How to connect a Powered Sub in a Stereo set up?

[jagdish_p]

Hi All
I do not have a separate LFE out either in my source (WD Player) / DAC or in my Arcam A 28 Integrated Amp. My sub has a single RCA in.
My Arcam has preouts, and initially I connected the Left Channel to Sub In, I guess this is Line level without any filtering for Low Frequencies. This connection works.
Next I bought a Y RCA adaptor to connect both the Left and Right pre outs of the Stereo Amp to the Sub.
Today I realized that the Y RCA adaptor connected to the preouts is also mixing up the Front Speaker Out puts. With the result that I do not get Left and Right channel separation when I play a 2 Channel Track.
My queries:
a) How do I feed both Left and Right channel signals to a Powered Sub with a single RCA in? Are there any other subs with two separate inputs that do not mix up the signal upstream for the Fronts?
b) Is it OK if I connect the Sub to one channel only? Does it introduce an imbalance in the L & R speaker outputs?
PS: I know that that the purists will frown at the idea of connecting a Sub in a stereo set up for music. But I feel some tracks sound better this way
Thanks

 

[greenhorn]

You bought the wrong sub. Now you'll need some sort of filter somewhere
Active Sub-Woofer Filter

or
Active 2 Way Filter
if you want to high pass the fronts.

PS: a shallow sub with a 6.5" cone isn't going to add much to a couple of floorstanders having 6.5" drivers

 

[jagdish_p]

Yes my existing sub does not make any marked difference. Its carried over from a previous set up and I thought I will connect it as it is lying unused.
Eventually I plan to replace it some time in the future

Does the Kit suggested by you also have a housing and Audio Inputs and outputs ? Or is it a simply a PCB in which case where do I get the remaining components. I am OK with simple soldering of wires but will not venture into soldering components on to a PCB.

 

[hydrovac]

Hi All
I do not have a separate LFE out either in my source (WD Player) / DAC or in my Arcam A 28 Integrated Amp. My sub has a single RCA in.
My Arcam has preouts, and initially I connected the Left Channel to Sub In, I guess this is Line level without any filtering for Low Frequencies. This connection works.
Next I bought a Y RCA adaptor to connect both the Left and Right pre outs of the Stereo Amp to the Sub.
Today I realized that the Y RCA adaptor connected to the preouts is also mixing up the Front Speaker Out puts. With the result that I do not get Left and Right channel separation when I play a 2 Channel Track.
My queries:
a) How do I feed both Left and Right channel signals to a Powered Sub with a single RCA in? Are there any other subs with two separate inputs that do not mix up the signal upstream for the Fronts?
b) Is it OK if I connect the Sub to one channel only? Does it introduce an imbalance in the L & R speaker outputs?
PS: I know that that the purists will frown at the idea of connecting a Sub in a stereo set up for music. But I feel some tracks sound better this way
Thanks

Hi jagdish_p,

Can you tell us what make and model of the sub you are using. Whether any provision for high level inputs available?

Regards
Krishna

 

[jagdish_p]

The sub is Yamaha YST-FSW150.(Rest of the equipment in my signature)
It accepts only line level inputs
Extract from the manual:
INPUT terminal
Input terminal for line level signals from the amplifier

 

[greenhorn]

Yes my existing sub does not make any marked difference. Its carried over from a previous set up and I thought I will connect it as it is lying unused.
Eventually I plan to replace it some time in the future

Does the Kit suggested by you also have a housing and Audio Inputs and outputs ? Or is it a simply a PCB in which case where do I get the remaining components. I am OK with simple soldering of wires but will not venture into soldering components on to a PCB.

not really sure. this looks like a built board. You will have to solder connections to it though. RCA's and 2 DC power supplies (or a split PSU if you can find one)

 

[jagdish_p]

not really sure. this looks like a built board. You will have to solder connections to it though. RCA's and 2 DC power supplies (or a split PSU if you can find one)

Ok got it - Thanks

 

[greenhorn]

alternately, you can make a DIY Y cable using some RCA connectors and some wire. If you have an extra pre out, take 2x 10K (this value really doesnt matter as long as its between 1k and 47K and you can adjust the gain on your sub) and then use them to connect the signals together

L->10K->output<-10k<-R

it will look something like this. It's a quick and dirty way to be up and running

 

[jagdish_p]

Thanks. Are there any specific type of resistors recommended for Audio?

Also should I add two more resistors for the ground wires also?

 

[greenhorn]

nah, any resistor will do. The ground wires should be shorted directly together. - they should be shorted together anyway internally

 

[arj]

Are you sure your front speaker signals are getting mixed uo when you put a Y splitter on the Sub ?
if you have this on the sub and are using the pre outs form the amp via two RCA getting summed up in thes ub, your speakers should have No impact.
do ou have a crossover setting on the dub ? that needs to be turned lower than the speaker s lower freq point.

if it does there is a problem in the in amp is what i would suspect.

Not sure if i got the problem right..

 

[jagdish_p]

Are you sure your front speaker signals are getting mixed uo when you put a Y splitter on the Sub ?
if you have this on the sub and are using the pre outs form the amp via two RCA getting summed up in thes ub, your speakers should have No impact.
do ou have a crossover setting on the dub ? that needs to be turned lower than the speaker s lower freq point.

if it does there is a problem in the in amp is what i would suspect.

Not sure if i got the problem right..

1) yes I am sure the signal is getting mixed up. Checked with a test track.
2) yes I have used something similar y splitter- only change being its a 2 male to 1 female RCA and connected to the 2 Amp preouts at the amp end as I wanted to avoid 2 cables run to the sub
3) No my Sub does not have a crossover setting.

Yes even I am wondering if there is something wrong with the Amp as I would expect the pre outs to be isolated from the powered outs.

 

[Santy]

Are you sure your front speaker signals are getting mixed uo when you put a Y splitter on the Sub ?
if you have this on the sub and are using the pre outs form the amp via two RCA getting summed up in thes ub, your speakers should have No impact.

Are you sure mixing L/R of the preouts is safe ? Not sure about the preout of an amp but if we were to short it at source level, can it not damage the circuits? Have always been wondering about this.

@ jagdish

Is this the sub you are trying to connect?

boy it dosen't even have a crossover control it seems.. It is not ideal for stereo in that case.

 

[jagdish_p]

Yes Santy you posted the correct Sub picture. I had this lying around unused and wanted to try it out .

Regarding shorting the pre outs together, except for the L& R channels getting mixed up it did not cause any other problems in the Amp.

OK so what are the other Sub options if I am planning a new Sub? ( I do not have a crossover setting on my Amp nor do I have an LFE out- I can use the pre outs for connecting the Sub)

Are there Subs available with separate L & R inputs - line level or speaker level?
If it is speaker level do I connect the L&R speakers to the sub with cross over happening in the Sub? Will the Sub crossover degrade the SQ to Front Speakers?

 

[arj]

I agree with Santy/kapvin. with no crossover setting you have the wrong sub. and need to have a crossover put in. can be a simple one.

but if you are seeing the impact of this connection as a feedback on the main speakers , there is something wrong with the Amp !!! its supposed to abe a preamp out, not an in.
What i suggest is only use either the left or the right on o the sub.

[Ignore]Santy,from how i understand it, it should not have any problem if you connectit it...this only get summed and not really shorted since this is L&R and not opposing current[ignore]

 

[Santy]

Santy,from how i understand it, it should not have any problem if you connectit it...this only get summed and not really shorted since this is L&R and not opposing current

Noted, thanks arj.

Yes Santy you posted the correct Sub picture. I had this lying around unused and wanted to try it out .

You could use it as an underseat active sub in your car with a DC-220vAC convertor.

OK so what are the other Sub options if I am planning a new Sub? ( I do not have a crossover setting on my Amp nor do I have an LFE out- I can use the pre outs for connecting the Sub)

Are there Subs available with separate L & R inputs - line level or speaker level?
If it is speaker level do I connect the L&R speakers to the sub with cross over happening in the Sub? Will the Sub crossover degrade the SQ to Front Speakers?

Even proper entry level subs will have cross over settings. Almost all of them have stereo inputs and many have speaker lever inputs. Some subwoofers have speaker level in and OUT as well. So you can connect your amp output to the sub and then from the sub to the speakers. There could be slight quality loss, but that is because of the extra component in the chain not because of the cross over circuit exactly.

If I am correct, it works this way
Speaker in - > Split 1 -> Line level convertor -> Cross over -> Mono Amp -> Woofer
.............. - > Split 2 -> Speaker out

 

[jagdish_p]

Thanks ARJ. I have the schematic of the A 28. ( which I can share through e mail with any one interested) I tried to follow the signal paths and see if connecting the Preouts together will merge the sound signal for the Amp section. I am a total novice at reading the diagrams and couldn't make out

 

[arj]

this seems to be a sub meant to be used only in an HT with an LFE out..does not have a crossover at all.
from what i see of your speakers..if you use a sub you need a much better one. POssible that you are only thinking you are getting good bass here. in reality it very well could be a lower mid bass thump which sakes your gut but does not do any good to the quality of the sound

BTW why dont you connect it to your Yamaha AVR ? if it has a pre in, then give the aracam pre out t the avr pre in
frankly..its complicated and not worth the trouble.

 

[greenhorn]

arj, I'm not sure about the direction this thread is going, or if you are answering the right question , but you DO NOT short the pre out L&R using a Y cable. It WILL blow the output transistors in the pre outs , if the pre outs are driven by a discrete stage. More likely, they will be op amp driven, in which case, their output protection should save them, but don't count on it.
Also, if there is no seperate buffer for the pre out, and the pre outs are fed directly from the gain stage - the same point which is connected to the power stage, then this will mess up the input to the power amp section, and you will hear some weird sound

This is why I suggested using resistors in between to make the DIY stereo to mono convertor. I thought this question was settled. Jagdish, do you have any further questions?

 

[arj]

arj, I'm not sure about the direction this thread is going, or if you are answering the right question , but you DO NOT short the pre out L&R using a Y cable. It WILL blow the output transistors in the pre outs , if the pre outs are driven by a discrete stage. More likely, they will be op amp driven, in which case, their output protection should save them, but don't count on it.
Also, if there is no seperate buffer for the pre out, and the pre outs are fed directly from the gain stage - the same point which is connected to the power stage, then this will mess up the input to the power amp section, and you will hear some weird sound

This is why I suggested using resistors in between to make the DIY stereo to mono convertor. I thought this question was settled. Jagdish, do you have any further questions?

Thanks.,corrected my comment. I thought per outs are additive in nature and not sure why I remember it as so. My apologies
I guess only option is using only L or R ?