Wiring speakers to the sub

st170dan

Active Member
Hi, my sub on my hifi system has inputs for me to wire the speakers into. Why would I want to do this? What advantages, if any, are there over wiring the speakers to the amp? I have a Cambridge Audio amp FWIW.

Cheers
Dan
 

formbypc

Novice Member
If the sub is a passive one, with an internal crossover, the idea is to connect the amp to the sub, and the speaker output from the sub to the stereo speakers. That way the low freq is filtered out from the main speakers.

Without knowing what sub it is, it's difficult to tell.
 

st170dan

Active Member
Cheers mate, back looks like that but all the +ive and -ive channels are in line, not with the -ive in a square like that.
 

BlueWizard

Distinguished Member
With regard to most subs that have this feature, internal the Subwoofer, and between Speaker In and the Speaker Out are a couple of large capacitors to filter low bass and prevent if from being passed to the front speaker. This could be handy in a stereo system, but is of no use in a Surround Sound system, because the Surround Sound amp typically handles the crossovers, and the controls in the Sub itself aren't needed.

But, these capacitors that filter bass from the front speakers is a somewhat rude and crude method, and the crossover can vary with the impedance of the speaker. This Speaker Output is not likely to be controlled by the Subs internal crossovers, and the fixed crossover frequency of the capacitor could be anything from a 125hz up to 250hz.

To determine if you should do this, we would need to know specifically what amp and what front speakers you have.

This feature can be helpful to some people in some situations, but it is not generally recommended as it is too crude and uncontrollable.

Whether what I've said applies specifically to your Subwoofer or not, I can't be sure. But given that it is a Gale, I suspect it does apply.

Steve/bluewizard
 

BlueWizard

Distinguished Member
In the Subwoofer between the speaker in and the speaker out is a large capacitor. That filters out the low bass leaving the low bass in the Sub, and passing everything above that to the front speakers. Simple as that.

But it is not adjustable, the capacitor is what the capacitor is, and where the crossover is depends on the impedance of your speaker. Though typically this capacitor filter everything below roughly 150hz to 250hz. Precisely what and where the crossover is, is hard to determine, which is why I say it is a pretty crude method.

Again, this is primarily intended for system with limited range small Satellite speakers in front (in front meaning the main left/right speakers).

If you have decent bookshelf or floorstanding front speakers it is best to run them directly off the amp, and carefully adjust the sub controls for the best balance between the front and Sub speakers.

If you have small fragile speakers in front, or speakers with a very limited low end, then best use the Speaker Out on the Sub, and adjust the sub the best you can to match the front.

Steve/bluewizard
 

st170dan

Active Member
Ok, that makes sense now. I have floor standing speakers on my hifi and have them connected to the amp. By the sound of it then I should leave it this way. Just wondered why there was inputs on the subs for speakers - and now I know! Cheers.
 

BlueWizard

Distinguished Member
Inputs on the Subwoofer are a completely different subject. We were talking about Outputs on the Sub.

The Inputs on a Sub come in two types. One is the standard RCA-Phono Type (red, white) connectors, these are called Line Level Inputs, and are made to connect to amp Sub Outs or amp Pre Outs.

The Speaker Terminal Inputs on a Sub are referred to as High Level Inputs, or Speaker Level Inputs. If your amp does not have some type of Sub out or Pre-amp out, then you can connect the Speaker/High Level Inputs directly to the Speaker terminals of the amp. Internal to the Sub, those high level speaker signals are attenuated down to a level that is compatible with the Line Level Inputs of the Sub.

It simply give you two different ways to connect your amp to your Subwoofer.

The Speaker Terminal outputs on most Sub have a filter to stop low bass from getting to your front speakers. That leaves the Sub to handle all the low bass and eases the strain on the main front speakers. However, as I have pointed out the filter method is pretty crude and unpredictable, and would really only be needed with very small limited range front speaker.

The reason I asked about your amp is because I was wondering if it was a Stereo amp or if it might be a Surround Sound amp. Cambridge does or did make nice Surround Sound amps. If a stereo amp then everything we've said is true. However, if it is a Surround Sound amp, then likely it has some type of pre-amp or Subwoofer outputs, and that is what you should be using.

Again, we assume you are using a stereo amp, and if you are, and the Stereo amp has Pre-Amp out, then that is what you should be using. Though the Speaker Level Inputs on the Sub are fine, and if it is more convenient for you to use those, don't worry about it.

Steve/bluwizard
 

st170dan

Active Member
Ah I see now. I am using a stereo amp with a pre out for the sub which is what I have been using. My sub has high level input and output, but as you said I don't need to be using these.

Thanks for the info.
 

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