Hooking up sub

Hi, I'd like to hook up a powered sub (Energy ES8) to an older Technics HT receiver. There is no sub output on reciever. I was told not to use the "B" speaker hookup as this could screw up impedence. I was thinking, could I hook up to tape RCA outputs Get an adaptor that merges the L+R into one RCA cable since normal sub output is mono anyway? If not what would be the best way to do this? The sub is powered and has a volume control and a crossover selector knob. By the way will be using 6 speakers, the front and rear L+R, center and the sub, all Energy speakers.

1. Tape out is not volume-controlled, so the sub level will not track the main speaker level if you do this.

2. If you do not have preamp outputs, you must use the speaker output.


What model is the receiver? If it is an HT receiver which supports mains, surround and center speakers, I'd be surprised that it doesn't have some type of sub output. Are you sure there is not an RCA out for "LFE" (low frequency effects), which is sometimes what the sub out is called on an HT receiver.

Does your receiver support Dolby Digital 5.1 surround sound? If so, it must have a sub out of some kind.

There is another way to hookup sub from front/left channels if your sub backside has speakers hookup and you might have to buy extra speakers cale. Connect speaker cable (SC) from LF front speaker from receiver to input subwoofer speaker connectors. And output of subwoofer Speaker connectors to your front LR speakers.
Old receiver, Technics SA-GX670. For the bedroom. No sub output I can see (or LFE) but perhaps the idea about using the high output speaker connections on the sub (it does have them)? I was worried about impedence again, hooking up 4 ohm speakers to my Sony HT (old) pretty much toasted it, now even with 8 ohm speaks hooked up the "protection" circuit activates a lot. Or maybe the tape out and just adjust the volume on the sub with it's own output dial?

If you run speaker wire from the receiver to the sub, then run speaker wire from the sub to the front L&R speakers, it won't upset the impedence seen by the receiver. If it is a surround receiver and you will be connecting a center channel and surrounds, you will need to determine how bass management will be performed.

If your receiver allows speaker configuration, you will likely need to set up the front L&R main speakers to "large" because the sub/speaker setup will be receiving the low frequency informatio too. The other speakers will need to be set to small so their low frequency information goes to the sub/front speakers.

If your sub is powered (and it is, right?), then hooking up the the sub via the B speaker hook-up should not affect impedance, the receiver is not "driving" the sub (the sub amp is), the receiver is only sending a high level signal to the sub amp. This is also by many (like the REL sub manufacturer) considered a superior signal transfer.
The person who told you not to do this was probably assuming that the sub was NOT powered by its own amp. Hope this helps,
Hey thanks for answers folks :) Lot of knowledgable people here. My knowledge is kind of stuck in the 70s when I was "into" what I considered "high end" equipment, as least the best I could afford, usually something from the "Absolute Sound" (no, could not afford Audio Research tube stuff :)). No problem hooking up 4 ohm speaks in those days, in fact usually got quite a bit more power into 4 ohms.