Sub connections:RCA vs Speaker cable?

The description says that the atc sub accepts high level input, meaning it accepts speaker wire unless it takes XLR or something. That still doesn't directly relate to your question about splitting the frequencies between the sub and the monitors. The anwer I got from asking around is mixed. Some say that the monitors perform better because it's not trying to reproduce the signal it can't do anyway, others say that the cabinet's damping limits the ability of the monitor to reproduce the signal in the first place, which is an integral part of the monitor's design, AND, why the heck would you want to introduce another (most likely) very inferior crossover into your speaker system?

Btw, considering that the driver is a 9", I would guess that hsu's sub would outperform it in both volume and depth. If it were me, personally, I would go for one of rythmikaudio.com's servo subs. I think it would run about $600+shipping for a 12" servo driven subwoofer with a fully variable phase adjustment and the cabinet. Not many subwoofer amps have the variable phase adjustment, which can really alleviate placement issues. I'm guessing that the atc sub might be servo driven too since it's only a 9", but with the rythmikaudio servo, you'd be getting a larger and well built driver for less money. Plus the variable phase! All you need to do is assemble it, which isn't hard since they made the cabinet for you. Even I did it! Just gotta have a soldering iron hot enough and a screw driver and screws. I'd probably use some fiberglass stuffing too.

I have their regular plate amp driving my diy dual 10" subs and am very happy with the amp.

Next up? Room treatment!

I would imagine that an RCA connected sub would be better. You do have an output for that on your amp?
Crossovers etc have always been a bit beyond me.

Go for the rca connection(s).

Speaker level inputs are for when you are hooking up a subwoofer to a system with speaker outputs only and no subwoofer output.

As for the crossover, "dial it in" close to where your main speakers lowest frequency rolls off. If you don't have access to really expensive sound meters (not the cheap Radio Shack kind), then you will have to play it by ear. I like to have my crossover set as low as possible, as a boomy sub trying to output higher frequencies is a waste.

In other words, a good place to start is to look up the frequency response specs of your speakers. e.g. Speaker frequency response is 50Hz to 20KHz. Set your subwoofer's crossover to 50Hz plus or minus a few till you like how it sounds.

Of course, the placement of the subwoofer and room shape/treatment, greatly affect your sub's performance.

Hope that helps.

-Ed

OK I will give you advice for using sub in audio only system (not home theater where you use sub out or LFE connection)

There are usually two connection options:

1)Connect speaker cables to sub, then connect sub to speakers with another pair of cables. Not best way IMO because you need extra pair of speaker cables that connect through cheap connectors on sub.

2)Use RCA cables from any low level volume controlled output from preamp (if no extra ones available use RCA splitter) to connect sub, do not need expensive cables here, sub must have low level RCA inputs. This is the method I always use for my systems.

Once connected using one of these methods you use variable crossover on sub to blend with lowest bass of main speakers, usually the listed -3db bass response level for speaker is very close to optimum for setting crossover on sub. For my Von Schweikert VR1, Tyler Taylo Ref and Green Mountain Audio Europas crossover sounds best at 40-45 hz to my ears. Then you can adjust overall volume of sub to match different types of music.

I really like HSU subs (own two currently) you should seriously consider VTF2 Mk II model for $499, it is a giant killer.

The folks at Mapleshade Records believe, contrary to common expectation, that subs sound/integrate better when using speaker cable rather then RCAs. One is not necessarily cheaper then the other, and I suggest you try both ways if you've got the free time.

I owned the hsu stf-2 which is the vtf-2 at max output mode instead of being variably tunable. Basically, I now know that I sold it because I couldn't get the phase to line up well with my speakers. Back then, I just thought it was muddy. I don't have a lot of placement options. Maybe you do. With a variable phase adjustment, the problem is minimized. If you can get it placed well in phase, then I would hesitantly recommend it. I did experience some bass overhang though and I'm not 100% sure that it was phase related. The sealed low Q design of the rythmikaudio servo sub will smoke the tightness and quick response of the hsu subwoofer on paper any day of the week in terms of phase slope and group delay. I have no reason to believe it wouldn't do so in person.

I would also recommend low level RCA connection to the subwoofer, btw. High power connection is a generally a last resort for people without a second preamp output from the days before subwoofers.

As I understand it, the STF-2 is comparable to the VTF-2 in max extension mode while the current production of STF-3 is comparable to the VTF-3 in max output mode.

Three things you need to look for when buying sub for audio only system:

1)RCA low level inputs on sub

2)Ability to adust volume and crossover point of sub

3)Make sure sub variable crossover goes low enough, most subs only offer 50-150hz adjustment! You want crossover adjustment down to 30hz (some go even lower like Rel down to 26hz)