XPA-4 Gen 3 "Bi-Amping"

[metaldaze]

Finally I found the gold at the end of the rainbow. This post is under amplifiers, because although its directly related to this speaker, my question really is about my amp. This 40 year old floor standing speaker is the Ohm I. It sounds remarkably good for its age. I'm no stranger to Ohm products but had yet to ever hear this speaker. Needless to say I'll be upgrading the pair through the manufacturer as I can. It's claim to fame has been the ability to accept ~1,500 watts without compression or breakup, achieving a full 'concert hall'  experience at home provided you have the space and amplification. It also does a lot of other things very very well besides just getting loud. I plan to critically listen to them more once they have been brought into the 21st century. 

As it pertains to my amp, the I's have the ability to be truly bi-amped. The top drivers and front high tweeter are contained in their own space using the top port. The subwoofer and lower port are within a space all their own. 


Right now I have them running on 'normal system' using 2 of the channels in my XPA-4. My pre-amp has Two summed subwoofer pre-outs and I know the crossover frequency of the speaker subs to be 100Hz. 

As they sit hooked up now at 4 ohms they're getting 490 watts/channel, which is max for the mono high power blades. That figure is rated for 0.1% thd, but is only using around half of the amps total power supply, correct? 

So if I use the 2 subwoofer outputs and connect them to the other two blades, bi-amping each speaker. Then I would be tapping into the full potential of the amplifiers power supply? Essentially like a DR-2 (but not really since mine is not fully differential and hooked up single ended anyway)

In this way I would be feeding each speaker around 800 watts instead. Or is this not entirely correct since its still sharing the same power supply so just splitting the demand over 4 blades instead of 2 won't make that much of a difference? I'm just trying to get some outside input before I buy extra cable and go fiddling about in awkward positions for science   Thanks 

Cheers 

[creimes]

I didn't know they made Atmos speakers back then

[metaldaze]

Oct 11, 2019 22:42:28 GMT -5 creimes said:

I didn't know they made Atmos speakers back then

hardy-har-har   

[repeetavx]

It's the old acoustic power vs electrical power argument. Usually two channels working half as hard will still develop the same SPL as one channel working "harder". I like bi-amping because I believe that the counter EMF is divided. Allowing your amps to operate easier and thus more efficiently (less distortion). Others here disagree with me. The bottom line is that every speaker is different, and until you try it, you won't know how your speakers will sound.

So save yourself work and hook them up "normally", or be adventurous and experiment.

P.S. I'd make sure that you hit that Normal/BiAmp switch with some contact cleaner.

[metaldaze]

I'm leaning towards being adventurous to see if it really would up the two channel experience. I've already given them around 30 watts/ch RMS in the two channel configuration, and I admit I'm alarmed at the power these things just accept with grace.

As for the contact cleaner, that second picture is actually a stock photo but all the switches on Ohm speakers are self cleaning! & so in essence I did just that by working all the contact switches a few dozen times.

[metaldaze]

In the manual It states 260 Watts/channel all channels driven for my XPA-4. But that rating is for 8 ohms, 4 ohms it doesn't show.

I've done some simple calculations and come up with 416 watts/channel into 4 ohms, all channels driven for the gen 3 XPA-4. This gives me round about 832 watts/channel vs 490 using only two mono blades.

Doubling the power only results in an increase of 3db, but as repeetavx said I'm hoping it will render a cleaner signal into the speakers, even when pushing them hard.

If Keith or anyone who has more insight into the output figures of this amp, please weigh in and let me know if I'm on the right track