# Using a second receiver to power a sub?



## azgreenb (Nov 19, 2007)

Basic question, I purchased a new receiver and want to know how to possibly use the old receiver to power a sub? How do the signals from the main reciever get connected to the "sub" receiver. I am still looking at buying/building a sub. But I have read other posts where people have used the power from a second reciever to power their sub.

new receiver: HK AVR-645
old receiver: Sony, forget the model #, but I remember 90W/ch


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## brent_s (Feb 26, 2007)

I'm assuming the sub doesn't already have an amp and only has speaker level inputs.

Connect the LFE/Sub output on the H/K to an analog input on the Sony. If the Sony has 5.1 line level inputs, I'd use one of those as they'll likely have the least signal processing from input to output. Then just connect the sub's inputs to the appropriate (left or right front) speaker output on the Sony. If your sub is a dual voice coil, then split the H/K (assuming only one RCA output) signal using a Y-splitter into both left/right inputs on the Sony and connect both speaker outputs accordingly.

Clear as mud?

-Brent


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## tonyvdb (Sep 5, 2007)

Brent is right, The only issue is that the 90watts is hardly going to be enough power to drive a sub at any decent level. The Sony will not be bridgeable meaning bubbling the amount of watts that it will put out to the sub.


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## azgreenb (Nov 19, 2007)

So if I take:
H/K sub output and run it into the Sony CD (RCA) input.
Connect the (as yet to be purchased/built) sub to one of the speaker mains
Set the Sony to CD and enjoy!

That shouldn't be too hard, Thanks!


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## Mike P. (Apr 6, 2007)

Make sure your Sony can handle the load from the sub. If your sub is 4 ohms, the Sony needs to be 4 ohm stable. The specs will tell you.


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## brent_s (Feb 26, 2007)

Not trying to be argumentative, but power needs will depend on Bill's listening habits, the driver/alignment chosen, and the room itself. While it's fun to say you have 1Kwatt on tap or more, the reality is most folks will be satisfied with much less 

For example, I have a pair of sealed NHT1259 based DIY subs in my living room system. Power plant is an ancient Yamaha RX-V850 receiver rated at 80 wpc into 8 ohms. Calibrated flat with the mains, the subs have no problem keeping up at a measured 105dB peaks 17' from the mains/subs and the room is 20x22x9 and open to pretty much the rest of the downstairs and part of the upstairs of a 2900 ft^2 low country. Of course, the NHT1259s only need 300 watts to reach Xmax above 40hz and less than 150 watts by the time you get down into the mid 20s....output=f(displacement). My movie listening tastes tend to run towards 90-95dB peaks on average, especially when the family is involved. By the time you get to an 85dB average (not peak) level on music, conversation becomes difficult.

-Brent


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## tonyvdb (Sep 5, 2007)

brent_s said:


> Not trying to be argumentative, but power needs will depend on Bill's listening habits....
> -Brent


True. But Sony is notorious for over rating there amplifiers capabilities so it would not surprise me if the rating is lower than what it states. Yamaha's are much closer to actual power available.


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## lcaillo (May 2, 2006)

I don't know where you get the idea that Sony is notorious for over-stating the power of their amps. This is simply not true. They may often be less capable into lower impedance loads, but the specs are what they are and I have never serviced a Sony amp that did not meet power spec.

I also use a Yamaha receiver at 100w/ch to power my subs and have more than enough power for moderate listening.


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## azgreenb (Nov 19, 2007)

I think if I had a nice 500W SVS sub I could put it to use. However, I like the idea of re-using something that I already have. Plus after seeing some of the DIY subs, that idea is kinda growing on me. I will double check the Sony's specs. Thanks again.


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