Need help with stereo subs and full range drivers

[zanon]

Hi guys:

I was wondering if you could help me out. I have a stereo system (for music) where the speakers are directly connected to the amp -- so no crossover.

I want to supplement the speakers with stereo subs. So, this means I want left and right channel signal to be split, and go directly to a left and right sub. At the same time, I don't want to introduce any crossover between the amp and the speaker, so I do not want to connect the sub and speaker in series (ie. amp -> sub -> speaker is not acceptable).

Speakers are passive, amps would be powered (active).

Any recommendations on how to do this? I've found few receivers or amps that have L R stereo LFE sub outputs.

Could I do it with a receiver that has A and B speaker outputs, and connect A L/R to the speakers, and B L/R to the subs (high level line in). I would then set the amp to play A+B, and the subs would not have any output to speakers, the mono connection would terminate at the sub.

I hope this makes sense!

[Pete_Hsu]

Hi zanon,

Does your pre-amp have left and right rca pre-outs? If so, then all you need to do is run from left pre-out to left low level input on one VTF sub, and right pre-out to right low level inputs on a second VTF sub.

If your processor does not have left/right rca pre-outs, then you need to tap into the signal from the main amplifier. Run speaker wire from the left outputs to left high level inputs on one subwoofer, and from right outputs to right high level inputs on the second subwoofer.

Sincerely,

[zanon]

hi pete:

great to hear from you! My current amp has no pre-outs, so I will have to go with your option #2. It sounds like it will work fine if I just wire up half the high-level inputs on the subs, leave the other half of the high-level inputs empty, and have no outputs either. That's great! I had no idea it could work like that. And I guess that the volume control on the amp will feed into the subs, even though they have their own level control too, yes?

Final question -- since my speakers are so efficient, I can drive them to very adequate SPL with my 15 W amp. But this amp cannot work with subs (no pre-outs, or secondary outs) so I am considering a new amp, like this 40 W Onkyo class-d amp has two speaker ouputs (A and B) for bi-amping.

http://www.onkyousa.com/model.cfm?m=A-5VL&class=Amplifier&p=i

I look at the schematic at I see that the two speaker outputs A and B are wired in parallel. I'm guessing that if I hook up subs as you suggest to output B, the impedence will be so high that essentially all 40 W will still be available for my speakers (which I will wire up on A). Running the amp on A+B will get me 40 W to my speakers, and stereo subs (which will have their own power amps, of course). Is this right?

Thanks!

[Pete_Hsu]

Hi zanon,

You don't need a secondary set of outputs to make use of the high level inputs on the subwoofer. Basically, the subwoofer will tap into the signal from the main amplifier (ie. the same signal that is sent to the main speakers). Since the subwoofer has it's own amplifier section, there is no noticeable drain on the main amplifier.

Take a look at page 3, "Method B" in the owner's manual here:

http://www.hsuresearch.com/products/VTF.pdf

Sincerely,

[zanon]

Hi Pete:

Again, thanks for your note. I see method B in the owner's manual, but it looks like the output to the satellites from the subwoofer would go through a low pass filter, or some other kind of crossover.

I want to maintain a direct, crossoverless/filter-less connection between my amp and my satellites.

Maybe I am wrong in thinking that the subwoofer outputs would go through a filter/crossover first, in which case method B is OK. Otherwise, having a second set of output terminals would work, as I don't have to use the subwoofer outputs and can just use half the high-level subwoofer inputs.

[Pete_Hsu]

Hey zanon,

Actually you won't need to use the subwoofer amplifier outputs back to the speakers, all you will need to feed is the high level inputs on the subwoofer. In a nutshell, there will be speaker wire running from the left speaker outputs on the main amplifier to both the left high level inputs on one subwoofer and to the left main speaker, and then there will be speaker wire running from the right speaker outputs on the main amplifier to both the right high level inputs on a second subwoofer and to the right main speaker. The subwoofers are literally tapping into the same signal that is intended for the left/right main speakers.

You are correct that on the VTF subwoofers, using the sub amplifier outputs back to the speakers does have some circuitry that helps to cut off lower frequencies sent to the main speakers, so don't use that.

Sincerely,

[zanon]

Perfect, that totally works. I'm thinking it has to be a bad idea to physically attach two wires to the output terminals on the amp, so it would need to be an amp with two stereo outputs, all wired in parallel (like the A, B, A+B Onkyo). If you can run two wires off the same terminal, it sounds like that will work too, although I don't think my current amp outputs can fit in two wires ; )

So, with such a setup, what Hsu speakers do you recommend? The room is very large, but I end up sitting close to the satellites to reduce ceiling reflection (ceiling is unfortunately high and vaulted). I play at modest volumes, and emphasis is 100% on transients, not on headroom. Need to keep everything on a tight budget though, since I will be needing two subs, and a new amp!