Need help with REW - can't get reasonable measurements

**brucek** · **03-26-07, 03:07 PM**

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I can't move it.. it's locked in the center..?

Looks like it isn't locked in the Playback screen. Try it there.............

**brucek** · **03-26-07, 03:08 PM**

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So I should set the wheel on 80dB and set receiver volume so it reads 80 dB and then just go as usual?

Yeah, everything will just be at 80dB instead of 75dB..................

**brucek** · **03-26-07, 03:12 PM**

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but there's a picture

Yeah, as long as it has line-in and line-out it will be fine............. you don't need all the 5.1 ****, but if it's there you just select stereo instead....... I suspect the Connect one would be fine (I don't read Danish)

brucek

**Tobias** · **03-26-07, 04:07 PM**

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brucek wrote:

Yeah, as long as it has line-in and line-out it will be fine............. you don't need all the 5.1 ****, but if it's there you just select stereo instead....... I suspect the Connect one would be fine (I don't read Danish)

brucek

I found some specifications about it on creative's site:
http://uk.europe.creative.com/produc...ct=15911&nav=0

Doesn't look like it has line-out, or am I just missing something?

Would just like to be sure that I don't buy it just to find out something is missing on it

**brucek** · **03-26-07, 04:54 PM**

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Doesn't look like it has line-out, or am I just missing something?

connect.jpg

brucek

**allredp** · **03-26-07, 09:18 PM**

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brucek wrote:

Yeah, as long as it has line-in and line-out it will be fine............. you don't need all the 5.1 ****, but if it's there you just select stereo instead....... brucek

So, does this mean that my HTPC with 7.1 Realtek AC97 needs to be set to "stereo" in the Sounds options in my XP Media Center OS?

Thanks for the help--having fun getting started with REW (am actually stuck on "calibrating the soundcard!)...

--Phil

**brucek** · **03-26-07, 10:25 PM**

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So, does this mean that my HTPC with 7.1 Realtek AC97 needs to be set to "stereo" in the Sounds options

Yes....

**Tobias** · **03-28-07, 12:09 PM**

What do you think I could do to improve my response brucek?
Maybe turn up the gain on the sub? (It's on 50% now, and it's a SVS PCi 20-39), and then make some more filters to reduce the level? If this sounds as a good idea, how would you do it?
I mean, if I turn up and calibrate as before I will just end with the same results.. I was thinking about leaving the target curve at the lower level, and then turn up the gain and make some filters.. or something like that

I just ordered the SB connect soundcard so I should be able to make some new measurements with it soon, but I wouldn't be so surprised if the response was quite the same as with the old card

Btw, I tried a measurement with adjusment to 80dB, and I got a higher input, but the graph looked quite much the same.

**brucek** · **03-28-07, 12:50 PM**

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What do you think I could do to improve my response brucek?

Move the location of your sub. It's probably simply in a very bad spot. Try some other locations.

brucek

**Tobias** · **03-28-07, 01:01 PM**

Well, I have already tried some different locations, and actually the response I posted on the bottom of page 1 is the best I've gotten so far..

**brucek** · **03-28-07, 02:28 PM**

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actually the response I posted on the bottom of page 1 is the best I've gotten so far..

Do a one foot nearfield measurement of the sub to ensure all is well there..........

brucek

**Tobias** · **03-29-07, 09:51 AM**

I just tried placing the meter on the floor (still pointing the mic up

) about one feet from the woofer.. I got this graph:

measure9.jpg

Is that okay?

**brucek** · **03-29-07, 09:59 AM**

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Is that okay?

Well, it ain't your subwoofer that's causing your wacky response. It's the room. It's hard to get a decent nearfield with a ported sub, but that sub looks great.

ltr

**Tobias** · **03-29-07, 10:10 AM**

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brucek wrote:

Well, it ain't your subwoofer that's causing your wacky response. It's the room. It's hard to get a decent nearfield with a ported sub, but that sub looks great.

ltr

That's good to hear since I was beginning to think something was wrong with the sub

I just received my new external soundcard, and tried to do a calibration. This time the input wasn't any problem, and I ended up using an input volume of 0,237.

But the measurement from the listening position is pretty much unchanged though. I think I'm gonna try some alternative positions.. I might be able to squeeze it into a corner at one of the front speakers

**brucek** · **03-29-07, 10:28 AM**

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This time the input wasn't any problem, and I ended up using an input volume of 0,237.

Yep... that's better.

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I think I'm gonna try some alternative positions.. I might be able to squeeze it into a corner at one of the front speakers

Another thing you should try is to use multiple sweeps, which reduces noise and random noise. Try doing a 256K sweep with x4 or x8 sweeps set in the Measurements screen....

brucek

**Tobias** · **03-29-07, 11:34 AM**

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brucek wrote:

Yep... that's better.

Another thing you should try is to use multiple sweeps, which reduces noise and random noise. Try doing a 256K sweep with x4 or x8 sweeps set in the Measurements screen....

brucek

Okay thanks for the tip

I just tried placing the sub at the corner and I took this measurement:

sub_right_corner_1.jpg

What do you think about that response? It's a bit more dippy at 50/70hz, but don't you think it's better this way?

And another thing I would like to ask you is how I should read off the values of the RS meter. The needle is quite often moving some dB's up and down, so I'm getting confused which value it reads. So far I have been trying to find a value where it seem to settle down a bit.. but is this the right way to read off the value?

**brucek** · **03-29-07, 12:49 PM**

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but don't you think it's better this way?

Yep....

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but is this the right way to read off the value?

Well, the switch should be on slow to give you the best chance, but just take an average reading off the meter - use the 70 position on the RS meter dial.

The only reading you have to actually take is setting up the ~75dB at the listening position to get the that approximate target level and then match the REW SPL meter to it. Once you hit the set target level button, REW takes care of everything else. Don't worry about an exact 75dB setting - do your best.

You've obviously been successful, because your target line is around 75dB. If you find after you hit the REW set target level button and it returns 72dB or something, just redo your receiver level and REW SPL meter calibrate until you get an REW set target level around 75dB.

brucek

**Tobias** · **03-29-07, 02:25 PM**

I have been puzzling around with the BFD filters now, I inputted the filters as proposed by REW, and tried to experiment with a few (added an extra one at around 40hz).. I tried a new measurement:

sub_right_corner_with_bfd_4.jpg

I think it's starting to look better

The dips aren't so big anymore.. though I haven't made any filter with +gain.. so actually I think that's a bit weird, but as long as it is getting better it should be fine

**brucek** · **03-29-07, 02:51 PM**

Here's a trick.

Shut the filters off in the BFD (IN/OUT Green LED off) and do a normal measure of the sub.

Once the measure is done, Manually lower the target line in REW by clicking the little Target Level thumbwheel to expose more of your response peaks above the target line.

Now hit Find Peaks etc.
See what happened.

You told REW to make the filters see more peak above the line and the filters are more aggressive....

Enter the filters and then turn up the subwoofer amplifier gain control a bit and see how it looks with the new filters entered (IN/OUT back on).

brucek

**Tobias** · **03-29-07, 03:35 PM**

Thanks for the tip

I'll try that soon.

Quote:

brucek wrote:

Here's a trick.
Enter the filters and then turn up the subwoofer amplifier gain control a bit and see how it looks with the new filters entered (IN/OUT back on).
brucek

Then I'll be using a measured target level right?

**brucek** · **03-29-07, 04:17 PM**

Well, the whole point is to trick REW into being a bit more aggressive with the peaks it finds and then the filters it recommends from those peaks. You shouldn't go too far, but if you lower the target line (after the regular measurement at 75dB is finished) to end up with more aggressive filters, the result will be a smoother response (to the corrected line in REW), but the added cut will lower the overall level of the sub, so after you enter the filters into the BFD, you need to compensate by adding some gain to the subwoofer amplifier........ If you cut down to a line that you lowered by -5dB, then you would have to add about 5dB to the subwoofers volume to compensate (by turning up the subwoofers amplifier).

Once you've got a raw measure you can see for yourself how it works by playing around with the target line and FIND peaks. Clear the peaks and move the target line and Find Peaks again and see what it does...

brucek

**JohnM** · **03-29-07, 07:43 PM**

Don't forget to use "Optimise PK Gain & Q" after assigning filters, the initial REW assignments are just starting points for the optimisation, you must run the Optimise routine to get correct filter settings.

**brucek** · **03-29-07, 10:20 PM**

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you must run the Optimise routine to get correct filter settings.

Yeah, good point John, I should have made that clear.....

brucek

**Tobias** · **03-30-07, 04:22 AM**

Ahr I forgot the optimization of the filters

Got to remember this next time

Btw, when I have made a measurement and added some filters.. should I then just go set the phase and gain on the sub as usual, using for example the AVIA calibration dvd?

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