Using Room EQ Wizard (REW) to measure FR

[StimpsonJCat]

forsberg21 & I have decided to try and take it to the next level in our audio obsession.

You can use REW to measure and plot your in room frequency response for any speaker. You can also do this with your mains & sub together to see how they work with each other.

I've just started this and have some graphs posted in my gallery.

I'm creating this thread to discuss REW (setup, graphs, tweaks, etc..)

Please join in on the conversation if you have used REW or if you are interested in setting this up for measuring your systems FR.

[StimpsonJCat]

I'm not sure what happened, but I'm getting good at typos (the title of this thread has one). Hopefully Big Daddy or someone can fix it.

Anyways I thought I'd post my latest graph:

[bluseminole]

Originally Posted by StimpsonJCat

Does your sound card have a line in (not mic in)? If so, it should work fine. To calibrate the sound card you need to run a loopback rca between the line in & line out (with the correct adapters). Also, make sure you have them plugged into the red (Right) rca connection on the adapter if your choose to use the Right channel in REW or white (Left) if you choose to use the Left Channel. Don't connect to the AVR or SPL meter (or mic) yet. If you take a screenshot of the main REW screen I can look for possible issues. You should try to choose your soundcard in the drop downs for line in and line out instead of the defaults. Also make sure your sound card is setup for the same sampling rate picked on the main REW screen and turn off any sound card enhancements.

Loopback was setup wrong...whoops! Getting some interesting readings now, definitely had my sub running too hot. Cutting back on that now. Significant dip between 40 and 50 Hz. Things get wacky around 2k...is that a limitation of the SPL meter or do I have big big issues with high frequency? I don't have any wall treatments, so it's a possibility.

Here's the graph with my sub scaled back (btw, this is system response, not just the sub):
EQ graph.jpg

[StimpsonJCat]

Originally Posted by bluseminole

Loopback was setup wrong...whoops! Getting some interesting readings now, definitely had my sub running too hot. Cutting back on that now. Significant dip between 40 and 50 Hz. Things get wacky around 2k...is that a limitation of the SPL meter or do I have big big issues with high frequency? I don't have any wall treatments, so it's a possibility.

I haven't run it with my Mains + Sub yet. So, I'm not sure on the higher frequency response. You might want to post it on Home Theater Shack and see what they think. Can you zoom in on the lower frequencies? There is a button in the upper right corner that lets you set the x & y axis limits. Set them like mine. Then we can see better what is happening down low.

Have you tried finding the peaks with REW and seeing what EQ filters it creates? If you could get rid of that null with placement I think an external EQ would really help smooth out your FR.
It would be interesting to see how different sub placements affect that null.

[Dase]

Originally Posted by StimpsonJCat

forsberg21 & I have decided to try and take it to the next level in our audio obsession.

You buying EQ's? Or just graphing room response?

[bluseminole]

Here's the sub graph:
Sub eq graph.jpg

I haven't messed around with the filter settings yet....I was pretty proud that I was able to even get the graph to work! "Baby steps....baby steps.."

I'll take a stab at them in the next few days though, I promise.

EDIT: BTW, placement of the sub is final. I can't move it....really....I can't. Check out my gallery, you'll see what I mean. The room is just awful, and the sub is quite big.

EDIT #2: Subwoofer to main speaker crossover was set at 80Hz

EDIT #3: I replaced the graph with one that tested the sub by itself. The dotted line represents my first foray into the Parametric EQ settings.

[bluseminole]

Originally Posted by -dase-

You buying EQ's? Or just graphing room response?

Just graphing, using the REW software from Home Theater Shack and an SPL meter. The idea is to reveal nulls and peaks in the room. The software provides filter settings for you to use if you happen to have an EQ. While placement can alleviate nulls, adjusting peaks pretty much requires an EQ.

[sterryo]

EDIT: BTW, placement of the sub is final. I can't move it....really....I can't. Check out my gallery, you'll see what I mean. The room is just awful, and the sub is quite big.

looked at your gallery photos and I don't quite understand why you have no other placement capabilities?
Subs don't require being in the front, behind the seating or next to seating is recommended by Hsu Research.... along the back wall is good also.

I have a pair of a2-300 mid wall on side of theater

[bluseminole]

Originally Posted by sterryo

looked at your gallery photos and I don't quite understand why you have no other placement capabilities?
Subs don't require being in the front, behind the seating or next to seating is recommended by Hsu Research.... along the back wall is good also.

I have a pair of a2-300 mid wall on side of theater

No open wall space! Where would you suggest I try it? There's not enough room behind the recliner and I can't put it in front of the right speaker along that wall without interfering with that speaker. If there's something I've missed, I'm all ears!

BTW, nice BR player!

[Fors*]

Originally Posted by bluseminole

Just graphing, using the REW software from Home Theater Shack and an SPL meter. The idea is to reveal nulls and peaks in the room. The software provides filter settings for you to use if you happen to have an EQ. While placement can alleviate nulls, adjusting peaks pretty much requires an EQ.

Yep, this is what I plan to do. I have an order from monoprice with my necessary cables and adaptors coming today and tomorrow. Apparently I still need to tweak the software before I can run the test. Luckily I have been talking to StimpsonJCat, and he has graciously walked me thru the procedure up to this point. Hopefully I will have everything in and set-up by this weekend. I am really looking forward to giving this whirl so I can post my results and listen to any suggestions to tweak my sub's bass response as well.

By the way, Stimpy ( ) this is a great thread idea!

[StimpsonJCat]

Originally Posted by -dase-

You buying EQ's? Or just graphing room response?

Even before running REW I new that Audyssey was boosting in the lower frequencies so I bought an eQ.2 (2 band sub EQ). I was able to get an alright result by ear, but after using REW to see the FR I was able to do a much better job and the difference in SQ is huge. So, yes I am using an EQ. REW is free. If you already have a SPL meter and a PC with the right sound card it is a very inexpensive way to at least see what is happening with your in room FR.

[StimpsonJCat]

Originally Posted by bluseminole

Here's the sub graph:

I haven't messed around with the filter settings yet....I was pretty proud that I was able to even get the graph to work! "Baby steps....baby steps.."

I'll take a stab at them in the next few days though, I promise.

EDIT: BTW, placement of the sub is final. I can't move it....really....I can't. Check out my gallery, you'll see what I mean. The room is just awful, and the sub is quite big.

EDIT #2: Subwoofer to main speaker crossover was set at 80Hz

EDIT #3: I replaced the graph with one that tested the sub by itself. The dotted line represents my first foray into the Parametric EQ settings.

First off good job getting things up and running with REW. It can be a pain to setup, but once you have it working it won't be hard to take new measurements. Thanks for contributing to this thread.

How many filters did REW setup? I would discount any with only a few dbs (<4) This will at least give you an idea of how many EQ bands it would take to get that dotted line FR.

Bummer about the placement issue. I'm pretty much stuck with mine as well. But, if you don't get rid of that null with placement you might just have to live with it. You could try to boost it with an EQ band, but often it won't make a difference. And even if it does you will lose head room in the process.

I want to measure with the Mains + Sub next and play with the crossover. I'm not sure when I will get to this, but I would like to see how it looks. I also want to play with the other features of REW.

[StimpsonJCat]

Originally Posted by forsberg21

Yep, this is what I plan to do. I have an order from monoprice with my necessary cables and adaptors coming today and tomorrow. Apparently I still need to tweak the software before I can run the test. Luckily I have been talking to StimpsonJCat, and he has graciously walked me thru the procedure up to this point. Hopefully I will have everything in and set-up by this weekend. I am really looking forward to giving this whirl so I can post my results and listen to any suggestions to tweak my sub's bass response as well.

By the way, Stimpy ( ) this is a great thread idea!

I hope we can get your REW setup up and running soon. I'm really interested in seeing what the Pioneer's room EQ is doing. Overall I'm very happy with what Audyssey does with my sound aside from the stange subsonic boost.

[sterryo]

Originally Posted by bluseminole

No open wall space! Where would you suggest I try it? There's not enough room behind the recliner and I can't put it in front of the right speaker along that wall without interfering with that speaker. If there's something I've missed, I'm all ears!

BTW, nice BR player!

since the pictures only show view from front i can only guess at the rest, perhaps next to recliner instead of behind it?
and thx for the compliment, I need to update my theater pics as I have really changed things down there, but will wait till i finish my sub risers and i also decided to get rid of my fugly home built stand and i am to build a cabinet into the wall underneath the steps

[sterryo]

Originally Posted by StimpsonJCat

I hope we can get your REW setup up and running soon. I'm really interested in seeing what the Pioneer's room EQ is doing. Overall I'm very happy with what Audyssey does with my sound aside from the stange subsonic boost.

REW was tricky to set up for me, i tried using an older Acer notebook running XP first and got no where (i think incompatible USB drivers), next i tried my wifes HP with Vista and again got further but couldn't calibrate the soundcard correctly, finally got it work using my netbook (8.9" screen) in order to see the whole screen with the needed buttons i had to make the font size -75% of normal.... it was tiny on that little screen but it worked an i was able to place filters into my BFD. after playing around with placement i found that Audyssey could get excellent results on it's own ( only needed one small tweak using only one filter) so i removed the BFD from the mix... have fun with REW, it can be a very helpful tool, but as with all things HT make sure you have ample free time...

[StimpsonJCat]

Originally Posted by sterryo

REW was tricky to set up for me, i tried using an older Acer notebook running XP first and got no where (i think incompatible USB drivers), next i tried my wifes HP with Vista and again got further but couldn't calibrate the soundcard correctly, finally got it work using my netbook (8.9" screen) in order to see the whole screen with the needed buttons i had to make the font size -75% of normal.... it was tiny on that little screen but it worked an i was able to place filters into my BFD. after playing around with placement i found that Audyssey could get excellent results on it's own ( only needed one small tweak using only one filter) so i removed the BFD from the mix... have fun with REW, it can be a very helpful tool, but as with all things HT make sure you have ample free time...

I hear you. I spent a ton of time this past weekend. I was just lucky that my wife was out of town. She really loves the end result, but is not much for the process. I enjoy tweaking though so I don't mind it taking so much of my time.

[bluseminole]

Originally Posted by sterryo

since the pictures only show view from front i can only guess at the rest, perhaps next to recliner instead of behind it?
and thx for the compliment, I need to update my theater pics as I have really changed things down there, but will wait till i finish my sub risers and i also decided to get rid of my fugly home built stand and i am to build a cabinet into the wall underneath the steps

Whoops, my bad! I have uploaded new pics of my setup since it's changed, but I forgot to put them in my gallery....I simply put them in a thread!

[bluseminole]

Originally Posted by StimpsonJCat

First off good job getting things up and running with REW. It can be a pain to setup, but once you have it working it won't be hard to take new measurements. Thanks for contributing to this thread.

How many filters did REW setup? I would discount any with only a few dbs (<4) This will at least give you an idea of how many EQ bands it would take to get that dotted line FR.

Bummer about the placement issue. I'm pretty much stuck with mine as well. But, if you don't get rid of that null with placement you might just have to live with it. You could try to boost it with an EQ band, but often it won't make a difference. And even if it does you will lose head room in the process.

I want to measure with the Mains + Sub next and play with the crossover. I'm not sure when I will get to this, but I would like to see how it looks. I also want to play with the other features of REW.

Here's the graph of the sub response (solid line) and the predicted effect of the EQ filters automated by REW (dotted line) plotted against the target level (solid blue line, 77.1 dB....I guess I ran the test a tad hot ):

Sub Eq graph with auto filters.jpg

Here's my second shot at adding some manual filters. I went on the assumption that my limit will be 12 bands of EQ, because if I were to purchase something, it would likely be the Behringer DSP1124:

Sub Eq graph with manual filters.jpg

[bluseminole]

Originally Posted by sterryo

REW was tricky to set up for me, i tried using an older Acer notebook running XP first and got no where (i think incompatible USB drivers), next i tried my wifes HP with Vista and again got further but couldn't calibrate the soundcard correctly, finally got it work using my netbook (8.9" screen) in order to see the whole screen with the needed buttons i had to make the font size -75% of normal.... it was tiny on that little screen but it worked an i was able to place filters into my BFD. after playing around with placement i found that Audyssey could get excellent results on it's own ( only needed one small tweak using only one filter) so i removed the BFD from the mix... have fun with REW, it can be a very helpful tool, but as with all things HT make sure you have ample free time...

So if you have no use for that BFD....are you looking for somebody to take it off your hands?

[StimpsonJCat]

Originally Posted by bluseminole

Here's the graph of the sub response (solid line) and the predicted effect of the EQ filters automated by REW (dotted line) plotted against the target level (solid blue line, 77.1 dB....I guess I ran the test a tad hot ):

Here's my second shot at adding some manual filters. I went on the assumption that my limit will be 12 bands of EQ, because if I were to purchase something, it would likely be the Behringer DSP1124:

I would be careful using a EQ filter to boost. If it really does boost you will lose headroom, but often you won't be able to actually boost a null.

I doubt you would ever need 12 bands. Take a look at this great post from HTS.

He shows how to reduce the number of filters needed (and which are not even really needed). I've read through a few peoples threads and they start out using a lot of bands, but in the end they get the best sound with only a few. Also he talks about setting up the target curve for the best starting point of adding filters.

Also, take a look at his discussion of house curves. I used a house curve, but with limited EQ bands I didn't try for the hard-knee house curve he talks about. It is an interesting read.