Old 09-24-2013, 01:38 PM   #1
Lucian
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Default Speaker and Room Analysis Help

Now that Reaper has a separate Monitor buss, I was thinking of creating an eq for my entry level (not great) monitors. I have 2 mics that are matched and comparable to AKG 414s. I was thinking of running some sine wavs out of my speakers with analysis, picking up the sound on the mics on a different channel and trying to match the analysis with eq to first get the speakers sounding how they should. I am on the right track? is this doable?

Then proceeding to room analysis.

I currently have Rockit 5's with a matching 10" sub.
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Old 09-24-2013, 03:32 PM   #2
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Sign yourself up on the Home Theatre Shack forums and download "Room Equalisation Wizard".

You really need an omnidirectional mic (the Behringer ECM8000 is good enough here). You really need an SPL meter, but the radio shack one is good enough for the job.

Read up on how to use it, try some sweeps, come back and chew the cud (PM me if I don't notice your replies).

It's a great tool for free and I've found out some strange things in the bottom end frequency of rooms with it.


Oh, and don't swear in their forums


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Old 09-24-2013, 07:40 PM   #3
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Thanks for the link, Planet. I don't have a measuring mic but the mic I mentioned can be set to omni mode. So I am using that with a DMP3 preamp for figuring this out.

I spent a few hours messing with this and have some problems calibrating the sound card. I downloaded the beta17 with asio drivers as well as the original but have the same problem. My soundcard is a Delta-66 with 4 mono ins and outs.

In REWv4 I can either choose 1&2 for outputs to my speakers or 3&4 to get the loopback on 3, not both

In REWv5 with Asio, I can choose out 1 or 2 so only one speaker works and then choose Out 3 for loopback reference.

The INS are ok. Loopback is on 1 and mic is on 2.

To calibrate the soundcard, do I need the mic on? Without the mic, the loopback occurs but it says the db is way too low, with the mic on, it says there is too much db variation for a valid calibration file but I am guessing this is due to the mic. Also, since I only get 2 outs for this, one is loopback and the other is only one monitor so when the sweep plays it is only out the left speaker.

Any ideas?

While I sort this out, I will pick up a calibration mic.
Edit: So I need both a calibration mic AND and an spl meter?
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Old 09-25-2013, 05:17 AM   #4
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Quote:
Originally Posted by Lucian View Post
Thanks for the link, Planet. I don't have a measuring mic but the mic I mentioned can be set to omni mode. So I am using that with a DMP3 preamp for figuring this out.

I spent a few hours messing with this and have some problems calibrating the sound card. I downloaded the beta17 with asio drivers as well as the original but have the same problem. My soundcard is a Delta-66 with 4 mono ins and outs.

In REWv4 I can either choose 1&2 for outputs to my speakers or 3&4 to get the loopback on 3, not both

In REWv5 with Asio, I can choose out 1 or 2 so only one speaker works and then choose Out 3 for loopback reference.

The INS are ok. Loopback is on 1 and mic is on 2.

To calibrate the soundcard, do I need the mic on? Without the mic, the loopback occurs but it says the db is way too low, with the mic on, it says there is too much db variation for a valid calibration file but I am guessing this is due to the mic. Also, since I only get 2 outs for this, one is loopback and the other is only one monitor so when the sweep plays it is only out the left speaker.

Any ideas?

While I sort this out, I will pick up a calibration mic.
Edit: So I need both a calibration mic AND and an spl meter?

Don't think you need the mic for the audio interface loopback test -that's just to make sure you're flat from in to out (or out to in, here). Older interfaces could drop-off or be uneven. Should be only a once performed test so that in/out gremlins are eliminated. If you're having issues measuring this it's probably down to gain-staging/levels.

The SPL meter is so you can calibrate the levels to SPL in REW, and also a real-world step that keeps you in a realistic zone where you're not endangering your ears, your monitors and your neighbour relations (also to get you above an expected noise-floor).

The Realist SPL meter is quite cheap and so is that Behringer mic. It'll cost you more if you want to calibrate it to get a correction curve. You are most interested in the sub-400Hz domain, so it's not that critical. Any good omni will probably do, they're not as peaky as cardoids as a rule.

Top-end unneveness is phase-variable to the mm, so mic measurements are too small a sample to be necessarily useful (where it's room-created issues and not monitor chain, obviously), and top-end is so easily corrected with absorption and diffusion anyway. It's the bottom-end that takes you by surprise with standing-waves and rear-wall reflections, and it is this end of the audio frequency spectrum that is the hardest to tame and correct for, especially in smaller rooms.


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Old 09-25-2013, 03:54 PM   #5
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Lucian, have you acoustically treated your room (bass traps, reflection panels)?
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Old 09-25-2013, 06:04 PM   #6
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Hi Tim, no, I haven't. I wanted to test this software that helps correct bad rooms, I am just curious about the results. The problem is I cannot seem to get the delta 66 card calibrated. This is the second night attempt but I am getting nowhere, It keeps saying the signal is -65 db and too low.

One last stab at this. It only works when the mic is plugged in. There are three meters:
Out - not sure if this is Out to the left speaker on delta OUT1 or is it the Timing reference output(loopback cable) on delta OUT2.

In - delta IN1 -the mic.

Ref in - delta IN2 cabled to delta out2

Without the mic on, I get no signal on the middle meter which I would expect. But if I am not to use it then why is it there? Is it just for the level check?

Using the mic doesn't list that error anymore, it now says things are too loud or the 65DB range in volume is too much...still playing with this. The best I can get is 45DB variation in db during the sine sweep which it says is extremely suspicious and says shouldn't be used but it let me use it regardless to create a calibration file. I am wondering if my Room/setup is just that bad.
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Old 10-01-2013, 12:59 PM   #7
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Hello Lucian, I missed this.

You only need not user the mic for the soundcard loop-back test.

After that, you need the mic to read back what your monitors are chucking out.

Did you get a Radio Shack SPL meter?


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Old 10-01-2013, 02:02 PM   #8
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Hi Planet,
No, I am using a $500 condenser mic set in Omni pattern.
More info is I have a sub and I see there are settings for whether to
use it OR the monitors. The way I am wired is into the sub first and then out to the monitors. I suppose I could disconnect then monitors and then choose sub only but this is the least of my troubles I think.

I was going to post some pics about what I am seeing, my cable setup, etc but my audio computer is XP and I have grown spoiled with the snipping tool.
I will just use print screen and paint to crop old school style and hopefully something will jump out with seeing the pics.
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Old 10-01-2013, 02:12 PM   #9
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Quote:
Originally Posted by Lucian View Post
Hi Planet,
No, I am using a $500 condenser mic set in Omni pattern.
You are actually probably better off with a less expensive mic designed for the purpose just as an FYI assuming you don't have a calibration profile for the mic you are using.
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Old 10-01-2013, 04:43 PM   #10
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Hmmm...ok then, A radio shack spl meter it is. I will pick one up and post back here during the weekend.
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Old 10-01-2013, 04:46 PM   #11
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Hmmm...ok then, A radio shack spl meter it is. I will pick one up and post back here during the weekend.
Oh, sorry, I meant the actual mic that does that's used for generating the waterfall plot etc. However, I can't say enough good things about having an OK SPL meter as well because it'll always find good use.
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Old 10-02-2013, 03:50 PM   #12
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Quote:
Originally Posted by karbomusic View Post
Oh, sorry, I meant the actual mic that does that's used for generating the waterfall plot etc. However, I can't say enough good things about having an OK SPL meter as well because it'll always find good use.

Lucian may be ok with his omni for measurement (omnis tend to be flatter than other polar patterns), but I think it's quite hard to do the setup and monitor level calibration without an SPL meter.


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Old 10-02-2013, 04:40 PM   #13
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Hi Tim, no, I haven't. I wanted to test this software that helps correct bad rooms, I am just curious about the results.
Hey Lucian, I hate to be negative but I believe that EQ doesn't correct room acoustics issues. IME only actual physical room acoustic treatment does. Mainly because it's not just a frequency/dB level issue but a time-oriented-resonance issue... ringing. Owens Corning 703 panels (rockwool also) are inexpensive, and they work!
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Old 10-02-2013, 05:00 PM   #14
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Lucian may be ok with his omni for measurement (omnis tend to be flatter than other polar patterns), but I think it's quite hard to do the setup and monitor level calibration without an SPL meter.
Agreed, it's just that it made me a little uncomfortable not knowing the curve of the mic being used. So long as the low end of the range is mostly flat I assume it would be OK.
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Old 10-02-2013, 05:29 PM   #15
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well, I have an spl app on my phone which is always great showing to people who like standing in front of the mains

I would think my mic would work but the trouble is a calibration file does not exist.Is this is why I should get the behringer? as I need a calibration file for this to work?

mics aside, I write device drivers for work so I am not completely clueless on what is going on, I just don't understand why I can't get the latency test to work with the loop back cable. My only guess is because I am not using a preamp? I am connecting the out directly to an in. Normally I use a DMP-3 pre amp. However, without it the meters are fine in the actual application running the test.

Tim: This won't be a final fix, just an experiment. I understand notching out 200hz because that is a problem freq for my listening space really winds up adding a new problem, but I am curious about the results and figured this would be fun and easy hehe
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Old 10-02-2013, 05:38 PM   #16
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Quote:
I would think my mic would work but the trouble is a calibration file does not exist.Is this is why I should get the behringer?
That does remove some guessing. I didn't read every thread but why do you need a latency test for room measurement? IIRC the only thing you need is to know the signal is within an acceptable SPL range for taking the measurement, that's about it.

The latency test will come in handy later for multi-tracking but I can't remember why it matters for measuring room response. Forgive me if I forgot as its been a little over a year since I did what you are doing when I measured and treated my room.

Oh yea, I remember... It wasn't for latency, it was for generating a calibration file for the sound card itself. However, as you'll see when you get it working the flatness of the sound card is likely going to far more flat than both the mic used and the room. If you have to account for the preamp too that may be worth completing and hopefully I'm not confusing things for you.
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Old 10-09-2013, 09:02 AM   #17
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Default Ethan Winer:the audio expert

I hope it is ok to add this to the discussion. Ethan Winer helped me alot a while back with frequency isolation and room measurements. You may find him at music player forums discussing audio science and acoustics.
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Old 10-10-2013, 05:26 AM   #18
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I hope it is ok to add this to the discussion. Ethan Winer helped me alot a while back with frequency isolation and room measurements. You may find him at music player forums discussing audio science and acoustics.

He does have a few odd ideas, but generally he's a switched-on guy with good info and advice for acoustic treatment of rooms. Pay close attention to his studies of rear-wall reflections causing nodes too.

EQ attenuation can be used to counter constructive resonance and reflective nodes, if you monitor rigidly from that one measured position (and three dimensions may be relevant here depending on the room mode causing the node), but is useless to alleviate the 20, 30dB nulls caused by destructive interference. These are the monitoring anomalies that will have you adding or leaving in frequencies that will jump out at you in other environments that do not share the same acountic topographies.

Think of EQ as a bodge fix, a temporary partial solution, even a fine varnish applied after acoustic treatment to smooth the last humps out; it is definitely treating the results, not curing the cause of the response deviations though. It is always much better to tackle the nodes at their source -the reflective boundaries of your room.

Stop, or at least control those reflections and what you hear will become close to what your monitors are putting out.



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