Home Theater Forum and Systems banner

41 - 60 of 73 Posts
E

·
Guest
Joined
·
0 Posts
Discussion Starter #41
Thanks brucek. I'm a little closer now, not sure what I was doing wrong before. However, when running Check Levels, nothing I seem to can get the Output and Right Input meters to balance. The output meter is always louder than the input meter by something like 12db.

Also, can you confirm for me that "soundcard line-out right channel" is the same as the right Front speaker connector?

Thanks for any advice!
 

·
Registered
Joined
·
2,431 Posts
So this is a Rythmik sub? Which one 12" or 15"?

I've seen artifacts like that below 15hz before but not that dramatic:scratchhead:. Looks almost like a cal file got added or something.You will get different results depending on your sweep range and duration. From what I have seen the longer the sweep stays in that range the more accurate it will be. A 1M 0-200hz sweep is going to be better than a 128k 0-24000hz sweep for the bass range. The very short sweeps seem to exaggerate the bass below 15hz a little. THIS IS OPPOSITE OF WHAT YOU ARE SEEING THOUGH! You usually have a LOT of compensation added to the readings in that range, which can do some screwey things from multiple cal files. I've never seen it affect things all the way up above 23hz though and with that big of a difference. Usually it's just a few db.

How hard is your sub being driven on these sweeps? Looks almost like a limiter is kicking in or something. The Rythmiks are small sealed subs and they are servo controlled and eq'd flat down to the really deep bass. That would cause the driver to be pushed very hard below 20hz even with a moderate volume sweep. What length were those sweeps? Can you keep the sweep range the same like 0-200hz and run one at each length and see if there is a difference there between the shorter and longer ones?
 

·
Registered
Joined
·
7,514 Posts
can you confirm for me that "soundcard line-out right channel" is the same as the right Front speaker connector?
Yep, usually.

However, when running Check Levels, nothing I seem to can get the Output and Right Input meters to balance. The output meter is always louder than the input meter by something like 12db.
I'm a bit confused by that statement. It makes no sense to me. You use the receivers volume control to set whatever level you desire on the soundcards input meter.

First connect a single loopback from line-out (right) to line-in (right) and do a Check Levels and Calibrate @75 and a Measure to be sure you get a flat line.

Now all your levels are setup in the soundcard. Then insert the receiver into that loopback and fuss with the receivers volume control when you run the Check levels routine. Don't touch the soundcards input or output levels, because you already have them in a good spot as if you were measuring a cable, but instead you've placed a receiver in the loop.

Get it?

brucek
 
E

·
Guest
Joined
·
0 Posts
Discussion Starter #44
First connect a single loopback from line-out (right) to line-in (right) and do a Check Levels and Calibrate @75 and a Measure to be sure you get a flat line.
brucek, I'm sorry, but I'm confused. When I connect line-out to line-in, I don't actually get any sound from my sub or speakers. So, what/where am I looking to get a 75db reading?

Thanks!
 

·
Registered
Joined
·
7,514 Posts
When I connect line-out to line-in, I don't actually get any sound from my sub or speakers. So, what/where am I looking to get a 75db reading?
After you run the Check Levels routine, you run the Calibrate routine. You don't hear any sound (of course), but you set the level to 75dB with the thumbwheel in the Calibrate routine to fool REW's SPL meter into thinking the level is 75dB. How else would REW know where to place the trace on the graph. You have to tell it that the level of the loopback signal is 75dB, so that's where the trace will lie. The advantage of doing the loopback first before you insert the receiver in the loop is to first verify that a cable without the receiver is indeed flat, and to get a good setup of the soundcards line-in and line-out before the receiver is inserted in the loop.

Then you remove the loopback and connect the receiver and go through the Check Levels routine using the receivers volume control to get the correct input level.

brucek
 
E

·
Guest
Joined
·
0 Posts
Discussion Starter #46
Thanks brucek! This is hopefully a correct attempt at measuring my pre-pro's response...

  • I set Windows Volume to 100.
  • I connected soundcard line-out (front right speaker) to soundcard line-in right channel.
  • I cleared meter cal file and kept soundcard cal file loaded.
  • I ran check levels.
  • I adjusted the sweep level to -20 which is where the out and right meters werer equal
  • I ran "Calibrate" using REW subwoofer cal signal as signal source
  • I set to 75 and clicked finished
  • I took a measurement using 0 to 15,000Hz, -20 level, 256k length, 1 sweep.
.
The result is shown in the first graph below (green line). Does it look as it's supposed to?

  • Next, I connected soundcard line-out right channel to pre-pro aux-in right channel, and pre-pro sub-out to soundcard line-in right channel and ran Check Levels.
  • I kept all settings the same as described above and only adjusted my pre-pro volume until out and right were equal (at around -20). I had to crank the volume on my pre-pro up to about 95%. Is this common?
  • I ran a measurement using the same settings as above. The results are shown in the second graph (red line).
Do these both look as they should?

Thanks!
 

Attachments

·
Registered
Joined
·
486 Posts
Looks correct to me. brucek will have to verify. It looks to be doing just like John stated:

For a 60Hz crossover the sub's output is down 6dB at 60Hz and down 25dB at 120Hz.
 

·
Registered
Joined
·
7,514 Posts
Do these both look as they should?
Yep, they look correct.

I would display the measurement graph with an upper limit of 200Hz to get a better look, and I might add the 60Hz REW target line to give yourself assurance that it's tracking close to spec, but it looks fine. There's nothing wrong with your receiver....

brucek
 

·
Registered
Joined
·
486 Posts
Would you say brucek that this pointing to the sub as the problem with his graph variances?
 
E

·
Guest
Joined
·
0 Posts
Discussion Starter #50
Here's a closeup. Any idea what that weird "blip" is about at 120Hz? Also, is it normal that I needed to crank my pre-pro's volume up to 95% to get the output and input levels even?

I'll work on some of the measurements suggested above by Ricci next.

Thanks again for all the help!!
 

Attachments

·
Registered
Joined
·
7,514 Posts
Any idea what that weird "blip" is about at 120Hz?
It would not be the receiver. It would be your computer and REW causing a small hitch in the signal sweep at that point.

is it normal that I needed to crank my pre-pro's volume up to 95% to get the output and input levels even?
I would set the REW sweep level up to a higher level (~-6dB) to offer the receiver more voltage, so you won't have to turn its volume up so high during the test.

BTW, turn on the REW target @60Hz to observe how the receiver tracks. Match it's passband level to the target for a good comparison.

Would you say brucek that this pointing to the sub as the problem with his graph variances?
The sub or the room. It's almost never the receiver...

brucek
 

·
Registered
Joined
·
486 Posts
The sub or the room. It's almost never the receiver...
So now he should do a nearfield plot of the sub using the same testing he did post #34 correct? Basically place the mic a few inches from the driver and do the same sweeps in post #34 to see if it is the sub. This should help remove the room correct?
 

·
Registered
Joined
·
7,514 Posts
So now he should do a nearfield plot of the sub using the same testing he did post #34 correct?
Yeah, that's correct, although doing it outside would be even better. I take it this is a servo type sub - so he wouldn't need to check a port nearfield.

brucek
 

·
Registered
Joined
·
486 Posts
Yeah, that's correct, although doing it outside would be even better. I take it this is a servo type sub - so he wouldn't need to check a port nearfield.

brucek
Yes it is a servo sub.
 

·
Registered
Joined
·
7,514 Posts
it is a servo sub.
I wonder if the servo mechanism is acting up. Certainly, he shouldn't be experiencing the high distortion that is revealed in his ETC plots shown in earlier posts.

brucek
 

·
Registered
Joined
·
2,431 Posts
Yep. My guess is that it's the servo or some form of limiting going on in the response below 25hz.

Elee532,

Try a moderate volume 0-200hz sweep set at 128K and then follow up with a sweep at each setting up to 1M, keeping everything else the same when you get a chance. My guess is that the longer sweeps will show a decrease in the lowest bass. After that start at a very low volume and do a few sweeps while increasing the volume 3db at a time and keep the sweep used exactly the same in between. (just turn your reciever up, be careful so you don't overdrive your sub) This should reveal whether it is some form of limiter in the sub or a problem with it.
 
E

·
Guest
Joined
·
0 Posts
Discussion Starter #57
The first graph shows four tests. Each was run using a 0 to 200Hz sweep. I used the "seperate traces" option to make for easier reading.

Green=128k
Red = 256k
Gold=512k
Aqua=1m

Graph two shows 0 to 200Hz sweeps set at 128k length with my pre-pro set increasing volume levels. The pattern doesn't seem to change much despite the change in volume.

What can you make of this?

Thanks!
 

Attachments

·
Registered
Joined
·
486 Posts
Have you tried doing any nearfield plots of the driver also?
 

·
Registered
Joined
·
2,431 Posts
Good suggestion Weverb.

Elee532,

Seeing as the 3 longer sweeps all correlate really well and have the lower bass represented well, I'd hazrd to say that you should probably stick with the 512K sweep length from now on. I think that your sub is fine.
 
41 - 60 of 73 Posts
Top