sub hums if I turn on SPL meter

**subby** · **08-24-07, 02:34 PM**

I can only increase the sweep level. Do get to 50 db now instead of 59 db if I turn the sweep level to -3.0db

Nothing else is connected but the line input to the line output.

**brucek** · **08-24-07, 03:08 PM**

Quote:

I can only increase the sweep level.

Aha, maybe we're getting somewhere.

Why can't you control the Wave and Output level?

Here's what my Settings screen looks like during a soundcard cal routine. Are you not able to change the levels?

check levels soundcard cal.jpg

brucek

**subby** · **08-24-07, 05:01 PM**

Quote:

brucek wrote:

Are you not able to change the levels?

nop, only the sweep level.

I can also choose "intel(r) integrated audio" as soundcard and then I do can increase wave volume, output volume and input volume. In this case I get to about 38db witch is already better but still not enough. I also don't know if this is right because I don't know if I still use Delta 44 or the break out box then.

I also see u use the realtek AC97 soundcard. We also have it my dad's laptop but it only has a microphone and headphone input.

**brucek** · **08-24-07, 06:09 PM**

Quote:

it only has a microphone and headphone

Nope - no good - can't use a microphone input. People with laptops have to purchase external USB soundcards..

Quote:

nope, only the sweep level

OK, sometimes REW can't see the volume controls of some drivers. No problem, go to the soundcards own mixer (usually found in Control Panel) and adjust the Wave volume and line-in volume from there.

Failing that, control it from the Windows mixer itself. Give that a try. It should make a difference

brucek

**subby** · **08-24-07, 06:22 PM**

on the pannels both soundcards (intel(r) integrated soundcard and Delta 44) were already set to it's highes level possibles. Both the wave volume and the line-in volume.

**brucek** · **08-24-07, 07:15 PM**

I wonder if you tried another one of the four channels if it would make a difference - probably not.

Seems strange that a soundcard as good as that one can't get enough level to loopback to itself.

I'm kinda stumped here..........

**subby** · **08-25-07, 05:00 AM**

Quote:

brucek wrote:

I wonder if you tried another one of the four channels if it would make a difference - probably not.

Yes, I already tried that before without any result.

But I tried something else this morning and it might be I'm on to something.

I took a regular stereo cable and I plugged all 4 the phono to RCA plugs at both ends.
So in the line outs 2 cables and in the line ins 2 cables. And again it worked and got to 9db fs wich is enough. I think the break out box or soundcard only reads the signal if it comes from 2 cables. This is only so with the line ins though. So I might have some good news and bad news.

the good news is that we may have solved the problem this time. the bad news is that I may need to find a plug that has a phono in at both ends and a cable that devides a mono signel into 2 cables. wich means only one cable at the one end and devides into 2 cables at the other end. So even though the signal from the spl meter is only mono I might still have to devide over 2 cables. I think the soundcard only reads a signal if it comes from to cables.

The line out shouldn't be a problem with only one cable that goes out to the BFD.

very strange though.

any sugestions to make it easier that have to buy a new cable and phono to phono plug?(the cable from my spl meter to my soundcard is 10 meters so I can't replace that cable or I have to move my whole pc equipment to my room)

**brucek** · **08-25-07, 07:33 AM**

I don't understand the logic behind this working, but can't argue if it's successful. Have you examined the soundcards software application in the areas of channel balance etc to find a clue?

Either way, it's easy enough to split a line-out signal to two with a Y-splitter. They come in all varieties from Radio Shack like this RCA one:

Have you been able to create a decent soundcard calibration file?

brucek

**subby** · **08-25-07, 04:27 PM**

Nice, I still had such plug as seen on that picture of you somewhere deep in a closet.

The soundcard calibration went fine and I could succefully save it as a cal.file. The measure without the C weighting wich you have to do after the soundcard calibration also at 9db.

Now comes the tricky part: Checking levels. There seems to be a signal coming in from the spl meter. I just don't when I have the right level and how to read it. I find the instructions of the REW helpfile a but vague at this stage. The only thing I know is I have to get to 75db, but where do I have to read it? Do I have to look to the input peak level or at the spl meter? Or do I have to read 10db on the input peak level while my spl meter level indicator and range shows 75db?

**brucek** · **08-25-07, 05:19 PM**

Quote:

Now comes the tricky part: Checking levels. There seems to be a signal coming in from the spl meter. I just don't when I have the right level and how to read it.

Here's a shorter version of the important steps left to do......

You have removed the loopback you used to create the soundcard.cal file and hooked up the Line-out of the soundcard (left and right) and connected both channels to your receiver AUX or CD input and put the receiver in stereo mode.

Hook up the SPL meter to the Line-in and select that same channel in REW in the Settings icon.

1. Ensure the soundcard and SPL meter calibration files are both loaded (the soundcard.cal you already created and stored).

2. Run the Check Levels routine (in Settings icon) selecting Subwoofer in the Levels pull down, with the SPL meter at the listening position and the dial of the meter at 80dB position.
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 or higher if needed.
Then adjust the receiver volume control so the actual standalone SPL meter reads ~75db at the listening position.
Then adjust REW input volume to end up with -12dB on the REW input VU meter.

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

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

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

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

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

brucek

**subby** · **08-25-07, 05:37 PM**

Quote:

brucek wrote:

You have removed the loopback you used to create the soundcard.cal file and hooked up the Line-out of the soundcard (left and right) and connected both channels to your receiver AUX or CD input and put the receiver in stereo mode.

Is it also ok if I just plug it in the BFD? Because I'm planning to calibrate my sub and then finally just set my receiver's sub level to 0.0db.

**brucek** · **08-25-07, 06:55 PM**

Quote:

Is it also ok if I just plug it in the BFD? Because I'm planning to calibrate my sub and then finally just set my receiver's sub level to 0.0db.

You really need the receiver in play for a several reasons.

It provides a very convenient volume control over the signal to set your 75dB for the test.

It provides the bass management of the sub and mains signal, so you are able to integrate the two together. This is quite important to the final result.

The subwoofer speaker level trim set by the receiver is adjusted as per the BFD Guide and should be set up first. See the BFD Guide on Setting the Input Levels of the BFD.

brucek

**subby** · **08-26-07, 05:48 AM**

Quote:

brucek wrote:

You really need the receiver in play for a several reasons.

Ok, I understand. But is it ok if I use my BFD as a piece for in between because my kinda out of Coax cables that are long enough from my line out to my receiver. So is it ok if I send an RCA cable from my line out to my BFD and then a coax cable from my BFD to my receiver? Or is it important that the BFD doesn't interfier in that signal. I have the impression that the BFD doesn't change the signal volume unless you change the frequentie volume.

So I'm basivly only going to use the BFD as piece to connect the wires in this stage because I'm out of cables that are long enough.

edit: I started the check level routine through my receiver. I set the level of my receiver so that my spl needle was set to 75db but on the VU meter in REW it only reads 40db.

**brucek** · **08-26-07, 06:20 AM**

The BFD is connected between the output of the receiver and the input of the subwoofer.

I'm a bit confused about what you propose. If your cables aren't long enough to reach the receiver, then you could simply extend them with another set of cables using in-line couplers.

brucek

**subby** · **08-26-07, 07:38 AM**

I don't understand why the BFD is already necesairy to be connected between the receiver and the sub if all frequenties in the BFD are still set at 0.0db so they won't change anything in the signal.

edit: I started the check level routine through my receiver. I set the level of my receiver so that my spl needle indicated 75db but on the VU meter in REW it only reads 40db.

**brucek** · **08-26-07, 08:26 AM**

Quote:

I don't understand why the BFD is already necesairy to be connected between the receiver and the sub if all frequenties in the BFD are still set at 0.0db so they won't change anything in the signal.

I'm confused about why you are concerned about this. What are you proposing and why?

Quote:

I set the level of my receiver so that my spl needle indicated 75db but on the VU meter in REW it only reads 40db.

Sounds like the SPL meter is not connected properly to the line-in of the soundcard. You're not getting a signal from the SPL meter into REW through the soundcard input. Does the SPL meter and cable function properly - you can test the meter and its cable by plugging it into the receiver (AUX input) and test it like any other microphone....

brucek

**subby** · **08-26-07, 10:23 AM**

Quote:

brucek wrote:

I'm confused about why you are concerned about this. What are you proposing and why?

Well I don't have these in-line couplers at this point. So unless it really necearly I might just do the level check as I'm doing right now. I already set up the level of my sub with the help of my receiver's MCACC function.

Just checked the cables and SPL meter and it works fine. I hope it's not my soundcard again that can't receive the spl's signal properly.

**subby** · **08-26-07, 11:24 AM**

Quote:

brucek wrote:

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

is it also ok if I just load the RS spl meter cal.file that you can download from HTshack in the download section?

**brucek** · **08-26-07, 12:53 PM**

Quote:

is it also ok if I just load the RS spl meter cal.file that you can download from HTshack in the download section?

You definitely need to load the RS SPL meter calibration file from the download section (pick the model you own), and you also need to run the Calibrate SPL routine in REW. These are completely separate issues. Both quite necessary.

The calibration file compensates for known inadequacies that the SPL meter suffer from.
The Calibrate SPL routine in REW matches the REW SPL readout to equal the 75dBSPL set at the listening position, so that they may track accurately.

brucek

**subby** · **08-26-07, 04:25 PM**

ok, I understand

what concerns the low spl signal. I might not exlude the possibility that I have to devide the SPL's signal over all 4 line inputs of the souncard's break outbox. I know, it wouldn't make sence to me either. But the case that the 2 wires now give only have the volume that I have to get, maybe the soundcard will get the full signal if it receives the signal over all 4 line input. It's going to complicated with all the cables and in line couplers that I have to put in between and I'm probebly going to have to run to the store tomorrow for that. If that doesn't work I see no other option then to e-mail M-audio. My only concern is that they probebly don't know REW and maybe can't help me very far.

In the worst case scenario I'm going to have to buy an extern soundcard but I hope it doesn't come to that.

**subby** · **08-27-07, 05:07 AM**

ok, I just found something out.

The reason that I only got a proper signal to the line in with a stereo cable during the soundcard calibration didn't have anything to do with the stereo cable. I just found out that I only get a proper signal if I use the 2nd line in port, only then I get to 10 db. the 1ste, 3th and 4th line in port only get me to 53db.

But during the check levels routine, I only get to 40db as I already said. Connections and all the settings in the control panel are fine though. So I just e-mailed M-audio. I also send them a link to the help files of REW so they can get a better idea of REW and what my settings need to be.

UPDATE: ok, everything seams to be working as it should be. I was wrong about the other line in channels being broken or not working. I just forgot that I had to switch in put channel left or right.
The only problem now is still the SPL's signal that comes in too weak and the VU input level only indicates 39db while the SPL's needles points to 75db.

is there maybe a possibility that the SPL meter's build in amp sends out the signal too weak?

**brucek** · **08-27-07, 08:09 AM**

Quote:

is there maybe a possibility that the SPL meter's build in amp sends out the signal too weak?

No, it's a typical line level signal.

brucek

**subby** · **08-27-07, 09:32 AM**

So it defenetly should be my soundcard? because I already checked with another cable and it's the same result.

**subby** · **08-27-07, 12:57 PM**

Any suggestions?

**brucek** · **08-27-07, 01:43 PM**

I can only suggest getting a cheap soundcard. It isn't worth the effort messing around for the price of a soundcard ~$25

brucek

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