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Topic: Adding a Sub to a stereo set up (Read 2374 times) previous topic - next topic
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Adding a Sub to a stereo set up

This is for a outdoor system that has a Yamaha Amp driving Bose 251 speakers. This is an enclosed patio, and weather proof is not a must for the Sub.

The question I have is if the line out RCA jack pair - Tape Out -  on the amp can be used to supply as Sub. And if so, other than a line in jack what does the Sub need to have built in to accept what will be a full spectrum signal with no volume control.

The other way I guess is a high level connection to the Sub from the speaker terminals on the amp, with a Sub that accepts high level inputs. If such a Sub is available is that a better approach?

Thanks in advance for any inputs.

PS: The amp does not have a subwoofer out jack.

Re: Adding a Sub to a stereo set up

Reply #1 –
Quote from: KumarK on
The other way I guess is a high level connection to the Sub from the speaker terminals on the amp, with a Sub that accepts high level inputs. If such a Sub is available is that a better approach?
Many inexpensive subs have speaker level inputs. that's what you want to use, not a fixed level Tape Out...unless volume is controlled other than receiver (by source for example).
Loudspeaker manufacturer

Re: Adding a Sub to a stereo set up

Reply #2 –
Thanks; the volume from the fixed line level outputs on the amp is indeed controlled by a volume level equipped source - Echo Show 5 wired to its Aux line in jacks.

Is there any SQ difference/benefit in going speaker level in such a case or can one just do what is more conveniently wired? Or, where the Sub does not have speaker level inputs?

PS: I also notice the Subs often have a Left/Right pair of line level input jacks - can one wire a RCA pair to 3.5 mm stereo jack cable to either of the two jacks to avoid buying another cable? Presumably even if a RCA cable with two jacks at both ends is used, the signal must be getting summed inside the Sub?

Re: Adding a Sub to a stereo set up

Reply #3 –
Quote
Is there any SQ difference/benefit in going speaker level in such a case or can one just do what is more conveniently wired? Or, where the Sub does not have speaker level inputs?
Theoretically the line-level inputs could be better because most-likely the speaker level inputs are attenuated to line-level before being re-amplified, and that's an extra amplification stage.   And if you clip the regular speaker outputs you're sending a clipped signal into the sub.

Quote
PS: I also notice the Subs often have a Left/Right pair of line level input jacks - can one wire a RCA pair to 3.5 mm stereo jack cable to either of the two jacks to avoid buying another cable? Presumably even if a RCA cable with two jacks at both ends is used, the signal must be getting summed inside the Sub?
That's confusing.  Either way, if it has left & right inputs they will be summed internally and of course either way you need the correct adapters/cables.   

In a "normal" home theater setup, the bass management built into the receiver sums the bass from the 5 (or 7) surround channels and with the "point one" LFE channel.    The summed "mono" line-level signal then goes to the powered/active subwoofer.

Re: Adding a Sub to a stereo set up

Reply #4 –
Thank you.

I use a stereo amp that has Tape Out sockets - and when I wire those to the usual audio in jack on a portable powered speaker via a cable that has two jacks at the amp end and a stereo minijack at the other end, the speaker plays fine. Hence the question - if I was to wire the same cable to either of the two line level input jacks on a Sub that has such a pair, is that ok?

A related question - my amp has two pairs of line out jacks, one for Tape and the other for Minidisc recording. Can I keep the portable speaker wired to one pair and the Sub to the other pair as above, with no ill effect on the amp?

Re: Adding a Sub to a stereo set up

Reply #5 –
What's the actual amp model?

I also don't understand very well what you want to do with the RCA to 3.5mm cable, do you want to mix the L and R before going into the sub? That won't work and may cause some damage, generally speaking you can split with cables, but not the reverse (mix) without a proper mixer (which the sub already has integrated, if it has L and R RCA inputs).

I think it's practically better in your situation to use the speaker level inputs, for the reasons already mentioned, you'll be able control volume with the amp. If you use line level and change volume at the source, it'd be easy for someone to accidentally change the amp's volume and then your balance between speakers/sub will be out of whack.

In your specific case you need to use both L and R inputs of the sub, you can't just use one. Most subs have the option to only use one, but that's for when your source or receiver have a proper sub output.

Re: Adding a Sub to a stereo set up

Reply #6 –
Quote
A related question - my amp has two pairs of line out jacks, one for Tape and the other for Minidisc recording. Can I keep the portable speaker wired to one pair and the Sub to the other pair as above, with no ill effect on the amp?
They shouldn't affect each other.   
 

Re: Adding a Sub to a stereo set up

Reply #7 –
Quote from: andy o on
What's the actual amp model?

I also don't understand very well what you want to do with the RCA to 3.5mm cable, do you want to mix the L and R before going into the sub?
Yamaha AX 397. I only thought I could use an existing RCA pair to stereo minijack cable, but have since learned I can't so I bought and am now using a stereo RCA cable with two jacks at each end, and the Sub is working fine wired using it. It is a fixed line out feeding the Sub, but the reason it still works for me is that the amp is in a box out of sight for months at a time since both sources have volume controls that are used to do the sound level changes when needed. So it was a matter of resetting the system balance again with the sub in the mix, and then closing the lid on the box that the amp sits in, with the volume knob on it not accessed by anyone else. The source level changes leave the balance between sub/speakers unchanged.

Till the cable arrived I was using speaker level connections from the B speaker terminals on the amp - while I have not seen any sound quality difference, the sub volume knob is at a significantly lower level using line level connections, to get the same subtle bass augmentation as before.

So now I have a speaker pair wired to the amp speaker terminals and a powered speaker and Sub wired to each of the two REC line out jacks on the amp. With stereo imaging much less of a need compared to that of more even sound levels across the space, this has all worked out quite well...

Thanks for all the inputs.

Re: Adding a Sub to a stereo set up

Reply #8 –
One of the sources in question is the cheapest Echo model with a screen, the Echo Show 5, with its audio out wired to a line in pair on the Yamaha. Based on using that I'd say home audio has never had it so good as long as one isn't caught up in the audiophile navel gazing analysis trap. For a very low fixed cost of the Show and a small recurring subscription cost, one can get album art for millions of music tracks from Spotify and the like, with music play commanded by both voice and from the phone app. And the sound quality is still excellent via this or any other legacy style set up from years ago. IMO, to my not golden ears.

Or for that matter, in my case, also from a local NAS that has all my owned music on a USB stick plugged into a Raspberry PI with the My Media for Alexa instance allowing voice commanded music play of songs and playlists of that music, with album art.

Modern tech does get some things right, for very low prices.