. I realize this will cut my power/sound output. But, I'm concerned about over driving the speakers or amp. As I see it, I have 2 choices:

A) 1 channel into one speaker (8 ohm load)

or

B) Bridge the amp to mono and wire both speakers, parallel, to the mono output (4 ohm load, I'm pretty sure)

Here's what I'm thinking:

A) Less efficient but will not be over driving the speaker/amp.

B) More efficient but chance of too much power output, (especially to the speakers. The amp *should* handle it.(?) )

I'm leaning toward "A" but having little/no experience with electrical theory, (ohms are a logarithmic function, right?), I need a little guidance so I don't blow speakers or end up with a flaming trunk.

Not looking for thump. Just some bass "fill".

TIA

 

something sounds flakey with the amp specs. normally the bridged power is not doubled that would be the power at 2ohms. pretty much either connection is going to be 50w speakers. unless thats really the right spec

 

What?

 

sorry wasnt looking at something right. the stereo hookup would give you like 50w per speaker but hooked in parallel amp bridged would be like 112.5. sounds like a good match.just make sure the gain is set properly

 

Bridged power should be the sum of the stereo power at 1/2 the impedance.

In other words,

8 ohm bridged power should be the sum of the two channels at the two-channel 4 ohm rating.

4 ohm bridged power should be the sum of the two channels at the two-channel 2 ohm rating.

2 ohm bridged power should be the sum of the two channels at the two-channel 1 ohm rating.

The latter is why many amps don't like 2 ohm loads in bridged mode because the amp feels that load as 1 ohm per channel. So, if the amp isn't rated for 2 ch operation at 1 ohm per channel it's almost certainly not rated for and won't like 2 ohm bridged operation.

Likewise, if the amp isn't rated for 2 ch operation at 2 ohms per channel then it's almost certainly not rated for 4 ohm bridged operation and probably won't take kindly to that either.

 

As to the OP, myself, I'd just try it both ways to see which you prefer. Neither way will hurt anything. A good rule of thumb is if it sounds bad, it is bad, at which point you turn it down some.

 

Gotcha'.

Thanks to all for the help.