Hooking up a sub to RC-1070 and RB-1080

[Parsonsk]

With the Rotel RB-1080 and the RC-1070, can you hook up a sub? I see on the back of the rc-1070 there are left and right outputs, is this for the sub?

[BlazeMaster]

what kind of input connections does your sub have? I'd assume that you would wanna use the LFE connection for movies, even if the amp option you mentioned would work.
My PV1 has a RJ something connection that allows the amp to give direct signal to the sub, but I still prefer the LFE for movies. For music, the bass seems a lil faster with that RJ connector.

[NMG]

I have that exact combo Parsonsk and that is indeed what I do. The RC-1070 has 2 sets of preouts and I run one set to the RB-1080 and the other to the L/R inputs on my sub. If your sub has such inputs it should work fine.

[Kevin D]

Since the 1070 doesn't have any crossover options, it would be better to run the RCA's in to the sub and then out to the 1080. That is if your sub has ins and outs and a built in crossover.

Kevin D.

[thyname]

Since the 1070 doesn't have any crossover options, it would be better to run the RCA's in to the sub and then out to the 1080. That is if your sub has ins and outs and a built in crossover.

Kevin D.

Coud you please explain a little on above Kevin?!

You think that this way the sub could sound better? I have same combo (1080/1070) and am thinking to add a sub sooner or later. Your method requires an extra pair of some expensive ICs as well. I don't seem to understand the issue of crossover with subs (and with speakers in general). Probably because I don't have a multi-channel system yet (not considering my Sony HTIB), only a nice stereo one.

[Kevin D]

Sure,

The 1070 always sends a full output signal out both sets of preouts. If you run one to the 1080, the speakers hooked up to the 1080 will play a full range signal as best they can. IE, full is 20hz-20khz but your speakers may only be capable of 40hz-20khz. It's not a brick wall, so everything below 40hz will just gradually get softer to the point you can't hear it anymore.

A sub added to the second set of outputs will also get a full range signal. Pretty much most subs have a built in low-pass crossover that's adjustable. Now you would probably be ok if you set it's crossover to match where your speakers naturally trail off (40hz in this example). Anything lower than this and you have a dip in the bass and anything higher you have a spike in the bass. IE, set the sub to 60hz and both the sub and your speakers will be playing 40hz-60hz at normal levels, creating a bass doubling effect.

So if your sub has a built in high-pass and low pass crossover, the control will effect what the sub plays and what gets sent out the outputs on the subwoofer (which gets sent back to the 1080 amp). That way, you can set it to 60hz and the sub plays 60hz and below while your mains play 60hz and above.

If you are happy with your two channel setup and want a little more low-end where your speakers can't play, hooking the sub up to the second output and leaving the 1080 connection alone will probably yeild great results. If you want to let your sub handle more of the bass and free up some of the 1080's power to more efficiently drive everything else, you will need to run through the sub to avoid a boomy sound.

Some subs also have high-level passthroughs where you run the 1080's output to the sub and then run speaker wires from the sub to your speakers. It's not as clean of a signal going to the sub and it's debatable what effect this siphoning of the signal would have on the 1080's sound.

Confused yet?

Kevin D.

[maddog]

You could also buy a separate crossover like the Outlaw Audio ICBM. It would take 2-ch input and output 2.1 ch. You would not need long interconnects for that option like you would with using the sub's crossover, which could introduce noise into the system if they are not balanced IC's.

[bigburner]

Parsonsk, I have an RB-1080 amp, an RC-1070 preamp, a B&W ASW750 subwoofer, and a pair of B&W CDM9NT speakers (3-way floorstanders).

I've wired the sub so that the output of the pre-amp goes to the input of the sub (via RCA cables), and the output of the sub goes to the input of my amp (also via RCA cables). This enables the high-pass filter on the sub to limit the frequencies being sent to my speakers to 80Hz and above. I've set the low-pass filter on the sub to 80Hz so that the sub only plays 80Hz and below. I've found that this results in the best stereo image because the sub isn't duplicating frequencies being played on the speakers. This method of connecting your sub takes the bass load off the speakers, enabling them to play at much higher volume without fear of distortion. This is important for me because occasionally I do play music at high volume.

[thyname]

Thank you Kevin for the detailed explanation! It seems that I would need to try for myself both low-level and high-level passthroughs of my future sub. It seems that the low-level one is the easiest way of doing it, but I am not sure if it is the best. I am thinking of purchasing a HSU VTF3-MKII, which has them both. I will definitely will give them a call first to see what they have to say about both options. But, before I buy anything, I need my fiance's approval!!! Such a sub would be a good upgrade for my stereo, since I can use it for my future HT as well.

As for the Outlaw ICMB, I have heard they are mainly for SACD, dvd-A playback, am I wrong?

[maddog]

... As for the Outlaw ICMB, I have heard they are mainly for SACD, dvd-A playback, am I wrong?

You can use it between the preamp and amp for a 2-ch stereo setup. If you are interested, you can download the User Manual from their website. They describe how to set it up for a stereo setup in there. They are also very quick about replying to questions by e-mail.

But I have not used an ICBM and I have not used the setup where you use a sub's crossover. So, I don't know which sounds better or which is cheaper. But, I have heard that the crossover in the ICBM is supposed to be very high quality. Although, I do think you have to plug the ICBM in. So, you'll need an outlet for it. On the other hand, some say that long runs of unbalanced IC's can introduce noise in the system, which is what you would need to use the sub's crossover. Long runs of IC's can also be expensive. So you would not need that for the ICBM, since it would be on your audio rack, maybe above your preamp.

[thyname]

Do you mean for a 2 channel setup WITHOUT a sub? I don't have a sub yet, and I am not getting before building my HT. I am sure that I will consider this ICBM, since seems to improve a lot of things.

[NMG]

Kevin D's explanation was very good indeed!

For what it is worth, I have found that my system sounds best without using the high pass feature of my sub, hence the reason I run the second set of preouts straight to the sub. I have Paradigm Studio 80's and a Paradigm PW-2200. If I had smaller main speakers, I would use the high pass feature. Given that my mains go fairly low already, I just set the crossover on my sub quite low . . . I think it is set at around 50-60hz or thereabouts . . . I'd have to double check to be sure though.

From my own paranoid standpoint, I wanted to make sure that my speakers were receiving the "cleanest" signal from my 1070 as possible and I didn't want the crossover network on my sub "tainting" it in any way. I also found that using the high pass tended to make things sound a little brighter, but it could just be my imagination. It certainly didn't sound bad, but it did sound different from how I am running things now. With my sub crossover set that low, I don't really notice any bass humps or stuff like that. I can also play my system plenty loud without distortion. If I were running a small amp the high pass would be useful in these regards. As it stands right now, my speakers would run out of steam and/or make my ears bleed before the 1080 will start to show fatigue

One thing you will find with subs is that it takes ALLOT of time and experimentation to get things "right" for your room and listening preferences. Try both methods of hookup, play around with the sub level and crossover settings, experiment with placing the sub in different areas of the room, etc. It is a bit of a pain in the butt but when you get it right it will be worth it :T

[maddog]

Do you mean for a 2 channel setup WITHOUT a sub? I don't have a sub yet, and I am not getting before building my HT. I am sure that I will consider this ICBM, since seems to improve a lot of things.

I thought you wanted to hook up a sub? Either way, I think the ICBM has a bypass feature that sends no signal to the sub and a full-range signal to the mains if you want to listen to something without the sub. With the turn of a knob, you can turn off the bypass and use the sub when you want.

I think the ICBM also allows you to play a full range from the 2 mains and just send a low pass signal to the sub so that you can have double bass below the crossover, like I think NMG is describing. I have read that a lot of people like that better.

... From my own paranoid standpoint, I wanted to make sure that my speakers were receiving the "cleanest" signal from my 1070 as possible and I didn't want the crossover network on my sub "tainting" it in any way. I also found that using the high pass tended to make things sound a little brighter, but it could just be my imagination. It certainly didn't sound bad, but it did sound different from how I am running things now...

Outlaw does claim that the crossover in the ICBM is "audiophile" quality. So, it is probably better than the crossover in most < $1000 subs, but obviously that depends on the sub. My point is that a cheap crossover in a sub might brighten the high-passed signal sent to the mains, but the ICBM might not since it's supposed to be high quality. But this is just speculation on my part. I have never read anything about this issue and I don't know this from my own experience since I don't have an ICBM (yet). But, I am concidering getting one for my SACD player.