Head-Fi.org › Forums › Equipment Forums › Cables, Power, Tweaks, Speakers, Accessories (DBT-Free Forum) › How do subwoofers connect to an amp?
New Posts  All Forums:Forum Nav:

How do subwoofers connect to an amp?

post #1 of 14
Thread Starter 

I'm quite new to speakers and stuff (been into headphones more). However, I am looking into a new setup. I want a subwoofer as i'm into quite bassy music (electro/dub etc...). How do you wire a sub up to an amp? Do they have their own plug, does it wire to speakers etc...?

 

I've been looking at amps, but I never know whether I can hook a sub up to them or what? 

post #2 of 14

Generally subwoofers have their own built-in amplifier, and hook up to a pre-amplified sub-out/LFE-out or pre-amplified RCA outputs via RCA cables. Some subwoofers also have speaker-level inputs that you connect to the speaker-level outputs of your amplifier via speaker wire, though the internal amplifier on the subwoofer is still doing the work. Few subs have speaker-level outputs that pass through the signal from the amplifier to speakers, but generally the speaker-level input-output transition negatively impacts the signal.

 

Very few subwoofers are passive, in which case you will have to dedicate an amplifier to these units and wire it up via speaker cable. They end up being very expensive to get right, and generally don't perform any better than the best of active-powered subwoofers in the appropriate price range.

post #3 of 14
Thread Starter 
Quote:
Originally Posted by 3X0 View Post

Generally subwoofers have their own built-in amplifier, and hook up to a pre-amplified sub-out/LFE-out or pre-amplified RCA outputs via RCA cables. Some subwoofers also have speaker-level inputs that you connect to the speaker-level outputs of your amplifier via speaker wire, though the internal amplifier on the subwoofer is still doing the work. Few subs have speaker-level outputs that pass through the signal from the amplifier to speakers, but generally the speaker-level input-output transition negatively impacts the signal.

 

Very few subwoofers are passive, in which case you will have to dedicate an amplifier to these units and wire it up via speaker cable. They end up being very expensive to get right, and generally don't perform any better than the best of active-powered subwoofers in the appropriate price range.

 

Ah, thank you, this is what I was looking for. So, most subs just have red/white RCA cables and attach to a Line-Out plug, or is there a dedicated plug in which the sub has to be connected to? Do most amplifiers have a sub-out connector, or just the more expensive ones? I was looking at the Cambridge Audio 640A V2 (Can't afford the new ones!). So, from the picture below, the amp would connect to the "pre-out" RCA jacks?

 

640a-v2-rear

post #4 of 14
Quote:
Originally Posted by alex98uk View Post



 

Ah, thank you, this is what I was looking for. So, most subs just have red/white RCA cables and attach to a Line-Out plug, or is there a dedicated plug in which the sub has to be connected to? Do most amplifiers have a sub-out connector, or just the more expensive ones? I was looking at the Cambridge Audio 640A V2 (Can't afford the new ones!). So, from the picture below, the amp would connect to the "pre-out" RCA jacks?


Yes, you would have to connect the pre-out RCA jacks to the line-in RCA jacks on the subwoofer via speaker cable. Lower-end subwoofers will have only a single RCA line-in/sub-in/LFE-in so you will only have to merge the outputs. Almost all subwoofers have just the inputs, so you'll have to buy the RCA cables for the hookup if they're not provided.

 

Most 2-channel stereo amplifiers (music usage) have pre-amplified outputs only. Sub-outs and LFE-outs are used almost exclusively in AV receivers (home theater usage).

post #5 of 14
Thread Starter 
Quote:
Originally Posted by 3X0 View Post




Yes, you would have to connect the pre-out RCA jacks to the line-in RCA jacks on the subwoofer via speaker cable. Lower-end subwoofers will have only a single RCA line-in/sub-in/LFE-in so you will only have to merge the outputs. Almost all subwoofers have just the inputs, so you'll have to buy the RCA cables for the hookup if they're not provided.

 

Most 2-channel stereo amplifiers (music usage) have pre-amplified outputs only. Sub-outs and LFE-outs are used almost exclusively in AV receivers (home theater usage).

 

Cool, I think that just about answers everything! One more question, how would you merge two RCA cables from the Pre-Out jacks to a single plug for the Line-In on the subwoofer? Is there some sort of converter?

 

What is the difference between LFE out, Sub Out and Pre-Out? Anything in particular?
 

post #6 of 14

Most subwoofers have RCA input jacks and speaker level inputs. Additionally, subwoofers may have a low-pass filter which filters out any high frequencies so that they the subwoofer doesn't try to play them. Depending on the subwoofer, this low-pass filter may be defeatable or may only work on the speaker level inputs. It just depends on the model, so read the subwoofer's manual.

 

Amplifiers designed for home theater purposes (what you find at Best Buy) usually have a single RCA out jack labeled "LFE" (low frequency effect) or "SUB OUT." In this case, the amplifier either sends the LFE channel in a 5.1 mix (i.e. from Dolby Digital or DTS) directly to this jack or mixes in low frequencies from other channels and sends it to this jack. This LFE RCA jack should be connected to either the left or right RCA input jack on the subwoofer. It doesn't matter which one since they get mixed together by the subwoofer. Additionally, you should turn off the subwoofer's low-pass filter since the amplifier takes care of that job.

 

Stereo amplifiers, on the other hand, usually do not have an output jack specifically for LFE signals because they do not mix low frequencies into a signal channel like a home theater amplifier does. In this case, you can either connect the pre-out RCA jacks (both left and right) to the subwoofers RCA input jacks (both left and right), or run another set of speaker wires for both the left and right channels from the amplifier's speaker outputs to the subwoofer's speaker inputs. In either case, you will want to enable the subwoofer's low-pass filter since you will be sending the full frequency spectrum to it.

post #7 of 14
Thread Starter 
Quote:
Originally Posted by chronomitch View Post

Most subwoofers have RCA input jacks and speaker level inputs. Additionally, subwoofers may have a low-pass filter which filters out any high frequencies so that they the subwoofer doesn't try to play them. Depending on the subwoofer, this low-pass filter may be defeatable or may only work on the speaker level inputs. It just depends on the model, so read the subwoofer's manual.

 

Amplifiers designed for home theater purposes (what you find at Best Buy) usually have a single RCA out jack labeled "LFE" (low frequency effect) or "SUB OUT." In this case, the amplifier either sends the LFE channel in a 5.1 mix (i.e. from Dolby Digital or DTS) directly to this jack or mixes in low frequencies from other channels and sends it to this jack. This LFE RCA jack should be connected to either the left or right RCA input jack on the subwoofer. It doesn't matter which one since they get mixed together by the subwoofer. Additionally, you should turn off the subwoofer's low-pass filter since the amplifier takes care of that job.

 

Stereo amplifiers, on the other hand, usually do not have an output jack specifically for LFE signals because they do not mix low frequencies into a signal channel like a home theater amplifier does. In this case, you can either connect the pre-out RCA jacks (both left and right) to the subwoofers RCA input jacks (both left and right), or run another set of speaker wires for both the left and right channels from the amplifier's speaker outputs to the subwoofer's speaker inputs. In either case, you will want to enable the subwoofer's low-pass filter since you will be sending the full frequency spectrum to it.


Yeah, i'll be using a Stereo Amp, not a home receiver. So, if I buy a sub, I need to make sure it has "low pass filter". This I guess is just activated/deactivated via a switch on the back of the sub? I think I have my head around everything now!

post #8 of 14

Most decent subs have both a switch to turn the low-pass filter on and off and a dial to set the frequency cut-off point. Generally speaking, 80hz is a good cut-off point, but it all depends on your speakers and purpose of your setup. Also, you may not even want to turn the low-pass filter on. It just depends on your preference and speaker/amplifier setup. For example, I have a 2.1 setup with some small bookshelf speakers (B&W 686) and an HSU STF-2 subwoofer, and I find that it sounds better with the low-pass filter off because it allows the subwoofer to pick up and play the mid-bass better, a place where the speakers are a little weak.

 

Just experiment and do whatever sounds best to you.

 

Also, I'm not sure what brands you're looking at, but I'm a big fan of HSU subs. They are definitely not the best looking subs, but they give some of the best value (and sound) for the money, IMO.

post #9 of 14
Thread Starter 

Yea, 2.1 is what I want. It's kind of annoying, I was hoping there would be another line-out that I could use to pass onto my LD MKIII headphone amp. That way I could use the same source, DAC and just switch between headphones and speakers. But, if the subwoofer uses the pre-out, I guess I can't connect my headphone amp anywhere :(


Edited by alex98uk - 7/15/10 at 9:44am
post #10 of 14

In that case, why don't you connect the subwoofer using the Speaker B terminals? That would reserve the pre-out RCA jacks for your headphone amp.

post #11 of 14
Thread Starter 
Quote:
Originally Posted by chronomitch View Post

In that case, why don't you connect the subwoofer using the Speaker B terminals? That would reserve the pre-out RCA jacks for your headphone amp.


You sir have good ideas! Is there any difference between using speaker B and Pre-Out jacks? I assume they both pass through the full spectrum? Just out of interest, is there any real advantage over bi-wiring speakers?

 

Lastly, the pre-out will be an OK source for the Headphone Amp right and the Zero '09 an OK DAC (in terms of usability). 

post #12 of 14
Quote:
Originally Posted by alex98uk View Post

Yea, 2.1 is what I want.


You will only get 2-channel audio proper. The .1 is specific to home theater usage and AVRs where the lower frequencies are mixed into the discrete LFE channel (the .1 in x.1 setups).

 

You should be connecting the headphone amp to a fixed line-level output, not a pre-amplified output.


Edited by 3X0 - 7/15/10 at 10:13am
post #13 of 14

Actually, on second thought, you should probably connect your headphone amp to one of the "Rec Out" outputs on your integrated amplifier. The Rec Out is the same thing as a Tape Out, which is just a loop output from whatever is input (i.e. there is no volume control or amplification). This will prevent the source signal from being amplified twice (once in the integrated amplifier and once in the headphone amplifier). You can then use the Pre Outs for the subwoofer.

 

*Edit*

3X0 beat me to it.

post #14 of 14
Thread Starter 

OK, cheers guys. So to sum up:

 

My headphone amp will go on the Rec Out

Sub wired up to either speakers terminal B or pre-out (leaving space for another set of speakers if needs be).

The sub should have "low pass filter" ability

 

Excellent, well I think that has answered all my questions, now just to look for some nice speakers and a sub. Rep+ is just "thumbs up" on Head-Fi right?

New Posts  All Forums:Forum Nav:
Head-Fi.org › Forums › Equipment Forums › Cables, Power, Tweaks, Speakers, Accessories (DBT-Free Forum) › How do subwoofers connect to an amp?