Another new REW user

**bcrawfo2** · **07-07-06, 09:23 AM**

First...I'd like to say thanks. This is an amazing tool. I'm really learning a lot, both about audio and general and about my room/equipment interaction.

Here is my room graph.
I thought I had a pretty good sub location, but that drop at 55hz really concerns me. It doesn't seem prudent to boost that much. Playing in REW, I can get it pretty close...but it would max out the gain for a filter. I guess I should try a few different sub locations and measure them (current location was picked by ear).
How much can I actually boost safely?
Oh...almost forgot. I'm sure it's not a crossover. I'm crossing over at 80 hz in this trace. I'm going to play with that and probably move down to 60. I have B&W Nautilus 803s as my mains...they should be ok down to that point. Also...the sub is an Velodyne HGS-18.
graph.jpg

Thanks
Scott

**brucek** · **07-07-06, 11:17 AM**

Generally we recommend setting the axis limits from 45dB to 105dB and 15Hz to 200Hz with a sweep setting from 20hz to 200Hz as shown in this FAQ. Also set your Pre-Impulse Response Window as shown in that thread. It will allow us all to be comparing the same graph settings..

Also shut off your mains and measure the sub only with the crossover set to its usual setting.

brucek

**bcrawfo2** · **07-07-06, 12:51 PM**

Thanks. I figured that was coming as I combed the other posts looking at results other users had.
I'm working on new graphs. Also, I'm having problems with measuring impulse response. All the controls are greyed out.
I would think that when you do this sample that it would make a sound...stop...then listen for the decay. Maybe I need to worry about that later.

I hear the capture fading off in the other room. New graph coming soon
Thanks
Scott

**bcrawfo2** · **07-07-06, 01:19 PM**

OK...new graph.
It wouldn't go any wider than 632. I guess that's because the screen on my laptop won't go any higher resolution?
graph4.jpg
Conditions...all but sub off...xover at 80 (willing to try this out)
That reference line is a house curve as suggested in the FAQ:
30 8.0
80 0.0

That's a 15 db drop in the 50s. I think this weekend I'll shuffle the sub around and run some more traces.

**brucek** · **07-07-06, 01:46 PM**

OK, much better. Good job. 632 is fine.

I'm guessing this is the uncorrected, unfiltered response?

Yeah, you have a problem at ~52Hz which corresponds to a room dimension of ~(10.5 to 11.0) feet.

It may respond to gain and then it may not. If it doesn't respond, then don't push it, you'll get nowhere other than to deplete headroom in your sub amp. The only options would be to move the sub or live with it.

Both your mains and sub are beautiful speakers. The BFD will help a lot in making the overall response much smoother.

Once you've added filters to get the best response possible, you can do a sub plus mains response using the same setup and parameters in REW. This will reveal whether the mains integrate with the sub around the crossover without creating problems in the response.

brucek

**bcrawfo2** · **07-07-06, 02:02 PM**

Thanks for getting me on the straight and narrow Bruce.
I was going to track down a room mode calculator and figure it out. I'll go download the one in the downloads section later and play with it. I get the basics..kinda. My room is about 15 wide by about 24 long with 8 foot ceilings. I have a few openings (big doorways) and not sure how they play in. So it might not be room mode, based on your guess dimension. This is not the theater's final resting place, so I'll probably just get it as good as I can for now. Need to finish a kitchen floor and then I'll start on a basement theater room from the ground up.

I had heard the comments about dynamic range but it just wasn't clicking. Your comment made it go CLICK. I get it now...if boosting frequencies doesn't show any result on the graphs...then it's a room problem...so your amp is working harder and not providing any more perceived volume. I get it.

So I'll bost away as long as I'm getting positive results in the graph.

I'm gonna move stuff around this weekend and see if I can get a less drastic curve (and just learn more about REW).
My BFD will be here late next week, so I'll just have to work in theory until then.

Did you see my question about impulse response? I'm still not able to figure that out.

Scott

**brucek** · **07-07-06, 02:11 PM**

Quote:

I get it now...if boosting frequencies doesn't show any result on the graphs...then it's a room problem...so your amp is working harder and not providing any more perceived volume. I get it.

Yep, you got it.

Quote:

Did you see my question about impulse response? I'm still not able to figure that out.

Ah, sorry, I meant to answer that.
You must first take a measurement and then all the controls will un-grey themselves. Then make your adjustments and go back and see the results. Same for waterfall etc. You must first take a measurement.

Edit: You're not the first one to ask that question. We'll have to talk to John M about that and maybe he can fashion a pop-up message regarding this in REW.

brucek

**Wayne A. Pflughaupt** · **07-07-06, 03:52 PM**

Hi Scott,

Quote:

I thought I had a pretty good sub location, but that drop at 55hz really concerns me. How much can I actually boost safely?

Probably more than you think. It all gets down to how much headroom you have available. I’m guessing with that sub, coupled with the size of your room, that it’s really loafing. I’ll be surprised if you have it adjusted higher than 9:00 or so, right? If it’s below say, 11:00 or so you should have no problem dialing in the boost you need - assuming as brucek mentioned, that it's not a null. I'll be surprised if it is, seeing how broad it is.

Quote:

I'm crossing over at 80 hz in this trace. I'm going to play with that and probably move down to 60.

Assuming your 55 Hz problem is actually a room problem, moving the crossover that low will put it above the sub’s domain, which means you won’t be able to equalize it.

Regards,
Wayne

**bcrawfo2** · **07-18-06, 04:22 PM**

OK...I'm back. Thanks everyone for getting me thinking correctly.
My BFD finally got here. Everyone reading...just pay the $ and get it quickly. I bought on off of ebay (dunno why now) and it took forever to get hear.
So...here is my "in theory" graph.
graph5.jpg
My wife is taking a nap, so I can't do another capture.
Will post another graph either later tonight...or more likely tomorrow morning.
I'll be very excited if I get near this response.
I can see the draw of doing Midi configuration. It took me a few tries to figure it out. I would assume that with frequent changes it could get pretty frustrating.

Thanks...will update soon.
Scott

**brucek** · **07-18-06, 06:33 PM**

Quote:

So...here is my "in theory" graph

Shouldn't your target look more like this:

graph.jpg

brucek

**bcrawfo2** · **07-18-06, 07:07 PM**

OK...you're right. I looked after I posted...I reloaded the house curve a few times. Finally I realized that I hadn't told REW that this channel was a subwoofer. That put the correct curve in.
I need to work a little on that small peak at 75.
Thanks for keeping my honest Bruce.
graph6.jpg

**bcrawfo2** · **07-19-06, 08:44 PM**

OK...here's what I ended up with.
I gotta try some more on that 50s area.
I guess try a few more passes on my current filters...I used all 12

I guess I should've used fewer and saved some for cleanup.
Maybe I'll try a little more and then start over clean.
Is there a way to get the text values of what filters are in REW so I can post here?after-7-18-detail.jpg

**Wayne A. Pflughaupt** · **07-19-06, 09:33 PM**

What does your base graph look like? It seldom takes that many filters.

Regards,
Wayne A. Pflughaupt

**bcrawfo2** · **07-28-06, 06:37 PM**

Before you read this...I take it all back. I made a mistake and was measuring where I thought it was ok...but it wasn't. Skip this post....but read further on in this thread...then...come back and look at these measurements.
Lesson #1....measure exactly where you sit. It's not "close enough".

Scott

Hi everyone...sorry it took me so long for another pass (I'm sure y'all were on the edge of your seats...kidding).
I started over and got down to 6 filters and came up with this.
sub-alone-7-28-06.jpg
I can live with this. Might tweak a little more.
Unfortunately, this created a sound that was quite annoying. Bad enough that I turned down my sub and I actually felt a little relief when I bypassed the BFD.
So...my wife is out of town tonight, so I was able to do some longer term playing.
I went ahead and ran a full range scan in the lower range and got this (this is BFD w/ 6 filters and all speakers on).
full-range-7-28-06.jpg
No wonder it sounds funky. I probably wasn't bothered by it too much cause my x-over was at 60 pre BFD. Right now I'm at 80.
So...guessing that it was a phase problem, I inverted it and came up with this (again...BFD on with all speakers, x-over at 80).
full-range-rev-phase-7-28-06.jpg

I still have that mid 50s problem (even on my sub alone)...I guess that's a room problem. In my filters...I have 50+3(51.95) +15db, 7.3hz wide. I guess I can try to put one just to the right of that (right at 55) and try to work some more on that dip.
Thoughts?

**brucek** · **07-28-06, 06:56 PM**

Quote:

I have 50+3(51.95) +15db

Too much gain. I would try to never exceed about +5dB gain.......

Why not change your crossover back to 60Hz. What does the sub + mains look like then?

brucek

**bcrawfo2** · **07-28-06, 07:14 PM**

Actually....before anyone spends any more time...kick me a few times for wasting everyone's time.
He bows his head down out of shame. I continued to be unhappy with the sound of my last with filters graph. I leaned down to where I rested my SPL meter (not very far from my ears...in my mind) and heard a totally different sound. So...I dug up my camera tripod and remeasured and came up with a greatly different starting graph.
Lemme work on that...will post shortly.
You can use me as the "really be careful where you measure from dunce hat guy".
Sorry and thanks for your continued help.

**bcrawfo2** · **07-28-06, 08:50 PM**

OK...lets try this again.
Measured from the CORRECT position.
My unfiltered sub only
try-2-sub-alone-7-28-06.jpg
Not too bad...dropped off earlier than I had hoped for the 60hz x-over. I would also expect it to drop off more linearly after the 60hz x-over. Any thoughts here? My mains, center, and rear amps were OFF. I'm wonder if this is NOT helping my full range graphs.
Now...I smoothed out everything but that mid 50s+ stuff, hoping that it was x-over and that the mains would even it out.
try-2-sub-alone-after-7-28-06.jpg

Now, I added the mains and got..
try-2-full-range-7-28-06.jpg
Obviously...we can't live with that 55hz dip.

I reversed polarity and got...
try-2-full-range-rev-phase-7-28-06.jpg
I need to look at that wide 50ish dip. Also...I might run some higher freqs to look at where the mains pick up. I'm just using an old RS analog meter. Reading up on proper mics.

I gotta say....AHHHH...this sounds much better. I can't believe I put up with that sound for a week of casual TV watching.
The moral of the story....measure from where your head is, not where it's easy to put the meter. I know you say this...but from an amateur's mouth...it makes a difference.

Scott

**brucek** · **07-28-06, 09:50 PM**

Quote:

Obviously...we can't live with that 55hz dip.

Probably too narrow to even notice.

Quote:

I'm just using an old RS analog meter.

I'm assuming that you're using the correct calibration file.

----------------------

Why is your REW target showing what looks to me to be an 80Hz crossover rather than the 60Hz your processor is set to?

Why do you not measure to 200Hz?

You've really got to turn on the graph grid lines....

brucek

**bcrawfo2** · **07-29-06, 02:15 PM**

Yes...using the oldRS cal file.
and...yes...I didn't change my house curve to show the 60hz x-over.
I'll take another set of graphs in the next few days.
I didn't go to 200 because I was more concerned with lower freqs...will include that range in my next graphs.
Scott

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