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How to connect subwoofers

Hello guys
I have a 2.0 stereo system, entry level high end, with Audio-gd R8 DAC, Audio-gd M1 preamp, Nord Acoustics Class D amp and Q Acoustics Concept 500 floorstanders.

I want to add a pair of subs, but before buying them I need figure out how I will be able to connect them to my system. 

There's seems to be two ways:

1. High level connection. The one I prefer for my room lay out, cables length and sound quality. 

This way I understand I have to connect the subs with speaker cables from the binding posts of the speakers, each sub connected to one speaker. 

I have different opiniones on this kind of connection from different dealers. Someones say the sub wont change the impedance, etc of the speakers and it wont affect the amp, but others say the opposite.

2. RCA connection. 

I only have one RCA output for each channel on the preamp, but I have two RCA inputs on each sub (right and left channel).

I understand I should use one single RCA cable for each sub, but that will mean that one RCA input on each sub will not be not connected and it will not get any signal. Could that harm the subs? 

Well I would appreciate your comments regarding your experience with subs as I guess most subs should behave similar, no matter the brand. Am I correct? 
plga
mrdecibel
3,063 posts
 
No, it is not. Feed the subs the same way you feed the speakers. Example : Spades / bananas share a post on the amp.
paradisecom
309 posts
 
Using the high-level speaker connectors on the subs is fine. I don't see a problem connecting them to the speaker terminals, rather than the amp, if it's easier for you. The speaker level inputs on most subs are usually many thousands of ohms impedance, so your amp won't see any additional load. 

For the rca level inputs, you could install a simple set of y-cables from the preamp outs with one leg going to a subwoofer and the other the amplifier input. Connecting only 1 to a sub would be fine. 

What subs are they, anyway?
lalitk's avatar
lalitk
5,450 posts
 
Here is another recent discussion about integrating subs. 

https://forum.audiogon.com/discussions/best-way-to-integrate-subwoofers
danoroo
239 posts
 
plga wrote:
" Thank you guys.
One more question.
My power amp has only 4 binding posts, 2 for each speaker channel, so taking a parallel pair of cables from the same binding post of the amp, isn't the same of just taking them from the speakers binding posts?"

If it is more convenient to tap the signal from the speakers binding posts then do so.  It doesn't look the same as tapping the amp's binding posts, but it is electrically identical.  
plga OP
184 posts
 
Paradisecom
The people of SVS and Kef have told me the exact same thing, the high level inputs of their subs have thousands of ohms and would not provide an extra load to the amp.
The thing is that here (Argentina) there's no dealers of SVS and Kef is much more expensive than in US or abroad.
I've found a good deal in a pair of Boston Acoustics M Subs, wich have good specs and some few good reviews, so I will buy them with a trial period, but I cant get a strait answer from Boston Acoustics USA about how to connect them to my system without risk. 
Also my preamp and power amp are connected with XLR cables, so the RCA outputs of my preamp are free and I think, if the M Subs dont accept RCA mono input, I could get a pair of Y RCA cables to connect both RCA inputs of each sub to one RCA output of my preamp. Has anyone tried a connection with these Y RCA cables? 
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