Low Sub Out signal

[BmoreBirds]

Newbie here...

I have a Martin Logan soundbar which I'm trying to add a subwoofer to using the subwoofer RCA output. I'm hoping to design and build a sub at a later time, but for now have an Onkyo powered unit.

The problem I'm having is that the subwoofer will only come out of standby with the soundbar volume up fairly high. And when the sub turns on, it's very quiet even with the gain maxed out. The sub does fine if plugged into my phone through a 3.5mm to RCA cable.

I'm assuming the soundbar's output signal is low.

Anyone have any ideas how I could increase the output?

Would a MiniDSP do it? I'd be interested in one for future use.

Appreciate any help!
David


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[Zero D]

Hi, could you feed the input/s to the soundbar also to the sub input's ? Thereby bypassing the soundbars sub feed. I'm presuming the sub has it's own amp & LPF !

 

[BmoreBirds]

Thanks for the response.

The sub is powered but no LPF. Also wouldn't have volume control.


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[Zero D]

I see. Then i suggest that you buy a simple cheap preamp/mixer to feed the sub from the soundbar. Doesn't need to be new, or with lots of inputs. Or, if you can & would like, build one if you know how.

 

[BmoreBirds]

Anyone know if a mini DSP would boost the signal? Or would it essentially be pass through?


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[hollowboy]

Would a MiniDSP do it? I'd be interested in one for future use.

Yes, within limits. With the MiniDSP plugin I use (2-way stereo), you can apply boost in the eq window. For example, you can set it to give a shelf boost of +16dB below 150Hz.

It may not be the best tool for the job, but being cheap, and good "for future use", you won't lose much by trying it.

 

[BmoreBirds]

Yes, within limits. With the MiniDSP plugin I use (2-way stereo), you can apply boost in the eq window. For example, you can set it to give a shelf boost of +16dB below 150Hz.



It may not be the best tool for the job, but being cheap, and good "for future use", you won't lose much by trying it.

Thanks, very helpful!


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[Rik_bS]

MiniDSP can boost with EQ, but I don't believe it can output higher than 0.9v RMS, which is on par with phone headphone output

 

[BmoreBirds]

I ended up ordering a 2x4 HD. Hopefully it'll do what I need and much more!


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[chris661]

If the soundbar's output is low, then yeah, boosting with MiniDSP will be fine. You'll only hit problems if the soundbar has lots of output which might cause the MiniDSP to clip it's outputs after boosting.

Chris

 

[BmoreBirds]

The MiniDSP HD easily solved my issue. It has many ways to increase the level even without using EQ.

Thanks for all the replies!


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