# calibration confusion!



## blue_max (Feb 22, 2007)

OK, I have tried this several times and had problems with my sound card - possibly conflicting with my on-board sound. However, I think I am getting there.

I get to the check calibration part and it produces a graph like this:









This doesn't look like the samples! Is it clear from this where I might be going wrong. 

Thanks for any help.

Graham


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## Chrisbee (Apr 20, 2006)

I'm sure brucek will be along in a minute.


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## brucek (Apr 11, 2006)

You're having a bit of trouble with the soundcard calibration file. For the areas of interest which are below 500Hz, the soundcard.cal file is OK, but the card is showing oscillation after that. The loopback measured response simply validates that the soundcard.cal file is not good after ~500Hz.

This is usually caused by choosing an Input Volume setting that is too high, even though REW says the headroom is OK, the fact is it's not OK at the higher frequencies. Set the sweep level to -12db and then select a lower Input Level setting and it will stop oscillating at the higher frequency. Do successive tests until you find the best level with no ringing.......

brucek


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## JohnM (Apr 11, 2006)

You can also get responses like that if some kind of sound effect is turned on.


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## blue_max (Feb 22, 2007)

I am fairly confident that no sound effects are turned on, but will make sure they are definitely off. I will also try lowering the volume. Thanks for the suggestions. Just need the time to give it a go.

Graham


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## blue_max (Feb 22, 2007)

I still have had no luck in getting this to work, however, I have had the suggestion that using the windows mixer may be more successful.

The computer is a Dell and is running Windows XP. It has an on-board sound. I have added a pci card to give me the required input/outputs, but the software it comes with is very basic - and seems to be causing issues.

I have looked and looked, but can't seem to find the windows mixer. Would it be available with on-board sound? I would appreciate any help in getting the software on my machine - if it isn't already.

I know my way round macs, but am new to pc's, so assume zero knowledge.

Thanks all - I'm itching to get my BFD to do something useful!

Graham


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## brucek (Apr 11, 2006)

You need to first disable the on-board sound in BIOS.

Usually once Windows sees a new device in a computer it will load drivers for it that are found in Windows (unless it's an unusual type, then its own software drivers would need to be loaded).

The Mixer can be accessed by double clicking on the little volume control speaker icon in the system tray (bottom right hand corner of the windows screen).

If the little speaker isn't there, put it there by clicking Start button / Control Panel / Sound and Audio Devices and check the box.

The mixer can show either playback or record features by selecting options / properties of the mixer.

brucek


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## blue_max (Feb 22, 2007)

So many thanks to Brucek and Malice (beyond the call of duty!).

But sadly... I still have issues.

I disabled the onboard sound in BIOS - what an adventure! Also I got the sound card to use the system mixer and have the sound on the dashboard (is that what it's called?). So, set it all up and I get this graph from REW.










Is this card just junk. This is just too much work and I have nothing to show for it. Again, your patience and expert help is much appreciated. Am I flogging a dead horse with this card though?

Graham


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## brucek (Apr 11, 2006)

Graham,

Most cards work without any probelms, so, A few questions. 

Can you tell me what type and model of soundcard you're using?

Did you load its software package or are you using the embedded Windows XP software to operate it?

Are you using line-in and line-out of the soundcard with stereo adaptors and looping one channel (i.e. right channel)?

Can you post the mixer settings for both record and playback like shown below? and if you are using the soundcards software, please post a picture of its settings...

PLAYBACK








RECORD








brucek


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## blue_max (Feb 22, 2007)

OK, sorry for the delay. I have to drag the pc back to the other end of the flat, so I can hook it up to the internet and get the files onto the mac, where I am much more comfortable.

This is the card I bought.
http://tinyurl.com/2k35bf

I did load the software 'package'. At first it didn't seem to show anything, so I disabled the onboard sound (it's a dell dimension 3000). Then it took. It's just a simple sound mixer, but I don't really understand how it works as there is no explanation. Now I have disabled the onboard sound via bios. Selected the soundcard in the sounds control panel and it seems to work. I still have the old mixer down at the bottom right hand side. I am now using xp to control the volume.

I have set the sound card to use stereo and only one jack puts out sound. I use that for the line out. The line in one is the only one that seems to work, so I am guessing is the right one! I am looping using a stereo adapters to phono lead.

Here are the pics as requested.




























Hope I have made a school boy error and it can be sorted simply.

Thanks once again.

Graham


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## brucek (Apr 11, 2006)

> Hope I have made a school boy error and it can be sorted simply.


The C-Media CMI8738 looks like a nice card. I do see where they supply just the drivers on their site. If all else fails you could uninstall the C-Media software package and then reboot windows, at which time it would "find new hardware" and would ask for the drivers if it needed them.

Either way, it sure looks like you have all the settings correct. I was hoping to see a mistake. You did say you loaded the software package from C-Media. This means in the Windows "Control Panel", there will be an icon to start that software package and play with its features. Look again that in addition to only enabling the card for two channel, that no wacky features are turned on. If that doesn't clear the problem, I would try the software uninstall and let windows handle it all on its own.

The last resort of course that can be used is to get the best soundcard calibrate file you can get and then edit it to remove the frequencies above where it starts to mis-behave. The file is a simple text file and can easily be editted with notepad and then resaved. Simply delete the entries above a certain frequency and point REW to the file as if it was fine. This works and simply doesn't provide compensation above that chosen frequency (i.e. 1000Hz)......I suggest this because in the frequencies of interest (i.e. 10Hz -200Hz), the file appears fine to do the job

brucek


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## blue_max (Feb 22, 2007)

Thanks Brucek,

I have tried many settings, but nothing shifts the issue.

So I have tried your suggestion of deleting everything above the 1000 mark. Then I ran a check with C weighting unchecked under mic/meter.

Can I work with this?










Hope so!

Graham


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## brucek (Apr 11, 2006)

Yes, it will be fine for sub measurement.

If you set your graph axis to the standard of vertical = 45dB to 105dB and the horizontal = 15Hz to 200Hz that we use on the site for sub measurements, you'll see the loopback cable measures a flat line. So that means you have a response that eliminates the test equipment and all you'll be seeing in a room response will be your sound equipment. Be sure to load the microphone/meter calibration file for the meter you will be using when you take the measurements.

Be sure to set the target level to 75dB when measuring..


brucek


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## JohnM (Apr 11, 2006)

Graham,

Could you post images of the impulse response and the scope graphs when you do a loopback measurement? It might give a pointer to where things are going wrong.


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## blue_max (Feb 22, 2007)

Yes JohnM, I will certainly see if I can do that. Thank you. 

Meanwhile... I have done my first graph! After so long without anything to show for it, I have managed to get a chart at least. Whether it is on the right lines is another matter. I get so confused about where I am supposed to alter the volume - mixer or amp. I have the amp quite high to get a level (about -12). 

I find the relationship with room EQ (it's a denon amp) and auto setup, changing the subs input to set the highest level for the BFD, then altering the subs volume to match the fronts, then altering the volume in REL and I am totally confused.

I probably need to go back to basics and work through it again when I finally get the card sorted out - unless this chart is working?


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## blue_max (Feb 22, 2007)

Here are the charts as requested. Hope they reveal something.

Thanks for your interest.

Graham


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## brucek (Apr 11, 2006)

> I get so confused about where I am supposed to alter the volume - mixer or amp. I have the amp quite high to get a level (about -12).


If that's the case, then raise the Wave and Output volume to 1.000 and then use the receivers volume control to set the Radio Shack SPL meter to 75dB.

Your chart is very good. (although you need the BFD for sure  )



> I find the relationship with room EQ (it's a denon amp) and auto setup, changing the subs input to set the highest level for the BFD, then altering the subs volume to match the fronts, then altering the volume in REL and I am totally confused.


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 contolled by the sub amp volume.
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.

brucek


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## Malice (May 1, 2006)

And when you get that sorted, I'd see if there is anywhere else you could move the sub to. Just a few inches can make a difference with troughs (42Hz 51Hz) which could be caused by unwanted reflections in your room interacting with your "original" sound. What are your room dimensions?
Bob


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## blue_max (Feb 22, 2007)

Hi Bob, giving me advice from both sides of the pond hey! Gord bless yer.

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.

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.

Here's the room in case it helps anyone.










Graham


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## brucek (Apr 11, 2006)

> 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.


Unless you have replaced the PROM in the BFD to upgrade to V1.4 firmware, then the Midi control doesn't work. You'll have to enter your filters by hand. READ THIS THREAD



> Here are the charts as requested. Hope they reveal something.


Not enough signal level. It's all down in the noise. Re-read my thread above about setting the levels.

EDIT: as an example here's an impulse response of one of my subs. I have noise around -50dB, but there is some good signal level, so it works out....









brucek


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## blue_max (Feb 22, 2007)

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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## Malice (May 1, 2006)

blue_max said:


> 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!



blue_max said:


> 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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## blue_max (Feb 22, 2007)

Thanks Bob,

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

Cheers.

Graham


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## brucek (Apr 11, 2006)

> 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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## blue_max (Feb 22, 2007)

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


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## brucek (Apr 11, 2006)

> 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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## blue_max (Feb 22, 2007)

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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## brucek (Apr 11, 2006)

> virtually no input volume


I assume you're using stereo connectors on the line-in and line-out plugs?

brucek


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## blue_max (Feb 22, 2007)

brucek said:


> 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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## brucek (Apr 11, 2006)

> 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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## blue_max (Feb 22, 2007)

brucek said:


> 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


Hi brucek, yes it is standard rca connectors. I can't sing : ), but CAN get sound out of the mic. To be honest, I was able to meet all the criteria of the software - and it was as expected - all the way up to the measure panel when I was asked to check the levels. That is where I get the -53 reading and the warning it is much too low. The check of levels in the setting panel was fine.

Tis a mystery.

Graham


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## brucek (Apr 11, 2006)

> all the way up to the measure panel when I was asked to check the levels. That is where I get the -53 reading and the warning it is much too low. The check of levels in the setting panel was fine.


Ahhh, there's something you failed to mention - that the Check levels was OK (in Check Levels) and not in the Measure routine.

That's because the _Check Levels_ routine in the Measurement screen and the _Check Levels_ routine in the Settings screen use different values to generate the pink noise.

The Check Levels routine in the the Settings screen uses the fact that you have the _*Check/Set levels with Subwoofer*_ pull-down selected to generate its test noise.

To double check and verify that the _*end frequency*_ of the sweep that you have selected in the Measurement panel matches that subwoofer setting, its' Check Level routine uses the end frequency as the pink noise hi-limit cutoff. So if you had 20KHz as the end frequency to measure for your sweep, you can see how the pink noise would be different (between the two Check Levels) and as such the low level signal you're experiencing.

Set the End Frequency in the Measurement panel to 200Hz..................









brucek


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## blue_max (Feb 22, 2007)

Success!!!

Thank you brucek. I changed back to line-in and it all seemed to work. The 200 figure in your previous post was there and still is, so I don't really understand what had changed. Maybe just changing the input back to line-in made it register in some way?

Malice, you were right about the midi connections needing reversing - never would have thought of that, so thanks!

Anyway, Just to confirm, here are my graphs.

before filters.










with filters applied (not manually adjusted).










and with the filters and the main speakers.










It seems that I am going to have to increase the sound level on the sub. Is this via the subs volume control?

Then I can add a house curve and add a few filters to push up the dips by 3db or so - is this correct?

Many thanks for your help and thoughts on this.

Graham


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## brucek (Apr 11, 2006)

> It seems that I am going to have to increase the sound level on the sub. Is this via the subs volume control?


Yes. Also, if you want more of the plot considered for filter recommendation, then before pressing the Find Peaks button, manually lower the set target thumbwheel to include more of your plot above the target line.



> add a few filters to push up the dips by 3db or so - is this correct?


Adding gain filters is not a great idea. Your dips seem to be sharp and likely you won't hear them. Better to raise the sub level as you've already figured out (and then cut a bit more on the new peaks)...

brucek


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## JohnM (Apr 11, 2006)

Did you go through the "Optimise PK Gain & Q" step after assigning the filters? If you dd, you may want to manually tweak (increase) the bandwidths for filters 1, 2 and 3 to get a smoother corrected result, use "Adjust PK Gains" afterwards to get the levels correct.


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## blue_max (Feb 22, 2007)

Thanks John,
I think you are quite correct - although this is 'old' now. I have had another crack and found it also works better with the phase at 180. I added a house curve, increased the subs level and hammered down the peaks a little more heavily. This one was just to get some filters in to sample what could be achieved. I must say, initial real-world results are quite impressive - I am really beginning to appreciate what the bfd is doing for me. It is quite an expense on top of the sub, including all the extras, such as soundcard and cabling, not to mention the learning curve, but it has all been very worthwhile. In fact, I am only now getting the value out of my expensive subwoofer!

If I ever get the luxury of a couple of hours to myself, I would love to have a real good play and share my results with you guys. REW really is an excellent piece of software. Being able to see what is going on is a revelation.

Graham


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## Malice (May 1, 2006)

Without a BFD and REW I'm sure by now I would either have had to have sold my sub, or at least have sold the missus. The sub without EQ and SWMBO were not destined to share the same floor space!!

Bob


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