# Please help!!!!!



## Guest (Sep 13, 2008)

Hello everyone,

I tried moving the bass traps around and monkeyed with placement of my desk, as well as changed up the amp to make sure that it wasn't coloring the signal, nothing changed in the lower frequencies. They were still 20 - 30 db lowder than the upper frequencies. 

So, I almost gave up until I decided to use a different microphone and here are the results.

Dynamic Omni-Directional (Blue line)
Dynamic Cardioid (Pink Line)
ECM800 (Green Line)

(I was going to post some links to pictures but the site won't let me.) 
I have a thread open on Ethan Winer's forum if you want to look at the pictures.

From what I can tell, the ECM is low frequency sensitive below 300 Hz and the Omni Directional is Hi Frequency sensitive about 300 Hz. 

What do you make of this? Is there something wrong with the mics?

Like I said, I re-arranged the room completely and I'm still getting louder low frequency readings using the ECM8000.

Now, I must mention that I'm using the ECM8000 with a regular mixer and not the recommended XENYX802 preamp. I had to buy a phantom power box to allow the mic to work. But non the less, both the phantom box and the microphone are from Behringer (PS400 Phantom box and the ECM8000 mic.

Any thoughts, anyone???????


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## thewire (Jun 28, 2007)

Do you have a spectral decay of before moving the traps still? The older links to those do not seem to work now.


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## brucek (Apr 11, 2006)

> Any thoughts, anyone???????


Were you using appropiate calibration files for the three microphones?

Did you insert the mic preamp in the soundcard loopback when you were creating the soundcard calibration file to account for its response?

BTW - we have a Post Padding thread where new members can go an fire off five quick posts so that they can then post graphs etc.

brucek


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## Guest (Sep 14, 2008)

Hi Thewire, I don't have those because I change went out and bought an ECM8000 so I didn't think that I needed them.

Sorry.


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## Guest (Sep 14, 2008)

Were you using appropiate calibration files for the three microphones? I got the cal file for the ECM8000 mic from this site. Not sure where to get cal files for the other mics?

Did you insert the mic preamp in the soundcard loopback when you were creating the soundcard calibration file to account for its response? No, I looped just the sound card and didn't include the outboard mixer. I'll try this tonight.

Thank you.


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## Guest (Sep 14, 2008)

Hi and thank you for your prompt responses.

I calibrated the sound card with the mixer in the loop. I've taken readings again and you can find the images in attached.

Please let me know what you think.

Thanks.


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## brucek (Apr 11, 2006)

> Please let me know what you think.


First you'll have to tell us what you're doing and what you're trying to accomplish.

Note, when you measure a subwoofer, use a measure range from 0-200Hz.
Use a vertical graph axis of 45dB to 105dB and a horizontal graph axis from 15Hz to 200Hz. Use the Graph Limits button to set this. Use a target level of 75dBSPL.
Always use stereo mode with the crossover engaged in your receiver with all soundfield and effects turned off.

Waterfall plots use the same graph limits and must be changed to LOG rather than LIN mode (using the Freq Axis button).

brucek


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## Guest (Sep 14, 2008)

Hi Brucek,

- I have a home studio/mixing room that I'm trying to control my bass and high frequencies. When I read the graphs, it looks like my lower frequencies are much louder than my upper frequencies and the crossover seems to be at 300 Hz. The difference between each side seems to be between 20 - 30 db. I don't know what is causing this decrease in levels between the upper and lower frequencies. I would think that I need to correct this in order to get accurate mixes.

 Dimensions of the room are 12' x 12.5'.
 I'm using a computer with an M-Audio sound card and Room EQ. 
 An ECM8000 Microphone with an outboard phantom power supply from Behringer.
 I have an outboard mixer.
 I'm using an flat amplifier without any controls and my speakers are JBL4410a's. 
 No subwoofer.
 I have a total of 20 bass traps in my studio made with Rockwool 5" and Corning 703 
4".
 I have 5" x 7' x 2' bass traps in the side corners. x 4
 I have 4" x 32" triangle bass traps in the top tri-corners. x 4
 I have 4" x 6' x 2' bass traps in the side corners where the wall meets the ceiling. x 4
 I have 4" x 4' x 2' bass traps on each side of me for early reflections. x 2
 I have 4" x 4' x 2' bass traps in front of me and two behind me. x 4
 I have 4" x 4' x 2' bass traps directly above my listening position. x 2
 My speakers are approximately 2" away from the front bass traps and 4' a part.
 My listening possition is approximately 38% from the front of the room. 5' from the front of the room and 7' from the back of the room. I also have 6' from each side of the room. My microphone position for testing is at the listening position, triangular to the speakers. 4 ' away from the center of the speakers.
 My ceiling is 8' tall.
 I have hardwood flooring with carpet covering most of it.

Use a vertical graph axis of 45dB to 105dB and a horizontal graph axis from 15Hz to 200Hz. Use the Graph Limits button to set this. Use a target level of 75dBSPL.
Always use stereo mode with the crossover engaged in your receiver with all soundfield and effects turned off.

Waterfall plots use the same graph limits and must be changed to LOG rather than LIN mode (using the Freq Axis button).

I'll take some readings and change the settings as you requested and post the pictures today.

Thank you.


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## Guest (Sep 14, 2008)

Here are the graphs as per your request. I didn't have to change any axis because they were already set int he Graphs Limit button to the settings that you mentioned.

Thanks.


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## brucek (Apr 11, 2006)

I see no difference in those plots. The axis are still incorrect. 

Look at your vertical axis - it is from 20dB to 140dB - change it to 45dB - 105dB. The horizontal should go (in your case) from 15Hz - 4KHz. 

Enter the values into the Graph Limits button popup and apply.

We don't require spectral or scope. just waterfall (log, not lin) and response with the correct axis.

brucek


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## Guest (Sep 14, 2008)

I hope these are better. I'm trying to understand what you want. 

Thanks.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Top one looks good. Change the axis of the waterfall to the same as the other - i.e. 45-105.

Regards,
Wayne


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## brucek (Apr 11, 2006)

> I hope these are better. I'm trying to understand what you want.


Getting better. 

Since you are testing a sub plus mains in pursuit of checking room treatments (I think), then set the Measure screen testing range that you'll sweep from 0Hz -~500Hz and set your graphs horizontal scale to 15Hz-500Hz (for a sub only it would be 15hz-200Hz). 

Also be sure you're testing at 75dBSPL target level.

And as Wayne said, set your waterfall to the same axis as the response graph. It also looks like you have a lot of ringing and as such I would change the time range in the waterfall screen from 300ms to 600ms.

Here's what they should look like.

View attachment 9322


View attachment 9323



brucek


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## Guest (Sep 14, 2008)

Thanks to both of you for your prompt responses.

I think I'm starting to get what you want. A little dense at times.

Just so that you know, I don't have a subwoofer. I only have 2 studio monitors JBL 4410a's.

THanks.


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## Wayne A. Pflughaupt (Apr 13, 2006)

You might want to check your SPL calibration. 104 dB - wow, are you trying to blow up those speakers? 

Regards,
Wayne


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## brucek (Apr 11, 2006)

> I think I'm starting to get what you want


You've changed the response chart to LIN from LOG. Click the Freq Axis button to display *LOG*.

See how the spacing on your response graph is equally spaced? It looks nice, but we don't hear that way. It has to be LOGarithmically spaced. Look again at my graph I posted above. Clicking the Freq Axis button switches between LOG and LIN. Use LOG.

Also you're still having trouble with your horizontal axis. It should be set to *15Hz to 500Hz*. You have your response graph set to 2Hz-500Hz and you have your waterfall from 20Hz-500Hz. Set them both to 15Hz - 500Hz and both of them LOG.

brucek


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## Guest (Sep 14, 2008)

That's weard. My SPC1000 meter says that it's reading between 73 and 76 db's. Perhaps it's my mic sensitivity or trim on the mixer that I might be running a bit hot. I'll try to adjust it and see if I can get the reading down. It's not very loud on my speakers at all.


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## brucek (Apr 11, 2006)

> Perhaps it's my mic sensitivity or trim on the mixer that I might be running a bit hot. I'll try to adjust it and see if I can get the reading down.


Hopefully you've loaded the correct calibration file for your microphone into REW?

Hot? No, you must have a mic mixer absolutely flat. Most people include the mixer in the loopback when they create their soundcard cal file.

Hopefully, you've calibrated your soundcard and created a soundcard file that is loaded into REW?

There's not much reason taking measurements unless you have flat calibrated all the equipment you're using, then when you take a measurement, the only variable is the speakers and the room.

brucek


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## Guest (Sep 14, 2008)

Here are my latest readings with the levels brought down. I'm going to try a different mixer that should be completely flat and re-calibrate my sound card with the mixer to see what I get.

The cal file that I'm using is as follows:

newecm.cal 09-09-2008 2:31 PM

Hope it's right.


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## brucek (Apr 11, 2006)

> The cal file that I'm using is as follows:
> 
> newecm.cal


But you can only use that cal file if you are using a Behringer ECM8000 microphone (and no other).

Again, please use a horizontal scale that is the same for both waterfall and response graphs of 15Hz-500Hz.

brucek


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## Guest (Sep 14, 2008)

The microphone that I'm using is a Behringer ECM8000.

I'll check out my other mixer, recalibrate and try it again.

Thanks.


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## Guest (Sep 14, 2008)

Okay, 

I changed the mixer to another one and I'm getting the same results even though I calibrated my mixer with the sound card M-Audio 2496. Both the spectrum and the waterfall look almost the same with little to no change as with the other mixer.

I've attached a copy of my mic and sound card calibration. The mic calibration is in black and the sound card is in yellow/orange.

Can you tell if I've successfully calibrated my card?

Thanks.


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## brucek (Apr 11, 2006)

> Can you tell if I've successfully calibrated my card?


Yep, it's good.

OK, I am definitely confused. You have a set of standard JBL studio monitors that have only a 10" woofer and a specification of 45Hz-20kHz (+/- 2dB). 

Yet you have response that starts to rise below about 300Hz and increases about +30dB as the frequency lowers to an extension beyond 20Hz. 

Something is not right. You're doing something wrong. Those speakers should be flat and start to drop off around 45-50Hz - not rise by 30dB starting at 300Hz. It's as if the drivers are bad in the speakers. Where is your microphone located when you measure?

Have you tried a single monitor in the middle of the room, away from reflecting surfaces, and taken a near-field measurement to remove the room effects..

brucek


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## Guest (Sep 15, 2008)

I agree about being confused...... the microphone is approximately 4 feet between the two monitors. In a triangular fashion. It's considered the listening position. The monitors are also 4 feet a part.

Perhaps I might have it hooked up wrong. 

What I did was put a Y connector from the sound card right out channel to my amplifier left and right in. So that I get sound from both speakers. Then I ran a single wire from my sound card left out to my sound card left in as a loop back (the manual says that it is not necessary but I did it anyway). Then I took an out source from the mixer into the right in on the sound card.

I'll try one speaker tomorrow in the middle of the room and take a reading. Maybe I'll test both to see if one is reading different from the other. (Play it safe)

How far should the microphone be from the speaker when taking te reading?

It's amazing how something so simple can become so complecated when I put my hands on it.

One thing that I may have forgotten to mention to you is the following:

I decided to use three different microphones and here are the results.

Dynamic Omni-Directional (Blue line)
Dynamic Cardioid (Pink Line)
ECM8000 (Green Line)

http://boxstr.com/files/3523124_zu6fl/measured.jpg

From what I can tell, the ECM is low frequency sensitive and the Omni Directional is Hi Frequency sensitive. 

What do you make of this? Is there something wrong with the mics? If I put two of the graphs together from the different mic's, I think it looks pretty good and even across with a dip at 120Hz. I'm just grasping here.

Also, I'm using a home system amplifier called B&K ST-202 in it's rawest form. There are no nobs to play with or turn on it at all, therefore I cannot turn up the bass or volume except from on my windows volume controller.
Do you think it's the AMP colouring the sound?

Thanks again to all that have helped. I'm really sorry if I'm causing a bunch of headaches and causing you to pull your hair out....


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## brucek (Apr 11, 2006)

> Then I ran a single wire from my sound card left out to my sound card left in as a loop back


Remove this cable. It will only cause noise.
There are two methods of compensating for soundcard response characteristics.
The first method (highly recommended) is to create a soundcard file that is loaded in REW to compensate for the soundcard. This file is created once (using a temporary loopback cable on the right channel which is later removed). The only cables when taking measurements are the right channel cables. The left channel is left open.
The second method is to use a permanent cable on the left channel and check the box in the settings screen called 'Use Left Channel as Calibration Reference'. No soundcard cal file is made or loaded. REW compensates for the soundcard by using the left channel loopback during each measurement. Extra noise is created using this process. 

Use the first method and remove the left channel cable. Also note that to check your soundcard calibration and to ensure that everything is working correctly, you can simply connect your loopback cable on the right channel (with the soundcard cal file loaded and the meter cal cleared) and do a measure. The response should be a perfectly flat line response since the soundcard cal file is applied inversely to the soundcards response characteristics. (Of course if you included a mixer in the soundcard file creation, you would need the mixer in the loop for the test. Be sure that test passes.



> How far should the microphone be from the speaker when taking te reading?


Well, depends on the speaker, but a couple feet to try and be equal distance from all drivers.



> From what I can tell, the ECM is low frequency sensitive and the Omni Directional is Hi Frequency sensitive


Well sure, and that's why we need to use a microphone calibration file in REW to render each microphone flat. Hopefully, you have the file loaded. That's what all this calibration stuff is about. We render the soundcard and mixer and microphone flat so the only thing we're measuring is the speaker and the room......

Although, I have to say after looking at the ECM8000 response compared to the other mics, that it doesn't look normal (where the other two responses look like typical mains). The calibration file really only compensates below 20hz and above about 10KHz - other than that, it's relatively flat. There is a rather elaborate circuit board of electronics in the ECM. I suppose you may have a fault. I suppose the only solution is to get hold of another ECM8000 (or get a calibration file for one of the other mics).

brucek


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## Guest (Sep 15, 2008)

Wow, you are an encyclopedia of information....... I really appreciate your patience with me.

Do you know where to find cal files for other microphones?

I'll try everything that you said and will report back to you tonight.

Talk to you soon and thank you.


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## brucek (Apr 11, 2006)

> Do you know where to find cal files for other microphones?


No, but they can be created rather easily from a graph of the microphones response - if you can find one. They aren't as accurate as sending a microphone away to have it calibrated, but perfectly acceptable for home use.

brucek


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## Guest (Sep 15, 2008)

Hi Brucek,

I found the specs for the two microphones. Are you able to assist me with creating a cal file for those mic's?

I've attached them to this message.

Thanks.


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## brucek (Apr 11, 2006)

The cal files are in simple text format and can be read and edited easily with windows notepad.

They are in the form of frequency as the first entry, followed by the decibel variation from zero representing the mic response..

The zero point is chosen arbitrarily as the flattest response area. REW will 'connect the dots' as it were between any frequencies. So I can use a resolute progression and then a jump to a higher frequency without a problem.

I created a mic cal file for you from the 635 PDF you attached, so that you can see how it's done (if you want to do your other mic). I chose between 400 and 900 Hz as my zero point. I also extended the graph endpoints a bit to include down to 20hz and up to 20KHz. This is a liberty that can be inaccurate, so you can remove the 20Hz, 30Hz and 20KHz entries in the file if you wish, but they should be close enough for home use and I would probably just leave them.

I attach the cal file and what it looks like in REW when loaded. You can compare it to the 635 pdf graph. Simply save the target cal file and dump it into notepad to have a look.

View attachment 9347


View attachment 9346


brucek


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## Guest (Sep 15, 2008)

Not sure what to say but thank you. I really appreciate your help on this. 

I'll definitely be working hard tonight to make this work.

Talk to you soon.


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## Guest (Sep 15, 2008)

Brucek,

Is there a way to test the frequency curve of the amplifier as well?

Thanks.


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## brucek (Apr 11, 2006)

> Is there a way to test the frequency curve of the amplifier as well


Not easily, but an amplifer will be flat over most of the audio bandwidth.... Not much chance of a problem there..

brucek


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## Guest (Sep 16, 2008)

Okay, here is what I did. I tested the speakers, created new cal files etc... etc... and got the same results. Didn't know what to do at that point and wanted to light everything up with a match. Thankfully I didn't and decided to replace some equipment that I had. I went out and bought a new XLR cable and a new xenyx802 preamp. 

Here are my latest readings. I would appreciate your opinion on the graphs from my home studio.

Thanks Brucek and Wayne.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Overall it's not that bad. If you're expecting it to look like those graphs manufacturers publish for their speakers - that ain't gonna happen. Try using 1/3-octave or even 1-octave smoothing on the graph and it will look more like what you're probably looking for.

Regards,
Wayne


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## Guest (Sep 16, 2008)

Thanks for the reply Wayne.

So there really isn't anything wrong with the graph? Are those dips at 120 Hz, 320 Hz and 1.75 Khz okay? Should I move my bass traps around to try and reduce those dips, or do you think that they are good enough for a recording studio mixing room?

Perhaps a repeated question. 

Thank you.


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## Wayne A. Pflughaupt (Apr 13, 2006)

I don't know of moving the bass traps around will help or not. Whoever manufactured them can tell you that better than I can. I don't think they work all the way up to 1 kHz anyway. The raggedness up there is simply comb filtering from reflections. 

Overall your room appears to be very well dampened. There is bare-minimal comb filtering up to the point where the graph ends. By comparision, take a look at this less dampened room. It's a full-range graph, but even ignoring everything above 2.5 kHz I'll think you'll realize how good yours is:


View attachment 9363​

I assume you know that the purpose of bass traps is to minimize low frequency ringing (i.e., extended decay of the low frequency signals). Your waterfall graph shows your lows are truncated pretty well. Changing the window to 300 ms would display that even better.










The raggedness in response is perfectly natural, it's just what rooms do to response. Overall I'd guess that your speakers sound pretty good. Above ~150 Hz you have fairly linear response with no apparent "problem trends" - at least not as far out as the graph ends. To see what I mean about "problem trends," take a look at this graph below yours, as a comparision:


















In this graph, we see a huge peak at 40 Hz. The area between 1-5 kHz is overall depressed compared what's below 1 kHz. And of course we have a nasty peak between 5-8 kHz that's going to exaggerate sibilances. Response falls like a brick above 8 kHz, which will certainly take some of the "sparkle" out of cymbals and other instruments with lots of high frequency energy.

Feel better now? 

Regards,
Wayne


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## brucek (Apr 11, 2006)

> I went out and bought a new XLR cable and a new xenyx802 preamp.


From looking at the mic cal in your above post, I'm assuming that you are using the ECM8000 mic (that was acting strange) and that the fault was either the XLR cable or the Preamp?

BTW, your response is quite good. The waterfall is very good and it appear your treatment has been quite effective. You could go to a 300ms second windows (as already noted) to get a better look, but either way it's very good.

Yeah, you could add 1/3 octave smoothing (since you're graphing beyond a subwoofer range) to get a better look at the underlying trend, but the comb filtering appears very well behaved.

brucek


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## Guest (Sep 16, 2008)

That is music to my ears. Thank you so much for all your help both to Brucek and Wayne. I can't believe the support you guy's provide for free.

You are correct, the difference was the cable and the xenyx802. I put everything back and changed only those two things and it worked.

This is definitely a great experience and I hope that everyone enjoys this as I did.

Again thank you and a Kudo's to the site admins, moderators, volunteers etc.....

Talk to you soon.


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