My Graph

**Jonten123** · **09-08-07, 03:56 AM**

What do you guys think of this? Just finished my first calibration..

**brucek** · **09-08-07, 07:53 AM**

Although it looks good, I have to say I'm somewhat confused. Did you actually boost the signal by 27dB at 20Hz? If so, you added far too much boost to accomplish your goal.

Your sub looks like it is naturally dropping off around 35Hz. Sometimes you can locate a sub in a corner and realize some natural room gain. Then you can add a bit of boost (never more than 5dB) to help out too.

Too much boost removes headroom in both the sub and the equalizer. If you have set the input to your equalizer correctly, then a boost filter of ~27dB would cause the equalizer to clip - resulting in the requirement to lower the input level by that much to avoid clipping. This severely lowers usable dynamic range.

Next time you measure it's a good idea to use an end frequency of 200Hz and not 80Hz - (and be sure to only measure the sub without the mains turned on).

brucek

**Jonten123** · **09-08-07, 09:45 AM**

Actually, I did boost it that much. I thought it was that easy. But now I know better. I hope

I moved the sub to another corner and got better readings. I´m only going to use the sub with movies so I´m wondering if I should try to keep a flat line from 35Hz to 80Hz and the try to cut everything above that. Or follow the blue line. Should I do anything with the signal below 35Hz and or try to boost the dips at 50 and 75 Hz? The dip at 50Hz comes and goes as you see. Don´t know what do do about it...

**brucek** · **09-08-07, 10:13 AM**

You could fairly easily equalize that response down to the blue target. You can even throw in some small boost (<= 5dB) and see if some of the dips respond. Sometimes they don't, so give that up if they're stubborn. Narrow sharp dips actually are fairly inaudible and should be left alone (the one at 50Hz shouldn't be touched).

The standard graph scale we use is vertical of 45dB-105dB and horizontal of 15Hz to 200Hz. If the subs bottom end is around 30Hz, I would use a horizontal of 25Hz-200Hz.

Once you have equalized the sub, then you add the mains and take a reading. This is when you look at the crossover reaction between the sub and mains and tweak the subs phase contol to get the best and smoothest transition. You can also use the receivers sub distance control a bit to adjust problems at the crossover (when phase doesn't work).

brucek

**Wayne A. Pflughaupt** · **09-08-07, 11:00 AM**

I agree with brucek – the 50 Hz issue is to narrow to worry about and I doubt you can set an EQ filter narrow anyway.

It looks like ~ 35 Hz is about as low as this sub is going to go with equalization. Even then, keep an eye out to make sure you’re not overdriving it. It’ll bottom out loudly if that happens.

If you end up with response issues an octave or so below the crossover point, you might try equalization there as a last resort. The problems are phase-related, but I’ve seen many cases where it made a difference. Probably because the equalizer introduces its own phase changes.

Regards,
Wayne

**Jonten123** · **09-08-07, 01:22 PM**

Thanks for the help, I appreciate that! I think I might be doing something wrong. I adjusted the filters the best I could and got it very close to the target line. I went on a little further than 80Hz just because I could

But now when I am at the blue line Rew tells me to increase the Av processors volume. I push the "set target level" and finds out it´s down to 69.9dB now. I adjusted the volume so that the target line would start at 75dB again and made a new measurement. Now there is a difference of 5dB all the way. What am I doing wrong

**brucek** · **09-08-07, 01:35 PM**

Quote:

What am I doing wrong

Nothing really. When you add filters, the overall level decreases. So, when you remeasure after modifying filters, its best to go through the whole REW calibration with Check levels etc. It only takes a second, and this brings everything back to the ~75dB target.

Good job, BTW.

Now add the mains and (recalibrate exactly as before when you were just measuring the sub) and see what the crossover transition is like...

brucek

**Jonten123** · **09-09-07, 02:12 PM**

I guess I´m still not doing it right. I can make it to the target line but I doesn´t feel right. When I have adjusted a filter I push the "set target level" and it says 73.5, maybe. Then I use any volume control to get up to 75dB again. I even use "Level (dB FS)" to adjust in the Make a measurement menu. Then I measure again and adjust the next filter and so on. This is how it turns out. Everything on the side is going up up. A small step by step guide would really help//Jonten

**brucek** · **09-09-07, 03:37 PM**

Quote:

When I have adjusted a filter I push the "set target level" and it says 73.5, maybe

You shouldn't really push "set target level" after adjusting a filter. Once all the filters are set in you BFD and you want to check your work, you must go through the whole REW check levels setup again (which takes seconds when you're used to it).

Anyway, now that you have added your mains, you can see that there is a bit of a difference in the wholesale level betwen the mains and sub. The sub loudness needs to be adjusted up a bit using the subwoofers own amplifier volume control. Turn it up a bit and do a remeasure so that the sub and mains are at a more even level. (Some people even like the sub a bit hotter than the mains)....

------------------------------------------------

Here's a bit of a rough step by step of the setup once the soundcard.cal and meter.cal are loaded and the cables are all hooked up and ready to go..

To go through these steps only takes a second......

1. Run the Check Levels routine (in Settings icon) selecting Check/Set Levels with Subwoofer in the Levels pull down box, with the SPL meter at the listening position and the dial of the meter at 80dB position (or whatever scale allows 75dB to be measured).
Ensure the REW output VU meter is at -12db and the sweep level at -12dB.
Set the Wave Volume at 1.000 and the Output Volume about ~0.500.
Then adjust your receivers volume control so the actual standalone Radio Shack SPL meter reads ~75db at the listening position.
Then adjust REW Input Volume to end up with -12dB on the REW input VU meter.

2. Run the Calibrate SPL routine (in the meter tab) to match REW's SPL meter to the real SPL meter to ~75dBSPL.

3. Run the Set Target Level routine, which will set the target to ~75dB.

4. Run the Measure routine and set the End Frequency to 200Hz for subwoofers.

5. Measure.................... (use a larger number of sweeps and longer length for more accuracy and less noise)

6. Using the Graph Axis Limits icon, set the vertical scale to 45dB to 105dB and the horizontal scale for subs to 15Hz to 200Hz.

BTW, your response is starting to look real good. Only a little bit of work left to do....

brucek

**Jonten123** · **09-09-07, 05:32 PM**

So you adjust all the filters and then run the REW calibration with Check levels etc... What about the targetlevel that drops after each peakadjustment + remeasuring? If I adjust from 35 Hz to 80, I will have to go back to 35 again and lower that peak again since the targetlevel is lower now....If I remember correctly..Maybe the targetlevel stayed put and only changed when i pushed set target level... It´s in the middle of the night now and I don´t want to wake anybody up. This are my thoughts anyway. Thank you for your time! ( The mains are not connected in that measurement)

//Jonten

**brucek** · **09-09-07, 05:53 PM**

Quote:

The mains are not connected in that measurement

Huh?.......................

Quote:

What about the targetlevel that drops after each peakadjustment + remeasuring?

Huh?......................

OK, you're making this wayyyyyyyy more difficult than it actually is.

You start by simply taking a raw measurement once REW is setup (as I outlined).

Then you use Find Peaks and Assign Filters to get the complete list of filters REW recommends.

You enter those filters into REW.

Then start again and setup REW (the way I outlined) and remeasure to see how you did.

That's it.

brucek

**Jonten123** · **09-11-07, 07:36 AM**

It is diffucult

You can follow my progress on this graphs. I did the calibration with check levels and the spl reader measures 75dB in my livingroom. First graph is how it turned out. Then i adjusted the filters and made a new measurement. To get the targetline back to 75dB again I did the checklevels routine with adjusting the receivers volume so the spl reader measures 75dB and rews input volume -18. When adjusting input volume withs rews input volume ctrl nothing happends..so I raise Line in in recording...Then I measure again and thats the graph number 3. I´m getting the same results as the way I did ´before..Resulting in the graph where you thought my mains where connected...

**Jonten123** · **09-11-07, 08:23 AM**

Or is it so that I am done at graph nr 2? All the frequences has got the right level but at an overall level that is lower.

**brucek** · **09-11-07, 08:49 AM**

Quote:

When adjusting input volume withs rews input volume ctrl nothing happends..so I raise Line in in recording

Yeah, that's fine - no problem there, you're allowed to adjust the Windows mixer Line-in volume if the input volume is at its limit.

Your graph looks fine.

Quote:

I´m getting the same results as the way I did ´before..Resulting in the graph where you thought my mains where connected...

Are you saying that your mains are connected in those three graphs?

brucek

**Jonten123** · **09-11-07, 11:15 AM**

After adjusting my sub (first graph)I added the mains (second graph)..Just connected them..What do you think?

**Jonten123** · **09-11-07, 11:29 AM**

Lowered the volume of the mains....

**brucek** · **09-11-07, 11:37 AM**

Not bad - you might want to play with the phase control of the sub to try and reduce the peak at around 80Hz. If the phase control doesn't help, you can adjust the receivers sub distance setting a bit and also play with the filters around 80Hz.

brucek

**Jonten123** · **09-11-07, 01:01 PM**

I get some changes in the 35-80Hz area when I use the phase or raising the volume on the mains. The mains should not do anything at all in that area, right? That is not something I should correct..? This is how it looks now.. The phase ctrl did almost not do anything when I had the sub connected alone..

**brucek** · **09-11-07, 01:24 PM**

Quote:

That is not something I should correct..? This is how it looks now.. The phase ctrl did almost not do anything when I had the sub connected alone..

That's correct, the phase control will not do anything to a response measurement plot when only the subwoofer is active.

The phase contol only has an effect when used in concert with another speaker. The phase affects the interaction between two things, so you'll only see a difference when you plot the subwoofer and the mains together.

Look at this representation below.

In a perfect world, you see the subwoofer response with an 80Hz crossover and the mains response with an 80Hz crossover.

Then the red line shows how the two combine to produce a perfect flat end resultant.

This red line area is where the phase control has the greatest effect.

80crossover sub plus main.jpg

Trust me, the graph shows what the voltage waveforms look like in reality.
Once that voltage hits a speaker driver, and is let loose in the air, then you see the bumpy ride that results in your pesponse graphs. The BFD and phase and distance and positioning are all designed to help make the ride less bumpy.

brucek

**Jonten123** · **09-11-07, 03:01 PM**

Ok, thats why it´s a sloping curve... When I added the mains I tried to get them to play at 75dB on the splmeter, but it was not possible to raise the "Level Cal" in the receiver that high. I can´t change the volume on the receiver or from the pc, right? Then I change the subs volume to, and they will never match.. Maybe, I´ll start out with a higher volume on the receiver and lower volume on the sub next time. That should work, I hope.

If I manage to get the peak down with the phasectrl and the area between 35-80 looks a little bumpy, then I shouldn´t correct that with filters, right? //Jonas

**brucek** · **09-11-07, 04:38 PM**

Any combination that works is OK, but you start with the phase.

Nothing has to be ruler flat. You're really just trying to lower any bad peaks.....

brucek

**clubfoot** · **09-12-07, 07:12 AM**

Quote:

Jonten123 wrote:

Ok, thats why it´s a sloping curve... When I added the mains I tried to get them to play at 75dB on the splmeter, but it was not possible to raise the "Level Cal" in the receiver that high. I can´t change the volume on the receiver or from the pc, right? Then I change the subs volume to, and they will never match.. Maybe, I´ll start out with a higher volume on the receiver and lower volume on the sub next time. That should work, I hope.

If I manage to get the peak down with the phasectrl and the area between 35-80 looks a little bumpy, then I shouldn´t correct that with filters, right? //Jonas

The way I do it is to set the speaker size to small, input the distance and then set the levels of all speakers and sub in the receiver setup menu to 75db and write down the values. Fortunately for me my receiver automatically goes to "0db" during its test tones, so I use 0db for REW calibrations and have had no issues with level adjustments. If I need to adjust sub level I use the sub volume control not the receiver volume control.

**Jonten123** · **09-12-07, 09:30 AM**

I found it to be very difficult to get a good looking graph with my sub+mains connected. This are how my mains look! Any comments on how to get it better is appreciated. I have the mains set to small now..It looks better that way..

**clubfoot** · **09-12-07, 12:23 PM**

Quote:

Jonten123 wrote:

I found it to be very difficult to get a good looking graph with my sub+mains connected. This are how my mains look! Any comments on how to get it better is appreciated. I have the mains set to small now..It looks better that way..

Realizing that if you are using the RS meter it is reliable only out to may be 7 KHz, now is a good time to reposition your main speakers. Do one main (set to large) at a time and only take measurements with one main. Pull them a foot away from the rear wall and about 18" from the sides as a starting point and once you have the mid to bottom as smooth as you can WITHOUT the sub, take some new measurements with the sub (main set to small). Don't forget to input any distance and level changes you make into your receiver before adjusting phase...etc.

**Jonten123** · **09-12-07, 02:51 PM**

Thanks for the guys. This is how it looks now. Only 6 filters used. 5 to reduce peaks when calibrating the sub and one for boosting at 83Hz (+4) when the mains where on. I cant get it better than this with placement or phasectrl. Should I do any finetuning with filters? Moved the sofa forward from the backwall almost 2 feet and it help a lot. I´ve read that most people doesn´t seem to like this kind of flat curve. Is there a certain housecurve that people like better for movies

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