# I must be doing something wrong, but I don't know what



## RobertR (Jan 23, 2007)

I'm read the documention several times, and have taken many measurements. I'm using the RS meter, set to C weighting. I get a plausible response curve down to 20 Hz, but then the curve becomes RULER flat down to 2 Hz! That can't be right. Also, when I check the "C weighting" box, the curve rolls upward steeply, as if the program is compensating for a nonexistent C curve. Any help would be greatly appreciated.


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## brucek (Apr 11, 2006)

REW is designed to flatten the meter compensation when it's below the lowest frequency of the calibration file or C-Weight calibration around 5Hz (if memory serves). Continuing any lower and its assured the measured signal will be in the noise and serve no purpose other than to confuse users who would think the compensated rising signal was valid. It won't be since subs don't output that low.

Simply ignore anything below 10hz with REW...

brucek


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## RobertR (Jan 23, 2007)

I appreciate the info. I'm still having trouble believing the curve I'm getting. Less than .5 dB variation from 10 Hz to 120 Hz.


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## brucek (Apr 11, 2006)

Show us.... with a vertical scale = 45dB-105dB and horizontal scale = 10Hz-200Hz.......

brucek


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## RobertR (Jan 23, 2007)

Here it is...


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## brucek (Apr 11, 2006)

Yeah, well I can tell you that's not a measure of any speaker, so we have to find out what the problems is...

Let's start with the soundcard calibration. 
Did you do a soundcard calibration and create a soundcard cal file (by using a cable short on the right channel line-out to line-in of the soundcard), and then save that file. The left channel was left open when doing this and not used now or at any time.. After the file was saved, you removed the short? You also never selected the 'Use Left Channel as reference' checkbox?

brucek


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## RobertR (Jan 23, 2007)

brucek said:


> Yeah, well I can tell you that's not a measure of any speaker, so we have to find out what the problems is...
> 
> Let's start with the soundcard calibration.
> Did you do a soundcard calibration and create a soundcard cal file (by using a cable short on the right channel line-out to line-in of the soundcard), and then save that file. The left channel was left open when doing this and not used now or at any time.. After the file was saved, you removed the short? You also never selected the 'Use Left Channel as reference' checkbox?
> ...


Yes, that was the procedure I followed. I got quite a good curve for the sound card, and saved the calibration curve.


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## RobertR (Jan 23, 2007)

Wait, on this page:
http://www.hometheatershack.com/roomeq/wizardhelp/help_en-GB/html/gettingstarted.html#top
It shows the loopback connection being made on the LEFT channel.


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## brucek (Apr 11, 2006)

> It shows the loopback connection being made on the LEFT channel.


That says _optional_ loopback. It is only used if you don't employ the soundcard cal file method. The Left channel is only looped back when you select the "Use Left Channel as calibration reference" method of calibrating the soundcard. I don't recommend it.

OK, I'll assume you removed right channel loopback and then connected the right channel line out to the receiver and then connected a Radio Shack meter to the right channel line in, and ran the Check Levels routine?

brucek


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## RobertR (Jan 23, 2007)

brucek said:


> I'll assume you removed right channel loopback and then connected the right channel line out to the receiver and then connected a Radio Shack meter to the right channel line in, and ran the Check Levels routine?
> 
> brucek


Yes, that's what I did. I connected to an aux input on the prepro. I set the RS meter to slow, with C weighting. I'll rerun the sound card calibration using the right channel...


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## brucek (Apr 11, 2006)

OK, after that I'll be interested for you to run the Check Levels routine. If that works, then try the Check Levels routine with RS meter shut off. If it still works, then you probably have a 'monitor' mode turned on in the soundcard, which is essentially an internal loopback from line-out to line-in.

brucek


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## RobertR (Jan 23, 2007)

brucek said:


> OK, after that I'll be interested for you to run the Check Levels routine. If that works, then try the Check Levels routine with RS meter shut off. If it still works, then you probably have a 'monitor' mode turned on in the soundcard, which is essentially an internal loopback from line-out to line-in.
> 
> brucek


I'll try that when I get home. I did look everywhere I could think of in the sound options to see where there might be a "monitor" mode, but I couldn't find anything. The sound is built-in to the motherboard. Where might a "monitor" mode be?


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## brucek (Apr 11, 2006)

> Where might a "monitor" mode be?


You would look in the soundcard application software from the control panel. It can go by any number of goofy names, but the result is the same. It ends up turning on the line-in of the playback mixer. If you are using XP, start REW and then take a look at Windows Mixer playback properties to see if line-in is enabled. It should only be enabled in the record mixer and not the playback mixer.

brucek


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## RobertR (Jan 23, 2007)

brucek said:


> You would look in the soundcard application software from the control panel. It can go by any number of goofy names, but the result is the same. It ends up turning on the line-in of the playback mixer. If you are using XP, start REW and then take a look at Windows Mixer playback properties to see if line-in is enabled. It should only be enabled in the record mixer and not the playback mixer.
> 
> brucek


Thanks Bruce, I'll do that. Your help is very much appreciated.


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## RobertR (Jan 23, 2007)

Well, I'm extremely frustrated. I cannot get the computer to sense the RS meter. I cannot check the "line input" box in the recorder mixer control. I'll try another computer...


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## brucek (Apr 11, 2006)

> I cannot check the "line input" box in the recorder mixer control.


You may need to reload the soundcard driver....

brucek


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## RobertR (Jan 23, 2007)

I finally resorted to trying another computer. It worked! I got a real curve. I'll wait to get the mains and the surrounds set up properly before I work on it some more. Thanks Bruce.


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## RobertR (Jan 23, 2007)

I went ahead and did a sub-only curve, with the filters and correction. Comments, suggestions?


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## Ricci (May 23, 2007)

Robert,
What sub is this? Unless it's very powerful I wouldn't worry about graphing the stuff below 15hz and especially 10hz, or be boosting by that much at at 20hz (looks like 15db:time-out! Also cut the top of the graph at 200hz. Also why eq above 120hz? The 58hz boost is excessive and why not mess with the 47hz notch?

Your un eq'd response does not look all that bad except for the 45-55hz null. Maybe you can move the sub around and try to even that out as it's probably due to you room placement.


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## RobertR (Jan 23, 2007)

Ricci said:


> Robert,
> What sub is this? Unless it's very powerful I wouldn't worry about graphing the stuff below 15hz and especially 10hz, or be boosting by that much at at 20hz (looks like 15db:time-out! Also cut the top of the graph at 200hz. Also why eq above 120hz? The 58hz boost is excessive and why not mess with the 47hz notch?
> 
> Your un eq'd response does not look all that bad except for the 45-55hz null. Maybe you can move the sub around and try to even that out as it's probably due to you room placement.


The EQs are inverted responses, so you're actually seeing cuts, not boosts. This is an IB sub (8 15 inch drivers), so the location is fixed.


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## brucek (Apr 11, 2006)

> Comments, suggestions?


It doesn't look as though you clicked the Optimize PK Gain & Q button after you assigned your filters. That's important.

You have some rather sharp dips that don't appear to be room modes. I wonder if there is some cancellation occuring between the multiple drivers. Maybe ensure the phasing is correct.

Measure from 0-200Hz and use a 10Hz-200hz horizontal graph axis. be sure your mains are off and the crossover engaged for the IB. Set the appropriate cutoff on REW.

Don't filter above the crossover.

brucek


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## Ricci (May 23, 2007)

Well I had this all wrong! I thought that you were boosting and that the dotted line was pre EQ:duh:! Sorry.


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## brucek (Apr 11, 2006)

> I thought that you were boosting


Common error Josh. The "Invert filter responses" checkbox at the bottom of the REW chart inverts the filters to allow you to more easily match the filters manually to the peak or dip. It's harder to do if the filter is flipped to its normal orientation.

brucek


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## RobertR (Jan 23, 2007)

> You have some rather sharp dips that don't appear to be room modes. I wonder if there is some cancellation occuring between the multiple drivers. Maybe ensure the phasing is correct.


Hmmm, I wired the drivers according to this diagram:










There are two panels with 4 drivers each. I might have wired them as the mirror image of each other instead of exactly the same. I don't know if that would make a difference.

Edit: The more I think about it, the more I think you've hit on something, Bruce. Those dips (and the 58 Hz hump) coincide so closely with the dimensions of the room, that I think the panels are out of phase. I'll try changing it tonight.


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## RobertR (Jan 23, 2007)

Well, I checked the phase of the sub and it's ok. How else can I address the dips in the FR? This is really bothering me.


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## brucek (Apr 11, 2006)

You have two panels. Have you tried to take a response of just one panel at a time? 

It may be that the two panels are cancelling each other somewhat (especially if they're not co-located). It just seems as though the plot has some very sharp dips that look like severe cancellations.

I assume your graph was measured at the listening position. Have you tried a near field of either panel to get an assurance that eliminating the room offers a good response?

brucek


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## thewire (Jun 28, 2007)

Here is a map based on what I have learned in my room that I wrote on your graph. It is difficult to know what looks best without trying to move some seats or adding something with absorption somewhere. :yes:


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## RobertR (Jan 23, 2007)

brucek said:


> You have two panels. Have you tried to take a response of just one panel at a time?
> 
> It may be that the two panels are cancelling each other somewhat (especially if they're not co-located). It just seems as though the plot has some very sharp dips that look like severe cancellations.
> 
> ...


Excellent ideas, Steven and Bruce, thanks very much. I'll try them.


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## RobertR (Jan 23, 2007)

Well, I took a measurement with just one panel, and it was essentially identical to the measurement with two panels. I then took a near field measurement as Bruce suggested, and the big 45 Hz dip and the 60 Hz bump went away. It's not perfectly flat, but it looks much better than the measurement at the listening position. Looks like the problem is the room...how to fix?


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## RobertR (Jan 23, 2007)

Ok, I think I solved the problem. My front L/Rs are very large and known for their deep bass response (VMPS). I set the front crossover to 40 Hz, the sub crossover to 60 Hz, and set the sub phase to 180 degrees. This is what I got:











It won't be "pure" IB bass, but I was planning to set the crossover at 60 Hz anyway...


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## brucek (Apr 11, 2006)

Note: After you assign filters with REW, you must click the Optimize PK Gain & Q button (it doesn't look like you've done that).

Tip: On the EQ Filters popup, you can sort filters from low to high with the sort button.



> Ok, I think I solved the problem


I would say your mains are a bit high in SPL level with respect to the IB. Bring them down to a lower level and be sure they still _mask_ the 45Hz-60Hz problem. The rest seems equalizable though.
This is an unfortunate problem with IB's - they can't be moved to repair the low frequency response.

brucek


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## thewire (Jun 28, 2007)

RobertR said:


> I set the front crossover to 40 Hz


This seems to happen when I try to help.


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## RobertR (Jan 23, 2007)

When I have more time, I'll tweak it quite a bit more. I'm relieved that I found a solution, even though it's not ideal.


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## RobertR (Jan 23, 2007)

thewire said:


> This seems to happen when I try to help.


It's appreciated, Steve, but I wanted to see if there was a quick solution instead of moving seats, adding room treatments, etc.


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## Ricci (May 23, 2007)

Rob,
How capable are your mains? Also what amp/s is driving your IB and what drivers are you using?


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## RobertR (Jan 23, 2007)

Ricci said:


> Rob,
> How capable are your mains? Also what amp/s is driving your IB and what drivers are you using?


Josh,
VMPS specs the FF1s at -3dB at 14 Hz:

http://www.savantaudio.com/ff1s.html

I don't know if they actually go that low, but Anthony Cordsman's review in the old Audio magazine raved about the extremely deep bass response, which I've also experienced. I'm using eight RLP15s connected to a Behringer 2500 for the sub.


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