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Connecting an active subwoofer to MOTU 4pre

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Discussion related to installation, configuration and use of MOTU hardware such as MIDI interfaces, audio interfaces, etc. with Windows

Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Tue Apr 17, 2012 7:57 am

Hello everyone,

I have my 4pre up and running with 2 active studio monitors connected to the Main 1-2 outs.
The Line 3-4 outs will feed a headphone distribution module.

I got myself an active subwoofer which of course, has a phono sub input.

My question, what would be the most effective way to get the signal from my 4 pre to feed my sub.

Thanks and regards,

Dan
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Re: Connecting an active subwoofer to MOTU 4pre

Postby torrentg » Tue Apr 17, 2012 8:29 pm

I just looked at the unit on MOTU.com.

Seems you have two choices if you leave your previous connections as is.

1) Use S/PDIF out to subwoofer in, if subwoofer has that connection ability.

2) Use one of the front analogue headphone outputs connected to subwoofer input. Use a cable with 1/4" stereo plug to dual rca mono.


------

What I would do is actually use one of the front headphone sockets to feed the headphone distribution amp module.

Then, just use rear output 3+4 to feed the subwoofer.

If you do this, you'll need two of the same cables: 1/4" mono to RCA mono
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Wed Apr 18, 2012 5:18 am

Thank you very much "torrentg", using s/pdif and headphones outputs is a solution I have not thought about(obviousely) and in addition, I realise that I should have given more precise details about the subwoofer i/o capabalities.

There are binding post (banana) type speaker level i/o for left and right (can I really use 1/4" to loose ends with banana connectors.
Also a phono (rca) type called "Subwoofer Input". I don't know if that one is s/pdif but it just might be.

If s/pdif works, do I have to configure anything specific on the 4pre?

Regards,

Dan
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Wed Apr 18, 2012 1:12 pm

After a little investigation, I found that the rca type "Subwoofer Input" is a line level input and has nothing to do with s/pdif.

If I didn't want to clutter my 4pre front panel with extra wires, I was suggested to use 1/4" Y connectors to come out of the line 3-4 outs right and left.

One leg (of L-R) would feed the headphone amp console (L-R) and the 2 others could go back in a 1/4" female (2) to phono Y connector to feed the sub through it's phono sub input.

Do you think this would work?

If connected that way, is the main volume controlling 3-4 out as well as the main 1-2 outputs?
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Re: Connecting an active subwoofer to MOTU 4pre

Postby torrentg » Wed Apr 18, 2012 11:08 pm

DanFuzz wrote:There are binding post (banana) type speaker level i/o for left and right (can I really use 1/4" to loose ends with banana connectors.


I don't know the subwoofer unit, but if those posts are connections to the power amp, then yes. Use two separate mono 1'4" cables, with each having one end stripped to bare wire to make the connections.


DanFuzz wrote:If I didn't want to clutter my 4pre front panel with extra wires, I was suggested to use 1/4" Y connectors to come out of the line 3-4 outs right and left.

One leg (of L-R) would feed the headphone amp console (L-R) and the 2 others could go back in a 1/4" female (2) to phono Y connector to feed the sub through it's phono sub input.

Do you think this would work?


No, this won't work. You would end up with only the left channel feeding entire headphones (or the mix set instead, but both speakers on headphones could only be a mirror of each other) - and the same would happen to the subwoofer.

The analog outputs 3, 4 (1, 2 also) are single track mono and not stereo.

If you're talking about splitting each the 3 and 4 to both have 2 outputs instead of the one coming out the MOTU, I would not do that. It has to do with impedence and resistance. You don't really want two units being fed by what is designed to feed only one. There will be signal degradation.

So to feed only the subwoofer, you would need to use both 3 and 4 outputs, 3 panned to hard left and 4 panned to hard right.

Then you can use the stereo headphones output in the front to feed the headphones distributor.
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Thu Apr 19, 2012 7:03 am

torrentg wrote:
"If you're talking about splitting each the 3 and 4 to both have 2 outputs instead of the one coming out the MOTU"

Yes, this is exactly what I meant.

It's a Kef subwoofer...Yes, it seems like you could come out of an amp or receiver (L-R speaker level outs) with regular speaker wires and then connect them to the sub's "Speaker Level Input" banana type (+/- left, +/- right)...and then from "Speaker Level outputs" (+/- left, +/- right) of the sub again to the main speakers...so this is probably an option for those who don't have a dedicated "Sub out" on their gear to bring the signal in the sub.

MOTU should add this feature (sub out) on their gear.

torrentg wrote:
I don't know the subwoofer unit, but if those posts are connections to the power amp, then yes. Use two separate mono 1'4" cables, with each having one end stripped to bare wire to make the connections.

For the sub: I like the idea with 1/4" to loose ends but will the 3-4 line level outs be right to feed the speaker level banana in of the sub? Or else would I rather come out 3-4 with "Y" 1/4" to one rca (phono) to feed the phono sub input which I believe is line level! Are the 3-4 outs the same as 1-2...is there always signal there even when not connected and are they controlled by the Main Volume? I made a test by disconnecting my powered monitors from 1-2 and connected them in 3-4 to check the result and I had no sound at all. How do I configure the 4pre to make this work?
Because I believe the sub has to be controlled with the Main volume as well!

Last, for my headphone distribution amp (it needs 1/4" L-R feed), I understand that if using the Main headphone out and "Y" with 1/4" stereo to dual 1/4" mono (L-R) I would be in business with this one since the Main volume affects that phone out directly, right?

Thanks again for an outstanding comprehension and support,

Dan
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Wed Apr 25, 2012 11:29 am

Hi again,

I think I may have found the most straight forward and efficient way tu plug both my subwoofer and Rane Stereo Headphone console...

Since the 3-4 line outs of the 4pre are 1/4" TRS and the inputs of the Rane unit 1/4" TRS as well, this is surely the simplest way to go.

As for the subwoofer with mono phono type (rca) input, I'll make a wire (yes I can make wires ;o)) with 1/4" stereo to rca mono using a studio grade shielded wire and connect it from the Main headphone out (controlled by the main volume) to the suwoofer.

Please tell me what you think!

Dan
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Re: Connecting an active subwoofer to MOTU 4pre

Postby torrentg » Wed Apr 25, 2012 1:49 pm

Sounds good to me. Tell us how it goes after trying it! The way you describe, you can even use the MOTU itself to set bass level, in comparison to everything else.
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Wed Apr 25, 2012 8:19 pm

torrentg wrote:
...you can even use the MOTU itself to set bass level...


I'm not sure what you mean by that...
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Re: Connecting an active subwoofer to MOTU 4pre

Postby torrentg » Wed Apr 25, 2012 8:41 pm

Well, since you can set the volume level for the heaphones output independently and your subwoofer will be connected to that, all you need to do is raise or lower the headphone volume to set the bass volume.

But i just re-read what you intend to do.

"As for the subwoofer with mono phono type (rca) input,"

Are you sure that is not S/PDIF input instead? I can't see a subwoofer having only a single mono input.
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Mon Apr 30, 2012 8:38 am

I know what you mean but I checked with the sales person (quite knowledgeable dude, known him for more than 25 years) I got it from and he told me it was line level input. I bought this unit second hand so maybe at the time it was made, they didn't provide L-R inputs because a sub is mono in itself and you had to get 2 to have L-R sub signal...

Dan
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Mon Apr 30, 2012 8:51 am

Oh and yes of course about controlling the sub's volume with the MOTU volume...I thought you were reffering to something else.
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Re: Connecting an active subwoofer to MOTU 4pre

Postby DanFuzz » Mon May 07, 2012 8:45 pm

So, I connected my sub the way I described and it works just fine!!

Dan
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