# Getting REW to use the lfe channel



## TEK (Jan 9, 2011)

Hi

I notice that under "Preferences" I can select "use subwoofer to check levels".
When this is selected it seems as if REW is sending all the sound to the LFE channel and the sub's get's the signal.

But when I run measures (clicking on the "Measure" icon and the select "Start measuring") REW uses my main channels.
Is there anything I can do to get REW to run the measure sweep on the LFE channel, so that I can measure my sub's without rewiring everything when I want to measure sub's vs. when I want to measure my mains?


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## Phillips (Aug 12, 2011)

Hi yep either turn of your speakers e.g. Speaker A on the receiver or there might be something in your receiver menu.


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## Wayne A. Pflughaupt (Apr 13, 2006)

What Phillips said. You can also upper- limit the sweep to 100 Hz or whatever frequency you want in the “Measurement” window.

Regards, 
Wayne


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## TEK (Jan 9, 2011)

Hmm, there must be something I'm not getting here.

If REW passes a stereo signal to the receiver (I have a Marantz SR7005), the only sound that will go to the sub is the sound that is sent to the sub because I have my speakers set to small. If I do not have my front speakers set to small - no sound will be sent to the sub's. If I disconnect the speakers then no sound will be sent at all.

I would like REW to send the measurement signal directly to the subwoofer (using the lfe channel) like REW does when I check the levels under preferences and select "use subwoofer to check levels".
But it does not seems like I have an option to make REW only pass the output signal to the subwoofers.

So how should I then measure the subwoofers?


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## willis7469 (Jan 31, 2014)

Unhook your speakers. 


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## TEK (Jan 9, 2011)

If REW send a stereo signal to the receiver, and I unhook the speakers I will - of course - get no sound :innocent:

So, can we stop focusing on deactivating the main speakers and start focusing on how to get the sound to the sub :foottap:

Again, I'm very open to that I might have misunderstood something really simple, but it is NOT related to avoiding the sound coming from the mains - it related to how to get the sweep out of the subwoofer.
Any ideas - except turning off or disconnecting the main speakers (I have already done that) - is very welcome.


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## willis7469 (Jan 31, 2014)

Ok, like the other guys said, you can run the sweep up to say 60 or 80hz. Then at most your mains will only see a half second or so of sweep tone. I just figured out now that you must be connected with the high level inputs(speaker connection) instead of the subwoofer out.(RCA) My earlier suggestion to unhook your speakers took into account you were using the sub out(RCA). My bad. That's how most of us measure subs only, because unhooking the speakers doesn't effect the sub connection. I'm sure that's where we got disconnected (pardon the pun lol) Why else would you get no sound from the subs by unhooking the speakers. (You can still unhook them from the output side of the sub if that's the case) Banana connectors are awesome. The "use subwoofer to check levels" isn't for sweeping. It's for level matching channels or the built in spl meter. 


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## willis7469 (Jan 31, 2014)

REW can't just use the lfe channel because that's coded into a soundtrack independently of the rest of the bass. What your avr sees from REW is just simply frequencies. 


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## willis7469 (Jan 31, 2014)

TEK said:


> If REW send a stereo signal to the receiver, and I unhook the speakers I will - of course - get no sound :innocent:


this is why I assumed the high level inputs. Sorry if that's not the case. 





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## Wayne A. Pflughaupt (Apr 13, 2006)

TEK, What is your connection scheme for getting audio to your system? Are you using an outboard sound card with analog connections to the HT system, or HDMI from your computer?

Regards, 
Wayne


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## TEK (Jan 9, 2011)

Hi


I'm using HDMI out from my HTPC to my receiver. I have a soundcard with anaog out installed in my HTPC and may pass signals from that and out as well.

Rest of my equipment:
Speakers: 2 Wavecor Ardent DIY, 1 B&W HTM1 (To be exhanged), 2 B&W SCM1, 2 B&W SCMS, 2 Rhytmic Audio 15" DIY subs, 1 Aurasound 18" DIY sub
HTPC, Xbox one, TV-tuner box, Marantz SR7005 (receiver), Sony VLP-HW50ES (projector), Thule AV350B (stereo amp for front speakers)
XENYX 502, EMM6, Behringer FBD (currently not used)


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## willis7469 (Jan 31, 2014)

Nice gear. 


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## Wayne A. Pflughaupt (Apr 13, 2006)

TEK said:


> I'm using HDMI out from my HTPC to my receiver. I have a soundcard with anaog out installed in my HTPC and may pass signals from that and out as well.


Thanks for that, but it still doesn’t tell us which way you’re sending signals from REW to your receiver. However, the more I think about it the more I expect it doesn’t matter...




TEK said:


> If REW passes a stereo signal to the receiver…


REW sends a mono signal via analog (not sure about HDMI directly from a computer).




> If I do not have my front speakers set to small - no sound will be sent to the sub's.





> I would like REW to send the measurement signal directly to the subwoofer (using the lfe channel) like REW does when I check the levels under preferences and select "use subwoofer to check levels".
> But it does not seems like I have an option to make REW only pass the output signal to the subwoofers.


With an analog input from REW (and I suspect HDMI as well), the signal is subject to the settings you have in your receiver. If you have the speakers set for small, and if that setting in your particular receiver does not activate the subwoofer, then that’s just the way it is. You’d get the same results from any audio source you had connected, analog or digital. If you want REW to play a signal through the sub you’re going to have to set the receiver with an appropriate setting that activates the sub.

Regards, 
Wayne


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## TEK (Jan 9, 2011)

Thanks Wayne.
Sorry if I was not clear. When I wrote that "I'm using HDMI out from my HTPC to my receiver"
I should have been more precise. What I ment was:
I run the mic signal from the Mic trough a XENYX 502 and into the soundcard of my HTPC.
I run REW on my HTPC, and the REW sound signal is beeing transferred from the HTPC to the receiver trough HDMI.

Based on your input I have found the solution.
1) Set my main speakers to small
2) Set the crossover frequency for the mains as high as possible (250hz)
3) Turn of my external amp (to disable the main speakers)

Then start measuring...
Thanks for your help and input!


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## Todd Anderson (Jul 24, 2009)

If your crossover is set at 80Hz for the mains, go into your AVR and bump the crossover to 120Hz, then run your sweep to 90 or 100Hz...:T that should keep the mains largely out of the picture.


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## smygolf (Jan 18, 2014)

I use Asio4all with Rew.
The only issue i have is that when i change speaker it take a couple of sec for the reciver to sync.

Pc -> nanoAvr -> reciver, hdmi all the way


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