How to add a sub to a 2-channel integrated?

[hawkfan]

I'm having some difficulty with this one. I want to add an active sub to my 2-channel system. The problem is that the integrated amp has no preamp outputs, just a tape out and MD out. I read that I could use either of these but that I would not have any control over the sub's volume. I also read that I could use the Hi-level inputs on the sub's plate amp with actual speaker level outputs as the signal source. That way I would have control of the sub's volume. My integrated amp does have a 2nd set of speaker outputs for 2 zone use. If I go with the Hi-level method, could I use the 2nd zone speaker outputs? Would this effect my mains in any way? I want to add a sub, but not at the expense of my current 2 channel performance. Any suggestions?

[OttoMatic]

Hi there,

If your integrated amp's second zone output is simply playing the same thing as the "main zone", you should be fine to use those to connect to the sub. The sub will have a very high input impedance, and will probably use a voltage divider circuit. This means that there will be very little actual current draw from your integrated amp, and you will not lose any measurable amount of power.

Similarly, you could connect from your mains directly to the sub using a parallel connection.

I suspect you will hear no degradation of your 2-channel setup, and also that you will hear no difference between connecting your sub to zone 2 or directly to the mains using a parallel connection (i.e., the sub and the mains being on zone 1).

Good luck.

[Ovation]

Would it not be better to simply wire the speakers to the sub, and then the sub to the amp, thus allowing the all-important crossover to come into play? I may be misunderstanding what you are describing, but it seems to me that your suggestion would result in "double bass" in the area where the sub and speaker bass response overlap--never a good thing, IMO.

[OttoMatic]

Right, you'll need a crossover in there somewhere. I allow my mains to run full range for 2-channel listening, and integrate my sub in with a low-pass filter.

Depending on your mains' capability, you may want to high-pass filter them, and it may be that your sub has some ability to do that.

If your plate amp has a variable crossover point, you can just use that to integrate the sub with the mains. A variable phase control will also help, if you have it.

I would still wire the sub in parallel with the mains.

[hawkfan]

I posted a similar thread on another forum and I think I get this whole sub thing. I should run the speaker leads from my integrated amp to the sub amp's speaker-level inputs. I then run the sub amp's speaker-level outputs to the left and right mains. The only concern I have now is about the sub amp's crossover. How exactly does it work? I mean, I know how a crossover works, but I'm curious about the "specifics" of the sub amp crossover. Is it a two-way design where it takes the full-range signal from my integrated amp and sends the low frequencies to the sub and the higher frequencies to my mains through the speaker-level outputs? That seems to be the idea I'm getting from the responses I've read so far.

[OttoMatic]

Is there a crossover frequency control on the sub? What sub is it?

[hawkfan]

Is there a crossover frequency control on the sub? What sub is it?

The sub I'm looking at is the Rythmik DS12 or 15. They both use the same amp. Yes, there is a frequency or crossover control. It's continuously variable if I remember correctly. I just contacted Rythmik and they didn't recommend using the high pass on the speaker level outputs due to the fact that it is a crude RC filter that is sensitive to speaker impedance. That pretty much kills the only available way to add a sub to my current equipment. If that's the case I may just leave this whole sub thing alone and stick to two channel only.

[OttoMatic]

Nah, I'd still hook it up in parallel. Figure out where your mains roll off as stated in their specs. Apply the sub's crossover to the same point. With some tweaking and adjument of levels, you should be able to integrate the two very effectively. I use my Vandersteen 3A Signature's natural rolloff at about 30 Hz, then integrate my IB sub using an LPF that I create w/ my Behringer BFD (basically, a 4th order LPF at about that same frequency). It adds boost to the low end that I don't get from the Vandersteens, and it sounds great.

Have you ever used RoomEQWizard? It allows you to measure the frequency response of your system, such that you can appropriately integrate mains and sub. All you need is a PC and an SPL meter. You can find out more here.

I would say keep going for it.

[hawkfan]

My mains are the Natalie P design which, of course, I got from this forum. I believe they extend to about 30hz. Right now I'm pondering two directions:

1. I can use the A&B outputs on my amp and just add a high pass filter before the mains. I would probably have to pick a high pass point and build the filter(s) accordingly. It would be even nicer if I could build a variable filter

2. Just run everything through the sub and see how it turns out. I'm pretty sure that the high pass on the sub amp is fixed but I'm not sure where(100hz?).

#2 is certainly the easiest way to go. If any have tried this method with good results, please let me know.

[OttoMatic]

Why not just use the variable LPF on the sub to integrate it with the mains' natural rolloff?

[hawkfan]

Why not just use the variable LPF on the sub to integrate it with the mains' natural rolloff?

That sounds like a good idea. A lot simpler than adding additional hpf's for the mains. I'm planning on ordering the box from PE before the 13th to take advantage of the free shipping. I have a small living room, so I think I'm going with a single DS12. I heard that they have pretty good output down to the teens. Thanks for the help. I've mostly been involved with car audio the past few years and am a little lost when it comes to home A/V. ops:

[OttoMatic]

Yeah, it should work fine, and I think it's a very common method for 2-ch listening to just integrate a sub at the mains' natural rolloff. Just connect that sub in parallel on your "B" channel and dial up the crossover point. Good luck.

[hawkfan]

Yeah, it should work fine, and I think it's a very common method for 2-ch listening to just integrate a sub at the mains' natural rolloff. Just connect that sub in parallel on your "B" channel and dial up the crossover point. Good luck.

Rythmik kit completed this past Friday. Put it together and wired it up. It was a little "quiet" at first but started to get louder(and lower) after about an hour. Blends in perfectly with the Nat P's. Thanks Otto!

[andrewT]

Hi,
if your main amplifier allows you to access the pre to power connection, then go this way:
Intercept the pre to power and insert a high pass filter. Set the frequency to at least an octave above the existing main speaker rolloff frequency.
Insert a low pass filter into the signal feeding the bass amplifier. Set the same frequency as the high pass.
If the filter frequency is above 100Hz then you may need to sit the sub-bass between the main speakers.
If you can't split the pre from the power then you should consider dumping your existing amp or accepting poorer performance from your sub-bass /main set-up.