Please helpa noob with some graphs

**tjbierman** · **10-18-08, 11:35 AM**

Hey guys,
I am taking my first stab at REW for placing my two MFW-15 subs in my dedicated home theater. I think I have REW set properly. I have the RS 33-2055 meter connected to my laptop via the u-control external sound card. I am then going straight to my subs (no avr) for placement. So far I have tried (first graph) co-locating them in a corner and (second graph) separating them up front by my mains. Here are the two graphs. What suggestions do you have on which placement to go/tweak with? Also, I have a BFD which I haven't put in line yet. Which placement do you think the BFD will help the most? I'm sure I have made errors in this post, so let me know if I can change graph displays or take different measurements, etc.

Thanks for your help and this great resource.

Todd

**brucek** · **10-18-08, 12:45 PM**

There's not an enormous difference between the graphs. They both appear well behaved with some peaking around 35Hz that can be brought down a bit.

It's a better idea to feed the AVR (without mains on) and use the crossover you intend to use to get a better picture. Then add the mains to see how they integrate around the crossover.

brucek

**tjbierman** · **10-18-08, 01:29 PM**

Bruce, Thanks for the quick reply.

Should I be concerned with the dips around 50hz? If so, what are my options on dips? Further placement experiment or bass traps? Or are the dips not too bad.

I will take more measurements with my AVR. A quick question on that process. Do I input just one channel into the avr? Also, when I want to check with mains, do I set to "all channels"?

Thanks again.

Todd

**brucek** · **10-18-08, 01:43 PM**

Quote:

Should I be concerned with the dips around 50hz?

Well, I see it more as a peak below 50Hz than a dip. If the target was raised to 75dB for the 50Hz+ bandwidth, then the lower section is a peak.

Quote:

Do I input just one channel into the avr?

Most people feed a Y-splitter into the left and right channel. This allows you to test both mains when it's time...

Quote:

when I want to check with mains, do I set to "all channels"?

Use "Stereo" mode for all REW testing. When you don't want the mains, simply disconnect them (with the power off).

brucek

**Wayne A. Pflughaupt** · **10-18-08, 02:37 PM**

Notice the output penalty with the subs separated: At almost anyplace you look below ~70 Hz, output is down a few to several dB. Of course, of your subs are large and powerful enough for your room, that might not be anything to worry about (but if they aren't, it is).

Regards,
Wayne

**tjbierman** · **10-18-08, 03:07 PM**

Quote:

brucek wrote:

Well, I see it more as a peak below 50Hz than a dip. If the target was raised to 75dB for the 50Hz+ bandwidth, then the lower section is a peak.

So it is possible I can use the BFD to lower the peaks below 50Hz? You don't think the peaks are too extreme? I would like to keep them co-located as it works better for decor, if nothing else. I will get a Y-splitter and re-test.

Thanks again, this is a super useful forum. I can't wait to dip into my BFD and smooth this curve out.

Todd

**brucek** · **10-18-08, 03:30 PM**

Quote:

So it is possible I can use the BFD to lower the peaks below 50Hz?

Absolutely....... no problem...

Quote:

I would like to keep them co-located as it works better for decor, if nothing else.

Co-locating is the easiest method of using two subs. Few people are lucky enough to enjoy a non co-located second sub reinforcing the first at exactly the desired frequencies of dips and peaks. Co-locating basically creates a more powerful single sub...

brucek

Advertisement