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Discussion Starter #1
For various reasons, I am hooking up my sub through the speaker level inputs through the mains, running my mains as large, all other speakers small, and running the sub as "no".

My question and concern is about the amplifier. In this hookup does the powered sub share in the load of the power with the receiver as it would in the normal line level input method, or is the receiver being overworked causing possible distortion?


Thanks

Greg
 

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Your amp powering the sub will still be doing so, not the receiver. your receiver will be working just as hard as if you had no sub, and were running everything full range.
 

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I'm curious. Can you elaborate why you have set up this way. I was considering it but have been advised to just use the sub out.
 

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Discussion Starter #4
Mattsushiba,


My main speakers have a frequency range that goes down to 80 Hz. Knowing that I needed to set the crossover higher than that I tried both 100Hz and 120Hz on my receiver with the crossover on the sub all the way up to get it out of the way. When I ran bass management frequency sweeps with DVE and a SPL meter, I noticed that with a 100Hz crossover I was getting a big hole between 90-120 (it even went silent for a split second). Even at a 120Hz crossover on my receiver, I was getting a big dropoff between 100Hz and 120Hz. This didn't seem right, I figured maybe it was the crossovers of the sub and receiver not meshing right, or maybe it was phase cancellation issues.

I figured what the heck, and tried speaker level inputs. I hooked up my sub to the mains, put put the sub to "no", and set the crossover to 100 Hz on the low pass of the sub.What happened was amazing. Male vocals were suddenly much fuller, and everything sounded a ton better than before. I ran the sweeps again and there was a relatively flat response throughout the crossover region.

I am not sure why this improvement happened, especially when everyone recommends line level inputs, but unless I am lacking somewhere else by this setup, it makes sense, to my ears at least, to use the speaker level inputs.


Craig,

After I posted this I called Cambridge Soundworks, and they indicated that even though a full signal is flowing through the mains, the power from the amp of the receiver is only being used to power what the front satellites are using (100 Hz and up). The signal that the sub is taking (100Hz and down) is not being powered by the receiver at all and not sucking up power. The powered sub would handle that. I know not to always believe what manufacturers say, so I put it back to you. Does this make sense, or do you still think that the receiver is working extra hard with this setup vs. a linelevel setup.


Greg
 

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I believe there's an article at http://www.polkaudio.com that discusses this method of hookup, and they seemed to espouse it.


It may have been more for music, which may solve the bass management issues when running SACD players, for instance, into your multichannel setup.


It looks like their website is undergoing a major change at the moment, and is unavailable, so hopefully the article is available in the new site incarnation under resources, education, etc.
 

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Greg, any frequencies filtered from the main channels by the sub's crossover are no longer loading the receiver; they instead go to the sub's amp's input, with very little load current, so the receiver indeed sees less load.
 

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Discussion Starter #7
Thanks Larry,


Obviously I should go with what sounds better, but do you see any negative in using speaker level inputs other than it being a pain to setup and extra wires.


Greg
 
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