calibration confusion! - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 37 Old 03-16-07, 04:23 AM Thread Starter
 
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Re: calibration confusion!

Thanks brucek,

So to recap, I set my output/wave volume to 1.000 and reduce my amps volume. Should I change the imput volume too?

The BFD was second-hand and had firmware 1.0, I think I am right in assuming it is ok ie not the 1.3 version.

Getting there...

Graham
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post #22 of 37 Old 03-16-07, 05:23 AM
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Re: calibration confusion!

Quote:
blue_max wrote: View Post

I have a longish room, 21 x 12.5ft x 10ft ceilings. It has a bay with large windows and blinds. It's rather echoey now the curtains are gone. There are a couple of beds in there as it's our bedroom at the moment. There is a side table over the sub to hide it. This is one of those marital compromises, so sticking it in the middle of the room is probably not going to fly.
According to a room mode calculator the main modes in your room are:
26.9
45.2
53.8
56.5
80.7
90.4

Which is more or less borne out by your room response. Depending on how much grunt and headroom you have with your sub, and after following Brucek's suggestions on getting the right input levels into the BFD, I'd look at raising the volume on the sub a little to raise the troughs, EQ the "higher" levels back to a flat line (or house curve) and perhaps put a hint of a boost (no more than 3db) on the BFD for the troughs. Every little helps!

Quote:
blue_max wrote: View Post
I nearly set up my first set of filters, but despite setting up the BFD to accept midi control, it appears to send it via REW, but not a dicky bird from the BFD. Nothing at all flashes. That's when I leave it on channel 4. Maybe I am all too eager to blame the card, but I did try a couple of times. It was set up for the left channel, so it's not that.
Have you switched on the Midi capabilities on the BFD? This is done via the buttons (the REW instructions have the procedure) and is "lost" if power is turned off at any time. So if you turn off the BFD at any time, the default state is MIDI - OFF.

Have you selected your sound card's MIDI capabilities in the Control Panel, Sounds and Audio Devices, MIDI Device (under the Audio tab)?

Also, I have found that the labelling of MIDI-IN and MIDI Out can often mean the opposite. Swap your cable around as another option!

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post #23 of 37 Old 03-16-07, 05:51 AM Thread Starter
 
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Re: calibration confusion!

Thanks Bob,

Some useful suggestions there - I will certainly give it a try when I get a chance.

Cheers.

Graham
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post #24 of 37 Old 03-16-07, 07:44 AM
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Re: calibration confusion!

Quote:
So to recap, I set my output/wave volume to 1.000 and reduce my amps volume. Should I change the imput volume too
You're confusing two things here. Forgetting about REW for a minute (remember it's just a tool to help set the filters in your BFD).
You need to understand your system levels and the use of the BFD before using REW. Re-read the stuff below and get the system levels set first.

The input level to the BFD is totally contolled by the receivers volume control and trimmed somewhat by the receivers subwoofer speaker trim adjustment. We are simply trying to ensure the BFD gets an optimum a signal as possible. This means once the trim level is set for the subwoofer out of your receiver, then after that the volume level of the sub is best adjusted with the subwoofers own amplifier (as opposed to touching the trim again).

So, bypass the BFD (IN/OUT GREEN LED flashing and leave it that way for now) and setup your speaker levels with the receivers test tones (including the sub trim and subwoofer amps volume) as you normally would do.
Then put in a bass heavy movie and turn it up to the loudest you would ever use the system. If the BFD LED's are clipping in the RED, then turn the subwoofer trim down and turn up the sub amp to compensate. If the LEDs are not clipping, then turn up the trim to get the yellow LED on and turn down the sub amp to compensate.
There, now the sub trim is set for your system. Don't touch it again. The subs level will now be controlled by the sub amp volume (when necessary to change its balance against the main speakers).
You can put the BFD back on with the IN/OUT GREEN LED ON for filters engaged or OFF for filters disengaged. The flashing Green LED is filters off and the VU meters monitoring the input as opposed to the output level.

Now your system speaker levels are balanced, you can hook up REW and use it. The only system volume you'll touch is the Main Receiver Volume control. Don't touch the sub or the trim for now. Just the receivers main volume control.

Start the Check Level Routine and Set the REW output/wave volume to 1.000 and then set the receivers volume control to reach 75dB on the RadioShack meter.
Now set the input volume control on REW to the correct VU level.

Then do the Calibrate SPL routine.

Then do the Set target Level routine.

Then carry on with the measure...


brucek
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post #25 of 37 Old 03-17-07, 04:47 PM Thread Starter
 
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Re: calibration confusion!

Well, after literally hours of printing out the help files and pouring over then one by one, I have made a discovery!

The line-in choice should have been stereo mix. This makes a whole lot more sense now. But it's two forward and one back I think.

I have this as a measurement and I have NO peaks. I did think that I had done all the sound levels correctly. To be honest, it's such a poor 15in lcd monitor that I can't make out which line means what. It's also on the floor, so I am peering at it on my hands and knees!

I can't do much now as it's late, so would much appreciate any thoughts to fast-track me to filter heaven!



Thank you.
Graham

Last edited by blue_max; 03-17-07 at 04:49 PM. Reason: added some stuff
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post #26 of 37 Old 03-17-07, 05:01 PM
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Re: calibration confusion!

Quote:
The line-in choice should have been stereo mix
Nope. Set it back to line in.

Notice how the purple line is the exact inverse of the meter calibration file?

You have an internal loopback monitor turned on in your soundcard software........... The output is looping back to the input in the soundcard itself.

brucek
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post #27 of 37 Old 03-17-07, 06:10 PM Thread Starter
 
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Re: calibration confusion!

Ah, bother!

Before I got as far as the check level - all was going swimmingly until I came to check levels, just before producing the chart. It had virtually no input volume - something like -53. Literally everything else checked out up to that point. I got an error message saying to check my cables and input/output settings. That is when I went back and selected something else other than the line-in. I had the card set to stereo, so figured I had cracked it. Everything went fine until the final measurement.

Back to the drawing board - thanks again.

Graham
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post #28 of 37 Old 03-17-07, 06:44 PM
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Re: calibration confusion!

Quote:
virtually no input volume
I assume you're using stereo connectors on the line-in and line-out plugs?

brucek
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post #29 of 37 Old 03-17-07, 06:56 PM Thread Starter
 
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Re: calibration confusion!

Quote:
brucek wrote: View Post
I assume you're using stereo connectors on the line-in and line-out plugs?

brucek
Yes, the double ones like the pic in the help files. I'm just using the red (right) channels.

I am determined to get to the bottom of it. It's good to have you on my side though.

Graham
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post #30 of 37 Old 03-17-07, 07:20 PM
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Re: calibration confusion!

Quote:
virtually no input volume
Are you using a standard RCA connector on the Radio Shack meter?

Can you plug the Radio Shack meter into the AUX or CD input of your receiver with a standard RCA to RCA cable and sing... it's a microphone. Does it work?

brucek
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