# Help with Calibration



## Nick (Oct 28, 2009)

Greetings -- I've read much of the information but would appreciate help with understanding where I'm not getting it. I use the FBQ2496 and the Turtle Beach sound card. I'm sure I'm not optimizing the way I make measurements or the use of the software. I have the EQ connected to a preamp and it is connected to both the 'full range' mains and the sub for 2 channel music listening only. I've seen Wayne's explanation about sound card setup and the photos for Vista, but I haven't seen photos for XP - do they exist?

1. Setting input levels -- I never come close to clipping and rarely see more than a few of the green lights during output. Essentially, I have ignored the input procedure, but have used measurements to 'level match' the speakers with the sub. Do I need to go back and figure out how to set the input? I'm not understanding the instructions on the site on this procedure.

2) After I calibrate the RS SPL meter at 75dbs to match it to the reading on the software, and then test levels for the software, I have to turn down the volume quite a bit due to clipping. I am adjusting the volume manually to get a reading to show up on the graph close to the target curve at 75dbs. I wonder what I'm doing wrong at this point?

3) When I measure, I am able to filter to change the response. I have a bump at 45hz that does not respond at all to any kind of filtering. I thought perhaps the FBQ wasn't working, but when I filter other freqs it does work. Are there any suggestions as to why this might be happening? I think the FBQ is connected properly to EQ both the sub and the mains. Let me know if it would be best to post a before and after graph.

4) I've read the info about 'phase' but I'm not getting what to look for on that realm, or how much I should worry about that at this point.

I know this is pretty remedial, but thank you for any help you can offer.
Nick


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## JohnM (Apr 11, 2006)

The setup (if by that you mean the connections etc) is the same for Vista and XP, if you are referring to the volume mixer settings you can find info on that in the REW help under the "checking levels" topic. Got to run just now, but I'll post on your other questions shortly.


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## JohnM (Apr 11, 2006)

Did you manage to get a soundcard loopback calibration done? That gets most of the levels set to at least the right ballpark.

Re the FBQ and effect of applying filters, it would be worth explaining how you have things connected up. It sounds like you have the FBQ feeding the mains and the sub is driven from the same connection using its own internal crossover?


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## Wayne A. Pflughaupt (Apr 13, 2006)

> 1. Setting input levels -- I never come close to clipping and rarely see more than a few of the green lights during output.


That’s perfectly fine. :T




> 2) After I calibrate the RS SPL meter at 75dbs to match it to the reading on the software, and then test levels for the software, I have to turn down the volume quite a bit due to clipping. I am adjusting the volume manually to get a reading to show up on the graph close to the target curve at 75dbs. I wonder what I'm doing wrong at this point?


It happens sometimes. Just reduce the volume of your pre amp and try again.




> 3) When I measure, I am able to filter to change the response. I have a bump at 45hz that does not respond at all to any kind of filtering. I thought perhaps the FBQ wasn't working, but when I filter other freqs it does work. Are there any suggestions as to why this might be happening?


Assuming you have the EQ connected between the amp and subwoofer, typically that’s caused by something else generating signal on top of the subwoofer. You described your mains as “full range.” If you don’t have them set for “small” or “bass-limited,” it could be they have enough output at 45 Hz to over-ride any equalization you’ve dialed in for the sub.




> 4) I've read the info about 'phase' but I'm not getting what to look for on that realm, or how much I should worry about that at this point.


Nothing to worry about. Just get your sub equalized properly and you’ll be happy. 

Regards,
Wayne


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## Nick (Oct 28, 2009)

JohnM and Wayne, thank you for your replies.



JohnM said:


> Did you manage to get a soundcard loopback calibration done? That gets most of the levels set to at least the right ballpark.
> 
> Re the FBQ and effect of applying filters, it would be worth explaining how you have things connected up. It sounds like you have the FBQ feeding the mains and the sub is driven from the same connection using its own internal crossover?


I have not done the loopback. I didn't understand the terms used with regard to the connections for a loopback (is there a photo?), so didn't want to cause harm. I do have the FBQ feeding the mains and the sub from the same connection and using the internal sub crossover. I do not have a processor, so I can't do a speaker setting.

I just tried using the suggested filters from the software and the suggestion was to filter at lower than where the bump was, and it lowered the peak. When I look at my graph, it shows some wide bandwidth dips in the mid-100s and wide bandwidth peaks in the 200+ range. So, I am filtering in these areas as well. The sub brings up the levels below 40hz and seems to help filling in a dip in the 100 area. I have it crossed at 80hz. 

I don't have great hearing, but the mains filtering seems to improve the upper bass and make for a nicer mid-range. 

Do you recommend trying to use an MIDI cable to let the software set the FBQ?


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## JohnM (Apr 11, 2006)

All you are doing on the loopback is connecting the soundcard's output channel to its input. You can't do nay harm with that (the thing to be careful of is not to connect an output to an output). 

Using the Midi cable does simplify setting up the filters, especially if lots of settings are being changed, though if you play around for a while you will find you can also set them up very quickly by hand.


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## Nick (Oct 28, 2009)

Thanks John. In the loopback, then, I'm connecting the sound card only to the RS meter and the computer and then running a measurement?

I like Wayne's write-up about using less filters, but certainly more get used when I follow the software recommendation. I know many people say it degrades the sound to use filters for the mains, but I find the flatter response created trumps the differences in volume along a bandwidth. I'm thinking what I am really doing is applying tone control where I need it rather than broadly.


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## JohnM (Apr 11, 2006)

Nick said:


> Thanks John. In the loopback, then, I'm connecting the sound card only to the RS meter and the computer and then running a measurement?


Not quite, the meter is not involved - you are just connecting the soundcard to itself, output to input.


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