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Why are they doing this?

Kinda vague, huh? I'll elaborate. I have Emotiva XPA-1 monoblocks driving Magnapan 20.7's. Before that they were powering Mag 3.7's. They are 1000 watts into 4ohms. They never clipped. I did play them loud but not ridiculously loud. These amps have blue led meter lights that move in sync with the amp output and they would peak a little passed halfway. Occasionally a bit higher. Recently I added a pair of REL G2 subwoofers. They are connected one left and one right as per the manual. That would be to the speaker posts on the amps with the supplied neutrik cable. Upon connecting the subs, the blue led's no longer move. (Yes, I've checked the switch that turns these on and off) Also, three times now, the amps have clipped, once left channel and twice right channel. It was at a pretty good volume but not where it was outrageous. I talked to a tech at Emotiva and first off, he had no knowledge of REL subs and how they are connected. After I explained it he was kinda at a loss for words having obviously never heard of connecting subs to the speaker posts on the amps. His explanation for what was happening was that the subs are 4ohm and the 20.7's are 4ohm so that's driving the load down to 2ohms and that's causing the clipping and the amps cannot detect 2ohms so that's why the led's are not functioning. If this is true then Rel subs cannot be used with any 4ohm speaker or the same problem will occur. I'll be honest, when you start talking ohms splitting and other electronic stuff I tend to get lost. Anybody care to take a stab at this?

mrschret
elizabeth
6,726 posts
 
The problem is HOW you are connecting the subs. And not that they and the speakers are both 4 ohms.
What was explained to you is correct. YOu are conencting 4 ohm subs AND 4 ohm speakers to the same source... Thus making it basically a 2 ohm load. Which not many amps can drive. And I agree it is very unusual for anyone to drive a selfpowered sub from the amplifier outputs (at least for any audiophile.. maybe some kid would do it, thus the persons suprise at it being done at all in a quality system...)
What you must do is find another way to split the signal prior to the amplifier. So you have a signal to the amps and Maggies, And another signal to the subs.(which is NOT from the nmplifier.
If you use a preamp, then a 'y' splitter might work at the preamp output.
Or get a preamp with two outputs..
almarg's avatar
almarg
8,673 posts
 
Elizabeth, you probably posted before seeing my post just above. I always have great respect for your inputs, but in this case you are not correct. REL subs (and many others) often provide high level inputs that are designed to be driven from power amplifier outputs. And that is commonly done in high quality systems. As I indicated above, in those situations the main power amplifier will see the (very high) input impedance of the sub's amplifier, not the low impedance of the sub's driver.

I'm quite certain that the explanation of the problem that I provided is correct.

Best regards,
-- Al
mrschret OP
52 posts
 
Al, your explanation is great. I did see just what you showed from the Emo manual. I also saw in the REL manual that there is a different way to connect them to amps like these but the connection shown in the manual was for a two channel amp, not monoblocks so I wasn't sure if it would work on them. As soon as I can get the chance I will make the change. Even with my limited knowledge I was pretty sure what the Emo tech was telling me was wrong. Thank you for your help.
czarivey
4,494 posts
 
Now you know about Emo technical staff so you can rather ask non-Emo tech staff to take care of your equipment :)
bifwynne
2,069 posts
 
Al and Mrschret ... I also use a self-powered subwoofer which is connected to my linestage via a 330K ohm impedance buffer. As just stated, the sub is connected to my linestage ... not the amp.

Why can't Mreschret connect her REL sub to his/her pre/linestage?? Why mess with the amps.
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