Pre out or subwoofer out

[alaios]

Hi all,
what is the difference between pre out and subwoofer out?
1. I have seen amps with L and R pre out and without subwoofer out. My thinking always was that this was for the subwoofer (thinking also of stereo subwoofer)
2. My tiny all in one denon has only a single subwoofer out and not pre out
3. One yamaha model has both:

can you please explain me their differences? If we connect to subwoofer out there is no way to ever have stereo subs (if that is needed / makes sense)

 

[Apesbrain]

Sub out is summed mono and depending on the amp may come after a low-pass filter, i.e. "pass only frequencies below X Hz". Otherwise, no real difference.

 

[DVDdoug]

On an AVR the sub-out is the ONLY way to get the "point one" LFE channel and bass management (crossover).

 

[gsp1971]

I have wondered about this as well.

My subwoofer has a single RCA "LINE IN" socket, obviously meant to work with an AVR's single LFE Out / Sub Out socket.

But I want to use the subwoofer in a 2.1 system.

Can I use the Pre Out sockets of a 2-channel amp and connect them to my subwoofer's single RCA "LINE IN" socket, using a Twin RCA to Single RCA cable?

Alternatively, the subwoofer manual states that for 2-channel application, I should use speaker level connections, i.e connect the subwoofer speakers terminals to the amp speaker terminals in parallel with the main speakers, like the picture below:

"For 2-channel operation, use speaker level rather than line level connections. The subwoofer presents a high impedance load to the stereo power amplifier and takes very little current, so may be connected in parallel with the main speakers with no adverse effects."

Has this been done successfully by anyone?

All help is appreciated.

GS

 

[reggiegasket]

REL subs advocate high-level connection (speaker-level), and that's what I've always done in my stereo setup, with various REL and BK subs, and it works well. They supply a speakon connector so connecting the wires at the sub end is easy.

One downside is that you can't apply a low pass filter this way. The L&R speakers get a full frequency signal.

You also have the option to run two subs: one connected to the left speaker and one to the right.

 

[gsp1971]

One downside is that you can't apply a low pass filter this way. The L&R speakers get a full frequency signal.

Which they would anyway in a 2.0 configuration, right?

My question is: do I need a slightly more powerful amp if I am to use speaker-level connection for the sub?

The "problem" is that I am looking to buy a new amplifier but very few 2-channel amplifiers have a Sub Out. So amplifier choices are limited.

But if I could use Pre Out or speaker-level connection with the sub, that would make so many more amps available to shortlist.

Perhaps using something like a miniDSP Flex and a power amp would be the best solution.

Thanks for your input.

GS

 

[reggiegasket]

Some amps let you send a 'trimmed' signal to the main L&R speakers, rather than the full signal. That way the main speakers are getting an 'easier' life, as is the amp itself. The sub then handles the low frequencies. This is only possible if you use the sub-out socket from the amp to the sub, and you need an amp with an app so you can tweak the settings (i.e. frequency) where the split takes place. The Bluesound Powernode has this I think.

>> do I need a slightly more powerful amp if I am to use speaker-level connection for the sub?
No. It draws very little so it's not an issue at all.

>> I am looking to buy a new amplifier but very few 2-channel amplifiers have a Sub Out.
Yeah, so just connect high-level and buy any amp on the planet

The pre out thing may work but you'd need to check this. Sub out is mono, whereas pre out is L&R, as said.

 

[gsp1971]

>> do I need a slightly more powerful amp if I am to use speaker-level connection for the sub?
No. It draws very little so it's not an issue at all.

>> I am looking to buy a new amplifier but very few 2-channel amplifiers have a Sub Out.
Yeah, so just connect high-level and buy any amp on the planet

The pre out thing may work but you'd need to check this. Sub out is mono, whereas pre out is L&R, as said.

Thank you, I will try it out.

 

[AudioJester]

REL subs advocate high-level connection (speaker-level), and that's what I've always done in my stereo setup, with various REL and BK subs, and it works well. They supply a speakon connector so connecting the wires at the sub end is easy.

One downside is that you can't apply a low pass filter this way. The L&R speakers get a full frequency signal.

You also have the option to run two subs: one connected to the left speaker and one to the right.

I never got my head around this with REL subs.
I mean high level / speaker output has much more noise/distortion than preout. But i guess its not as imprtant for bass frequencies.
High level to low level conversion must measure horribly??

 

[reggiegasket]

REL always said high-level was the best way (and they offered line-in too) as it aligned and integrated with the amp better. I've never done a back-to-back so couldn't say otherwise. Subs are all about placement and setup (level and frequency) in my experience, and a definite improvement for stereo listening.

 

[AudioJester]

Subs are all about placement and setup (level and frequency) in my experience, and a definite improvement for stereo listening.

Very true!

 

[JustJones]

In a previous life I had an NHT Sub 1. Used external amp and they said the best way to connect was high level. Notice the high pass and low pass, phase and gain on the amp. I liked I could keep the amp in the rack with everything and ran a special connection to the cabinet. Pretty good sub.

 

[Nutul]

Can I use the Pre Out sockets of a 2-channel amp and connect them to my subwoofer's single RCA "LINE IN" socket, using a Twin RCA to Single RCA cable?

View attachment 341746

never do that, as you are shortening the L/R signals.
Also, generally the sub is one because below a certain threshold soudwaves are no longer directional; I think the limit is somewhere around 100Hz.
Of course, if you have a high LPF, say at 120 or 150Hz, then you could benefit of two subs, as some of the frequencies handled by them are still directional.

 

[Chrispy]

REL always said high-level was the best way (and they offered line-in too) as it aligned and integrated with the amp better. I've never done a back-to-back so couldn't say otherwise. Subs are all about placement and setup (level and frequency) in my experience, and a definite improvement for stereo listening.

Think it also just makes it easier to sell to those with old 2ch gear with no bass management

 

[Beershaun]

Hi all,
what is the difference between pre out and subwoofer out?
1. I have seen amps with L and R pre out and without subwoofer out. My thinking always was that this was for the subwoofer (thinking also of stereo subwoofer)
2. My tiny all in one denon has only a single subwoofer out and not pre out
3. One yamaha model has both:
View attachment 341718
View attachment 341719


can you please explain me their differences? If we connect to subwoofer out there is no way to ever have stereo subs (if that is needed / makes sense)

If your budget allows, I'd look for an integrated amplifier or pre amp that has room correction/DSP built in and subwoofer out. Something like the minidsp flex. Two main benefits to your overall setup vs. a regular amp with high level outputs.

1) room correction software makes a big difference in audio quality especially at low frequency. It can also allow you to equalize your speaker frequency response all in the digital domain.

2) a subwoofer output sums the low frequency from both channels and the system creates a crossover sending only the low frequency to the subwoofer and not sending them to the mains. This relieves the main amplifier from handling the most power intensive low frequency signals. Also this reduces the distortion your speakers will have due to removing the low frequency from their operating range.

 

[alaios]

REL subs advocate high-level connection (speaker-level), and that's what I've always done in my stereo setup, with various REL and BK subs, and it works well. They supply a speakon connector so connecting the wires at the sub end is easy.

One downside is that you can't apply a low pass filter this way. The L&R speakers get a full frequency signal.

You also have the option to run two subs: one connected to the left speaker and one to the right.

Have you tried to compare the two scenarios?

High input for your REL and no high pass of the mains (what you have)

Vs


Low level input for RELs and high pass filter on the mains.

 

[alaios]

If your budget allows, I'd look for an integrated amplifier or pre amp that has room correction/DSP built in and subwoofer out. Something like the minidsp flex. Two main benefits to your overall setup vs. a regular amp with high level outputs.

1) room correction software makes a big difference in audio quality especially at low frequency. It can also allow you to equalize your speaker frequency response all in the digital domain.

2) a subwoofer output sums the low frequency from both channels and the system creates a crossover sending only the low frequency to the subwoofer and not sending them to the mains. This relieves the main amplifier from handling the most power intensive low frequency signals. Also this reduces the distortion your speakers will have due to removing the low frequency from their operating range.

the new yamaha 801 does some room correction if I am not wrong

 

[Chrispy]

Have you tried to compare the two scenarios?

High input for your REL and no high pass of the mains (what you have)

Vs


Low level input for RELs and high pass filter on the mains.

For what purpose? Just preference?

 

[alaios]

what subjectively sound better to you.

When REL says connect to high level input assumes rejects the benefits of high passing main speakers (if such benefits exist for your set speakers)

 

[reggiegasket]

No I haven't.