Using Line level input - does it make a difference?

ChadNott

When connecting speakers with a "line level input" for the powered sub (i.e. RT1000i), will this type of connection provide a better response from the sub?

schumach

I have the RT1000p and use the line level inputs. I did notice a better bass response when I used the line level inputs.

Greg

pdebaum

It could, but most likely not. This is why :
RT1000i's subs are part of a full range speaker design and thus the internal crossover network is optimized for accepting a full range signal (all audio frequencies, bass included) from the speaker-level inputs.
The tower speaker comes with 2 sets of binding posts, one upper and one lower. The upper one controls the upper and mid-range speakers, while the lower one controls the woofer of the sub. They are usually shorted together with pieces of metal so the full-range signal can reach both sets of speakers at once. This is the original intended design, not counting hassle-free, and you may likely find that's the best way for your sub to "blend-in".
When hooking up the sub's line-level input, you have to bypass this speaker-level input. To accomplish this, you make sure your speaker cables are connected to the top binding post and you remove the shorting metal straps on the binding posts so the speaker-level signal can't reach the woofer from the lower posts. Thus the woofer will only receive signal from the sub's line-level input.
And now it's tweaking time. This means setting the bass management on your receiver or amp (yet another complex subject) and tweaking the crossover of the sub so it blends well with the filtered or unfiltered bass coming from the receiver/amp. Unfortunately, subs from full range towers such as the RT1000i were not designed to being real standalone subwoofers and therefore lack some adjustements on the crossover point. Also, there will be issues with the sub's amp AUTO ON/OFF feature, which is highly sensitive to the signal strenght at the line level input. This means that at reasonable low listening levels, the subs in your RT1000i's will not turn on and you won't have bass! To counter that, you'll have to boost your sub signal from your receiver, e.i. more tweaking and more possibilities of disappointments.

To conclude, for getting the most from your RT1000i's sub :

1) You'll most likely find the speaker-level connection to sound best. Hassle-free and operated with the intended speaker manufacturer specification.

2) If you feel adventurous and want to experiment, you can try to achieve something better by filtering the bass signal and using the sub's line-level input. Know well then your bass management rules and maybe you could achieve something better despite the limited capabilities of tower speaker's subs.

In short, experiment and see what sounds best to you. I went through that very same process trying to best use my RT2000i subs, and after many experimentations, found out that the speaker-level inputs for the sub sounds finally best to me, confirming Polk's recommendations. I should have trusted the guys I think they should have just eliminated that line-level input and prevent the confusion, but I guess it's good to have more options, even if they are not necessarily best

presidan

You can really give great responses !!!
What receiver are you using ?

pdebaum

Thanks presidan! As I just "came of age" on that very subject of bass management in receivers and speakers, after many many hours pondering articles on the web, I felt it my duty to post my fresh findings, as this is the kind of information I couldn't find easily and I thought others might welcome the gathered information. I was a complete clueless newbie not 3 weeks ago about any Hi-Fi subject.
Receiver documentations are usually a joke I hear (my Marantz one no exception) and Polk speaker manuals are marginally better, though at least they give you some basic hook-up recommendations.
As for my receiver, it's a Marantz SR6200. Not a bad receiver for the money, provided you escape the unusual high level of lemons that have circulated in the SR-x200 line since their introduction. Couldn't also resist the Philips employee discount or I might have selected something with more power

tclarence

I recently purchased RT1000i's, f/x300i's and a CS245i for my system, and have also struggled trying to find the best bass management of the built in subs. This thread was VERY helpful....probably because it confirmed my final decision: to go with the speaker wire and forget the line-level! I specifically wanted the 1000's because I listen to music as much as I watch movies and didn't want to mess with a dedicated sub. Will the bass from thunderous explosions on a DD or DTS movie rattle my windows? NO, but you can still feel it your toes! And more importantly, the bass from AC/DC and Metallica WILL rattle my windows! That's the strength of the 1000's: good movie rendition and GREAT music output.