Please Tell me if I am on track

Hi I am trying to upload a jpeg but am having a bit bit of trouble. nothing happens when I click manage atachments button or the paperclip button. I would like you all to tell me what my readings are telling me. But i have to get the pic up first.

please help

Jim

Figured out the upload... one computer nothing, another works fine...odd

Please tell me why this post got moved to boonie ville...lol I would like to get some feed back on if my plots are close and what to do in REW. I thought that I had put this post in the correct thread... sorry if I did not. How should I word this to stay in the popular area where I might get some help?

jam

[Sonnie]

Hi Jim,

Clicking on either the Manage Attachment button or the gemclip button should bring up the Manage Attachment pop-up window as such...



I just uploaded this image and it worked fine.

If you are having a problem, it may be you have pop-ups blocked... otherwise, I'm not sure what it would be.

You can also use our Image Gallery

[Sonnie]

I had moved it to the help area... I moved it back for you.

thank you... now if I just just figure out what the graphs mean I will be on my way!

Is there somewhere that I am missing that shows examples of what a good measurement graph looks like.

The ones I made seem to indicate that I have some deep cuts/peaks. And when I listen to the sweep by doing a manual measurement I can easily hear where the sine wave tone gets louder and softer. This is in an untreated 19' by 14' room with 8 1/2' ceiling. The wall sheetrock (5/8) is hung on RC1 an the ceiling rock (5/8) is hung on RC2. I hope to put up traps/difusers/etc to help, but before that I need to understand what I am reading on the graphs

jam

[Sonnie]

I've been somewhat out of touch with REW graphs for a while, but it looks like you are measuring your mains only with no sub.

Check out this thread and this thread for proper graph posting.

Sonnie wrote:

I've been somewhat out of touch with REW graphs for a while, but it looks like you are measuring your mains only with no sub.

Check out this thread and this thread for proper graph posting.

Yes, the speakers are JBL jrk100s, 15" full range PA Speakers with horns, with no subs attached. I also have some near field M-Audio BX-5as that I have not used for measurments yet. My goal right now is to determine the room accoustics and try to calibrate REW. Am I going about this all wrong?

jam

[Sonnie]

Yeah... those PA speakers probably are not designed to deliver the lower octaves of bass. You got what you got... but, did you calibrate your sound card per the REW Online Help File?

If not, your sound card may be pulling some of that low end down on the measurements. Also, what SPL/Mic are you using and are you applying correction files?

As far as room acoustics are concerned... probably some pics of your room posted in the Home Audio Acoustics forum would be a good start. Our guys are really good with acoustic treatment recommendations.

Sonnie wrote:

Yeah... those PA speakers probably are not designed to deliver the lower octaves of bass. You got what you got... but, did you calibrate your sound card per the REW Online Help File?

If not, your sound card may be pulling some of that low end down on the measurements. Also, what SPL/Mic are you using and are you applying correction files?

As far as room acoustics are concerned... probably some pics of your room posted in the Home Audio Acoustics forum would be a good start. Our guys are really good with acoustic treatment recommendations.

I have the radioshack digital meter 33-2055 newer with the cal. And yes I just got my sound card calibrated (after the above pics). I have another thread running that helped me in that respect, they seem to be merging...lol. I will take some pics of the room and post then here... Is there a way to merge the two or should I just continue to answer both?

thanks...jam

[brucek]

My goal right now is to determine the room accoustics and try to calibrate REW. Am I going about this all wrong?

I a bit confused what your goal is...

Generally, REW is first used to test a subwoofer(s) alone, without mains attached. The range used is usually from 15Hz-200Hz. This is the area where equalization is most effective (after proper placement of the sub has provided the best overall response). Above 200Hz, up to around 500Hz, room treatments are quite effective. REW will begin showing a lot of comb filtering in the graphs at and above this range, so you need to apply the smoothing feature to see the overall trend of the response. This is what you're seeing in your graph above ~200Hz. You bottom end is trailing off as expected with the speakers you're using.

Is you intent to position the speakers for the best response, or are you trying to apply treatment?

brucek

Thanks brucek... That was very good insight I did not realize about the smoothing. I will do this once I know I am getting good readings. As for my goal... This room is not a HT but a recording/mixing studio. At the moment it is just one room but I am working on splitting the room into three; live/tracking, control, and vocal/isolation booth. For now though the recording equipment/mixing is being done in the one room that tracking is done. My near field monitors can be adjusted to the mixing seat but the PA speakers need to be in position for live work. The room is blank right now, nothin on the walls/ceiling except sheetrock. I was hoping that REW would help me find where to place bass traps etc. for mixing at the mix position.

hope I explained enough... if not let me know... jam

[brucek]

I was hoping that REW would help me find where to place bass traps etc. for mixing at the mix position.

It will work for sure.

Tip: Common swing for SPL graphs is 60dBSPL, so the standard we use here is a vertical axis of 45dB-105dB. This is a 60dB swing with 75dB being the center target...... Normally we would use a 15Hz-200Hz for subs, but since your area of interest is up to about 500Hz, that would be a good horizontal selection of 15Hz-500Hz for you..

If your soundcard cal routine went well (with a perfect flat response when measuring a loopback cable after calibration), and you have your SPL meter cal file loaded, and the Check Levels routine went well, and your Impulse Response doesn't show too much noise or harmonics, then the graph you showed is fine and displays a dip at 30Hz. Traps usually wouldn't go that low, so you'd need to move your speakers around somewhat to try and eliminate it.....

brucek

I see that 30hz dip as well but what about all the dips/peaks between 137 and 410? Is that normal? or too small/narrow to worry about? I was also thinking about adding a sub into the mix down system... (m-audio bx5as) plus sub. The readings above are from the jbls though. I would think that if there is a 30hz dip then the room is the cause. I will find out when I hook the sub in and test with the m-audio near-fields

thanks---jim

[brucek]

I would think that if there is a 30hz dip then the room is the cause

Well, the room is the cause of all the problems. A dip at 30Hz is modal problem and the dips at 137 & 410 would be otherwise, such as reflection etc.

I don't know anything about recording and mixing, but I would guess you would want the mixer to receive as a signal that was as free of peaks and dips as possible. Narrow dips aren't going to be noticed though. That's why the smoothing can help you a lot to smooth the narrow problems.

No question that the best friend of a mixing console must be the near-field nature of the speakers. That removes a lot of room effect. Then I guess you have to place panels to smooth out the rest. Placing your REW mic exactly where your head would be at the console is important.

Others who know more about recording can comment better....

brucek