Subwoofer installation help

I've had my sub-woofer hooked up in the traditional speaker level connection but would like to run my mains full range and just add a bit of low end with the sub.So since it's a bit difficult to get to the back of my preamp could I run the speaker cable from my preamp to my main speakers then run a cable from my speaker to the sub speaker level input ? Thus having the mains running full range and having the option of adding a little lower end.

Any disadvantages to this hook up ?

Thanks

 

Does your sub have a crossover?

If so, yeah, that'll work, but better to get it/them a signal from the pre amp.

If not, then the sub/s will get a full spectrum signal, not a good thing.

 

It'd be easier to give you advice if you listed your equipment in your profile.

Are you using an integrated amp instead of a preamp?
Preamps don't usually have speaker outs.
I don't know if you can run speaker level from to your speaker first and then to your sub.
It might be easier to use interconnects from the preamp to your sub. That way, your mains will run full range and your sub will run up to the frequency you set on the crossover control.

 

You should be able to keep it the way that it is and adjust the crossover on the sub to the limit of your mains. I assume that you have your speakers attached to the outs on your sub. In this case the crossover on the sub should be able to do what you want to do. It's not good for the mains and the sub to be producing the same frequencies of bass. That may result in a cancellation which is not good.

 

Thanks for the quick response

my preamp has no sub out.It is a older Tandberg 3009A with two Tandberg 3009A mono blocks.The speakers are Soliloquy 6.3'S that are bi amp capable but have the jumper's installed.So with the cables coming from the power amp's to one set of the speaker terminals it would seem that I could use the second set of speaker terminals to run to the sub.Would that just be a simple series circuit ?

Yes the sub has a crossover that will filter the high end

 

In my sub, if I use the speaker level inputs, the crossover will also act as a high pass filter for the mains.
If you want your mains to operate full range, you'll need to use the preamp outs.
You could use Y connectors at your preamp outs to get interconnects to your sub.

 

Since the main speakers are being fed directly from the power amps and not by the subs speaker level out's ( which wouldn't be used in this case ) there wouldn't be a crossover involved to filter anything out.

 

You most definitely don't want to run the subs full range, but you may not have to crossover your mains. Assuming that they have a natural rolloff, you could just filter the highs out of your sub(s) and leave the mains alone. This would mean you'd have to set the internal LPF in the sub low enough to not duplicate the range of the mains.

I have a simple series capacitor in front of my main amp to cut the extreme bottom out of my mains, but that is not the easiest thing to do if you're not handy. In my case the crossover frequency is about 70Hz.

The easiest thing to do with entry level subs is to run the main speaker runs through the sub's built in passive crossover. That will work, but you're adding a lot of wire to your main runs. Granted much of the disadvantage of doing that is negated by relieving your mains of the lowest frequencies, but there are other reasons not to do that.

Also if you're running a single channel sub, you pretty much have to run both channels to it, to get a summed signal for the sub. Assuming your preamp doesn't have a sub output, there is no other easy way to do that. If you were to use a 'y' adapter pn your preamp outputs you will risk losing your stereo to your mains.

Another solution for this problem would be to use a buffer amp and 'y' the output of that to feed your subs. Any device, such as an abandoned cassette deck could be used to do this.

 

I'm probably wrong here but let me try to understand how this would be any different as far as the input to the sub is involved.

When using the line level connection installing a sub you connect the speaker output (which has all the frequency's ) to the speaker line input.Then you run the speaker line output to your mains which filters out the low frequency's to your mains.So I'm assuming the the sub has a crossover to limit the high frequency's right after the speaker line input as it also has a crossover to limit the low frequency's before the signal is sent back to the mains.

As far as the input to the sub it's the same as it always has been coming directly from the speaker out on the power amps.

 

You are somewhat correct, except for the terminology regarding line level. Line level is not the same as speaker level. Typically line inputs means RCA jacks, though they can be other types of connections such as XLR, Lemo, etc.

Speaker output levels are generally thought of in terms of power or watts. Line levels are generally a voltage level with reference to an impedance.

Typical in the pro world would be +4db (1.22v across 600 ohms). Most consumer gear uses -10db as their line level standard, which is 14 db less than the pro standard and usually around .3v across 10k ohms.

 

Doug

Thanks for pointing that out I did mean speaker level not line level or speaker line level.

 

Line level signals travel through RCA (or XLR) interconnects and link the preamp to the power amp.
Speaker levels are what come out of power amps and travel through speaker cables.

Some subs offer connection either way, with the speaker level going to the sub and its crossover, then going from the sub to the main speakers. This connection can place the sub's crossover in line with the mains (consult the manual). The sub only pulls the signal information and not the power from the speaker level signal.

Using the line level inputs into the sub won't involve the main speakers with the sub's crossover, because the mains are not connected to the sub.

 

I have an older integrated amp, the LFD Zero Mk III. It has 2 sets of speaker outputs, one set is currently connected to my Harbeth P3 speakers. It also has a tape out. Can I run speaker cable to a sub (Velodyne MiniVee 8") from my extra set of speaker outputs? Can I run an RCA cable from the tape out to the sub's Line In?

 

You should be able to run cables from your extra speaker outs to speaker level inputs on your sub if it has them. You'll need to play through both speaker outputs on your LFD to hear the sub, and adjust the sub's volume to match your main speakers, but you'll only need to do that once.

A tape out's volume doesn't change when you adjust the volume on the preamp, so your sub would only play at one loudness.

 

Makes sense thanks. I don't think the LFD integrated has a selector for speaker outs but maybe they are both on at the same time. Will try it when the sub arrives.

 

I don't know about the Velodyne, but some subs with speaker level inputs also have speaker level outputs to the main speakers and a crossover built in.

 

If your power amp can feed two pair of speakers you can hook your mains to speakers A and your sub to speakers B. That simple. I have them connected that way because I have a vintage receiver with no sub out and I'd want the mains in ¨large¨mode anyway because they have terrific low-end capabilities.

In that way you can take the sub off the loop whenever the mains render enough bass or get it on the loop for bass reinforcement or just low frequency extension. Needless to say you will need 8 cables to accomplish this. The impedance of an active sub input is so high the amplifier don't ¨see¨ it so no worries about overloading anything.

Hope it helped

 

Yeah that's what I'm gonna do Waxfreak thanks. Easy.

 

Bollocks. I've had my towers and sub connected in every possible way and ended up with the best results this way. Even with a good deal of overlapping a good portion of the low-end spectrum all you'll get is reinforced, extended bass . If you don't overlap you end up with a HUGE dip in frequency response where the mains' limits meet the sub's action.

 

Well if it worked for you that's good. I spent a long time getting my 2 subwoofers to work with the maximum amount of tight bass. Turns out what worked best in my room was one at the front and one at the back. I sit in the middle of the room due to having a surround system.

 

Oh, I see. Two subs CAN cause cancellations.

 

Luckily I got them right as I have never experienced such kick ass bass for music (and movies as well) in my life.

 

Not if you have the subs and mains crossed over the right way. I use two subs with KEF LS50s. Getting the subs placed correctly in the room crossed over at the right frequency with the right dropoff is key to not getting the dips you mention. I had to invest in a FirstWatt B4 to find a unit flexible enough to achieve this.

 

You both obviously know what you're doing and have set your subs in the right way. Congrats

 

I should have specified, the Velodyne is a powered sub, it's probably not ok to hook up a powered sub to the speaker outs of my integrated amp?