Penngray's HT room project

[penngray]

Im going to use this thread to get all my questions answered and to post updates of doing full room analysis of my new HT room.

The room is ready for acoustical treatment but I want to run initial charts just so I know what Im starting with. Its a 13x25 room but the sound is on the 25 foot wall, I have run my theater sideways actually for many different reasons, I know already its not optimal and I need to really absorb reflections on the "back" wall because I have one row and it is 2 feet of the back wall. I will post pics and graphs as I go along.

Anyways, here is the Equipment....

Nady CM-100 condensing mic, I assuming its identical to the Behringer brand so I will use the same cal. file
Xenyx 1002Fx pre-amp
HP Notebook with Vista
soundblaster live! 24bit external USB

Note: IF I can get his all done in 7 days I can return all the equipment

[penngray]

I have connected all equipment according to the pics and posts on here.

I have added the Behringer cal. file to calibrate the mic, should I have c Weighted SPL meter checked for this mic?

and now Im trying to calibrate REW but Im stuck. I have read many threads, help files and they all talk about changing the REW input volume.

Those options are greyed out. I can not change them...what can I do? I selected the proper soundblaster USB options in my My input and output device selections but what else?

[penngray]

Here is the Mic/meter tab...




here is the soundcard tab



So far Im stumped on how to calibrate...I have the left main speaker out connect to the left line in to do the loop testing (although I can not tell left and right when looking at the 1/8" plug y-splitter that splits into 2 RCA connections.

Here is what I get when I start measuring....



Here is what I get when I start the sound card calibration, I can not get even close to a 3 dB differential?????



Its all very confusing but it doesnt seem that Im doing this correctly. I do get a signal on the left channel, not shown in the last pic, its gets up too -14 which is green but the message still says my DB is too low...is it thinking I need the right channel?



Maybe its a Right and left thing ? I did switch input channel to Left and clicked "OFF" the use Left channel. I get a better headroom of 19dB but there is still a message talking about 10 dB.


I guess my questions are....

What did I do wrong?

[penngray]

EDITED:

There is a phones/control room nob that I had set to zero......hang on.....I see dB levels now....

btw, 75 dB is pretty low to hear...should it be?

Well, I still dont have a clue so I will wait for some help. Its hard to know if Im doing anything right, the numbers are all over the place it seems to me. Its kind of a shoot if you have never done this before.

Note: this isnt a very active site is it? I hang on AVSForum and there is a tons of activity, help, opinion. I will be patience

[JohnM]

The SB Live! 24-bit external seems very problematic under Vista, I don't think anyone has had good results with it. To check the volume settings, when you have REW running right click the volume control icon in the taskbar, select Open Volume Mixer and set the level for REW to the maximum. Close the volume mixer, right click the icon again and select recording devices. Double-click the Soundblaster Live Line In/Mic-In entry on the Recording tab that appears, select the Levels tab and put the Line In level to max. On the advanced tab set the sample rate and bit depth for shared mode to 2 channel, 16 bit, 48000 Hz (DVD Quality).

[brucek]

Uncheck the Use Left Channel Calibration reference, since you're not using it.

This is explained in the REW HELP FILES under Calibrating the soundcard and under Soundcard connections

You are using the soundcard cal file method of calibration, so you will use the looped cabled during calibration to create your soundcard file and then store it and load it into REW.

Then you'll remove the looped cable and your ready to go and hook up your cables.

With an ECM8000 type cal file, the C-Weight check box doesn't have any effect.

There are some reported problems with that soundcard and VISTA...

brucek

[penngray]

thanks, Im going to move the sound card to my desktop which is running XP. I will do a test there and see if I can get better results.

I seem to be getting the Mic calibrated but I can never get it to match my RS SPL....

Example, I set my receiver volume so that my RS SPL shows 75 dB then I press calibrate on the mic, it comes up with a value I should enter on the screen the default is 75 dB so I assume I just press enter to calibrate.

Then after that I look at the SPL meter and its reading about 10 to 15 dB higher then my RS meter still I guess this could be still a Vista issue so I will test with my XP box first.

[penngray]

This is explained in the REW HELP FILES under Calibrating the soundcard and under Soundcard connections

its explained but Its about as clear as mud to me....the first problem is that those 1/8" plugs with two RCA connections (Y plugs) dont tell me which is right or left so I have no idea how Im suspose to connect right out to left in for the looping. Im just not clueing in on how that is achieved.

[penngray]

Okay, I think Im getting somewhere on XP.

Current Mic and sound card calibrations.



To get no distortion I had to disconnect my RCA connection from my mic pre-amp...otherwise I was getting a huge distorted line for my soundcard calibration. I never read that in any the help docs I was just experimenting to try and get a decent plot. I might have missed that I had to disconnect it when doing my loop connection.

so Im going to assume Im calibrated and Im going to play around with it now.

[penngray]

Okay, so this is my first full 0 to 10K Hz measurement....




comments? This is a test in my office so I know its going to be a crazy bad plot. I just want to know that Im ready to move the equipment in the room.

Im not confident that its running full sweeps (mains and sub) I assume it is but those big distorted part on the right side seems like its screwed up and not set right, it simply looks like its all sub... how can I make sure it runs a full sweep with all main speakers together?

[brucek]

Use a vertical graph axis of 45dB-105dB and a horizontal graph axis starting at 15Hz for all graphs. This is set by clicking the Graph Limits icon on the REW screen.

When displaying graphs higher than 200Hz, you may turn on the smoothing feature (1/3 octave). This removes the normal comb filtering you're experiencing in your graph.

Your receiver must be in stereo mode so that only the mains and sub are on. These are the only channels you can test since REW is a mono signal.

Try the sub alone first (by disconnectingthe mains wires) and measure to 200Hz and use a graph horizontal axis of 15Hz-200Hz. Then when you get a smooth response by moving the sub around, add the mains and adjust the level (it's obviously low right now).

brucek

[salvasol]

penngray wrote:

....the first problem is that those 1/8" plugs with two RCA connections (Y plugs) dont tell me which is right or left so I have no idea how Im suspose to connect right out to left in for the looping. Im just not clueing in on how that is achieved.

Aha ... I'm not the only one who had this problem (I was trying to figure it out the same thing)

I checked my receiver AUX input, and the red side is what you need to use

[penngray]

add the mains and adjust the level (it's obviously low right now).

I can not figure out how to add the mains in REW...I only get the subs evertime I test. I change teh "Target Defaults, speaker" option to "full range" and then I run a measurement and only my subs have sound still.

[brucek]

I can not figure out how to add the mains in REW...I only get the subs evertime I test. I change teh "Target Defaults, speaker" option to "full range" and then I run a measurement and only my subs have sound still.

REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.

If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........

brucek

[penngray]

REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.

If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........

brucek

Hmmm...that is what I figured, I will double check the receiver.

[Jerm357]

brucek wrote:

REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.

If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........

brucek

The signal only comes out of one of the front main speakers and the sub right? Not both the mains at the same time?

[brucek]

The signal only comes out of one of the front main speakers and the sub right? Not both the mains at the same time?

It will come from both mains if a splitter is used at the receivers input to direct it to both right and left channel (as shown and explained in the Connections post).

I do try and get everyone to read this thread before they buy any equipment and attempt to hook up REW. It explains all the equipment required, where to get it, how much it costs, and how to hook it up. Combine that with the REW Help files and that's all anyone needs to be an expert.

brucek

[Jerm357]

Ok I see what you mean but if hooked up like this pic with out the optional loop back connections it should only come out of one right?

[brucek]

Yep, unless you had a mono button on your receiver............

brucek

[penngray]

I started my HT room measurements tonight (the room has no treatments yet) I had everything calibrated friday but now I get the below message...




"impulse peak not were it should be" ??? I double checked all calibrations and things seem to be fine so I dont know.

here is the filter adjusted plot....



Here is the measurement plot.....



and here is the waterfall plot.....



The real measurement plot looks better then the filterd plot, is this always true?

Also, I can not get the waterfall to show anything past 90 Hz....besides that the waterfall for the low end looks pretty good so far, doesnt it? Of course now Im nervous because if its good then I have to believe I did something wrong!

[JohnM]

To fix the problem with the waterfall display set the frequency axis to logarithmic by clicking the Freq Axis button in the toolbar when you are looking at the waterfall. Those are almost certainly not valid measurements, however. If you post screenshots of the Scope page and the Impulse page that may give some clues what is going wrong. You can save a jpeg of any graph by clicking the disc icon in the bottom left corner of the graph, at the ends of the scroll bars.

[penngray]

Ok, so Im trying to get my soundcard calibrated again!! Is it really this hard all the time, I mean it laid out step by step but it never works and that is really annoying!!!


Sound card calibration

1 kHz test tone...



That is good correct?

The loop back is connect Right RCA cable out connected back into the line in adapter, of course I dont know which is left or right on this adapter?? Does it matter?



Sooooo....all should be good to run the sweep? correct?



Nope, this time its a straight line. Man this stuff is really, really fussy and things dont work easily my fustration level is extremely high now. I have 20 years of software and hardward experience in the IT world and it shouldnt be this hard.

Been through the help too many times now so something is missing.

Please help, I need to get this stuff working because I have to get the room done this week

[brucek]

Is it really this hard all the time,

Nope, should be simple.

That is good correct?

Why do you have a signal at both right and left input showing in your picture?
You only loop the line-out right to the line-in right for soundcard calibration. Leave the left channel open.

of course I dont know which is left or right on this adapter?? Does it matter?

Sure it matters. You need to use right on the line-out adapter and right on the line-in adapter.
Use a multimeter to identify the left and right on both adapters and mark them if needed. The tip is left and the ring is right and the sleeve is ground. You can use right or left, just be sure to use the same on line-in and line-out.

brucek

[salvasol]

...Ok, so Im trying to get my soundcard calibrated again!! Is it really this hard all the time, I mean it laid out step by step but it never works and that is really annoying!!! ...

I think most of us struggled when doing this calibration ... you need to do it just one time.

... The loop back is connect Right RCA cable out connected back into the line in adapter, of course I dont know which is left or right on this adapter?? Does it matter? ...

Yes, I think it matters (that was the problem I have when calibrating my soundcard, I was using a 1/8" cable without the splitter)

What I noticed is that you have marked to use left input channel (it has to be right), also, the input/output device need to be your soundcard not default ... if the adapter doesn't have a mark to see which side is R or L, try one side and if doesn't work switch sides.

The soundcard calibration will look similar to this



Relax ... you'll make it work

[penngray]

Ok, started from scratch...


1. Rebooted notebook, my memory was all used up and REW was pretty slow so that might have cause problems.

2. rechecked all line levels on my sound card....made sure everything was muted except Volume/Wave...on problem here could have the fact that CD wasnt muted and probably was screwing things up...

3. started REW, selected mic calibration and added the correct file.

4. selected the sound card calibration and made sure I connected Right line out back into Right line in. This time I didnt get errors and I did get a plot similar to plots shown above and in the help files so I think Im getting further again.

5. Did a measurement from 10 Hz to 200 Hz and here is the plot, it definitely looks real this time!



One thing that still bothers me is that when running these test my subs are going to be so much louder then my main speakers so doesnt that skew the results for the 100 -200 Hz?