Subwoofer connectivity question

I've got a lightspeed attenuator, a prima luna prologue 5 and a Parasound Z Dac.

What is the best way for me to hook up a sub? I was thinking if I could find a sub with RCA inputs and outputs, I could put the sub in line between the lightspeed and my amp. If the sub filters the signal so that its sending a high pass signal via RCA's, if I put in line before the amp, it would only be amplifying 80-100 hz and higher thus relieving some of the load of my amp in the process.

Anyways, what are your ideas on the best way to hook up a sub to this particular set-up (DAC, Lightspeed, Amp...)?

Thanks for your time and input!
Ok, I am trying to think.I am not familiar with the lightspeed unit but it's probably a passive preamp. What is your source? Your source is connected with RCA so you buy and use a Y RCA connector to split the signal,assuming you buy a powered sub . Signal would be going to the sub AND your setup at the same time.Powered subs have besides other controls also a volume control build in .Another option would be to use the speaker connections of your Primaluna ,some subs come with speaker connections but I prefer the Y RCA splitter myself.

The input impedance of the line-level inputs of most subs is too low to be optimal when driven by a passive preamp such as the Lightspeed. Also, if the sub is not located close to the Lightspeed the capacitance of the interconnect cables that would be involved stands a good chance of being too high to be properly driven by the Lightspeed.

Splitting the output signal of the DAC, as was suggested, is probably a non-starter because you would have to adjust the volume controls of both the Lightspeed and the sub in sync, every time you want to change volume.

My suggestion is that you choose a sub having speaker level inputs, and use those.

-- Al
If you use a Y connector you will be running your speakers full range. I have always used a sub going out from preamp to line in on sub then line out on sub to line in on amp. When you do it that way your speakers are not running full range which is what you want to do!
Thanks for chiming in here. I was concerned about the same thing you spoke about in your reply.

Sooooo, speaker level inputs is the way to go in my particular case, which way should I hook them up? Should I run leads from my amp to the sub, at the same time as running speaker cables from my amp to my speakers, OR should I just use the speaker level outputs on the sub and hook my speakers up that way?

If I do use speaker level outputs on the sub, is the sub degrading the signal my speakers see, since it will be in line of the signal between my amp and speakers?
Should I run leads from my amp to the sub, at the same time as running speaker cables from my amp to my speakers?
Yes. The input impedance of the speaker-level inputs of the sub will be very high. Therefore it will present a negligible load to the amp, and the wiring between the amp's output terminals and the sub doesn't have to be heavy gauge speaker wire; much narrower gauges will work fine for the sub connection too, as long as the main speakers are connected directly to the amp with heavy gauge cable.

REL subs, for example, come with a narrow gauge 3-wire cable which can be used for that purpose, one wire going to the left channel + output of the amp, one wire going to the right channel + output of the amp, and one wire going to the - output of either channel. (Connecting to the - output of the other channel isn't necessary, as the two - outputs of an amp that does not have balanced outputs are presumably connected together within the amp).

-- Al
If you are going to run your speakers full range why bother with a sub?
I use a pair of Gallo TR1D subs, and run my bi-wired main speakers full range. The subs are connected speaker level with a short piece of speaker cable from the low frequency terminals of the speakers to the subwoofer inputs.

The subs are positioned next to the main speakers so this arrangement is tidy. The crossover and level controls are utilized on the subwoofer for a perfect blend.
The REL "high level" input system is brilliant as it stays out of the way of existing hookups, the amp likely doesn't know it's there (puts a very high impedance load on the amp) and lets your mains remain unmolested...I spade my REL at the amp and banana the main speakers so everything fits neatly, and the REL blends beautifully and sounds great.
Hi B Limo, your dac is fine with a low output impedance your Prima Luna is fine with a nice high input impedance.
To see if the sub will match ok I need to know what it is and if you have a link to the specs.

Cheers George