Subwoofer connection question

Nelis87

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Never ever owned a subwoofer before. So I have seen amps and receivers with subwoofer out, subwoofer pre out and line out to connect a subwoofer (if im correct). Whats the difference between the three and which is preferable? Any difference sound quality wise?
 

Pedro

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Like you I've never owned a subwoofer. It is my understanding that most of them are powered, ie, they have their own amplification built-in. So if you buy a powered subwoofer you will only need a preamp out (line level) on your amp/receiver (RCA usually I think).

Maybe I'm wrong but it seems the connections you describe are the same...

With a non powered subwoofer your amp/receiver would be doing the amplification, like with regular passive speakers, via speaker cable.
 

Oldphrt

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Gray said:
I've never owned one either but:

'Subwoofer out' and 'subwoofer pre out' are different names given for the same thing.

(Just 'Sub out' or 'Subwoofer out' will be the most common ways that you'll see it labelled)

In other words, low frequencies only, out of an RCA socket, ready to be amplified by an active sub.

IMPORTANT: Don't connect a subwoofer to anything marked as just 'Line out' or 'Preamp out'. Either of those won't be giving it what it wants. (Wouldn't damage anything, but just avoid it)

Nope. Preamp out is exactly what is required. Some subs allow connection to loudspeakers too.
 

MajorFubar

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Gray said:
You're not saying that it would be right for me to connect either of them to an active sub are you?

If it's a true pre-out and not a line-out, Yes. Active subs usually have their own [user adjustable] low-pass circuitry so they don't need any special output from an amp. Certainly my Gemini II does and it's one of the cheapest you can buy. AV amps with dedicated sub outputs will probably have low-pass and high-pass filters built in to help integrate the sub with the main speakers, but it's not mandatory.
 

Andrewjvt

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Gray said:
Oldphrt said:
Gray said:
I've never owned one either but:

'Subwoofer out' and 'subwoofer pre out' are different names given for the same thing.

(Just 'Sub out' or 'Subwoofer out' will be the most common ways that you'll see it labelled)

In other words, low frequencies only, out of an RCA socket, ready to be amplified by an active sub.

IMPORTANT: Don't connect a subwoofer to anything marked as just 'Line out' or 'Preamp out'. Either of those won't be giving it what it wants. (Wouldn't damage anything, but just avoid it)

Nope. Preamp out is exactly what is required. Some subs allow connection to loudspeakers too.

When you say, 'Preamp out is exactly what is required' do you mean specifically on AV amps?

As you will know Oldphrt, my Cyrus amp has two RCA output sockets labelled 'Pre out'.

You're not saying that it would be right for me to connect either of them to an active sub are you?

I could understand if the appropriate sub out on an AV amp was marked 'Sub pre out' but I'm (genuinely) ready to be educated:

Are you telling me that, on an AV amp (or anything else), there are RCA sockets intended for connection to an active subwoofer, that are marked with just 'pre out' ?

thats how i connect mine -

pre out to sub

Only a handful of stereo amps will have a dedicated sub out built in - the sub out is mostly from av amps. the pre out is fine - it will send full signal to the sub and you just adjust the frequency cut off on the sub.
 

Gray

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Oldphrt said:
Gray said:
Don't connect a subwoofer to anything marked as just 'Line out' or 'Preamp out'. Either of those won't be giving it what it wants. (Wouldn't damage anything, but just avoid it)

Nope. Preamp out is exactly what is required. Some subs allow connection to loudspeakers too.

When you say, 'Preamp out is exactly what is required' do you mean specifically on AV amps?

As you will know Oldphrt, my Cyrus amp has two RCA output sockets labelled 'Pre out'.

You're not saying that it would be right for me to connect either of them to an active sub are you?

I could understand if the appropriate sub out on an AV amp was marked 'Sub pre out' but I'm (genuinely) ready to be educated:

Are you telling me that, on an AV amp (or anything else), there are RCA sockets intended for connection to an active subwoofer, that are marked with just 'pre out' ?
 

Gray

Well-known member
Andrewjvt said:
Gray said:
Oldphrt said:
Gray said:
I've never owned one either but:

'Subwoofer out' and 'subwoofer pre out' are different names given for the same thing.

(Just 'Sub out' or 'Subwoofer out' will be the most common ways that you'll see it labelled)

In other words, low frequencies only, out of an RCA socket, ready to be amplified by an active sub.

IMPORTANT: Don't connect a subwoofer to anything marked as just 'Line out' or 'Preamp out'. Either of those won't be giving it what it wants. (Wouldn't damage anything, but just avoid it)

Nope. Preamp out is exactly what is required. Some subs allow connection to loudspeakers too.

When you say, 'Preamp out is exactly what is required' do you mean specifically on AV amps?

As you will know Oldphrt, my Cyrus amp has two RCA output sockets labelled 'Pre out'.

You're not saying that it would be right for me to connect either of them to an active sub are you?

I could understand if the appropriate sub out on an AV amp was marked 'Sub pre out' but I'm (genuinely) ready to be educated:

Are you telling me that, on an AV amp (or anything else), there are RCA sockets intended for connection to an active subwoofer, that are marked with just 'pre out' ?

thats how i connect mine -

pre out to sub

Only a handful of stereo amps will have a dedicated sub out built in - the sub out is mostly from av amps. the pre out is fine - it will send full signal to the sub and you just adjust the frequency cut off on the sub.

You've answered my last question to Oldphrt, thanks.
 

Gray

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MajorFubar said:
Gray said:
You're not saying that it would be right for me to connect either of them to an active sub are you?

If it's a true pre-out and not a line-out, Yes. Active subs usually have their own [user adjustable] low-pass circuitry so they don't need any special output from an amp. Certainly my Gemini II does and it's one of the cheapest you can buy. AV amps with dedicated sub outputs will probably have low-pass and high-pass filters built in to help integrate the sub with the main speakers, but it's not mandatory.

So your advice is that the answer to my last sentence question to Oldphrt, would be yes, and you'd need to ensure that your're sub is of the type with its own low pass filter.
 

Gray

Well-known member
With thanks to Oldphrt for originally correcting my incorrect 'IMPORTANT' advice and to Major and Andrewjvt for confirming the correction, you should now be an expert (if you're still around!)

I've learned that some subwoofers do their own filtering of a signal and so can indeed be fed by a signal from an AV amp RCA socket marked just, 'Pre out'

I already knew that, "A little knowledge is worse than none at all" but have learned to bear that in mind before making 'IMPORTANT' catagorical statements. It should be clear to you that the above contributors own subwoofers / at least know what they're talking about, wheras I do not.

(I've edited my post #3, but you will see the original, subsequently quoted in posts).

Bottom line advice to you, if thinking about a subwoofer is: Be sure whether it needs a filtered or unfiltered signal to its input - and know what the AV amp is giving it - however they've decided to label the RCA socket on the AV amp!
 

Gray

Well-known member
Oldphrt said:
All the active subs that I know of have a low pass filter. They have to, a stereo amplifier doesn't have one.

I was thinking more about AV amps. The majority of stereo amplifiers don't have dedicated sub outputs.

Something like the Denon mini system certainly does. From that you'd get a filtered output. If you connected that to any full-range input, you'd hear only LF.

Surely you're not saying no subwoofer is sent pre filtered LF?
 

Oldphrt

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I know of no active subwoofer that doesn't have a low pass filter. The market for such a device would be very small. Most have variable crossover.
 

jonathanRD

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Nelis87 said:
Never ever owned a subwoofer before. So I have seen amps and receivers with subwoofer out, subwoofer pre out and line out to connect a subwoofer (if im correct). Whats the difference between the three and which is preferable? Any difference sound quality wise?

Trying not to confuse matters, as the latest posts cover the first part of the question, but I thought it was interesting to add BK's take on sound quality.

To quote BK's XXLS400 sub owner's manual 'The high level input, is an unbalanced dual channel (stereo) input ......... Signals for this input would normally be sourced from the left and right speaker terminals of the main system amplifier. The advantage of this method is that the XXLS400 recieves exactly the same signal as being supplied to the main speakers. This means that the character and tonal balance of the bass from the main speakers is carried through to the sub bass'.

I should add that this is for a connection with a 'hifi' amplifier to listen to music.
 

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