# Need help with Soundcard Cal



## strange_brew (Jan 22, 2007)

Hi there, 

My first attempt at this so please be gentle with me. I followed the instructions to the letter (at least I think I did) to calibrate my soundcard. The first graph measuring the card looks pretty good, but the low frequency seems out of whack:










Then when I check the calibration I get this:










It doesn't look anything like the example in the Help section. The measurement itself "seems" ok except for the low frequency issue. Are they related problems? What I don't understand is why my calibration dashed line is in such a different place from the example shown. Can someone tell me where to start looking for problems?

Thanks!


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## brucek (Apr 11, 2006)

> Can someone tell me where to start looking for problems?


I don't really see any problems. You created the soundcard.cal file that appears to create a flat line on the loopback cable when measured.

I wouldn't worry too much about anything below 10Hz - you won't be measuring there.

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> I don't really see any problems. You created the soundcard.cal file that appears to create a flat line on the loopback cable when measured.
> 
> I wouldn't worry too much about anything below 10Hz - you won't be measuring there.
> 
> brucek


Thanks brucek. I was concerned about the first soundcard reading where there is nothing under 30Hz. Doesn't that mean that my soundcard isn't picking up anything below that level? In other words, how am I going to get accurate s/w measurements? Or is that what the .cal file does?


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## brucek (Apr 11, 2006)

Look at the vertical graph scale on the soundcard response. It goes from -3dB to +3dB. It's an exaggerated scale to show high resolution. If you changed that scale to a realistic 50dB swing as opposed to the existing 6dB swing, the response would look quite good to you. 

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> Look at the vertical graph scale on the soundcard response. It goes from -3dB to +3dB. It's an exaggerated scale to show high resolution. If you changed that scale to a realistic 50dB swing as opposed to the existing 6dB swing, the response would look quite good to you.
> 
> brucek


Gotcha.

Ok, on to the next step. I have the Galaxy CM-140 and I can't for the life of me get the level over -30.4. The input is cranked. I've tried both channels, checked all the connections, changed the ranges, etc... no dice. When I run the measurement I get an error message saying the input level is too low. And this is the resulting graph:










Any ideas?


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## brucek (Apr 11, 2006)

Are you using a mono to stereo adapter at the line-in of the soundcard. The Galaxy is mono and the soundcard is stereo, so you need an adapter to 'break out' the left and right channel, and only use the one channel and then select that channel in REW?

Did you run the Check Levels routine?

Did you run the Calibrate SPL routine?

BTW, it looks like you have your Target level set to 0dB. Set it to 75dB or run the Set Target Level routine.

Graphs should be posted with a vertical scale from 45dB to 105dB and a horizontal scale from 15Hz to 200Hz......... 

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> Are you using a mono to stereo adapter at the line-in of the soundcard. The Galaxy is mono and the soundcard is stereo, so you need an adapter to 'break out' the left and right channel, and only use the one channel and then select that channel in REW?
> 
> Did you run the Check Levels routine?
> 
> ...


I'm using the stereo mini-plug to RCA adapters on the soundmeter, line-in and line-out of the sound card. Then I'm running all the RCA cables on the left (white) channel. should the mono out from the soundmeter be mixed back into stereo into the soundcard? I thought I only needed to use one channel. Interesting thing was the soundmeter was only active on the left channel. 

I ran both check levels and Calibrate SPL.

I edited the graph above to change the target level.


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## brucek (Apr 11, 2006)

> RCA adapters on the soundmeter


The Galaxy isn't an RCA connector. It's a 1/8" (3.5mm) phono......



> should the mono out from the soundmeter be mixed back into stereo into the soundcard? I thought I only needed to use one channel.


Don't understand? Galaxy mono to one channel into the line-in.

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> The Galaxy isn't an RCA connector. It's a 1/8" (3.5mm) phono......


I'm using 3 Radio shack stereo mini-plug to RCA adapters (the ones pictured in the help files)

1 plugged into the soundmeter
1 plugged into the line-in of the computer
1 plugged into the line-out of the computer

Then I ran RCA cables from the Left (white) RCA jack:

From the soundmeter to the line-in on the computer
From the line-out of the computer to an analog input on my pre-amp

Is that not correct?


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## brucek (Apr 11, 2006)

> 1 plugged into the soundmeter


There's the mistake....The Galaxy is a *mono* 1/8" (3.5mm) phono. You can't use a stereo plug. It won't mate inside the meter properly.....

The line-in and line-out are stereo, so they're correct......

GALAXY OUTPUT CONNECTOR








brucek


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## strange_brew (Jan 22, 2007)

Aha. So I should be just using a 1/8 mono mini-plug to RCA adapter and then straight into the applicable channel on the line-in.

Thanks brucek. I'll be back shortly


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## strange_brew (Jan 22, 2007)

Ok, so I fixed the connections, but I now have the opposite problem.

When I first re-connected everything there was no change - I still could not get past -30.4. So I looked again in my soundcard settings (onboard Nforce2) and found the problem. There are settings for changing the input to "line in", "stereo mix", and "mono mix". "Line in" will not go past -30.4. "Mono Mix" I can't get under -4.0 and "Stereo Mix" I can get to -10.8 but that's about it.

I ran the measurement under "Stereo Mix" and I didn't get any errors. But this is the graph I got. There is obviously something wrong here - I'm pretty sure my Subs don't pick up steam below 20Hz and the frequency response can't possibly be that flat. Is this caused by the input level? If so I guess I need to get a new soundcard. Or is it something else?


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## brucek (Apr 11, 2006)

Note how the graph is the exact mirror image of the calibration file? That's because the output is internally being looped back to the input. You have an internal soundcard monitor turned on. You can't use stereo mix. You must use line-in.



> If so I guess I need to get a new soundcard


No, you're simply doing something wrong.

Post a picture of your mixer settings and a picture of REW settings page, so I can get a look at what you're doing.

Also test your SPL meter by plugging it into the AUX or CD input of your receiver and sing (it's a microphone) and be sure it works.

brucek


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## strange_brew (Jan 22, 2007)

> Also test your SPL meter by plugging it into the AUX or CD input of your receiver and sing (it's a microphone) and be sure it works.


Bingo! It was a faulty RCA cable from the SPL meter to the AV processor. Not sure when that cable was damaged but there you go. Thanks - it would have taken me forever to troubleshoot that.

So that fixed the input level. Now onto the next problem. I'm getting MASSIVE amounts of feedback. To the point that I can't go anywhere near 75db. I've tried lowering the input levels but that doesn't really help. Now what?

EDIT: Duh! forgot to mute the Line in:coocoo:


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## brucek (Apr 11, 2006)

I would say that you've still got a monitor turned on in the soundcard software. Most soundcards offer this feature (and call it various goofy names), but its purpose is to allow you to hear what you're recording (when using the soundcard for that purpose). In REW we want that feature shut off, including all other effects features and multichannel features - stereo only, no effects....

Take a look in your soundcard software.

brucek


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## strange_brew (Jan 22, 2007)

I "think" I finally got a valid measurement. Not too great I must say considering all the sound treatments in the room!

Thoughts? (thanks for all the help so far btw!)


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## strange_brew (Jan 22, 2007)

brucek said:


> I would say that you've still got a monitor turned on in the soundcard software. Most soundcards offer this feature (and call it various goofy names), but its purpose is to allow you to hear what you're recording (when using the soundcard for that purpose). In REW we want that feature shut off, including all other effects features and multichannel features - stereo only, no effects....
> 
> Take a look in your soundcard software.
> 
> brucek


Thanks - looks like my edit was after you wrote this - I forgot to mute line-in. First real measurement result is above


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## brucek (Apr 11, 2006)

> Thoughts?


You're measuring a sub. Change the graph scale (use the Graph Limits icon) to a vertical scale of 45dB to 105dB and the horizontal scale from 15Hz to 200Hz. Lets see what it looks like..

Did you press the Set Target Level button before measuring?

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> You're measuring a sub. Change the graph scale (use the Graph Limits icon) to a vertical scale of 45dB to 105dB and the horizontal scale from 15Hz to 200Hz. Lets see what it looks like..
> 
> Did you press the Set Target Level button before measuring?
> 
> brucek


Ok, I ran through the entire procedure again right from the beginning. I'm not sure what step I missed before but obviously I screwed something up. Here is the result using the scale per your suggestion. This is about what I expected - I told a buddy of mine I thought I had a massive valley at 60Hz and I wasn't far off! I also knew I was missing a bunch of bottom end punch and this bears out that assumption. Now how to fix it?










I don't have my BFD yet, but I'll start with moving the subs around and see what happens. I currently have 2 subs on my front screenwall and I can only move them laterally across the front. Any suggestions for placement? Right now they are each about 1/3 of the way in from the sidewalls. I could also employ the notch filters in my B&K Ref 50 pre-amp....


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## brucek (Apr 11, 2006)

> Right now they are each about 1/3 of the way in from the sidewalls


You should always measure the subs without the mains to see what's really going on. We only add the mains after the subs are equalized, so as to check the integration at the crossover area.

Place both subs together (either stacked or side by side) in a front corner.

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> You should always measure the subs without the mains to see what's really going on. We only add the mains after the subs are equalized, so as to check the integration at the crossover area.
> 
> Place both subs together (either stacked or side by side) in a front corner.
> 
> brucek


Ok, here is the measurement with the Subs only but in the same position:


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## strange_brew (Jan 22, 2007)

Here's what the front wall of my theater looks like just to give you an idea.

The subs are currently directly on either side of the center channel.


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## brucek (Apr 11, 2006)

OK, now it's easier to see what going on.... good. 

BTW, you do have the Galaxy.cal meter calibration file loaded. I trust?

Did you tell us what type of subs you are using?



> The subs are currently directly on either side of the center channel.


Not the best spot. Co-locate them both in the same corner and test....

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> BTW, you do have the Galaxy.cal meter calibration file loaded. I trust?


I do now :doh:



> Did you tell us what type of subs you are using?


B&W ASW1000's 

Here is the measurement with the .cal file loaded. I'll move them and post the next result.


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## strange_brew (Jan 22, 2007)

Ok, stacked the subs on top of each other and moved close to the left corner. Looks like it improved things a bit. But I still have those nasty dips at 26db and 74db and the entire bottom end is pretty weak. I suppose the peaks can be dealt with by the BFD but what does one do about the dips? Keep moving the subs? Unfortunately I don't have a lot of wiggle room to move them around...


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## brucek (Apr 11, 2006)

Looks pretty good now. 

The spec on your subs is +/-3 dB at 25Hz, so they'll begin to drop off at about 30Hz. The BFD will allow you to cut the areas between 40-70 and 80-120 with a couple filters and then you would raise the wholesale level of the subs with the subs amplifier. 

Having two units allows you a fair bit of headroom. These cuts will improve the sound quite a bit. Right now you're listening mostly to the peaks at 65 and 90, which drowns out the low end. If you cut those peaks, the bottom end will reveal itself. 

Not much you can do until you get the equalizer.

Good job.

brucek


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## strange_brew (Jan 22, 2007)

Thanks brucek for all your help - much appreciated!!

Although I must say this has me thinking I should be buying a new sub (or subs?). I've had them so long I forgot that they don't have much under 25Hz. And that is the visceral "feel it" range.

Given the room is 24.5'D x 13.5'W x 7.4'H and the positioning limitation across the front wall (I can't go much more than 20"D - height and width are no issue), what would you recommend as a starting point for a new sub? Or do you think I should stick with what I have? I can't help feeling that I'm giving up a lot on the bottom end and my theater just won't have the ooomph that it should unless I replace those subs. I've had them for ages so I won't be offended if you tell me they're total pieces of **** 

Would an SVS cylinder be a good choice?


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## brucek (Apr 11, 2006)

> what would you recommend as a starting point for a new sub? Or do you think I should stick with what I have? I can't help feeling that I'm giving up a lot on the bottom end and my theater just won't have the ooomph that it should unless I replace those subs.


There's nothing wrong with those subs, but they will never provide that room shaking bottom end that you're looking for. Two only provides more headroom, not bottom end. The ASW 1000 only has a 120 watt amplifier with a 12" driver in a 70 liter vented box. Pretty good for music, but not theater.

Replacing them with a single SVS would indeed provide for a better HT experience. The middle PC-plus line seems reasonably priced with lots of low frequency energy and still good for music. I believe the 20-39 is the compromise model between music and HT. You do have a fair sized room, so perhaps you would need to step up to the Ultra models, but that's starting to get expensive. You'd have to decide what you like...... Others can comment further.

brucek


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## strange_brew (Jan 22, 2007)

I could sit a PB12-Plus/2 sideways and fit it in. Do you think that would provide the kind of deep visceral impact I'm looking for? I have Monitor Audio Gold Ref 60's as mains btw, so they can handle music pretty well on their own.

I'm also looking at the JL F113 but that will depend on price.


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## brucek (Apr 11, 2006)

> I could sit a PB12-Plus/2 sideways and fit it in. Do you think that would provide the kind of deep visceral impact I'm looking for?


Yep............................. you could simply sell the ASW's. Don't try and combine them with the SVS...

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> Yep............................. you could simply sell the ASW's. Don't try and combine them with the SVS...
> 
> brucek


Ok, that is the direction I'm leaning.

In the meantime, I'm trying to understand how to use REW a little better.

I applied a notch filter on my pre-amp between 38 and 54 Hz, then raised the gain on the sub amp. I also noticed that inverting the phase increased the volume at 80Hz so I left it inverted (I can invert in my pre-amp). Looks like I need to turn the gain down a little on the sub. To do that, do I just lower the volume on the sub and increase the volume on the pre-amp to get to 75db when I do "Check Levels"? Or can I just turn down the sweep volume and get the same result? I'm not sure I understand the interaction of the 75db Check Levels and the sub gain. If I need to see 75db on my spl, how do I turn the gain down on the sub? Not sure if I'm making any sense...actually, now I think about it, do I simply increase the cut in the notch filter and let it come down to the rest of the reading...


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## brucek (Apr 11, 2006)

> If I need to see 75db on my spl, how do I turn the gain down on the sub?


If you play around with anything so the level when using REW gets 'out of whack', then it only takes a second to go through the calibration routine.

1. press the Check Levels routine button and ensure the output VU meter is still at -12db. Then adjust the processor/preamp/receiver volume control so the Galaxy meter reads 75db. (if you felt you wanted to adjust the sub amps volume, that would be fine too as long as you end up with 75dB on the Galaxy). Then adjust REW input volume to be -12dB on the VU meter.

2. press the Calibrate SPL meter button and set it to 75dB to match the Galaxy.

3. press the Set Target Level button to run that routine.

4. Measure..............

After you have equalized and set up filters on the sub, then you can play with the sub amp level to make it match the mains by using REW or your recivers speaker setup tones .

brucek


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## strange_brew (Jan 22, 2007)

Here is a measurement with:

Notch Filter = 38.3Hz - 53.7Hz (max notch width)
Notch Filter = -14db
Bass Gain = +6 db (max gain) @ 25Hz










Here is the same settings but with the notch at -18db










What do you think? My sense is that I should stay with the last one at -18db on the notch. Do you see anything else I can do with this at this point?

Also, my sub amp is now up so high that its completely out of whack with everything else. I'm assuming from your previous post that I now just lower the sub amp until its back in line with everything else?

I definitely understand now why people use the BFD!!


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## brucek (Apr 11, 2006)

> Also, my sub amp is now up so high that its completely out of whack with everything else


Yeah, and the -18dB is quite a bit of cut to use also. With that much cut and the commensurate pumping up of the sub amps gain, it eats up a lot of headroom. The +6dB gain at 25Hz on subs that are naturally down at 25hz also is a bit of a push.

What happens is that you can get a decent +75dBSPL graph when you use a lot of cut and gain, but if you attempted to get the same response at +100dB (and it's easy to do in REW - just use a 100dB target), you'll see the sub may not be able to produce the same response because of loss of headroom and compression.........

brucek


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## strange_brew (Jan 22, 2007)

Should I leave it at the -14db notch and +6db bass gain then? Or do you think I should try backing that off?

Assuming i can work with that for now, how do I go about integrating my mains?


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## brucek (Apr 11, 2006)

> Should I leave it at the -14db notch and +6db bass gain then? Or do you think I should try backing that off?


I'm sure it's fine. It would be interesting to do two measures. One at 75dB and one at 100dB and see if they are the same. If they're about the same you're good.



> how do I go about integrating my mains?


Simple. Turn them on and do the exact same 75dB measure of your sub and see how the levels match at the crossover and see if there is any interaction around the crossover frequency. Any problems around the crossover can be adjusted with sub phase and timing adjustments. Levels can be adjusted with sub and speaker trims and sub amp volume..

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> I'm sure it's fine. It would be interesting to do two measures. One at 75dB and one at 100dB and see if they are the same. If they're about the same you're good.
> 
> 
> Simple. Turn them on and do the exact same 75dB measure of your sub and see how the levels match at the crossover and see if there is any interaction around the crossover frequency. Any problems around the crossover can be adjusted with sub phase and timing adjustments. Levels can be adjusted with sub and speaker trims and sub amp volume..
> ...


Just for fun I ran the speaker levels on my pre-amp setup. I had to back off the sub volumes from about 3/4 to 1/4 in order to even get within range. Now all 7.2 speakers are spitting out 75db on the test tones.

But if I want to go back to measuring via REW, I'll have to push the volume back up on my subs to 3/4's (likely more) or they won't be able to hit the 75 db on the spl. In other words, if I leave everything the way it should be setup according to speaker levels on the pre-amp, the sub doesn't even register on REW. The only way to get the sub up with the mains is to max out their volume controls. Is that normal? or is something wrong?


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## brucek (Apr 11, 2006)

> Now all 7.2 speakers are spitting out 75db on the test tones.


I assume the processor has a tones routine and you adjust the trims of the speakers to 75dB with the Galaxy meter? I also assume the master volume is bypassed when you do this (as most receivers and processors are)? Did the preamps/processors manual instruct you to set the trims to 75dB or did it tell you to simply match the levels starting from an initial +/-0 value for each trim?

But when you feed the signal from the REW soundcard, are you saying you can't simply adjust the preamps master volume to easily get 75dB on the Galaxy meter?

I admit to being confused by what you're saying. There is a set of speaker trims and a master volume on the processor and there is the sub amplifiers own volume conrtol. Can you better describe the problem?

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> I assume the processor has a tones routine and you adjust the trims of the speakers to 75dB with the Galaxy meter? I also assume the master volume is bypassed when you do this (as most receivers and processors are)? Did the preamps/processors manual instruct you to set the trims to 75dB or did it tell you to simply match the levels starting from an initial +/-0 value for each trim?


correct - it outputs a test tone and the main volume is disabled. It says to match the levels (but suggests using an SPL meter to do so). I matched everything to 75 db using the Galaxy.



> But when you feed the signal from the REW soundcard, are you saying you can't simply adjust the preamps master volume to easily get 75dB on the Galaxy meter?


Exactly. After leaving the speaker setup described above, the mains I can hit 75 and above, no problem. But the sub can't get anywhere near 75 unless I crank the sub amp volume close to max.



> I admit to being confused by what you're saying. There is a set of speaker trims and a master volume on the processor and there is the sub amplifiers own volume conrtol. Can you better describe the problem?


If I want to set the sub to 75 for REW measuring, I have to crank up the sub amp to over 3/4, max out the pre-amp and max out the pre-amp sub output. Then I measure. But then if I turn the amp back on, the sub will be WAY above the levels of the other 7 speakers and I have to lower the subs back to match the other speakers. Seems something must be wrong - this is borne out by the results - I tested the last setup I created on a test DVD and it sounded like **** - almost like the sub wasn't on.

Do I need to do another soundcard cal? Or did I miss something earlier in the chain?


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## brucek (Apr 11, 2006)

> It says to match the levels (but suggests using an SPL meter to do so). I matched everything to 75 db using the Galaxy.


But is it your choice to use 75dB? Why a specific SPL level? 
Perhaps you are changing the trims to too low or high a level as a result. With my processor, the trim swing is +10 and -10 from an initial zero starting point. The goal is to *match* the levels, *not* to set them to any specific SPL level of 75dB. 

So I start by setting the sub amp to about middle position and then trim all the speakers (including the sub), up or down only a little bit until they match the first speaker I started from (which is at zero trim). Fact is, the actual level is somewhere around 69dB in my unit - doesn't matter. The only purpose of the trims is to match levels, not set a specific level. So, if I found that I had to change my sub trim very far from zero during that routine, I'd change the sub amp to make it close to zero. After that's all done, then the master volume is in charge.

Now, when I use REW, I only want to use 75dB because it's a nice convenient value that I can achieve by adjusting the master volume on the processor. I don't touch the trims, or the sub amp. I have lots of control with the voltage line level from the soundcard (hopefully it puts out a nice line level), and then I have full swing with my master volume...........



> But the sub can't get anywhere near 75 unless I crank the sub amp volume close to max


Do you have the output and wave volume at maximum on the REW Settings panel and the sweep level at -12dB? Perhaps your line-level signal to the processor is too low, because it's kinda weird that you can't obtain a 75dB level with the master volume...

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> But is it your choice to use 75dB? Why a specific SPL level?
> Perhaps you are changing the trims to too low or high a level as a result. With my processor, the trim swing is +10 and -10 from an initial zero starting point. The goal is to *match* the levels, *not* to set them to any specific SPL level of 75dB.


Understood - I'm not seeking out 75db for any specific reason. It just happens that the mains are close to 75 on the SPL when I start so the left main is at 0.0 (or close to it) and the others are relative to that. It was just a convenient reference to use.



> So I start by setting the sub amp to about middle position and then trim all the speakers (including the sub), up or down only a little bit until they match the first speaker I started from (which is at zero trim). Fact is, the actual level is somewhere around 69dB in my unit - doesn't matter. The only purpose of the trims is to match levels, not set a specific level. So, if I found that I had to change my sub trim very far from zero during that routine, I'd change the sub amp to make it close to zero. After that's all done, then the master volume is in charge.


Right. And I used the same process. I think I ended up with the sub gain in my pre-amp at +3.0 or something like that after I had finished fiddling with the sub amp. I probably could have gotten it to 0.0 but thought that was close enough.



> Now, when I use REW, I only want to use 75dB because it's a nice convenient value that I can achieve by adjusting the master volume on the processor. I don't touch the trims, or the sub amp. I have lots of control with the voltage line level from the soundcard (hopefully it puts out a nice line level), and then I have full swing with my master volume...........


This is where we differ. I can use my master volume to get the other speakers set to 75 db in REW without any problems. Input level is good, output level is good. BUT if I want to measure the subs as well as the rest of the speakers at the SAME TIME, I can't get to 75db without putting the master volume at +15.0db (max), maxing out the sub gain in the pre-amp, and increasing the sub amp volume significantly. It seems like I'm losing a lot of signal between the pre-amp and the subs. I have a 40' sub cable (Belden from Blue Jean Cable) but I don't think line level over that distance should be a problem - but I could be wrong.



> Do you have the output and wave volume at maximum on the REW Settings panel and the sweep level at -12dB? Perhaps your line-level signal to the processor is too low, because it's kinda weird that you can't obtain a 75dB level with the master volume...


again, no problem getting 75 db with the 7 speakers running off the amp - only with the 2 subs. I can't change any of those settings in REW except sweep level - they're all greyed out. I use the main Nforce control panel to change them. But the output volume and wave volume on the soundcard are maxed.


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## brucek (Apr 11, 2006)

> BUT if I want to measure the subs as well as the rest of the speakers at the SAME TIME, I can't get to 75db without putting the master volume at +15.0db (max


Hopefully, you're processor is in 'stereo' mode and you are feeding the mono signal from the soundcard to the CD or AUX input using a Y-splitter ?

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> Hopefully, you're processor is in 'stereo' mode and you are feeding the mono signal from the soundcard to the CD or AUX input using a Y-splitter ?
> 
> brucek


Ok, this may be where I have a problem. I haven't really been worrying about what mode my processor is in. Even in Stereo mode it outputs to all 7 speakers. Do I need to limit it to just the mains?

Also, I'm only using 1 side of the CD input (1 of the 2 analog RCA jacks). Do I need to split the mono signal from the soundcard back to stereo to go into the processor? I didn't think it mattered as its only measuring a mono subwoofer signal.


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## brucek (Apr 11, 2006)

> Even in Stereo mode it outputs to all 7 speakers. Do I need to limit it to just the mains?


Usually in stereo or direct mode, the signal doesn't pass through a DSP decoder that uses phase for steering. Think about pro-logic. It uses phase and amplitude to direct the signal to various channels. Feeding a mono signal to one of these decoders has unpredictable results. Use a mono or direct stereo mode. Strange that your stereo mode outputs to all speakers.



> Also, I'm only using 1 side of the CD input (1 of the 2 analog RCA jacks). Do I need to split the mono signal from the soundcard back to stereo to go into the processor? I didn't think it mattered as its only measuring a mono subwoofer signal.


Most people use a Y-splitter so that both mains are fed the signal, so that when the mains are checked for integration, they're both on. Actually, you can also use two cables from REW, because the line-out activates both left and right channels (not-line in though).

brucek


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## strange_brew (Jan 22, 2007)

I finally found the problem!

The processor was set to THX subwoofer. Which for the B&K means that the sub is only active when receiving an LFE channel. In movies I could hear it, but when trying to measure, it was a problem.

Back to the graphs. When I re-meausured with all my "eq" from the last go-round this is what I got:










Then I removed all my previous "improvements":










Next I moved the notch filter to deal with the peak around 60Hz, increased the gain at 25db and moved the crossover down to 70Hz to deal with the bump at 80 and ended up with:











Last but not least I measured with the mains on (I had to turn the master volume down to get to 75db again) and got this craziness - what do you make of this?


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## brucek (Apr 11, 2006)

Yeah, not too uncommon. The large dip is caused by the integration between the mains and sub. You need to adjust the sub phase control to get rid of it. If you're lucky enough to have a variable phase control, then adjust and measure until the dip is gone. If you have a simple 0 / 180 switch for phase and it doesn't get rid of the dip, you can also adjust the subs distance control on the processor to help.

The second problem is that the mains are at a higher level than the mains. Preferable the sub is equal or a bit higher than the mains...

You're getting there. 

brucek


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## strange_brew (Jan 22, 2007)

Brought the sub volume back up to match the mains (I don't understand why I can have the levels match using the processor's internal test tones, but then have a 8-10db difference when using REW?):










Then inverted the phase (its 0 or 180):










Probably the best I can do right now?


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## strange_brew (Jan 22, 2007)

Ok, enough messing around.

I've decided to pull the trigger on an SVS PB12-Plus/2

It will be here tomorrow  (the Canadian distributor is local to me)

Should be interesting to see the difference!


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## brucek (Apr 11, 2006)

Yeah, it will be interesting. I think it will be quite a difference. You did a good job on with what you have though. As you say, that's about the best you're going to get......

burcek


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## strange_brew (Jan 22, 2007)

brucek said:


> Yeah, it will be interesting. I think it will be quite a difference. You did a good job on with what you have though. As you say, that's about the best you're going to get......
> 
> burcek


Thanks for all your help again brucek - I feel like I've learned a lot in a short period of time - not only about REW but about my pre/pro! I'll be back with more graphs when I get my SVS fired up


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## strange_brew (Jan 22, 2007)

Ok, I'm back armed with an SVS PB12-Plus/2.

I have it in the front left corner of the room about 1.5' from the sidewall and tight against the back wall (don't have a choice there). There are 2" thick OC703 treatments on the front wall though.

Firstly, holy ****! what a difference. And thats without EQ!

Anyway, first choice is what to set the port tuning at. Here are the 3 graphs (25Hz, 20Hz, 16Hz) and an overlay of all 3. I'm guessing 16 Hz is the best choice since I gain at the bottom and don't really give anything up anywhere else. Agree?


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## strange_brew (Jan 22, 2007)

I obviously have a nasty room mode at 25Hz.

As with the B&W, I boosted 25Hz +6.0Db and put my notch filter from 40Hz - 55Hz and bumped up the gain. Here is what I got - not too bad!!


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## strange_brew (Jan 22, 2007)

Same thing but with the ports tuned to 20Hz. Might as well stick with 16Hz?


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## strange_brew (Jan 22, 2007)

Left the ports @ 16Hz, backed off the cut on the notch filter a little bit. Do you think its running too hot under 25Hz?


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## strange_brew (Jan 22, 2007)

Hows this for a contrast in deep bass performance?

SVS PB12-Plus/2 versus 2 B&W ASW1000's

Unreal.


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## strange_brew (Jan 22, 2007)

Here is with the mains on. What do you think? Should I play with the phase / cross-over to try and get rid of the big hole @ 70Hz?


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## brucek (Apr 11, 2006)

Wow, that thing has huge output at 15Hz. Is there no way of moving it at all to try and find the 25Hz dip?

Yeah I think the phase would help with the 70Hz dip, although it was there with the sub only, so the mains may be helping the dip already. Try the phase and see. Sometimes a bit of sub processor delay can also help around the crossover.

The response is pretty good though. Maybe move it out of the corner a little and the 15Hz will settle down and hopefully bring up the 25Hz. If you have a lot of room for movement, what some people do is put the sub at the listening position and move the mic to different positions. It's a lot lighter to move a mic around until you find the best spot...

brucek


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## strange_brew (Jan 22, 2007)

brucek said:


> Wow, that thing has huge output at 15Hz. Is there no way of moving it at all to try and find the 25Hz dip?


No kidding. Almost rattled my fillings loose. Loved every minute of it 



> Yeah I think the phase would help with the 70Hz dip, although it was there with the sub only, so the mains may be helping the dip already. Try the phase and see. Sometimes a bit of sub processor delay can also help around the crossover.


I'll try moving the sub first then see how 70 looks. I'm guessing it will just move.



> what some people do is put the sub at the listening position and move the mic to different positions. It's a lot lighter to move a mic around until you find the best spot...


Can't do that unfortunately. Moving the sub to the listening position will involve a neighbor and the removal of the screen  I'll just keep moving along the front wall and see what happens.

How much can I expect the BFD to help btw? Will I be able to flatten it right out?


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## brucek (Apr 11, 2006)

> How much can I expect the BFD to help btw? Will I be able to flatten it right out?


You can flatten any peaks between 20Hz and 100Hz. The BFD doesn't program filters less tahn 20hz, so any peaks below that are a bit tricky, but doable.

Adding gain to dips is not advisable, but some do it with decent results, unless it's a true null, and then nothing will fix it except a location change......

brucek


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## clubfoot (Apr 12, 2007)

Hi Craig did you check to make sure that the THX bass peak limiter is also set to off and that your sub xover was set to max for your sub measurements? As brucek suggested, before you add boost or notch filters try moving the sub around.


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## strange_brew (Jan 22, 2007)

clubfoot said:


> Hi Craig did you check to make sure that the THX bass peak limiter is also set to off and that your sub xover was set to max for your sub measurements? As brucek suggested, before you add boost or notch filters try moving the sub around.


Hi clubfoot. Yes in both cases.


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## strange_brew (Jan 22, 2007)

Ok, I'm a bit concerned now. I moved the sub across the front wall and could not get rid of the huge valley at 25Hz. I have the ports tuned to 16Hz and the sub in the middle of the front wall right now. This helped the huge bump down low, but there doesn't seem to be anything I can do about 25Hz. I'm assuming that means its a room mode? I've got my BFD hooked up now. Am I going to be able to fix the 25Hz issue, or am I SOL?


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## clubfoot (Apr 12, 2007)

Have you tried trimming 20Hz and 40-50Hz, you could probably knock off about 5db at both frequencies.


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## JohnM (Apr 11, 2006)

The 25Hz dip is most likely your seating position, being unaffected by the position of the sub across the front wall suggests it is either a front-to-back mode or a partial cancellation due to the reflection from the back wall. Try measuring the response with the mic a few feet forward or backward of the usual spot and compare the results.


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