Sub level post house curve

[jaz123]

Folowing the advice of many on this forum I added my first house curve. I used the simple two point curve shown in the REW FAQ section with a 10 dB gain at 30 HZ. I perfomed my system calibration at to 80dB and and moved my target response curve down manually until it was in a place where I could set my filters (mostly cuts) to follow the curve.

My question is this. How should I set the sub level so the blend between my mains an the sub is correct? I understand that the level will need to be adjusted using the gain control on the sub as opposed to my receiver. Is it as easy as setting the mains to the 80dB using some pink noise and setting the sub to 90dB using pink noise also? Or do I need to use REW to set the sub to 90dB at 30Hz?

Any other suggestions -

Thanks

John

[Otto]

Good morning, John.

First, welcome to the Shack. There's lots of good information here.

As to setting main and sub levels, once I get the curve I want (sounds like you're done with that part), I usually get them in the ball park with a quick pink noise test like you suggest. Then, with the mains still on, do the sweep test again. At this point, I usually let it go up to about 200 Hz, to get well beyond the crossover point. That sweep will show you the interaction between mains and sub. If one is much hotter than the other (they should be pretty close anyway from the pink noise level setting test you just did), then adjust as needed. You may decide you need to tweak a little on your filters as well.

There may also be some phase interaction between mains and sub as well. You may recall from the REW/BFD instructions that the BFD's processing will incur about a 1mS group delay. You can set your receiver to add another foot of distance for the sub location to account for that. There may be other phase contributions as well, so you may wish to play around with the distance for your sub to account for that. If you see a big dropout in frequency response at or about the crossover point, it may be phase related. There's more discussion on that topic here.

It can be a lot to digest, but don't worry -- it sounds like you are on the right path!v

[jaz123]

Hi Otto -

Thanks for pointing me in the right direction. I had added the 1 foot to my sub distance based upon some earlier BFD discussions.

The pink noise "calibration" I was referring to was performed through the setup on my Denon 3805 receiver. Should I be adding the 10dB to my sub output level with respect to my mains... IOW mains = 80dB / sub = 90dB?

How would I go about perfoming a sweep in REW with my mains included? My soundcard setup for Sub Eq was dedicated to the sub only. Do I need to split the output and somehow run it back through my receiver? If I do this will I need to rerun the input level setting / calibration setup?


Again thanks to your patience with a newbie


John

[Otto]

Hi John,

jaz123 wrote:

The pink noise "calibration" I was referring to was performed through the setup on my Denon 3805 receiver. Should I be adding the 10dB to my sub output level with respect to my mains... IOW mains = 80dB / sub = 90dB?

How would I go about perfoming a sweep in REW with my mains included? My soundcard setup for Sub Eq was dedicated to the sub only. Do I need to split the output and somehow run it back through my receiver? If I do this will I need to rerun the input level setting / calibration setup?
John

Well, I went back and re-read your original post. I think what's going on is that the first calibration you did is irrelevant now. Now that your curve is done, just recalibrate with the receiver. The receiver is basically going to take care of levels and distances for you if you do it after the BFD setup. I don't think you will need to add that extra foot in the distance if you receiver does the setup either.

As to the full range sweep, REW always just does it for me. I have to turn off my main amp to be able do the sub only sweep. When I turn back on the main amp, I can do the combined sweep. Did you have to disconnect your main, center and surround speakers? In general, I've used REW with analog inputs (left only, actually), and there's no way for my preamp to know that that signal is intended only for the sub. I've never used REW with the digital input on my sound card because we do the soundcard calibration to account for any inaccuracies in the sound card. Do the sweep again and see if you can hear any low frequencies coming out of your mains, center or surrounds at all. You may have limited the sweep to 80 Hz or whatever and it may not be readily apparent that there's anything coming out of the mains. You said "My soundcard setup for Sub Eq was dedicated to the sub only". I'm not sure what that means, but you might have to undo that.

So here's the steps I would do:

1. Forget anything the receiver has done for setup. If it's using any room correction/Audessey/whatever, turn it all off.
2. Do the cals as described in the REW manual. Get your level up to about 75 dB per the RS SPL meter.
3. Load up your house curve and cal files, etc.
4. Sweep and see how it goes.
5. I like to boost up my sub level so that I can apply a lot of cuts. Remember you may need to turn up the sub gain again later, so don't max it out if you don't have the headroom. You can also get some boost from the receiver level settings. I usually boost up enough so that I can hit a target curve of about 80 dB or so.
6. Let it sweep and apply whatever filters until you are happy.
7. Recalibrate mains and sub channels using your receiver or RS SPL meter and pink noise.
8. Sweep with sub and mains.
9. Repeat as necessary.

Bottom line is that there should not be a big drop or hump in output at the crossover point. As to where to apply the boost on your sub if needed, I kind of like to keep everything in the middle. If you have your sub gain turned up high, and your receiver is cutting the sub level by 10 dB, I would try to balance them out -- turn up the receiver sub level to 0 and turn down the sub gain till it's somewhere in the middle.

In the end, you will likely have to twiddle with the receiver's sub level depending on the program material. Even if your receiver or RS SPL meter thinks all levels are correct, sometimes it just doesn't sound right to our human ears.

Sorry that this got kind of rambling, but hey. Too long to proofread, so lemme know if something doesn't make sense.

Have a good day!